《操作系统》的实验代码。
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#include <defs.h>
#include <stdio.h>
#include <syscall.h>
/* *
* cputch - writes a single character @c to stdout, and it will
* increace the value of counter pointed by @cnt.
* */
static void
cputch(int c, int *cnt) {
sys_putc(c);
(*cnt) ++;
}
/* *
* vcprintf - format a string and writes it to stdout
*
* The return value is the number of characters which would be
* written to stdout.
*
* Call this function if you are already dealing with a va_list.
* Or you probably want cprintf() instead.
* */
int
vcprintf(const char *fmt, va_list ap) {
int cnt = 0;
vprintfmt((void*)cputch, &cnt, fmt, ap);
return cnt;
}
/* *
* cprintf - formats a string and writes it to stdout
*
* The return value is the number of characters which would be
* written to stdout.
* */
int
cprintf(const char *fmt, ...) {
va_list ap;
va_start(ap, fmt);
int cnt = vcprintf(fmt, ap);
va_end(ap);
return cnt;
}
/* *
* cputs- writes the string pointed by @str to stdout and
* appends a newline character.
* */
int
cputs(const char *str) {
int cnt = 0;
char c;
while ((c = *str ++) != '\0') {
cputch(c, &cnt);
}
cputch('\n', &cnt);
return cnt;
}