What is the writeUInt8 function in Node.js?
The writeUInt8 function in Node.js comes with the Buffer module and is used to write an 8-bit unsigned integer to a buffer at a specified offset.
Syntax
To use the writeUInt8 function, we would need a pre-allocated buffer. For this tutorial, we have named it mybuffer. The following syntax is used to use the writeUInt8 function:
mybuffer.writeUInt8(value, offset);
Parameters
The writeUInt8 function takes in up to two parameters:
value: the unsigned 8-bit integer that needs to be written to a pre-allocated buffer.offset(optional): the offset at or the number of bytes after whichvaluewill be written to in the buffer. The minimum value ofoffsetis 0, and its maximum value is one less thanthe value of mybuffer.lenwhich is the number of bytes in the buffer
If
offsetis not specified, it is assumed to be 0 by default. If the value ofoffsetis out of the prescribed range, theERR_OUT_OF_RANGEerror is thrown. Ifvalueis greater than 8 bits, the function exhibits undefined behavior.
Return value
The writeUInt8 returns the sum of the offset and the number of bytes written to the buffer upon successful execution.
Example
The program below allocates a buffer of length 5. Subsequently, it uses the writeUInt8 function to write an 8-bit unsigned integer to mybuffer at a specified offset and prints the current state of mybuffer using the console.log function.
The program fills mybuffer from 0 to 4 in reverse order and prints its final state before terminating.
mybuffer = Buffer.alloc(5);console.log(mybuffer);mybuffer.writeUInt8(0x01, 4);console.log(mybuffer);mybuffer.writeUInt8(0x02, 3);console.log(mybuffer);mybuffer.writeUInt8(0x03, 2);console.log(mybuffer);mybuffer.writeUInt8(0x04, 1);console.log(mybuffer);mybuffer.writeUInt8(0x05, 0);console.log(mybuffer);
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