Nodejs Buffers

9

Reading from Nodejs Buffers:

In order to read the data store in our buffer we will be using the below syntax:

Syntax:

buf.read([encoding],[, start],[, end])

Parameter:

• Encoding: It represents the type of encoding, by default it is “UTF8”
• Start: It indicates the index from which reading will start.
• End: It represents the index till which it has to read.

Return value:

It returns the string from the buffer.

Example of reading from a buffer:

var buffer = Buffer.alloc(16)
buffer.write("DataFlair", "utf-8")
console.log(buffer.toString("utf-8", 0, 9))

Output:

Buffer to Json:

To convert the buffer data to a json format buffer.toJSON() method is used.

Syntax:

buffer.toJSON()

Return type:

It returns a json value for the given buffer.

Code for converting buffer to json:

let buffer = new Buffer('Welcome to DataFlair');
let json = buffer.toJSON(buffer);
console.log(json);

Output:

Concatenate Buffer:

It is used to concatenate two buffers together to make a single buffer. Below is syntax for doing the same.

Syntax:

Buffer.concat(list[, totalLength])

Parameter:

• List: It is the list of buffers that will be concatenated
  totalLength: Represents the total length after concatenation
• Return value:
  Returns the concatenated buffer.

Example of concatenating buffers:

var buffer1 = new Buffer('Data');
var buffer2 = new Buffer('Flair');
var buffer3 = Buffer.concat([buffer1, buffer2]);

console.log(buffer3.toString());

Output:

Iterating over a buffer:

In order to iterate a buffer use a for loop which you use in javascript.

Code for iterating over a buffer

const buf = Buffer.from('DataFlair!')
for (const item of buf) {
    console.log(item)
}

Output:

Length of Buffer:

To get the length of the buffer that you have created use the buffer.length() method. It will return a number representing the length of the buffer.

Code to know the length of buffer

const buf = Buffer.from('DataFlair')
console.log(buf.length)

Output:

Changing contents of Nodejs buffers:

When we want to edit our buffer we treat it like an array and replace the content in the same way as we do incase of arrays.

Code for changing the contents of buffer

const buf = Buffer.from('DataFlair')
buf[0] = 100
console.log(buf.toString())

Output

Slicing buffer in Nodejs:

Slicing is used when we want to get a particular part from our buffer.

Code for Slicing the buffer:

const buf = Buffer.from('DataFlair')
const slice = buf.subarray(0, 4)
console.log(slice.toString())

Output:

Copy Nodejs buffer:

To copy data from one buffer to another we make another buffer of the same size and then set the content of the buffer.

Code for Copying a buffer:

const buf = Buffer.from('DataFlair')
let bufcopy = Buffer.alloc(9)
bufcopy.set(buf)
console.log(bufcopy.toString())

Output:

Compare Nodejs buffers:

To compare one buffer with another we use the buffer.compare method.

Syntax:

buffer.compare(‘anotherBufferName’)

Code for Comparing Nodejs buffers:

let buffer1 = new Buffer('Hello from DataFlair');
let buffer2 = new Buffer('Welcome to DataFlair');
let 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:

Methods Reference:

• Comparing buffer:

To compare two buffers we use the buffer.compare(buf1,buf2)

• isBuffer:

To know whether the given object is a buffer or not we use the buffer.isBuffer(obj) method.

• isEncoding:

It returns true if the encoding provided is a valid encoding.

Summary

In this article, we discussed Nodejs buffers and their different properties. Hope you liked the article.