[Linux-NTFS-cvs] CVS: ntfsprogs/libntfs compress.c,1.18,1.19

[Yuval <uv...@de...>]

Changes by: uvman

Update of /cvs/linux-ntfs/ntfsprogs/libntfs
In directory delta357:/tmp/cvs-serv4713/libntfs

Modified Files:
	compress.c 
Log Message:
I was assuming memmove() would copy byte by byte if it detects a smaller than word gap. Anton pointed out that it doesn't, glibc sources confirm, the C99 standard claims otherwise. Revert the compress.c patch as implementation is more important than specification.

Index: compress.c
===================================================================
RCS file: /cvs/linux-ntfs/ntfsprogs/libntfs/compress.c,v
retrieving revision 1.18
retrieving revision 1.19
diff -u -p -r1.18 -r1.19
--- compress.c	28 Oct 2006 23:35:56 -0000	1.18
+++ compress.c	29 Oct 2006 08:59:21 -0000	1.19
@@ -166,7 +166,7 @@ do_next_tag:
 	tag = *cb++;
 	/* Parse the eight tokens described by the tag. */
 	for (token = 0; token < 8; token++, tag >>= 1) {
-		u16 lg, pt, length;
+		u16 lg, pt, length, max_non_overlap;
 		register u16 i;
 		u8 *dest_back_addr;
 
@@ -214,9 +214,27 @@ do_next_tag:
 		/* Verify destination is in range. */
 		if (dest + length > dest_sb_end)
 			goto return_overflow;
-		/* memmove() is safe with overlapping blocks. */
-		memmove(dest, dest_back_addr, length);
-		dest += length;
+		/* The number of non-overlapping bytes. */
+		max_non_overlap = dest - dest_back_addr;
+		if (length <= max_non_overlap) {
+			/* The byte sequence doesn't overlap, just copy it. */
+			memcpy(dest, dest_back_addr, length);
+			/* Advance destination pointer. */
+			dest += length;
+		} else {
+			/*
+			 * The byte sequence does overlap, copy non-overlapping
+			 * part and then do a slow byte by byte copy for the
+			 * overlapping part. Also, advance the destination
+			 * pointer.
+			 */
+			memcpy(dest, dest_back_addr, max_non_overlap);
+			dest += max_non_overlap;
+			dest_back_addr += max_non_overlap;
+			length -= max_non_overlap;
+			while (length--)
+				*dest++ = *dest_back_addr++;
+		}
 		/* Advance source position and continue with the next token. */
 		cb += 2;
 	}