X-Git-Url: https://pd.if.org/git/?a=blobdiff_plain;f=functions%2Fstdio%2Fftell.c;h=d39297f688ae9bc170360f5e5902eca020e2c4e4;hb=05556502a427911d4499c22b809ca7d366327d7c;hp=e392a8b1f01de37121a2683c6a8ab2643f4d326d;hpb=f495ef679088649341da616b815ddc7ff60cec7b;p=pdclib

diff --git a/functions/stdio/ftell.c b/functions/stdio/ftell.c
index e392a8b..d39297f 100644
--- a/functions/stdio/ftell.c
+++ b/functions/stdio/ftell.c
@@ -7,39 +7,23 @@
 */
 
 #include <stdio.h>
+#include <stdint.h>
 #include <limits.h>
+#include <errno.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. Buffers may not be larger than INT_MAX so the casts are
-       safe.
-    */
-    /* FIXME: This calculation *underflows* when offset smaller than pre-read */
-    if ( ( stream->pos.offset - ( (int)stream->bufend + (int)stream->ungetidx ) ) > ( LONG_MAX - stream->bufidx ) )
+    uint_fast64_t off64 = _PDCLIB_ftell64( 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;
 }
 
 #endif
@@ -63,6 +47,13 @@ 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' );