129 lines
3.1 KiB
C++
129 lines
3.1 KiB
C++
/* Copyright 2015 Google Inc. All Rights Reserved.
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Distributed under MIT license.
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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/* Helper functions for woff2 variable length types: 255UInt16 and UIntBase128 */
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#include "./variable_length.h"
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namespace woff2 {
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size_t Size255UShort(uint16_t value) {
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size_t result = 3;
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if (value < 253) {
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result = 1;
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} else if (value < 762) {
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result = 2;
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} else {
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result = 3;
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}
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return result;
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}
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void Write255UShort(std::vector<uint8_t>* out, int value) {
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if (value < 253) {
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out->push_back(value);
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} else if (value < 506) {
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out->push_back(255);
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out->push_back(value - 253);
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} else if (value < 762) {
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out->push_back(254);
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out->push_back(value - 506);
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} else {
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out->push_back(253);
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out->push_back(value >> 8);
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out->push_back(value & 0xff);
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}
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}
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void Store255UShort(int val, size_t* offset, uint8_t* dst) {
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std::vector<uint8_t> packed;
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Write255UShort(&packed, val);
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for (uint8_t packed_byte : packed) {
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dst[(*offset)++] = packed_byte;
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}
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}
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// Based on section 6.1.1 of MicroType Express draft spec
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bool Read255UShort(Buffer* buf, unsigned int* value) {
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static const int kWordCode = 253;
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static const int kOneMoreByteCode2 = 254;
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static const int kOneMoreByteCode1 = 255;
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static const int kLowestUCode = 253;
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uint8_t code = 0;
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if (!buf->ReadU8(&code)) {
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return FONT_COMPRESSION_FAILURE();
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}
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if (code == kWordCode) {
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uint16_t result = 0;
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if (!buf->ReadU16(&result)) {
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return FONT_COMPRESSION_FAILURE();
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}
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*value = result;
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return true;
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} else if (code == kOneMoreByteCode1) {
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uint8_t result = 0;
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if (!buf->ReadU8(&result)) {
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return FONT_COMPRESSION_FAILURE();
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}
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*value = result + kLowestUCode;
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return true;
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} else if (code == kOneMoreByteCode2) {
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uint8_t result = 0;
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if (!buf->ReadU8(&result)) {
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return FONT_COMPRESSION_FAILURE();
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}
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*value = result + kLowestUCode * 2;
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return true;
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} else {
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*value = code;
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return true;
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}
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}
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bool ReadBase128(Buffer* buf, uint32_t* value) {
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uint32_t result = 0;
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for (size_t i = 0; i < 5; ++i) {
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uint8_t code = 0;
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if (!buf->ReadU8(&code)) {
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return FONT_COMPRESSION_FAILURE();
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}
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// Leading zeros are invalid.
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if (i == 0 && code == 0x80) {
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return FONT_COMPRESSION_FAILURE();
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}
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// If any of the top seven bits are set then we're about to overflow.
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if (result & 0xfe000000) {
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return FONT_COMPRESSION_FAILURE();
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}
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result = (result << 7) | (code & 0x7f);
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if ((code & 0x80) == 0) {
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*value = result;
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return true;
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}
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}
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// Make sure not to exceed the size bound
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return FONT_COMPRESSION_FAILURE();
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}
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size_t Base128Size(size_t n) {
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size_t size = 1;
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for (; n >= 128; n >>= 7) ++size;
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return size;
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}
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void StoreBase128(size_t len, size_t* offset, uint8_t* dst) {
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size_t size = Base128Size(len);
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for (size_t i = 0; i < size; ++i) {
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int b = static_cast<int>((len >> (7 * (size - i - 1))) & 0x7f);
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if (i < size - 1) {
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b |= 0x80;
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}
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dst[(*offset)++] = b;
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}
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}
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} // namespace woff2
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