node.js缓冲奇怪的行为

Question

I'm trying to duplicate a buffer with slice of its arraybuffer, but the result buffer contains wrong value. Here is the example:

var sourceBuf = new Buffer(1);
sourceBuf.writeUInt8(1, 0);
var slice = sourceBuf.buffer.slice(0,1);
var resultBuf = new Buffer(slice);
console.log(resultBuf.readUInt8(0));

outputs 118

In case of TypedArray all works as I at first expected:

var sourceBuf = new Uint8Array(1);
sourceBuf[0] = 1;
var slice = sourceBuf.buffer.slice(0,1);
var resultBuf = new Uint8Array(slice);
console.log(resultBuf[0]);

outputs 1

So for now I want to know what causes such "different behavior".

Answer 1

You seem to access the internal buffer and read the value. Try accessing the value like this:

var sourceBuf = new Buffer(1);
sourceBuf.writeUInt8(1, 0);
var slice = sourceBuf.slice(0,1); // Changed this line
var resultBuf = new Buffer(slice);
console.log(resultBuf.readUInt8(0));

There are two possible cases on how the error gets generated:

1. the binary value in the raw buffer gets interpreted the wrong way
2. robertKlep suggests that the buffer -property is uninitialized internally

In either way, accessing that property seemed to be the error.