1 files changed, 137 insertions, 0 deletions
diff --git a/modules/woff2/src/variable_length.cc b/modules/woff2/src/variable_length.cc
new file mode 100644
index 000000000..944a17f2e
--- /dev/null
+++ b/modules/woff2/src/variable_length.cc
@@ -0,0 +1,137 @@
+// Copyright 2015 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.
+//
+// Helper functions for woff2 variable length types: 255UInt16 and UIntBase128
+
+#include "./variable_length.h"
+
+namespace woff2 {
+
+size_t Size255UShort(uint16_t value) {
+  size_t result = 3;
+  if (value < 253) {
+    result = 1;
+  } else if (value < 762) {
+    result = 2;
+  } else {
+    result = 3;
+  }
+  return result;
+}
+
+void Write255UShort(std::vector<uint8_t>* out, int value) {
+  if (value < 253) {
+    out->push_back(value);
+  } else if (value < 506) {
+    out->push_back(255);
+    out->push_back(value - 253);
+  } else if (value < 762) {
+    out->push_back(254);
+    out->push_back(value - 506);
+  } else {
+    out->push_back(253);
+    out->push_back(value >> 8);
+    out->push_back(value & 0xff);
+  }
+}
+
+void Store255UShort(int val, size_t* offset, uint8_t* dst) {
+  std::vector<uint8_t> packed;
+  Write255UShort(&packed, val);
+  for (uint8_t val : packed) {
+    dst[(*offset)++] = val;
+  }
+}
+
+// Based on section 6.1.1 of MicroType Express draft spec
+bool Read255UShort(Buffer* buf, unsigned int* value) {
+  static const int kWordCode = 253;
+  static const int kOneMoreByteCode2 = 254;
+  static const int kOneMoreByteCode1 = 255;
+  static const int kLowestUCode = 253;
+  uint8_t code = 0;
+  if (!buf->ReadU8(&code)) {
+    return FONT_COMPRESSION_FAILURE();
+  }
+  if (code == kWordCode) {
+    uint16_t result = 0;
+    if (!buf->ReadU16(&result)) {
+      return FONT_COMPRESSION_FAILURE();
+    }
+    *value = result;
+    return true;
+  } else if (code == kOneMoreByteCode1) {
+    uint8_t result = 0;
+    if (!buf->ReadU8(&result)) {
+      return FONT_COMPRESSION_FAILURE();
+    }
+    *value = result + kLowestUCode;
+    return true;
+  } else if (code == kOneMoreByteCode2) {
+    uint8_t result = 0;
+    if (!buf->ReadU8(&result)) {
+      return FONT_COMPRESSION_FAILURE();
+    }
+    *value = result + kLowestUCode * 2;
+    return true;
+  } else {
+    *value = code;
+    return true;
+  }
+}
+
+bool ReadBase128(Buffer* buf, uint32_t* value) {
+  uint32_t result = 0;
+  for (size_t i = 0; i < 5; ++i) {
+    uint8_t code = 0;
+    if (!buf->ReadU8(&code)) {
+      return FONT_COMPRESSION_FAILURE();
+    }
+    // Leading zeros are invalid.
+    if (i == 0 && code == 0x80) {
+      return FONT_COMPRESSION_FAILURE();
+    }
+    // If any of the top seven bits are set then we're about to overflow.
+    if (result & 0xfe000000) {
+      return FONT_COMPRESSION_FAILURE();
+    }
+    result = (result << 7) | (code & 0x7f);
+    if ((code & 0x80) == 0) {
+      *value = result;
+      return true;
+    }
+  }
+  // Make sure not to exceed the size bound
+  return FONT_COMPRESSION_FAILURE();
+}
+
+size_t Base128Size(size_t n) {
+  size_t size = 1;
+  for (; n >= 128; n >>= 7) ++size;
+  return size;
+}
+
+void StoreBase128(size_t len, size_t* offset, uint8_t* dst) {
+  size_t size = Base128Size(len);
+  for (size_t i = 0; i < size; ++i) {
+    int b = static_cast<int>((len >> (7 * (size - i - 1))) & 0x7f);
+    if (i < size - 1) {
+      b |= 0x80;
+    }
+    dst[(*offset)++] = b;
+  }
+}
+
+} // namespace woff2
+