Comment cleanups.

[pdclib] / functions / stdio / ftell.c

diff --git a/functions/stdio/ftell.c b/functions/stdio/ftell.c
index e392a8b1f01de37121a2683c6a8ab2643f4d326d..af6542c0d713edd797eaeb80a5fdc6aeb3379a7a 100644 (file)
--- 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).
@@ -28,12 +26,11 @@ long int ftell( struct _PDCLIB_file_t * stream )
            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. Buffers may not be larger than INT_MAX so the casts are
-       safe.
+    /*  If offset is too large for return type, report error instead of wrong
+        offset value.
     */
-    /* FIXME: This calculation *underflows* when offset smaller than pre-read */
-    if ( ( stream->pos.offset - ( (int)stream->bufend + (int)stream->ungetidx ) ) > ( 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_ERANGE;
@@ -63,6 +60,13 @@ int main( void )
     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' );