rocksdb/util/slice.cc
sdong 5917de0bae CappedFixTransform: return fixed length prefix, or full key if key is shorter than the fixed length
Summary: Add CappedFixTransform, which is the same as fixed length prefix extractor, except that when slice is shorter than the fixed length, it will use the full key.

Test Plan:
Add a test case for
db_test
options_test
and a new test

Reviewers: yhchiang, rven, igor

Reviewed By: igor

Subscribers: MarkCallaghan, leveldb, dhruba, yoshinorim

Differential Revision: https://reviews.facebook.net/D31887
2015-01-30 16:04:30 -08:00

116 lines
2.8 KiB
C++

// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2012 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 "rocksdb/slice_transform.h"
#include "rocksdb/slice.h"
#include "util/string_util.h"
namespace rocksdb {
namespace {
class FixedPrefixTransform : public SliceTransform {
private:
size_t prefix_len_;
std::string name_;
public:
explicit FixedPrefixTransform(size_t prefix_len)
: prefix_len_(prefix_len),
name_("rocksdb.FixedPrefix." + ToString(prefix_len_)) {}
virtual const char* Name() const { return name_.c_str(); }
virtual Slice Transform(const Slice& src) const {
assert(InDomain(src));
return Slice(src.data(), prefix_len_);
}
virtual bool InDomain(const Slice& src) const {
return (src.size() >= prefix_len_);
}
virtual bool InRange(const Slice& dst) const {
return (dst.size() == prefix_len_);
}
virtual bool SameResultWhenAppended(const Slice& prefix) const {
return InDomain(prefix);
}
};
class CappedPrefixTransform : public SliceTransform {
private:
size_t cap_len_;
std::string name_;
public:
explicit CappedPrefixTransform(size_t cap_len)
: cap_len_(cap_len),
name_("rocksdb.CappedPrefix." + ToString(cap_len_)) {}
virtual const char* Name() const { return name_.c_str(); }
virtual Slice Transform(const Slice& src) const {
assert(InDomain(src));
return Slice(src.data(), std::min(cap_len_, src.size()));
}
virtual bool InDomain(const Slice& src) const { return true; }
virtual bool InRange(const Slice& dst) const {
return (dst.size() <= cap_len_);
}
virtual bool SameResultWhenAppended(const Slice& prefix) const {
return prefix.size() >= cap_len_;
}
};
class NoopTransform : public SliceTransform {
public:
explicit NoopTransform() { }
virtual const char* Name() const {
return "rocksdb.Noop";
}
virtual Slice Transform(const Slice& src) const {
return src;
}
virtual bool InDomain(const Slice& src) const {
return true;
}
virtual bool InRange(const Slice& dst) const {
return true;
}
virtual bool SameResultWhenAppended(const Slice& prefix) const {
return false;
}
};
}
const SliceTransform* NewFixedPrefixTransform(size_t prefix_len) {
return new FixedPrefixTransform(prefix_len);
}
const SliceTransform* NewCappedPrefixTransform(size_t cap_len) {
return new CappedPrefixTransform(cap_len);
}
const SliceTransform* NewNoopTransform() {
return new NoopTransform;
}
} // namespace rocksdb