Merge #17398: build: Update leveldb to 1.22+

677fb8e92380d4deb6a3753047c01f7cf7b5af91 test: Add ubsan surpression for crc32c (Wladimir J. van der Laan)
8e68bb1ddeca504bedd40aee8492b5478a88c1e5 build: Disable msvc warning 4722 for leveldb build (Aaron Clauson)
be23949765e1b2e050574c6c2a136658a89dee5d build: MSVC changes for leveldb update (Aaron Clauson)
9ebdf047578f0da7e6578d0c51c32f55e84ac157 build: CRC32C build system integration (Wladimir J. van der Laan)
402252a8081e25f22aa1a5c60708714cf1d84ec4 build: Add LCOV exception for crc32c (Wladimir J. van der Laan)
3a037d0067c2c12a1c2c800fb85613a0a2911253 test: Add crc32c exception to various linters and generation scripts (Wladimir J. van der Laan)
84ff1b2076ef91ce688930d0aa0a7f4078ef3e1d test: Add crc32c to subtree check linter (Wladimir J. van der Laan)
7cf13a513409c18d18dff2f6203b3630937b487d doc: Add crc32c subtree to developer notes (Wladimir J. van der Laan)
24d02a9ac00a82d172b171f73554a882df264c80 build: Update build system for new leveldb (Wladimir J. van der Laan)
2e1819311a59fb5cb26e3ca50a510bfe01358350 Squashed 'src/crc32c/' content from commit 224988680f7673cd7c769963d4035cb315aa3388 (Wladimir J. van der Laan)
66480821b36c839ab7615cb9309850015bceadb0 Squashed 'src/leveldb/' changes from f545dfabff4c2e9836efed094dba99a34fbc6b88..f8ae182c1e5176d12e816fb2217ae33a5472fdd7 (Wladimir J. van der Laan)

Pull request description:

  This updates leveldb to currently newest upstream commit https://github.com/bitcoin-core/leveldb/commit/0c40829872a9f00f38e11dc370ff8adb3e19f25b:

  - CRC32C hardware acceleration is now an external library [crc32c](https://github.com/google/crc32c). This adds acceleration on ARM, and should be faster on x86 because of using prefetch. It also makes it easy to support similar instruction sets on other platforms in the future.
  - Thread handling uses C++11, instead of platform specific code.
  - Native windows environment was added. No need to maintain our own hacky one, anymore.
  - Upstream now builds using CMake. This doesn't mean we need to use that (phew), but internal configuration changed to a a series of checks, instead of OS profiles. This means the blanket error "Cannot build leveldb for $host. Please file a bug report' is removed.

  All changes: https://github.com/google/leveldb/compare/a53934a3ae1244679f812d998a4f16f2c7f309a6...0c40829872a9f00f38e11dc370ff8adb3e19f25b

  Pretty much all our changes have been subsumed by upstream, so we figured it was cleaner to start over with a new branch from upstream with the still-relevant patches applied: https://github.com/bitcoin-core/leveldb/tree/bitcoin-fork-new

  There's quite some testing to be done (see below). See https://github.com/bitcoin-core/leveldb/issues/25 and https://github.com/bitcoin-core/leveldb/pull/26 for more history and context.

  TODO:
  - [x] Subtree `crc32c`
  - [x] Make linters happy about crc32 subtree
  - [x] Integrate `crc32c` library into build system
  - [x] MSVC build system

ACKs for top commit:
  sipa:
    ACK 677fb8e92380d4deb6a3753047c01f7cf7b5af91

Tree-SHA512: 37ee92a750e053e924bc4626b12bb3fd81faa9f8c5ebaa343931fee810c45ba05aa6051fdea82535fa351bf2be7297801b98af9469865fc5ead771650a5d6240

5 files changed, 16 insertions, 1260 deletions

diff --git a/src/leveldb/doc/bench/db_bench_sqlite3.cc b/src/leveldb/doc/bench/db_bench_sqlite3.cc
deleted file mode 100644
index e63aaa8dcc..0000000000
--- a/src/leveldb/doc/bench/db_bench_sqlite3.cc
+++ /dev/null
@@ -1,718 +0,0 @@
-// 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.
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <sqlite3.h>
-#include "util/histogram.h"
-#include "util/random.h"
-#include "util/testutil.h"
-
-// Comma-separated list of operations to run in the specified order
-//   Actual benchmarks:
-//
-//   fillseq       -- write N values in sequential key order in async mode
-//   fillseqsync   -- write N/100 values in sequential key order in sync mode
-//   fillseqbatch  -- batch write N values in sequential key order in async mode
-//   fillrandom    -- write N values in random key order in async mode
-//   fillrandsync  -- write N/100 values in random key order in sync mode
-//   fillrandbatch -- batch write N values in sequential key order in async mode
-//   overwrite     -- overwrite N values in random key order in async mode
-//   fillrand100K  -- write N/1000 100K values in random order in async mode
-//   fillseq100K   -- write N/1000 100K values in sequential order in async mode
-//   readseq       -- read N times sequentially
-//   readrandom    -- read N times in random order
-//   readrand100K  -- read N/1000 100K values in sequential order in async mode
-static const char* FLAGS_benchmarks =
-    "fillseq,"
-    "fillseqsync,"
-    "fillseqbatch,"
-    "fillrandom,"
-    "fillrandsync,"
-    "fillrandbatch,"
-    "overwrite,"
-    "overwritebatch,"
-    "readrandom,"
-    "readseq,"
-    "fillrand100K,"
-    "fillseq100K,"
-    "readseq,"
-    "readrand100K,"
-    ;
-
-// Number of key/values to place in database
-static int FLAGS_num = 1000000;
-
-// Number of read operations to do.  If negative, do FLAGS_num reads.
-static int FLAGS_reads = -1;
-
-// Size of each value
-static int FLAGS_value_size = 100;
-
-// Print histogram of operation timings
-static bool FLAGS_histogram = false;
-
-// Arrange to generate values that shrink to this fraction of
-// their original size after compression
-static double FLAGS_compression_ratio = 0.5;
-
-// Page size. Default 1 KB.
-static int FLAGS_page_size = 1024;
-
-// Number of pages.
-// Default cache size = FLAGS_page_size * FLAGS_num_pages = 4 MB.
-static int FLAGS_num_pages = 4096;
-
-// If true, do not destroy the existing database.  If you set this
-// flag and also specify a benchmark that wants a fresh database, that
-// benchmark will fail.
-static bool FLAGS_use_existing_db = false;
-
-// If true, we allow batch writes to occur
-static bool FLAGS_transaction = true;
-
-// If true, we enable Write-Ahead Logging
-static bool FLAGS_WAL_enabled = true;
-
-// Use the db with the following name.
-static const char* FLAGS_db = NULL;
-
-inline
-static void ExecErrorCheck(int status, char *err_msg) {
-  if (status != SQLITE_OK) {
-    fprintf(stderr, "SQL error: %s\n", err_msg);
-    sqlite3_free(err_msg);
-    exit(1);
-  }
-}
-
-inline
-static void StepErrorCheck(int status) {
-  if (status != SQLITE_DONE) {
-    fprintf(stderr, "SQL step error: status = %d\n", status);
-    exit(1);
-  }
-}
-
-inline
-static void ErrorCheck(int status) {
-  if (status != SQLITE_OK) {
-    fprintf(stderr, "sqlite3 error: status = %d\n", status);
-    exit(1);
-  }
-}
-
-inline
-static void WalCheckpoint(sqlite3* db_) {
-  // Flush all writes to disk
-  if (FLAGS_WAL_enabled) {
-    sqlite3_wal_checkpoint_v2(db_, NULL, SQLITE_CHECKPOINT_FULL, NULL, NULL);
-  }
-}
-
-namespace leveldb {
-
-// Helper for quickly generating random data.
-namespace {
-class RandomGenerator {
- private:
-  std::string data_;
-  int pos_;
-
- public:
-  RandomGenerator() {
-    // We use a limited amount of data over and over again and ensure
-    // that it is larger than the compression window (32KB), and also
-    // large enough to serve all typical value sizes we want to write.
-    Random rnd(301);
-    std::string piece;
-    while (data_.size() < 1048576) {
-      // Add a short fragment that is as compressible as specified
-      // by FLAGS_compression_ratio.
-      test::CompressibleString(&rnd, FLAGS_compression_ratio, 100, &piece);
-      data_.append(piece);
-    }
-    pos_ = 0;
-  }
-
-  Slice Generate(int len) {
-    if (pos_ + len > data_.size()) {
-      pos_ = 0;
-      assert(len < data_.size());
-    }
-    pos_ += len;
-    return Slice(data_.data() + pos_ - len, len);
-  }
-};
-
-static Slice TrimSpace(Slice s) {
-  int start = 0;
-  while (start < s.size() && isspace(s[start])) {
-    start++;
-  }
-  int limit = s.size();
-  while (limit > start && isspace(s[limit-1])) {
-    limit--;
-  }
-  return Slice(s.data() + start, limit - start);
-}
-
-}  // namespace
-
-class Benchmark {
- private:
-  sqlite3* db_;
-  int db_num_;
-  int num_;
-  int reads_;
-  double start_;
-  double last_op_finish_;
-  int64_t bytes_;
-  std::string message_;
-  Histogram hist_;
-  RandomGenerator gen_;
-  Random rand_;
-
-  // State kept for progress messages
-  int done_;
-  int next_report_;     // When to report next
-
-  void PrintHeader() {
-    const int kKeySize = 16;
-    PrintEnvironment();
-    fprintf(stdout, "Keys:       %d bytes each\n", kKeySize);
-    fprintf(stdout, "Values:     %d bytes each\n", FLAGS_value_size);
-    fprintf(stdout, "Entries:    %d\n", num_);
-    fprintf(stdout, "RawSize:    %.1f MB (estimated)\n",
-            ((static_cast<int64_t>(kKeySize + FLAGS_value_size) * num_)
-             / 1048576.0));
-    PrintWarnings();
-    fprintf(stdout, "------------------------------------------------\n");
-  }
-
-  void PrintWarnings() {
-#if defined(__GNUC__) && !defined(__OPTIMIZE__)
-    fprintf(stdout,
-            "WARNING: Optimization is disabled: benchmarks unnecessarily slow\n"
-            );
-#endif
-#ifndef NDEBUG
-    fprintf(stdout,
-            "WARNING: Assertions are enabled; benchmarks unnecessarily slow\n");
-#endif
-  }
-
-  void PrintEnvironment() {
-    fprintf(stderr, "SQLite:     version %s\n", SQLITE_VERSION);
-
-#if defined(__linux)
-    time_t now = time(NULL);
-    fprintf(stderr, "Date:       %s", ctime(&now));  // ctime() adds newline
-
-    FILE* cpuinfo = fopen("/proc/cpuinfo", "r");
-    if (cpuinfo != NULL) {
-      char line[1000];
-      int num_cpus = 0;
-      std::string cpu_type;
-      std::string cache_size;
-      while (fgets(line, sizeof(line), cpuinfo) != NULL) {
-        const char* sep = strchr(line, ':');
-        if (sep == NULL) {
-          continue;
-        }
-        Slice key = TrimSpace(Slice(line, sep - 1 - line));
-        Slice val = TrimSpace(Slice(sep + 1));
-        if (key == "model name") {
-          ++num_cpus;
-          cpu_type = val.ToString();
-        } else if (key == "cache size") {
-          cache_size = val.ToString();
-        }
-      }
-      fclose(cpuinfo);
-      fprintf(stderr, "CPU:        %d * %s\n", num_cpus, cpu_type.c_str());
-      fprintf(stderr, "CPUCache:   %s\n", cache_size.c_str());
-    }
-#endif
-  }
-
-  void Start() {
-    start_ = Env::Default()->NowMicros() * 1e-6;
-    bytes_ = 0;
-    message_.clear();
-    last_op_finish_ = start_;
-    hist_.Clear();
-    done_ = 0;
-    next_report_ = 100;
-  }
-
-  void FinishedSingleOp() {
-    if (FLAGS_histogram) {
-      double now = Env::Default()->NowMicros() * 1e-6;
-      double micros = (now - last_op_finish_) * 1e6;
-      hist_.Add(micros);
-      if (micros > 20000) {
-        fprintf(stderr, "long op: %.1f micros%30s\r", micros, "");
-        fflush(stderr);
-      }
-      last_op_finish_ = now;
-    }
-
-    done_++;
-    if (done_ >= next_report_) {
-      if      (next_report_ < 1000)   next_report_ += 100;
-      else if (next_report_ < 5000)   next_report_ += 500;
-      else if (next_report_ < 10000)  next_report_ += 1000;
-      else if (next_report_ < 50000)  next_report_ += 5000;
-      else if (next_report_ < 100000) next_report_ += 10000;
-      else if (next_report_ < 500000) next_report_ += 50000;
-      else                            next_report_ += 100000;
-      fprintf(stderr, "... finished %d ops%30s\r", done_, "");
-      fflush(stderr);
-    }
-  }
-
-  void Stop(const Slice& name) {
-    double finish = Env::Default()->NowMicros() * 1e-6;
-
-    // Pretend at least one op was done in case we are running a benchmark
-    // that does not call FinishedSingleOp().
-    if (done_ < 1) done_ = 1;
-
-    if (bytes_ > 0) {
-      char rate[100];
-      snprintf(rate, sizeof(rate), "%6.1f MB/s",
-               (bytes_ / 1048576.0) / (finish - start_));
-      if (!message_.empty()) {
-        message_  = std::string(rate) + " " + message_;
-      } else {
-        message_ = rate;
-      }
-    }
-
-    fprintf(stdout, "%-12s : %11.3f micros/op;%s%s\n",
-            name.ToString().c_str(),
-            (finish - start_) * 1e6 / done_,
-            (message_.empty() ? "" : " "),
-            message_.c_str());
-    if (FLAGS_histogram) {
-      fprintf(stdout, "Microseconds per op:\n%s\n", hist_.ToString().c_str());
-    }
-    fflush(stdout);
-  }
-
- public:
-  enum Order {
-    SEQUENTIAL,
-    RANDOM
-  };
-  enum DBState {
-    FRESH,
-    EXISTING
-  };
-
-  Benchmark()
-  : db_(NULL),
-    db_num_(0),
-    num_(FLAGS_num),
-    reads_(FLAGS_reads < 0 ? FLAGS_num : FLAGS_reads),
-    bytes_(0),
-    rand_(301) {
-    std::vector<std::string> files;
-    std::string test_dir;
-    Env::Default()->GetTestDirectory(&test_dir);
-    Env::Default()->GetChildren(test_dir, &files);
-    if (!FLAGS_use_existing_db) {
-      for (int i = 0; i < files.size(); i++) {
-        if (Slice(files[i]).starts_with("dbbench_sqlite3")) {
-          std::string file_name(test_dir);
-          file_name += "/";
-          file_name += files[i];
-          Env::Default()->DeleteFile(file_name.c_str());
-        }
-      }
-    }
-  }
-
-  ~Benchmark() {
-    int status = sqlite3_close(db_);
-    ErrorCheck(status);
-  }
-
-  void Run() {
-    PrintHeader();
-    Open();
-
-    const char* benchmarks = FLAGS_benchmarks;
-    while (benchmarks != NULL) {
-      const char* sep = strchr(benchmarks, ',');
-      Slice name;
-      if (sep == NULL) {
-        name = benchmarks;
-        benchmarks = NULL;
-      } else {
-        name = Slice(benchmarks, sep - benchmarks);
-        benchmarks = sep + 1;
-      }
-
-      bytes_ = 0;
-      Start();
-
-      bool known = true;
-      bool write_sync = false;
-      if (name == Slice("fillseq")) {
-        Write(write_sync, SEQUENTIAL, FRESH, num_, FLAGS_value_size, 1);
-        WalCheckpoint(db_);
-      } else if (name == Slice("fillseqbatch")) {
-        Write(write_sync, SEQUENTIAL, FRESH, num_, FLAGS_value_size, 1000);
-        WalCheckpoint(db_);
-      } else if (name == Slice("fillrandom")) {
-        Write(write_sync, RANDOM, FRESH, num_, FLAGS_value_size, 1);
-        WalCheckpoint(db_);
-      } else if (name == Slice("fillrandbatch")) {
-        Write(write_sync, RANDOM, FRESH, num_, FLAGS_value_size, 1000);
-        WalCheckpoint(db_);
-      } else if (name == Slice("overwrite")) {
-        Write(write_sync, RANDOM, EXISTING, num_, FLAGS_value_size, 1);
-        WalCheckpoint(db_);
-      } else if (name == Slice("overwritebatch")) {
-        Write(write_sync, RANDOM, EXISTING, num_, FLAGS_value_size, 1000);
-        WalCheckpoint(db_);
-      } else if (name == Slice("fillrandsync")) {
-        write_sync = true;
-        Write(write_sync, RANDOM, FRESH, num_ / 100, FLAGS_value_size, 1);
-        WalCheckpoint(db_);
-      } else if (name == Slice("fillseqsync")) {
-        write_sync = true;
-        Write(write_sync, SEQUENTIAL, FRESH, num_ / 100, FLAGS_value_size, 1);
-        WalCheckpoint(db_);
-      } else if (name == Slice("fillrand100K")) {
-        Write(write_sync, RANDOM, FRESH, num_ / 1000, 100 * 1000, 1);
-        WalCheckpoint(db_);
-      } else if (name == Slice("fillseq100K")) {
-        Write(write_sync, SEQUENTIAL, FRESH, num_ / 1000, 100 * 1000, 1);
-        WalCheckpoint(db_);
-      } else if (name == Slice("readseq")) {
-        ReadSequential();
-      } else if (name == Slice("readrandom")) {
-        Read(RANDOM, 1);
-      } else if (name == Slice("readrand100K")) {
-        int n = reads_;
-        reads_ /= 1000;
-        Read(RANDOM, 1);
-        reads_ = n;
-      } else {
-        known = false;
-        if (name != Slice()) {  // No error message for empty name
-          fprintf(stderr, "unknown benchmark '%s'\n", name.ToString().c_str());
-        }
-      }
-      if (known) {
-        Stop(name);
-      }
-    }
-  }
-
-  void Open() {
-    assert(db_ == NULL);
-
-    int status;
-    char file_name[100];
-    char* err_msg = NULL;
-    db_num_++;
-
-    // Open database
-    std::string tmp_dir;
-    Env::Default()->GetTestDirectory(&tmp_dir);
-    snprintf(file_name, sizeof(file_name),
-             "%s/dbbench_sqlite3-%d.db",
-             tmp_dir.c_str(),
-             db_num_);
-    status = sqlite3_open(file_name, &db_);
-    if (status) {
-      fprintf(stderr, "open error: %s\n", sqlite3_errmsg(db_));
-      exit(1);
-    }
-
-    // Change SQLite cache size
-    char cache_size[100];
-    snprintf(cache_size, sizeof(cache_size), "PRAGMA cache_size = %d",
-             FLAGS_num_pages);
-    status = sqlite3_exec(db_, cache_size, NULL, NULL, &err_msg);
-    ExecErrorCheck(status, err_msg);
-
-    // FLAGS_page_size is defaulted to 1024
-    if (FLAGS_page_size != 1024) {
-      char page_size[100];
-      snprintf(page_size, sizeof(page_size), "PRAGMA page_size = %d",
-               FLAGS_page_size);
-      status = sqlite3_exec(db_, page_size, NULL, NULL, &err_msg);
-      ExecErrorCheck(status, err_msg);
-    }
-
-    // Change journal mode to WAL if WAL enabled flag is on
-    if (FLAGS_WAL_enabled) {
-      std::string WAL_stmt = "PRAGMA journal_mode = WAL";
-
-      // LevelDB's default cache size is a combined 4 MB
-      std::string WAL_checkpoint = "PRAGMA wal_autocheckpoint = 4096";
-      status = sqlite3_exec(db_, WAL_stmt.c_str(), NULL, NULL, &err_msg);
-      ExecErrorCheck(status, err_msg);
-      status = sqlite3_exec(db_, WAL_checkpoint.c_str(), NULL, NULL, &err_msg);
-      ExecErrorCheck(status, err_msg);
-    }
-
-    // Change locking mode to exclusive and create tables/index for database
-    std::string locking_stmt = "PRAGMA locking_mode = EXCLUSIVE";
-    std::string create_stmt =
-          "CREATE TABLE test (key blob, value blob, PRIMARY KEY(key))";
-    std::string stmt_array[] = { locking_stmt, create_stmt };
-    int stmt_array_length = sizeof(stmt_array) / sizeof(std::string);
-    for (int i = 0; i < stmt_array_length; i++) {
-      status = sqlite3_exec(db_, stmt_array[i].c_str(), NULL, NULL, &err_msg);
-      ExecErrorCheck(status, err_msg);
-    }
-  }
-
-  void Write(bool write_sync, Order order, DBState state,
-             int num_entries, int value_size, int entries_per_batch) {
-    // Create new database if state == FRESH
-    if (state == FRESH) {
-      if (FLAGS_use_existing_db) {
-        message_ = "skipping (--use_existing_db is true)";
-        return;
-      }
-      sqlite3_close(db_);
-      db_ = NULL;
-      Open();
-      Start();
-    }
-
-    if (num_entries != num_) {
-      char msg[100];
-      snprintf(msg, sizeof(msg), "(%d ops)", num_entries);
-      message_ = msg;
-    }
-
-    char* err_msg = NULL;
-    int status;
-
-    sqlite3_stmt *replace_stmt, *begin_trans_stmt, *end_trans_stmt;
-    std::string replace_str = "REPLACE INTO test (key, value) VALUES (?, ?)";
-    std::string begin_trans_str = "BEGIN TRANSACTION;";
-    std::string end_trans_str = "END TRANSACTION;";
-
-    // Check for synchronous flag in options
-    std::string sync_stmt = (write_sync) ? "PRAGMA synchronous = FULL" :
-                                           "PRAGMA synchronous = OFF";
-    status = sqlite3_exec(db_, sync_stmt.c_str(), NULL, NULL, &err_msg);
-    ExecErrorCheck(status, err_msg);
-
-    // Preparing sqlite3 statements
-    status = sqlite3_prepare_v2(db_, replace_str.c_str(), -1,
-                                &replace_stmt, NULL);
-    ErrorCheck(status);
-    status = sqlite3_prepare_v2(db_, begin_trans_str.c_str(), -1,
-                                &begin_trans_stmt, NULL);
-    ErrorCheck(status);
-    status = sqlite3_prepare_v2(db_, end_trans_str.c_str(), -1,
-                                &end_trans_stmt, NULL);
-    ErrorCheck(status);
-
-    bool transaction = (entries_per_batch > 1);
-    for (int i = 0; i < num_entries; i += entries_per_batch) {
-      // Begin write transaction
-      if (FLAGS_transaction && transaction) {
-        status = sqlite3_step(begin_trans_stmt);
-        StepErrorCheck(status);
-        status = sqlite3_reset(begin_trans_stmt);
-        ErrorCheck(status);
-      }
-
-      // Create and execute SQL statements
-      for (int j = 0; j < entries_per_batch; j++) {
-        const char* value = gen_.Generate(value_size).data();
-
-        // Create values for key-value pair
-        const int k = (order == SEQUENTIAL) ? i + j :
-                      (rand_.Next() % num_entries);
-        char key[100];
-        snprintf(key, sizeof(key), "%016d", k);
-
-        // Bind KV values into replace_stmt
-        status = sqlite3_bind_blob(replace_stmt, 1, key, 16, SQLITE_STATIC);
-        ErrorCheck(status);
-        status = sqlite3_bind_blob(replace_stmt, 2, value,
-                                   value_size, SQLITE_STATIC);
-        ErrorCheck(status);
-
-        // Execute replace_stmt
-        bytes_ += value_size + strlen(key);
-        status = sqlite3_step(replace_stmt);
-        StepErrorCheck(status);
-
-        // Reset SQLite statement for another use
-        status = sqlite3_clear_bindings(replace_stmt);
-        ErrorCheck(status);
-        status = sqlite3_reset(replace_stmt);
-        ErrorCheck(status);
-
-        FinishedSingleOp();
-      }
-
-      // End write transaction
-      if (FLAGS_transaction && transaction) {
-        status = sqlite3_step(end_trans_stmt);
-        StepErrorCheck(status);
-        status = sqlite3_reset(end_trans_stmt);
-        ErrorCheck(status);
-      }
-    }
-
-    status = sqlite3_finalize(replace_stmt);
-    ErrorCheck(status);
-    status = sqlite3_finalize(begin_trans_stmt);
-    ErrorCheck(status);
-    status = sqlite3_finalize(end_trans_stmt);
-    ErrorCheck(status);
-  }
-
-  void Read(Order order, int entries_per_batch) {
-    int status;
-    sqlite3_stmt *read_stmt, *begin_trans_stmt, *end_trans_stmt;
-
-    std::string read_str = "SELECT * FROM test WHERE key = ?";
-    std::string begin_trans_str = "BEGIN TRANSACTION;";
-    std::string end_trans_str = "END TRANSACTION;";
-
-    // Preparing sqlite3 statements
-    status = sqlite3_prepare_v2(db_, begin_trans_str.c_str(), -1,
-                                &begin_trans_stmt, NULL);
-    ErrorCheck(status);
-    status = sqlite3_prepare_v2(db_, end_trans_str.c_str(), -1,
-                                &end_trans_stmt, NULL);
-    ErrorCheck(status);
-    status = sqlite3_prepare_v2(db_, read_str.c_str(), -1, &read_stmt, NULL);
-    ErrorCheck(status);
-
-    bool transaction = (entries_per_batch > 1);
-    for (int i = 0; i < reads_; i += entries_per_batch) {
-      // Begin read transaction
-      if (FLAGS_transaction && transaction) {
-        status = sqlite3_step(begin_trans_stmt);
-        StepErrorCheck(status);
-        status = sqlite3_reset(begin_trans_stmt);
-        ErrorCheck(status);
-      }
-
-      // Create and execute SQL statements
-      for (int j = 0; j < entries_per_batch; j++) {
-        // Create key value
-        char key[100];
-        int k = (order == SEQUENTIAL) ? i + j : (rand_.Next() % reads_);
-        snprintf(key, sizeof(key), "%016d", k);
-
-        // Bind key value into read_stmt
-        status = sqlite3_bind_blob(read_stmt, 1, key, 16, SQLITE_STATIC);
-        ErrorCheck(status);
-
-        // Execute read statement
-        while ((status = sqlite3_step(read_stmt)) == SQLITE_ROW) {}
-        StepErrorCheck(status);
-
-        // Reset SQLite statement for another use
-        status = sqlite3_clear_bindings(read_stmt);
-        ErrorCheck(status);
-        status = sqlite3_reset(read_stmt);
-        ErrorCheck(status);
-        FinishedSingleOp();
-      }
-
-      // End read transaction
-      if (FLAGS_transaction && transaction) {
-        status = sqlite3_step(end_trans_stmt);
-        StepErrorCheck(status);
-        status = sqlite3_reset(end_trans_stmt);
-        ErrorCheck(status);
-      }
-    }
-
-    status = sqlite3_finalize(read_stmt);
-    ErrorCheck(status);
-    status = sqlite3_finalize(begin_trans_stmt);
-    ErrorCheck(status);
-    status = sqlite3_finalize(end_trans_stmt);
-    ErrorCheck(status);
-  }
-
-  void ReadSequential() {
-    int status;
-    sqlite3_stmt *pStmt;
-    std::string read_str = "SELECT * FROM test ORDER BY key";
-
-    status = sqlite3_prepare_v2(db_, read_str.c_str(), -1, &pStmt, NULL);
-    ErrorCheck(status);
-    for (int i = 0; i < reads_ && SQLITE_ROW == sqlite3_step(pStmt); i++) {
-      bytes_ += sqlite3_column_bytes(pStmt, 1) + sqlite3_column_bytes(pStmt, 2);
-      FinishedSingleOp();
-    }
-
-    status = sqlite3_finalize(pStmt);
-    ErrorCheck(status);
-  }
-
-};
-
-}  // namespace leveldb
-
-int main(int argc, char** argv) {
-  std::string default_db_path;
-  for (int i = 1; i < argc; i++) {
-    double d;
-    int n;
-    char junk;
-    if (leveldb::Slice(argv[i]).starts_with("--benchmarks=")) {
-      FLAGS_benchmarks = argv[i] + strlen("--benchmarks=");
-    } else if (sscanf(argv[i], "--histogram=%d%c", &n, &junk) == 1 &&
-               (n == 0 || n == 1)) {
-      FLAGS_histogram = n;
-    } else if (sscanf(argv[i], "--compression_ratio=%lf%c", &d, &junk) == 1) {
-      FLAGS_compression_ratio = d;
-    } else if (sscanf(argv[i], "--use_existing_db=%d%c", &n, &junk) == 1 &&
-               (n == 0 || n == 1)) {
-      FLAGS_use_existing_db = n;
-    } else if (sscanf(argv[i], "--num=%d%c", &n, &junk) == 1) {
-      FLAGS_num = n;
-    } else if (sscanf(argv[i], "--reads=%d%c", &n, &junk) == 1) {
-      FLAGS_reads = n;
-    } else if (sscanf(argv[i], "--value_size=%d%c", &n, &junk) == 1) {
-      FLAGS_value_size = n;
-    } else if (leveldb::Slice(argv[i]) == leveldb::Slice("--no_transaction")) {
-      FLAGS_transaction = false;
-    } else if (sscanf(argv[i], "--page_size=%d%c", &n, &junk) == 1) {
-      FLAGS_page_size = n;
-    } else if (sscanf(argv[i], "--num_pages=%d%c", &n, &junk) == 1) {
-      FLAGS_num_pages = n;
-    } else if (sscanf(argv[i], "--WAL_enabled=%d%c", &n, &junk) == 1 &&
-               (n == 0 || n == 1)) {
-      FLAGS_WAL_enabled = n;
-    } else if (strncmp(argv[i], "--db=", 5) == 0) {
-      FLAGS_db = argv[i] + 5;
-    } else {
-      fprintf(stderr, "Invalid flag '%s'\n", argv[i]);
-      exit(1);
-    }
-  }
-
-  // Choose a location for the test database if none given with --db=<path>
-  if (FLAGS_db == NULL) {
-      leveldb::Env::Default()->GetTestDirectory(&default_db_path);
-      default_db_path += "/dbbench";
-      FLAGS_db = default_db_path.c_str();
-  }
-
-  leveldb::Benchmark benchmark;
-  benchmark.Run();
-  return 0;
-}
diff --git a/src/leveldb/doc/bench/db_bench_tree_db.cc b/src/leveldb/doc/bench/db_bench_tree_db.cc
deleted file mode 100644
index 4ca381f11f..0000000000
--- a/src/leveldb/doc/bench/db_bench_tree_db.cc
+++ /dev/null
@@ -1,528 +0,0 @@
-// 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.
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <kcpolydb.h>
-#include "util/histogram.h"
-#include "util/random.h"
-#include "util/testutil.h"
-
-// Comma-separated list of operations to run in the specified order
-//   Actual benchmarks:
-//
-//   fillseq       -- write N values in sequential key order in async mode
-//   fillrandom    -- write N values in random key order in async mode
-//   overwrite     -- overwrite N values in random key order in async mode
-//   fillseqsync   -- write N/100 values in sequential key order in sync mode
-//   fillrandsync  -- write N/100 values in random key order in sync mode
-//   fillrand100K  -- write N/1000 100K values in random order in async mode
-//   fillseq100K   -- write N/1000 100K values in seq order in async mode
-//   readseq       -- read N times sequentially
-//   readseq100K   -- read N/1000 100K values in sequential order in async mode
-//   readrand100K  -- read N/1000 100K values in sequential order in async mode
-//   readrandom    -- read N times in random order
-static const char* FLAGS_benchmarks =
-    "fillseq,"
-    "fillseqsync,"
-    "fillrandsync,"
-    "fillrandom,"
-    "overwrite,"
-    "readrandom,"
-    "readseq,"
-    "fillrand100K,"
-    "fillseq100K,"
-    "readseq100K,"
-    "readrand100K,"
-    ;
-
-// Number of key/values to place in database
-static int FLAGS_num = 1000000;
-
-// Number of read operations to do.  If negative, do FLAGS_num reads.
-static int FLAGS_reads = -1;
-
-// Size of each value
-static int FLAGS_value_size = 100;
-
-// Arrange to generate values that shrink to this fraction of
-// their original size after compression
-static double FLAGS_compression_ratio = 0.5;
-
-// Print histogram of operation timings
-static bool FLAGS_histogram = false;
-
-// Cache size. Default 4 MB
-static int FLAGS_cache_size = 4194304;
-
-// Page size. Default 1 KB
-static int FLAGS_page_size = 1024;
-
-// If true, do not destroy the existing database.  If you set this
-// flag and also specify a benchmark that wants a fresh database, that
-// benchmark will fail.
-static bool FLAGS_use_existing_db = false;
-
-// Compression flag. If true, compression is on. If false, compression
-// is off.
-static bool FLAGS_compression = true;
-
-// Use the db with the following name.
-static const char* FLAGS_db = NULL;
-
-inline
-static void DBSynchronize(kyotocabinet::TreeDB* db_)
-{
-  // Synchronize will flush writes to disk
-  if (!db_->synchronize()) {
-    fprintf(stderr, "synchronize error: %s\n", db_->error().name());
-  }
-}
-
-namespace leveldb {
-
-// Helper for quickly generating random data.
-namespace {
-class RandomGenerator {
- private:
-  std::string data_;
-  int pos_;
-
- public:
-  RandomGenerator() {
-    // We use a limited amount of data over and over again and ensure
-    // that it is larger than the compression window (32KB), and also
-    // large enough to serve all typical value sizes we want to write.
-    Random rnd(301);
-    std::string piece;
-    while (data_.size() < 1048576) {
-      // Add a short fragment that is as compressible as specified
-      // by FLAGS_compression_ratio.
-      test::CompressibleString(&rnd, FLAGS_compression_ratio, 100, &piece);
-      data_.append(piece);
-    }
-    pos_ = 0;
-  }
-
-  Slice Generate(int len) {
-    if (pos_ + len > data_.size()) {
-      pos_ = 0;
-      assert(len < data_.size());
-    }
-    pos_ += len;
-    return Slice(data_.data() + pos_ - len, len);
-  }
-};
-
-static Slice TrimSpace(Slice s) {
-  int start = 0;
-  while (start < s.size() && isspace(s[start])) {
-    start++;
-  }
-  int limit = s.size();
-  while (limit > start && isspace(s[limit-1])) {
-    limit--;
-  }
-  return Slice(s.data() + start, limit - start);
-}
-
-}  // namespace
-
-class Benchmark {
- private:
-  kyotocabinet::TreeDB* db_;
-  int db_num_;
-  int num_;
-  int reads_;
-  double start_;
-  double last_op_finish_;
-  int64_t bytes_;
-  std::string message_;
-  Histogram hist_;
-  RandomGenerator gen_;
-  Random rand_;
-  kyotocabinet::LZOCompressor<kyotocabinet::LZO::RAW> comp_;
-
-  // State kept for progress messages
-  int done_;
-  int next_report_;     // When to report next
-
-  void PrintHeader() {
-    const int kKeySize = 16;
-    PrintEnvironment();
-    fprintf(stdout, "Keys:       %d bytes each\n", kKeySize);
-    fprintf(stdout, "Values:     %d bytes each (%d bytes after compression)\n",
-            FLAGS_value_size,
-            static_cast<int>(FLAGS_value_size * FLAGS_compression_ratio + 0.5));
-    fprintf(stdout, "Entries:    %d\n", num_);
-    fprintf(stdout, "RawSize:    %.1f MB (estimated)\n",
-            ((static_cast<int64_t>(kKeySize + FLAGS_value_size) * num_)
-             / 1048576.0));
-    fprintf(stdout, "FileSize:   %.1f MB (estimated)\n",
-            (((kKeySize + FLAGS_value_size * FLAGS_compression_ratio) * num_)
-             / 1048576.0));
-    PrintWarnings();
-    fprintf(stdout, "------------------------------------------------\n");
-  }
-
-  void PrintWarnings() {
-#if defined(__GNUC__) && !defined(__OPTIMIZE__)
-    fprintf(stdout,
-            "WARNING: Optimization is disabled: benchmarks unnecessarily slow\n"
-            );
-#endif
-#ifndef NDEBUG
-    fprintf(stdout,
-            "WARNING: Assertions are enabled; benchmarks unnecessarily slow\n");
-#endif
-  }
-
-  void PrintEnvironment() {
-    fprintf(stderr, "Kyoto Cabinet:    version %s, lib ver %d, lib rev %d\n",
-            kyotocabinet::VERSION, kyotocabinet::LIBVER, kyotocabinet::LIBREV);
-
-#if defined(__linux)
-    time_t now = time(NULL);
-    fprintf(stderr, "Date:           %s", ctime(&now));  // ctime() adds newline
-
-    FILE* cpuinfo = fopen("/proc/cpuinfo", "r");
-    if (cpuinfo != NULL) {
-      char line[1000];
-      int num_cpus = 0;
-      std::string cpu_type;
-      std::string cache_size;
-      while (fgets(line, sizeof(line), cpuinfo) != NULL) {
-        const char* sep = strchr(line, ':');
-        if (sep == NULL) {
-          continue;
-        }
-        Slice key = TrimSpace(Slice(line, sep - 1 - line));
-        Slice val = TrimSpace(Slice(sep + 1));
-        if (key == "model name") {
-          ++num_cpus;
-          cpu_type = val.ToString();
-        } else if (key == "cache size") {
-          cache_size = val.ToString();
-        }
-      }
-      fclose(cpuinfo);
-      fprintf(stderr, "CPU:            %d * %s\n", num_cpus, cpu_type.c_str());
-      fprintf(stderr, "CPUCache:       %s\n", cache_size.c_str());
-    }
-#endif
-  }
-
-  void Start() {
-    start_ = Env::Default()->NowMicros() * 1e-6;
-    bytes_ = 0;
-    message_.clear();
-    last_op_finish_ = start_;
-    hist_.Clear();
-    done_ = 0;
-    next_report_ = 100;
-  }
-
-  void FinishedSingleOp() {
-    if (FLAGS_histogram) {
-      double now = Env::Default()->NowMicros() * 1e-6;
-      double micros = (now - last_op_finish_) * 1e6;
-      hist_.Add(micros);
-      if (micros > 20000) {
-        fprintf(stderr, "long op: %.1f micros%30s\r", micros, "");
-        fflush(stderr);
-      }
-      last_op_finish_ = now;
-    }
-
-    done_++;
-    if (done_ >= next_report_) {
-      if      (next_report_ < 1000)   next_report_ += 100;
-      else if (next_report_ < 5000)   next_report_ += 500;
-      else if (next_report_ < 10000)  next_report_ += 1000;
-      else if (next_report_ < 50000)  next_report_ += 5000;
-      else if (next_report_ < 100000) next_report_ += 10000;
-      else if (next_report_ < 500000) next_report_ += 50000;
-      else                            next_report_ += 100000;
-      fprintf(stderr, "... finished %d ops%30s\r", done_, "");
-      fflush(stderr);
-    }
-  }
-
-  void Stop(const Slice& name) {
-    double finish = Env::Default()->NowMicros() * 1e-6;
-
-    // Pretend at least one op was done in case we are running a benchmark
-    // that does not call FinishedSingleOp().
-    if (done_ < 1) done_ = 1;
-
-    if (bytes_ > 0) {
-      char rate[100];
-      snprintf(rate, sizeof(rate), "%6.1f MB/s",
-               (bytes_ / 1048576.0) / (finish - start_));
-      if (!message_.empty()) {
-        message_  = std::string(rate) + " " + message_;
-      } else {
-        message_ = rate;
-      }
-    }
-
-    fprintf(stdout, "%-12s : %11.3f micros/op;%s%s\n",
-            name.ToString().c_str(),
-            (finish - start_) * 1e6 / done_,
-            (message_.empty() ? "" : " "),
-            message_.c_str());
-    if (FLAGS_histogram) {
-      fprintf(stdout, "Microseconds per op:\n%s\n", hist_.ToString().c_str());
-    }
-    fflush(stdout);
-  }
-
- public:
-  enum Order {
-    SEQUENTIAL,
-    RANDOM
-  };
-  enum DBState {
-    FRESH,
-    EXISTING
-  };
-
-  Benchmark()
-  : db_(NULL),
-    num_(FLAGS_num),
-    reads_(FLAGS_reads < 0 ? FLAGS_num : FLAGS_reads),
-    bytes_(0),
-    rand_(301) {
-    std::vector<std::string> files;
-    std::string test_dir;
-    Env::Default()->GetTestDirectory(&test_dir);
-    Env::Default()->GetChildren(test_dir.c_str(), &files);
-    if (!FLAGS_use_existing_db) {
-      for (int i = 0; i < files.size(); i++) {
-        if (Slice(files[i]).starts_with("dbbench_polyDB")) {
-          std::string file_name(test_dir);
-          file_name += "/";
-          file_name += files[i];
-          Env::Default()->DeleteFile(file_name.c_str());
-        }
-      }
-    }
-  }
-
-  ~Benchmark() {
-    if (!db_->close()) {
-      fprintf(stderr, "close error: %s\n", db_->error().name());
-    }
-  }
-
-  void Run() {
-    PrintHeader();
-    Open(false);
-
-    const char* benchmarks = FLAGS_benchmarks;
-    while (benchmarks != NULL) {
-      const char* sep = strchr(benchmarks, ',');
-      Slice name;
-      if (sep == NULL) {
-        name = benchmarks;
-        benchmarks = NULL;
-      } else {
-        name = Slice(benchmarks, sep - benchmarks);
-        benchmarks = sep + 1;
-      }
-
-      Start();
-
-      bool known = true;
-      bool write_sync = false;
-      if (name == Slice("fillseq")) {
-        Write(write_sync, SEQUENTIAL, FRESH, num_, FLAGS_value_size, 1);
-        DBSynchronize(db_);
-      } else if (name == Slice("fillrandom")) {
-        Write(write_sync, RANDOM, FRESH, num_, FLAGS_value_size, 1);
-        DBSynchronize(db_);
-      } else if (name == Slice("overwrite")) {
-        Write(write_sync, RANDOM, EXISTING, num_, FLAGS_value_size, 1);
-        DBSynchronize(db_);
-      } else if (name == Slice("fillrandsync")) {
-        write_sync = true;
-        Write(write_sync, RANDOM, FRESH, num_ / 100, FLAGS_value_size, 1);
-        DBSynchronize(db_);
-      } else if (name == Slice("fillseqsync")) {
-        write_sync = true;
-        Write(write_sync, SEQUENTIAL, FRESH, num_ / 100, FLAGS_value_size, 1);
-        DBSynchronize(db_);
-      } else if (name == Slice("fillrand100K")) {
-        Write(write_sync, RANDOM, FRESH, num_ / 1000, 100 * 1000, 1);
-        DBSynchronize(db_);
-      } else if (name == Slice("fillseq100K")) {
-        Write(write_sync, SEQUENTIAL, FRESH, num_ / 1000, 100 * 1000, 1);
-        DBSynchronize(db_);
-      } else if (name == Slice("readseq")) {
-        ReadSequential();
-      } else if (name == Slice("readrandom")) {
-        ReadRandom();
-      } else if (name == Slice("readrand100K")) {
-        int n = reads_;
-        reads_ /= 1000;
-        ReadRandom();
-        reads_ = n;
-      } else if (name == Slice("readseq100K")) {
-        int n = reads_;
-        reads_ /= 1000;
-        ReadSequential();
-        reads_ = n;
-      } else {
-        known = false;
-        if (name != Slice()) {  // No error message for empty name
-          fprintf(stderr, "unknown benchmark '%s'\n", name.ToString().c_str());
-        }
-      }
-      if (known) {
-        Stop(name);
-      }
-    }
-  }
-
- private:
-    void Open(bool sync) {
-    assert(db_ == NULL);
-
-    // Initialize db_
-    db_ = new kyotocabinet::TreeDB();
-    char file_name[100];
-    db_num_++;
-    std::string test_dir;
-    Env::Default()->GetTestDirectory(&test_dir);
-    snprintf(file_name, sizeof(file_name),
-             "%s/dbbench_polyDB-%d.kct",
-             test_dir.c_str(),
-             db_num_);
-
-    // Create tuning options and open the database
-    int open_options = kyotocabinet::PolyDB::OWRITER |
-                       kyotocabinet::PolyDB::OCREATE;
-    int tune_options = kyotocabinet::TreeDB::TSMALL |
-        kyotocabinet::TreeDB::TLINEAR;
-    if (FLAGS_compression) {
-      tune_options |= kyotocabinet::TreeDB::TCOMPRESS;
-      db_->tune_compressor(&comp_);
-    }
-    db_->tune_options(tune_options);
-    db_->tune_page_cache(FLAGS_cache_size);
-    db_->tune_page(FLAGS_page_size);
-    db_->tune_map(256LL<<20);
-    if (sync) {
-      open_options |= kyotocabinet::PolyDB::OAUTOSYNC;
-    }
-    if (!db_->open(file_name, open_options)) {
-      fprintf(stderr, "open error: %s\n", db_->error().name());
-    }
-  }
-
-  void Write(bool sync, Order order, DBState state,
-             int num_entries, int value_size, int entries_per_batch) {
-    // Create new database if state == FRESH
-    if (state == FRESH) {
-      if (FLAGS_use_existing_db) {
-        message_ = "skipping (--use_existing_db is true)";
-        return;
-      }
-      delete db_;
-      db_ = NULL;
-      Open(sync);
-      Start();  // Do not count time taken to destroy/open
-    }
-
-    if (num_entries != num_) {
-      char msg[100];
-      snprintf(msg, sizeof(msg), "(%d ops)", num_entries);
-      message_ = msg;
-    }
-
-    // Write to database
-    for (int i = 0; i < num_entries; i++)
-    {
-      const int k = (order == SEQUENTIAL) ? i : (rand_.Next() % num_entries);
-      char key[100];
-      snprintf(key, sizeof(key), "%016d", k);
-      bytes_ += value_size + strlen(key);
-      std::string cpp_key = key;
-      if (!db_->set(cpp_key, gen_.Generate(value_size).ToString())) {
-        fprintf(stderr, "set error: %s\n", db_->error().name());
-      }
-      FinishedSingleOp();
-    }
-  }
-
-  void ReadSequential() {
-    kyotocabinet::DB::Cursor* cur = db_->cursor();
-    cur->jump();
-    std::string ckey, cvalue;
-    while (cur->get(&ckey, &cvalue, true)) {
-      bytes_ += ckey.size() + cvalue.size();
-      FinishedSingleOp();
-    }
-    delete cur;
-  }
-
-  void ReadRandom() {
-    std::string value;
-    for (int i = 0; i < reads_; i++) {
-      char key[100];
-      const int k = rand_.Next() % reads_;
-      snprintf(key, sizeof(key), "%016d", k);
-      db_->get(key, &value);
-      FinishedSingleOp();
-    }
-  }
-};
-
-}  // namespace leveldb
-
-int main(int argc, char** argv) {
-  std::string default_db_path;
-  for (int i = 1; i < argc; i++) {
-    double d;
-    int n;
-    char junk;
-    if (leveldb::Slice(argv[i]).starts_with("--benchmarks=")) {
-      FLAGS_benchmarks = argv[i] + strlen("--benchmarks=");
-    } else if (sscanf(argv[i], "--compression_ratio=%lf%c", &d, &junk) == 1) {
-      FLAGS_compression_ratio = d;
-    } else if (sscanf(argv[i], "--histogram=%d%c", &n, &junk) == 1 &&
-               (n == 0 || n == 1)) {
-      FLAGS_histogram = n;
-    } else if (sscanf(argv[i], "--num=%d%c", &n, &junk) == 1) {
-      FLAGS_num = n;
-    } else if (sscanf(argv[i], "--reads=%d%c", &n, &junk) == 1) {
-      FLAGS_reads = n;
-    } else if (sscanf(argv[i], "--value_size=%d%c", &n, &junk) == 1) {
-      FLAGS_value_size = n;
-    } else if (sscanf(argv[i], "--cache_size=%d%c", &n, &junk) == 1) {
-      FLAGS_cache_size = n;
-    } else if (sscanf(argv[i], "--page_size=%d%c", &n, &junk) == 1) {
-      FLAGS_page_size = n;
-    } else if (sscanf(argv[i], "--compression=%d%c", &n, &junk) == 1 &&
-               (n == 0 || n == 1)) {
-      FLAGS_compression = (n == 1) ? true : false;
-    } else if (strncmp(argv[i], "--db=", 5) == 0) {
-      FLAGS_db = argv[i] + 5;
-    } else {
-      fprintf(stderr, "Invalid flag '%s'\n", argv[i]);
-      exit(1);
-    }
-  }
-
-  // Choose a location for the test database if none given with --db=<path>
-  if (FLAGS_db == NULL) {
-      leveldb::Env::Default()->GetTestDirectory(&default_db_path);
-      default_db_path += "/dbbench";
-      FLAGS_db = default_db_path.c_str();
-  }
-
-  leveldb::Benchmark benchmark;
-  benchmark.Run();
-  return 0;
-}
diff --git a/src/leveldb/doc/benchmark.html b/src/leveldb/doc/benchmark.html
index c4639772c1..f3fd77144c 100644
--- a/src/leveldb/doc/benchmark.html
+++ b/src/leveldb/doc/benchmark.html
@@ -90,9 +90,9 @@ div.bsql {
 <h4>Benchmark Source Code</h4>
 <p>We wrote benchmark tools for SQLite and Kyoto TreeDB based on LevelDB's <span class="code">db_bench</span>. The code for each of the benchmarks resides here:</p>
 <ul>
-	<li> <b>LevelDB:</b> <a href="http://code.google.com/p/leveldb/source/browse/trunk/db/db_bench.cc">db/db_bench.cc</a>.</li>
-	<li> <b>SQLite:</b> <a href="http://code.google.com/p/leveldb/source/browse/#svn%2Ftrunk%2Fdoc%2Fbench%2Fdb_bench_sqlite3.cc">doc/bench/db_bench_sqlite3.cc</a>.</li>
-	<li> <b>Kyoto TreeDB:</b> <a href="http://code.google.com/p/leveldb/source/browse/#svn%2Ftrunk%2Fdoc%2Fbench%2Fdb_bench_tree_db.cc">doc/bench/db_bench_tree_db.cc</a>.</li>
+	<li> <b>LevelDB:</b> <a href="https://github.com/google/leveldb/blob/master/benchmarks/db_bench.cc">benchmarks/db_bench.cc</a>.</li>
+	<li> <b>SQLite:</b> <a href="https://github.com/google/leveldb/blob/master/benchmarks/db_bench_sqlite3.cc">benchmarks/db_bench_sqlite3.cc</a>.</li>
+	<li> <b>Kyoto TreeDB:</b> <a href="https://github.com/google/leveldb/blob/master/benchmarks/db_bench_tree_db.cc">benchmarks/db_bench_tree_db.cc</a>.</li>
 </ul>
 
 <h4>Custom Build Specifications</h4>
diff --git a/src/leveldb/doc/impl.md b/src/leveldb/doc/impl.md
index 4b13f2a6ba..cacabb96fc 100644
--- a/src/leveldb/doc/impl.md
+++ b/src/leveldb/doc/impl.md
@@ -64,13 +64,15 @@ Other files used for miscellaneous purposes may also be present (LOCK, *.dbtmp).
 
 ## Level 0
 
-When the log file grows above a certain size (1MB by default):
-Create a brand new memtable and log file and direct future updates here
+When the log file grows above a certain size (4MB by default):
+Create a brand new memtable and log file and direct future updates here.
+
 In the background:
-Write the contents of the previous memtable to an sstable
-Discard the memtable
-Delete the old log file and the old memtable
-Add the new sstable to the young (level-0) level.
+
+1. Write the contents of the previous memtable to an sstable.
+2. Discard the memtable.
+3. Delete the old log file and the old memtable.
+4. Add the new sstable to the young (level-0) level.
 
 ## Compactions
 
diff --git a/src/leveldb/doc/index.md b/src/leveldb/doc/index.md
index be8569692b..3d9a25805b 100644
--- a/src/leveldb/doc/index.md
+++ b/src/leveldb/doc/index.md
@@ -307,7 +307,7 @@ version numbers found in the keys to decide how to interpret them.
 ## Performance
 
 Performance can be tuned by changing the default values of the types defined in
-`include/leveldb/options.h`.
+`include/options.h`.
 
 ### Block size
 
@@ -338,19 +338,19 @@ options.compression = leveldb::kNoCompression;
 ### Cache
 
 The contents of the database are stored in a set of files in the filesystem and
-each file stores a sequence of compressed blocks. If options.cache is non-NULL,
-it is used to cache frequently used uncompressed block contents.
+each file stores a sequence of compressed blocks. If options.block_cache is
+non-NULL, it is used to cache frequently used uncompressed block contents.
 
 ```c++
 #include "leveldb/cache.h"
 
 leveldb::Options options;
-options.cache = leveldb::NewLRUCache(100 * 1048576);  // 100MB cache
+options.block_cache = leveldb::NewLRUCache(100 * 1048576);  // 100MB cache
 leveldb::DB* db;
 leveldb::DB::Open(options, name, &db);
 ... use the db ...
 delete db
-delete options.cache;
+delete options.block_cache;
 ```
 
 Note that the cache holds uncompressed data, and therefore it should be sized