Allow log print of data units.

Bug: webrtc:9709
Change-Id: I5987a9779e645115dc1893944302a73d540bcf2f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/125680
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27578}

api/units/BUILD.gn

@@ -85,6 +85,7 @@ if (rtc_include_tests) {
       ":data_size",
       ":time_delta",
       ":timestamp",
+      "../../rtc_base:logging",
       "../../test:test_support",
     ]
   }

api/units/data_rate.h

@@ -107,6 +107,9 @@ inline DataSize operator*(const TimeDelta duration, const DataRate rate) {
 }
 
 std::string ToString(DataRate value);
+inline std::string ToLogString(DataRate value) {
+  return ToString(value);
+}
 
 #ifdef UNIT_TEST
 inline std::ostream& operator<<(  // no-presubmit-check TODO(webrtc:8982)

api/units/data_rate_unittest.cc

@@ -9,11 +9,19 @@
  */
 
 #include "api/units/data_rate.h"
+#include "rtc_base/logging.h"
 #include "test/gtest.h"
 
 namespace webrtc {
 namespace test {
 
+TEST(DataRateTest, CompilesWithChecksAndLogs) {
+  DataRate a = DataRate::kbps(300);
+  DataRate b = DataRate::kbps(210);
+  RTC_CHECK_GT(a, b);
+  RTC_LOG(LS_INFO) << a;
+}
+
 TEST(DataRateTest, ConstExpr) {
   constexpr int64_t kValue = 12345;
   constexpr DataRate kDataRateZero = DataRate::Zero();

api/units/data_size.h

@@ -52,6 +52,9 @@ class DataSize final : public rtc_units_impl::RelativeUnit<DataSize> {
 };
 
 std::string ToString(DataSize value);
+inline std::string ToLogString(DataSize value) {
+  return ToString(value);
+}
 
 #ifdef UNIT_TEST
 inline std::ostream& operator<<(  // no-presubmit-check TODO(webrtc:8982)

api/units/time_delta.h

@@ -95,6 +95,9 @@ class TimeDelta final : public rtc_units_impl::RelativeUnit<TimeDelta> {
 };
 
 std::string ToString(TimeDelta value);
+inline std::string ToLogString(TimeDelta value) {
+  return ToString(value);
+}
 
 #ifdef UNIT_TEST
 inline std::ostream& operator<<(  // no-presubmit-check TODO(webrtc:8982)

api/units/timestamp.h

@@ -133,6 +133,9 @@ class Timestamp final : public rtc_units_impl::UnitBase<Timestamp> {
 };
 
 std::string ToString(Timestamp value);
+inline std::string ToLogString(Timestamp value) {
+  return ToString(value);
+}
 
 #ifdef UNIT_TEST
 inline std::ostream& operator<<(  // no-presubmit-check TODO(webrtc:8982)

rtc_base/checks.h

@@ -125,6 +125,15 @@ struct Val {
   T val;
 };
 
+// Case for when we need to construct a temp string and then print that.
+// (We can't use Val<CheckArgType::kStdString, const std::string*>
+// because we need somewhere to store the temp string.)
+struct ToStringVal {
+  static constexpr CheckArgType Type() { return CheckArgType::kStdString; }
+  const std::string* GetVal() const { return &val; }
+  std::string val;
+};
+
 inline Val<CheckArgType::kInt, int> MakeVal(int x) {
   return {x};
 }
@@ -178,6 +187,15 @@ MakeVal(T x) {
   return {static_cast<typename std::underlying_type<T>::type>(x)};
 }
 
+template <typename T,
+          typename T1 = typename std::decay<T>::type,
+          typename T2 = decltype(ToLogString(std::declval<T>())),
+          typename std::enable_if<std::is_same<T2, std::string>::value>::type* =
+              nullptr>
+ToStringVal MakeVal(const T& x) {
+  return {ToLogString(x)};
+}
+
 // Ephemeral type that represents the result of the logging << operator.
 template <typename... Ts>
 class LogStreamer;

rtc_base/logging.h

@@ -186,11 +186,10 @@ struct Val {
   T val;
 };
 
-// TODO(bugs.webrtc.org/9278): Get rid of this specialization when callers
-// don't need it anymore. No in-tree caller does, but some external callers
-// still do.
-template <>
-struct Val<LogArgType::kStdString, std::string> {
+// Case for when we need to construct a temp string and then print that.
+// (We can't use Val<CheckArgType::kStdString, const std::string*>
+// because we need somewhere to store the temp string.)
+struct ToStringVal {
   static constexpr LogArgType Type() { return LogArgType::kStdString; }
   const std::string* GetVal() const { return &val; }
   std::string val;
@@ -265,26 +264,45 @@ inline Val<LogArgType::kLogMetadataTag, LogMetadataTag> MakeVal(
 }
 #endif
 
+template <typename T, typename = void>
+struct has_to_log_string : std::false_type {};
+template <typename T>
+struct has_to_log_string<
+    T,
+    typename std::enable_if<
+        std::is_same<std::string,
+                     decltype(ToLogString(std::declval<T>()))>::value>::type>
+    : std::true_type {};
+
 // Handle arbitrary types other than the above by falling back to stringstream.
 // TODO(bugs.webrtc.org/9278): Get rid of this overload when callers don't need
 // it anymore. No in-tree caller does, but some external callers still do.
 template <
     typename T,
-    typename T1 =
-        typename std::remove_cv<typename std::remove_reference<T>::type>::type,
+    typename T1 = typename std::decay<T>::type,
     typename std::enable_if<
         std::is_class<T1>::value && !std::is_same<T1, std::string>::value &&
         !std::is_same<T1, LogMetadata>::value &&
+        !has_to_log_string<T1>::value &&
 #ifdef WEBRTC_ANDROID
         !std::is_same<T1, LogMetadataTag>::value &&
 #endif
         !std::is_same<T1, LogMetadataErr>::value>::type* = nullptr>
-Val<LogArgType::kStdString, std::string> MakeVal(const T& x) {
+ToStringVal MakeVal(const T& x) {
   std::ostringstream os;  // no-presubmit-check TODO(webrtc:8982)
   os << x;
   return {os.str()};
 }
 
+template <
+    typename T,
+    typename T1 = typename std::decay<T>::type,
+    typename std::enable_if<std::is_class<T1>::value &&
+                            has_to_log_string<T1>::value>::type* = nullptr>
+ToStringVal MakeVal(const T& x) {
+  return {ToLogString(x)};
+}
+
 void Log(const LogArgType* fmt, ...);
 
 // Ephemeral type that represents the result of the logging << operator.