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- /* Copyright 2015 Google Inc. All Rights Reserved.
- Distributed under MIT license.
- See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
- */
- /* 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 packed_byte : packed) {
- dst[(*offset)++] = packed_byte;
- }
- }
- // 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
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