Adding Google benchmarking library.

third_party/google_benchmark/src/commandlineflags.h

Index: third_party/google_benchmark/src/commandlineflags.h
diff --git a/third_party/google_benchmark/src/commandlineflags.h b/third_party/google_benchmark/src/commandlineflags.h
new file mode 100644
index 0000000000000000000000000000000000000000..945c9a9fc4af3be7a4ab07db31448b33bf380122
--- /dev/null
+++ b/third_party/google_benchmark/src/commandlineflags.h
@@ -0,0 +1,79 @@
+#ifndef BENCHMARK_COMMANDLINEFLAGS_H_
+#define BENCHMARK_COMMANDLINEFLAGS_H_
+
+#include <cstdint>
+#include <string>
+
+// Macro for referencing flags.
+#define FLAG(name) FLAGS_##name
+
+// Macros for declaring flags.
+#define DECLARE_bool(name) extern bool FLAG(name)
+#define DECLARE_int32(name) extern int32_t FLAG(name)
+#define DECLARE_int64(name) extern int64_t FLAG(name)
+#define DECLARE_double(name) extern double FLAG(name)
+#define DECLARE_string(name) extern std::string FLAG(name)
+
+// Macros for defining flags.
+#define DEFINE_bool(name, default_val, doc) bool FLAG(name) = (default_val)
+#define DEFINE_int32(name, default_val, doc) int32_t FLAG(name) = (default_val)
+#define DEFINE_int64(name, default_val, doc) int64_t FLAG(name) = (default_val)
+#define DEFINE_double(name, default_val, doc) double FLAG(name) = (default_val)
+#define DEFINE_string(name, default_val, doc) \
+  std::string FLAG(name) = (default_val)
+
+namespace benchmark {
+// Parses 'str' for a 32-bit signed integer.  If successful, writes the result
+// to *value and returns true; otherwise leaves *value unchanged and returns
+// false.
+bool ParseInt32(const std::string& src_text, const char* str, int32_t* value);
+
+// Parses a bool/Int32/string from the environment variable
+// corresponding to the given Google Test flag.
+bool BoolFromEnv(const char* flag, bool default_val);
+int32_t Int32FromEnv(const char* flag, int32_t default_val);
+double DoubleFromEnv(const char* flag, double default_val);
+const char* StringFromEnv(const char* flag, const char* default_val);
+
+// Parses a string for a bool flag, in the form of either
+// "--flag=value" or "--flag".
+//
+// In the former case, the value is taken as true if it passes IsTruthyValue().
+//
+// In the latter case, the value is taken as true.
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+bool ParseBoolFlag(const char* str, const char* flag, bool* value);
+
+// Parses a string for an Int32 flag, in the form of
+// "--flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+bool ParseInt32Flag(const char* str, const char* flag, int32_t* value);
+
+// Parses a string for a Double flag, in the form of
+// "--flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+bool ParseDoubleFlag(const char* str, const char* flag, double* value);
+
+// Parses a string for a string flag, in the form of
+// "--flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+bool ParseStringFlag(const char* str, const char* flag, std::string* value);
+
+// Returns true if the string matches the flag.
+bool IsFlag(const char* str, const char* flag);
+
+// Returns true unless value starts with one of: '0', 'f', 'F', 'n' or 'N', or
+// some non-alphanumeric character. As a special case, also returns true if
+// value is the empty string.
+bool IsTruthyFlagValue(const std::string& value);
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_COMMANDLINEFLAGS_H_