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.
82 lines
2.1 KiB
C++
82 lines
2.1 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 <algorithm>
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#include <stdint.h>
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#include "leveldb/comparator.h"
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#include "leveldb/slice.h"
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#include "port/port.h"
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#include "util/logging.h"
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namespace leveldb {
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Comparator::~Comparator() { }
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namespace {
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class BytewiseComparatorImpl : public Comparator {
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public:
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BytewiseComparatorImpl() { }
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virtual const char* Name() const {
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return "leveldb.BytewiseComparator";
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}
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virtual int Compare(const Slice& a, const Slice& b) const {
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return a.compare(b);
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}
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virtual void FindShortestSeparator(
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std::string* start,
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const Slice& limit) const {
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// Find length of common prefix
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size_t min_length = std::min(start->size(), limit.size());
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size_t diff_index = 0;
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while ((diff_index < min_length) &&
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((*start)[diff_index] == limit[diff_index])) {
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diff_index++;
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}
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if (diff_index >= min_length) {
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// Do not shorten if one string is a prefix of the other
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} else {
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uint8_t diff_byte = static_cast<uint8_t>((*start)[diff_index]);
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if (diff_byte < static_cast<uint8_t>(0xff) &&
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diff_byte + 1 < static_cast<uint8_t>(limit[diff_index])) {
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(*start)[diff_index]++;
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start->resize(diff_index + 1);
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assert(Compare(*start, limit) < 0);
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}
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}
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}
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virtual void FindShortSuccessor(std::string* key) const {
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// Find first character that can be incremented
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size_t n = key->size();
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for (size_t i = 0; i < n; i++) {
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const uint8_t byte = (*key)[i];
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if (byte != static_cast<uint8_t>(0xff)) {
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(*key)[i] = byte + 1;
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key->resize(i+1);
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return;
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}
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}
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// *key is a run of 0xffs. Leave it alone.
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}
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};
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} // namespace
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static port::OnceType once = LEVELDB_ONCE_INIT;
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static const Comparator* bytewise;
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static void InitModule() {
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bytewise = new BytewiseComparatorImpl;
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}
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const Comparator* BytewiseComparator() {
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port::InitOnce(&once, InitModule);
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return bytewise;
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}
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} // namespace leveldb
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