--- diff-delta.c.orig	2006-04-22 06:53:44.000000000 -0400
+++ diff-delta.c	2006-04-22 06:59:14.000000000 -0400
@@ -29,7 +29,7 @@
 #define RABIN_WINDOW_SIZE 22
 #define RABIN_SHIFT 55
 
-static unsigned long long T[256] =
+static const unsigned long long T[256] =
 { 0x0000000000000000ULL, 0xb15e234bd3792f63ULL, 0x62bc4697a6f25ec6ULL,
   0xd3e265dc758b71a5ULL, 0x7426ae649e9d92efULL, 0xc5788d2f4de4bd8cULL,
   0x169ae8f3386fcc29ULL, 0xa7c4cbb8eb16e34aULL, 0x59137f82ee420abdULL,
@@ -118,7 +118,7 @@
   0xed7b43a0554e9f70ULL
 };
 
-static unsigned long long U[256] =
+static const unsigned long long U[256] =
 { 0x0000000000000000ULL, 0x079343d61ab9f60eULL, 0x0f2687ac3573ec1cULL,
   0x08b5c47a2fca1a12ULL, 0x1e4d0f586ae7d838ULL, 0x19de4c8e705e2e36ULL,
   0x116b88f45f943424ULL, 0x16f8cb22452dc22aULL, 0x3c9a1eb0d5cfb070ULL,
@@ -261,7 +261,7 @@
 static int	copy_count = 0;
 static unsigned max_copies = 0; /* Dynamically increased */
 
-static unsigned *idx;
+static unsigned *idx = 0;
 static unsigned idx_size;
 static unsigned char *idx_data;
 static unsigned idx_data_len;
@@ -406,6 +406,19 @@
     { idx[maxfp[j] % idx_size] = maxofs[j];
 } } }
 
+static void finalize_idx()
+{ if (max_copies > MAX_COPIES)
+  { free (copies);
+    max_copies = 0;
+    copy_count = 0;
+  }
+  if (idx) free (idx);
+  idx = 0;
+  idx_size = 0;
+  idx_data = 0;
+  idx_data_len = 0;
+}
+
 static unsigned header_length (unsigned srclen, unsigned tgtlen)
 { unsigned len = 0;
   assert (srclen <= MAX_SIZE && tgtlen <= MAX_SIZE);
@@ -420,10 +433,12 @@
 }
 
 static unsigned data_length (unsigned length)
-{ assert (length > 0 && length <= MAX_SIZE);
+{ unsigned len = length % 0x7f;
+  assert (length > 0 && length <= MAX_SIZE);
 
   /* Can only include 0x7f data bytes per command */
-  return (length / 0x7f) * 0x80 + length % 0x7f + 1;
+  if (len) len++;
+  return len + (length / 0x7f) * 0x80;
 }
 
 static unsigned copy_length (unsigned offset, unsigned length)
@@ -624,8 +639,7 @@
 
 static unsigned char *
 write_header (unsigned char *patch, unsigned srclen, unsigned tgtlen)
-{ 
-  assert (srclen <= MAX_SIZE && tgtlen <= MAX_SIZE);
+{ assert (srclen <= MAX_SIZE && tgtlen <= MAX_SIZE);
 
   while (srclen >= 0x7f) 
   { *patch++= (srclen & 0x7f) | 0x80;
@@ -658,8 +672,9 @@
 
   *patch++ = (unsigned char) size; 
   memcpy (patch, data, size);
+  patch += size;
 
-  return patch + size;
+  return patch;
 } 
 
 static unsigned char *
@@ -687,6 +702,7 @@
     if (cmd & 0x40) *patch++ = (size >> 16) & 0xff;
     size -= chunksize;
   } 
+
   return patch;
 } 
 
@@ -699,7 +715,9 @@
   unsigned copy_commands = 0;
   int j;
 
+  assert (delta_size - (ptr - delta) >= header_length (idx_data_len, len));
   ptr = write_header (ptr, idx_data_len, len);
+  assert (ptr - delta > 0);
 
   for (j = 0; j < copy_count; j++)
   { CopyInfo *copy = copies + j;
@@ -732,11 +750,17 @@
 void *diff_delta(void *from_buf, unsigned long from_size,
                  void *to_buf, unsigned long to_size,
                  unsigned long *delta_size, unsigned long max_size)
-{ unsigned dsize;
+{ unsigned char *delta = 0;
+  unsigned dsize;
   assert (from_size <= MAX_SIZE && to_size <= MAX_SIZE);
   init_idx (from_buf, from_size, 1); /* Use optimization level 1 */
+
   dsize = calculate_delta (to_buf, to_size);
-  if (!dsize) return 0;
-  *delta_size = dsize;
-  return create_delta (to_buf, to_size, *delta_size);
+  if (dsize && (!max_size || dsize <= max_size))
+  { delta = create_delta (to_buf, to_size, dsize);
+    *delta_size = delta ? dsize : 0;
+  }
+
+  finalize_idx ();
+  return delta;
 }