1
2/*
3 * Copyright 2011 Google Inc.
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10#ifndef GrBinHashKey_DEFINED
11#define GrBinHashKey_DEFINED
12
13#include "GrTypes.h"
14
15/**
16 *  GrBinHashKey is a hash key class that can take a data chunk of any predetermined
17 *  length. The hash function used is the One-at-a-Time Hash
18 *  (http://burtleburtle.net/bob/hash/doobs.html).
19 */
20template<size_t KEY_SIZE>
21class GrBinHashKey {
22public:
23    enum { kKeySize = KEY_SIZE };
24
25    GrBinHashKey() {
26        this->reset();
27    }
28
29    void reset() {
30        fHash = 0;
31#ifdef SK_DEBUG
32        fIsValid = false;
33#endif
34    }
35
36    void setKeyData(const uint32_t* SK_RESTRICT data) {
37        SK_COMPILE_ASSERT(KEY_SIZE % 4 == 0, key_size_mismatch);
38        memcpy(&fData, data, KEY_SIZE);
39
40        uint32_t hash = 0;
41        size_t len = KEY_SIZE;
42        while (len >= 4) {
43            hash += *data++;
44            hash += (hash << 10);
45            hash ^= (hash >> 6);
46            len -= 4;
47        }
48        hash += (hash << 3);
49        hash ^= (hash >> 11);
50        hash += (hash << 15);
51#ifdef SK_DEBUG
52        fIsValid = true;
53#endif
54        fHash = hash;
55    }
56
57    bool operator==(const GrBinHashKey<KEY_SIZE>& key) const {
58        SkASSERT(fIsValid && key.fIsValid);
59        if (fHash != key.fHash) {
60            return false;
61        }
62        for (size_t i = 0; i < SK_ARRAY_COUNT(fData); ++i) {
63            if (fData[i] != key.fData[i]) {
64                return false;
65            }
66        }
67        return true;
68    }
69
70    bool operator<(const GrBinHashKey<KEY_SIZE>& key) const {
71        SkASSERT(fIsValid && key.fIsValid);
72        for (size_t i = 0; i < SK_ARRAY_COUNT(fData); ++i) {
73            if (fData[i] < key.fData[i]) {
74                return true;
75            } else if (fData[i] > key.fData[i]) {
76                return false;
77            }
78        }
79        return false;
80    }
81
82    uint32_t getHash() const {
83        SkASSERT(fIsValid);
84        return fHash;
85    }
86
87    const uint8_t* getData() const {
88        SkASSERT(fIsValid);
89        return reinterpret_cast<const uint8_t*>(fData);
90    }
91
92private:
93    uint32_t            fHash;
94    uint32_t            fData[KEY_SIZE / sizeof(uint32_t)];  // Buffer for key storage.
95
96#ifdef SK_DEBUG
97public:
98    bool                fIsValid;
99#endif
100};
101
102#endif
103