text: ﻿// 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 "table/filter_block.h"
  
  #include "leveldb/filter_policy.h"
  #include "util/coding.h"
  #include "util/hash.h"
  #include "util/logging.h"
  #include "util/testharness.h"
  #include "util/testutil.h"
  
  namespace leveldb {
  
  // For testing: emit an array with one hash value per key
  class TestHashFilter : public FilterPolicy {
   public:
    virtual const char* Name() const {
      return "TestHashFilter";
    }
  
    virtual void CreateFilter(const Slice* keys, int n, std::string* dst) const {
      for (int i = 0; i < n; i++) {
        uint32_t h = Hash(keys[i].data(), keys[i].size(), 1);
        PutFixed32(dst, h);
      }
    }
  
    virtual bool KeyMayMatch(const Slice& key, const Slice& filter) const {
      uint32_t h = Hash(key.data(), key.size(), 1);
      for (int i = 0; i + 4 <= filter.size(); i += 4) {
        if (h == DecodeFixed32(filter.data() + i)) {
          return true;
        }
      }
      return false;
    }
  };
  
  class FilterBlockTest {
   public:
    TestHashFilter policy_;
  };
  
  TEST(FilterBlockTest, EmptyBuilder) {
    FilterBlockBuilder builder(&policy_);
    Slice block = builder.Finish();
    ASSERT_EQ("\\x00\\x00\\x00\\x00\\x0b", EscapeString(block));
    FilterBlockReader reader(&policy_, block);
    ASSERT_TRUE(reader.KeyMayMatch(0, "foo"));
    ASSERT_TRUE(reader.KeyMayMatch(100000, "foo"));
  }
  
  TEST(FilterBlockTest, SingleChunk) {
    FilterBlockBuilder builder(&policy_);
    builder.StartBlock(100);
    builder.AddKey("foo");
    builder.AddKey("bar");
    builder.AddKey("box");
    builder.StartBlock(200);
    builder.AddKey("box");
    builder.StartBlock(300);
    builder.AddKey("hello");
    Slice block = builder.Finish();
    FilterBlockReader reader(&policy_, block);
    ASSERT_TRUE(reader.KeyMayMatch(100, "foo"));
    ASSERT_TRUE(reader.KeyMayMatch(100, "bar"));
    ASSERT_TRUE(reader.KeyMayMatch(100, "box"));
    ASSERT_TRUE(reader.KeyMayMatch(100, "hello"));
    ASSERT_TRUE(reader.KeyMayMatch(100, "foo"));
    ASSERT_TRUE(! reader.KeyMayMatch(100, "missing"));
    ASSERT_TRUE(! reader.KeyMayMatch(100, "other"));
  }
  
  TEST(FilterBlockTest, MultiChunk) {
    FilterBlockBuilder builder(&policy_);
  
    // First filter
    builder.StartBlock(0);
    builder.AddKey("foo");
    builder.StartBlock(2000);
    builder.AddKey("bar");
  
    // Second filter
    builder.StartBlock(3100);
    builder.AddKey("box");
  
    // Third filter is empty
  
    // Last filter
    builder.StartBlock(9000);
    builder.AddKey("box");
    builder.AddKey("hello");
  
    Slice block = builder.Finish();
    FilterBlockReader reader(&policy_, block);
  
    // Check first filter
    ASSERT_TRUE(reader.KeyMayMatch(0, "foo"));
    ASSERT_TRUE(reader.KeyMayMatch(2000, "bar"));
    ASSERT_TRUE(! reader.KeyMayMatch(0, "box"));
    ASSERT_TRUE(! reader.KeyMayMatch(0, "hello"));
  
    // Check second filter
    ASSERT_TRUE(reader.KeyMayMatch(3100, "box"));
    ASSERT_TRUE(! reader.KeyMayMatch(3100, "foo"));
    ASSERT_TRUE(! reader.KeyMayMatch(3100, "bar"));
    ASSERT_TRUE(! reader.KeyMayMatch(3100, "hello"));
  
    // Check third filter (empty)
    ASSERT_TRUE(! reader.KeyMayMatch(4100, "foo"));
    ASSERT_TRUE(! reader.KeyMayMatch(4100, "bar"));
    ASSERT_TRUE(! reader.KeyMayMatch(4100, "box"));
    ASSERT_TRUE(! reader.KeyMayMatch(4100, "hello"));
  
    // Check last filter
    ASSERT_TRUE(reader.KeyMayMatch(9000, "box"));
    ASSERT_TRUE(reader.KeyMayMatch(9000, "hello"));
    ASSERT_TRUE(! reader.KeyMayMatch(9000, "foo"));
    ASSERT_TRUE(! reader.KeyMayMatch(9000, "bar"));
  }
  
  }  // namespace leveldb
  
  int main(int argc, char** argv) {
    return leveldb::test::RunAllTests();
  }
  