-/* $Id$ */
-
/* ftell( FILE * )
This file is part of the Public Domain C Library (PDCLib).
long int ftell( struct _PDCLIB_file_t * stream )
{
- /* FIXME: A bit too fuzzy in the head now. stream->ungetidx should be in here
- somewhere.
+ /* ftell() must take into account:
+ - the actual *physical* offset of the file, i.e. the offset as recognized
+ by the operating system (and stored in stream->pos.offset); and
+ - any buffers held by PDCLib, which
+ - in case of unwritten buffers, count in *addition* to the offset; or
+ - in case of unprocessed pre-read buffers, count in *substraction* to
+ the offset. (Remember to count ungetidx into this number.)
+ Conveniently, the calculation ( ( bufend - bufidx ) + ungetidx ) results
+ in just the right number in both cases:
+ - in case of unwritten buffers, ( ( 0 - unwritten ) + 0 )
+ i.e. unwritten bytes as negative number
+ - in case of unprocessed pre-read, ( ( preread - processed ) + unget )
+ i.e. unprocessed bytes as positive number.
+ That is how the somewhat obscure return-value calculation works.
+ */
+ /* If offset is too large for return type, report error instead of wrong
+ offset value.
*/
- if ( stream->pos.offset > ( LONG_MAX - stream->bufidx ) )
+ /* TODO: Check what happens when ungetc() is called on a stream at offset 0 */
+ if ( ( stream->pos.offset - stream->bufend ) > ( LONG_MAX - ( stream->bufidx - stream->ungetidx ) ) )
{
/* integer overflow */
- _PDCLIB_errno = _PDCLIB_EINVAL;
+ _PDCLIB_errno = _PDCLIB_ERANGE;
return -1;
}
- /* Position of start-of-buffer, plus:
- - buffered, unwritten content (for output streams), or
- - already-parsed content from buffer (for input streams)
- */
- return (long int)( stream->pos.offset + stream->bufidx - stream->ungetidx );
+ return (long int)( stream->pos.offset - ( ( (int)stream->bufend - (int)stream->bufidx ) + stream->ungetidx ) );
}
#endif
#ifdef TEST
-#include <_PDCLIB_test.h>
+
+#include "_PDCLIB_test.h"
#include <stdlib.h>
*/
char * buffer = (char*)malloc( 4 );
FILE * fh;
- remove( testfile );
- TESTCASE( ( fh = fopen( testfile, "w+" ) ) != NULL );
+ TESTCASE( ( fh = tmpfile() ) != NULL );
TESTCASE( setvbuf( fh, buffer, _IOLBF, 4 ) == 0 );
+ /* Testing ungetc() at offset 0 */
+ rewind( fh );
+ TESTCASE( ungetc( 'x', fh ) == 'x' );
+ TESTCASE( ftell( fh ) == -1l );
+ rewind( fh );
+ TESTCASE( ftell( fh ) == 0l );
+ /* Commence "normal" tests */
TESTCASE( fputc( '1', fh ) == '1' );
TESTCASE( fputc( '2', fh ) == '2' );
TESTCASE( fputc( '3', fh ) == '3' );
TESTCASE_NOREG( fh->bufidx == 0 );
/* Reading back first character after rewind for basic read check */
TESTCASE( fgetc( fh ) == '1' );
- TESTCASE( fclose( fh ) == 0 );
/* TODO: t.b.c. */
- remove( testfile );
+ TESTCASE( fclose( fh ) == 0 );
return TEST_RESULTS;
}
#endif
-