gis/seek.c

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/*!
 * \file lib/gis/seek.c
 *
 * \brief GIS Library - file seek routines
 *
 * (C) 2009-2010 by the GRASS Development Team
 *
 * This program is free software under the GNU General Public License
 * (>=v2). Read the file COPYING that comes with GRASS for details.
 *
 * \author Glynn Clements
 */
 
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <grass/gis.h>
#include <grass/glocale.h>
 
/*!
   \brief Get the current file position of the stream.
 
   \param fp file descriptor
 
   \return file position
   \return -1 on failure
 */
off_t G_ftell(FILE *fp)
{
#ifdef HAVE_FSEEKO
    return ftello(fp);
#else
    return (off_t)ftell(fp);
#endif
}
 
/*!
   \brief Change the file position of the stream.
 
   The value of <i>whence</i> must be one of the constants `SEEK_SET',
   `SEEK_CUR', or `SEEK_END', to indicate whether the <i>offset</i> is
   relative to the beginning of the file, the current file position, or
   the end of the file, respectively.
 
   \param fp file descriptor
   \param offset offset
   \param whence
 */
void G_fseek(FILE *fp, off_t offset, int whence)
{
#ifdef HAVE_FSEEKO
    if (fseeko(fp, offset, whence) != 0) {
        int err = errno;
        G_fatal_error(_("File read/write operation failed: %s (%d)"),
                      strerror(err), err);
    }
#else
    long loff = (long)offset;
 
    if ((off_t)loff != offset)
        G_fatal_error(_("Seek offset out of range"));
    if (fseek(fp, loff, whence) != 0) {
        int err = errno;
        G_fatal_error(_("File read/write operation failed: %s (%d)"),
                      strerror(err), err);
    }
#endif
}