78 lines
1.9 KiB
C
78 lines
1.9 KiB
C
/* printf.c -- format and print data */
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/* Copyright (c) 2020 Renaud Fivet */
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#include <stdarg.h>
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#include <stdio.h>
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#include "system.h" /* kputc(), kputs() */
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static int kputu( unsigned u, unsigned d) {
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char s[ 12] ; /* room for 11 octal digit + EOS */
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char *p = &s[ sizeof s - 1] ; /* point to last byte */
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*p = 0 ; /* null terminated string */
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do {
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unsigned r = u % d ;
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u /= d ;
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*--p = "0123456789ABCDEF"[ r] ;
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} while( u) ;
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return kputs( p) ;
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}
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static int kputi( int i) {
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int flag = i < 0 ;
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if( flag) {
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i = -i ;
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kputc( '-') ;
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}
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return flag + kputu( i, 10) ;
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}
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int printf( const char *fmt, ...) {
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va_list ap ;
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int cnt = 0 ;
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int c ; /* current char in format string */
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va_start( ap, fmt) ;
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while( ( c = *fmt++) != 0)
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if( c != '%') {
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cnt += 1 ; kputc( c) ;
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} else if( ( c = *fmt++) == 0) {
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cnt += 1 ; kputc( '%') ;
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break ;
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} else
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switch( c) {
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case 'c':
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cnt += 1 ; kputc( va_arg( ap, int /* char */)) ;
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break ;
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case 'o':
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cnt += kputu( va_arg( ap, unsigned), 8) ;
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break ;
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case 'u':
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cnt += kputu( va_arg( ap, unsigned), 10) ;
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break ;
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case 'x':
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case 'X':
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cnt += kputu( va_arg( ap, unsigned), 16) ;
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break ;
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case 'i':
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case 'd':
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cnt += kputi( va_arg( ap, int)) ;
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break ;
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case 's':
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cnt += kputs( va_arg( ap, char *)) ;
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break ;
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default:
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cnt += 1 ; kputc( '%') ;
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/* fallthrough */
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case '%':
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cnt += 1 ; kputc( c) ;
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}
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va_end( ap) ;
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return cnt ;
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}
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/* end of printf.c */
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