Node.js Buffer.readUIntBE() Method

The Buffer.readUIntBE() method is an inbuilt application programming interface of class Buffer within the Buffer module which is used to read specified number of byte(s) value from an allocated buffer at a specified offset.

Syntax:

Buffer.readUIntBE( offset, byteLength )

Parameters: This method accept two parameters as mentioned above and described below:

• offset: It 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 – byteLength. Its default value is 0.
• byteLength: It specifies the number of bytes to be read. The value of byteLength loes 0 < byteLength <= 6.

Return: This method returns an integer value that read from buffer in Big Endian format.

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

Example 1:

// Node program to demonstrate the
// Buffer.readUIntBE() Method

// Allocating buffer from array
const buf = Buffer.from([0x21, 0x09, 0x19, 0x98]);

// Printing allocated buffer
console.log(buf);

// Reading  data from the buffer
// and printing it as a string
console.log(buf.readUIntBE(0, 3).toString(16));
console.log(buf.readUIntBE(1, 3).toString(16));
console.log(buf.readUIntBE(2, 2).toString(16));

Output:

<Buffer 21 09 19 98>
210919
91998
1998

Example 2:

// Node program to demonstrate the
// Buffer.readUIntBE() Method

// Allocating buffer from array
const buf = Buffer.from([0x21, 0x09, 0x19, 0x98]);

// Printing allocated buffer
console.log(buf);

// Reading data from the buffer
// and printing it as a string
console.log(buf.readUIntBE(0, 3).toString(16));
console.log(buf.readUIntLE(0, 3).toString(16));
console.log(buf.readUIntBE(1, 2).toString(16));
console.log(buf.readUIntLE(1, 2).toString(16));
console.log(buf.readUIntBE(2, 1).toString(16));
console.log(buf.readUIntLE(2, 1).toString(16));

Output:

<Buffer 21 09 19 98>
210919
190921
919
1909
19
19

Example 3:

// Node program to demonstrate the
// Buffer.readUIntBE() Method

// Allocating buffer from array
const buf = Buffer.from([0x21, 0x09, 0x19, 0x98]);

// Printing allocated buffer
console.log(buf);

// Reading data from the buffer
// and printing it as a string
console.log(buf.readUIntBE(0, 4).toString(16));
console.log(buf.readUIntBE(1, 2).toString(16));
console.log(buf.readUIntBE(2, 3).toString(16));

// Wrong index is provoded to produce error
console.log(buf.readUIntBE(3, 6).toString(16));

Output:

<Buffer 21 09 19 98>
21091998
919
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 <= 1. Received 2
    at boundsError (internal/buffer.js:49:9)
    at readUInt24BE (internal/buffer.js:205:5)
    at Buffer.readUIntBE (internal/buffer.js:148:12)
    . . . 

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

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