Node.js Buffer.readIntBE() Method

The Buffer.readIntBE() method is used to read the number of bytes for a buffer at a given offset and interprets the result as a two’s complement signed value.

Syntax:

buffer.readIntBE( offset, byteLen )

Parameters: This method accepts two parameters as mentioned above and described below: offset: It specifies the position of buffer object. It represents the number of bytes to skip before starting to read. The value of offset lies between the range 0 to buffer.length – byteLen.
byteLen: It is an integer value that indicates the number of bytes that are to be read from the given offset. This parameter value lies between 0 and 6.

Return value: It returns an integer value with byteLen bytes from the specified offset in big endian.

Example 1:

// Node.js program to demonstrate the
// buffer.readIntBE(offset, bytelen) method
const buff = Buffer.from([0x11, 0x12, 0x34, 0x56, 0x89, 0xcd]);

console.log(buff.readIntBE(0, 5).toString(16));

console.log(buff.readIntBE(0, 4).toString(16));

Output:

1112345689
11123456

Example 2:

// Node.js program to demonstrate the
// buffer.readIntBE(offset, bytelen) method
const buff = Buffer.from([0x11, 0x12, 0x34, 0x56, 0x89, 0xcd]);

console.log(buff.readIntBE(4, 6).toString(16));

console.log(buff.readIntBE(3, 0).toString(16));

Output:

buffer.js:831
    throw new RangeError('Index out of range');
    ^

RangeError: Index out of range
    at checkOffset (buffer.js:831:11)
    at Buffer.readIntBE (buffer.js:938:5)
    at Object. (/home/cg/root/8545664/main.js:8:17)
    at Module._compile (module.js:570:32)
    at Object.Module._extensions..js (module.js:579:10)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.runMain (module.js:604:10)
    at run (bootstrap_node.js:389:7)

The above example shows the error because its parameters are not in the valid range.

Note:

• To get the values in Little endian format you can use Buffer.readIntLE() method.
• The above program will compile and run by using the node index.js command.

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