mirror of https://github.com/facebook/rocksdb.git
82 lines
2.4 KiB
C++
82 lines
2.4 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// 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 "util/coding.h"
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#include <algorithm>
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#include "rocksdb/slice.h"
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#include "rocksdb/slice_transform.h"
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namespace rocksdb {
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char* EncodeVarint32(char* dst, uint32_t v) {
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// Operate on characters as unsigneds
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unsigned char* ptr = reinterpret_cast<unsigned char*>(dst);
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static const int B = 128;
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if (v < (1 << 7)) {
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*(ptr++) = v;
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} else if (v < (1 << 14)) {
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*(ptr++) = v | B;
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*(ptr++) = v >> 7;
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} else if (v < (1 << 21)) {
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*(ptr++) = v | B;
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*(ptr++) = (v >> 7) | B;
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*(ptr++) = v >> 14;
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} else if (v < (1 << 28)) {
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*(ptr++) = v | B;
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*(ptr++) = (v >> 7) | B;
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*(ptr++) = (v >> 14) | B;
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*(ptr++) = v >> 21;
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} else {
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*(ptr++) = v | B;
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*(ptr++) = (v >> 7) | B;
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*(ptr++) = (v >> 14) | B;
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*(ptr++) = (v >> 21) | B;
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*(ptr++) = v >> 28;
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}
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return reinterpret_cast<char*>(ptr);
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}
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const char* GetVarint32PtrFallback(const char* p, const char* limit,
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uint32_t* value) {
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uint32_t result = 0;
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for (uint32_t shift = 0; shift <= 28 && p < limit; shift += 7) {
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uint32_t byte = *(reinterpret_cast<const unsigned char*>(p));
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p++;
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if (byte & 128) {
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// More bytes are present
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result |= ((byte & 127) << shift);
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} else {
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result |= (byte << shift);
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*value = result;
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return reinterpret_cast<const char*>(p);
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}
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}
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return nullptr;
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}
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const char* GetVarint64Ptr(const char* p, const char* limit, uint64_t* value) {
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uint64_t result = 0;
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for (uint32_t shift = 0; shift <= 63 && p < limit; shift += 7) {
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uint64_t byte = *(reinterpret_cast<const unsigned char*>(p));
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p++;
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if (byte & 128) {
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// More bytes are present
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result |= ((byte & 127) << shift);
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} else {
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result |= (byte << shift);
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*value = result;
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return reinterpret_cast<const char*>(p);
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}
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}
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return nullptr;
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}
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} // namespace rocksdb
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