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/*! \file printf.c
\brief printf function
\author Matthew Ahrens <mahrens@acm.org>
*/
/*
* The contents of this file are subject to the Mozilla Public License
* Version 1.0 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS"
* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
* License for the specific language governing rights and limitations
* under the License.
*
* The Original Code is from the Brown Computer Science Department,
* Weenix support code.
*
* The Initial Developer of the Original Code is David Powell.
*
* Contributor(s): Matthew Ahrens <mahrens@acm.org>
*/
#include <stdarg.h>
static const char hexdigits[] = "0123456789ABCDEF";
static const char lhexdigits[] = "0123456789abcdef";
static const char empty_string[] = "(null string)";
/* This function takes an unsigned int and puts its ascii
* representation at a particular location in a buffer of given
* length. The radix used is must also be provided, as well as a
* string containing the characters used in the ascii representation.
*
* This function makes no attempt to handle two-byte characters.
*/
static int itoa(unsigned int value, char *dst, int pos, int len,
int radix, const char *digits)
{
char sbuf[10];
int spos;
spos = 0;
while(value) {
sbuf[spos] = value % radix;
spos++;
value /= radix;
}
if(!spos)
*sbuf = 0, spos = 1;
for(spos--; pos<len && spos>=0; pos++,spos--) {
dst[pos] = digits[(int)sbuf[spos]];
}
return pos-1;
}
/* This function takes a buffer, its length, a format specification,
* and a va_list, formats the provided data according the the format
* spec, and places the result in the buffer. It returns the length of
* the output. The only format options supported by this function
* are:
* %d - decimal unsigned int
* %i - " " "
* %x - hexidecimal unsigned int (lowercase letters)
* %X - " " " (uppercase letters)
* %c - character
* %s - string
* %% - '%' character
*/
int vsnprintf(char *dst, int len, const char *fmt, va_list arg)
{
int pos;
int cc;
const char *temp;
unsigned int scratch;
for(pos=0, cc=0; (pos<len) && (cc=*fmt); pos++, fmt++) {
if(cc!='%')
dst[pos] = cc;
else {
cc = *(++fmt);
switch(cc) {
case 'd':
case 'i':
/* integer */
scratch = va_arg(arg, unsigned);
pos = itoa(scratch, dst, pos, len, 10,
hexdigits);
break;
case 'X':
/* hexadecimal (uppercase) */
scratch = va_arg(arg, unsigned);
pos = itoa(scratch, dst, pos, len, 16,
hexdigits);
break;
case 'x':
/* hexadecimal (lowercase) */
scratch = va_arg(arg, unsigned);
pos = itoa(scratch, dst, pos, len, 16,
lhexdigits);
break;
case 's':
/* string */
temp = va_arg(arg, const char*);
if(!temp)
temp = empty_string;
for(; pos<len && *temp; pos++, temp++) {
dst[pos] = *temp;
}
pos--;
break;
case 'c':
/* character */
dst[pos] = va_arg(arg, int);
break;
case '\0':
case '%':
dst[pos] = cc;
break;
}
if(!cc) {
break;
}
}
}
dst[pos++] = '\0';
return pos;
}
/* This function prints the specified format into the provided buffer
* taking care not to access beyond the end of the string.
*/
char *snprintf(char *dst, int len, const char *fmt, ...)
{
va_list arg;
va_start(arg, fmt);
(void) vsnprintf(dst, len, fmt, arg);
va_end(arg);
return dst;
}
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