cc65/libsrc/common/fseek.c

/*
 * fseek.c
 *
 * Christian Groessler, 2000-08-07
 * Ullrich von Bassewitz, 2004-05-12
 */



#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include "_file.h"



/*****************************************************************************/
/*     	    	     		     Code				     */
/*****************************************************************************/



int __fastcall__ fseek (register FILE* f, long offset, int whence)
{
    long res;

    /* Is the file open? */
    if ((f->f_flags & _FOPEN) == 0) {
        _errno = EINVAL;                /* File not open */
        return -1;
    }

    /* If we have a pushed back character, and whence is relative to the
     * current position, correct the offset.
     */
    if ((f->f_flags & _FPUSHBACK) && whence == SEEK_CUR) {
        --offset;
    }

    /* Do the seek */
    res = lseek(f->f_fd, offset, whence);

    /* If we had an error, set the error indicator on the stream, and
     * return -1. We will check for < 0 here, because that saves some code,
     * and we don't have files with 2 gigabytes in size anyway:-)
     */
    if (res < 0) {
        f->f_flags |= _FERROR;
        return -1;
    }

    /* The seek was successful. Discard any effects of the ungetc function,
     * and clear the end-of-file indicator.
     */
    f->f_flags &= ~(_FEOF | _FPUSHBACK);

    /* Done */
    return 0;
}