Fix MSVC warnings about possible value truncation.

src/kern.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "kern.h"
 
 // kern - Kerning
 // http://www.microsoft.com/opentype/otspec/kern.htm
 
 #define DROP_THIS_TABLE \
@@ skipping 93 matching lines @@
       ++max_pow2;
     }
     const uint16_t expected_search_range = (1u << max_pow2) * kFormat0PairSize;
     if (subtable.search_range != expected_search_range) {
       OTS_WARNING("bad search range");
       subtable.search_range = expected_search_range;
     }
     if (subtable.entry_selector != max_pow2) {
       return OTS_FAILURE();
     }
-    const uint32_t expected_range_shift
-        = kFormat0PairSize * num_pairs - subtable.search_range;
+    const uint16_t expected_range_shift =
+        kFormat0PairSize * num_pairs - subtable.search_range;
     if (subtable.range_shift != expected_range_shift) {
       OTS_WARNING("bad range shift");
       subtable.range_shift = expected_range_shift;
     }
 
     // Read kerning pairs.
     subtable.pairs.reserve(num_pairs);
     uint32_t last_pair = 0;
     for (unsigned j = 0; j < num_pairs; ++j) {
       OpenTypeKERNFormat0Pair kerning_pair;
@@ skipping 28 matching lines @@
 }
 
 bool ots_kern_should_serialise(OpenTypeFile *file) {
   if (!file->glyf) return false;  // this table is not for CFF fonts.
   return file->kern != NULL;
 }
 
 bool ots_kern_serialise(OTSStream *out, OpenTypeFile *file) {
   const OpenTypeKERN *kern = file->kern;
 
-  if (!out->WriteU16(kern->version) ||
-      !out->WriteU16(kern->subtables.size())) {
+  const uint16_t num_subtables = static_cast<uint16_t>(kern->subtables.size());
+  if (num_subtables != kern->subtables.size() ||
+      !out->WriteU16(kern->version) ||
+      !out->WriteU16(num_subtables)) {
     return OTS_FAILURE();
   }
 
-  for (unsigned i = 0; i < kern->subtables.size(); ++i) {
-    const uint16_t length = 14 + (6 * kern->subtables[i].pairs.size());
-    if (!out->WriteU16(kern->subtables[i].version) ||
-        !out->WriteU16(length) ||
+  for (uint16_t i = 0; i < num_subtables; ++i) {
+    const size_t length = 14 + (6 * kern->subtables[i].pairs.size());
+    if (length > std::numeric_limits<uint16_t>::max() ||
+        !out->WriteU16(kern->subtables[i].version) ||
+        !out->WriteU16(static_cast<uint16_t>(length)) ||
         !out->WriteU16(kern->subtables[i].coverage) ||
-        !out->WriteU16(kern->subtables[i].pairs.size()) ||
+        !out->WriteU16(
+            static_cast<uint16_t>(kern->subtables[i].pairs.size())) ||
         !out->WriteU16(kern->subtables[i].search_range) ||
         !out->WriteU16(kern->subtables[i].entry_selector) ||
         !out->WriteU16(kern->subtables[i].range_shift)) {
       return OTS_FAILURE();
     }
     for (unsigned j = 0; j < kern->subtables[i].pairs.size(); ++j) {
       if (!out->WriteU16(kern->subtables[i].pairs[j].left) ||
           !out->WriteU16(kern->subtables[i].pairs[j].right) ||
           !out->WriteS16(kern->subtables[i].pairs[j].value)) {
         return OTS_FAILURE();
       }
     }
   }
 
   return true;
 }
 
 void ots_kern_free(OpenTypeFile *file) {
   delete file->kern;
 }
 
 }  // namespace ots