vsprintf.c

一个操作系统的源码部分

/*------------------------------------------------------------------------
 Module:        D:\BoCHS\Lingix\kernel\vsprintf.c
 Author:        Lars Wirzenius & Linus Torvalds ±(sunwen)
 Project:       Linux(Lingix)
 State:         2003.2.23
 Creation Date: Wuhan
 Description:   Wirzenius wrote this portably, Torvalds fucked
				it up :-)
------------------------------------------------------------------------*/
#include "String.h"
#include "Stdarg.h"

/* we use this so that we can do without the ctype library */
#define is_digit(c)	((c) >= '0' && (c) <= '9')

#define ZEROPAD	1		/* pad with zero */
#define SIGN	2		/* unsigned/signed long */
#define PLUS	4		/* show plus */
#define SPACE	8		/* space if plus */
#define LEFT	16		/* left justified */
#define SPECIAL	32		/* 0x */
#define SMALL	64		/* use 'abcdef' instead of 'ABCDEF' */

#define do_div(n,base) ({ \
int __res; \
__asm__("divl %4":"=a" (n),"=d" (__res):"0" (n),"1" (0),"r" (base)); \
__res; })

/*------------------------------------------------------------------------
 Procedure:     skip_atoi ID:1
 Purpose:
 Input:
 Output:
 Errors:
------------------------------------------------------------------------*/
static int skip_atoi(const char **s)
{
	int i = 0;

	while (is_digit(**s))
		i = i * 10 + *((*s)++) - '0';
	return i;
}

/*------------------------------------------------------------------------
 Procedure:     number ID:1
 Purpose:
 Input:
 Output:
 Errors:
------------------------------------------------------------------------*/
static char * number(char * str, int num, int base, int size, int precision, int type)
{
	int i;
	char c, sign, tmp[36];
	const char *digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

	if (type & SMALL)
		digits = "0123456789abcdefghijklmnopqrstuvwxyz";
	if (type & LEFT)
		type &= ~ZEROPAD;
	if (base < 2 || base > 36)
		return 0;
	c = (type & ZEROPAD) ? '0' : ' ';
	if (type & SIGN && num < 0) {
		sign = '-';
		num = -num;
	} else
		sign = (type & PLUS) ? '+' : ((type&SPACE) ? ' ' : 0);
	if (sign)
		size--;
	if (type & SPECIAL) {
		if (base == 16)
			size -= 2;
		else if (base == 8)
			size--;
	}
	i = 0;
	if (num == 0)
		tmp[i++]='0';
	else while (num != 0)
		tmp[i++] = digits[do_div(num, base)];
	if (i > precision)
		precision = i;
	size -= precision;
	if (!(type&(ZEROPAD + LEFT)))
		while (size-- > 0)
			*str++ = ' ';
	if (sign)
		*str++ = sign;
	if (type & SPECIAL) {
		if (base == 8)
			*str++ = '0';
		else if (base == 16) {
			*str++ = '0';
			*str++ = digits[33];
		}
	}
	if (!(type & LEFT))
		while (size-- > 0)
			*str++ = c;
	while (i < precision--)
		*str++ = '0';
	while (i-- > 0)
		*str++ = tmp[i];
	while (size-- > 0)
		*str++ = ' ';
	return str;
}

/*------------------------------------------------------------------------
 Procedure:     vsprintf ID:1
 Purpose:
 Input:
 Output:
 Errors:
------------------------------------------------------------------------*/
int vsprintf(char *buf, const char *fmt, va_list args)
{
	int len;
	int i;
	char * str;
	char *s;
	int *ip;
	int flags;		/* flags to number() */
	int field_width;	/* width of output field */
	int precision;		/* min. # of digits for integers; max number of chars for from string */
	int qualifier;		/* 'h', 'l', or 'L' for integer fields */

	for (str = buf ; *fmt; fmt++) {
		if (*fmt != '%') {
			*str++ = *fmt;
			continue;
		}

		/* process flags */
		flags = 0;
repeat:
		++fmt;		/* this also skips first '%' */
		switch (*fmt) {
		case '-':
			flags |= LEFT;
			goto repeat;
		case '+':
			flags |= PLUS;
			goto repeat;
		case ' ':
			flags |= SPACE;
			goto repeat;
		case '#':
			flags |= SPECIAL;
			goto repeat;
		case '0':
			flags |= ZEROPAD;
			goto repeat;
		}

		/* get field width */
		field_width = -1;
		if (is_digit(*fmt))
			field_width = skip_atoi(&fmt);
		else if (*fmt == '*') {
			/* it's the next argument */
			field_width = va_arg(args, int);
			if (field_width < 0) {
				field_width = -field_width;
				flags |= LEFT;
			}
		}

		/* get the precision */
		precision = -1;
		if (*fmt == '.') {
			++fmt;
			if (is_digit(*fmt))
				precision = skip_atoi(&fmt);
			else if (*fmt == '*') {
				/* it's the next argument */
				precision = va_arg(args, int);
			}
			if (precision < 0)
				precision = 0;
		}

		/* get the conversion qualifier */
		qualifier = -1;
		if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L') {
			qualifier = *fmt;
			++fmt;
		}

		switch (*fmt) {
		case 'c':
			if (!(flags & LEFT))
				while (--field_width > 0)
					*str++ = ' ';
			*str++ = (unsigned char) va_arg(args, int);
			while (--field_width > 0)
				*str++ = ' ';
			break;

		case 's':
			s = va_arg(args, char *);
			len = strlen(s);
			if (precision < 0)
				precision = len;
			else if (len > precision)
				len = precision;

			if (!(flags & LEFT))
				while (len < field_width--)
					*str++ = ' ';
			for (i = 0; i < len; ++i)
				*str++ = *s++;
			while (len < field_width--)
				*str++ = ' ';
			break;

		case 'o':
			str = number(str, va_arg(args, unsigned long), 8, field_width, precision, flags);
			break;

		case 'p':
			if (field_width == -1) {
				field_width = 8;
				flags |= ZEROPAD;
			}
			str = number(str, (unsigned long) va_arg(args, void *), 16, field_width, precision, flags);
			break;

		case 'x':
			flags |= SMALL;
		case 'X':
			str = number(str, va_arg(args, unsigned long), 16, field_width, precision, flags);
			break;

		case 'd':
		case 'i':
			flags |= SIGN;
		case 'u':
			str = number(str, va_arg(args, unsigned long), 10, field_width, precision, flags);
			break;

		case 'n':
			ip = va_arg(args, int *);
			*ip = (str - buf);
			break;

		default:
			if (*fmt != '%')
				*str++ = '%';
			if (*fmt)
				*str++ = *fmt;
			else
				--fmt;
			break;
		}
	}
	*str = '\0';
	return str-buf;
}


void sprintf(char* buf,const char * fmt, ...)
{
	int i;
	va_list args;
	va_start(args, fmt);
	i = vsprintf(buf, fmt, args);
	va_end(args);
}