@ohos.buffer (Buffer)

A Buffer object represents a byte sequence of a fixed length. It is used to store binary data.

Recommended use case: Use Buffer when you need to process images and a large amount of binary data, and receive or upload files.

NOTE

The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version.

Modules to Import

import { buffer } from '@kit.ArkTS';

BufferEncoding

type BufferEncoding = 'ascii' | 'utf8' | 'utf-8' | 'utf16le' | 'ucs2' | 'ucs-2' | 'base64' | 'base64url' | 'latin1' | 'binary' | 'hex'

Enumerates the supported encoding formats.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Type	Description
'ascii'	ASCII format.
'utf8'	UTF-8 format.
'utf-8'	UTF-8 format.
'utf16le'	UTF-16LE format.
'ucs2'	Alias of UTF-16LE.
'ucs-2'	Alias of UTF-16LE.
'base64'	Base64 format.
'base64url'	Base64URL format.
'latin1'	Alias of iso-8859-1, which is backward compatible with the ASCII format.
'binary'	Binary format.
'hex'	Hexadecimal format.

buffer.alloc

alloc(size: number, fill?: string | Buffer | number, encoding?: BufferEncoding): Buffer

Creates and initializes a Buffer object of the specified length.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
size	number	Yes	Size of the Buffer object to create, in bytes.
fill	string | Buffer | number	No	Value to be filled in the buffer. The default value is 0.
encoding	BufferEncoding	No	Encoding format (valid only when fill is a string). The default value is 'utf8'.

Return value

Type	Description
Buffer	Buffer object created.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.

Example

import { buffer, JSON } from '@kit.ArkTS';

let buf1 = buffer.alloc(5);
console.info(JSON.stringify(buf1)); // {"type":"Buffer","data":[0,0,0,0,0]}

let buf2 = buffer.alloc(5, 'a');
console.info(JSON.stringify(buf2)); // {"type":"Buffer","data":[97,97,97,97,97]}

let buf3 = buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');
console.info(JSON.stringify(buf3)); // {"type":"Buffer","data":[104,101,108,108,111,32,119,111,114,108,100]}

buffer.allocUninitializedFromPool

allocUninitializedFromPool(size: number): Buffer

Creates a Buffer object of the specified size from the buffer pool, without initializing it.

You need to use fill() to initialize the Buffer object created.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
size	number	Yes	Size of the Buffer object to create, in bytes.

Return value

Type	Description
Buffer	Uninitialized Buffer object.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.

Example

import { buffer, JSON } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(10);
buf.fill(0);
console.info(JSON.stringify(buf)); // {"type":"Buffer","data":[0,0,0,0,0,0,0,0,0,0]}

buffer.allocUninitialized

allocUninitialized(size: number): Buffer

Creates a Buffer object of the specified size, without initializing it. This API does not allocate memory from the buffer pool.

You need to use fill() to initialize the Buffer object created.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
size	number	Yes	Size of the Buffer object to create, in bytes.

Return value

Type	Description
Buffer	Uninitialized Buffer object.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.

Example

import { buffer, JSON } from '@kit.ArkTS';

let buf = buffer.allocUninitialized(10);
buf.fill(0);
console.info(JSON.stringify(buf)); // {"type":"Buffer","data":[0,0,0,0,0,0,0,0,0,0]}

buffer.byteLength

byteLength(string: string | Buffer | TypedArray | DataView | ArrayBuffer | SharedArrayBuffer, encoding?: BufferEncoding): number

Obtains the number of bytes of a string based on the encoding format.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
string	string | Buffer | TypedArray | DataView | ArrayBuffer | SharedArrayBuffer	Yes	Target string.
encoding	BufferEncoding	No	Encoding format. The default value is 'utf8'.

Return value

Type	Description
number	Number of bytes of the string.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

let str = '\u00bd + \u00bc = \u00be';
console.info(`${str}: ${str.length} characters, ${buffer.byteLength(str, 'utf-8')} bytes`);
// Output: ½ + ¼ = ¾: 9 characters, 12 bytes

buffer.compare

compare(buf1: Buffer | Uint8Array, buf2: Buffer | Uint8Array): -1 | 0 | 1

Compares two Buffer objects. This API is used for sorting Buffer objects.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
buf1	Buffer | Uint8Array	Yes	Buffer object to compare.
buf2	Buffer | Uint8Array	Yes	Buffer object to compare.

Return value

Type	Description
-1 | 0 | 1	Returns 0 if buf1 is the same as buf2. Returns 1 if buf1 comes after buf2 when sorted. Returns -1 if buf1 comes before buf2 when sorted.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.from('1234');
let buf2 = buffer.from('0123');
let res = buffer.compare(buf1, buf2);

console.info(Number(res).toString());
// Output: 1

buffer.concat

concat(list: Buffer[] | Uint8Array[], totalLength?: number): Buffer

Concatenates an array of Buffer objects of the specified length into a new object.

System capability: SystemCapability.Utils.Lang

Atomic service API: This API can be used in atomic services since API version 11.

Parameters

Name	Type	Mandatory	Description
list	Buffer[] | Uint8Array[]	Yes	Array of objects to concatenate.
totalLength	number	No	Total length of bytes to be copied. The default value is 0.

Return value

Type	Description
Buffer	Buffer object created.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "length" is out of range. It must be >= 0 and <= uint32 max. Received value is: [length]

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.from("1234");
let buf2 = buffer.from("abcd");
let buf = buffer.concat([buf1, buf2]);
console.info(buf.toString('hex'));
// Output: 3132333461626364

buffer.from

from(array: number[]): Buffer

Creates a Buffer object with the specified array.

System capability: SystemCapability.Utils.Lang

Atomic service API: This API can be used in atomic services since API version 11.

Parameters

Name	Type	Mandatory	Description
array	number[]	Yes	Array to create a Buffer object.

Return value

Type	Description
Buffer	Buffer object created.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);
console.info(buf.toString('hex'));
// Output: 627566666572

buffer.from

from(arrayBuffer: ArrayBuffer | SharedArrayBuffer, byteOffset?: number, length?: number): Buffer

Creates a Buffer object of the specified length that shares memory with ArrayBuffer.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
arrayBuffer	ArrayBuffer | SharedArrayBuffer	Yes	Instance object.
byteOffset	number	No	Byte offset. The default value is 0.
length	number	No	Length of the Buffer object to create, in bytes. The default value is arrayBuffer.byteLength minus byteOffset. If null is passed, the byte length is 0.

Return value

Type	Description
Buffer	Buffer object created.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[byteOffset/length]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [byteOffset/length]

Example

import { buffer, JSON } from '@kit.ArkTS';

let ab = new ArrayBuffer(10);
let buf = buffer.from(ab, 0, 2);
console.info(JSON.stringify(buf)); // {"type":"Buffer","data":[0,0]}

buffer.from

from(buffer: Buffer | Uint8Array): Buffer

Copies the data of a passed Buffer object to create a new Buffer object and returns the new one.

Creates a Buffer object based on the memory of a passed Uint8Array object and returns the new object, maintaining the memory association of the data.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
buffer	Buffer | Uint8Array	Yes	Target object.

Return value

Type	Description
Buffer	Buffer object created.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

// Create a Buffer object of the Buffer type.
let buf1 = buffer.from('buffer');
let buf2 = buffer.from(buf1);

// Create a Buffer object of the Uint8Array type to ensure memory sharing between objects.
let uint8Array = new Uint8Array(10);
let buf3 = buffer.from(uint8Array);
buf3.fill(1);
console.info("uint8Array:", uint8Array);
// Output: 1,1,1,1,1,1,1,1,1,1

buffer.from

from(object: Object, offsetOrEncoding: number | string, length: number): Buffer

Creates a Buffer object based on the specified object.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
object	Object	Yes	Object that supports Symbol.toPrimitive or valueOf().
offsetOrEncoding	number | string	Yes	Byte offset or encoding format.
length	number	Yes	Length of the Buffer object to create, in bytes. This parameter is valid only when the return value of valueOf() of object is ArrayBuffer. Value range: 0 <= length <= ArrayBuffer.byteLength. Error 10200001 is reported if a value outside this range is reported. In other cases, you can set this parameter to any value of the number type. This parameter does not affect the result.

Return value

Type	Description
Buffer	Buffer object created.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer, JSON } from '@kit.ArkTS';

let buf = buffer.from(new String('this is a test'), 'utf8', 14);
console.info(JSON.stringify(buf)); // {"type":"Buffer","data":[116,104,105,115,32,105,115,32,97,32,116,101,115,116]}

buffer.from

from(string: String, encoding?: BufferEncoding): Buffer

Creates a Buffer object based on a string in the given encoding format.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
string	String	Yes	String.
encoding	BufferEncoding	No	Encoding format. The default value is 'utf8'.

Return value

Type	Description
Buffer	Buffer object created.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.from('this is a test');
let buf2 = buffer.from('7468697320697320612074c3a97374', 'hex');

console.info(buf1.toString());
// Output: this is a test
console.info(buf2.toString());
// Output: this is a tést

buffer.isBuffer

isBuffer(obj: Object): boolean

Checks whether the specified object is a Buffer object.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
obj	Object	Yes	Object to check.

Return value

Type	Description
boolean	Check result. The value true is returned if the object is a Buffer object; otherwise, false is returned.

Example

import { buffer } from '@kit.ArkTS';

let result = buffer.isBuffer(buffer.alloc(10)); // 10: buffer size
console.info("result = " + result);
// Output: result = true
let result1 = buffer.isBuffer(buffer.from('foo'));
console.info("result1 = " + result1);
// Output: result1 = true
let result2 = buffer.isBuffer('a string');
console.info("result2 = " + result2);
// Output: result2 = false
let result3 = buffer.isBuffer([]);
console.info("result3 = " + result3);
// Output: result3 = false
let result4 = buffer.isBuffer(new Uint8Array(1024));
console.info("result4 = " + result4);
// Output: result4 = false

buffer.isEncoding

isEncoding(encoding: string): boolean

Checks whether the encoding format is supported.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
encoding	string	Yes	Encoding format.

Return value

Type	Description
boolean	Check result. The value true is returned if the encoding format is supported; otherwise, false is returned.

Example

import { buffer } from '@kit.ArkTS';

console.info(buffer.isEncoding('utf-8').toString());
// Output: true
console.info(buffer.isEncoding('hex').toString());
// Output: true
console.info(buffer.isEncoding('utf/8').toString());
// Output: false
console.info(buffer.isEncoding('').toString());
// Output: false

buffer.transcode

transcode(source: Buffer | Uint8Array, fromEnc: string, toEnc: string): Buffer

Transcodes a Buffer or Uint8Array object from one encoding format to another.

System capability: SystemCapability.Utils.Lang

Atomic service API: This API can be used in atomic services since API version 11.

Parameters

Name	Type	Mandatory	Description
source	Buffer | Uint8Array	Yes	Instance object.
fromEnc	string	Yes	Current encoding format. For details about the supported formats, see BufferEncoding.
toEnc	string	Yes	Target encoding format. For details about the supported formats, see BufferEncoding.

Return value

Type	Description
Buffer	New Buffer object in the target encoding format.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

let newBuf = buffer.transcode(buffer.from('€'), 'utf-8', 'ascii');
console.info("newBuf = " + newBuf.toString('ascii'));
// Output: newBuf = ,

Buffer

Properties

System capability: SystemCapability.Utils.Lang

Atomic service API: This API can be used in atomic services since API version 11.

Name	Type	Read-Only	Optional	Description
length	number	Yes	No	Length of the Buffer object, in bytes.
buffer	ArrayBuffer	Yes	No	ArrayBuffer object.
byteOffset	number	Yes	No	Offset of the Buffer object in the memory pool. - When a Buffer is created using a memory pool (for example, using allocUninitializedFromPool to create a Buffer or using buffer.from() to pass a string whose length plus the offset of the current memory pool is less than 4 KB), the offset relative to the memory pool is returned. - When a Buffer allocates memory directly (for example, using alloc), the return value is 0.

Error codes

For details about the error codes, see Utils Error Codes.

ID	Error Message
10200013	${propertyName} cannot be set for the buffer that has only a getter.

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from("12345678");
console.info(JSON.stringify(buf.length));
// Output: 8
let arrayBuffer = buf.buffer;
console.info(JSON.stringify(new Uint8Array(arrayBuffer)));
// Output: {"0":49,"1":50,"2":51,"3":52,"4":53,"5":54,"6":55,"7":56}
console.info(JSON.stringify(buf.byteOffset));
// Output: 0
let buf1 = buffer.from("abcd");
console.info(JSON.stringify(buf1.byteOffset));
// Output: 8

compare

compare(target: Buffer | Uint8Array, targetStart?: number, targetEnd?: number, sourceStart?: number, sourceEnd?: number): -1 | 0 | 1

Compares this Buffer object with another object.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
target	Buffer | Uint8Array	Yes	Target Buffer object to compare.
targetStart	number	No	Offset to the start of the data to compare in the target Buffer object. The default value is 0.
targetEnd	number	No	Offset to the end of the data to compare in the target Buffer object (not inclusive). The default value is the length of the target Buffer object.
sourceStart	number	No	Offset to the start of the data to compare in this Buffer object. The default value is 0.
sourceEnd	number	No	Offset to the end of the data to compare in this Buffer object (not inclusive). The default value is the length of this Buffer object.

Return value

Type	Description
number	Comparison result. The value 0 is returned if the two Buffer objects are the same; 1 is returned if this object comes after the target object when sorted; -1 is returned if this object comes before the target object when sorted.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[targetStart/targetEnd/sourceStart/sourceEnd]" is out of range. It must be >= 0 and <= [right range]. Received value is: [targetStart/targetEnd/sourceStart/sourceEnd]

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9]);
let buf2 = buffer.from([5, 6, 7, 8, 9, 1, 2, 3, 4]);

console.info(buf1.compare(buf2, 5, 9, 0, 4).toString());
// Output: 0
console.info(buf1.compare(buf2, 0, 6, 4).toString());
// Output: -1
console.info(buf1.compare(buf2, 5, 6, 5).toString());
// Output: 1

copy

copy(target: Buffer| Uint8Array, targetStart?: number, sourceStart?: number, sourceEnd?: number): number

Copies data at the specified position in this Buffer object to the specified position in another Buffer object.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
target	Buffer | Uint8Array	Yes	Buffer or Uint8Array object to which data is copied.
targetStart	number	No	Offset to the start position in the target object where data is copied. The default value is 0.
sourceStart	number	No	Offset to the start position in this Buffer object where data is copied. The default value is 0.
sourceEnd	number	No	Offset to the end position in this Buffer object (not inclusive). The default value is the length of this Buffer object.

Return value

Type	Description
number	Total length of the data copied, in bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[targetStart/sourceStart/sourceEnd]" is out of range. It must be >= 0. Received value is: [targetStart/sourceStart/sourceEnd]

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.allocUninitializedFromPool(26);
let buf2 = buffer.allocUninitializedFromPool(26).fill('!');

for (let i = 0; i < 26; i++) {
  buf1.writeInt8(i + 97, i);
}

buf1.copy(buf2, 8, 16, 20);
console.info(buf2.toString('ascii', 0, 25));
// Output: !!!!!!!!qrst!!!!!!!!!!!!!

entries

entries(): IterableIterator<[number, number]>

Creates and returns an iterator that contains key-value pairs of this Buffer object.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
IterableIterator<[number, number]>	Iterator that contains the key and value, both of which are of the number type.

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from('buffer');
let pair = buf.entries();
let next: IteratorResult<Object[]> = pair.next();
while (!next.done) {
  console.info("buffer: " + next.value);
  /*
  Output: buffer: 0,98
           buffer: 1,117
           buffer: 2,102
           buffer: 3,102
           buffer: 4,101
           buffer: 5,114
   */
  next = pair.next();
}

equals

equals(otherBuffer: Uint8Array | Buffer): boolean

Checks whether this Buffer object is the same as another Buffer object.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
otherBuffer	Uint8Array | Buffer	Yes	Buffer object to compare.

Return value

Type	Description
boolean	Check result. The value true is returned if the two objects are the same; otherwise, false is returned.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.from('ABC');
let buf2 = buffer.from('414243', 'hex');
let buf3 = buffer.from('ABCD');

console.info(buf1.equals(buf2).toString());
// Output: true
console.info(buf1.equals(buf3).toString());
// Output: false

fill

fill(value: string | Buffer | Uint8Array | number, offset?: number, end?: number, encoding?: BufferEncoding): Buffer

Fills this Buffer object at the specified position. By default, data is filled cyclically.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	string | Buffer | Uint8Array | number	Yes	Value to fill.
offset	number	No	Offset to the start position in this Buffer object where data is filled. The default value is 0.
end	number	No	Offset to the end position in this Buffer object (not inclusive). The default value is the length of this Buffer object.
encoding	BufferEncoding	No	Encoding format (valid only when value is a string). The default value is 'utf8'.

Return value

Type	Description
Buffer	Buffer object filled with the specified value.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[offset/end]" is out of range. It must be >= 0 and <= [right range]. Received value is: [offset/end]

Example

import { buffer } from '@kit.ArkTS';

let b = buffer.allocUninitializedFromPool(50).fill('h');
console.info(b.toString());
// Output: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

includes

includes(value: string | number | Buffer | Uint8Array, byteOffset?: number, encoding?: BufferEncoding): boolean

Checks whether this Buffer object contains the specified value.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	string | number | Buffer | Uint8Array	Yes	Value to match.
byteOffset	number	No	Number of bytes to skip before starting to check data. If the offset is a negative number, data is checked from the end of the Buffer object. The default value is 0.
encoding	BufferEncoding	No	Encoding format (valid only when value is a string). The default value is 'utf8'.

Return value

Type	Description
boolean	Check result. The value true is returned if the object contains the specified value; otherwise, false is returned.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from('this is a buffer');
console.info(buf.includes('this').toString());
// Output: true
console.info(buf.includes('be').toString());
// Output: false

indexOf

indexOf(value: string | number | Buffer | Uint8Array, byteOffset?: number, encoding?: BufferEncoding): number

Obtains the index of the first occurrence of the specified value in this Buffer object. If no match is found, -1 is returned.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	string | number | Buffer | Uint8Array	Yes	Value to match.
byteOffset	number	No	Number of bytes to skip before starting to check data. If the offset is a negative number, data is checked from the end of the Buffer object. The default value is 0.
encoding	BufferEncoding	No	Encoding format (valid only when value is a string). The default value is 'utf8'.

Return value

Type	Description
number	Index obtained.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from('this is a buffer');
console.info(buf.indexOf('this').toString());
// Output: 0
console.info(buf.indexOf('is').toString());
// Output: 2

keys

keys(): IterableIterator<number>

Creates and returns an iterator that contains the keys of this Buffer object.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
IterableIterator<number>	Iterator created.

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from('buffer');
let keys = buf.keys();
for (const key of keys) {
  console.info(key.toString());
}
/*
Output: 0
        1
        2
        3
        4
        5
 */

lastIndexOf

lastIndexOf(value: string | number | Buffer | Uint8Array, byteOffset?: number, encoding?: BufferEncoding): number

Obtains the index of the last occurrence of the specified value in this Buffer object. If no match is found, -1 is returned.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	string | number | Buffer | Uint8Array	Yes	Value to match.
byteOffset	number	No	Number of bytes to skip before starting to check data. If the offset is a negative number, data is checked from the end of the Buffer object. The default value is the length of this Buffer object.
encoding	BufferEncoding	No	Encoding format (valid only when value is a string). The default value is 'utf8'.

Return value

Type	Description
number	Index obtained.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from('this buffer is a buffer');
console.info(buf.lastIndexOf('this').toString());
// Output: 0
console.info(buf.lastIndexOf('buffer').toString());
// Output: 17

readBigInt64BE

readBigInt64BE(offset?: number): bigint

Reads a 64-bit, big-endian, signed big integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
bigint	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 8. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x70,
  0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78]);
console.info(buf.readBigInt64BE(0).toString());
// Output: 7161960797921896816

let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeBigInt64BE(BigInt(0x0102030405060708), 0);
console.info("result = " + result);
// Output: result = 8

readBigInt64LE

readBigInt64LE(offset?: number): bigint

Reads a 64-bit, little-endian, signed big integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
bigint	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 8. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x70,
  0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78]);
console.info(buf.readBigUInt64LE(0).toString());
// Output: 8100120198111388771

let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeBigUInt64BE(BigInt(0xdecafafecacefade), 0);
console.info("result = " + result);
// Output: result = 8

readBigUInt64BE

readBigUInt64BE(offset?: number): bigint

Reads a 64-bit, big-endian, unsigned big integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
bigint	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 8. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x70,
  0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78]);
console.info(buf.readBigUInt64BE(0).toString());
// Output: 7161960797921896816
let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeBigUInt64BE(BigInt(0xdecafafecacefade), 0);
console.info("result = " + result);
// Output: result = 8

readBigUInt64LE

readBigUInt64LE(offset?: number): bigint

Reads a 64-bit, little-endian, unsigned big integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
bigint	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 8. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x70,
  0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78]);
console.info(buf.readBigUInt64LE(0).toString());
// Output: 8100120198111388771

let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeBigUInt64BE(BigInt(0xdecafafecacefade), 0);
console.info("result = " + result);
// Output: result = 8

readDoubleBE

readDoubleBE(offset?: number): number

Reads a 64-bit, big-endian, double-precision floating-point number from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 8. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
console.info(buf.readDoubleBE(0).toString());
// Output: 8.20788039913184e-304
let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeDoubleBE(123.456, 0);
console.info("result = " + result);
// Output: result = 8

readDoubleLE

readDoubleLE(offset?: number): number

Reads a 64-bit, little-endian, double-precision floating-point number from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 8. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
console.info(buf.readDoubleLE(0).toString());
// Output: 5.447603722011605e-270
let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeDoubleLE(123.456, 0);
console.info("result = " + result);
// Output: result = 8

readFloatBE

readFloatBE(offset?: number): number

Reads a 32-bit, big-endian, single-precision floating-point number from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 4. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
console.info(buf.readFloatBE(0).toString());
// Output: 2.387939260590663e-38
let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeFloatBE(0xcabcbcbc, 0);
console.info("result = " + result);
// Output: result = 4

readFloatLE

readFloatLE(offset?: number): number

Reads a 32-bit, little-endian, single-precision floating-point number from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 4. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
console.info(buf.readFloatLE(0).toString());
// Output: 1.539989614439558e-36
let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeFloatLE(0xcabcbcbc, 0);
console.info("result = " + result);
// Output: result = 4

readInt8

readInt8(offset?: number): number

Reads an 8-bit signed integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 1

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 1. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([-1, 5]);
console.info(buf.readInt8(0).toString());
// Output: 0
console.info(buf.readInt8(1).toString());
// Output: 5
let buf1 = buffer.allocUninitializedFromPool(2);
let result = buf1.writeInt8(0x12);
console.info("result = " + result);
// Output: result = 1

readInt16BE

readInt16BE(offset?: number): number

Reads a 16-bit, big-endian, signed integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 2

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 2. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0, 5]);
console.info(buf.readInt16BE(0).toString());
// Output: 5
let buf1 = buffer.alloc(2);
let result = buf1.writeInt16BE(0x1234, 0);
console.info("result = " + result);
// Output: result = 2

readInt16LE

readInt16LE(offset?: number): number

Reads a 16-bit, little-endian, signed integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 2

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 2. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0, 5]);
console.info(buf.readInt16LE(0).toString());
// Output: 1280
let buf1 = buffer.alloc(2);
let result = buf1.writeInt16BE(0x1234, 0);
console.info("result = " + result);
// Output: result = 2

readInt32BE

readInt32BE(offset?: number): number

Reads a 32-bit, big-endian, signed integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 4. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0, 0, 0, 5]);
console.info(buf.readInt32BE(0).toString());
// Output: 5
let buf1 = buffer.alloc(4);
let result = buf1.writeInt32BE(0x12345678, 0);
console.info("result = " + result);
// Output: result = 4

readInt32LE

readInt32LE(offset?: number): number

Reads a 32-bit, little-endian, signed integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 4. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0, 0, 0, 5]);
console.info(buf.readInt32LE(0).toString());
// Output: 83886080
let buf1 = buffer.alloc(4);
let result = buf1.writeInt32BE(0x12345678, 0);
console.info("result = " + result);
// Output: result = 4

readIntBE

readIntBE(offset: number, byteLength: number): number

Reads the specified number of bytes from this Buffer object at the specified offset, and interprets the result as a big-endian, two's complement signed value that supports up to 48 bits of precision.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	Yes	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - byteLength
byteLength	number	Yes	Number of bytes to read. Value range: 1 <= byteLength <= 6

Return value

Type	Description
number	Data read. If the offset is a decimal, undefined is returned.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from("ab");
let num = buf.readIntBE(0, 1);
console.info(num.toString());
// Output: 97
let buf1 = buffer.allocUninitializedFromPool(6);
let result = buf1.writeIntBE(0x123456789011, 0, 6);
console.info("result = " + result);
// Output: result = 6

readIntLE

readIntLE(offset: number, byteLength: number): number

Reads the specified number of bytes from this Buffer object at the specified offset and interprets the result as a little-endian, two's complement signed value that supports up to 48 bits of precision.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	Yes	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - byteLength
byteLength	number	Yes	Number of bytes to read. Value range: 1 <= byteLength <= 6

Return value

Type	Description
number	Data read. If the offset is a decimal, undefined is returned.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.info(buf.readIntLE(0, 6).toString(16));
// Output: -546f87a9cbee
let buf1 = buffer.allocUninitializedFromPool(6);
let result = buf1.writeIntLE(0x123456789011, 0, 6);
console.info("result = " + result);
// Output: result = 6

readUInt8

readUInt8(offset?: number): number

Reads an 8-bit unsigned integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 1

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 1. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([1, -2]);
console.info(buf.readUInt8(0).toString());
// Output: 1
console.info(buf.readUInt8(1).toString());
// Output: 0
let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUInt8(0x42);
console.info("result = " + result);
// Output: result = 1

readUInt16BE

readUInt16BE(offset?: number): number

Reads a 16-bit, big-endian, unsigned integer from this Buffer object at the specified offset.

System capability: SystemCapability.Utils.Lang

Atomic service API: This API can be used in atomic services since API version 11.

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 2

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 2. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x12, 0x34, 0x56]);
console.info(buf.readUInt16BE(0).toString(16));
// Output: 1234
console.info(buf.readUInt16BE(1).toString(16));
// Output: 3456
let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUInt16BE(0x1234, 0);
console.info("result = " + result);
// Output: result = 2

readUInt16LE

readUInt16LE(offset?: number): number

Reads a 16-bit, little-endian, unsigned integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 2

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 2. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x12, 0x34, 0x56]);
console.info(buf.readUInt16LE(0).toString(16));
// Output: 3412
console.info(buf.readUInt16LE(1).toString(16));
// Output: 5634
let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUInt16LE(0x1234, 0);
console.info("result = " + result);
// Output: result = 2

readUInt32BE

readUInt32BE(offset?: number): number

Reads a 32-bit, big-endian, unsigned integer from this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 4. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x12, 0x34, 0x56, 0x78]);
console.info(buf.readUInt32BE(0).toString(16));
// Output: 12345678
let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUInt32BE(0x12345678, 0);
console.info("result = " + result);
// Output: result = 4

readUInt32LE

readUInt32LE(offset?: number): number

Reads a 32-bit, little-endian, unsigned integer from this Buffer object at the specified offset.

System capability: SystemCapability.Utils.Lang

Atomic service API: This API can be used in atomic services since API version 11.

Parameters

Name	Type	Mandatory	Description
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Data read.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 4. Received value is: [offset].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x12, 0x34, 0x56, 0x78]);
console.info(buf.readUInt32LE(0).toString(16));
// Output: 78563412
let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUInt32LE(0x12345678, 0);
console.info("result = " + result);
// Output: result = 4

readUIntBE

readUIntBE(offset: number, byteLength: number): number

Reads the specified number of bytes from this Buffer object at the specified offset, and interprets the result as an unsigned, big-endian integer that supports up to 48 bits of precision.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	Yes	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - byteLength
byteLength	number	Yes	Number of bytes to read. Value range: 1 <= byteLength <= 6

Return value

Type	Description
number	Data read. If the offset is a decimal, undefined is returned.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.info(buf.readUIntBE(0, 6).toString(16));
// Output: 1234567890ab
let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUIntBE(0x13141516, 0, 4);
console.info("result = " + result);
// Output: result = 4

readUIntLE

readUIntLE(offset: number, byteLength: number): number

Reads the specified number of bytes from this Buffer object at the specified offset, and interprets the result as an unsigned, little-endian integer that supports up to 48 bits of precision.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
offset	number	Yes	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - byteLength
byteLength	number	Yes	Number of bytes to read. Value range: 1 <= byteLength <= 6

Return value

Type	Description
number	Data read. If the offset is a decimal, undefined is returned.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.info(buf.readUIntLE(0, 6).toString(16));
// Output: ab9078563412
let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUIntLE(0x13141516, 0, 4);
console.info("result = " + result);
// Output: result = 4

subarray

subarray(start?: number, end?: number): Buffer

Truncates this Buffer object from the specified position to create a new Buffer object.

System capability: SystemCapability.Utils.Lang

Atomic service API: This API can be used in atomic services since API version 11.

Parameters

Name	Type	Mandatory	Description
start	number	No	Offset to the start position in this Buffer object where data is truncated. The default value is 0.
end	number	No	Offset to the end position in this Buffer object (not inclusive). The default value is the length of this Buffer object. If null is passed, an empty Buffer is returned.

Return value

Type	Description
Buffer	Buffer object created. When the value of start or end is less than 0, an empty buffer is returned.

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.allocUninitializedFromPool(26);

for (let i = 0; i < 26; i++) {
  buf1.writeInt8(i + 97, i);
}
const buf2 = buf1.subarray(0, 3);
console.info(buf2.toString('ascii', 0, buf2.length));
// Output: abc

swap16

swap16(): Buffer

Converts this Buffer object into an array of unsigned 16-bit integers and swaps the byte order in place.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
Buffer	Buffer object swapped.

Error codes

For details about the error codes, see Utils Error Codes.

ID	Error Message
10200009	The buffer size must be a multiple of 16-bits.

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.info(buf1.toString('hex'));
// Output: 0102030405060708
buf1.swap16();
console.info(buf1.toString('hex'));
// Output: 0201040306050807

swap32

swap32(): Buffer

Converts this Buffer object into an array of unsigned 32-bit integers and swaps the byte order in place.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
Buffer	Buffer object swapped.

Error codes

For details about the error codes, see Utils Error Codes.

ID	Error Message
10200009	The buffer size must be a multiple of 32-bits.

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.info(buf1.toString('hex'));
// Output: 0102030405060708
buf1.swap32();
console.info(buf1.toString('hex'));
// Output: 0403020108070605

swap64

swap64(): Buffer

Converts this Buffer object into an array of unsigned 64-bit integers and swaps the byte order in place.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
Buffer	Buffer object swapped.

Error codes

For details about the error codes, see Utils Error Codes.

ID	Error Message
10200009	The buffer size must be a multiple of 64-bits.

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.info(buf1.toString('hex'));
// Output: 0102030405060708
buf1.swap64();
console.info(buf1.toString('hex'));
// Output: 0807060504030201

toJSON

toJSON(): Object

Converts this Buffer object into a JSON object.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
Object	JSON object.

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]);
let obj = buf1.toJSON();
console.info(JSON.stringify(obj));
// Output: {"type":"Buffer","data":[1,2,3,4,5]}

toString

toString(encoding?: string, start?: number, end?: number): string

Converts the data at the specified position in this Buffer object into a string in the specified encoding format.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
encoding	string	No	Encoding format (valid only when value is a string). The default value is 'utf8'.
start	number	No	Offset to the start position of the data to convert. The default value is 0.
end	number	No	Offset to the end position of data. The default value is the length of this Buffer object.

Return value

Type	Description
string	String. When the value of start is greater than or equal to Buffer.length or start is greater than end, an empty string is returned.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.allocUninitializedFromPool(26);
for (let i = 0; i < 26; i++) {
  buf1.writeInt8(i + 97, i);
}
console.info(buf1.toString('utf-8'));
// Output: abcdefghijklmnopqrstuvwxyz

values

values(): IterableIterator<number>

Creates and returns an iterator that contains the values of this Buffer object.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
IterableIterator<number>	Iterator.

Example

import { buffer } from '@kit.ArkTS';

let buf1 = buffer.from('buffer');
let pair = buf1.values();
let next:IteratorResult<number> = pair.next();
while (!next.done) {
  console.info(next.value.toString());
  /*
  Output: 98
           117
           102
           102
           101
           114
   */
  next = pair.next();
}

write

write(str: string, offset?: number, length?: number, encoding?: string): number

Writes a string of the specified length to this Buffer object at the specified position in the given encoding format.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
str	string	Yes	String to write.
offset	number	No	Offset. The default value is 0.
length	number	No	Maximum number of bytes to write. The default value is Buffer.length minus offset.
encoding	string	No	Encoding format of the string. The default value is 'utf8'.

Return value

Type	Description
number	Number of bytes written.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[offset/length]" is out of range. It must be >= 0 and <= buf.length. Received value is: [offset/length].

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.alloc(256);
let len = buf.write('\u00bd + \u00bc = \u00be', 0);
console.info(`${len} bytes: ${buf.toString('utf-8', 0, len)}`);
// Output: 12 bytes: ½ + ¼ = ¾

let buffer1 = buffer.alloc(10);
let length = buffer1.write('abcd', 8);
console.info("length = " + length);
// Output: length = 2

writeBigInt64BE

writeBigInt64BE(value: bigint, offset?: number): number

Writes a 64-bit, big-endian, signed big integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	bigint	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeBigInt64BE(BigInt(0x0102030405060708), 0);
console.info("result = " + result);
// Output: result = 8

writeBigInt64LE

writeBigInt64LE(value: bigint, offset?: number): number

Writes a 64-bit, little-endian, signed big integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	bigint	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeBigInt64LE(BigInt(0x0102030405060708), 0);
console.info("result = " + result);
// Output: result = 8

writeBigUInt64BE

writeBigUInt64BE(value: bigint, offset?: number): number

Atomic service API: This API can be used in atomic services since API version 11.

Writes a 64-bit, big-endian, unsigned big integer to this Buffer object at the specified offset.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	bigint	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeBigUInt64BE(BigInt(0xdecafafecacefade), 0);
console.info("result = " + result);
// Output: result = 8

writeBigUInt64LE

writeBigUInt64LE(value: bigint, offset?: number): number

Writes a 64-bit, little-endian, unsigned big integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	bigint	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeBigUInt64LE(BigInt(0xdecafafecacefade), 0);
console.info("result = " + result);
// Output: result = 8

writeDoubleBE

writeDoubleBE(value: number, offset?: number): number

Writes a 64-bit, big-endian, double-precision floating-point number to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 8. Received value is: [offset]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeDoubleBE(123.456, 0);
console.info("result = " + result);
// Output: result = 8

writeDoubleLE

writeDoubleLE(value: number, offset?: number): number

Writes a 64-bit, little-endian, double-precision floating-point number to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 8

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 8. Received value is: [offset]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeDoubleLE(123.456, 0);
console.info("result = " + result);
// Output: result = 8

writeFloatBE

writeFloatBE(value: number, offset?: number): number

Writes a 32-bit, big-endian, single-precision floating-point number to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 4. Received value is: [offset]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeFloatBE(0xcafebabe, 0);
console.info("result = " + result);
// Output: result = 4

writeFloatLE

writeFloatLE(value: number, offset?: number): number

Writes a 32-bit, little-endian, single-precision floating-point number to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "offset" is out of range. It must be >= 0 and <= buf.length - 4. Received value is: [offset]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeFloatLE(0xcafebabe, 0);
console.info("result = " + result);
// Output: result = 4

writeInt8

writeInt8(value: number, offset?: number): number

Writes an 8-bit signed integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 1

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(2);
let result = buf.writeInt8(2, 0);
console.info("result = " + result);
// Output: result = 1
let result1 = buf.writeInt8(-2, 1);
console.info("result1 = " + result1);
// Output: result1 = 2

writeInt16BE

writeInt16BE(value: number, offset?: number): number

Writes a 16-bit, big-endian, signed integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 2

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(2);
let result = buf.writeInt16BE(0x0102, 0);
console.info("result = " + result);
// Output: result = 2

writeInt16LE

writeInt16LE(value: number, offset?: number): number

Writes a 16-bit, little-endian, signed integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 2

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(2);
let result = buf.writeInt16LE(0x0304, 0);
console.info("result = " + result);
// Output: result = 2

writeInt32BE

writeInt32BE(value: number, offset?: number): number

Writes a 32-bit, big-endian, signed integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeInt32BE(0x01020304, 0);
console.info("result = " + result);
// Output: result = 4

writeInt32LE

writeInt32LE(value: number, offset?: number): number

Writes a 32-bit, little-endian, signed integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeInt32LE(0x05060708, 0);
console.info("result = " + result);
// Output: result = 4

writeIntBE

writeIntBE(value: number, offset: number, byteLength: number): number

Writes a big-endian signed value of the specified length to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	Yes	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - byteLength
byteLength	number	Yes	Number of bytes to write.

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(6);
let result = buf.writeIntBE(0x1234567890ab, 0, 6);
console.info("result = " + result);
// Output: result = 6

writeIntLE

writeIntLE(value: number, offset: number, byteLength: number): number

Writes a little-endian signed value of the specified length to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	Yes	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - byteLength
byteLength	number	Yes	Number of bytes to write.

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(6);
let result = buf.writeIntLE(0x1234567890ab, 0, 6);
console.info("result = " + result);
// Output: result = 6

writeUInt8

writeUInt8(value: number, offset?: number): number

Writes an 8-bit unsigned integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 1

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeUInt8(0x3, 0);
console.info("result = " + result);
// Output: result = 1
let result1 = buf.writeUInt8(0x4, 1);
console.info("result1 = " + result1);
// Output: result1 = 2
let result2 = buf.writeUInt8(0x23, 2);
console.info("result2 = " + result2);
// Output: result2 = 3
let result3 = buf.writeUInt8(0x42, 3);
console.info("result3 = " + result3);
// Output: result3 = 4

writeUInt16BE

writeUInt16BE(value: number, offset?: number): number

Writes a 16-bit, big-endian, unsigned integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 2

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeUInt16BE(0xdead, 0);
console.info("result = " + result);
// Output: result = 2
let result1 = buf.writeUInt16BE(0xbeef, 2);
console.info("result1 = " + result1);
// Output: result1 = 4

writeUInt16LE

writeUInt16LE(value: number, offset?: number): number

Writes a 16-bit, little-endian, unsigned integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 2

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeUInt16LE(0xdead, 0);
console.info("result = " + result);
// Output: result = 2
let result1 = buf.writeUInt16LE(0xbeef, 2);
console.info("result1 = " + result1);
// Output: result1 = 4

writeUInt32BE

writeUInt32BE(value: number, offset?: number): number

Writes a 32-bit, big-endian, unsigned integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeUInt32BE(0xfeedface, 0);
console.info("result = " + result);
// Output: result = 4

writeUInt32LE

writeUInt32LE(value: number, offset?: number): number

Writes a 32-bit, little-endian, unsigned integer to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - 4

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeUInt32LE(0xfeedface, 0);
console.info("result = " + result);
// Output: result = 4

writeUIntBE

writeUIntBE(value: number, offset: number, byteLength: number): number

Writes an unsigned big-endian value of the specified length to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	Yes	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - byteLength
byteLength	number	Yes	Number of bytes to write.

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(6);
let result = buf.writeUIntBE(0x1234567890ab, 0, 6);
console.info("result = " + result);
// Output: result = 6

writeUIntLE

writeUIntLE(value: number, offset: number, byteLength: number): number

Writes an unsigned little-endian value of the specified length to this Buffer object at the specified offset.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	Yes	Offset. The default value is 0. Value range: 0 <= offset <= Buffer.length - byteLength
byteLength	number	Yes	Number of bytes to write.

Return value

Type	Description
number	Offset plus the number of written bytes.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.
10200001	The value of "[param]" is out of range. It must be >= [left range] and <= [right range]. Received value is: [param]

Example

import { buffer } from '@kit.ArkTS';

let buf = buffer.allocUninitializedFromPool(6);
let result = buf.writeUIntLE(0x1234567890ab, 0, 6);
console.info("result = " + result);
// Output: result = 6

Blob

Properties

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Name	Type	Read-Only	Optional	Description
size	number	Yes	No	Total size of the Blob object, in bytes.
type	string	Yes	No	Type of the data in the Blob object.

constructor

constructor(sources: string[] | ArrayBuffer[] | TypedArray[] | DataView[] | Blob[] , options?: Object)

A constructor used to create a Blob object.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
sources	string[] | ArrayBuffer[] | TypedArray[] | DataView[] | Blob[]	Yes	Data sources of the Blob object.
options	Object	No	options: - endings: specifies how the terminator '\n' is output. The value can be 'native' or 'transparent'. 'native' means that the terminator follows the system. 'transparent' means that the terminator stored in the Blob object remains unchanged. The default value is 'transparent'. - type: type of the data in the Blob object. This type represents the MIME type of the data. However, it is not used for type format validation. The default value is ''.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types.

Example

import { buffer } from '@kit.ArkTS';

let blob: buffer.Blob  = new buffer.Blob(['a', 'b', 'c']);

class option {
  endings: string = "";
  type: string = "";
}
let o1: option = {endings:'native', type: 'MIME'}
let blob1: buffer.Blob = new buffer.Blob(['a', 'b', 'c'], o1);

arrayBuffer

arrayBuffer(): Promise<ArrayBuffer>

Puts the Blob data into an ArrayBuffer object. This API uses a promise to return the result.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
Promise<ArrayBuffer>	Promise used to return the ArrayBuffer containing the Blob data.

Example

import { buffer } from '@kit.ArkTS';

let blob: buffer.Blob = new buffer.Blob(['a', 'b', 'c']);
let pro = blob.arrayBuffer();
pro.then((val: ArrayBuffer) => {
  let uint8Array: Uint8Array = new Uint8Array(val);
  console.info(uint8Array.toString());
  // Output: 97,98,99
});

slice

slice(start?: number, end?: number, type?: string): Blob

Creates and returns a Blob object that contains specified data from this Blob object.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
start	number	No	Offset to the start position of data. The default value is 0.
end	number	No	Offset to the end position of data. The default value is the data length in the original Blob object.
type	string	No	Type of the data in the new Blob object. The default value is ''.

Return value

Type	Description
Blob	New Blob object created.

Example

import { buffer } from '@kit.ArkTS';

let blob: buffer.Blob = new buffer.Blob(['a', 'b', 'c']);
let blob2 = blob.slice(0, 2);
let blob3 = blob.slice(0, 2, "MIME");
console.info("type:", blob3.type); // type: MIME

text

text(): Promise<string>

Decodes data using UTF-8 and returns a string. This API uses a promise to return the result.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
Promise<string>	Promise used to return the string decoded using UTF-8.

Example

import { buffer } from '@kit.ArkTS';

let blob: buffer.Blob = new buffer.Blob(['a', 'b', 'c']);
let pro = blob.text();
pro.then((val: string) => {
  console.info(val);
  // Output: abc
});