gecko-dev/mfbt/HashFunctions.cpp
Justin Lebar f584e08122 Bug 729940 - Part 1: Add hash function utilities to mfbt. r=waldo
--HG--
extra : rebase_source : 05f5c9f5c1e99e5bca012c57502a965423aeb10e
2012-03-12 18:53:18 -04:00

73 lines
2.5 KiB
C++

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sw=4 et tw=99 ft=cpp:
*
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at:
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla Code.
*
* The Initial Developer of the Original Code is
* The Mozilla Foundation
* Portions created by the Initial Developer are Copyright (C) 2011
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Justin Lebar <justin.lebar@gmail.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
/* Implementations of hash functions */
#include "mozilla/HashFunctions.h"
#include <string.h>
namespace mozilla {
MFBT_API(uint32_t)
HashBytes(const void* bytes, size_t length)
{
uint32_t hash = 0;
const char* b = reinterpret_cast<const char*>(bytes);
/* Walk word by word. */
size_t i = 0;
for (; i < length - (length % sizeof(size_t)); i += sizeof(size_t)) {
/* Do an explicitly unaligned load of the data. */
size_t data;
memcpy(&data, b + i, sizeof(size_t));
hash = AddToHash(hash, data, sizeof(data));
}
/* Get the remaining bytes. */
for (; i < length; i++) {
hash = AddToHash(hash, b[i]);
}
return hash;
}
} /* namespace mozilla */