5 This file is part of the Public Domain C Library (PDCLib).
6 Permission is granted to use, modify, and / or redistribute at will.
14 long int ftell( struct _PDCLIB_file_t * stream )
16 /* ftell() must take into account:
17 - the actual *physical* offset of the file, i.e. the offset as recognized
18 by the operating system (and stored in stream->pos.offset); and
19 - any buffers held by PDCLib, which
20 - in case of unwritten buffers, count in *addition* to the offset; or
21 - in case of unprocessed pre-read buffers, count in *substraction* to
22 the offset. (Remember to count ungetidx into this number.)
23 Conveniently, the calculation ( ( bufend - bufidx ) + ungetidx ) results
24 in just the right number in both cases:
25 - in case of unwritten buffers, ( ( 0 - unwritten ) + 0 )
26 i.e. unwritten bytes as negative number
27 - in case of unprocessed pre-read, ( ( preread - processed ) + unget )
28 i.e. unprocessed bytes as positive number.
29 That is how the somewhat obscure return-value calculation works.
31 /* If offset is too large for return type, report error instead of wrong
32 offset value. Buffers may not be larger than INT_MAX so the casts are
35 /* FIXME: This calculation *underflows* when offset smaller than pre-read */
36 if ( ( stream->pos.offset - ( (int)stream->bufend + (int)stream->ungetidx ) ) > ( LONG_MAX - stream->bufidx ) )
38 /* integer overflow */
39 _PDCLIB_errno = _PDCLIB_ERANGE;
42 return (long int)( stream->pos.offset - ( ( (int)stream->bufend - (int)stream->bufidx ) + stream->ungetidx ) );
48 #include <_PDCLIB_test.h>
54 /* Testing all the basic I/O functions individually would result in lots
55 of duplicated code, so I took the liberty of lumping it all together
58 /* The following functions delegate their tests to here:
59 fgetc fflush rewind fputc ungetc fseek
60 flushbuffer seek fillbuffer prepread prepwrite
62 char * buffer = (char*)malloc( 4 );
64 TESTCASE( ( fh = tmpfile() ) != NULL );
65 TESTCASE( setvbuf( fh, buffer, _IOLBF, 4 ) == 0 );
66 TESTCASE( fputc( '1', fh ) == '1' );
67 TESTCASE( fputc( '2', fh ) == '2' );
68 TESTCASE( fputc( '3', fh ) == '3' );
69 /* Positions incrementing as expected? */
70 TESTCASE( ftell( fh ) == 3l );
71 TESTCASE_NOREG( fh->pos.offset == 0l );
72 TESTCASE_NOREG( fh->bufidx == 3l );
73 /* Buffer properly flushed when full? */
74 TESTCASE( fputc( '4', fh ) == '4' );
75 TESTCASE_NOREG( fh->pos.offset == 4l );
76 TESTCASE_NOREG( fh->bufidx == 0 );
77 /* fflush() resetting positions as expected? */
78 TESTCASE( fputc( '5', fh ) == '5' );
79 TESTCASE( fflush( fh ) == 0 );
80 TESTCASE( ftell( fh ) == 5l );
81 TESTCASE_NOREG( fh->pos.offset == 5l );
82 TESTCASE_NOREG( fh->bufidx == 0l );
83 /* rewind() resetting positions as expected? */
85 TESTCASE( ftell( fh ) == 0l );
86 TESTCASE_NOREG( fh->pos.offset == 0 );
87 TESTCASE_NOREG( fh->bufidx == 0 );
88 /* Reading back first character after rewind for basic read check */
89 TESTCASE( fgetc( fh ) == '1' );
91 TESTCASE( fclose( fh ) == 0 );