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OpenRCT2/src/openrct2/util/SawyerCoding.cpp

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/*****************************************************************************
* Copyright (c) 2014-2020 OpenRCT2 developers
*
* For a complete list of all authors, please refer to contributors.md
* Interested in contributing? Visit https://github.com/OpenRCT2/OpenRCT2
*
* OpenRCT2 is licensed under the GNU General Public License version 3.
*****************************************************************************/
#include "SawyerCoding.h"
#include "../core/Numerics.hpp"
#include "../platform/platform.h"
#include "../scenario/Scenario.h"
#include "Util.h"
#include <algorithm>
#include <cstring>
static size_t decode_chunk_rle(const uint8_t* src_buffer, uint8_t* dst_buffer, size_t length);
static size_t decode_chunk_rle_with_size(const uint8_t* src_buffer, uint8_t* dst_buffer, size_t length, size_t dstSize);
static size_t encode_chunk_rle(const uint8_t* src_buffer, uint8_t* dst_buffer, size_t length);
static size_t encode_chunk_repeat(const uint8_t* src_buffer, uint8_t* dst_buffer, size_t length);
static void encode_chunk_rotate(uint8_t* buffer, size_t length);
bool gUseRLE = true;
uint32_t sawyercoding_calculate_checksum(const uint8_t* buffer, size_t length)
{
uint32_t checksum = 0;
for (size_t i = 0; i < length; i++)
checksum += buffer[i];
return checksum;
}
/**
*
* rct2: 0x006762E1
*
*/
size_t sawyercoding_write_chunk_buffer(uint8_t* dst_file, const uint8_t* buffer, sawyercoding_chunk_header chunkHeader)
{
uint8_t *encode_buffer, *encode_buffer2;
if (!gUseRLE)
{
if (chunkHeader.encoding == CHUNK_ENCODING_RLE || chunkHeader.encoding == CHUNK_ENCODING_RLECOMPRESSED)
{
chunkHeader.encoding = CHUNK_ENCODING_NONE;
}
}
switch (chunkHeader.encoding)
{
case CHUNK_ENCODING_NONE:
std::memcpy(dst_file, &chunkHeader, sizeof(sawyercoding_chunk_header));
dst_file += sizeof(sawyercoding_chunk_header);
std::memcpy(dst_file, buffer, chunkHeader.length);
// fwrite(&chunkHeader, sizeof(sawyercoding_chunk_header), 1, file);
// fwrite(buffer, 1, chunkHeader.length, file);
break;
case CHUNK_ENCODING_RLE:
encode_buffer = static_cast<uint8_t*>(malloc(0x600000));
chunkHeader.length = static_cast<uint32_t>(encode_chunk_rle(buffer, encode_buffer, chunkHeader.length));
std::memcpy(dst_file, &chunkHeader, sizeof(sawyercoding_chunk_header));
dst_file += sizeof(sawyercoding_chunk_header);
std::memcpy(dst_file, encode_buffer, chunkHeader.length);
free(encode_buffer);
break;
case CHUNK_ENCODING_RLECOMPRESSED:
encode_buffer = static_cast<uint8_t*>(malloc(chunkHeader.length * 2));
encode_buffer2 = static_cast<uint8_t*>(malloc(0x600000));
chunkHeader.length = static_cast<uint32_t>(encode_chunk_repeat(buffer, encode_buffer, chunkHeader.length));
chunkHeader.length = static_cast<uint32_t>(encode_chunk_rle(encode_buffer, encode_buffer2, chunkHeader.length));
std::memcpy(dst_file, &chunkHeader, sizeof(sawyercoding_chunk_header));
dst_file += sizeof(sawyercoding_chunk_header);
std::memcpy(dst_file, encode_buffer2, chunkHeader.length);
free(encode_buffer2);
free(encode_buffer);
break;
case CHUNK_ENCODING_ROTATE:
encode_buffer = static_cast<uint8_t*>(malloc(chunkHeader.length));
std::memcpy(encode_buffer, buffer, chunkHeader.length);
encode_chunk_rotate(encode_buffer, chunkHeader.length);
std::memcpy(dst_file, &chunkHeader, sizeof(sawyercoding_chunk_header));
dst_file += sizeof(sawyercoding_chunk_header);
std::memcpy(dst_file, encode_buffer, chunkHeader.length);
free(encode_buffer);
break;
}
return chunkHeader.length + sizeof(sawyercoding_chunk_header);
}
size_t sawyercoding_decode_sv4(const uint8_t* src, uint8_t* dst, size_t length, size_t bufferLength)
{
// (0 to length - 4): RLE chunk
// (length - 4 to length): checksum
return decode_chunk_rle_with_size(src, dst, length - 4, bufferLength);
}
size_t sawyercoding_decode_sc4(const uint8_t* src, uint8_t* dst, size_t length, size_t bufferLength)
{
// Uncompress
size_t decodedLength = decode_chunk_rle_with_size(src, dst, length - 4, bufferLength);
// Decode
for (size_t i = 0x60018; i <= std::min(decodedLength - 1, static_cast<size_t>(0x1F8353)); i++)
dst[i] = dst[i] ^ 0x9C;
for (size_t i = 0x60018; i <= std::min(decodedLength - 1, static_cast<size_t>(0x1F8350)); i += 4)
{
dst[i + 1] = Numerics::ror8(dst[i + 1], 3);
uint32_t* code = reinterpret_cast<uint32_t*>(&dst[i]);
*code = Numerics::rol32(*code, 9);
}
return decodedLength;
}
size_t sawyercoding_encode_sv4(const uint8_t* src, uint8_t* dst, size_t length)
{
// Encode
size_t encodedLength = encode_chunk_rle(src, dst, length);
// Append checksum
uint32_t checksum = sawyercoding_calculate_checksum(dst, encodedLength);
*(reinterpret_cast<uint32_t*>(&dst[encodedLength])) = checksum;
return encodedLength + 4;
}
size_t sawyercoding_decode_td6(const uint8_t* src, uint8_t* dst, size_t length)
{
return decode_chunk_rle(src, dst, length - 4);
}
size_t sawyercoding_encode_td6(const uint8_t* src, uint8_t* dst, size_t length)
{
size_t output_length = encode_chunk_rle(src, dst, length);
uint32_t checksum = 0;
for (size_t i = 0; i < output_length; i++)
{
uint8_t new_byte = ((checksum & 0xFF) + dst[i]) & 0xFF;
checksum = (checksum & 0xFFFFFF00) + new_byte;
checksum = Numerics::rol32(checksum, 3);
}
checksum -= 0x1D4C1;
*(reinterpret_cast<uint32_t*>(&dst[output_length])) = checksum;
output_length += 4;
return output_length;
}
/* Based off of rct2: 0x006770C1 */
int32_t sawyercoding_validate_track_checksum(const uint8_t* src, size_t length)
{
uint32_t file_checksum = *(reinterpret_cast<const uint32_t*>(&src[length - 4]));
uint32_t checksum = 0;
for (size_t i = 0; i < length - 4; i++)
{
uint8_t new_byte = ((checksum & 0xFF) + src[i]) & 0xFF;
checksum = (checksum & 0xFFFFFF00) + new_byte;
checksum = Numerics::rol32(checksum, 3);
}
if (checksum - 0x1D4C1 == file_checksum)
return 1; // .TD6
else if (checksum - 0x1A67C == file_checksum)
return 1; // .TD4
else if (checksum - 0x1A650 == file_checksum)
return 1; // .TD4
else
return 0;
}
#pragma region Decoding
/**
*
* rct2: 0x0067693A
*/
static size_t decode_chunk_rle(const uint8_t* src_buffer, uint8_t* dst_buffer, size_t length)
{
size_t count;
uint8_t *dst, rleCodeByte;
dst = dst_buffer;
for (size_t i = 0; i < length; i++)
{
rleCodeByte = src_buffer[i];
if (rleCodeByte & 128)
{
i++;
count = 257 - rleCodeByte;
std::fill_n(dst, count, src_buffer[i]);
dst = reinterpret_cast<uint8_t*>(reinterpret_cast<uintptr_t>(dst) + count);
}
else
{
std::memcpy(dst, src_buffer + i + 1, rleCodeByte + 1);
dst = reinterpret_cast<uint8_t*>(reinterpret_cast<uintptr_t>(dst) + rleCodeByte + 1);
i += rleCodeByte + 1;
}
}
// Return final size
return dst - dst_buffer;
}
/**
*
* rct2: 0x0067693A
*/
static size_t decode_chunk_rle_with_size(const uint8_t* src_buffer, uint8_t* dst_buffer, size_t length, size_t dstSize)
{
size_t count;
uint8_t *dst, rleCodeByte;
dst = dst_buffer;
assert(length > 0);
assert(dstSize > 0);
for (size_t i = 0; i < length; i++)
{
rleCodeByte = src_buffer[i];
if (rleCodeByte & 128)
{
i++;
count = 257 - rleCodeByte;
assert(dst + count <= dst_buffer + dstSize);
assert(i < length);
std::fill_n(dst, count, src_buffer[i]);
dst = reinterpret_cast<uint8_t*>(reinterpret_cast<uintptr_t>(dst) + count);
}
else
{
assert(dst + rleCodeByte + 1 <= dst_buffer + dstSize);
assert(i + 1 < length);
std::memcpy(dst, src_buffer + i + 1, rleCodeByte + 1);
dst = reinterpret_cast<uint8_t*>(reinterpret_cast<uintptr_t>(dst) + rleCodeByte + 1);
i += rleCodeByte + 1;
}
}
// Return final size
return dst - dst_buffer;
}
#pragma endregion
#pragma region Encoding
/**
* Ensure dst_buffer is bigger than src_buffer then resize afterwards
* returns length of dst_buffer
*/
static size_t encode_chunk_rle(const uint8_t* src_buffer, uint8_t* dst_buffer, size_t length)
{
const uint8_t* src = src_buffer;
uint8_t* dst = dst_buffer;
const uint8_t* end_src = src + length;
uint8_t count = 0;
const uint8_t* src_norm_start = src;
while (src < end_src - 1)
{
if ((count && *src == src[1]) || count > 125)
{
*dst++ = count - 1;
std::memcpy(dst, src_norm_start, count);
dst += count;
src_norm_start += count;
count = 0;
}
if (*src == src[1])
{
for (; (count < 125) && ((src + count) < end_src); count++)
{
if (*src != src[count])
break;
}
*dst++ = 257 - count;
*dst++ = *src;
src += count;
src_norm_start = src;
count = 0;
}
else
{
count++;
src++;
}
}
if (src == end_src - 1)
count++;
if (count)
{
*dst++ = count - 1;
std::memcpy(dst, src_norm_start, count);
dst += count;
}
return dst - dst_buffer;
}
static size_t encode_chunk_repeat(const uint8_t* src_buffer, uint8_t* dst_buffer, size_t length)
{
if (length == 0)
return 0;
size_t outLength = 0;
// Need to emit at least one byte, otherwise there is nothing to repeat
*dst_buffer++ = 255;
*dst_buffer++ = src_buffer[0];
outLength += 2;
// Iterate through remainder of the source buffer
for (size_t i = 1; i < length;)
{
size_t searchIndex = (i < 32) ? 0 : (i - 32);
size_t searchEnd = i - 1;
size_t bestRepeatIndex = 0;
size_t bestRepeatCount = 0;
for (size_t repeatIndex = searchIndex; repeatIndex <= searchEnd; repeatIndex++)
{
size_t repeatCount = 0;
size_t maxRepeatCount = std::min(std::min(static_cast<size_t>(7), searchEnd - repeatIndex), length - i - 1);
// maxRepeatCount should not exceed length
assert(repeatIndex + maxRepeatCount < length);
assert(i + maxRepeatCount < length);
for (size_t j = 0; j <= maxRepeatCount; j++)
{
if (src_buffer[repeatIndex + j] == src_buffer[i + j])
{
repeatCount++;
}
else
{
break;
}
}
if (repeatCount > bestRepeatCount)
{
bestRepeatIndex = repeatIndex;
bestRepeatCount = repeatCount;
// Maximum repeat count is 8
if (repeatCount == 8)
break;
}
}
if (bestRepeatCount == 0)
{
*dst_buffer++ = 255;
*dst_buffer++ = src_buffer[i];
outLength += 2;
i++;
}
else
{
*dst_buffer++ = static_cast<uint8_t>((bestRepeatCount - 1) | ((32 - (i - bestRepeatIndex)) << 3));
outLength++;
i += bestRepeatCount;
}
}
return outLength;
}
static void encode_chunk_rotate(uint8_t* buffer, size_t length)
{
size_t i;
uint8_t code = 1;
for (i = 0; i < length; i++)
{
buffer[i] = Numerics::rol8(buffer[i], code);
code = (code + 2) % 8;
}
}
#pragma endregion
int32_t sawyercoding_detect_file_type(const uint8_t* src, size_t length)
{
size_t i;
// Currently can't detect TD4, as the checksum is the same as SC4 (need alternative method)
uint32_t checksum = *(reinterpret_cast<const uint32_t*>(&src[length - 4]));
uint32_t actualChecksum = 0;
for (i = 0; i < length - 4; i++)
{
actualChecksum = (actualChecksum & 0xFFFFFF00) | (((actualChecksum & 0xFF) + static_cast<uint8_t>(src[i])) & 0xFF);
actualChecksum = Numerics::rol32(actualChecksum, 3);
}
return sawyercoding_detect_rct1_version(checksum - actualChecksum);
}
int32_t sawyercoding_detect_rct1_version(int32_t gameVersion)
{
int32_t fileType = (gameVersion) > 0 ? FILE_TYPE_SV4 : FILE_TYPE_SC4;
gameVersion = abs(gameVersion);
if (gameVersion >= 108000 && gameVersion < 110000)
return (FILE_VERSION_RCT1 | fileType);
if (gameVersion >= 110000 && gameVersion < 120000)
return (FILE_VERSION_RCT1_AA | fileType);
if (gameVersion >= 120000 && gameVersion < 130000)
return (FILE_VERSION_RCT1_LL | fileType);
// RCTOA Acres sets this, and possibly some other user-created scenarios as well
if (gameVersion == 0)
return (FILE_VERSION_RCT1_LL | fileType);
return -1;
}
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