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author | dgrogan@chromium.org <dgrogan@chromium.org@62dab493-f737-651d-591e-8d6aee1b9529> | 2011-04-19 23:11:15 +0000 |
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committer | dgrogan@chromium.org <dgrogan@chromium.org@62dab493-f737-651d-591e-8d6aee1b9529> | 2011-04-19 23:11:15 +0000 |
commit | 69c6d38342a1fab5f7f2921aa2e9c0e60ba90e35 (patch) | |
tree | bea96813c653d9e32277cb86cb517ddd90d0595c /util/comparator.cc | |
parent | b743906eeabc925f3e824d91a9747012bf249e2f (diff) | |
download | leveldb-69c6d38342a1fab5f7f2921aa2e9c0e60ba90e35.tar.gz |
reverting disastrous MOE commit, returning to r21
git-svn-id: https://leveldb.googlecode.com/svn/trunk@23 62dab493-f737-651d-591e-8d6aee1b9529
Diffstat (limited to 'util/comparator.cc')
-rw-r--r-- | util/comparator.cc | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/util/comparator.cc b/util/comparator.cc new file mode 100644 index 0000000..e2b27e3 --- /dev/null +++ b/util/comparator.cc @@ -0,0 +1,72 @@ +// Copyright (c) 2011 The LevelDB Authors. All rights reserved. +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. See the AUTHORS file for names of contributors. + +#include <stdint.h> +#include "leveldb/comparator.h" +#include "leveldb/slice.h" +#include "util/logging.h" + +namespace leveldb { + +Comparator::~Comparator() { } + +namespace { +class BytewiseComparatorImpl : public Comparator { + public: + BytewiseComparatorImpl() { } + + virtual const char* Name() const { + return "leveldb.BytewiseComparator"; + } + + virtual int Compare(const Slice& a, const Slice& b) const { + return a.compare(b); + } + + virtual void FindShortestSeparator( + std::string* start, + const Slice& limit) const { + // Find length of common prefix + size_t min_length = std::min(start->size(), limit.size()); + size_t diff_index = 0; + while ((diff_index < min_length) && + ((*start)[diff_index] == limit[diff_index])) { + diff_index++; + } + + if (diff_index >= min_length) { + // Do not shorten if one string is a prefix of the other + } else { + uint8_t diff_byte = static_cast<uint8_t>((*start)[diff_index]); + if (diff_byte < static_cast<uint8_t>(0xff) && + diff_byte + 1 < static_cast<uint8_t>(limit[diff_index])) { + (*start)[diff_index]++; + start->resize(diff_index + 1); + assert(Compare(*start, limit) < 0); + } + } + } + + virtual void FindShortSuccessor(std::string* key) const { + // Find first character that can be incremented + size_t n = key->size(); + for (int i = 0; i < n; i++) { + const uint8_t byte = (*key)[i]; + if (byte != static_cast<uint8_t>(0xff)) { + (*key)[i] = byte + 1; + key->resize(i+1); + return; + } + } + // *key is a run of 0xffs. Leave it alone. + } +}; +} +static const BytewiseComparatorImpl bytewise; + +const Comparator* BytewiseComparator() { + return &bytewise; +} + +} |