nf_getc.c

#include <stdio.h>

#include "stdio_impl.h"

#ifdef STDIO_NO_FILE_IO
/* "No file system" fgetc, ungetc */

static char ungetbuf[UNGET];
static char ungetcnt = 0;

int fgetc(FILE *fp)
{
    int c;
     extern int getch(void);

    if (fp == stdin) {
        if (ungetcnt) {
            c = ungetbuf[--ungetcnt];
        } else {
            c = getch();
        }
    } else {
        if (fp->ungetcnt) {
            c = fp->ungetbuf[--fp->ungetcnt];
        } else {
            c = fp->source[fp->count];
            if (c == '\0') {
                c = EOF;
            } else {
                ++fp->count;
            }
        }
    }
    return c;
}

int ungetc(int c, FILE *fp)
{
    if (c == EOF) {
        return EOF;
    }
    if (fp == stdin) {
        if (ungetcnt != UNGET) {
            ungetbuf[ungetcnt++] = (char)c;
        }
        else {
            return EOF;
        }
    } else {
        if (fp->ungetcnt != UNGET) {
            fp->ungetbuf[fp->ungetcnt++] = (char)c;
        } else {
            return EOF;
        }
    }
    return (unsigned char)c;
}

#endif