[tracing] Add support for TracedValue JSON serializer.

src/tracing/traced-value.cc

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/tracing/traced-value.h"
+
+#include "src/base/platform/platform.h"
+
+namespace v8 {
+namespace tracing {
+
+namespace {
+
+#define DCHECK_CURRENT_CONTAINER_IS(x) DCHECK_EQ(x, nesting_stack_.back())
+#define DCHECK_CONTAINER_STACK_DEPTH_EQ(x) DCHECK_EQ(x, nesting_stack_.size())
+#ifdef DEBUG
+const bool kStackTypeDict = false;
+const bool kStackTypeArray = true;
+#define DEBUG_PUSH_CONTAINER(x) nesting_stack_.push_back(x)
+#define DEBUG_POP_CONTAINER() nesting_stack_.pop_back()
+#else
+#define DEBUG_PUSH_CONTAINER(x) ((void)0)
+#define DEBUG_POP_CONTAINER() ((void)0)
+#endif
+
+std::string EscapeString(const std::string& value) {
+  std::string result("\"");

[Primiano Tucci (use gerrit), 2016/10/05 19:50:48]

maybe you can reserve(length+2) to optimistically reduce the heap traffic for
cases that require no escaping.

[alph, 2016/10/06 00:03:10]

Done.

+  size_t length = value.length();
+  char number_buffer[10];
+  for (size_t src = 0; src < length; ++src) {
+    unsigned char c = value[src];

[Primiano Tucci (use gerrit), 2016/10/05 19:50:48]

why unsigned, operator[] is signed IIRC.

[alph, 2016/10/06 00:03:10]

Done.

+    switch (c) {
+      case '\t':
+        result += "\\t";
+        break;
+      case '\n':
+        result += "\\n";
+        break;
+      case '\"':
+        result += "\\\"";
+        break;
+      case '\\':
+        result += "\\\\";
+        break;
+      default:
+        if (c < '\040') {
+          base::OS::SNPrintF(number_buffer, arraysize(number_buffer), "\\u%04X",
+                             static_cast<unsigned>(c));
+          result += number_buffer;
+        } else {
+          result += c;
+        }
+    }
+  }
+  result += '"';
+  return result;
+}
+
+}  // namespace
+
+std::unique_ptr<TracedValue> TracedValue::Create() {
+  return std::unique_ptr<TracedValue>(new TracedValue());
+}
+
+TracedValue::TracedValue() : first_item_(true) {
+  DEBUG_PUSH_CONTAINER(kStackTypeDict);
+}
+
+TracedValue::~TracedValue() {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeDict);
+  DEBUG_POP_CONTAINER();
+  DCHECK_CONTAINER_STACK_DEPTH_EQ(0u);
+}
+
+void TracedValue::SetInteger(const char* name, int value) {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeDict);
+  WriteName(name);
+  data_ += std::to_string(value);
+}
+
+void TracedValue::SetDouble(const char* name, double value) {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeDict);
+  WriteName(name);
+  data_ += std::to_string(value);
+}
+
+void TracedValue::SetBoolean(const char* name, bool value) {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeDict);
+  WriteName(name);
+  data_ += value ? "true" : "false";
+}
+
+void TracedValue::SetString(const char* name, const std::string& value) {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeDict);
+  WriteName(name);
+  data_ += EscapeString(value);
+}
+
+void TracedValue::BeginDictionary(const char* name) {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeDict);
+  DEBUG_PUSH_CONTAINER(kStackTypeDict);
+  WriteName(name);
+  data_ += '{';
+  first_item_ = true;
+}
+
+void TracedValue::BeginArray(const char* name) {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeDict);
+  DEBUG_PUSH_CONTAINER(kStackTypeArray);
+  WriteName(name);
+  data_ += '[';
+  first_item_ = true;
+}
+
+void TracedValue::AppendInteger(int value) {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeArray);
+  WriteComma();
+  data_ += std::to_string(value);
+}
+
+void TracedValue::AppendDouble(double value) {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeArray);
+  WriteComma();
+  data_ += std::to_string(value);
+}
+
+void TracedValue::AppendBoolean(bool value) {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeArray);
+  WriteComma();
+  data_ += value ? "true" : "false";
+}
+
+void TracedValue::AppendString(const std::string& value) {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeArray);
+  WriteComma();
+  data_ += EscapeString(value);
+}
+
+void TracedValue::BeginDictionary() {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeArray);
+  DEBUG_PUSH_CONTAINER(kStackTypeDict);
+  WriteComma();
+  data_ += '{';
+  first_item_ = true;
+}
+
+void TracedValue::BeginArray() {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeArray);
+  DEBUG_PUSH_CONTAINER(kStackTypeArray);
+  WriteComma();
+  data_ += '[';
+  first_item_ = true;
+}
+
+void TracedValue::EndDictionary() {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeDict);
+  DEBUG_POP_CONTAINER();
+  data_ += '}';
+  first_item_ = false;
+}
+
+void TracedValue::EndArray() {
+  DCHECK_CURRENT_CONTAINER_IS(kStackTypeArray);
+  DEBUG_POP_CONTAINER();
+  data_ += ']';
+  first_item_ = false;
+}
+
+void TracedValue::WriteComma() {
+  if (first_item_) {
+    first_item_ = false;
+  } else {
+    data_ += ',';
+  }
+}
+
+void TracedValue::WriteName(const char* name) {
+  WriteComma();
+  data_ += '"';
+  data_ += name;
+  data_ += "\":";
+}
+
+void TracedValue::AppendAsTraceFormat(std::string* out) const {
+  *out += '{';
+  *out += data_;
+  *out += '}';
+}
+
+}  // namespace tracing
+}  // namespace v8