# Buffer > **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. 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, receive and upload files, and use network protocols. ## Modules to Import ```ts import buffer from '@ohos.buffer'; ``` ## Buffer ### alloc alloc(size: number, fill?: string | Buffer | number, encoding?: BufferEncoding): Buffer Allocates and initializes a **Buffer** instance of the specified size. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | size | number | Yes| Size of the **Buffer** instance to allocate, in bytes.| | fill | string \| Buffer \| number | No| Pre-filled value. 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 | Initialized **Buffer** instance.| **Example** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.alloc(5); let buf2 = buffer.alloc(5, 'a'); let buf3 = buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64'); ``` ### allocUninitializedFromPool allocUninitializedFromPool(size: number): Buffer Allocates a **Buffer** instance of the specified size from the buffer pool, without initializing it. To initialize the **Buffer** instance, call the **fill()** function. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | size | number | Yes| Size of the **Buffer** instance to allocate, in bytes.| **Return value** | Type| Description| | -------- | -------- | | Buffer | Uninitialized **Buffer** instance.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(10); buf.fill(0); ``` ### allocUninitialized allocUninitialized(size: number): Buffer Allocates a **Buffer** instance of the specified size, without initializing it. This API does not allocate memory from the buffer pool. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | size | number | Yes|Size of the **Buffer** instance to allocate, in bytes.| **Return value** | Type| Description| | -------- | -------- | | Buffer | Uninitialized **Buffer** instance.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitialized(10); buf.fill(0); ``` ### byteLength byteLength(string: string | Buffer | TypeArray | 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 \| TypeArray \| DataView \| ArrayBuffer \| SharedArrayBuffer | Yes| Target string.| | encoding | BufferEncoding | No| Encoding format. The default value is **utf-8**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes of the string.| **Example** ```ts 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 ``` ### compare compare(buf1: Buffer | Uint8Array, buf2: Buffer | Uint8Array): number Compares two **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| | -------- | -------- | | number | 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** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.from('1234'); let buf2 = buffer.from('0123'); console.log(buf1.compare(buf2)); // Print 1 ``` ### concat concat(list: Buffer[] | Uint8Array[], totalLength?: number): Buffer Concatenates an array of **Buffer** instances into a new instance of the specified length. **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 the new **Buffer** instance, in bytes.| **Return value** | Type| Description| | -------- | -------- | | Buffer | **Buffer** instance created.| **Example** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.from("1234"); let buf2 = buffer.from("abcd"); let buf = buffer.concat([buf1, buf2]); console.log(buf); // ``` ### 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** ```ts import buffer from '@ohos.buffer'; let arrayList = new ArrayList(); let buf = buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]); console.log(buf); // Print: ``` ### from from(arrayBuffer: ArrayBuffer | SharedArrayBuffer, byteOffset?: number, length?: number): Buffer Creates a **Buffer** instance that shares memory with the specified array of **Buffer** instances. **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.| **Example** ```ts import buffer from '@ohos.buffer'; let ab = new ArrayBuffer(10); let buf = buffer.from(ab, 0, 2); ``` ### from from(data: Buffer | Uint8Array): Buffer Creates a **Buffer** instance with the copy of another instance. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | data | Buffer \| Uint8Array | Yes| Instance to copy.| **Return value** | Type| Description| | -------- | -------- | | Buffer | **Buffer** instance created.| **Example** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.from('buffer'); let buf2 = buffer.from(buf1); ``` ### 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 | No| Byte offset or encoding format.| | length | number | No| Length of the **Buffer** instance to create.| **Return value** | Type| Description| | -------- | -------- | | Buffer | **Buffer** instance created.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from(new String('this is a test')); ``` ### 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** ```ts 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()); ``` ### 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** ```ts import buffer from '@ohos.buffer'; buffer.isBuffer(buffer.alloc(10)); // true buffer.isBuffer(buffer.from('foo')); // true buffer.isBuffer('a string'); // false buffer.isBuffer([]); // false buffer.isBuffer(new Uint8Array(1024)); // false ``` ### 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** ```ts import buffer from '@ohos.buffer'; console.log (Buffer.isEncoding ('utf-8')); // Print: true console.log (Buffer.isEncoding ('hex')); // Print: true console.log (Buffer.isEncoding ('utf/8')); // Print: false console.log (Buffer.isEncoding ('')); // Print: false ``` ### 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 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.| | Type| Description| | -------- | -------- | | number | Returns **0** if the two **Buffer** instances are the same.
Returns **1** if the target instance comes before this instance when sorted.
Returns **-1** if the target instance comes after this instance when sorted.| **Example** ```ts 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); // Print: 0 console.log (buf1.compare (buf2, 0, 6, 4); // Print: -1 console.log (buf1.compare (buf2, 5, 6, 5)); // 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.| **Example** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.allocUninitializedFromPool(26); let buf2 = buffer.allocUninitializedFromPool(26).fill('!'); for (let i = 0; i < 26; i++) { buf1[i] = i + 97; } 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 **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from('buffer'); for (let pair of buf.entries()) { console.log(pair); } ``` ### equals equals(otherBuffer: Buffer | Uint8Array): boolean Checks whether this **Buffer** instance is the same as another **Buffer** instance. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | otherBuffer | Buffer \| Uint8Array | Yes| **Buffer** instance to compare.| **Return value** | Type| Description| | -------- | -------- | | boolean | Returns **true** if the two instances are the same; returns **false** otherwise.| **Example** ```ts 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)); // Print: true console.log (buf1.equals (buf3)); // 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.| **Example** ```ts 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 checking data. If the offset is a negative number, data is searched from the end of the **Buffer** instance. The default value is **0**.| | encoding | BufferEncoding | No| Encoding format used if **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** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from('this is a buffer'); console.log (buf.includes ('this')); // Print: true console.log (buf.includes ('be')); // 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 checking data. If the offset is a negative number, data is searched from the end of the **Buffer** instance. The default value is **0**.| | encoding | BufferEncoding | No| Encoding format used if **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** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from('this is a buffer'); console.log (buf.indexOf('this')); // Print: 0 console.log(buf.indexOf('is')); // 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.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from('buffer'); for (const key of buf.keys()) { console.log(key); } ``` ### 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 checking data. If the offset is a negative number, data is searched from the end of the **Buffer** instance. The default value is **0**.| | encoding | BufferEncoding | No| Encoding format used if **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** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from('this buffer is a buffer'); console.log(buf.lastIndexOf('this')); // Print: 0 console.log(buf.lastIndexOf('buffer')); // Print:17 ``` ### readBigInt64BE readBigInt64BE(offset: number): number Reads a signed, big-endian 64-bit integer from this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | offset | number | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | A signed, big-endian 64-bit integer.| **Example** ```ts 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)); ``` ### readBigInt64LE readBigInt64LE(offset: number): number Reads a signed, little-endian 64-bit integer from this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | offset | number | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | A signed, little-endian 64-bit integer.| **Example** ```ts 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)); ``` ### readBigUInt64BE readBigUInt64BE(offset: number): number Reads an unsigned, big-endian 64-bit integer from this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | offset | number | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | An unsigned, big-endian 64-bit integer.| **Example** ```ts 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)); ``` ### readBigUInt64LE readBigUInt64LE(offset: number): number Reads an unsigned, little-endian 64-bit integer from this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | offset | number | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | An unsigned, little-endian 64-bit integer.| **Example** ```ts 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)); ``` ### 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 | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | A 64-bit, big-endian double-precision floating-point number.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]); console.log(buf.readDoubleBE(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 | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | A 64-bit, little-endian double-precision floating-point number.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]); console.log(buf.readDoubleLE(0)); ``` ### readFloatBE readFloatBE(offset: number): number Reads a 32-bit, big-endian floating-point number from this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | offset | number | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | A 32-bit, big-endian floating-point number.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]); console.log(buf.readFloatBE(0)); ``` ### readFloatLE readFloatLE(offset: number): number Reads a 32-bit, little-endian floating-point number from this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | offset | number | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | A 32-bit, little-endian floating-point number.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([1, 2, 3, 4, 5, 6, 7, 8]); console.log(buf.readFloatLE(0)); ``` ### readInt8 readInt8(offset: number): number Reads a signed 8-bit integer from this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | offset | number | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | A signed 8-bit integer.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([-1, 5]); console.log (buf.readInt8(0)); // Print: -1 console.log (buf.readInt8(1); // Print: 5 ``` ### readInt16BE readInt16BE(offset: number): number Reads a signed, big-endian 16-bit integer from this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | offset | number | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | A signed, big-endian 16-bit integer.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = Buffer.from([0, 5]); console.log (buf.readInt16BE(0)); // Print: 5 ``` ### readInt16LE readInt16LE(offset: number): number Reads a signed, little-endian 16-bit integer from this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | offset | number | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | A signed, little-endian 16-bit integer.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = Buffer.from([0, 5]); console.log (buf.readInt16BE(0)); // Print: 1280 ``` ### readInt32BE readInt32BE(offset: number): number Reads a signed, big-endian 32-bit integer from this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | offset | number | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | A signed, big-endian 32-bit integer.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([0, 0, 0, 5]); console.log(buf.readInt32BE(0)); // Print: 5 ``` ### readInt32LE readInt32LE(offset: number): number Reads a signed, little-endian 32-bit integer from this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | offset | number | Yes| Number of bytes to skip before reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | A signed, little-endian 32-bit integer.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([0, 0, 0, 5]); console.log (buf.readInt32LE(0)); // Print: 83886080 ``` ### 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 | No| Number of bytes to skip before reading data. The default value is **0**.| | byteLength | number | No| Number of bytes to read.| **Return value** | Type| Description| | -------- | -------- | | number | Data read.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = Buffer.from("ab"); let num = buf.readIntBE(0, 1); console.log(num); // 97 ``` ### 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 | No| Number of bytes to skip before reading data. The default value is **0**.| | byteLength | number | No| Number of bytes to read.| **Return value** | Type| Description| | -------- | -------- | | number | Data read.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]); console.log(buf.readIntLE(0, 6).toString(16)); ``` ### readUInt8 readUInt8(offset: number): number Reads an unsigned 8-bit 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 reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | An unsigned 8-bit integer.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([1, -2]); console.log(buf.readUInt8(0)); console.log(buf.readUInt8(1)); ``` ### readUInt16BE readUInt16BE(offset: number): number Reads an unsigned, big-endian 16-bit 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 reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | An unsigned, big-endian 16-bit integer.| **Example** ```ts 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)); ``` ### readUInt16LE readUInt16LE(offset: number): number Reads an unsigned, little-endian 16-bit 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 reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | An unsigned, little-endian 16-bit integer.| **Example** ```ts 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)); ``` ### readUInt32BE readUInt32BE(offset: number): number Reads an unsigned, big-endian 32-bit 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 reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | An unsigned, big-endian 32-bit integer.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([0x12, 0x34, 0x56, 0x78]); console.log(buf.readUInt32BE(0).toString(16)); ``` ### readUInt32LE readUInt32LE(offset: number): number Reads an unsigned, little-endian 32-bit 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 reading data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | An unsigned, little-endian 32-bit integer.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([0x12, 0x34, 0x56, 0x78]); console.log(buf.readUInt32LE(0).toString(16)); ``` ### 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 | No| Number of bytes to skip before reading data. The default value is **0**.| | byteLength | number | No| Number of bytes to read.| **Return value** | Type| Description| | -------- | -------- | | number | Data read.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]); console.log(buf.readUIntBE(0, 6).toString(16)); ``` ### 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 | No| Number of bytes to skip before reading data. The default value is **0**.| | byteLength | number | No| Number of bytes to read.| **Return value** | Type| Description| | -------- | -------- | | number | Data read.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]); console.log(buf.readUIntLE(0, 6).toString(16)); ``` ### 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** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.allocUninitializedFromPool(26); for (let i = 0; i < 26; i++) { buf1[i] = i + 97; } 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.| **Example** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]); console.log(buf1); // Print: buf1.swap16(); console.log(buf1); // Print: ``` ### 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.| **Example** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]); console.log(buf1); // Print: buf1.swap32(); console.log(buf1); // Print: ``` ### 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.| **Example** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]); console.log(buf1); // Print: buf1.swap64(); console.log(buf1); // Print: ``` ### toJSON toJSON(): Object Converts this **Buffer** instance into a JSON object. **System capability**: SystemCapability.Utils.Lang **Return value** | Type| Description| | -------- | -------- | | Object | JSON object.| **Example** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]); let buf2 = buffer.from(buf1.toJSON()) let json = JSON.stringify(buf2); console.log(json); // 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 of the 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** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.allocUninitializedFromPool(26); for (let i = 0; i < 26; i++) { buf1[i] = i + 97; } 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 created.| **Example** ```ts import buffer from '@ohos.buffer'; let buf1 = buffer.from('buffer'); for (const value of buf.values()) { console.log(value); } ``` ### 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 writing 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 | BufferEncoding | No| Encoding format of the string. The default value is **utf-8**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts 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 buffer = Buffer.alloc(10); let length = buffer.write('abcd', 8); ``` ### writeBigInt64BE writeBigInt64BE(value: number, offset?: number): number Writes a signed, big-endian 64-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(8); buf.writeBigInt64BE(0x0102030405060708n, 0); ``` ### writeBigInt64LE writeBigInt64LE(value : number, offset? : number): number Writes a signed, little-endian 64-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(8); buf.writeBigInt64LE(0x0102030405060708n, 0); ``` ### writeBigUInt64BE writeBigUInt64BE(value : number, offset? : number): number Writes an unsigned, big-endian 64-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(8); buf.writeBigUInt64BE(0xdecafafecacefaden, 0); ``` ### writeBigUInt64LE writeBigUInt64LE(value : number, offset? : number): number Writes an unsigned, little-endian 64-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(8); buf.writeBigUInt64LE(0xdecafafecacefaden, 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(8); 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(8); buf.writeDoubleLE(123.456, 0); ``` ### writeFloatBE writeFloatBE(value : number, offset? : number): number Writes a 32-bit, big-endian 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(8); buf.writeFloatBE(0xcafebabe, 0); ``` ### writeFloatLE writeFloatLE(value : number, offset? : number): number Writes a 32-bit, little-endian 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(8); buf.writeFloatLE(0xcafebabe, 0); ``` ### writeInt8 writeInt8(value : number, offset? : number): number Writes a signed 8-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(2); buf.writeInt8(2, 0); buf.writeInt8(-2, 1); ``` ### writeInt16BE writeInt16BE(value : number, offset? : number): number Writes a signed, big-endian 16-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(2); buf.writeInt16BE(0x0102, 0); ``` ### writeInt16LE writeInt16LE(value : number, offset : number): number Writes a signed, little-endian 16-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(2); buf.writeInt16LE(0x0304, 0); ``` ### writeInt32BE writeInt32BE(value : number, offset : number): number Writes a signed, big-endian 32-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(4); buf.writeInt32BE(0x01020304, 0); ``` ### writeInt32LE writeInt32LE(value : number, offset : number): number Writes a signed, little-endian 32-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(4); 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 | No| Number of bytes to skip before writing data. The default value is **0**.| | byteLength | number | No| Number of bytes to write.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(6); 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 | No| Number of bytes to skip before writing data. The default value is **0**.| | byteLength | number | No| Number of bytes to write.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(6); buf.writeIntLE(0x1234567890ab, 0, 6); ``` ### writeUInt8 writeUInt8(value : number, offset : number): number Writes an unsigned 8-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(4); buf.writeUInt8(0x3, 0); buf.writeUInt8(0x4, 1); buf.writeUInt8(0x23, 2); buf.writeUInt8(0x42, 3); ``` ### writeUInt16BE writeUInt16BE(value : number, offset : number): number Writes an unsigned, big-endian 16-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(4); buf.writeUInt16BE(0xdead, 0); buf.writeUInt16BE(0xbeef, 2); ``` ### writeUInt16LE writeUInt16LE(value : number, offset : number): number Writes an unsigned, little-endian 16-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(4); buf.writeUInt16LE(0xdead, 0); buf.writeUInt16LE(0xbeef, 2); ``` ### writeUInt32BE writeUInt32BE(value : number, offset : number): number Writes an unsigned, big-endian 32-bit 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 writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(4); buf.writeUInt32BE(0xfeedface, 0); ``` ### writeUInt32LE writeUInt32LE(value : number, offset : number): number Writes an unsigned, little-endian 32-bit integer to this **Buffer** instance at the specified offset. **System capability**: SystemCapability.Utils.Lang **Parameters** | Name| Type| Mandatory| Description| | -------- | -------- | -------- | -------- | | value | number | Yes| Number to write.| | offset | number | No| Number of bytes to skip before writing data. The default value is **0**.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(4); buf.writeUInt32LE(0xfeedface, 0); ``` ### writeUIntBE writeUIntBE(value : number, offset : number, byteLength : number): number Writes a big-endian unsigned 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 | No| Number of bytes to skip before writing data. The default value is **0**.| | byteLength | number | No| Number of bytes to write.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(6); buf.writeUIntBE(0x1234567890ab, 0, 6); ``` ### writeUIntLE writeUIntLE(value : number, offset : number, byteLength : number): number Writes a little-endian unsigned 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 | No| Number of bytes to skip before writing data. The default value is **0**.| | byteLength | number | No| Number of bytes to write.| **Return value** | Type| Description| | -------- | -------- | | number | Number of bytes written.| **Example** ```ts import buffer from '@ohos.buffer'; let buf = buffer.allocUninitializedFromPool(6); buf.writeUIntLE(0x1234567890ab, 0, 6); ``` ### transcode transcode(source : Buffer | Uint8Array, fromEnc : string, toEnc : string): Buffer Transcodes the given **Buffer** or **Uint8Array** instance 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** ```ts import buffer from '@ohos.buffer'; let buf = buffer.alloc(50); let newBuf = buf.transcode(buffer.from('€'), 'utf8', 'ascii'); console.log(newBuf.toString('ascii')); ``` ## 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**: 'transparent' or 'native'.
- **type**: type of the data in **Blob**.| **Example** ```ts import buffer from '@ohos.buffer'; let blob1 = new buffer.Blob(['a', 'b', 'c']); let blob1 = new buffer.Blob(['a', 'b', 'c'], {endings:'native', type: 'MIME'}); ``` ### encode 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** ```ts let blob = new buffer.Blob(['a', 'b', 'c']); let pro = blob.arrayBuffer(); pro.then(val => { console.log(val) }); ``` ### 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.| | end | number | No| Offset to the end position of the data to copy.| | type | string | No| Type of the data in the new **Blob** instance.| **Return value** | Type| Description| | -------- | -------- | | Blob | New **Blob** instance created.| **Example** ```ts let 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. **System capability**: SystemCapability.Utils.Lang **Return value** | Type| Description| | -------- | -------- | | Promise<string> | Promise used to return the text encoded in UTF-8.| **Example** ```ts let blob = new buffer.Blob(['a', 'b', 'c']); let pro = blob.text(); pro.then(val => { console.log(val) }); ```