Pure JavaScript is unicode friendly, however it isn't so for binary data. While handling TCP streams or the file system, it is necessary to handle octet streams. Node provides Buffer class which provides instances to store raw data that's similar to an array of integers but tallies with a raw memory allocation outside the V8 heap.
Node Buffer class is a global class that can be obtained in an application without having to import the buffer module.
Creating Buffers
First Method
var buf = new Buffer(10);
Second Method
var buf = new Buffer([10, 20, 30, 40, 50]);
Third Method
var buf = new Buffer("Best Tutorial Platform", "utf-8");
Writing to Buffers
Syntax
buf.write(string[, offset][, length][, encoding])
Parameter Details
- string - This is the string data to be written to buffer.
- offset - This is the buffer's index to begin writing at. Default value is 0.
- length - This is the number of bytes to write. Defaults to buffer.length.
- encoding - The encoding to use. 'utf8' is the default encoding.
Return Value
Example
buf = new Buffer(256); len = buf.write("Best Tutorial Platform"); console.log("Octets written : "+ len);
Output
Octets written : 22
Reading from Buffers
Syntax
buf.toString([encoding][, start][, end])
Parameter Details
- encoding - This is the encoding to use. 'utf8' is the default encoding.
- start - This the beginning index to start reading, defaults to 0.
- end - This is the end index to end reading, defaults to complete buffer.
Return Value
Example
buf = new Buffer(26); for (var i = 0 ; i < 26 ; i++) { buf[i] = i + 97; } console.log( buf.toString('ascii')); // outputs: abcdefghijklmnopqrstuvwxyz console.log( buf.toString('ascii',0,5)); // outputs: abcde console.log( buf.toString('utf8',0,5)); // outputs: abcde console.log( buf.toString(undefined,0,5)); // encoding defaults to 'utf8', outputs abcde
Output
abcdefghijklmnopqrstuvwxyz abcde abcde abcde
Convert Buffer to JSON
Syntax
buf.toJSON()
Return Value
Example
var buf = new Buffer('Simply Easy Learning'); var json = buf.toJSON(buf); console.log(json);
Output
{ type: 'Buffer', data: [ 83, 105, 109, 112, 108, 121, 32, 69, 97, 115, 121, 32, 76, 101, 97, 114, 110, 105, 110, 103 ] }
Concatenate Buffers
Syntax
Buffer.concat(list[, totalLength])
Parameter Details
- list - This is an array list of Buffer objects to be concatenated.
- totalLength - This is the total of the buffers when concatenated.
Return Value
Example
var buffer1 = new Buffer('WebDesignTutorialz '); var buffer2 = new Buffer('Best Tutorial Platform'); var buffer3 = Buffer.concat([buffer1,buffer2]); console.log("buffer3 content: " + buffer3.toString());
Output
buffer3 content: WebDesignTutorialz Best Tutorial Platform
Compare Buffers
Syntax
buf.compare(otherBuffer);
Parameter Details
- otherBuffer - This is the other buffer which will be compared with buf.
Return Value
Example
var buffer1 = new Buffer('ABC'); var buffer2 = new Buffer('ABCD'); var result = buffer1.compare(buffer2); if(result < 0) { console.log(buffer1 +" comes before " + buffer2); } else if(result === 0) { console.log(buffer1 +" is same as " + buffer2); } else { console.log(buffer1 +" comes after " + buffer2); }
Output
ABC comes before ABCD
Copy Buffer
Syntax
buf.copy(targetBuffer[, targetStart][, sourceStart][, sourceEnd])
Parameter Details
- targetBuffer - Buffer object where buffer will be copied.
- targetStart - Number, Optional, Default: 0.
- sourceStart - Number, Optional, Default: 0.
- sourceEnd - Number, Optional, Default: buffer.length.
Return Value
Example
var buffer1 = new Buffer('ABC'); //copy a buffer var buffer2 = new Buffer(3); buffer1.copy(buffer2); console.log("buffer2 content: " + buffer2.toString());
Output
buffer2 content: ABC
Slice Buffer
Syntax
buf.slice([start][, end])
Parameter Details
- start - Number, Optional, Default: 0.
- end - Number, Optional, Default: buffer.length.
Return Value
Example
var buffer1 = new Buffer('WebDesignTutorialz'); //slicing a buffer var buffer2 = buffer1.slice(0,9); console.log("buffer2 content: " + buffer2.toString());
Output
buffer2 content: WebDesign
Buffer Length
Syntax
buf.length;
Return Value
Example
var buffer = new Buffer('WebDesignTutorialz'); //length of the buffer console.log("buffer length: " + buffer.length);
Output
buffer length: 18
Method Reference
Sr.No. | Method & Description |
---|---|
1 | new Buffer(size) Allocates a new buffer of size octets. Note that the size must be no more than kMaxLength. Otherwise, a RangeError will be thrown here. |
2 | new Buffer(buffer) Copies the passed buffer data onto a new Buffer instance. |
3 | new Buffer(str[, encoding]) Allocates a new buffer containing the given str. encoding defaults to 'utf8'. |
4 | buf.length Returns the size of the buffer in bytes. Note that this is not necessarily the size of the contents. length refers to the amount of memory allocated for the buffer object. It does not change when the contents of the buffer are changed. |
5 | buf.write(string[, offset][, length][, encoding]) Writes a string to the buffer at offset using the given encoding. offset defaults to 0, encoding defaults to 'utf8'. length is the number of bytes to write. Returns the number of octets written. |
6 | buf.writeUIntLE(value, offset, byteLength[, noAssert]) Writes a value to the buffer at the specified offset and byteLength. Supports up to 48 bits of accuracy. Set noAssert to true to skip validation of value and offset. Defaults to false. |
7 | buf.writeUIntBE(value, offset, byteLength[, noAssert]) Writes a value to the buffer at the specified offset and byteLength. Supports up to 48 bits of accuracy. Set noAssert to true to skip validation of value and offset. Defaults to false. |
8 | buf.writeIntLE(value, offset, byteLength[, noAssert]) Writes a value to the buffer at the specified offset and byteLength. Supports up to 48 bits of accuracy. Set noAssert to true to skip validation of value and offset. Defaults to false. |
9 | buf.writeIntBE(value, offset, byteLength[, noAssert]) Writes a value to the buffer at the specified offset and byteLength. Supports up to 48 bits of accuracy. Set noAssert to true to skip validation of value and offset. Defaults to false. |
10 | buf.readUIntLE(offset, byteLength[, noAssert]) A generalized version of all numeric read methods. Supports up to 48 bits of accuracy. Set noAssert to true to skip validation of offset. It means that the offset may be beyond the end of the buffer. Defaults to false. |
11 | buf.readUIntBE(offset, byteLength[, noAssert]) A generalized version of all numeric read methods. Supports up to 48 bits of accuracy. Set noAssert to true to skip validation of offset. It means that the offset may be beyond the end of the buffer. Defaults to false. |
12 | buf.readIntLE(offset, byteLength[, noAssert]) A generalized version of all numeric read methods. Supports up to 48 bits of accuracy. Set noAssert to true to skip validation of offset. It means that the offset may be beyond the end of the buffer. Defaults to false. |
13 | buf.readIntBE(offset, byteLength[, noAssert]) A generalized version of all numeric read methods. Supports up to 48 bits of accuracy. Set noAssert to true to skip validation of offset. It means that the offset may be beyond the end of the buffer. Defaults to false. |
14 | buf.toString([encoding][, start][, end]) Decodes and returns a string from buffer data encoded using the specified character set encoding. |
15 | buf.toJSON() Returns a JSON-representation of the Buffer instance. JSON.stringify implicitly calls this function when stringifying a Buffer instance. |
16 | buf[index] Get and set the octet at index. The values refer to individual bytes, so the legal range is between 0x00 and 0xFF hex or 0 and 255. |
17 | buf.equals(otherBuffer) Returns a boolean if this buffer and otherBuffer have the same bytes. |
18 | buf.compare(otherBuffer) Returns a number indicating whether this buffer comes before or after or is the same as the otherBuffer in sort order. |
19 | buf.copy(targetBuffer[, targetStart][, sourceStart][, sourceEnd]) Copies data from a region of this buffer to a region in the target buffer even if the target memory region overlaps with the source. If undefined, the targetStart and sourceStart parameters default to 0, while sourceEnd defaults to buffer.length. |
20 | buf.slice([start][, end]) Returns a new buffer which references the same memory as the old, but offset and cropped by the start (defaults to 0) and end (defaults to buffer.length) indexes. Negative indexes start from the end of the buffer. |
21 | buf.readUInt8(offset[, noAssert]) Reads an unsigned 8 bit integer from the buffer at the specified offset. Set noAssert to true to skip validation of offset. It means that the offset may be beyond the end of the buffer. Defaults to false. |
22 | buf.readUInt16LE(offset[, noAssert]) Reads an unsigned 16-bit integer from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
23 | buf.readUInt16BE(offset[, noAssert]) Reads an unsigned 16-bit integer from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
24 | buf.readUInt32LE(offset[, noAssert]) Reads an unsigned 32-bit integer from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
25 | buf.readUInt32BE(offset[, noAssert]) Reads an unsigned 32-bit integer from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
26 | buf.readInt8(offset[, noAssert]) Reads a signed 8-bit integer from the buffer at the specified offset. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
27 | buf.readInt16LE(offset[, noAssert]) Reads a signed 16-bit integer from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
28 | buf.readInt16BE(offset[, noAssert]) Reads a signed 16-bit integer from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
29 | buf.readInt32LE(offset[, noAssert]) Reads a signed 32-bit integer from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
30 | buf.readInt32BE(offset[, noAssert]) Reads a signed 32-bit integer from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
31 | buf.readFloatLE(offset[, noAssert]) Reads a 32-bit float from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
32 | buf.readFloatBE(offset[, noAssert]) Reads a 32-bit float from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
33 | buf.readDoubleLE(offset[, noAssert]) Reads a 64-bit double from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
34 | buf.readDoubleBE(offset[, noAssert]) Reads a 64-bit double from the buffer at the specified offset with the specified endian format. Set noAssert to true to skip validation of offset. It means the offset may be beyond the end of the buffer. Defaults to false. |
35 | buf.writeUInt8(value, offset[, noAssert]) Writes a value to the buffer at the specified offset. Note that the value must be a valid unsigned 8-bit integer. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
36 | buf.writeUInt16LE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note that the value must be a valid unsigned 16-bit integer. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and the offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of correctness. Defaults to false. |
37 | buf.writeUInt16BE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note that the value must be a valid unsigned 16-bit integer. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and the offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
38 | buf.writeUInt32LE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note that the value must be a valid unsigned 32-bit integer. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and the offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
39 | buf.writeUInt32BE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note that the value must be a valid unsigned 32-bit integer. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and the offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
40 | buf.writeInt8(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note that the value must be a valid signed 8-bit integer. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and the offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
41 | buf.writeInt16LE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note that the value must be a valid signed 16-bit integer. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and the offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
42 | buf.writeInt16BE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note that the value must be a valid signed 16-bit integer. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
43 | buf.writeInt32LE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note that the value must be a valid signed 32-bit integer. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and the offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
44 | buf.writeInt32BE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note that the value must be a valid signed 32-bit integer. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and the offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of correctness. Defaults to false. |
45 | buf.writeFloatLE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note that the value must be a valid 32-bit float. Set noAssert to true to skip validation of value and offset. It means that the value may be too large for the specific function and the offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
46 | buf.writeFloatBE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note, value must be a valid 32-bit float. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and the offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
47 | buf.writeDoubleLE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note, value must be a valid 64-bit double. Set noAssert to true to skip validation of value and offset. It means that value may be too large for the specific function and offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
48 | buf.writeDoubleBE(value, offset[, noAssert]) Writes a value to the buffer at the specified offset with the specified endian format. Note, value must be a valid 64-bit double. Set noAssert to true to skip validation of value and offset. It means the value may be too large for the specific function and the offset may be beyond the end of the buffer leading to the values being silently dropped. It should not be used unless you are certain of its correctness. Defaults to false. |
49 | buf.fill(value[, offset][, end]) Fills the buffer with the specified value. If the offset (defaults to 0) and end (defaults to buffer.length) are not given, it will fill the entire buffer. |
Class Methods
Sr.No. | Method & Description |
---|---|
1 | Buffer.isEncoding(encoding) Returns true if the encoding is a valid encoding argument, false otherwise. |
2 | Buffer.isBuffer(obj) Tests if obj is a Buffer. |
3 | Buffer.byteLength(string[, encoding]) Gives the actual byte length of a string. encoding defaults to 'utf8'. It is not the same as String.prototype.length, since String.prototype.length returns the number of characters in a string. |
4 | Buffer.concat(list[, totalLength]) Returns a buffer which is the result of concatenating all the buffers in the list together. |
5 | Buffer.compare(buf1, buf2) The same as buf1.compare(buf2). Useful for sorting an array of buffers. |
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