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from-list.js

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'use strict';

// Read n bytes from the supplied list of buffers.

// the length is the sum of all the buffers in the list.

module.exports = fromList;

function fromList(n, list, length) {

var ret;

// nothing in the list, definitely empty.

if (list.length === 0) {

return null;

}

if (typeof length === 'undefined') {

// didn't tell us the length of the list.

// flatten and proceed from there.

var buf = Buffer.concat(list);

length = buf.length;

list.length = 0;

list.push(buf);

}

if (length === 0) {

ret = null;

} else if (!n || n >= length) {

// read it all, truncate the array.

ret = Buffer.concat(list);

list.length = 0;

} else {

// read just some of it.

if (n < list[0].length) {

// just take a part of the first list item.

var buf = list[0];

ret = buf.slice(0, n);

list[0] = buf.slice(n);

} else if (n === list[0].length) {

// first list is a perfect match

ret = list.shift();

} else {

// complex case.

// we have enough to cover it, but it spans past the first buffer.

ret = new Buffer(n);

var c = 0;

for (var i = 0, l = list.length; i < l && c < n; i++) {

var buf = list.shift();

var cpy = Math.min(n - c, buf.length);

buf.copy(ret, c, 0, cpy);

if (cpy < buf.length) {

list.unshift(buf.slice(cpy));

}

c += cpy;

}

}

}

return ret;

}