PDCLIB-7: Add _PDCLIB_ftell64 to give us full precision file positioning information...

[pdclib] / functions / stdio / ftell.c

diff --git a/functions/stdio/ftell.c b/functions/stdio/ftell.c
index e82ca48155e25d22e4fcacfb2f93858e3634f6c9..d39297f688ae9bc170360f5e5902eca020e2c4e4 100644 (file)
--- 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.
-    */
-    /* 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( stream );
+
+    if ( off64 > LONG_MAX )
     {
         /* integer overflow */
-        _PDCLIB_errno = _PDCLIB_ERANGE;
+        errno = ERANGE;
         return -1;
     }
-    long int res = ( stream->pos.offset - ( ( (int)stream->bufend - (int)stream->bufidx ) + stream->ungetidx ) );
-    return res;
+    return off64;
 }
 
 #endif