Node.js Buffer.readBigInt64BE() Method

The Buffer.readBigInt64BE() method is used to read 64-bit Big integer from a buffer object at a given offset and returns the result in Big endian.

Syntax:

buffer.readBigInt64BE( offset )

Parameters: This method accepts a single parameter offset which specifies the position of buffer object. It represents the number of bytes to skip before starting to read. The value of offset lies within the range 0 to buffer.length – 8. The default value is 0.

Return value: This method reads an signed 64-bit Big integer at the specified offset in Big endian.

Example 1: Filename: index.js

javascript

// Node.js program to demonstrate the
// buffer.readBigInt64BE() method
const buff = Buffer.from([0x00, 0x00,
    0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);

// Getting big integer value by
// using readBigInt64BE method
const value = buff.readBigInt64BE(0);

// Display the result
console.log("Big Integer :- " + value);

Run the index.js file using the following command: 

node index.js

Output:

Big Integer :- 4294967295

Example 2:
Filename: index.js

javascript

// Node.js program to demonstrate the
// buffer.readBigInt64BE() method
const buff = Buffer.from([0x00, 0x00
   , 0x01, 0x00, 0xfe, 0xff, 0xff, 0xff]);

// Getting big integer value by
// using readBigInt64BE method
const value = buff.readBigInt64BE(1);

// Display the result
console.log("Big Integer :- " + value);

Run the index.js file using the following command: 

node index.js

Output:

internal/buffer.js:77
  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:77:9)
    at Buffer.readBigInt64BE (internal/buffer.js:146:5)
    at Object. (F:\java\GFG.js:7:20)
    at Module._compile (internal/modules/cjs/loader.js:1138:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1158:10)
    at Module.load (internal/modules/cjs/loader.js:986:32)
    at Function.Module._load (internal/modules/cjs/loader.js:879:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)
    at internal/main/run_main_module.js:17:47 {
  code: 'ERR_OUT_OF_RANGE'
}

The above example shows the error because its parameters are not in the valid range.
Reference: https://nodejs.org/dist/latest-v12.x/docs/api/buffer.html#buffer_buf_readbigint64be_offset