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/**
** @file sprint.c
**
** @author Numerous CSCI-452 classes
**
** @brief C implementations of common library functions
*/
#ifndef SPRINT_SRC_INC
#define SPRINT_SRC_INC
#include <common.h>
#include <lib.h>
/**
** sprint(dst,fmt,...) - formatted output into a string buffer
**
** @param dst The string buffer
** @param fmt Format string
**
** The format string parameter is followed by zero or more additional
** parameters which are interpreted according to the format string.
**
** NOTE: assumes the buffer is large enough to hold the result string
**
** NOTE: relies heavily on the x86 parameter passing convention
** (parameters are pushed onto the stack in reverse order as
** 32-bit values).
*/
void sprint(char *dst, char *fmt, ...)
{
int32_t *ap;
char buf[12];
char ch;
char *str;
int leftadjust;
int width;
int len;
int padchar;
/*
** Get characters from the format string and process them
**
** We use the "old-school" method of handling variable numbers
** of parameters. We assume that parameters are passed on the
** runtime stack in consecutive longwords; thus, if the first
** parameter is at location 'x', the second is at 'x+4', the
** third at 'x+8', etc. We use a pointer to a 32-bit thing
** to point to the next "thing", and interpret it according
** to the format string.
*/
// get the pointer to the first "value" parameter
ap = (int *)(&fmt) + 1;
// iterate through the format string
while ((ch = *fmt++) != '\0') {
/*
** Is it the start of a format code?
*/
if (ch == '%') {
/*
** Yes, get the padding and width options (if there).
** Alignment must come at the beginning, then fill,
** then width.
*/
leftadjust = 0;
padchar = ' ';
width = 0;
ch = *fmt++;
if (ch == '-') {
leftadjust = 1;
ch = *fmt++;
}
if (ch == '0') {
padchar = '0';
ch = *fmt++;
}
while (ch >= '0' && ch <= '9') {
width *= 10;
width += ch - '0';
ch = *fmt++;
}
/*
** What data type do we have?
*/
switch (ch) {
case 'c': // characters are passed as 32-bit values
ch = *ap++;
buf[0] = ch;
buf[1] = '\0';
dst = padstr(dst, buf, 1, width, leftadjust, padchar);
break;
case 'd':
len = cvtdec(buf, *ap++);
dst = padstr(dst, buf, len, width, leftadjust, padchar);
break;
case 's':
str = (char *)(*ap++);
dst = padstr(dst, str, -1, width, leftadjust, padchar);
break;
case 'x':
len = cvthex(buf, *ap++);
dst = padstr(dst, buf, len, width, leftadjust, padchar);
break;
case 'o':
len = cvtoct(buf, *ap++);
dst = padstr(dst, buf, len, width, leftadjust, padchar);
break;
case 'u':
len = cvtuns(buf, *ap++);
dst = padstr(dst, buf, len, width, leftadjust, padchar);
break;
}
} else {
// no, it's just an ordinary character
*dst++ = ch;
}
}
// NUL-terminate the result
*dst = '\0';
}
#endif
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