Version 3.0.2.

src/log-utils.cc

Index: src/log-utils.cc
diff --git a/src/log-utils.cc b/src/log-utils.cc
index c7b75679ea9ba2acb6f54b21b03c7a34610f4908..d6d8754b23e1a38e0bd1d5b583124464d8f54bae 100644
--- a/src/log-utils.cc
+++ b/src/log-utils.cc
@@ -273,7 +273,29 @@ void LogMessageBuilder::Append(String* str) {
 
 
 void LogMessageBuilder::AppendAddress(Address addr) {
-  Append("0x%" V8PRIxPTR, 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);
+  }
 }
 
 
@@ -321,6 +343,24 @@ void LogMessageBuilder::AppendStringPart(const char* str, int len) {
 }
 
 
+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_);
@@ -329,6 +369,145 @@ void LogMessageBuilder::WriteToLogFile() {
   }
 }
 
+
+// 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 = static_cast<int>(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(static_cast<int>(unchanged_len + best.backref_size));
+  }
+  return true;
+}
+
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal