- ftruncate() ended up changing the current file position, contrary

to what it is supposed to do. Fixed.


git-svn-id: file:///Users/olsen/Code/migration-svn-zu-git/logical-line-staging/clib2/trunk@14888 87f5fb63-7c3d-0410-a384-fd976d0f7a62

library/changes

@@ -91,6 +91,9 @@
   entire library constructor/destructor functionality to use the
   same approach as libnix.
 
+- ftruncate() ended up changing the current file position, contrary
+  to what it is supposed to do. Fixed.
+
 
 c.lib 1.189 (5.3.2005)
 

library/stdio_fdhookentry.c

@@ -1,5 +1,5 @@
 /*
- * $Id: stdio_fdhookentry.c,v 1.21 2005-03-12 09:49:47 obarthel Exp $
+ * $Id: stdio_fdhookentry.c,v 1.22 2005-03-14 10:03:06 obarthel Exp $
  *
  * :ts=4
  *
@@ -151,17 +151,28 @@ __fd_hook_entry(
 
 			if(FLAG_IS_SET(fd->fd_Flags,FDF_APPEND))
 			{
+				LONG position;
+
 				SHOWMSG("appending data");
 
 				PROFILE_OFF();
 
-				if(Seek(file,0,OFFSET_END) >= 0)
+				position = Seek(file,0,OFFSET_END);
+				if(position >= 0)
 				{
 					if(FLAG_IS_SET(fd->fd_Flags,FDF_CACHE_POSITION))
 						fd->fd_Position = Seek(file,0,OFFSET_CURRENT);
 				}
 
 				PROFILE_ON();
+
+				if(position < 0)
+				{
+					D(("seek to end of file failed; ioerr=%ld",IoErr()));
+
+					fam->fam_Error = __translate_io_error_to_errno(IoErr());
+					goto out;
+				}
 			}
 
 			D(("write %ld bytes to position %ld from 0x%08lx",fam->fam_Size,Seek(file,0,OFFSET_CURRENT),fam->fam_Data));
@@ -349,6 +360,8 @@ __fd_hook_entry(
 
 						old_dir = CurrentDir(parent_dir);
 
+						/* ZZZ we probably ought to observe the current umask settings. */
+
 						flags = fib->fib_Protection ^ (FIBF_READ|FIBF_WRITE|FIBF_EXECUTE|FIBF_DELETE);
 
 						CLEAR_FLAG(flags,FIBF_EXECUTE);
@@ -454,18 +467,14 @@ __fd_hook_entry(
 
 					#if defined(UNIX_PATH_SEMANTICS)
 					{
-						if(NOT fib_is_valid && CANNOT __safe_examine_file_handle(file,fib))
-						{
-							fam->fam_Error = __translate_io_error_to_errno(IoErr());
+						/* Check if this operation failed because the file is shorter than
+						   the new file position. First, we need to find out if the file
+						   is really shorter than required. If not, then it must have
+						   been a different error. */
+						if((NOT fib_is_valid && CANNOT __safe_examine_file_handle(file,fib)) || (new_position <= fib->fib_Size))
 							goto out;
-						}
-
-						if(new_position <= fib->fib_Size)
-						{
-							fam->fam_Error = __translate_io_error_to_errno(IoErr());
-							goto out;
-						}
 
+						/* Now try to make that file larger. */
 						if(__grow_file_size(fd,new_position - fib->fib_Size) < 0)
 						{
 							fam->fam_Error = __translate_io_error_to_errno(IoErr());

library/stdio_grow_file.c

@@ -1,5 +1,5 @@
 /*
- * $Id: stdio_grow_file.c,v 1.1 2005-02-18 18:53:16 obarthel Exp $
+ * $Id: stdio_grow_file.c,v 1.2 2005-03-14 10:03:06 obarthel Exp $
  *
  * :ts=4
  *
@@ -41,7 +41,8 @@
 
 /****************************************************************************/
 
-/* Seek to the end of a file, then add a certain number of 0 bytes. */
+/* Seek to the end of a file, then add a certain number of 0 bytes. Note that
+   this function will change the current file position! */
 int
 __grow_file_size(struct fd * fd,int num_bytes)
 {
@@ -104,7 +105,7 @@ __grow_file_size(struct fd * fd,int num_bytes)
 	position = Seek(fd->fd_DefaultFile,0,OFFSET_END);
 	PROFILE_ON();
 
-	if(position == -1)
+	if(position < 0)
 	{
 		SHOWMSG("could not move to the end of the file");
 		goto out;

library/unistd_ftruncate.c

@@ -1,5 +1,5 @@
 /*
- * $Id: unistd_ftruncate.c,v 1.7 2005-03-07 11:16:43 obarthel Exp $
+ * $Id: unistd_ftruncate.c,v 1.8 2005-03-14 10:03:06 obarthel Exp $
  *
  * :ts=4
  *
@@ -47,7 +47,9 @@ ftruncate(int file_descriptor, off_t length)
 	D_S(struct FileInfoBlock,fib);
 	int result = -1;
 	struct fd * fd = NULL;
-	long int position;
+	BOOL restore_initial_position = FALSE;
+	off_t current_file_size;
+	off_t initial_position = -1;
 	BOOL success;
 
 	ENTER();
@@ -62,6 +64,8 @@ ftruncate(int file_descriptor, off_t length)
 	if(__check_abort_enabled)
 		__check_abort();
 
+	PROFILE_OFF();
+
 	fd = __get_file_descriptor(file_descriptor);
 	if(fd == NULL)
 	{
@@ -101,11 +105,7 @@ ftruncate(int file_descriptor, off_t length)
 		goto out;
 	}
 
-	/* Remember where we started. */
-	position = lseek(file_descriptor,0,SEEK_CUR);
-	if(position < 0)
-		goto out;
-
+	/* Figure out how large the file is right now. */
 	if(CANNOT __safe_examine_file_handle(fd->fd_DefaultFile,fib))
 	{
 		SHOWMSG("couldn't examine file");
@@ -114,47 +114,93 @@ ftruncate(int file_descriptor, off_t length)
 		goto out;
 	}
 
-	PROFILE_OFF();
+	current_file_size = fib->fib_Size;
 
-	if(length < fib->fib_Size)
+	/* Is the file to be made shorter than it is right now? */
+	if(length < current_file_size)
 	{
+		/* Remember where we started. */
+		if(initial_position < 0)
+		{
+			initial_position = Seek(fd->fd_DefaultFile,0,OFFSET_CURRENT);
+			if(initial_position < 0)
+				goto out;
+		}
+
 		/* Careful: seek to a position where the file can be safely truncated. */
-		success = (Seek(fd->fd_DefaultFile,length,OFFSET_BEGINNING) != -1 && SetFileSize(fd->fd_DefaultFile,length,OFFSET_BEGINNING) != -1);
-	}
-	else if (length > fib->fib_Size)
+		if(Seek(fd->fd_DefaultFile,length,OFFSET_BEGINNING) < 0)
 		{
-		success = (Seek(fd->fd_DefaultFile,fib->fib_Size,OFFSET_BEGINNING) != -1 && __grow_file_size(fd,length - fib->fib_Size) == OK);
-	}
-	else
-	{
-		success = TRUE;
-	}
+			D(("could not move to file offset %ld",length));
 
-	PROFILE_ON();
-
-	if(NO success)
-	{
-		int error;
-
-		error = __translate_io_error_to_errno(IoErr());
-
-		/* Return to the original file position. */
-		lseek(file_descriptor,position,SEEK_SET);
-
-		__set_errno(error);
+			__set_errno(__translate_io_error_to_errno(IoErr()));
 			goto out;
 		}
 
-	/* Return to the original file position. */
-	if(lseek(file_descriptor,position,SEEK_SET) < 0)
+		if(SetFileSize(fd->fd_DefaultFile,length,OFFSET_BEGINNING) < 0)
+		{
+			D(("could not reduce file to size %ld",length));
+
+			__set_errno(__translate_io_error_to_errno(IoErr()));
 			goto out;
+		}
+
+		/* If the file is now shorter than the file position, which must
+		   not be changed by a call to ftruncate(), extend the file again,
+		   filling the extension with 0 bytes. */
+		if(initial_position > length)
+		{
+			current_file_size = length;
+
+			length = initial_position;
+		}
+
+		restore_initial_position = TRUE;
+	}
+
+	/* Is the size of the file to grow? */
+	if(length > current_file_size)
+	{
+		/* Remember where we started. */
+		if(initial_position < 0)
+		{
+			initial_position = Seek(fd->fd_DefaultFile,0,OFFSET_CURRENT);
+			if(initial_position < 0)
+				goto out;
+		}
+
+		/* Move to what should be the end of the file. */
+		if(Seek(fd->fd_DefaultFile,current_file_size,OFFSET_BEGINNING) < 0)
+		{
+			D(("could not move to file offset %ld",current_file_size));
+
+			__set_errno(__translate_io_error_to_errno(IoErr()));
+			goto out;
+		}
+
+		/* Add as many bytes to the end of the file as are required
+		   to make it as large as requested. */
+		if(__grow_file_size(fd,length - current_file_size) != OK)
+		{
+			D(("could not extend file to size %ld",length));
+
+			__set_errno(__translate_io_error_to_errno(IoErr()));
+			goto out;
+		}
+
+		restore_initial_position = TRUE;
+	}
 
 	result = 0;
 
  out:
 
+	if(restore_initial_position)
+		Seek(fd->fd_DefaultFile,initial_position,OFFSET_CURRENT);
+
 	__fd_unlock(fd);
 
+	PROFILE_ON();
+
 	RETURN(result);
 	return(result);
 }