50e77a8263
The create function took |num_keys| as an int, but callers and implementers wanted it to function as a size_t (e.g. passing std::vector::size() in, passing it to vector constructors as a size arg, indexing containers by it, etc.). This resulted in implicit conversions between the two types as well as warnings (found with Chromium's external copy of these sources, built with MSVC) about signed vs. unsigned comparisons. The leveldb sources were already widely using size_t elsewhere, e.g. for key and filter lengths, so using size_t here is not inconsistent with the existing code. However, it does change the public C API. ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=101074871
112 lines
3.3 KiB
C++
112 lines
3.3 KiB
C++
// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include "table/filter_block.h"
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#include "leveldb/filter_policy.h"
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#include "util/coding.h"
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namespace leveldb {
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// See doc/table_format.txt for an explanation of the filter block format.
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// Generate new filter every 2KB of data
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static const size_t kFilterBaseLg = 11;
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static const size_t kFilterBase = 1 << kFilterBaseLg;
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FilterBlockBuilder::FilterBlockBuilder(const FilterPolicy* policy)
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: policy_(policy) {
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}
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void FilterBlockBuilder::StartBlock(uint64_t block_offset) {
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uint64_t filter_index = (block_offset / kFilterBase);
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assert(filter_index >= filter_offsets_.size());
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while (filter_index > filter_offsets_.size()) {
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GenerateFilter();
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}
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}
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void FilterBlockBuilder::AddKey(const Slice& key) {
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Slice k = key;
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start_.push_back(keys_.size());
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keys_.append(k.data(), k.size());
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}
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Slice FilterBlockBuilder::Finish() {
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if (!start_.empty()) {
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GenerateFilter();
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}
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// Append array of per-filter offsets
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const uint32_t array_offset = result_.size();
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for (size_t i = 0; i < filter_offsets_.size(); i++) {
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PutFixed32(&result_, filter_offsets_[i]);
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}
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PutFixed32(&result_, array_offset);
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result_.push_back(kFilterBaseLg); // Save encoding parameter in result
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return Slice(result_);
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}
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void FilterBlockBuilder::GenerateFilter() {
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const size_t num_keys = start_.size();
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if (num_keys == 0) {
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// Fast path if there are no keys for this filter
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filter_offsets_.push_back(result_.size());
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return;
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}
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// Make list of keys from flattened key structure
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start_.push_back(keys_.size()); // Simplify length computation
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tmp_keys_.resize(num_keys);
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for (size_t i = 0; i < num_keys; i++) {
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const char* base = keys_.data() + start_[i];
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size_t length = start_[i+1] - start_[i];
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tmp_keys_[i] = Slice(base, length);
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}
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// Generate filter for current set of keys and append to result_.
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filter_offsets_.push_back(result_.size());
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policy_->CreateFilter(&tmp_keys_[0], static_cast<int>(num_keys), &result_);
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tmp_keys_.clear();
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keys_.clear();
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start_.clear();
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}
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FilterBlockReader::FilterBlockReader(const FilterPolicy* policy,
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const Slice& contents)
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: policy_(policy),
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data_(NULL),
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offset_(NULL),
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num_(0),
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base_lg_(0) {
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size_t n = contents.size();
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if (n < 5) return; // 1 byte for base_lg_ and 4 for start of offset array
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base_lg_ = contents[n-1];
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uint32_t last_word = DecodeFixed32(contents.data() + n - 5);
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if (last_word > n - 5) return;
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data_ = contents.data();
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offset_ = data_ + last_word;
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num_ = (n - 5 - last_word) / 4;
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}
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bool FilterBlockReader::KeyMayMatch(uint64_t block_offset, const Slice& key) {
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uint64_t index = block_offset >> base_lg_;
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if (index < num_) {
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uint32_t start = DecodeFixed32(offset_ + index*4);
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uint32_t limit = DecodeFixed32(offset_ + index*4 + 4);
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if (start <= limit && limit <= static_cast<size_t>(offset_ - data_)) {
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Slice filter = Slice(data_ + start, limit - start);
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return policy_->KeyMayMatch(key, filter);
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} else if (start == limit) {
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// Empty filters do not match any keys
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return false;
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}
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}
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return true; // Errors are treated as potential matches
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}
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}
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