ungetc.c

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#include <stdio.h>
 
#include "user/common/file.h"
 
int ungetc(int c, FILE* stream)
{
    int rc;
 
    mtx_lock(&stream->mtx);
 
    if (c == EOF || stream->ungetIndex == _UNGETC_MAX)
    {
        rc = -1;
    }
    else
    {
        rc = stream->ungetBuf[stream->ungetIndex++] = (unsigned char)c;
    }
 
    mtx_unlock(&stream->mtx);
 
    return rc;
}