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Add Buffer.concat method
We write out this loop a lot of places throughout node.
It clearly needs to be an API method.
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isaacs committed Jun 11, 2012
1 parent cfa2869 commit d53cdc5
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20 changes: 20 additions & 0 deletions doc/api/buffer.markdown
Expand Up @@ -148,6 +148,26 @@ Example:

// ½ + ¼ = ¾: 9 characters, 12 bytes

### Class Method: Buffer.concat(list, [totalLength])

* `list` {Array} List of Buffer objects to concat
* `totalLength` {Number} Total length of the buffers when concatenated

Returns a buffer which is the result of concatenating all the buffers in
the list together.

If the list has no items, or if the totalLength is 0, then it returns a
zero-length buffer.

If the list has exactly one item, then the first item of the list is
returned.

If the list has more than one item, then a new Buffer is created.

If totalLength is not provided, it is read from the buffers in the list.
However, this adds an additional loop to the function, so it is faster
to provide the length explicitly.

### buf.length

* Number
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32 changes: 32 additions & 0 deletions lib/buffer.js
Expand Up @@ -469,6 +469,38 @@ Buffer.prototype.fill = function fill(value, start, end) {
};


Buffer.concat = function(list, length) {
if (!Array.isArray(list)) {
throw new Error('Usage: Buffer.concat(list, [length])');
}

if (list.length === 0) {
return new Buffer(0);
} else if (list.length === 1) {
return list[0];
}

if (typeof length !== 'number') {
length = 0;
for (var i = 0; i < list.length; i++) {
var buf = list[i];
length += buf.length;
}
}

var buffer = new Buffer(length);
var pos = 0;
for (var i = 0; i < list.length; i++) {
var buf = list[i];
buf.copy(buffer, pos);
pos += buf.length;
}
return buffer;
};




// copy(targetBuffer, targetStart=0, sourceStart=0, sourceEnd=buffer.length)
Buffer.prototype.copy = function(target, target_start, start, end) {
var source = this;
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41 changes: 41 additions & 0 deletions test/simple/test-buffer-concat.js
@@ -0,0 +1,41 @@
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

var common = require('../common');
var assert = require('assert');

var zero = [];
var one = [ new Buffer('asdf') ];
var long = [];
for (var i = 0; i < 10; i++) long.push(new Buffer('asdf'));

var flatZero = Buffer.concat(zero);
var flatOne = Buffer.concat(one);
var flatLong = Buffer.concat(long);
var flatLongLen = Buffer.concat(long, 40);

assert(flatZero.length === 0);
assert(flatOne.toString() === 'asdf');
assert(flatOne === one[0]);
assert(flatLong.toString() === (new Array(10+1).join('asdf')));
assert(flatLongLen.toString() === (new Array(10+1).join('asdf')));

console.log("ok");

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