/*****************************************************************************
Stripped-down printf()
Chris Giese <geezer@execpc.com> http://www.execpc.com/~geezer
Release date: Dec 12, 2003
This code is public domain (no copyright).
You can do whatever you want with it.
Revised Dec 12, 2003
- fixed vsprintf() and sprintf() in test code
Revised Jan 28, 2002
- changes to make characters 0x80-0xFF display properly
Revised June 10, 2001
- changes to make vsprintf() terminate string with '\0'
Revised May 12, 2000
- math in DO_NUM is now unsigned, as it should be
- %0 flag (pad left with zeroes) now works
- actually did some TESTING, maybe fixed some other bugs
%[flag][width][.prec][mod][conv]
flag: - left justify, pad right w/ blanks DONE
0 pad left w/ 0 for numerics DONE
+ always print sign, + or - no
' ' (blank) no
# (???) no
width: (field width) DONE
prec: (precision) no
conv: d,i decimal int DONE
u decimal unsigned DONE
o octal DONE
x,X hex DONE
f,e,g,E,G float no
c char DONE
s string DONE
p ptr DONE
mod: N near ptr DONE
F far ptr no
h short (16-bit) int DONE
l long (32-bit) int DONE
L long long (64-bit) int no
*****************************************************************************/
#include <string.h> /* strlen() */
#include <stdio.h> /* stdout, putchar(), fputs() (but not printf() :) */
#if 0
#include <stdarg.h> /* va_list, va_start(), va_arg(), va_end() */
#else
/* home-brew STDARG.H, also public-domain: */
/* Assume: width of stack == width of int. Don't use sizeof(char *) or
other pointer because sizeof(char *)==4 for LARGE-model 16-bit code.
Assume: width is a power of 2 */
#define STACK_WIDTH sizeof(int)
/* Round up object width so it's an even multiple of STACK_WIDTH.
Using & for division here, so STACK_WIDTH must be a power of 2. */
#define TYPE_WIDTH(TYPE) ((sizeof(TYPE) + STACK_WIDTH - 1) & ~(STACK_WIDTH - 1))
/* point the va_list pointer to LASTARG,
then advance beyond it to the first variable arg */
#define va_start(PTR, LASTARG) PTR = (va_list)((char *)&(LASTARG) + TYPE_WIDTH(LASTARG))
#define va_end(PTR) /* nothing */
/* Increment the va_list pointer, then return
(evaluate to, actually) the previous value of the pointer.
WHEEE! At last; a valid use for the C comma operator! */
#define va_arg(PTR, TYPE) ( (char *)(PTR) += TYPE_WIDTH(TYPE) , *((TYPE *)((char *)(PTR) - TYPE_WIDTH(TYPE))) )
/* Every other compiler/libc seems to be using 'void *', so...
(I _was_ using 'unsigned char *') */
typedef void *va_list;
#endif
/* flags used in processing format string */
#define PR_LJ 0x01 /* left justify */
#define PR_CA 0x02 /* use A-F instead of a-f for hex */
#define PR_SG 0x04 /* signed numeric conversion (%d vs. %u) */
#define PR_32 0x08 /* long (32-bit) numeric conversion */
#define PR_16 0x10 /* short (16-bit) numeric conversion */
#define PR_WS 0x20 /* PR_SG set and num was < 0 */
#define PR_LZ 0x40 /* pad left with '0' instead of ' ' */
#define PR_FP 0x80 /* pointers are far */
/* largest number handled is 2^32-1, lowest radix handled is 8.
2^32-1 in base 8 has 11 digits (add 5 for trailing NUL and for slop) */
#define PR_BUFLEN 16
typedef int (*fnptr_t)(unsigned c, void **helper);
/*****************************************************************************
name: do_printf
action: minimal subfunction for ?printf, calls function
'fn' with arg 'ptr' for each character to be output
returns:total number of characters output
*****************************************************************************/
int do_printf(const char *fmt, va_list args, fnptr_t fn, void *ptr)
{
unsigned flags, actual_wd, count, given_wd;
unsigned char *where, buf[PR_BUFLEN];
unsigned char state, radix;
long num;
state = flags = count = given_wd = 0;
/* begin scanning format specifier list */
for(; *fmt; fmt++)
{
switch(state)
{
/* STATE 0: AWAITING % */
case 0:
if(*fmt != '%') /* not %... */
{
fn(*fmt, &ptr); /* ...just echo it */
count++;
break;
}
/* found %, get next char and advance state to check if next char is a flag */
state++;
fmt++;
/* FALL THROUGH */
/* STATE 1: AWAITING FLAGS (%-0) */
case 1:
if(*fmt == '%') /* %% */
{
fn(*fmt, &ptr);
count++;
state = flags = given_wd = 0;
break;
}
if(*fmt == '-')
{
if(flags & PR_LJ)/* %-- is illegal */
state = flags = given_wd = 0;
else
flags |= PR_LJ;
break;
}
/* not a flag char: advance state to check if it's field width */
state++;
/* check now for '%0...' */
if(*fmt == '0')
{
flags |= PR_LZ;
fmt++;
}
/* FALL THROUGH */
/* STATE 2: AWAITING (NUMERIC) FIELD WIDTH */
case 2:
if(*fmt >= '0' && *fmt <= '9')
{
given_wd = 10 * given_wd +
(*fmt - '0');
break;
}
/* not field width: advance state to check if it's a modifier */
state++;
/* FALL THROUGH */
/* STATE 3: AWAITING MODIFIER CHARS (FNlh) */
case 3:
if(*fmt == 'F')
{
flags |= PR_FP;
break;
}
if(*fmt == 'N')
break;
if(*fmt == 'l')
{
flags |= PR_32;
break;
}
if(*fmt == 'h')
{
flags |= PR_16;
break;
}
/* not modifier: advance state to check if it's a conversion char */
state++;
/* FALL THROUGH */
/* STATE 4: AWAITING CONVERSION CHARS (Xxpndiuocs) */
case 4:
where = buf + PR_BUFLEN - 1;
*where = '\0';
switch(*fmt)
{
case 'X':
flags |= PR_CA;
/* FALL THROUGH */
/* xxx - far pointers (%Fp, %Fn) not yet supported */
case 'x':
case 'p':
case 'n':
radix = 16;
goto DO_NUM;
case 'd':
case 'i':
flags |= PR_SG;
/* FALL THROUGH */
case 'u':
radix = 10;
goto DO_NUM;
case 'o':
radix = 8;
/* load the value to be printed. l=long=32 bits: */
DO_NUM: if(flags & PR_32)
num = va_arg(args, unsigned long);
/* h=short=16 bits (signed or unsigned) */
else if(flags & PR_16)
{
if(flags & PR_SG)
num = va_arg(args, short);
else
num = va_arg(args, unsigned short);
}
/* no h nor l: sizeof(int) bits (signed or unsigned) */
else
{
if(flags & PR_SG)
num = va_arg(args, int);
else
num = va_arg(args, unsigned int);
}
/* take care of sign */
if(flags & PR_SG)
{
if(num < 0)
{
flags |= PR_WS;
num = -num;
}
}
/* convert binary to octal/decimal/hex ASCII
OK, I found my mistake. The math here is _always_ unsigned */
do
{
unsigned long temp;
temp = (unsigned long)num % radix;
where--;
if(temp < 10)
*where = temp + '0';
else if(flags & PR_CA)
*where = temp - 10 + 'A';
else
*where = temp - 10 + 'a';
num = (unsigned long)num / radix;
}
while(num != 0);
goto EMIT;
case 'c':
/* disallow pad-left-with-zeroes for %c */
flags &= ~PR_LZ;
where--;
*where = (unsigned char)va_arg(args,
unsigned char);
actual_wd = 1;
goto EMIT2;
case 's':
/* disallow pad-left-with-zeroes for %s */
flags &= ~PR_LZ;
where = va_arg(args, unsigned char *);
EMIT:
actual_wd = strlen(where);
if(flags & PR_WS)
actual_wd++;
/* if we pad left with ZEROES, do the sign now */
if((flags & (PR_WS | PR_LZ)) ==
(PR_WS | PR_LZ))
{
fn('-', &ptr);
count++;
}
/* pad on left with spaces or zeroes (for right justify) */
EMIT2: if((flags & PR_LJ) == 0)
{
while(given_wd > actual_wd)
{
fn(flags & PR_LZ ?
'0' : ' ', &ptr);
count++;
given_wd--;
}
}
/* if we pad left with SPACES, do the sign now */
if((flags & (PR_WS | PR_LZ)) == PR_WS)
{
fn('-', &ptr);
count++;
}
/* emit string/char/converted number */
while(*where != '\0')
{
fn(*where++, &ptr);
count++;
}
/* pad on right with spaces (for left justify) */
if(given_wd < actual_wd)
given_wd = 0;
else given_wd -= actual_wd;
for(; given_wd; given_wd--)
{
fn(' ', &ptr);
count++;
}
break;
default:
break;
}
default:
state = flags = given_wd = 0;
break;
}
}
return count;
}
#if 1 /* testing */
/*****************************************************************************
SPRINTF
*****************************************************************************/
static int vsprintf_help(unsigned c, void **ptr)
{
char *dst;
dst = *ptr;
*dst++ = (char)c;
*ptr = dst;
return 0 ;
}
/*****************************************************************************
*****************************************************************************/
int vsprintf(char *buf, const char *fmt, va_list args)
{
int rv;
rv = do_printf(fmt, args, vsprintf_help, (void *)buf);
buf[rv] = '\0';
return rv;
}
/*****************************************************************************
*****************************************************************************/
int sprintf(char *buf, const char *fmt, ...)
{
va_list args;
int rv;
va_start(args, fmt);
rv = vsprintf(buf, fmt, args);
va_end(args);
return rv;
}
/*****************************************************************************
PRINTF
You must write your own putchar()
*****************************************************************************/
int vprintf_help(unsigned c, void **ptr)
{
putchar(c);
return 0 ;
}
/*****************************************************************************
*****************************************************************************/
int vprintf(const char *fmt, va_list args)
{
return do_printf(fmt, args, vprintf_help, NULL);
}
/*****************************************************************************
*****************************************************************************/
int printf(const char *fmt, ...)
{
va_list args;
int rv;
va_start(args, fmt);
rv = vprintf(fmt, args);
va_end(args);
return rv;
}
/*****************************************************************************
*****************************************************************************/
int main(void)
{
char buf[64];
sprintf(buf, "%u score and %i years ago...\n", 4, -7);
fputs(buf, stdout); /* puts() adds newline */
sprintf(buf, "-1L == 0x%lX == octal %lo\n", -1L, -1L);
fputs(buf, stdout); /* puts() adds newline */
printf("<%-08s> and <%08s> justified strings\n", "left", "right");
return 0;
}
#endif
