text: //  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"
  
  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." + std::to_string(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_);
    }
  };
  
  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;
    }
  };
  
  }
  
  const SliceTransform* NewFixedPrefixTransform(size_t prefix_len) {
    return new FixedPrefixTransform(prefix_len);
  }
  
  const SliceTransform* NewNoopTransform() {
    return new NoopTransform;
  }
  
  }  // namespace rocksdb
  