Per isolate Log with block support

runtime/vm/log.cc

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include "vm/log.h"
+
+#include "vm/flags.h"
+#include "vm/thread.h"
+
+namespace dart {
+
+DEFINE_FLAG(bool, force_log_flush, false, "Always flush log messages.");
+
+Log::Log(LogPrinter printer)
+    : printer_(printer),
+      manual_flush_(0),
+      buffer_(0) {
+}
+
+
+void Log::Print(const char* format, ...) {
+  if (this == NoOpLog()) {
+    return;
+  }
+  // Measure.
+  va_list args;
+  va_start(args, format);
+  intptr_t len = OS::VSNPrint(NULL, 0, format, args);
+  va_end(args);
+
+  // Print string to buffer.
+  char* buffer = reinterpret_cast<char*>(malloc(len + 1));
+  va_list args2;
+  va_start(args2, format);
+  OS::VSNPrint(buffer, (len + 1), format, args2);
+  va_end(args2);
+
+  // Does not append the '\0' character.
+  for (intptr_t i = 0; i < len; i++) {
+    buffer_.Add(buffer[i]);
+  }
+  free(buffer);
+  if ((manual_flush_ == 0) || FLAG_force_log_flush) {
+    Flush();
+  }
+}
+
+
+void Log::Flush(const intptr_t cursor) {
+  if (this == NoOpLog()) {
+    return;
+  }
+  if (buffer_.is_empty()) {
+    return;
+  }
+  if (buffer_.length() <= cursor) {
+    return;
+  }
+  TerminateString();
+  const char* str = &buffer_[cursor];
+  ASSERT(str != NULL);
+  printer_(str);
+  buffer_.TruncateTo(cursor);
+}
+
+
+void Log::Clear() {
+  if (this == NoOpLog()) {
+    return;
+  }
+  buffer_.TruncateTo(0);
+}
+
+
+intptr_t Log::cursor() const {
+  return buffer_.length();
+}
+
+
+Log Log::noop_log_;
+Log* Log::NoOpLog() {
+  return &noop_log_;
+}
+
+
+void Log::TerminateString() {
+  buffer_.Add('\0');
+}
+
+
+void Log::EnableManualFlush() {
+  manual_flush_++;
+}
+
+
+void Log::DisableManualFlush() {
+  manual_flush_--;
+  ASSERT(manual_flush_ >= 0);
+  if (manual_flush_ == 0) {
+    Flush();
+  }
+}
+
+
+LogBlock::LogBlock(Thread* thread, Log* log)
+    : StackResource(thread->isolate()),
+      log_(log), cursor_(log->cursor()) {
+  CommonConstructor();
+}
+
+
+LogBlock::LogBlock(Isolate* isolate)
+    : StackResource(isolate),
+      log_(isolate->Log()), cursor_(isolate->Log()->cursor()) {
+  CommonConstructor();
+}
+
+
+LogBlock::LogBlock(Thread* thread)
+    : StackResource(thread->isolate()),
+      log_(thread->isolate()->Log()),
+      cursor_(thread->isolate()->Log()->cursor()) {
+  CommonConstructor();
+}
+
+}  // namespace dart