CFMT

fmt implemented in C.

See, you can print things like this in C/C++:

cfmt_println("{} {}", "This is", "cfmt");
cfmt_println("{} {} {}", 0.47, (short)10, (long long)100);

Or better formated:

cfmt_println("{:10} {:10}", "This is", "cfmt");
cfmt_println("{:10.1e} {:10x} {:10}", 0.47, (short)10, (long long)100);

Motivation

I'v been suffered from "%x", "%lx", "%llx" for a really long time. And I decided to end th is.

Say you have a struct A { int val; }, and originally, you use printf("%d", a.val);. And you changed int val to long long val, now you have to change all "%d" to "%lld". It's annoying.

I do hate std::cout. The performance, and the way format output.

float a = 123.777;
// If you want a formated output, you have to put more function in cout.
std::cout << setprecision(5) << a;

How to use this?(Usage)

Before use cfmt

Download cfmt, try to use your compiler to compile test.c:

gcc test.c cfmt.c -o test FLAGS_OF_YOUR_PROJECT
./test

Or MSVC:

cl test.c cfmt.c /std:c11 FLAGS_OF_YOUR_PROJECT
.\test.exe

If it is compiled successfully, and runs without any error, then it is OK to use cfmt.

Compile

Take cfmt.c and cfmt.h to your project, and include cfmt.h, compile cfmt.c. e.g.:

gcc cfmt.c -c
g++ cfmt.o test.cc -o test

gcc test.c -o test

If it is MSVC:

cl /std:c11 test.c cfmt.c

Or MSVC C++:

cl cfmt.c /c /std:c11
cl cfmt.o test.cc

How to format print a struct and class?

Well, you are able to do this in 2 ways.

convert it to a char *.

const char *convert_to_string(struct A *a) {
  // Here you `malloc`ed, and convert `a` to string, then return the string
}
int main() {
  struct A a;
  const char *str = convert_to_string(&a);
  cfmt_println("{}", str);
  free(str);
}

And in C++, you can print std::string like this:

cfmt_println("{}", str.c_str());

Modify cfmt

1. In C, see how I print struct tm * in this project.

2. In C++, struct/class is converted to its pointer, and you are going to set a formatter function, which converts all of these types to char * and fill into a buffer. I've showed how to print std::string and std::string_view

Wrap cfmt?

cfmt is macros. You can only use macro to wrap it.

#define Log(fmt, ...) cfmt_fprint(log_file, "Log {}:{}:" fmt "\n", __func__, __LINE__, ##__VA_ARGS__)

API references

void cfmt_fprint(FILE *fp, const char *fmt, ...)
void cfmt_println(const char *fmt, ...)
void cfmt_print(const char *fmt, ...)
const char *cfmt_format(const char *fmt, ...)

You DO NOT own the string returned by cfmt_format, DON'T free() the ptr!

const char *str = cfmt_format("{}", 12);
// This might crashes
free(str);

arg fmt: format string

If you are care about errors, call cfmt_last_errno() to get errno, and cfmt_strerr() to get the info string.

result = cfmt_format("{");
assert(cfmt_last_errno() == kUnmatchedBrace);
cfmt_println("{}", cfmt_strerr());

More Example

See test.c and test.cc