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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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