X-Git-Url: https://pd.if.org/git/?p=pdclib;a=blobdiff_plain;f=functions%2Fstdio%2Fftell.c;h=9731e33368ae23364110f22dba1421ddd1d5cc0c;hp=29c360a2fd55d82f1d8569c67c6c3332e5f7fef2;hb=da0f3f353d417fed71f358a48d5d5394145e460d;hpb=ef6aa72f40326153ba99e833340ace354799ed95

diff --git a/functions/stdio/ftell.c b/functions/stdio/ftell.c
index 29c360a..9731e33 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).
@@ -7,46 +5,42 @@
 */
 
 #include <stdio.h>
+#include <stdint.h>
 #include <limits.h>
+#include <errno.h>
 
 #ifndef REGTEST
+#include "_PDCLIB_io.h"
 
-long int ftell( struct _PDCLIB_file_t * stream )
+long int _PDCLIB_ftell_unlocked( FILE * 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 ) ) )
+    uint_fast64_t off64 = _PDCLIB_ftell64_unlocked( stream );
+
+    if ( off64 > LONG_MAX )
     {
         /* integer overflow */
-        _PDCLIB_errno = _PDCLIB_ERANGE;
+        errno = ERANGE;
         return -1;
     }
-    return (long int)( stream->pos.offset - ( ( (int)stream->bufend - (int)stream->bufidx ) + stream->ungetidx ) );
+    return off64;
+}
+
+long int ftell( FILE * stream )
+{
+    _PDCLIB_flockfile( stream );
+    long int off = _PDCLIB_ftell_unlocked( stream );
+    _PDCLIB_funlockfile( stream );
+    return off;
 }
 
 #endif
 
 #ifdef TEST
-#include <_PDCLIB_test.h>
-
+#include "_PDCLIB_test.h"
 #include <stdlib.h>
+#ifndef REGTEST
+#include "_PDCLIB_io.h"
+#endif
 
 int main( void )
 {
@@ -62,6 +56,13 @@ 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' );