update CLib

git-svn-id: svn://kolibrios.org@614 a494cfbc-eb01-0410-851d-a64ba20cac60

programs/develop/open watcom/trunk/clib/streamio/fseek.c

@@ -0,0 +1,157 @@
+/****************************************************************************
+*
+*                            Open Watcom Project
+*
+*    Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
+*
+*  ========================================================================
+*
+*    This file contains Original Code and/or Modifications of Original
+*    Code as defined in and that are subject to the Sybase Open Watcom
+*    Public License version 1.0 (the 'License'). You may not use this file
+*    except in compliance with the License. BY USING THIS FILE YOU AGREE TO
+*    ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
+*    provided with the Original Code and Modifications, and is also
+*    available at www.sybase.com/developer/opensource.
+*
+*    The Original Code and all software distributed under the License are
+*    distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+*    EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM
+*    ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF
+*    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
+*    NON-INFRINGEMENT. Please see the License for the specific language
+*    governing rights and limitations under the License.
+*
+*  ========================================================================
+*
+* Description:  Implementation of fseek - set stream position.
+*
+****************************************************************************/
+
+
+#include "variety.h"
+#include <stdio.h>
+#include <errno.h>
+#include <unistd.h>
+#include "fileacc.h"
+#include "rtdata.h"
+#include "seterrno.h"
+#include "flush.h"
+
+
+static int __update_buffer( long diff, FILE *fp )
+{
+    /*
+      diff is relative to fp->_ptr
+      if diff is within the buffer update the pointers and return 0
+      otherwise update the pointers and return 1
+    */
+    if( diff <= fp->_cnt  &&  diff >= (_FP_BASE(fp) - fp->_ptr) ) {
+        fp->_flag &= ~(_EOF);
+        fp->_ptr += diff;
+        fp->_cnt -= diff;
+        return( 0 );
+    }
+    return( 1 );
+}
+
+
+/*
+ * This used to be in __update_buffer(), but we don't want to do this until
+ * AFTER we've made certain that lseek() will be a successful one.
+ */
+static void __reset_buffer( FILE *fp )
+{
+    fp->_flag &= ~(_EOF);
+    fp->_ptr = _FP_BASE(fp);
+    fp->_cnt = 0;
+}
+
+
+_WCRTLINK int fseek( FILE *fp, long offset, int origin )
+{
+    _ValidFile( fp, -1 );
+    _AccessFile( fp );
+    /*
+      if the file is open for any sort of writing we must ensure that
+      the buffer is flushed when dirty so that the integrity of the
+      data is preserved.
+      if there is an ungotten character in the buffer then the data must
+      be discarded to ensure the integrity of the data
+    */
+    if( fp->_flag & (_WRITE | _UNGET) ) {
+        if( fp->_flag & _DIRTY ) {
+            /*
+              the __flush routine aligns the DOS file pointer with the
+              start of the resulting cleared buffer, as such, the SEEK_CUR
+              code used for the non-_DIRTY buffer case is not required
+            */
+            if( __flush( fp ) ) {
+                // assume __flush set the errno value
+                // if erroneous input, override errno value
+                if( origin == SEEK_SET && offset < 0 ) {
+                    __set_errno( EINVAL );
+                }
+                _ReleaseFile( fp );
+                return( -1 );
+            }
+        } else {
+            if( origin == SEEK_CUR ) {
+                offset -= fp->_cnt;
+            }
+            fp->_ptr = _FP_BASE(fp);
+            fp->_cnt = 0;
+        }
+        fp->_flag &= ~(_EOF|_UNGET);
+        if( lseek( fileno( fp ), offset, origin ) == -1 ) {
+            _ReleaseFile( fp );
+            return( -1 );
+        }
+    } else {
+        // file is open for read only,
+        // no characters have been ungotten
+        // the OS file pointer is at fp->_ptr + fp->_cnt relative to the
+        // FILE* buffer
+        switch( origin ) {
+        case SEEK_CUR:
+        {   long    ptr_delta = fp->_cnt;
+
+            if( __update_buffer( offset, fp ) ) {
+                offset -= ptr_delta;
+                if( lseek( fileno( fp ), offset, origin ) == -1 ) {
+                    _ReleaseFile( fp );
+                    return( -1 );
+                }
+                __reset_buffer(fp);
+            }
+        }   break;
+        case SEEK_SET:
+        {   long    file_ptr = tell( fileno( fp ) );
+
+            file_ptr -= fp->_cnt;
+            if( __update_buffer( offset - file_ptr, fp ) ) {
+                if( lseek( fileno( fp ), offset, origin ) == -1 ) {
+                    _ReleaseFile( fp );
+                    return( -1 );
+                }
+                __reset_buffer(fp);
+            }
+        }   break;
+        case SEEK_END:
+            fp->_flag &= ~(_EOF);
+            fp->_ptr = _FP_BASE(fp);
+            fp->_cnt = 0;
+            if( lseek( fileno( fp ), offset, origin ) == -1 ) {
+                _ReleaseFile( fp );
+                return( -1 );
+            }
+            break;
+        default:
+            __set_errno( EINVAL );
+            _ReleaseFile( fp );
+            return( -1 );
+        }
+    }
+    _ReleaseFile( fp );
+    return( 0 );            /* indicate success */
+}