src/gpu/GrBinHashKey.h

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */


#ifndef GrBinHashKey_DEFINED
#define GrBinHashKey_DEFINED

#include "GrTypes.h"

/**
 *  GrBinHashKey is a hash key class that can take a data chunk of any predetermined
 *  length. The hash function used is the One-at-a-Time Hash
 *  (http://burtleburtle.net/bob/hash/doobs.html).
 */
template<size_t KEY_SIZE>
class GrBinHashKey {
public:
    enum { kKeySize = KEY_SIZE };

    GrBinHashKey() {
        this->reset();
    }

    void reset() {
        fHash = 0;
#ifdef SK_DEBUG
        fIsValid = false;
#endif
    }

    void setKeyData(const uint32_t* SK_RESTRICT data) {
        SK_COMPILE_ASSERT(KEY_SIZE % 4 == 0, key_size_mismatch);
        memcpy(&fData, data, KEY_SIZE);

        uint32_t hash = 0;
        size_t len = KEY_SIZE;
        while (len >= 4) {
            hash += *data++;
            hash += (hash << 10);
            hash ^= (hash >> 6);
            len -= 4;
        }
        hash += (hash << 3);
        hash ^= (hash >> 11);
        hash += (hash << 15);
#ifdef SK_DEBUG
        fIsValid = true;
#endif
        fHash = hash;
    }

    bool operator==(const GrBinHashKey<KEY_SIZE>& key) const {
        SkASSERT(fIsValid && key.fIsValid);
        if (fHash != key.fHash) {
            return false;
        }
        for (size_t i = 0; i < SK_ARRAY_COUNT(fData); ++i) {
            if (fData[i] != key.fData[i]) {
                return false;
            }
        }
        return true;
    }

    bool operator<(const GrBinHashKey<KEY_SIZE>& key) const {
        SkASSERT(fIsValid && key.fIsValid);
        for (size_t i = 0; i < SK_ARRAY_COUNT(fData); ++i) {
            if (fData[i] < key.fData[i]) {
                return true;
            } else if (fData[i] > key.fData[i]) {
                return false;
            }
        }
        return false;
    }

    uint32_t getHash() const {
        SkASSERT(fIsValid);
        return fHash;
    }

    const uint8_t* getData() const {
        SkASSERT(fIsValid);
        return reinterpret_cast<const uint8_t*>(fData);
    }

private:
    uint32_t            fHash;
    uint32_t            fData[KEY_SIZE / sizeof(uint32_t)];  // Buffer for key storage.

#ifdef SK_DEBUG
public:
    bool                fIsValid;
#endif
};

#endif