Adding TTC support, take 1

src/woff2_common.cc

@@ -0,0 +1,46 @@
+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Helpers common across multiple parts of woff2
+
+#include <algorithm>
+
+#include "./woff2_common.h"
+
+namespace woff2 {
+
+
+uint32_t ComputeULongSum(const uint8_t* buf, size_t size) {
+  uint32_t checksum = 0;
+  for (size_t i = 0; i < size; i += 4) {
+    // We assume the addition is mod 2^32, which is valid because unsigned
+    checksum += (buf[i] << 24) | (buf[i + 1] << 16) |
+      (buf[i + 2] << 8) | buf[i + 3];
+  }
+  return checksum;
+}
+
+size_t CollectionHeaderSize(uint32_t header_version, uint32_t num_fonts) {
+  size_t size = 0;
+  if (header_version == 0x00020000) {
+    size += 12;  // ulDsig{Tag,Length,Offset}
+  }
+  if (header_version == 0x00010000 || header_version == 0x00020000) {
+    size += 12   // TTCTag, Version, numFonts
+      + 4 * num_fonts;  // OffsetTable[numFonts]
+  }
+  return size;
+}
+
+} // namespace woff2