tomFlowee
c63519fa47
The leveldb and univalue 3rd party libraries are not installed and not needed by anyone outside of the Hub. So move them there, making it easier for 3rd party usage.
53 lines
1.3 KiB
C++
53 lines
1.3 KiB
C++
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include <string.h>
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#include "util/coding.h"
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#include "util/hash.h"
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// The FALLTHROUGH_INTENDED macro can be used to annotate implicit fall-through
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// between switch labels. The real definition should be provided externally.
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// This one is a fallback version for unsupported compilers.
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#ifndef FALLTHROUGH_INTENDED
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#define FALLTHROUGH_INTENDED do { } while (0)
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#endif
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namespace leveldb {
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uint32_t Hash(const char* data, size_t n, uint32_t seed) {
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// Similar to murmur hash
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const uint32_t m = 0xc6a4a793;
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const uint32_t r = 24;
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const char* limit = data + n;
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uint32_t h = seed ^ (n * m);
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// Pick up four bytes at a time
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while (data + 4 <= limit) {
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uint32_t w = DecodeFixed32(data);
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data += 4;
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h += w;
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h *= m;
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h ^= (h >> 16);
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}
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// Pick up remaining bytes
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switch (limit - data) {
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case 3:
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h += static_cast<unsigned char>(data[2]) << 16;
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FALLTHROUGH_INTENDED;
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case 2:
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h += static_cast<unsigned char>(data[1]) << 8;
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FALLTHROUGH_INTENDED;
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case 1:
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h += static_cast<unsigned char>(data[0]);
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h *= m;
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h ^= (h >> r);
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break;
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}
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return h;
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}
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} // namespace leveldb
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