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// 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 "leveldb/filter_policy.h"
#include "util/coding.h"
#include "util/logging.h"
#include "util/testharness.h"
#include "util/testutil.h"
namespace leveldb {
static const int kVerbose = 1;
static Slice Key(int i, char* buffer) {
EncodeFixed32(buffer, i);
return Slice(buffer, sizeof(uint32_t));
}
class BloomTest {
public:
BloomTest() : policy_(NewBloomFilterPolicy(10)) {}
~BloomTest() { delete policy_; }
void Reset() {
keys_.clear();
filter_.clear();
}
void Add(const Slice& s) { keys_.push_back(s.ToString()); }
void Build() {
std::vector<Slice> key_slices;
for (size_t i = 0; i < keys_.size(); i++) {
key_slices.push_back(Slice(keys_[i]));
}
filter_.clear();
policy_->CreateFilter(&key_slices[0], static_cast<int>(key_slices.size()),
&filter_);
keys_.clear();
if (kVerbose >= 2) DumpFilter();
}
size_t FilterSize() const { return filter_.size(); }
void DumpFilter() {
fprintf(stderr, "F(");
for (size_t i = 0; i + 1 < filter_.size(); i++) {
const unsigned int c = static_cast<unsigned int>(filter_[i]);
for (int j = 0; j < 8; j++) {
fprintf(stderr, "%c", (c & (1 << j)) ? '1' : '.');
}
}
fprintf(stderr, ")\n");
}
bool Matches(const Slice& s) {
if (!keys_.empty()) {
Build();
}
return policy_->KeyMayMatch(s, filter_);
}
double FalsePositiveRate() {
char buffer[sizeof(int)];
int result = 0;
for (int i = 0; i < 10000; i++) {
if (Matches(Key(i + 1000000000, buffer))) {
result++;
}
}
return result / 10000.0;
}
private:
const FilterPolicy* policy_;
std::string filter_;
std::vector<std::string> keys_;
};
TEST(BloomTest, EmptyFilter) {
ASSERT_TRUE(!Matches("hello"));
ASSERT_TRUE(!Matches("world"));
}
TEST(BloomTest, Small) {
Add("hello");
Add("world");
ASSERT_TRUE(Matches("hello"));
ASSERT_TRUE(Matches("world"));
ASSERT_TRUE(!Matches("x"));
ASSERT_TRUE(!Matches("foo"));
}
static int NextLength(int length) {
if (length < 10) {
length += 1;
} else if (length < 100) {
length += 10;
} else if (length < 1000) {
length += 100;
} else {
length += 1000;
}
return length;
}
TEST(BloomTest, VaryingLengths) {
char buffer[sizeof(int)];
// Count number of filters that significantly exceed the false positive rate
int mediocre_filters = 0;
int good_filters = 0;
for (int length = 1; length <= 10000; length = NextLength(length)) {
Reset();
for (int i = 0; i < length; i++) {
Add(Key(i, buffer));
}
Build();
ASSERT_LE(FilterSize(), static_cast<size_t>((length * 10 / 8) + 40))
<< length;
// All added keys must match
for (int i = 0; i < length; i++) {
ASSERT_TRUE(Matches(Key(i, buffer)))
<< "Length " << length << "; key " << i;
}
// Check false positive rate
double rate = FalsePositiveRate();
if (kVerbose >= 1) {
fprintf(stderr, "False positives: %5.2f%% @ length = %6d ; bytes = %6d\n",
rate * 100.0, length, static_cast<int>(FilterSize()));
}
ASSERT_LE(rate, 0.02); // Must not be over 2%
if (rate > 0.0125)
mediocre_filters++; // Allowed, but not too often
else
good_filters++;
}
if (kVerbose >= 1) {
fprintf(stderr, "Filters: %d good, %d mediocre\n", good_filters,
mediocre_filters);
}
ASSERT_LE(mediocre_filters, good_filters / 5);
}
// Different bits-per-byte
} // namespace leveldb
int main(int argc, char** argv) { return leveldb::test::RunAllTests(); }
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