The writeUIntBE function in Node.js comes with the Buffer module and is used to write an unsigned integer in the Big Endian format to a buffer at a specified offset. The maximum integer size here is 6 bytes.
In Big Endian format, the least significant bits are written last. In Little Endian format, this order is reversed. For example, the 32-bit hex number AB CD AD BD would be represented as BD AD CD AB in Little Endian format, and as AB CD AD BD in Big Endian format.
To use the writeUIntBE function, we would need a pre-allocated buffer. For this tutorial, we have named it mybuffer. The following syntax is used to use the writeUIntBE function:
mybuffer.writeUIntBE(value, offset, length);
The writeUIntBE function takes in three parameters:
value: the unsigned integer that needs to be written to a pre-allocated buffer.offset: the offset at or the number of bytes after which value will be written in the buffer. The minimum value of offset is 0, and its maximum value is the number length less than the value of mybuffer.len, which is the number of bytes in the buffer.If the value of
offsetis out of the prescribed range, theERR_OUT_OF_RANGEerror is thrown. Iflengthis greater than 6, the function exhibits undefined behavior.
length: size, in bytes, of value. Its value must be greater than 0 and smaller than or equal to 6.The writeUIntBE function returns the sum of the offset and the number of bytes written to the buffer upon successful execution.
The program below allocates a buffer that is 8 bytes long. Subsequently, it uses the writeUIntBE function to write a 2 byte and a 6 byte unsigned integer to mybuffer at specified offsets, then prints the state of mybuffer using the console.log function.
The program fills mybuffer with unsigned integers and prints its final state before terminating.
mybuffer = Buffer.alloc(8);console.log(mybuffer);mybuffer.writeUIntBE(0xabcd, 0, 2);console.log(mybuffer);mybuffer.writeUIntBE(0xdbacab125678, 2, 6);console.log(mybuffer);
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