@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

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’	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 instance of the specified length.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
size	number	Yes	Size of the Buffer instance 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 utf-8.

Return value

Type	Description
Buffer	Buffer instance created.

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

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

Return value

Type	Description
Buffer	Uninitialized Buffer instance.

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

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

Return value

Type	Description
Buffer	Uninitialized Buffer instance.

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

Name	Type	Mandatory	Description
string	string | Buffer | TypedArray | DataView | ArrayBuffer | SharedArrayBuffer	Yes	Target string.
encoding	BufferEncoding	No	Encoding format of the string. The default value is utf-8.

Return value

Type	Description
number	Number of bytes of the string.

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

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

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

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

Return value

Type	Description
Buffer	Buffer instance created.

Error codes

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

ID	Error Message
10200001	The value of “length” is out of range. It must be >= 0 and <= uint32 max. Received value is: [length]

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

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

Return value

Type	Description
Buffer	Buffer instance created.

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

Name	Type	Mandatory	Description
arrayBuffer	ArrayBuffer | SharedArrayBuffer	Yes	Array of Buffer instances, whose memory is to be shared.
byteOffset	number	No	Byte offset. The default value is 0.
length	number	No	Length of the Buffer instance to create, in bytes. The default value is the length of arrayBuffer minus byteOffset.

Return value

Type	Description
Buffer	Buffer instance with shared memory.

Error codes

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

ID	Error Message
10200001	The value of “[byteOffset/length]” is out of range.

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

Name	Type	Mandatory	Description
buffer	Buffer | Uint8Array	Yes	Buffer instance to copy.

Return value

Type	Description
Buffer	Buffer instance created.

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

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 instance to create.

Return value

Type	Description
Buffer	Buffer instance created.

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

Name	Type	Mandatory	Description
string	String	Yes	String.
encoding	BufferEncoding	No	Encoding format of the string. The default value is utf-8.

Return value

Type	Description
Buffer	Buffer instance created.

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

Name	Type	Mandatory	Description
obj	Object	Yes	Object to check.

Return value

Type	Description
boolean	Returns true if the object is a Buffer instance; returns false otherwise.

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

Name	Type	Mandatory	Description
encoding	string	Yes	Encoding format.

Return value

Type	Description
boolean	Returns true if the encoding format is supported; returns false otherwise.

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

Name	Type	Mandatory	Description
source	Buffer | Uint8Array	Yes	Instance to encode.
fromEnc	string	Yes	Current encoding format.
toEnc	string	Yes	Target encoding format.

Return value

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

Example

import buffer from '@ohos.buffer';

let buf = buffer.alloc(50);
let newBuf = buffer.transcode(buffer.from('€'), 'utf-8', 'ascii');
console.log(newBuf.toString('ascii'));

Buffer

Attributes

System capability: SystemCapability.Utils.Lang

Name	Type	Readable	Writable	Description
length	number	Yes	No	Length of the Buffer instance, in bytes.
buffer	ArrayBuffer	Yes	No	ArrayBuffer object.
byteOffset	number	Yes	No	Offset of the Buffer instance in the memory pool.

Error codes

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

ID	Error Message
10200013	Cannot set property ${propertyName} of Buffer which has only a getter.

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

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

Return value

Type	Description
number	Returns 0 if the two Buffer instances are the same. Returns 1 if this instance comes after the target instance when sorted. Returns -1 if this instance comes before the target instance when sorted.

Error codes

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

ID	Error Message
10200001	The value of “[targetStart/targetEnd/sourceStart/sourceEnd]” is out of range.

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

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

Return value

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

Error codes

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

ID	Error Message
10200001	The value of “[targetStart/sourceStart/sourceEnd]” is out of range.

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

Type	Description
number	Key of the iterator.
number	Value of the iterator.

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

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

Return value

Type	Description
boolean	Returns true if the two instances are the same; returns false otherwise.

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

Name	Type	Mandatory	Description
value	string | Buffer | Uint8Array | number	Yes	Value to fill.
offset	number	No	Offset to the start position in this Buffer instance where data is filled. The default value is 0.
end	number	No	Offset to the end position in this Buffer instance (not inclusive). The default value is the length of this Buffer instance.
encoding	BufferEncoding	No	Encoding format (valid only when value is a string). The default value is utf-8.

Return value

Type	Description
Buffer	Buffer instance filled with the specified value.

Error codes

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

ID	Error Message
10200001	The value of “[offset/end]” is out of range.

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

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 instance. The default value is 0.
encoding	BufferEncoding	No	Encoding format (valid only when value is a string). The default value is utf-8.

Return value

Type	Description
boolean	Returns true if the instance contains the specified value; returns false otherwise.

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

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 instance. The default value is 0.
encoding	BufferEncoding	No	Encoding format (valid only when value is a string). The default value is utf-8.

Return value

Type	Description
number	Index obtained. If -1 is returned, the Buffer instance does not contain the specified 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

Type	Description
IterableIterator<number>	Iterator created.

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

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 instance. The default value is 0.
encoding	BufferEncoding	No	Encoding format (valid only when value is a string). The default value is utf-8.

Return value

Type	Description
number	Index obtained. If -1 is returned, the Buffer instance does not contain the specified 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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
bigint	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
bigint	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
bigint	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
bigint	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

Example

import buffer from '@ohos.buffer';

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	Yes	Number of bytes to skip before starting to read data. The default value is 0.
byteLength	number	Yes	Number of bytes to read.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
offset	number	Yes	Number of bytes to skip before starting to read data. The default value is 0.
byteLength	number	Yes	Number of bytes to read.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	No	Number of bytes to skip before starting to read data. The default value is 0.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
10200001	The value of “offset” is out of range.

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

Name	Type	Mandatory	Description
offset	number	Yes	Number of bytes to skip before starting to read data. The default value is 0.
byteLength	number	Yes	Number of bytes to read.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
offset	number	Yes	Number of bytes to skip before starting to read data. The default value is 0.
byteLength	number	Yes	Number of bytes to read.

Return value

Type	Description
number	Data read.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
start	number	No	Offset to the start position in this Buffer instance where data is truncated. The default value is 0.
end	number	No	Offset to the end position in this Buffer instance (not inclusive). The default value is the length of this Buffer instance.

Return value

Type	Description
Buffer	Buffer instance created.

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

Type	Description
Buffer	Buffer instance swapped.

Error codes

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

ID	Error Message
10200009	Buffer size must be a multiple of 16-bits

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

Type	Description
Buffer	Buffer instance swapped.

Error codes

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

ID	Error Message
10200009	Buffer size must be a multiple of 32-bits

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

Type	Description
Buffer	Buffer instance swapped.

Error codes

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

ID	Error Message
10200009	Buffer size must be a multiple of 64-bits

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

Type	Description
Object	JSON object.

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

Name	Type	Mandatory	Description
encoding	string	No	Encoding format (valid only when value is a string). The default value is utf-8.
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 the data to convert. The default value is the length of this Buffer instance.

Return value

Type	Description
string	String obtained.

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

Type	Description
IterableIterator<number>	Iterator.

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

Name	Type	Mandatory	Description
str	string	Yes	String to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.
length	number	No	Maximum number of bytes to write. The default value is the length of the Buffer instance minus the offset.
encoding	string	No	Encoding format of the string. The default value is utf-8.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
10200001	The value of “[offset/length]” is out of range.

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

Name	Type	Mandatory	Description
value	bigint	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	bigint	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	bigint	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	bigint	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	Yes	Number of bytes to skip before starting to write data. The default value is 0.
byteLength	number	Yes	Number of bytes to write.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	Yes	Number of bytes to skip before starting to write data. The default value is 0.
byteLength	number	Yes	Number of bytes to write.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	No	Number of bytes to skip before starting to write data. The default value is 0.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	Yes	Number of bytes to skip before starting to write data. The default value is 0.
byteLength	number	Yes	Number of bytes to write.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@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

Name	Type	Mandatory	Description
value	number	Yes	Data to write.
offset	number	Yes	Number of bytes to skip before starting to write data. The default value is 0.
byteLength	number	Yes	Number of bytes to write.

Return value

Type	Description
number	Number of bytes written.

Error codes

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

ID	Error Message
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 '@ohos.buffer';

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

Blob

Attributes

System capability: SystemCapability.Utils.Lang

Name	Type	Readable	Writable	Description
size	number	Yes	No	Total size of the Blob instance, in bytes.
type	string	Yes	No	Type of the data in the Blob instance.

constructor

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

A constructor used to create a Blob instance.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
sources	string[] | ArrayBuffer[] | TypedArray[] | DataView[] | Blob[]	Yes	Data sources of the Blob instance.
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 instance remains unchanged. The default value is ‘transparent’. - type: type of the data in the Blob instance. This type represents the MIME type of the data. However, it is not used for type format validation. The default value is “.

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

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

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

Return value |Type|Description| |——–|——–| |Blob|New Blob instance created.|

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 |Type|Description| |——–|——–| |Promise<string>|Promise used to return the text encoded in UTF-8.|

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)
});

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