rework scale code for ubsan

source/scale.cc

 /*
  *  Copyright 2011 The LibYuv Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS. All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 641 matching lines @@
     sum += src_ptr[x];
   }
   return sum;
 }
 
 static void ScaleAddCols2_C(int dst_width, int boxheight, int x, int dx,
                             const uint16* src_ptr, uint8* dst_ptr) {
   int i;
   int scaletbl[2];
   int minboxwidth = dx >> 16;
-  int* scaleptr = scaletbl - minboxwidth;
   int boxwidth;
   scaletbl[0] = 65536 / (MIN1(minboxwidth) * boxheight);
   scaletbl[1] = 65536 / (MIN1(minboxwidth + 1) * boxheight);
   for (i = 0; i < dst_width; ++i) {
     int ix = x >> 16;
     x += dx;
     boxwidth = MIN1((x >> 16) - ix);
-    *dst_ptr++ = SumPixels(boxwidth, src_ptr + ix) * scaleptr[boxwidth] >> 16;
+    *dst_ptr++ = SumPixels(boxwidth, src_ptr + ix) *
+        scaletbl[boxwidth - minboxwidth] >> 16;
   }
 }
 
 static void ScaleAddCols2_16_C(int dst_width, int boxheight, int x, int dx,
                                const uint32* src_ptr, uint16* dst_ptr) {
   int i;
   int scaletbl[2];
   int minboxwidth = dx >> 16;
-  int* scaleptr = scaletbl - minboxwidth;
   int boxwidth;
   scaletbl[0] = 65536 / (MIN1(minboxwidth) * boxheight);
   scaletbl[1] = 65536 / (MIN1(minboxwidth + 1) * boxheight);
   for (i = 0; i < dst_width; ++i) {
     int ix = x >> 16;
     x += dx;
     boxwidth = MIN1((x >> 16) - ix);
-    *dst_ptr++ =
-        SumPixels_16(boxwidth, src_ptr + ix) * scaleptr[boxwidth] >> 16;
+    *dst_ptr++ = SumPixels_16(boxwidth, src_ptr + ix) *
+        scaletbl[boxwidth - minboxwidth]  >> 16;
   }
 }
 
 static void ScaleAddCols0_C(int dst_width, int boxheight, int x, int,
                             const uint16* src_ptr, uint8* dst_ptr) {
   int scaleval = 65536 / boxheight;
   int i;
   src_ptr += (x >> 16);
   for (i = 0; i < dst_width; ++i) {
     *dst_ptr++ = src_ptr[i] * scaleval >> 16;
@@ skipping 965 matching lines @@
                    dst_u, dst_halfwidth,
                    dst_v, dst_halfwidth,
                    dst_width, aheight,
                    interpolate ? kFilterBox : kFilterNone);
 }
 
 #ifdef __cplusplus
 }  // extern "C"
 }  // namespace libyuv
 #endif