purgatory/printf.c

#include <stdarg.h>
#include <limits.h>
#include <stdint.h>
#include <purgatory.h>
#include <string.h>

/*
 * Output
 * =============================================================================
 */

#define LONG_LONG_SHIFT  ((int)((sizeof(unsigned long long)*CHAR_BIT) - 4))
#define LONG_SHIFT  ((int)((sizeof(unsigned long)*CHAR_BIT) - 4))
#define INT_SHIFT   ((int)((sizeof(unsigned int)*CHAR_BIT) - 4))
#define SHRT_SHIFT  ((int)((sizeof(unsigned short)*CHAR_BIT) - 4))
#define CHAR_SHIFT  ((int)((sizeof(unsigned char)*CHAR_BIT) - 4))

/**************************************************************************
PRINTF and friends

	Formats:
		%x	- 4 bytes int (8 hex digits, lower case)
		%X	- 4 bytes int (8 hex digits, upper case)
		%lx     - 8 bytes long (16 hex digits, lower case)
		%lX     - 8 bytes long (16 hex digits, upper case)
		%hx	- 2 bytes int (4 hex digits, lower case)
		%hX	- 2 bytes int (4 hex digits, upper case)
		%hhx	- 1 byte int (2 hex digits, lower case)
		%hhX	- 1 byte int (2 hex digits, upper case)
			- optional # prefixes 0x or 0X
		%d	- decimal int
		%c	- char
		%s	- string
	Note: width specification not supported
**************************************************************************/
void vsprintf(char *buffer, const char *fmt, va_list args)
{
	char *p;
	for ( ; *fmt != '\0'; ++fmt) {
		if (*fmt != '%') {
			if (buffer)
				*buffer++ = *fmt;
			else
				putchar(*fmt);
			continue;
		}
		if (*++fmt == 's') {
			for(p = va_arg(args, char *); *p != '\0'; p++) 
				if (buffer)
					*buffer++ = *p;
				else
					putchar(*p);
		}
		else {	/* Length of item is bounded */
			char tmp[40], *q = tmp;
			int shift = INT_SHIFT;
			if (*fmt == 'L') {
				shift = LONG_LONG_SHIFT;
				fmt++;
			}
			else if (*fmt == 'l') {
				shift = LONG_SHIFT;
				fmt++;
			}
			else if (*fmt == 'h') {
				shift = SHRT_SHIFT;
				fmt++;
				if (*fmt == 'h') {
					shift = CHAR_SHIFT;
					fmt++;
				}
			}
			
			/*
			 * Before each format q points to tmp buffer
			 * After each format q points past end of item
			 */
			if ((*fmt | 0x20) == 'x') {
				/* With x86 gcc, sizeof(long) == sizeof(int) */
				unsigned long long h;
				int ncase;
				if (shift > LONG_SHIFT) {
					h = va_arg(args, unsigned long long);
				}
				else if (shift > INT_SHIFT) {
					h = va_arg(args, unsigned long);
				} else {
					h = va_arg(args, unsigned int);
				}
				ncase = (*fmt & 0x20);
				for ( ; shift >= 0; shift -= 4)
					*q++ = "0123456789ABCDEF"[(h >> shift) & 0xF] | ncase;
			}
			else if (*fmt == 'd') {
				char *r;
				long i;
				if (shift > LONG_SHIFT) {
					i = va_arg(args, long long);
				}
				else if (shift > INT_SHIFT) {
					i = va_arg(args, long);
				} else {
					i = va_arg(args, int);
				}
				if (i < 0) {
					*q++ = '-';
					i = -i;
				}
				p = q;		/* save beginning of digits */
				do {
					*q++ = '0' + (i % 10);
					i /= 10;
				} while (i);
				/* reverse digits, stop in middle */
				r = q;		/* don't alter q */
				while (--r > p) {
					i = *r;
					*r = *p;
					*p++ = i;
				}
			}
			else if (*fmt == 'c')
				*q++ = va_arg(args, int);
			else
				*q++ = *fmt;
			/* now output the saved string */
			for (p = tmp; p < q; ++p)
				if (buffer)
					*buffer++ = *p;
				else
					putchar(*p);
		}
	}
	if (buffer)
		*buffer = '\0';
}

void sprintf(char *buffer, const char *fmt, ...)
{
	va_list args;

	va_start(args, fmt);
	vsprintf(buffer, fmt, args);
	va_end(args);
}

void printf(const char *fmt, ...)
{
	va_list args;

	va_start(args, fmt);
	vsprintf(0, fmt, args);
	va_end(args);
}