printxf.c

#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "printxf.h"

struct printxf printxf_default;

/* allow domains an easy way to defer standard specifiers to the
 * system's implementation. */
int printxf_vfprintf(struct printxf *pxf,
		     FILE *fp, const char *spec, va_list ap)
{
	return vfprintf(fp, spec, ap);
}

int __printxf_wsegment(FILE *fp, const char **fmt, size_t ssize, size_t *tsize)
{
	size_t wsize;

	wsize = fwrite(*fmt, 1, ssize, fp);
	*tsize += wsize;
	*fmt   += wsize;

	return (wsize < ssize) ? EOF : 0;
}

int vfprintxf(struct printxf *pxf, FILE *fp, const char *fmt, va_list ap)
{
	size_t tsize = 0, wsize, ssize;
	vfprintxf_fn handler;
	char spec[16];

	pxf = pxf ? : &printxf_default;

	if (!fmt)
		return 0;

	while (*fmt) {
		ssize = strcspn(fmt, "%");

		/* leading segment containing no format specifiers. */
		if (ssize && __printxf_wsegment(fp, &fmt, ssize, &tsize))
			break;

		if (fmt[0] == '\0') {
			/* this was the last segment */
			break;
		} else if ((fmt[0] == '%')
			   && ((fmt[1] == '\0') || (fmt[1] == '%'))) {
			/* "%" or "%%", write "%" */
			if (!fwrite("%", 1, 1, fp))
				break;

			tsize++;
			fmt += fmt[1] ? 2 : 1;
			continue;
		}
		
		ssize = strspn(fmt + 1, " #$'*+,-.0123456789:;L_hjlqtvz") + 1;

		if (!fmt[ssize]) {
			/* corner case. fmt ends with an unterminated
			 * format. e.g. "evilness: 100%" */
			__printxf_wsegment(fp, &fmt, ssize, &tsize);
			break;
		}

		handler = pxf->vfprintxf[fmt[ssize] & 0x7f];
		if (!handler) {
			/* unsupported specifier, write the entire
			 * specifier unformatted to the output */
			if (__printxf_wsegment(fp, &fmt, ssize + 1, &tsize))
				break;

			continue;
		}

		ssize++;
		memset(spec, '\0', sizeof(spec));
		strncpy(spec, fmt, (ssize >= sizeof(spec)) ? sizeof(spec) - 1 : ssize);
		fmt += ssize;

		tsize += handler(pxf, fp, spec, ap);
	}

	return tsize;
}

int fprintxf(struct printxf *pxf, FILE *fp, const char *fmt, ...)
{
	va_list ap;
	int ret;

	va_start(ap, fmt);
	ret = vfprintxf(pxf, fp, fmt, ap);
	va_end(ap);
	return ret;
}

int vprintxf(struct printxf *pxf, const char *fmt, va_list ap)
{
	return vfprintxf(pxf, stdout, fmt, ap);
}

int printxf(struct printxf *pxf, const char *fmt, ...)
{
	va_list ap;
	int ret;

	va_start(ap, fmt);
	ret = vprintxf(pxf, fmt, ap);
	va_end(ap);
	return ret;
}

__attribute__((constructor))
static void printxf_init(void)
{
	const char *std = "aAcdeEfFgGiosuxX";

	for (; *std; std++)
		printxf_default.vfprintxf[(int)*std] = &printxf_vfprintf;
}