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/* ftell( FILE * )
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>
#include <limits.h>
#ifndef REGTEST
long int ftell( struct _PDCLIB_file_t * stream )
{
/* 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.
*/
/* 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_ERANGE;
return -1;
}
return (long int)( stream->pos.offset - ( ( (int)stream->bufend - (int)stream->bufidx ) + stream->ungetidx ) );
}
#endif
#ifdef TEST
#include "_PDCLIB_test.h"
#include <stdlib.h>
int main( void )
{
/* Testing all the basic I/O functions individually would result in lots
of duplicated code, so I took the liberty of lumping it all together
here.
*/
/* The following functions delegate their tests to here:
fgetc fflush rewind fputc ungetc fseek
flushbuffer seek fillbuffer prepread prepwrite
*/
char * buffer = (char*)malloc( 4 );
FILE * fh;
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' );
/* Positions incrementing as expected? */
TESTCASE( ftell( fh ) == 3l );
TESTCASE_NOREG( fh->pos.offset == 0l );
TESTCASE_NOREG( fh->bufidx == 3l );
/* Buffer properly flushed when full? */
TESTCASE( fputc( '4', fh ) == '4' );
TESTCASE_NOREG( fh->pos.offset == 4l );
TESTCASE_NOREG( fh->bufidx == 0 );
/* fflush() resetting positions as expected? */
TESTCASE( fputc( '5', fh ) == '5' );
TESTCASE( fflush( fh ) == 0 );
TESTCASE( ftell( fh ) == 5l );
TESTCASE_NOREG( fh->pos.offset == 5l );
TESTCASE_NOREG( fh->bufidx == 0l );
/* rewind() resetting positions as expected? */
rewind( fh );
TESTCASE( ftell( fh ) == 0l );
TESTCASE_NOREG( fh->pos.offset == 0 );
TESTCASE_NOREG( fh->bufidx == 0 );
/* Reading back first character after rewind for basic read check */
TESTCASE( fgetc( fh ) == '1' );
/* TODO: t.b.c. */
TESTCASE( fclose( fh ) == 0 );
return TEST_RESULTS;
}
#endif
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