Speed up Snappy uncompression, new Logger interface.

- Removed one copy of an uncompressed block contents changing
  the signature of Snappy_Uncompress() so it uncompresses into a
  flat array instead of a std::string.
        
  Speeds up readrandom ~10%.

- Instead of a combination of Env/WritableFile, we now have a
  Logger interface that can be easily overridden applications
  that want to supply their own logging.

- Separated out the gcc and Sun Studio parts of atomic_pointer.h
  so we can use 'asm', 'volatile' keywords for Sun Studio.




git-svn-id: https://leveldb.googlecode.com/svn/trunk@39 62dab493-f737-651d-591e-8d6aee1b9529

17 files changed, 261 insertions, 212 deletions

diff --git a/db/db_bench.cc b/db/db_bench.cc
index 53b8c53..7b4e41a 100644
--- a/db/db_bench.cc
+++ b/db/db_bench.cc
@@ -472,13 +472,14 @@ class Benchmark {
     std::string compressed;
     bool ok = port::Snappy_Compress(input.data(), input.size(), &compressed);
     int64_t bytes = 0;
-    std::string uncompressed;
+    char* uncompressed = new char[input.size()];
     while (ok && bytes < 1024 * 1048576) {  // Compress 1G
       ok =  port::Snappy_Uncompress(compressed.data(), compressed.size(),
-                                    &uncompressed);
-      bytes += uncompressed.size();
+                                    uncompressed);
+      bytes += input.size();
       FinishedSingleOp();
     }
+    delete[] uncompressed;
 
     if (!ok) {
       message_ = "(snappy failure)";
diff --git a/db/db_impl.cc b/db/db_impl.cc
index 48056da..5a0648e 100644
--- a/db/db_impl.cc
+++ b/db/db_impl.cc
@@ -68,16 +68,6 @@ struct DBImpl::CompactionState {
   }
 };
 
-namespace {
-class NullWritableFile : public WritableFile {
- public:
-  virtual Status Append(const Slice& data) { return Status::OK(); }
-  virtual Status Close() { return Status::OK(); }
-  virtual Status Flush() { return Status::OK(); }
-  virtual Status Sync() { return Status::OK(); }
-};
-}
-
 // Fix user-supplied options to be reasonable
 template <class T,class V>
 static void ClipToRange(T* ptr, V minvalue, V maxvalue) {
@@ -96,11 +86,10 @@ Options SanitizeOptions(const std::string& dbname,
     // Open a log file in the same directory as the db
     src.env->CreateDir(dbname);  // In case it does not exist
     src.env->RenameFile(InfoLogFileName(dbname), OldInfoLogFileName(dbname));
-    Status s = src.env->NewWritableFile(InfoLogFileName(dbname),
-                                        &result.info_log);
+    Status s = src.env->NewLogger(InfoLogFileName(dbname), &result.info_log);
     if (!s.ok()) {
       // No place suitable for logging
-      result.info_log = new NullWritableFile;
+      result.info_log = NULL;
     }
   }
   if (result.block_cache == NULL) {
@@ -201,7 +190,7 @@ void DBImpl::MaybeIgnoreError(Status* s) const {
   if (s->ok() || options_.paranoid_checks) {
     // No change needed
   } else {
-    Log(env_, options_.info_log, "Ignoring error %s", s->ToString().c_str());
+    Log(options_.info_log, "Ignoring error %s", s->ToString().c_str());
     *s = Status::OK();
   }
 }
@@ -247,7 +236,7 @@ void DBImpl::DeleteObsoleteFiles() {
         if (type == kTableFile) {
           table_cache_->Evict(number);
         }
-        Log(env_, options_.info_log, "Delete type=%d #%lld\n",
+        Log(options_.info_log, "Delete type=%d #%lld\n",
             int(type),
             static_cast<unsigned long long>(number));
         env_->DeleteFile(dbname_ + "/" + filenames[i]);
@@ -336,11 +325,11 @@ Status DBImpl::RecoverLogFile(uint64_t log_number,
                               SequenceNumber* max_sequence) {
   struct LogReporter : public log::Reader::Reporter {
     Env* env;
-    WritableFile* info_log;
+    Logger* info_log;
     const char* fname;
     Status* status;  // NULL if options_.paranoid_checks==false
     virtual void Corruption(size_t bytes, const Status& s) {
-      Log(env, info_log, "%s%s: dropping %d bytes; %s",
+      Log(info_log, "%s%s: dropping %d bytes; %s",
           (this->status == NULL ? "(ignoring error) " : ""),
           fname, static_cast<int>(bytes), s.ToString().c_str());
       if (this->status != NULL && this->status->ok()) *this->status = s;
@@ -370,7 +359,7 @@ Status DBImpl::RecoverLogFile(uint64_t log_number,
   // large sequence numbers).
   log::Reader reader(file, &reporter, true/*checksum*/,
                      0/*initial_offset*/);
-  Log(env_, options_.info_log, "Recovering log #%llu",
+  Log(options_.info_log, "Recovering log #%llu",
       (unsigned long long) log_number);
 
   // Read all the records and add to a memtable
@@ -434,7 +423,7 @@ Status DBImpl::WriteLevel0Table(MemTable* mem, VersionEdit* edit,
   meta.number = versions_->NewFileNumber();
   pending_outputs_.insert(meta.number);
   Iterator* iter = mem->NewIterator();
-  Log(env_, options_.info_log, "Level-0 table #%llu: started",
+  Log(options_.info_log, "Level-0 table #%llu: started",
       (unsigned long long) meta.number);
 
   Status s;
@@ -444,7 +433,7 @@ Status DBImpl::WriteLevel0Table(MemTable* mem, VersionEdit* edit,
     mutex_.Lock();
   }
 
-  Log(env_, options_.info_log, "Level-0 table #%llu: %lld bytes %s",
+  Log(options_.info_log, "Level-0 table #%llu: %lld bytes %s",
       (unsigned long long) meta.number,
       (unsigned long long) meta.file_size,
       s.ToString().c_str());
@@ -613,7 +602,7 @@ void DBImpl::BackgroundCompaction() {
                        f->smallest, f->largest);
     status = versions_->LogAndApply(c->edit());
     VersionSet::LevelSummaryStorage tmp;
-    Log(env_, options_.info_log, "Moved #%lld to level-%d %lld bytes %s: %s\n",
+    Log(options_.info_log, "Moved #%lld to level-%d %lld bytes %s: %s\n",
         static_cast<unsigned long long>(f->number),
         c->level() + 1,
         static_cast<unsigned long long>(f->file_size),
@@ -631,7 +620,7 @@ void DBImpl::BackgroundCompaction() {
   } else if (shutting_down_.Acquire_Load()) {
     // Ignore compaction errors found during shutting down
   } else {
-    Log(env_, options_.info_log,
+    Log(options_.info_log,
         "Compaction error: %s", status.ToString().c_str());
     if (options_.paranoid_checks && bg_error_.ok()) {
       bg_error_ = status;
@@ -727,7 +716,7 @@ Status DBImpl::FinishCompactionOutputFile(CompactionState* compact,
     s = iter->status();
     delete iter;
     if (s.ok()) {
-      Log(env_, options_.info_log,
+      Log(options_.info_log,
           "Generated table #%llu: %lld keys, %lld bytes",
           (unsigned long long) output_number,
           (unsigned long long) current_entries,
@@ -740,7 +729,7 @@ Status DBImpl::FinishCompactionOutputFile(CompactionState* compact,
 
 Status DBImpl::InstallCompactionResults(CompactionState* compact) {
   mutex_.AssertHeld();
-  Log(env_, options_.info_log,  "Compacted %d@%d + %d@%d files => %lld bytes",
+  Log(options_.info_log,  "Compacted %d@%d + %d@%d files => %lld bytes",
       compact->compaction->num_input_files(0),
       compact->compaction->level(),
       compact->compaction->num_input_files(1),
@@ -776,7 +765,7 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
   const uint64_t start_micros = env_->NowMicros();
   int64_t imm_micros = 0;  // Micros spent doing imm_ compactions
 
-  Log(env_, options_.info_log,  "Compacting %d@%d + %d@%d files",
+  Log(options_.info_log,  "Compacting %d@%d + %d@%d files",
       compact->compaction->num_input_files(0),
       compact->compaction->level(),
       compact->compaction->num_input_files(1),
@@ -859,7 +848,7 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
       last_sequence_for_key = ikey.sequence;
     }
 #if 0
-    Log(env_, options_.info_log,
+    Log(options_.info_log,
         "  Compact: %s, seq %d, type: %d %d, drop: %d, is_base: %d, "
         "%d smallest_snapshot: %d",
         ikey.user_key.ToString().c_str(),
@@ -925,7 +914,7 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
     status = InstallCompactionResults(compact);
   }
   VersionSet::LevelSummaryStorage tmp;
-  Log(env_, options_.info_log,
+  Log(options_.info_log,
       "compacted to: %s", versions_->LevelSummary(&tmp));
   return status;
 }
@@ -1112,7 +1101,7 @@ Status DBImpl::MakeRoomForWrite(bool force) {
       bg_cv_.Wait();
     } else if (versions_->NumLevelFiles(0) >= config::kL0_StopWritesTrigger) {
       // There are too many level-0 files.
-      Log(env_, options_.info_log, "waiting...\n");
+      Log(options_.info_log, "waiting...\n");
       bg_cv_.Wait();
     } else {
       // Attempt to switch to a new memtable and trigger compaction of old
diff --git a/db/repair.cc b/db/repair.cc
index 2e3f506..5bcdb56 100644
--- a/db/repair.cc
+++ b/db/repair.cc
@@ -78,7 +78,7 @@ class Repairer {
       for (size_t i = 0; i < tables_.size(); i++) {
         bytes += tables_[i].meta.file_size;
       }
-      Log(env_, options_.info_log,
+      Log(options_.info_log,
           "**** Repaired leveldb %s; "
           "recovered %d files; %llu bytes. "
           "Some data may have been lost. "
@@ -149,7 +149,7 @@ class Repairer {
       std::string logname = LogFileName(dbname_, logs_[i]);
       Status status = ConvertLogToTable(logs_[i]);
       if (!status.ok()) {
-        Log(env_, options_.info_log, "Log #%llu: ignoring conversion error: %s",
+        Log(options_.info_log, "Log #%llu: ignoring conversion error: %s",
             (unsigned long long) logs_[i],
             status.ToString().c_str());
       }
@@ -160,11 +160,11 @@ class Repairer {
   Status ConvertLogToTable(uint64_t log) {
     struct LogReporter : public log::Reader::Reporter {
       Env* env;
-      WritableFile* info_log;
+      Logger* info_log;
       uint64_t lognum;
       virtual void Corruption(size_t bytes, const Status& s) {
         // We print error messages for corruption, but continue repairing.
-        Log(env, info_log, "Log #%llu: dropping %d bytes; %s",
+        Log(info_log, "Log #%llu: dropping %d bytes; %s",
             (unsigned long long) lognum,
             static_cast<int>(bytes),
             s.ToString().c_str());
@@ -209,7 +209,7 @@ class Repairer {
       if (status.ok()) {
         counter += WriteBatchInternal::Count(&batch);
       } else {
-        Log(env_, options_.info_log, "Log #%llu: ignoring %s",
+        Log(options_.info_log, "Log #%llu: ignoring %s",
             (unsigned long long) log,
             status.ToString().c_str());
         status = Status::OK();  // Keep going with rest of file
@@ -231,7 +231,7 @@ class Repairer {
         table_numbers_.push_back(meta.number);
       }
     }
-    Log(env_, options_.info_log, "Log #%llu: %d ops saved to Table #%llu %s",
+    Log(options_.info_log, "Log #%llu: %d ops saved to Table #%llu %s",
         (unsigned long long) log,
         counter,
         (unsigned long long) meta.number,
@@ -247,7 +247,7 @@ class Repairer {
       Status status = ScanTable(&t);
       if (!status.ok()) {
         std::string fname = TableFileName(dbname_, table_numbers_[i]);
-        Log(env_, options_.info_log, "Table #%llu: ignoring %s",
+        Log(options_.info_log, "Table #%llu: ignoring %s",
             (unsigned long long) table_numbers_[i],
             status.ToString().c_str());
         ArchiveFile(fname);
@@ -270,7 +270,7 @@ class Repairer {
       for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
         Slice key = iter->key();
         if (!ParseInternalKey(key, &parsed)) {
-          Log(env_, options_.info_log, "Table #%llu: unparsable key %s",
+          Log(options_.info_log, "Table #%llu: unparsable key %s",
               (unsigned long long) t->meta.number,
               EscapeString(key).c_str());
           continue;
@@ -291,7 +291,7 @@ class Repairer {
       }
       delete iter;
     }
-    Log(env_, options_.info_log, "Table #%llu: %d entries %s",
+    Log(options_.info_log, "Table #%llu: %d entries %s",
         (unsigned long long) t->meta.number,
         counter,
         status.ToString().c_str());
@@ -373,7 +373,7 @@ class Repairer {
     new_file.append("/");
     new_file.append((slash == NULL) ? fname.c_str() : slash + 1);
     Status s = env_->RenameFile(fname, new_file);
-    Log(env_, options_.info_log, "Archiving %s: %s\n",
+    Log(options_.info_log, "Archiving %s: %s\n",
         fname.c_str(), s.ToString().c_str());
   }
 };
diff --git a/db/version_set.cc b/db/version_set.cc
index 62bd6dd..5040b72 100644
--- a/db/version_set.cc
+++ b/db/version_set.cc
@@ -1124,7 +1124,7 @@ void VersionSet::SetupOtherInputs(Compaction* c) {
       std::vector<FileMetaData*> expanded1;
       GetOverlappingInputs(level+1, new_start, new_limit, &expanded1);
       if (expanded1.size() == c->inputs_[1].size()) {
-        Log(env_, options_->info_log,
+        Log(options_->info_log,
             "Expanding@%d %d+%d to %d+%d\n",
             level,
             int(c->inputs_[0].size()),
@@ -1147,7 +1147,7 @@ void VersionSet::SetupOtherInputs(Compaction* c) {
   }
 
   if (false) {
-    Log(env_, options_->info_log, "Compacting %d '%s' .. '%s'",
+    Log(options_->info_log, "Compacting %d '%s' .. '%s'",
         level,
         EscapeString(smallest.Encode()).c_str(),
         EscapeString(largest.Encode()).c_str());
diff --git a/include/leveldb/env.h b/include/leveldb/env.h
index 39f6a1a..bf51008 100644
--- a/include/leveldb/env.h
+++ b/include/leveldb/env.h
@@ -22,6 +22,7 @@
 namespace leveldb {
 
 class FileLock;
+class Logger;
 class RandomAccessFile;
 class SequentialFile;
 class Slice;
@@ -134,8 +135,8 @@ class Env {
   // same directory.
   virtual Status GetTestDirectory(std::string* path) = 0;
 
-  // Write an entry to the log file with the specified format.
-  virtual void Logv(WritableFile* log, const char* format, va_list ap) = 0;
+  // Create and return a log file for storing informational messages.
+  virtual Status NewLogger(const std::string& fname, Logger** result) = 0;
 
   // Returns the number of micro-seconds since some fixed point in time. Only
   // useful for computing deltas of time.
@@ -210,6 +211,22 @@ class WritableFile {
   void operator=(const WritableFile&);
 };
 
+// An interface for writing log messages.
+class Logger {
+ public:
+  Logger() { }
+  virtual ~Logger();
+
+  // Write an entry to the log file with the specified format.
+  virtual void Logv(const char* format, va_list ap) = 0;
+
+ private:
+  // No copying allowed
+  Logger(const Logger&);
+  void operator=(const Logger&);
+};
+
+
 // Identifies a locked file.
 class FileLock {
  public:
@@ -222,9 +239,9 @@ class FileLock {
 };
 
 // Log the specified data to *info_log if info_log is non-NULL.
-extern void Log(Env* env, WritableFile* info_log, const char* format, ...)
+extern void Log(Logger* info_log, const char* format, ...)
 #   if defined(__GNUC__) || defined(__clang__)
-    __attribute__((__format__ (__printf__, 3, 4)))
+    __attribute__((__format__ (__printf__, 2, 3)))
 #   endif
     ;
 
@@ -284,8 +301,8 @@ class EnvWrapper : public Env {
   virtual Status GetTestDirectory(std::string* path) {
     return target_->GetTestDirectory(path);
   }
-  virtual void Logv(WritableFile* log, const char* format, va_list ap) {
-    return target_->Logv(log, format, ap);
+  virtual Status NewLogger(const std::string& fname, Logger** result) {
+    return target_->NewLogger(fname, result);
   }
   uint64_t NowMicros() {
     return target_->NowMicros();
diff --git a/include/leveldb/options.h b/include/leveldb/options.h
index 0d4f6cd..381f228 100644
--- a/include/leveldb/options.h
+++ b/include/leveldb/options.h
@@ -12,8 +12,8 @@ namespace leveldb {
 class Cache;
 class Comparator;
 class Env;
+class Logger;
 class Snapshot;
-class WritableFile;
 
 // DB contents are stored in a set of blocks, each of which holds a
 // sequence of key,value pairs.  Each block may be compressed before
@@ -61,10 +61,10 @@ struct Options {
   Env* env;
 
   // Any internal progress/error information generated by the db will
-  // be to written to info_log if it is non-NULL, or to a file stored
+  // be written to info_log if it is non-NULL, or to a file stored
   // in the same directory as the DB contents if info_log is NULL.
   // Default: NULL
-  WritableFile* info_log;
+  Logger* info_log;
 
   // -------------------
   // Parameters that affect performance
diff --git a/port/atomic_pointer.h b/port/atomic_pointer.h
index c618778..c20b1bd 100644
--- a/port/atomic_pointer.h
+++ b/port/atomic_pointer.h
@@ -48,9 +48,8 @@ namespace port {
 // http://msdn.microsoft.com/en-us/library/ms684208(v=vs.85).aspx
 #define LEVELDB_HAVE_MEMORY_BARRIER
 
-// Gcc and Sun Studio on x86
-#elif defined(ARCH_CPU_X86_FAMILY) && \
-    (defined(__GNUC__) || defined(__SUNPRO_CC))
+// Gcc on x86
+#elif defined(ARCH_CPU_X86_FAMILY) && defined(__GNUC__)
 inline void MemoryBarrier() {
   // See http://gcc.gnu.org/ml/gcc/2003-04/msg01180.html for a discussion on
   // this idiom. Also see http://en.wikipedia.org/wiki/Memory_ordering.
@@ -58,6 +57,15 @@ inline void MemoryBarrier() {
 }
 #define LEVELDB_HAVE_MEMORY_BARRIER
 
+// Sun Studio
+#elif defined(ARCH_CPU_X86_FAMILY) && defined(__SUNPRO_CC)
+inline void MemoryBarrier() {
+  // See http://gcc.gnu.org/ml/gcc/2003-04/msg01180.html for a discussion on
+  // this idiom. Also see http://en.wikipedia.org/wiki/Memory_ordering.
+  asm volatile("" : : : "memory");
+}
+#define LEVELDB_HAVE_MEMORY_BARRIER
+
 // Mac OS
 #elif defined(OS_MACOSX)
 inline void MemoryBarrier() {
diff --git a/port/port_android.h b/port/port_android.h
index 13df9c9..d68b6c0 100644
--- a/port/port_android.h
+++ b/port/port_android.h
@@ -126,10 +126,16 @@ inline bool Snappy_Compress(
 }
 
 // TODO(gabor): Implement uncompress
+inline bool Snappy_GetUncompressedLength(const char* input, size_t length,
+                                         size_t* result) {
+  return false;
+}
+
+// TODO(gabor): Implement uncompress
 inline bool Snappy_Uncompress(
     const char* input_data,
     size_t input_length,
-    std::string* output) {
+    char* output) {
   return false;
 }
 
diff --git a/port/port_chromium.cc b/port/port_chromium.cc
index 2ab49b9..7f6de92 100644
--- a/port/port_chromium.cc
+++ b/port/port_chromium.cc
@@ -62,15 +62,19 @@ bool Snappy_Compress(const char* input, size_t input_length,
 #endif
 }
 
+bool Snappy_GetUncompressedLength(const char* input, size_t length,
+                                  size_t* result) {
+#if defined(USE_SNAPPY)
+  return snappy::GetUncompressedLength(input_data, input_length, result);
+#else
+  return false;
+#endif
+}
+
 bool Snappy_Uncompress(const char* input_data, size_t input_length,
-                       std::string* output) {
+                       char* output) {
 #if defined(USE_SNAPPY)
-  size_t ulength;
-  if (!snappy::GetUncompressedLength(input_data, input_length, &ulength)) {
-    return false;
-  }
-  output->resize(ulength);
-  return snappy::RawUncompress(input_data, input_length, &(*output)[0]);
+  return snappy::RawUncompress(input_data, input_length, output);
 #else
   return false;
 #endif
diff --git a/port/port_chromium.h b/port/port_chromium.h
index 1851e6e..feecd5b 100644
--- a/port/port_chromium.h
+++ b/port/port_chromium.h
@@ -84,8 +84,10 @@ class AtomicPointer {
 
 bool Snappy_Compress(const char* input, size_t input_length,
                      std::string* output);
+bool Snappy_GetUncompressedLength(const char* input, size_t length,
+                                  size_t* result);
 bool Snappy_Uncompress(const char* input_data, size_t input_length,
-                       std::string* output);
+                       char* output);
 
 inline bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg) {
   return false;
diff --git a/port/port_example.h b/port/port_example.h
index 8a624f3..6bd9b49 100644
--- a/port/port_example.h
+++ b/port/port_example.h
@@ -96,11 +96,21 @@ class AtomicPointer {
 extern bool Snappy_Compress(const char* input, size_t input_length,
                             std::string* output);
 
+// If input[0,input_length-1] looks like a valid snappy compressed
+// buffer, store the size of the uncompressed data in *result and
+// return true.  Else return false.
+extern bool Snappy_GetUncompressedLength(const char* input, size_t length,
+                                         size_t* result);
+
 // Attempt to snappy uncompress input[0,input_length-1] into *output.
 // Returns true if successful, false if the input is invalid lightweight
 // compressed data.
+//
+// REQUIRES: at least the first "n" bytes of output[] must be writable
+// where "n" is the result of a successful call to
+// Snappy_GetUncompressedLength.
 extern bool Snappy_Uncompress(const char* input_data, size_t input_length,
-                              std::string* output);
+                              char* output);
 
 // ------------------ Miscellaneous -------------------
 
diff --git a/port/port_posix.h b/port/port_posix.h
index 2995026..ef01de3 100644
--- a/port/port_posix.h
+++ b/port/port_posix.h
@@ -80,12 +80,12 @@ class CondVar {
   Mutex* mu_;
 };
 
-inline bool Snappy_Compress(const char* input, size_t input_length,
+inline bool Snappy_Compress(const char* input, size_t length,
                             ::std::string* output) {
 #ifdef SNAPPY
-  output->resize(snappy::MaxCompressedLength(input_length));
+  output->resize(snappy::MaxCompressedLength(length));
   size_t outlen;
-  snappy::RawCompress(input, input_length, &(*output)[0], &outlen);
+  snappy::RawCompress(input, length, &(*output)[0], &outlen);
   output->resize(outlen);
   return true;
 #endif
@@ -93,18 +93,22 @@ inline bool Snappy_Compress(const char* input, size_t input_length,
   return false;
 }
 
-inline bool Snappy_Uncompress(const char* input_data, size_t input_length,
-                              ::std::string* output) {
+inline bool Snappy_GetUncompressedLength(const char* input, size_t length,
+                                         size_t* result) {
 #ifdef SNAPPY
-  size_t ulength;
-  if (!snappy::GetUncompressedLength(input_data, input_length, &ulength)) {
-    return false;
-  }
-  output->resize(ulength);
-  return snappy::RawUncompress(input_data, input_length, &(*output)[0]);
+  return snappy::GetUncompressedLength(input, length, result);
+#else
+  return false;
 #endif
+}
 
+inline bool Snappy_Uncompress(const char* input, size_t length,
+                              char* output) {
+#ifdef SNAPPY
+  return snappy::RawUncompress(input, length, output);
+#else
   return false;
+#endif
 }
 
 inline bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg) {
diff --git a/table/format.cc b/table/format.cc
index 63971db..ba7838c 100644
--- a/table/format.cc
+++ b/table/format.cc
@@ -107,16 +107,20 @@ Status ReadBlock(RandomAccessFile* file,
       // Ok
       break;
     case kSnappyCompression: {
-      std::string decompressed;
-      if (!port::Snappy_Uncompress(data, n, &decompressed)) {
+      size_t ulength = 0;
+      if (!port::Snappy_GetUncompressedLength(data, n, &ulength)) {
         delete[] buf;
-        s = Status::Corruption("corrupted compressed block contents");
-        return s;
+        return Status::Corruption("corrupted compressed block contents");
       }
-      delete[] buf;     // Done with uncompressed data
-      buf = new char[decompressed.size()];
-      memcpy(buf, decompressed.data(), decompressed.size());
-      n = decompressed.size();
+      char* ubuf = new char[ulength];
+      if (!port::Snappy_Uncompress(data, n, ubuf)) {
+        delete[] buf;
+        delete[] ubuf;
+        return Status::Corruption("corrupted compressed block contents");
+      }
+      delete[] buf;
+      buf = ubuf;
+      n = ulength;
       break;
     }
     default:
diff --git a/util/env.cc b/util/env.cc
index e5297e7..79e493e 100644
--- a/util/env.cc
+++ b/util/env.cc
@@ -18,14 +18,19 @@ RandomAccessFile::~RandomAccessFile() {
 WritableFile::~WritableFile() {
 }
 
+Logger::~Logger() {
+}
+
 FileLock::~FileLock() {
 }
 
-void Log(Env* env, WritableFile* info_log, const char* format, ...) {
-  va_list ap;
-  va_start(ap, format);
-  env->Logv(info_log, format, ap);
-  va_end(ap);
+void Log(Logger* info_log, const char* format, ...) {
+  if (info_log != NULL) {
+    va_list ap;
+    va_start(ap, format);
+    info_log->Logv(format, ap);
+    va_end(ap);
+  }
 }
 
 Status WriteStringToFile(Env* env, const Slice& data,
diff --git a/util/env_chromium.cc b/util/env_chromium.cc
index 1af525a..975386b 100644
--- a/util/env_chromium.cc
+++ b/util/env_chromium.cc
@@ -23,6 +23,7 @@
 #include "leveldb/slice.h"
 #include "port/port.h"
 #include "util/logging.h"
+#include "util/posix_logger.h"
 
 #if defined(OS_WIN)
 #include <io.h>
@@ -406,9 +407,8 @@ class ChromiumEnv : public Env {
     return Status::OK();
   }
 
-  virtual void Logv(WritableFile* info_log, const char* format, va_list ap) {
-    // TODO(jorlow): We may want to just use Chromium's built in logging.
-
+  // TODO(user,user): Use Chromium's built-in logging?
+  static uint64_t gettid() {
     uint64_t thread_id = 0;
     // Coppied from base/logging.cc.
 #if defined(OS_WIN)
@@ -422,65 +422,17 @@ class ChromiumEnv : public Env {
     pthread_t tid = pthread_self();
     memcpy(&thread_id, &tid, min(sizeof(r), sizeof(tid)));
 #endif
+    return thread_id;
+  }
 
-    // We try twice: the first time with a fixed-size stack allocated buffer,
-    // and the second time with a much larger dynamically allocated buffer.
-    char buffer[500];
-    for (int iter = 0; iter < 2; iter++) {
-      char* base;
-      int bufsize;
-      if (iter == 0) {
-        bufsize = sizeof(buffer);
-        base = buffer;
-      } else {
-        bufsize = 30000;
-        base = new char[bufsize];
-      }
-      char* p = base;
-      char* limit = base + bufsize;
-
-      ::base::Time::Exploded t;
-      ::base::Time::Now().LocalExplode(&t);
-      p += snprintf(p, limit - p,
-                    "%04d/%02d/%02d-%02d:%02d:%02d.%06d %llx ",
-                    t.year,
-                    t.month,
-                    t.day_of_month,
-                    t.hour,
-                    t.minute,
-                    t.second,
-                    static_cast<int>(t.millisecond) * 1000,
-                    static_cast<long long unsigned int>(thread_id));
-
-      // Print the message
-      if (p < limit) {
-        va_list backup_ap;
-        va_copy(backup_ap, ap);
-        p += vsnprintf(p, limit - p, format, backup_ap);
-        va_end(backup_ap);
-      }
-
-      // Truncate to available space if necessary
-      if (p >= limit) {
-        if (iter == 0) {
-          continue;       // Try again with larger buffer
-        } else {
-          p = limit - 1;
-        }
-      }
-
-      // Add newline if necessary
-      if (p == base || p[-1] != '\n') {
-        *p++ = '\n';
-      }
-
-      assert(p <= limit);
-      info_log->Append(Slice(base, p - base));
-      info_log->Flush();
-      if (base != buffer) {
-        delete[] base;
-      }
-      break;
+  virtual Status NewLogger(const std::string& fname, Logger** result) {
+    FILE* f = fopen(fname.c_str(), "w");
+    if (f == NULL) {
+      *result = NULL;
+      return Status::IOError(fname, strerror(errno));
+    } else {
+      *result = new PosixLogger(f, &ChromiumEnv::gettid);
+      return Status::OK();
     }
   }
 
diff --git a/util/env_posix.cc b/util/env_posix.cc
index 46723e2..5127c89 100644
--- a/util/env_posix.cc
+++ b/util/env_posix.cc
@@ -23,6 +23,7 @@
 #include "leveldb/slice.h"
 #include "port/port.h"
 #include "util/logging.h"
+#include "util/posix_logger.h"
 
 namespace leveldb {
 
@@ -427,72 +428,21 @@ class PosixEnv : public Env {
     return Status::OK();
   }
 
-  virtual void Logv(WritableFile* info_log, const char* format, va_list ap) {
+  static uint64_t gettid() {
     pthread_t tid = pthread_self();
     uint64_t thread_id = 0;
     memcpy(&thread_id, &tid, std::min(sizeof(thread_id), sizeof(tid)));
+    return thread_id;
+  }
 
-    // We try twice: the first time with a fixed-size stack allocated buffer,
-    // and the second time with a much larger dynamically allocated buffer.
-    char buffer[500];
-    for (int iter = 0; iter < 2; iter++) {
-      char* base;
-      int bufsize;
-      if (iter == 0) {
-        bufsize = sizeof(buffer);
-        base = buffer;
-      } else {
-        bufsize = 30000;
-        base = new char[bufsize];
-      }
-      char* p = base;
-      char* limit = base + bufsize;
-
-      struct timeval now_tv;
-      gettimeofday(&now_tv, NULL);
-      const time_t seconds = now_tv.tv_sec;
-      struct tm t;
-      localtime_r(&seconds, &t);
-      p += snprintf(p, limit - p,
-                    "%04d/%02d/%02d-%02d:%02d:%02d.%06d %llx ",
-                    t.tm_year + 1900,
-                    t.tm_mon + 1,
-                    t.tm_mday,
-                    t.tm_hour,
-                    t.tm_min,
-                    t.tm_sec,
-                    static_cast<int>(now_tv.tv_usec),
-                    static_cast<long long unsigned int>(thread_id));
-
-      // Print the message
-      if (p < limit) {
-        va_list backup_ap;
-        va_copy(backup_ap, ap);
-        p += vsnprintf(p, limit - p, format, backup_ap);
-        va_end(backup_ap);
-      }
-
-      // Truncate to available space if necessary
-      if (p >= limit) {
-        if (iter == 0) {
-          continue;       // Try again with larger buffer
-        } else {
-          p = limit - 1;
-        }
-      }
-
-      // Add newline if necessary
-      if (p == base || p[-1] != '\n') {
-        *p++ = '\n';
-      }
-
-      assert(p <= limit);
-      info_log->Append(Slice(base, p - base));
-      info_log->Flush();
-      if (base != buffer) {
-        delete[] base;
-      }
-      break;
+  virtual Status NewLogger(const std::string& fname, Logger** result) {
+    FILE* f = fopen(fname.c_str(), "w");
+    if (f == NULL) {
+      *result = NULL;
+      return IOError(fname, errno);
+    } else {
+      *result = new PosixLogger(f, &PosixEnv::gettid);
+      return Status::OK();
     }
   }
 
diff --git a/util/posix_logger.h b/util/posix_logger.h
new file mode 100644
index 0000000..0dbdeaa
--- /dev/null
+++ b/util/posix_logger.h
@@ -0,0 +1,97 @@
+// Copyright 2011 Google Inc. All Rights Reserved.
+// Author: sanjay@google.com (Sanjay Ghemawat)
+//
+// Logger implementation that can be shared by all environments
+// where enough posix functionality is available.
+
+#ifndef STORAGE_LEVELDB_UTIL_POSIX_LOGGER_H_
+#define STORAGE_LEVELDB_UTIL_POSIX_LOGGER_H_
+
+#include <algorithm>
+#include <stdio.h>
+#include <sys/time.h>
+#include <time.h>
+#include "leveldb/env.h"
+
+namespace leveldb {
+
+class PosixLogger : public Logger {
+ private:
+  FILE* file_;
+  uint64_t (*gettid_)();  // Return the thread id for the current thread
+ public:
+  PosixLogger(FILE* f, uint64_t (*gettid)()) : file_(f), gettid_(gettid) { }
+  virtual ~PosixLogger() {
+    fclose(file_);
+  }
+  virtual void Logv(const char* format, va_list ap) {
+    const uint64_t thread_id = (*gettid_)();
+
+    // We try twice: the first time with a fixed-size stack allocated buffer,
+    // and the second time with a much larger dynamically allocated buffer.
+    char buffer[500];
+    for (int iter = 0; iter < 2; iter++) {
+      char* base;
+      int bufsize;
+      if (iter == 0) {
+        bufsize = sizeof(buffer);
+        base = buffer;
+      } else {
+        bufsize = 30000;
+        base = new char[bufsize];
+      }
+      char* p = base;
+      char* limit = base + bufsize;
+
+      struct timeval now_tv;
+      gettimeofday(&now_tv, NULL);
+      const time_t seconds = now_tv.tv_sec;
+      struct tm t;
+      localtime_r(&seconds, &t);
+      p += snprintf(p, limit - p,
+                    "%04d/%02d/%02d-%02d:%02d:%02d.%06d %llx ",
+                    t.tm_year + 1900,
+                    t.tm_mon + 1,
+                    t.tm_mday,
+                    t.tm_hour,
+                    t.tm_min,
+                    t.tm_sec,
+                    static_cast<int>(now_tv.tv_usec),
+                    static_cast<long long unsigned int>(thread_id));
+
+      // Print the message
+      if (p < limit) {
+        va_list backup_ap;
+        va_copy(backup_ap, ap);
+        p += vsnprintf(p, limit - p, format, backup_ap);
+        va_end(backup_ap);
+      }
+
+      // Truncate to available space if necessary
+      if (p >= limit) {
+        if (iter == 0) {
+          continue;       // Try again with larger buffer
+        } else {
+          p = limit - 1;
+        }
+      }
+
+      // Add newline if necessary
+      if (p == base || p[-1] != '\n') {
+        *p++ = '\n';
+      }
+
+      assert(p <= limit);
+      fwrite(base, 1, p - base, file_);
+      fflush(file_);
+      if (base != buffer) {
+        delete[] base;
+      }
+      break;
+    }
+  }
+};
+
+}
+
+#endif  // STORAGE_LEVELDB_UTIL_POSIX_LOGGER_H_