rocksdb/util/slice.cc

//  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 override { return name_.c_str(); }

  virtual Slice Transform(const Slice& src) const override {
    assert(InDomain(src));
    return Slice(src.data(), prefix_len_);
  }

  virtual bool InDomain(const Slice& src) const override {
    return (src.size() >= prefix_len_);
  }

  virtual bool InRange(const Slice& dst) const override {
    return (dst.size() == prefix_len_);
  }

  virtual bool SameResultWhenAppended(const Slice& prefix) const override {
    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 override { return name_.c_str(); }

  virtual Slice Transform(const Slice& src) const override {
    assert(InDomain(src));
    return Slice(src.data(), std::min(cap_len_, src.size()));
  }

  virtual bool InDomain(const Slice& src) const override { return true; }

  virtual bool InRange(const Slice& dst) const override {
    return (dst.size() <= cap_len_);
  }

  virtual bool SameResultWhenAppended(const Slice& prefix) const override {
    return prefix.size() >= cap_len_;
  }
};

class NoopTransform : public SliceTransform {
 public:
  explicit NoopTransform() { }

  virtual const char* Name() const override { return "rocksdb.Noop"; }

  virtual Slice Transform(const Slice& src) const override { return src; }

  virtual bool InDomain(const Slice& src) const override { return true; }

  virtual bool InRange(const Slice& dst) const override { return true; }

  virtual bool SameResultWhenAppended(const Slice& prefix) const override {
    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