update docs

Signed-off-by: NAnnie_wang <annie.wangli@huawei.com>

en/application-dev/reference/apis/js-apis-buffer.md

+# 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**.<br>Returns **1** if **buf1** comes after **buf2** when sorted.<br>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[]&nbsp;\|&nbsp;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); // <Buffer 31 32 33 34 61 62 63 64>
+```
+
+### 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: <Buffer 62 75 66 66 65 72>
+```
+
+### 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&nbsp;\|&nbsp;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&nbsp;\|&nbsp;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&nbsp;\|&nbsp;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&nbsp;\|&nbsp;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.<br>Returns **1** if the target instance comes before this instance when sorted.<br>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&nbsp;\|&nbsp;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&lt;[number,&nbsp;number]&gt;
+
+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&nbsp;\|&nbsp;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&nbsp;\|&nbsp;Buffer&nbsp;\|&nbsp;Uint8Array&nbsp;\|&nbsp;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&nbsp;\|&nbsp;number&nbsp;\|&nbsp;Buffer&nbsp;\|&nbsp;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&nbsp;\|&nbsp;number&nbsp;\|&nbsp;Buffer&nbsp;\|&nbsp;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. <br>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&lt;number&gt;
+
+Creates and returns an iterator that contains the keys of this **Buffer** instance.
+
+**System capability**: SystemCapability.Utils.Lang
+
+**Return value**
+
+| Type| Description|
+| -------- | -------- |
+|  IterableIterator&lt;number&gt; | 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&nbsp;\|&nbsp;number&nbsp;\|&nbsp;Buffer&nbsp;\|&nbsp;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.<br>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: <Buffer 01 02 03 04 05 06 07 08>
+
+buf1.swap16();
+console.log(buf1); // Print: <Buffer 02 01 04 03 06 05 08 07>
+```
+
+### 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: <Buffer 01 02 03 04 05 06 07 08>
+
+buf1.swap32();
+console.log(buf1); // Print: <Buffer 04 03 02 01 08 07 06 05>
+```
+
+### 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: <Buffer 01 02 03 04 05 06 07 08>
+buf1.swap64();
+console.log(buf1);	// Print: <Buffer 08 07 06 05 04 03 02 01>
+```
+
+### 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&lt;number&gt;
+
+Creates and returns an iterator that contains the values of this **Buffer** instance.
+
+**System capability**: SystemCapability.Utils.Lang
+
+**Return value**
+
+| Type| Description|
+| -------- | -------- |
+| IterableIterator&lt;number&gt; | 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&nbsp;\|&nbsp;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[]&nbsp;\|&nbsp;ArrayBuffer[]&nbsp;\|&nbsp;TypedArray[]&nbsp;\|&nbsp;DataView[]&nbsp;\|&nbsp;Blob[] | Yes| Data sources of the **Blob** instance.|
+| options | Object | No| options:<br>- **endings**: 'transparent' or 'native'.<br>- **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&lt;ArrayBuffer&gt;
+
+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&lt;ArrayBuffer&gt; | 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&lt;string&gt;
+
+Returns text in UTF-8 format.
+
+**System capability**: SystemCapability.Utils.Lang
+
+**Return value**
+| Type| Description|
+| -------- | -------- |
+| Promise&lt;string&gt; | 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)
+  });
+  ```