printk.c

printk 从linux核心裁剪出来,可单独编译运行, 对于移植到不支持C运行库的平台增加打印功能有借鉴意义

/*
 *  linux/lib/vsprintf.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/* vsprintf.c -- Lars Wirzenius & Linus Torvalds. */
/*
 * Wirzenius wrote this portably, Torvalds fucked it up :-)
 */

/* 
 * Fri Jul 13 2001 Crutcher Dunnavant <[e-mail]>
 * - changed to provide snprintf and vsnprintf functions
 */

#include <stdarg.h>
#include <stdio.h>


#define PAGE_SHIFT      13
#define PAGE_SIZE       (1UL << PAGE_SHIFT)

#define INT_MAX          (5)  


size_t strnlen(const char * s, size_t count)
 {
        const char *sc;

        for (sc = s; count-- && *sc != '\0'; ++sc)
               /* nothing */;
       return sc - s;
}




/**
 * simple_strtoul - convert a string to an unsigned long
 * @cp: The start of the string
 * @endp: A pointer to the end of the parsed string will be placed here
 * @base: The number base to use
 */
unsigned long simple_strtoul(const char *cp,char **endp,unsigned int base)
{
	unsigned long result = 0,value;

	if (!base) {
		base = 10;
		if (*cp == '0') {
			base = 8;
			cp++;
			if ((*cp == 'x') && isxdigit(cp[1])) {
				cp++;
				base = 16;
			}
		}
	}
	while (isxdigit(*cp) &&
	       (value = isdigit(*cp) ? *cp-'0' : toupper(*cp)-'A'+10) < base) {
		result = result*base + value;
		cp++;
	}
	if (endp)
		*endp = (char *)cp;
	return result;
}

/**
 * simple_strtol - convert a string to a signed long
 * @cp: The start of the string
 * @endp: A pointer to the end of the parsed string will be placed here
 * @base: The number base to use
 */
long simple_strtol(const char *cp,char **endp,unsigned int base)
{
	if(*cp=='-')
		return -simple_strtoul(cp+1,endp,base);
	return simple_strtoul(cp,endp,base);
}

/**
 * simple_strtoull - convert a string to an unsigned long
 * @cp: The start of the string
 * @endp: A pointer to the end of the parsed string will be placed here
 * @base: The number base to use
 */
unsigned long simple_strtoull(const char *cp,char **endp,unsigned int base)
{
	unsigned long result = 0,value;

	if (!base) {
		base = 10;
		if (*cp == '0') {
			base = 8;
			cp++;
			if ((*cp == 'x') && isxdigit(cp[1])) {
				cp++;
				base = 16;
			}
		}
	}
	while (isxdigit(*cp) && (value = isdigit(*cp) ? *cp-'0' : (islower(*cp)
	    ? toupper(*cp) : *cp)-'A'+10) < base) {
		result = result*base + value;
		cp++;
	}
	if (endp)
		*endp = (char *)cp;
	return result;
}

/**
 * simple_strtoll - convert a string to a signed long
 * @cp: The start of the string
 * @endp: A pointer to the end of the parsed string will be placed here
 * @base: The number base to use
 */
long simple_strtoll(const char *cp,char **endp,unsigned int base)
{
	if(*cp=='-')
		return -simple_strtoull(cp+1,endp,base);
	return simple_strtoull(cp,endp,base);
}

static int skip_atoi(const char **s)
{
	int i=0;

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

#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 LARGE	64		/* use 'ABCDEF' instead of 'abcdef' */

int do_div(long * n, int base) 
{
   int __res; 
   __res = ((unsigned long)(*n))%(unsigned) base; 
   (*n) = ((unsigned long)(*n))/(unsigned) base;  
   return __res;
 }



static char * number(char * buf, char * end, long num, int base, int size, int precision, int type)
{
	char c,sign,tmp[66];
	const char *digits;
	static const char small_digits[] = "0123456789abcdefghijklmnopqrstuvwxyz";
	static const char large_digits[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
	int i;

	digits = (type & LARGE) ? large_digits : small_digits;
	if (type & LEFT)
		type &= ~ZEROPAD;
	if (base < 2 || base > 36)
		return 0;
	c = (type & ZEROPAD) ? '0' : ' ';
	sign = 0;
	if (type & SIGN) {
		if (num < 0) {
			sign = '-';
			num = -num;
			size--;
		} else if (type & PLUS) {
			sign = '+';
			size--;
		} else if (type & SPACE) {
			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) {
			if (buf <= end)
				*buf = ' ';
			++buf;
		}
	}
	if (sign) {
		if (buf <= end)
			*buf = sign;
		++buf;
	}
	if (type & SPECIAL) {
		if (base==8) {
			if (buf <= end)
				*buf = '0';
			++buf;
		} else if (base==16) {
			if (buf <= end)
				*buf = '0';
			++buf;
			if (buf <= end)
				*buf = digits[33];
			++buf;
		}
	}
	if (!(type & LEFT)) {
		while (size-- > 0) {
			if (buf <= end)
				*buf = c;
			++buf;
		}
	}
	while (i < precision--) {
		if (buf <= end)
			*buf = '0';
		++buf;
	}
	while (i-- > 0) {
		if (buf <= end)
			*buf = tmp[i];
		++buf;
	}
	while (size-- > 0) {
		if (buf <= end)
			*buf = ' ';
		++buf;
	}
	return buf;
}

/**
* vsnprintf - Format a string and place it in a buffer
* @buf: The buffer to place the result into
* @size: The size of the buffer, including the trailing null space
* @fmt: The format string to use
* @args: Arguments for the format string
*
* Call this function if you are already dealing with a va_list.
* You probably want snprintf instead.
 */
int vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
{
	int len;
	unsigned long num;
	int i, base;
	char *str, *end, c;
	const char *s;

	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 */
				/* 'z' support added 23/7/1999 S.H.    */
				/* 'z' changed to 'Z' --davidm 1/25/99 */

	str = buf;
	end = buf + size - 1;

	if (end < buf - 1) {
		end = ((void *) -1);
		size = end - buf + 1;
	}

	for (; *fmt ; ++fmt) {
		if (*fmt != '%') {
			if (str <= end)
				*str = *fmt;
			++str;
			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 (isdigit(*fmt))
			field_width = skip_atoi(&fmt);
		else if (*fmt == '*') {
			++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 (isdigit(*fmt))
				precision = skip_atoi(&fmt);
			else if (*fmt == '*') {
				++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' ||
		    *fmt =='Z' || *fmt == 'z') {
			qualifier = *fmt;
			++fmt;
			if (qualifier == 'l' && *fmt == 'l') {
				qualifier = 'L';
				++fmt;
			}
		}

		/* default base */
		base = 10;

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

			case 's':
				s = va_arg(args, char *);
				if ((unsigned long)s < PAGE_SIZE)
					s = "<NULL>";

				len = strnlen(s, precision);

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