first commit

src/StringHelper.cpp

@@ -0,0 +1,67 @@
+#include "StringHelper.hpp"
+
+namespace YYCC::StringHelper {
+
+	bool Printf(std::string& strl, const char* format, ...) {
+		va_list argptr;
+		va_start(argptr, format);
+		bool ret = VPrintf(strl, format, argptr);
+		va_end(argptr);
+		return ret;
+	}
+
+	bool VPrintf(std::string& strl, const char* format, va_list argptr) {
+		va_list args1;
+		va_copy(args1, argptr);
+		va_list args2;
+		va_copy(args2, argptr);
+
+		// the return value is desired char count without NULL terminal.
+		// minus number means error
+		int count = std::vsnprintf(nullptr, 0, format, args1);
+		if (count < 0) {
+			// invalid length returned by vsnprintf.
+			return false;
+		}
+		va_end(args1);
+
+		// resize std::string to desired count.
+		// and pass its length + 1 to std::vsnprintf,
+		// because std::vsnprintf only can write "buf_size - 1" chars with a trailing NULL.
+		// however std::vsnprintf already have a trailing NULL, so we plus 1 for it.
+		strl.resize(count);
+		int write_result = std::vsnprintf(strl.data(), strl.size() + 1, format, args2);
+		va_end(args2);
+		
+		if (write_result < 0 || write_result > count) {
+			// invalid write result in vsnprintf.
+			return false;
+		}
+
+		return true;
+	}
+
+	
+	std::string Printf(const char* format, ...) {
+		std::string ret;
+		
+		va_list argptr;
+		va_start(argptr, format);
+		VPrintf(ret, format, argptr);
+		va_end(argptr);
+
+		return ret;
+	}
+
+	std::string VPrintf(const char* format, va_list argptr) {
+		std::string ret;
+
+		va_list argcpy;
+		va_copy(argcpy, argptr);
+		VPrintf(ret, format, argcpy);
+		va_end(argcpy);
+
+		return ret;
+	}
+
+}