Add TraceMeEncode helper

PiperOrigin-RevId: 311818799
Change-Id: I437235c1603a1e5be99a410376801771cfda0c66

tensorflow/core/profiler/lib/BUILD

@@ -102,6 +102,16 @@ cc_library(
     ]),
 )
 
+cc_library(
+    name = "traceme_encode",
+    hdrs = ["traceme_encode.h"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "//tensorflow/core:lib",
+        "@com_google_absl//absl/strings",
+    ],
+)
+
 cc_library(
     name = "annotated_traceme",
     hdrs = ["annotated_traceme.h"],

tensorflow/core/profiler/lib/traceme_encode.h

@@ -0,0 +1,82 @@
+/* Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_CORE_PROFILER_LIB_TRACEME_ENCODE_H_
+#define TENSORFLOW_CORE_PROFILER_LIB_TRACEME_ENCODE_H_
+
+#include <string.h>
+
+#include <initializer_list>
+#include <string>
+#include <utility>
+
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+#include "tensorflow/core/platform/logging.h"
+#include "tensorflow/core/platform/macros.h"
+
+namespace tensorflow {
+namespace profiler {
+namespace internal {
+
+// Copies the contents of str to the address pointed by out.
+// Returns the address after the copy.
+// REQUIRED: The address range [out, out + str.size()] must have been allocated.
+TF_ATTRIBUTE_ALWAYS_INLINE inline char* Append(char* out,
+                                               absl::string_view str) {
+  const size_t str_size = str.size();
+  if (str_size > 0) {
+    memcpy(out, str.data(), str_size);
+    out += str_size;
+  }
+  return out;
+}
+
+}  // namespace internal
+
+// Encodes an event name and arguments into a string stored by TraceMe.
+// Use within a lambda to avoid expensive operations when tracing is inactive.
+// Example Usage:
+//   TraceMe trace_me([&name, value1]() {
+//     return TraceMeEncode(name, {{"key1", value1}, {"key2", 42}});
+//   });
+inline std::string TraceMeEncode(
+    std::string name,
+    std::initializer_list<std::pair<absl::string_view, absl::AlphaNum>> args) {
+  if (TF_PREDICT_TRUE(args.size() > 0)) {
+    const auto old_size = name.size();
+    auto new_size = old_size + args.size() * 2 + 1;
+    for (const auto& arg : args) {
+      new_size += arg.first.size() + arg.second.size();
+    }
+    name.resize(new_size);
+    char* const begin = &name[0];
+    char* out = begin + old_size;
+    *out++ = '#';
+    for (const auto& arg : args) {
+      out = internal::Append(out, arg.first);
+      *out++ = '=';
+      out = internal::Append(out, arg.second.Piece());
+      *out++ = ',';
+    }
+    *(out - 1) = '#';
+    DCHECK_EQ(out, begin + new_size);
+  }
+  return name;
+}
+
+}  // namespace profiler
+}  // namespace tensorflow
+
+#endif  // TENSORFLOW_CORE_PROFILER_LIB_TRACEME_ENCODE_H_