diff --git a/src/log-utils.cc b/src/log-utils.cc
new file mode 100644
index 0000000..f327a0a
--- /dev/null
+++ b/src/log-utils.cc
@@ -0,0 +1,503 @@
+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "v8.h"
+
+#include "log-utils.h"
+
+namespace v8 {
+namespace internal {
+
+#ifdef ENABLE_LOGGING_AND_PROFILING
+
+LogDynamicBuffer::LogDynamicBuffer(
+    int block_size, int max_size, const char* seal, int seal_size)
+    : block_size_(block_size),
+      max_size_(max_size - (max_size % block_size_)),
+      seal_(seal),
+      seal_size_(seal_size),
+      blocks_(max_size_ / block_size_ + 1),
+      write_pos_(0), block_index_(0), block_write_pos_(0), is_sealed_(false) {
+  ASSERT(BlocksCount() > 0);
+  AllocateBlock(0);
+  for (int i = 1; i < BlocksCount(); ++i) {
+    blocks_[i] = NULL;
+  }
+}
+
+
+LogDynamicBuffer::~LogDynamicBuffer() {
+  for (int i = 0; i < BlocksCount(); ++i) {
+    DeleteArray(blocks_[i]);
+  }
+}
+
+
+int LogDynamicBuffer::Read(int from_pos, char* dest_buf, int buf_size) {
+  if (buf_size == 0) return 0;
+  int read_pos = from_pos;
+  int block_read_index = BlockIndex(from_pos);
+  int block_read_pos = PosInBlock(from_pos);
+  int dest_buf_pos = 0;
+  // Read until dest_buf is filled, or write_pos_ encountered.
+  while (read_pos < write_pos_ && dest_buf_pos < buf_size) {
+    const int read_size = Min(write_pos_ - read_pos,
+        Min(buf_size - dest_buf_pos, block_size_ - block_read_pos));
+    memcpy(dest_buf + dest_buf_pos,
+           blocks_[block_read_index] + block_read_pos, read_size);
+    block_read_pos += read_size;
+    dest_buf_pos += read_size;
+    read_pos += read_size;
+    if (block_read_pos == block_size_) {
+      block_read_pos = 0;
+      ++block_read_index;
+    }
+  }
+  return dest_buf_pos;
+}
+
+
+int LogDynamicBuffer::Seal() {
+  WriteInternal(seal_, seal_size_);
+  is_sealed_ = true;
+  return 0;
+}
+
+
+int LogDynamicBuffer::Write(const char* data, int data_size) {
+  if (is_sealed_) {
+    return 0;
+  }
+  if ((write_pos_ + data_size) <= (max_size_ - seal_size_)) {
+    return WriteInternal(data, data_size);
+  } else {
+    return Seal();
+  }
+}
+
+
+int LogDynamicBuffer::WriteInternal(const char* data, int data_size) {
+  int data_pos = 0;
+  while (data_pos < data_size) {
+    const int write_size =
+        Min(data_size - data_pos, block_size_ - block_write_pos_);
+    memcpy(blocks_[block_index_] + block_write_pos_, data + data_pos,
+           write_size);
+    block_write_pos_ += write_size;
+    data_pos += write_size;
+    if (block_write_pos_ == block_size_) {
+      block_write_pos_ = 0;
+      AllocateBlock(++block_index_);
+    }
+  }
+  write_pos_ += data_size;
+  return data_size;
+}
+
+
+bool Log::is_stopped_ = false;
+Log::WritePtr Log::Write = NULL;
+FILE* Log::output_handle_ = NULL;
+LogDynamicBuffer* Log::output_buffer_ = NULL;
+// Must be the same message as in Logger::PauseProfiler.
+const char* Log::kDynamicBufferSeal = "profiler,\"pause\"\n";
+Mutex* Log::mutex_ = NULL;
+char* Log::message_buffer_ = NULL;
+
+
+void Log::Init() {
+  mutex_ = OS::CreateMutex();
+  message_buffer_ = NewArray<char>(kMessageBufferSize);
+}
+
+
+void Log::OpenStdout() {
+  ASSERT(!IsEnabled());
+  output_handle_ = stdout;
+  Write = WriteToFile;
+  Init();
+}
+
+
+void Log::OpenFile(const char* name) {
+  ASSERT(!IsEnabled());
+  output_handle_ = OS::FOpen(name, OS::LogFileOpenMode);
+  Write = WriteToFile;
+  Init();
+}
+
+
+void Log::OpenMemoryBuffer() {
+  ASSERT(!IsEnabled());
+  output_buffer_ = new LogDynamicBuffer(
+      kDynamicBufferBlockSize, kMaxDynamicBufferSize,
+      kDynamicBufferSeal, strlen(kDynamicBufferSeal));
+  Write = WriteToMemory;
+  Init();
+}
+
+
+void Log::Close() {
+  if (Write == WriteToFile) {
+    if (output_handle_ != NULL) fclose(output_handle_);
+    output_handle_ = NULL;
+  } else if (Write == WriteToMemory) {
+    delete output_buffer_;
+    output_buffer_ = NULL;
+  } else {
+    ASSERT(Write == NULL);
+  }
+  Write = NULL;
+
+  DeleteArray(message_buffer_);
+  message_buffer_ = NULL;
+
+  delete mutex_;
+  mutex_ = NULL;
+
+  is_stopped_ = false;
+}
+
+
+int Log::GetLogLines(int from_pos, char* dest_buf, int max_size) {
+  if (Write != WriteToMemory) return 0;
+  ASSERT(output_buffer_ != NULL);
+  ASSERT(from_pos >= 0);
+  ASSERT(max_size >= 0);
+  int actual_size = output_buffer_->Read(from_pos, dest_buf, max_size);
+  ASSERT(actual_size <= max_size);
+  if (actual_size == 0) return 0;
+
+  // Find previous log line boundary.
+  char* end_pos = dest_buf + actual_size - 1;
+  while (end_pos >= dest_buf && *end_pos != '\n') --end_pos;
+  actual_size = end_pos - dest_buf + 1;
+  ASSERT(actual_size <= max_size);
+  return actual_size;
+}
+
+
+LogMessageBuilder::WriteFailureHandler
+    LogMessageBuilder::write_failure_handler = NULL;
+
+
+LogMessageBuilder::LogMessageBuilder(): sl(Log::mutex_), pos_(0) {
+  ASSERT(Log::message_buffer_ != NULL);
+}
+
+
+void LogMessageBuilder::Append(const char* format, ...) {
+  Vector<char> buf(Log::message_buffer_ + pos_,
+                   Log::kMessageBufferSize - pos_);
+  va_list args;
+  va_start(args, format);
+  AppendVA(format, args);
+  va_end(args);
+  ASSERT(pos_ <= Log::kMessageBufferSize);
+}
+
+
+void LogMessageBuilder::AppendVA(const char* format, va_list args) {
+  Vector<char> buf(Log::message_buffer_ + pos_,
+                   Log::kMessageBufferSize - pos_);
+  int result = v8::internal::OS::VSNPrintF(buf, format, args);
+
+  // Result is -1 if output was truncated.
+  if (result >= 0) {
+    pos_ += result;
+  } else {
+    pos_ = Log::kMessageBufferSize;
+  }
+  ASSERT(pos_ <= Log::kMessageBufferSize);
+}
+
+
+void LogMessageBuilder::Append(const char c) {
+  if (pos_ < Log::kMessageBufferSize) {
+    Log::message_buffer_[pos_++] = c;
+  }
+  ASSERT(pos_ <= Log::kMessageBufferSize);
+}
+
+
+void LogMessageBuilder::Append(String* str) {
+  AssertNoAllocation no_heap_allocation;  // Ensure string stay valid.
+  int length = str->length();
+  for (int i = 0; i < length; i++) {
+    Append(static_cast<char>(str->Get(i)));
+  }
+}
+
+
+void LogMessageBuilder::AppendAddress(Address addr) {
+  static Address last_address_ = NULL;
+  AppendAddress(addr, last_address_);
+  last_address_ = addr;
+}
+
+
+void LogMessageBuilder::AppendAddress(Address addr, Address bias) {
+  if (!FLAG_compress_log) {
+    Append("0x%" V8PRIxPTR, addr);
+  } else if (bias == NULL) {
+    Append("%" V8PRIxPTR, addr);
+  } else {
+    uintptr_t delta;
+    char sign;
+    if (addr >= bias) {
+      delta = addr - bias;
+      sign = '+';
+    } else {
+      delta = bias - addr;
+      sign = '-';
+    }
+    Append("%c%" V8PRIxPTR, sign, delta);
+  }
+}
+
+
+void LogMessageBuilder::AppendDetailed(String* str, bool show_impl_info) {
+  AssertNoAllocation no_heap_allocation;  // Ensure string stay valid.
+  int len = str->length();
+  if (len > 0x1000)
+    len = 0x1000;
+  if (show_impl_info) {
+    Append(str->IsAsciiRepresentation() ? 'a' : '2');
+    if (StringShape(str).IsExternal())
+      Append('e');
+    if (StringShape(str).IsSymbol())
+      Append('#');
+    Append(":%i:", str->length());
+  }
+  for (int i = 0; i < len; i++) {
+    uc32 c = str->Get(i);
+    if (c > 0xff) {
+      Append("\\u%04x", c);
+    } else if (c < 32 || c > 126) {
+      Append("\\x%02x", c);
+    } else if (c == ',') {
+      Append("\\,");
+    } else if (c == '\\') {
+      Append("\\\\");
+    } else {
+      Append("%lc", c);
+    }
+  }
+}
+
+
+void LogMessageBuilder::AppendStringPart(const char* str, int len) {
+  if (pos_ + len > Log::kMessageBufferSize) {
+    len = Log::kMessageBufferSize - pos_;
+    ASSERT(len >= 0);
+    if (len == 0) return;
+  }
+  Vector<char> buf(Log::message_buffer_ + pos_,
+                   Log::kMessageBufferSize - pos_);
+  OS::StrNCpy(buf, str, len);
+  pos_ += len;
+  ASSERT(pos_ <= Log::kMessageBufferSize);
+}
+
+
+bool LogMessageBuilder::StoreInCompressor(LogRecordCompressor* compressor) {
+  return compressor->Store(Vector<const char>(Log::message_buffer_, pos_));
+}
+
+
+bool LogMessageBuilder::RetrieveCompressedPrevious(
+    LogRecordCompressor* compressor, const char* prefix) {
+  pos_ = 0;
+  if (prefix[0] != '\0') Append(prefix);
+  Vector<char> prev_record(Log::message_buffer_ + pos_,
+                           Log::kMessageBufferSize - pos_);
+  const bool has_prev = compressor->RetrievePreviousCompressed(&prev_record);
+  if (!has_prev) return false;
+  pos_ += prev_record.length();
+  return true;
+}
+
+
+void LogMessageBuilder::WriteToLogFile() {
+  ASSERT(pos_ <= Log::kMessageBufferSize);
+  const int written = Log::Write(Log::message_buffer_, pos_);
+  if (written != pos_ && write_failure_handler != NULL) {
+    write_failure_handler();
+  }
+}
+
+
+void LogMessageBuilder::WriteCStringToLogFile(const char* str) {
+  const int len = strlen(str);
+  const int written = Log::Write(str, len);
+  if (written != len && write_failure_handler != NULL) {
+    write_failure_handler();
+  }
+}
+
+
+// Formatting string for back references to the whole line. E.g. "#2" means
+// "the second line above".
+const char* LogRecordCompressor::kLineBackwardReferenceFormat = "#%d";
+
+// Formatting string for back references. E.g. "#2:10" means
+// "the second line above, start from char 10 (0-based)".
+const char* LogRecordCompressor::kBackwardReferenceFormat = "#%d:%d";
+
+
+LogRecordCompressor::~LogRecordCompressor() {
+  for (int i = 0; i < buffer_.length(); ++i) {
+    buffer_[i].Dispose();
+  }
+}
+
+
+static int GetNumberLength(int number) {
+  ASSERT(number >= 0);
+  ASSERT(number < 10000);
+  if (number < 10) return 1;
+  if (number < 100) return 2;
+  if (number < 1000) return 3;
+  return 4;
+}
+
+
+int LogRecordCompressor::GetBackwardReferenceSize(int distance, int pos) {
+  // See kLineBackwardReferenceFormat and kBackwardReferenceFormat.
+  return pos == 0 ? GetNumberLength(distance) + 1
+      : GetNumberLength(distance) + GetNumberLength(pos) + 2;
+}
+
+
+void LogRecordCompressor::PrintBackwardReference(Vector<char> dest,
+                                                 int distance,
+                                                 int pos) {
+  if (pos == 0) {
+    OS::SNPrintF(dest, kLineBackwardReferenceFormat, distance);
+  } else {
+    OS::SNPrintF(dest, kBackwardReferenceFormat, distance, pos);
+  }
+}
+
+
+bool LogRecordCompressor::Store(const Vector<const char>& record) {
+  // Check if the record is the same as the last stored one.
+  if (curr_ != -1) {
+    Vector<const char>& curr = buffer_[curr_];
+    if (record.length() == curr.length()
+        && strncmp(record.start(), curr.start(), record.length()) == 0) {
+      return false;
+    }
+  }
+  // buffer_ is circular.
+  prev_ = curr_++;
+  curr_ %= buffer_.length();
+  Vector<char> record_copy = Vector<char>::New(record.length());
+  memcpy(record_copy.start(), record.start(), record.length());
+  buffer_[curr_].Dispose();
+  buffer_[curr_] =
+      Vector<const char>(record_copy.start(), record_copy.length());
+  return true;
+}
+
+
+bool LogRecordCompressor::RetrievePreviousCompressed(
+    Vector<char>* prev_record) {
+  if (prev_ == -1) return false;
+
+  int index = prev_;
+  // Distance from prev_.
+  int distance = 0;
+  // Best compression result among records in the buffer.
+  struct {
+    intptr_t truncated_len;
+    int distance;
+    int copy_from_pos;
+    int backref_size;
+  } best = {-1, 0, 0, 0};
+  Vector<const char>& prev = buffer_[prev_];
+  const char* const prev_start = prev.start();
+  const char* const prev_end = prev.start() + prev.length();
+  do {
+    // We're moving backwards until we reach the current record.
+    // Remember that buffer_ is circular.
+    if (--index == -1) index = buffer_.length() - 1;
+    ++distance;
+    if (index == curr_) break;
+
+    Vector<const char>& data = buffer_[index];
+    if (data.start() == NULL) break;
+    const char* const data_end = data.start() + data.length();
+    const char* prev_ptr = prev_end;
+    const char* data_ptr = data_end;
+    // Compare strings backwards, stop on the last matching character.
+    while (prev_ptr != prev_start && data_ptr != data.start()
+          && *(prev_ptr - 1) == *(data_ptr - 1)) {
+      --prev_ptr;
+      --data_ptr;
+    }
+    const intptr_t truncated_len = prev_end - prev_ptr;
+    const int copy_from_pos = data_ptr - data.start();
+    // Check if the length of compressed tail is enough.
+    if (truncated_len <= kMaxBackwardReferenceSize
+        && truncated_len <= GetBackwardReferenceSize(distance, copy_from_pos)) {
+      continue;
+    }
+
+    // Record compression results.
+    if (truncated_len > best.truncated_len) {
+      best.truncated_len = truncated_len;
+      best.distance = distance;
+      best.copy_from_pos = copy_from_pos;
+      best.backref_size = GetBackwardReferenceSize(distance, copy_from_pos);
+    }
+  } while (true);
+
+  if (best.distance == 0) {
+    // Can't compress the previous record. Return as is.
+    ASSERT(prev_record->length() >= prev.length());
+    memcpy(prev_record->start(), prev.start(), prev.length());
+    prev_record->Truncate(prev.length());
+  } else {
+    // Copy the uncompressible part unchanged.
+    const intptr_t unchanged_len = prev.length() - best.truncated_len;
+    // + 1 for '\0'.
+    ASSERT(prev_record->length() >= unchanged_len + best.backref_size + 1);
+    memcpy(prev_record->start(), prev.start(), unchanged_len);
+    // Append the backward reference.
+    Vector<char> backref(
+        prev_record->start() + unchanged_len, best.backref_size + 1);
+    PrintBackwardReference(backref, best.distance, best.copy_from_pos);
+    ASSERT(strlen(backref.start()) - best.backref_size == 0);
+    prev_record->Truncate(unchanged_len + best.backref_size);
+  }
+  return true;
+}
+
+#endif  // ENABLE_LOGGING_AND_PROFILING
+
+} }  // namespace v8::internal