Node.js | Buffer.readUInt32LE() Method

Last Updated : 30 Dec, 2019

The Buffer.readUInt32LE() method is an inbuilt application programming interface of class Buffer within the Buffer module which is used to read 32-bit value from an allocated buffer at a specified offset in little endian format.

Syntax:

Buffer.readUInt32LE( offset )

Parameters: This method accept single parameter offset which specifies the number of bytes to skip before read or simply signify the index in the buffer. The value of offset lies 0 <= offset <= Buffer.length – 4. Its default value is 0.

Return Value: This method returns an integer value that read from buffer in little endian format.

Below examples illustrate the use of Buffer.readUInt32LE() method in Node.js:

Example 1:

// Node program to demonstrate the   
// Buffer.readUInt32LE() Method 
   
// Allocating buffer from array 
const buf = Buffer.from([0x21, 0x09, 0x19, 
             0x98, 0x16, 0x09, 0x19, 0x96]); 
  
// Printing allocated buffer 
console.log(buf); 
   
// Reading 32bits data from the buffer 
// and printing it as a string 
console.log(buf.readUInt32LE(0).toString(16)); 
console.log(buf.readUInt32LE(1).toString(16)); 
console.log(buf.readUInt32LE(2).toString(16)); 
console.log(buf.readUInt32LE(3).toString(16)); 
console.log(buf.readUInt32LE(4).toString(16)); 

Output:

<Buffer 21 09 19 98 16 09 19 96>
98190921
16981909
9169819
19091698
96190916

Example 2:

// Node program to demonstrate the   
// Buffer.readUInt32LE() Method 
   
// Allocating buffer from array 
const buf = Buffer.from([0x21, 0x09, 0x19, 0x98, 
                     0x34, 0xae, 0xe8, 0xff]); 
  
// Printing allocated buffer 
console.log(buf); 
   
// Reading 16bits data from the buffer 
// and printing it as a string 
console.log(buf.readUInt32LE(0).toString(16)); 
console.log(buf.readUInt32BE(0).toString(16)); 
console.log(buf.readUInt32LE(1).toString(16)); 
console.log(buf.readUInt32BE(1).toString(16)); 
console.log(buf.readUInt32LE(2).toString(16)); 
console.log(buf.readUInt32BE(2).toString(16)); 
console.log(buf.readUInt32LE(3).toString(16)); 
console.log(buf.readUInt32BE(3).toString(16)); 
console.log(buf.readUInt32LE(4).toString(16)); 
console.log(buf.readUInt32BE(4).toString(16)); 

Output:

<Buffer 21 09 19 98 34 ae e8 ff>
98190921
21091998
34981909
9199834
ae349819
199834ae
e8ae3498
9834aee8
ffe8ae34
34aee8ff

Example 3:

// Node program to demonstrate the   
// Buffer.readUInt32LE() Method 
   
// Allocating buffer from array 
const buf = Buffer.from([0x21, 0x09, 0x19, 0x98]); 
  
// Printing allocated buffer 
console.log(buf); 
   
// Reading 16bits data from the buffer 
// and printing it as a string 
console.log(buf.readUInt32LE(0).toString(16)); 
   
// Wrong index is provoded to produce error 
console.log(buf.readUInt32LE(1).toString(16)); 

Output:

<Buffer 21 09 19 98>
98190921
internal/buffer.js:49
  throw new ERR_OUT_OF_RANGE(type || 'offset',
  ^
RangeError [ERR_OUT_OF_RANGE]: The value of "offset" is out of range. 
It must be >= 0 and <= 0. Received 1
    at boundsError (internal/buffer.js:49:9)
    at Buffer.readUInt32LE (internal/buffer.js:105:5)
    at Object. (C:\nodejs\buf_readuint32le_2.js:10:17)
    . . .

Note: The above program will compile and run by using the node index.js command.

Reference: https://nodejs.org/api/buffer.html#buffer_buf_readuint32le_offset