X-Git-Url: https://pd.if.org/git/?a=blobdiff_plain;f=functions%2Fstdio%2Fftell.c;h=bf6f792b892d1fdd5eee9c4ffc60b63ba61bfd67;hb=d6f1494a4f38a212b29a13ee713885058dcf0fe7;hp=9838156a3901f1f7f729f02d0e64b716bf5d2295;hpb=e5112b619d1aae8ffc439389cfcbd3b2b4bd2454;p=pdclib

diff --git a/functions/stdio/ftell.c b/functions/stdio/ftell.c
index 9838156..bf6f792 100644
--- a/functions/stdio/ftell.c
+++ b/functions/stdio/ftell.c
@@ -1,5 +1,3 @@
-/* $Id$ */
-
 /* ftell( FILE * )
 
    This file is part of the Public Domain C Library (PDCLib).
@@ -7,24 +5,96 @@
 */
 
 #include <stdio.h>
+#include <limits.h>
 
 #ifndef REGTEST
 
 long int ftell( struct _PDCLIB_file_t * stream )
 {
-    /* TODO: Implement. */
-    return 0;
+    /* 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 "_PDCLIB_test.h"
+
+#include <stdlib.h>
 
 int main( void )
 {
-    TESTCASE( NO_TESTDRIVER );
+    /* 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
+