Commit 7e4346f4 authored by Willy Tarreau's avatar Willy Tarreau Committed by Paul E. McKenney
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tools/nolibc/stdio: add a minimal [vf]printf() implementation 



This adds a minimal vfprintf() implementation as well as the commonly
used fprintf() and printf() that rely on it.

For now the function supports:
  - formats: %s, %c, %u, %d, %x
  - modifiers: %l and %ll
  - unknown chars are considered as modifiers and are ignored

It is designed to remain minimalist, despite this printf() is 549 bytes
on x86_64. It would be wise not to add too many formats.

Signed-off-by: default avatarWilly Tarreau <w@1wt.eu>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent e3e19052

tools/include/nolibc/stdio.h

+128 −0
Original line number Diff line number Diff line
@@ -7,6 +7,8 @@ 
#ifndef _NOLIBC_STDIO_H

#define _NOLIBC_STDIO_H



#include <stdarg.h>



#include "std.h"

#include "arch.h"

#include "types.h"
@@ -158,4 +160,130 @@ char *fgets(char *s, int size, FILE *stream) 
	return ofs ? s : NULL;

}





/* minimal vfprintf(). It supports the following formats:

 *  - %[l*]{d,u,c,x}

 *  - %s

 *  - unknown modifiers are ignored.

 */

static __attribute__((unused))

int vfprintf(FILE *stream, const char *fmt, va_list args)

{

	char escape, lpref, c;

	unsigned long long v;

	unsigned int written;

	size_t len, ofs;

	char tmpbuf[21];

	const char *outstr;



	written = ofs = escape = lpref = 0;

	while (1) {

		c = fmt[ofs++];



		if (escape) {

			/* we're in an escape sequence, ofs == 1 */

			escape = 0;

			if (c == 'c' || c == 'd' || c == 'u' || c == 'x') {

				if (lpref) {

					if (lpref > 1)

						v = va_arg(args, unsigned long long);

					else

						v = va_arg(args, unsigned long);

				} else

					v = va_arg(args, unsigned int);



				if (c == 'd') {

					/* sign-extend the value */

					if (lpref == 0)

						v = (long long)(int)v;

					else if (lpref == 1)

						v = (long long)(long)v;

				}



				switch (c) {

				case 'd':

					i64toa_r(v, tmpbuf);

					break;

				case 'u':

					u64toa_r(v, tmpbuf);

					break;

				case 'x':

					u64toh_r(v, tmpbuf);

					break;

				default: /* 'c' */

					tmpbuf[0] = v;

					tmpbuf[1] = 0;

					break;

				}

				outstr = tmpbuf;

			}

			else if (c == 's') {

				outstr = va_arg(args, char *);

			}

			else if (c == '%') {

				/* queue it verbatim */

				continue;

			}

			else {

				/* modifiers or final 0 */

				if (c == 'l') {

					/* long format prefix, maintain the escape */

					lpref++;

				}

				escape = 1;

				goto do_escape;

			}

			len = strlen(outstr);

			goto flush_str;

		}



		/* not an escape sequence */

		if (c == 0 || c == '%') {

			/* flush pending data on escape or end */

			escape = 1;

			lpref = 0;

			outstr = fmt;

			len = ofs - 1;

		flush_str:

			if (_fwrite(outstr, len, stream) != 0)

				break;



			written += len;

		do_escape:

			if (c == 0)

				break;

			fmt += ofs;

			ofs = 0;

			continue;

		}



		/* literal char, just queue it */

	}

	return written;

}



static __attribute__((unused))

int fprintf(FILE *stream, const char *fmt, ...)

{

	va_list args;

	int ret;



	va_start(args, fmt);

	ret = vfprintf(stream, fmt, args);

	va_end(args);

	return ret;

}



static __attribute__((unused))

int printf(const char *fmt, ...)

{

	va_list args;

	int ret;



	va_start(args, fmt);

	ret = vfprintf(stdout, fmt, args);

	va_end(args);

	return ret;

}



#endif /* _NOLIBC_STDIO_H */