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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MEDIA_BASE_DJB2_H_
#define MEDIA_BASE_DJB2_H_
#include <stddef.h>
#include <stdint.h>
#include "media/base/media_export.h"
// DJB2 is a hash algorithm with excellent distribution and speed
// on many different sets.
// It has marginally more collisions than FNV1, but makes up for it in
// performance.
// The return value is suitable for table lookups.
// For small fixed sizes (ie a pixel), it has low overhead and inlines well.
// For large data sets, it optimizes into assembly/simd and is appropriate
// for realtime applications.
// See Also:
// http://www.cse.yorku.ca/~oz/hash.html
static const uint32_t kDJB2HashSeed = 5381u;
// These functions perform DJB2 hash. The simplest call is DJB2Hash() to
// generate the DJB2 hash of the given data:
// uint32_t hash = DJB2Hash(data1, length1, kDJB2HashSeed);
//
// You can also compute the DJB2 hash of data incrementally by making multiple
// calls to DJB2Hash():
// uint32_t hash_value = kDJB2HashSeed; // Initial seed for DJB2.
// for (size_t i = 0; i < copy_lines; ++i) {
// hash_value = DJB2Hash(source, bytes_per_line, hash_value);
// source += source_stride;
// }
// For the given buffer of data, compute the DJB2 hash of
// the data. You can call this any number of times during the computation.
MEDIA_EXPORT uint32_t DJB2Hash(const void* buf, size_t len, uint32_t seed);
#endif // MEDIA_BASE_DJB2_H_
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