text: /* $Id$ */
  
  /* fseek( FILE *, long offset, int )
  
     This file is part of the Public Domain C Library (PDCLib).
     Permission is granted to use, modify, and / or redistribute at will.
  */
  
  #include <stdio.h>
  
  #ifndef REGTEST
  #include <_PDCLIB_io.h>
  
  int _PDCLIB_fseek_unlocked( FILE * stream, long loffset, int whence )
  {
      _PDCLIB_int64_t offset = loffset;
      if ( stream->status & _PDCLIB_FWRITE )
      {
          if ( _PDCLIB_flushbuffer( stream ) == EOF )
          {
              return EOF;
          }
      }
      stream->status &= ~ _PDCLIB_EOFFLAG;
      if ( stream->status & _PDCLIB_FRW )
      {
          stream->status &= ~ ( _PDCLIB_FREAD | _PDCLIB_FWRITE );
      }
  
      if ( whence == SEEK_CUR )
      {
          whence  = SEEK_SET;
          offset += _PDCLIB_ftell64_unlocked( stream );
      }
  
      return ( _PDCLIB_seek( stream, offset, whence ) != EOF ) ? 0 : EOF;
  }
  
  int fseek( FILE * stream, long loffset, int whence )
  {
      _PDCLIB_flockfile( stream );
      int r = _PDCLIB_fseek_unlocked( stream, loffset, whence );
      _PDCLIB_funlockfile( stream );
      return r;
  }
  
  #endif
  
  #ifdef TEST
  #include <_PDCLIB_test.h>
  #include <string.h>
  
  int main( void )
  {
      FILE * fh;
      TESTCASE( ( fh = tmpfile() ) != NULL );
      TESTCASE( fwrite( teststring, 1, strlen( teststring ), fh ) == strlen( teststring ) );
      /* General functionality */
      TESTCASE( fseek( fh, -1, SEEK_END ) == 0  );
      TESTCASE( (size_t)ftell( fh ) == strlen( teststring ) - 1 );
      TESTCASE( fseek( fh, 0, SEEK_END ) == 0 );
      TESTCASE( (size_t)ftell( fh ) == strlen( teststring ) );
      TESTCASE( fseek( fh, 0, SEEK_SET ) == 0 );
      TESTCASE( ftell( fh ) == 0 );
      TESTCASE( fseek( fh, 5, SEEK_CUR ) == 0 );
      TESTCASE( ftell( fh ) == 5 );
      TESTCASE( fseek( fh, -3, SEEK_CUR ) == 0 );
      TESTCASE( ftell( fh ) == 2 );
      /* Checking behaviour around EOF */
      TESTCASE( fseek( fh, 0, SEEK_END ) == 0 );
      TESTCASE( ! feof( fh ) );
      TESTCASE( fgetc( fh ) == EOF );
      TESTCASE( feof( fh ) );
      TESTCASE( fseek( fh, 0, SEEK_END ) == 0 );
      TESTCASE( ! feof( fh ) );
      /* Checking undo of ungetc() */
      TESTCASE( fseek( fh, 0, SEEK_SET ) == 0 );
      TESTCASE( fgetc( fh ) == teststring[0] );
      TESTCASE( fgetc( fh ) == teststring[1] );
      TESTCASE( fgetc( fh ) == teststring[2] );
      TESTCASE( ftell( fh ) == 3 );
      TESTCASE( ungetc( teststring[2], fh ) == teststring[2] );
      TESTCASE( ftell( fh ) == 2 );
      TESTCASE( fgetc( fh ) == teststring[2] );
      TESTCASE( ftell( fh ) == 3 );
      TESTCASE( ungetc( 'x', fh ) == 'x' );
      TESTCASE( ftell( fh ) == 2 );
      TESTCASE( fgetc( fh ) == 'x' );
      TESTCASE( ungetc( 'x', fh ) == 'x' );
      TESTCASE( ftell( fh ) == 2 );
      TESTCASE( fseek( fh, 2, SEEK_SET ) == 0 );
      TESTCASE( fgetc( fh ) == teststring[2] );
      /* PDCLIB-7: Check that we handle the underlying file descriptor correctly
       *           in the SEEK_CUR case */
      TESTCASE( fseek( fh, 10, SEEK_SET ) == 0 );
      TESTCASE( ftell( fh ) == 10l );
      TESTCASE( fseek( fh, 0, SEEK_CUR ) == 0 );
      TESTCASE( ftell( fh ) == 10l );
      TESTCASE( fseek( fh, 2, SEEK_CUR ) == 0 );
      TESTCASE( ftell( fh ) == 12l );
      TESTCASE( fseek( fh, -1, SEEK_CUR ) == 0 );
      TESTCASE( ftell( fh ) == 11l );
      /* Checking error handling */
      TESTCASE( fseek( fh, -5, SEEK_SET ) == -1 );
      TESTCASE( fseek( fh, 0, SEEK_END ) == 0 );
      TESTCASE( fclose( fh ) == 0 );
      return TEST_RESULTS;
  }
  
  #endif
  
  