Make string_util naming more consistent (#547)

* Rename StringXxx to StrXxx in string_util.h and its users

This makes the naming consistent within string_util and moves is the
Abseil convention.

* Style guide is 2 spaces before end of line "//" comments

* Rename StrPrintF/StringPrintF to StrFormat for absl compatibility.

include/benchmark/benchmark.h

@@ -543,7 +543,7 @@ class State {
   //  static void BM_Compress(benchmark::State& state) {
   //    ...
   //    double compress = input_size / output_size;
-  //    state.SetLabel(StringPrintf("compress:%.1f%%", 100.0*compression));
+  //    state.SetLabel(StrFormat("compress:%.1f%%", 100.0*compression));
   //  }
   // Produces output that looks like:
   //  BM_Compress   50         50   14115038  compress:27.3%

src/benchmark_register.cc

@@ -172,20 +172,20 @@ bool BenchmarkFamilies::FindBenchmarks(
             const auto& arg_name = family->arg_names_[arg_i];
             if (!arg_name.empty()) {
               instance.name +=
-                  StringPrintF("%s:", family->arg_names_[arg_i].c_str());
+                  StrFormat("%s:", family->arg_names_[arg_i].c_str());
             }
           }
           
-          instance.name += StringPrintF("%d", arg);
+          instance.name += StrFormat("%d", arg);
           ++arg_i;
         }
 
         if (!IsZero(family->min_time_))
-          instance.name += StringPrintF("/min_time:%0.3f", family->min_time_);
+          instance.name += StrFormat("/min_time:%0.3f", family->min_time_);
         if (family->iterations_ != 0)
-          instance.name += StringPrintF("/iterations:%d", family->iterations_);
+          instance.name += StrFormat("/iterations:%d", family->iterations_);
         if (family->repetitions_ != 0)
-          instance.name += StringPrintF("/repeats:%d", family->repetitions_);
+          instance.name += StrFormat("/repeats:%d", family->repetitions_);
 
         if (family->use_manual_time_) {
           instance.name += "/manual_time";
@@ -195,7 +195,7 @@ bool BenchmarkFamilies::FindBenchmarks(
 
         // Add the number of threads used to the name
         if (!family->thread_counts_.empty()) {
-          instance.name += StringPrintF("/threads:%d", instance.threads);
+          instance.name += StrFormat("/threads:%d", instance.threads);
         }
 
         if (re.Match(instance.name)) {

src/json_reporter.cc

@@ -32,15 +32,15 @@ namespace benchmark {
 namespace {
 
 std::string FormatKV(std::string const& key, std::string const& value) {
-  return StringPrintF("\"%s\": \"%s\"", key.c_str(), value.c_str());
+  return StrFormat("\"%s\": \"%s\"", key.c_str(), value.c_str());
 }
 
 std::string FormatKV(std::string const& key, const char* value) {
-  return StringPrintF("\"%s\": \"%s\"", key.c_str(), value);
+  return StrFormat("\"%s\": \"%s\"", key.c_str(), value);
 }
 
 std::string FormatKV(std::string const& key, bool value) {
-  return StringPrintF("\"%s\": %s", key.c_str(), value ? "true" : "false");
+  return StrFormat("\"%s\": %s", key.c_str(), value ? "true" : "false");
 }
 
 std::string FormatKV(std::string const& key, int64_t value) {

src/string_util.cc

@@ -122,7 +122,7 @@ std::string HumanReadableNumber(double n, double one_k) {
   return ToBinaryStringFullySpecified(n, 1.1, 1, one_k);
 }
 
-std::string StringPrintFImp(const char* msg, va_list args) {
+std::string StrFormatImp(const char* msg, va_list args) {
   // we might need a second shot at this, so pre-emptivly make a copy
   va_list args_cp;
   va_copy(args_cp, args);
@@ -152,10 +152,10 @@ std::string StringPrintFImp(const char* msg, va_list args) {
   return std::string(buff_ptr.get());
 }
 
-std::string StringPrintF(const char* format, ...) {
+std::string StrFormat(const char* format, ...) {
   va_list args;
   va_start(args, format);
-  std::string tmp = StringPrintFImp(format, args);
+  std::string tmp = StrFormatImp(format, args);
   va_end(args);
   return tmp;
 }

src/string_util.h

@@ -12,23 +12,23 @@ void AppendHumanReadable(int n, std::string* str);
 
 std::string HumanReadableNumber(double n, double one_k = 1024.0);
 
-std::string StringPrintF(const char* format, ...);
+std::string StrFormat(const char* format, ...);
 
-inline std::ostream& StringCatImp(std::ostream& out) BENCHMARK_NOEXCEPT {
+inline std::ostream& StrCatImp(std::ostream& out) BENCHMARK_NOEXCEPT {
   return out;
 }
 
 template <class First, class... Rest>
-inline std::ostream& StringCatImp(std::ostream& out, First&& f,
+inline std::ostream& StrCatImp(std::ostream& out, First&& f,
                                   Rest&&... rest) {
   out << std::forward<First>(f);
-  return StringCatImp(out, std::forward<Rest>(rest)...);
+  return StrCatImp(out, std::forward<Rest>(rest)...);
 }
 
 template <class... Args>
 inline std::string StrCat(Args&&... args) {
   std::ostringstream ss;
-  StringCatImp(ss, std::forward<Args>(args)...);
+  StrCatImp(ss, std::forward<Args>(args)...);
   return ss.str();
 }
 

src/sysinfo.cc

@@ -16,7 +16,7 @@
 
 #ifdef BENCHMARK_OS_WINDOWS
 #include <Shlwapi.h>
-#undef StrCat // Don't let StrCat in string_util.h be renamed to lstrcatA
+#undef StrCat  // Don't let StrCat in string_util.h be renamed to lstrcatA
 #include <VersionHelpers.h>
 #include <Windows.h>
 #else

src/timers.cc

@@ -17,7 +17,7 @@
 
 #ifdef BENCHMARK_OS_WINDOWS
 #include <Shlwapi.h>
-#undef StrCat // Don't let StrCat in string_util.h be renamed to lstrcatA
+#undef StrCat  // Don't let StrCat in string_util.h be renamed to lstrcatA
 #include <VersionHelpers.h>
 #include <Windows.h>
 #else