[Tracing] V8 Tracing Controller - Add args and copy support

src/libplatform/tracing/trace-writer.cc

Index: src/libplatform/tracing/trace-writer.cc
diff --git a/src/libplatform/tracing/trace-writer.cc b/src/libplatform/tracing/trace-writer.cc
index 464b5713fc2b69b6076f43b7cd40ef0ad7e8dd50..b04526f39abfa365ff3f736058aacd3219ee16b6 100644
--- a/src/libplatform/tracing/trace-writer.cc
+++ b/src/libplatform/tracing/trace-writer.cc
@@ -4,12 +4,85 @@
 
 #include "src/libplatform/tracing/trace-writer.h"
 
+#include <cmath>
+
+#include "base/trace_event/common/trace_event_common.h"
 #include "src/base/platform/platform.h"
 
 namespace v8 {
 namespace platform {
 namespace tracing {
 
+// Currently we do not support JSON-escaping strings in trace arguments.
+// Thus we perform an IsJSONString() check before writing any string argument.
+// In particular, this means strings cannot have control characters or " or \.
+V8_INLINE static bool IsJSONString(const char* str) {
+  size_t len = strlen(str);
+  for (size_t i = 0; i < len; ++i) {
+    if (iscntrl(str[i]) || str[i] == '\"' || str[i] == '\\') {
+      return false;
+    }
+  }
+  return true;
+}
+
+void JSONTraceWriter::AppendArgValue(uint8_t type,
+                                     TraceObject::ArgValue value) {
+  switch (type) {
+    case TRACE_VALUE_TYPE_BOOL:
+      stream_ << (value.as_bool ? "true" : "false");
+      break;
+    case TRACE_VALUE_TYPE_UINT:
+      stream_ << value.as_uint;
+      break;
+    case TRACE_VALUE_TYPE_INT:
+      stream_ << value.as_int;
+      break;
+    case TRACE_VALUE_TYPE_DOUBLE: {
+      std::string real;
+      double val = value.as_double;
+      if (std::isfinite(val)) {
+        std::ostringstream convert_stream;
+        convert_stream << val;
+        real = convert_stream.str();
+        // Ensure that the number has a .0 if there's no decimal or 'e'.  This
+        // makes sure that when we read the JSON back, it's interpreted as a
+        // real rather than an int.
+        if (real.find('.') == std::string::npos &&
+            real.find('e') == std::string::npos &&
+            real.find('E') == std::string::npos) {
+          real += ".0";
+        }
+      } else if (std::isnan(val)) {
+        // The JSON spec doesn't allow NaN and Infinity (since these are
+        // objects in EcmaScript).  Use strings instead.
+        real = "\"NaN\"";
+      } else if (val < 0) {
+        real = "\"-Infinity\"";
+      } else {
+        real = "\"Infinity\"";
+      }
+      stream_ << real;
+      break;
+    }
+    case TRACE_VALUE_TYPE_POINTER:
+      // JSON only supports double and int numbers.
+      // So as not to lose bits from a 64-bit pointer, output as a hex string.
+      stream_ << "\"" << value.as_pointer << "\"";
+      break;
+    case TRACE_VALUE_TYPE_STRING:
+    case TRACE_VALUE_TYPE_COPY_STRING:
+      // Strings are currently not JSON-escaped, so we need to perform a check
+      // to see if they are valid JSON strings.
+      CHECK(value.as_string == nullptr || IsJSONString(value.as_string));
+      stream_ << "\"" << (value.as_string ? value.as_string : "NULL") << "\"";
+      break;
+    default:
+      UNREACHABLE();
+      break;
+  }
+}
+
 JSONTraceWriter::JSONTraceWriter(std::ostream& stream) : stream_(stream) {
   stream_ << "{\"traceEvents\":[";
 }
@@ -19,30 +92,33 @@ JSONTraceWriter::~JSONTraceWriter() { stream_ << "]}"; }
 void JSONTraceWriter::AppendTraceEvent(TraceObject* trace_event) {
   if (append_comma_) stream_ << ",";
   append_comma_ = true;
-  if (trace_event->scope() == NULL) {
-    stream_ << "{\"pid\":" << trace_event->pid()
-            << ",\"tid\":" << trace_event->tid()
-            << ",\"ts\":" << trace_event->ts()
-            << ",\"tts\":" << trace_event->tts() << ",\"ph\":\""
-            << trace_event->phase() << "\",\"cat\":\""
-            << TracingController::GetCategoryGroupName(
-                   trace_event->category_enabled_flag())
-            << "\",\"name\":\"" << trace_event->name()
-            << "\",\"args\":{},\"dur\":" << trace_event->duration()
-            << ",\"tdur\":" << trace_event->cpu_duration() << "}";
-  } else {
-    stream_ << "{\"pid\":" << trace_event->pid()
-            << ",\"tid\":" << trace_event->tid()
-            << ",\"ts\":" << trace_event->ts()
-            << ",\"tts\":" << trace_event->tts() << ",\"ph\":\""
-            << trace_event->phase() << "\",\"cat\":\""
-            << TracingController::GetCategoryGroupName(
-                   trace_event->category_enabled_flag())
-            << "\",\"name\":\"" << trace_event->name() << "\",\"scope\":\""
-            << trace_event->scope()
-            << "\",\"args\":{},\"dur\":" << trace_event->duration()
-            << ",\"tdur\":" << trace_event->cpu_duration() << "}";
+  stream_ << "{\"pid\":" << trace_event->pid()
+          << ",\"tid\":" << trace_event->tid()
+          << ",\"ts\":" << trace_event->ts()
+          << ",\"tts\":" << trace_event->tts() << ",\"ph\":\""
+          << trace_event->phase() << "\",\"cat\":\""
+          << TracingController::GetCategoryGroupName(
+                 trace_event->category_enabled_flag())
+          << "\",\"name\":\"" << trace_event->name()
+          << "\",\"dur\":" << trace_event->duration()
+          << ",\"tdur\":" << trace_event->cpu_duration();
+  if (trace_event->flags() & TRACE_EVENT_FLAG_HAS_ID) {
+    if (trace_event->scope() != nullptr) {
+      stream_ << ",\"scope\":\"" << trace_event->scope() << "\"";
+    }
+    // So as not to lose bits from a 64-bit integer, output as a hex string.
+    stream_ << ",\"id\":\"0x" << std::hex << trace_event->id() << "\"";
+  }
+  stream_ << ",\"args\":{";
+  const char** arg_names = trace_event->arg_names();
+  const uint8_t* arg_types = trace_event->arg_types();
+  TraceObject::ArgValue* arg_values = trace_event->arg_values();
+  for (int i = 0; i < trace_event->num_args(); ++i) {
+    if (i > 0) stream_ << ",";
+    stream_ << "\"" << arg_names[i] << "\":";
+    AppendArgValue(arg_types[i], arg_values[i]);
   }
+  stream_ << "}}";
   // TODO(fmeawad): Add support for Flow Events.
 }