Pure JavaScript is Unicode friendly, but it is not so for binary data. While dealing with TCP streams or the file system, it’s necessary to handle octet streams. Node provides Buffer class which provides instances to store raw data similar to an array of integers but corresponds to a raw memory allocation outside the V8 heap.
Buffer class is a global class that can be accessed in an application without importing the buffer module.
Node Buffer can be constructed in a variety of ways.
Following is the syntax to create an uninitiated Buffer of 10 octets −
var buf = new Buffer(10);
Following is the syntax to create a Buffer from a given array −
var buf = new Buffer([10, 20, 30, 40, 50]);
Following is the syntax to create a Buffer from a given string and optionally encoding type −
var buf = new Buffer("Simply Easy Learning", "utf-8");
Though “utf8” is the default encoding, you can use any of the following encodings “ascii”, “utf8”, “utf16le”, “ucs2”, “base64” or “hex”.
Following is the syntax of the method to write into a Node Buffer −
buf.write(string[, offset][, length][, encoding])
Here is the description of the parameters used −
This method returns the number of octets written. If there is not enough space in the buffer to fit the entire string, it will write a part of the string.
buf = new Buffer(256);
len = buf.write("Simply Easy Learning");
console.log("Octets written : "+ len);
When the above program is executed, it produces the following result −
Octets written : 20
Following is the syntax of the method to read data from a Node Buffer −
buf.toString([encoding][, start][, end])
Here is the description of the parameters used −
This method decodes and returns a string from buffer data encoded using the specified character set encoding.
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
When the above program is executed, it produces the following result −
abcdefghijklmnopqrstuvwxyz abcde abcde abcde
Following is the syntax of the method to convert a Node Buffer into JSON object −
buf.toJSON()
This method returns a JSON-representation of the Buffer instance.
var buf = new Buffer('Simply Easy Learning');
var json = buf.toJSON(buf);
console.log(json);
When the above program is executed, it produces the following result −
{ type: 'Buffer',
data:
[
83,
105,
109,
112,
108,
121,
32,
69,
97,
115,
121,
32,
76,
101,
97,
114,
110,
105,
110,
103
]
}
Following is the syntax of the method to concatenate Node buffers to a single Node Buffer −
Buffer.concat(list[, totalLength])
Here is the description of the parameters used −
This method returns a Buffer instance.
var buffer1 = new Buffer('TutorialsPoint ');
var buffer2 = new Buffer('Simply Easy Learning');
var buffer3 = Buffer.concat([buffer1,buffer2]);
console.log("buffer3 content: " + buffer3.toString());
When the above program is executed, it produces the following result −
buffer3 content: TutorialsPoint Simply Easy Learning
Following is the syntax of the method to compare two Node buffers −
buf.compare(otherBuffer);
Here is the description of the parameters used −
Returns a number indicating whether it comes before or after or is the same as the otherBuffer in sort order.
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);
}
When the above program is executed, it produces the following result −
ABC comes before ABCD
Following is the syntax of the method to copy a node buffer −
buf.copy(targetBuffer[, targetStart][, sourceStart][, sourceEnd])
Here is the description of the parameters used −
No return value. 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.
var buffer1 = new Buffer('ABC');
//copy a buffer
var buffer2 = new Buffer(3);
buffer1.copy(buffer2);
console.log("buffer2 content: " + buffer2.toString());
When the above program is executed, it produces the following result −
buffer2 content: ABC
Following is the syntax of the method to get a sub-buffer of a node buffer −
buf.slice([start][, end])
Here is the description of the parameters used −
Returns a new buffer which references the same memory as the old one, 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.
var buffer1 = new Buffer('TutorialsPoint');
//slicing a buffer
var buffer2 = buffer1.slice(0,9);
console.log("buffer2 content: " + buffer2.toString());
When the above program is executed, it produces the following result −
buffer2 content: Tutorials
Following is the syntax of the method to get a size of a node buffer in bytes −
buf.length;
Returns the size of a buffer in bytes.
var buffer = new Buffer('TutorialsPoint');
//length of the buffer
console.log("buffer length: " + buffer.length);
When the above program is executed, it produces following result −
buffer length: 14
| 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. |