chromium/third_party/leveldatabase/src/table/block_builder.cc

// 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.
//
// BlockBuilder generates blocks where keys are prefix-compressed:
//
// When we store a key, we drop the prefix shared with the previous
// string.  This helps reduce the space requirement significantly.
// Furthermore, once every K keys, we do not apply the prefix
// compression and store the entire key.  We call this a "restart
// point".  The tail end of the block stores the offsets of all of the
// restart points, and can be used to do a binary search when looking
// for a particular key.  Values are stored as-is (without compression)
// immediately following the corresponding key.
//
// An entry for a particular key-value pair has the form:
//     shared_bytes: varint32
//     unshared_bytes: varint32
//     value_length: varint32
//     key_delta: char[unshared_bytes]
//     value: char[value_length]
// shared_bytes == 0 for restart points.
//
// The trailer of the block has the form:
//     restarts: uint32[num_restarts]
//     num_restarts: uint32
// restarts[i] contains the offset within the block of the ith restart point.

#include "table/block_builder.h"

#include <algorithm>
#include <cassert>

#include "leveldb/comparator.h"
#include "leveldb/options.h"
#include "util/coding.h"

namespace leveldb {

BlockBuilder::BlockBuilder(const Options* options)
    : … { … }

void BlockBuilder::Reset() { … }

size_t BlockBuilder::CurrentSizeEstimate() const { … }

Slice BlockBuilder::Finish() { … }

void BlockBuilder::Add(const Slice& key, const Slice& value) { … }

}  // namespace leveldb