@ohos.buffer (Buffer)

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

You can use the APIs provided by the Buffer module 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 '@ohos.buffer';

BufferEncoding

Enumerates the supported encoding formats.

System capability: SystemCapability.Utils.Lang

buffer.alloc

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

Creates and initializes a Buffer instance of the specified length.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

let buf1 = buffer.alloc(5);
let buf2 = buffer.alloc(5, 'a');
let buf3 = buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');

buffer.allocUninitializedFromPool

allocUninitializedFromPool(size: number): Buffer

Creates a Buffer instance of the specified size from the buffer pool, without initializing it. You need to use fill() to initialize the Buffer instance created.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(10);
buf.fill(0);

buffer.allocUninitialized

allocUninitialized(size: number): Buffer

Creates a Buffer instance 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 instance created.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitialized(10);
buf.fill(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.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

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

buffer.compare

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

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

console.log(Number(res).toString()); // Print 1.

buffer.concat

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

Concatenates an array of Buffer instances of the specified length into a new instance.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

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

buffer.from

from(array: number[]): Buffer;

Creates a Buffer instance with the specified array.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

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

buffer.from

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

Creates a Buffer instance of the specified length that shares memory with arrayBuffer.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let ab = new ArrayBuffer(10);
let buf = buffer.from(ab, 0, 2);

buffer.from

from(buffer: Buffer | Uint8Array): Buffer

Creates a Buffer instance with the copy of another instance.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

let buf1 = buffer.from('buffer');
let buf2 = buffer.from(buf1);

buffer.from

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

Creates a Buffer instance based on the specified object.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

let buf = buffer.from(new String('this is a test'), 'utf8', 14);

buffer.from

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

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

console.log (buf1.toString()); // Print: this is a test
console.log (buf2.toString()); // print: this is a test

buffer.isBuffer

isBuffer(obj: Object): boolean

Checks whether the specified object is a Buffer instance.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

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

buffer.isEncoding

isEncoding(encoding: string): boolean

Checks whether the encoding format is supported.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

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

buffer.transcode

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

let newBuf = buffer.transcode(buffer.from('€'), 'utf-8', 'ascii');
console.log(newBuf.toString('ascii'));

Buffer

Attributes

System capability: SystemCapability.Utils.Lang

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from("1236");
console.log(JSON.stringify(buf.length));
let arrayBuffer = buf.buffer;
console.log(JSON.stringify(new Uint8Array(arrayBuffer)));
console.log(JSON.stringify(buf.byteOffset));

compare

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

Compares this Buffer instance with another instance.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

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

copy

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

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.log(buf2.toString('ascii', 0, 25));
// Print: !!!!!!! qrst!!!!!!!!!!!!!

entries

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

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

System capability: SystemCapability.Utils.Lang

Return value

Example

import buffer from '@ohos.buffer';

let buf = buffer.from('buffer');
let pair = buf.entries();
let next: IteratorResult<Object[]> = pair.next();
while (!next.done) {
  console.info("buffer: " + next.value);
  next = pair.next();
}

equals

equals(otherBuffer: Uint8Array | Buffer): boolean

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

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

console.log(buf1.equals(buf2).toString());	// Print: true
console.log(buf1.equals(buf3).toString());	// Print: false

fill

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let b = buffer.allocUninitializedFromPool(50).fill('h');
console.log(b.toString());

includes

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

Checks whether this Buffer instance contains the specified value.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

let buf = buffer.from('this is a buffer');
console.log(buf.includes('this').toString());	// Print: true
console.log(buf.includes('be').toString());	// Print: 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 instance.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

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

keys

keys(): IterableIterator<number>

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

System capability: SystemCapability.Utils.Lang

Return value

Example

import buffer from '@ohos.buffer';

let buf = buffer.from('buffer');
let numbers = Array.from(buf.values());
for (const key of numbers) {
  console.log(key.toString());
}

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 instance.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

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

readBigInt64BE

readBigInt64BE(offset?: number): bigint

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

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

let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeBigInt64BE(BigInt(0x0102030405060708), 0);

readBigInt64LE

readBigInt64LE(offset?: number): bigint

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x70, 
        0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78]);
console.log(buf.readBigInt64LE(0).toString());

let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeBigInt64BE(BigInt(0x0102030405060708), 0);

readBigUInt64BE

readBigUInt64BE(offset?: number): bigint

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x70, 
        0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78]);
console.log(buf.readBigUInt64BE(0).toString());

let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeBigUInt64BE(BigInt(0xdecafafecacefade), 0);

readBigUInt64LE

readBigUInt64LE(offset?: number): bigint

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

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

let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeBigUInt64BE(BigInt(0xdecafafecacefade), 0);

readDoubleBE

readDoubleBE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
console.log(buf.readDoubleBE(0).toString());

let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeDoubleBE(123.456, 0);

readDoubleLE

readDoubleLE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
console.log(buf.readDoubleLE(0).toString());

let buf1 = buffer.allocUninitializedFromPool(8);
let result = buf1.writeDoubleLE(123.456, 0);

readFloatBE

readFloatBE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
console.log(buf.readFloatBE(0).toString());

let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeFloatBE(0xcabcbcbc, 0);

readFloatLE

readFloatLE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
console.log(buf.readFloatLE(0).toString());

let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeFloatLE(0xcabcbcbc, 0);

readInt8

readInt8(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([-1, 5]);
console.log(buf.readInt8(0).toString());	// Print: 0
console.log(buf.readInt8(1).toString());	// Print: 5

let buf1 = buffer.allocUninitializedFromPool(2);
let result = buf1.writeInt8(0x12);

readInt16BE

readInt16BE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0, 5]);
console.log(buf.readInt16BE(0).toString());	// Print: 5

let buf1 = buffer.alloc(2);
let result = buf1.writeInt16BE(0x1234, 0);

readInt16LE

readInt16LE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0, 5]);
console.log(buf.readInt16LE(0).toString());	// Print: 1280

let buf1 = buffer.alloc(2);
let result = buf1.writeInt16BE(0x1234, 0);

readInt32BE

readInt32BE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0, 0, 0, 5]);
console.log(buf.readInt32BE(0).toString());	// Print: 5

let buf1 = buffer.alloc(4);
let result = buf1.writeInt32BE(0x12345678, 0);

readInt32LE

readInt32LE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0, 0, 0, 5]);
console.log(buf.readInt32LE(0).toString());	// Print: 83886080

let buf1 = buffer.alloc(4);
let result = buf1.writeInt32BE(0x12345678, 0);

readIntBE

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

Reads the specified number of bytes from this Buffer instance 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.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from("ab");
let num = buf.readIntBE(0, 1);
console.log(num.toString()); // 97

let buf1 = buffer.allocUninitializedFromPool(6);
let result = buf1.writeIntBE(0x123456789011, 0, 6);

readIntLE

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

Reads the specified number of bytes from this Buffer instance 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.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.log(buf.readIntLE(0, 6).toString(16));

let buf1 = buffer.allocUninitializedFromPool(6);
let result = buf1.writeIntLE(0x123456789011, 0, 6);

readUInt8

readUInt8(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([1, -2]);
console.log(buf.readUInt8(0).toString());
console.log(buf.readUInt8(1).toString());

let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUInt8(0x42);

readUInt16BE

readUInt16BE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0x12, 0x34, 0x56]);
console.log(buf.readUInt16BE(0).toString(16));
console.log(buf.readUInt16BE(1).toString(16));

let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUInt16BE(0x1234, 0);

readUInt16LE

readUInt16LE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0x12, 0x34, 0x56]);
console.log(buf.readUInt16LE(0).toString(16));
console.log(buf.readUInt16LE(1).toString(16));

let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUInt16LE(0x1234, 0);

readUInt32BE

readUInt32BE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0x12, 0x34, 0x56, 0x78]);
console.log(buf.readUInt32BE(0).toString(16));

let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUInt32BE(0x12345678, 0);

readUInt32LE

readUInt32LE(offset?: number): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0x12, 0x34, 0x56, 0x78]);
console.log(buf.readUInt32LE(0).toString(16));

let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUInt32LE(0x12345678, 0);

readUIntBE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.log(buf.readUIntBE(0, 6).toString(16));

let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUIntBE(0x13141516, 0, 4);

readUIntLE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.log(buf.readUIntLE(0, 6).toString(16));

let buf1 = buffer.allocUninitializedFromPool(4);
let result = buf1.writeUIntLE(0x13141516, 0, 4);

subarray

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

let buf1 = buffer.allocUninitializedFromPool(26);

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

swap16

swap16(): Buffer

Interprets this Buffer instance as an array of unsigned 16-bit integers and swaps the byte order in place.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

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

buf1.swap16();
console.log(buf1.toString('hex'));	// Print: 0201040306050807

swap32

swap32(): Buffer

Interprets this Buffer instance as an array of unsigned 32-bit integers and swaps the byte order in place.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

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

buf1.swap32();
console.log(buf1.toString('hex'));	// Print: 0403020108070605

swap64

swap64(): Buffer

Interprets this Buffer instance as an array of unsigned 64-bit integers and swaps the byte order in place.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

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

toJSON

toJSON(): Object

Converts this Buffer instance into a JSON object.

System capability: SystemCapability.Utils.Lang

Return value

Example

import buffer from '@ohos.buffer';

let buf1 = buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]);
let obj = buf1.toJSON();
console.log(JSON.stringify(obj));
// Print: {"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 instance into a string in the specified encoding format.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

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

values

values(): IterableIterator<number>

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

System capability: SystemCapability.Utils.Lang

Return value

Example

import buffer from '@ohos.buffer';

let buf1 = buffer.from('buffer');
let pair = buf1.values()
let next:IteratorResult<number> = pair.next()
while (!next.done) {
  console.log(next.value.toString());
  next = pair.next();
}

write

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

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

let buffer1 = buffer.alloc(10);
let length = buffer1.write('abcd', 8);

writeBigInt64BE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeBigInt64BE(BigInt(0x0102030405060708), 0);

writeBigInt64LE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeBigInt64LE(BigInt(0x0102030405060708), 0);

writeBigUInt64BE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeBigUInt64BE(BigInt(0xdecafafecacefade), 0);

writeBigUInt64LE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeBigUInt64LE(BigInt(0xdecafafecacefade), 0);

writeDoubleBE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeDoubleBE(123.456, 0);

writeDoubleLE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeDoubleLE(123.456, 0);

writeFloatBE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeFloatBE(0xcafebabe, 0);

writeFloatLE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(8);
let result = buf.writeFloatLE(0xcafebabe, 0);

writeInt8

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(2);
let result = buf.writeInt8(2, 0);
let result1 = buf.writeInt8(-2, 1);

writeInt16BE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(2);
let result = buf.writeInt16BE(0x0102, 0);

writeInt16LE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(2);
let result = buf.writeInt16LE(0x0304, 0);

writeInt32BE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeInt32BE(0x01020304, 0);

writeInt32LE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeInt32LE(0x05060708, 0);

writeIntBE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(6);
let result = buf.writeIntBE(0x1234567890ab, 0, 6);

writeIntLE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(6);
let result = buf.writeIntLE(0x1234567890ab, 0, 6);

writeUInt8

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeUInt8(0x3, 0);
let result1 = buf.writeUInt8(0x4, 1);
let result2 = buf.writeUInt8(0x23, 2);
let result3 = buf.writeUInt8(0x42, 3);

writeUInt16BE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeUInt16BE(0xdead, 0);
let result1 = buf.writeUInt16BE(0xbeef, 2);

writeUInt16LE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeUInt16LE(0xdead, 0);
let result1 = buf.writeUInt16LE(0xbeef, 2);

writeUInt32BE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeUInt32BE(0xfeedface, 0);

writeUInt32LE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(4);
let result = buf.writeUInt32LE(0xfeedface, 0);

writeUIntBE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(6);
let result = buf.writeUIntBE(0x1234567890ab, 0, 6);

writeUIntLE

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

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.allocUninitializedFromPool(6);
let result = buf.writeUIntLE(0x1234567890ab, 0, 6);

Blob

Attributes

System capability: SystemCapability.Utils.Lang

constructor

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

A constructor used to create a Blob instance.

System capability: SystemCapability.Utils.Lang

Parameters

Example

import buffer from '@ohos.buffer';

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 instance. This API uses a promise to return the result.

System capability: SystemCapability.Utils.Lang

Return value

Example

import buffer from '@ohos.buffer';

let blob: buffer.Blob = new buffer.Blob(['a', 'b', 'c']);
let pro = blob.arrayBuffer();
pro.then((val: ArrayBuffer) => {
  let uintarr: Uint8Array = new Uint8Array(val);
  console.log(uintarr.toString());
});

slice

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

Creates a Blob instance by copying specified data from this Blob instance.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Example

import buffer from '@ohos.buffer';

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

text

text(): Promise<string>

Returns text in UTF-8 format. This API uses a promise to return the result.

System capability: SystemCapability.Utils.Lang

Return value

Example

import buffer from '@ohos.buffer';

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