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minor optimization

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This commit is contained in:
digant73 2026-04-07 21:31:02 +02:00
parent f9d496ff2f
commit 1a92a0f08e
1 changed files with 70 additions and 53 deletions
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123
rpcs3/Loader/ISO.cpp
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@ -68,10 +68,13 @@ static void reset_iv(std::array<u8, 16>& iv, u32 lba)
// Main function that will decrypt the sector(s)
static bool decrypt_data(aes_context& aes, u64 offset, unsigned char* buffer, u64 size)
{
if (size == 0)
{
return false;
}
// The following preliminary checks are good to be provided.
// Commented out to gain a bit of performance, just because we know the caller is providing values in the expected range
//if (size == 0)
//{
// return false;
//}
//if ((size % 16) != 0)
//{
@ -81,11 +84,9 @@ static bool decrypt_data(aes_context& aes, u64 offset, unsigned char* buffer, u6
u32 cur_sector_lba = static_cast<u32>(offset / ISO_SECTOR_SIZE); // First sector's LBA
const u32 sector_count = static_cast<u32>((offset + size - 1) / ISO_SECTOR_SIZE) - cur_sector_lba + 1;
const u32 sector_inner_count = sector_count > 2 ? sector_count - 2 : 0; // Remove first and last sector
const u64 sector_offset = offset % ISO_SECTOR_SIZE;
std::array<u8, 16> iv;
u64 dec_size;
u64 cur_offset;
u64 cur_size;
@ -95,12 +96,12 @@ static bool decrypt_data(aes_context& aes, u64 offset, unsigned char* buffer, u6
if (sector_offset != 0)
{
memcpy(iv.data(), buffer, 16);
dec_size = cur_offset = 16;
cur_offset = 16;
}
else
{
reset_iv(iv, cur_sector_lba);
dec_size = cur_offset = 0;
cur_offset = 0;
}
cur_size = sector_offset + size <= ISO_SECTOR_SIZE ? size : ISO_SECTOR_SIZE - sector_offset;
@ -113,11 +114,17 @@ static bool decrypt_data(aes_context& aes, u64 offset, unsigned char* buffer, u6
return false;
}
dec_size += cur_size;
if (sector_count < 2) // If no more sector(s)
{
return true;
}
cur_offset += cur_size;
const u32 inner_sector_count = sector_count > 2 ? sector_count - 2 : 0; // Remove first and last sector
// Inner sector(s), if any
for (u32 i = 0; i < sector_inner_count; i++)
for (u32 i = 0; i < inner_sector_count; i++)
{
reset_iv(iv, ++cur_sector_lba); // Next sector's IV
@ -127,20 +134,16 @@ static bool decrypt_data(aes_context& aes, u64 offset, unsigned char* buffer, u6
return false;
}
dec_size += ISO_SECTOR_SIZE;
cur_offset += ISO_SECTOR_SIZE;
}
// Partial (or even full) last sector, if any
if (dec_size < size)
{
reset_iv(iv, ++cur_sector_lba); // Next sector's IV
reset_iv(iv, ++cur_sector_lba); // Next sector's IV
if (aes_crypt_cbc(&aes, AES_DECRYPT, size - dec_size, iv.data(), &buffer[cur_offset], &buffer[cur_offset]) != 0)
{
sys_log.error("decrypt_data(): Error decrypting data on last sector read");
return false;
}
// Partial (or even full) last sector
if (aes_crypt_cbc(&aes, AES_DECRYPT, size - cur_offset, iv.data(), &buffer[cur_offset], &buffer[cur_offset]) != 0)
{
sys_log.error("decrypt_data(): Error decrypting data on last sector read");
return false;
}
return true;
@ -841,7 +844,6 @@ u64 iso_file::read_at(u64 offset, void* buffer, u64 size)
const u64 archive_last_offset = archive_first_offset + max_size - 1;
iso_sector first_sec, last_sec;
u64 offset_first_out;
u64 offset_aligned;
u64 offset_aligned_first_out;
@ -850,10 +852,13 @@ u64 iso_file::read_at(u64 offset, void* buffer, u64 size)
first_sec.size = first_sec.offset + max_size <= ISO_SECTOR_SIZE ? max_size : ISO_SECTOR_SIZE - first_sec.offset;
last_sec.lba_address = last_sec.address_aligned = (archive_last_offset / ISO_SECTOR_SIZE) * ISO_SECTOR_SIZE;
last_sec.offset = last_sec.offset_aligned = 0;
//last_sec.offset = last_sec.offset_aligned = 0; // Always 0 so no need to set and use those attributes
last_sec.size = (archive_last_offset % ISO_SECTOR_SIZE) + 1;
offset_first_out = first_sec.offset + first_sec.size;
//
// First sector
//
offset_aligned = first_sec.offset & ~0xF;
offset_aligned_first_out = (first_sec.offset + first_sec.size) & ~0xF;
@ -863,32 +868,58 @@ u64 iso_file::read_at(u64 offset, void* buffer, u64 size)
offset_aligned_first_out - first_sec.offset_aligned;
first_sec.address_aligned = first_sec.lba_address + first_sec.offset_aligned;
offset_aligned_first_out = last_sec.size & ~0xF;
total_read = m_file.read_at(first_sec.address_aligned, &first_sec.buf.data()[first_sec.offset_aligned], first_sec.size_aligned);
last_sec.size_aligned = offset_aligned_first_out != last_sec.size ?
offset_aligned_first_out + 16 :
offset_aligned_first_out;
m_dec->decrypt(first_sec.address_aligned, &first_sec.buf.data()[first_sec.offset_aligned], first_sec.size_aligned, m_meta.name);
memcpy(buffer, &first_sec.buf.data()[first_sec.offset], first_sec.size);
u64 sector_count = (last_sec.lba_address - first_sec.lba_address) / ISO_SECTOR_SIZE + 1;
u64 sector_inner_size = sector_count > 2 ? (sector_count - 2) * ISO_SECTOR_SIZE : 0;
u64 expected_read;
expected_read = first_sec.size_aligned;
total_read = m_file.read_at(first_sec.address_aligned, &first_sec.buf.data()[first_sec.offset_aligned], first_sec.size_aligned);
if (sector_count < 2) // If no more sector(s)
{
if (total_read != first_sec.size_aligned)
{
sys_log.error("read_at(): %s: Error reading from file", m_meta.name);
seek(m_pos, fs::seek_set);
return 0;
}
return max_size;
}
//
// Inner sector(s), if any
//
u64 expected_inner_sector_read = 0;
if (sector_count > 2) // If inner sector(s) are present
{
expected_read += sector_inner_size;
total_read += m_file.read_at(first_sec.lba_address + ISO_SECTOR_SIZE, &reinterpret_cast<u8*>(buffer)[first_sec.size], sector_inner_size);
u64 inner_sector_size = expected_inner_sector_read = (sector_count - 2) * ISO_SECTOR_SIZE;
total_read += m_file.read_at(first_sec.lba_address + ISO_SECTOR_SIZE, &reinterpret_cast<u8*>(buffer)[first_sec.size], inner_sector_size);
m_dec->decrypt(first_sec.lba_address + ISO_SECTOR_SIZE, &reinterpret_cast<u8*>(buffer)[first_sec.size], inner_sector_size, m_meta.name);
}
if (sector_count > 1) // If last sector is present
{
expected_read += last_sec.size_aligned;
total_read += m_file.read_at(last_sec.address_aligned, last_sec.buf.data(), last_sec.size_aligned);
}
//
// Last sector
//
if (total_read != expected_read)
offset_aligned_first_out = last_sec.size & ~0xF;
last_sec.size_aligned = offset_aligned_first_out != last_sec.size ? offset_aligned_first_out + 16 : offset_aligned_first_out;
total_read += m_file.read_at(last_sec.address_aligned, last_sec.buf.data(), last_sec.size_aligned);
m_dec->decrypt(last_sec.address_aligned, last_sec.buf.data(), last_sec.size_aligned, m_meta.name);
memcpy(&reinterpret_cast<u8*>(buffer)[max_size - last_sec.size], last_sec.buf.data(), last_sec.size);
//
// As last, check for an unlikely reading error (decoding also failed due to use of partially initialized buffer)
//
if (total_read != first_sec.size_aligned + last_sec.size_aligned + expected_inner_sector_read)
{
sys_log.error("read_at(): %s: Error reading from file", m_meta.name);
@ -896,20 +927,6 @@ u64 iso_file::read_at(u64 offset, void* buffer, u64 size)
return 0;
}
m_dec->decrypt(first_sec.address_aligned, &first_sec.buf.data()[first_sec.offset_aligned], first_sec.size_aligned, m_meta.name);
memcpy(buffer, &first_sec.buf.data()[first_sec.offset], first_sec.size);
if (sector_count > 2) // If inner sector(s) are present
{
m_dec->decrypt(first_sec.lba_address + ISO_SECTOR_SIZE, &reinterpret_cast<u8*>(buffer)[first_sec.size], sector_inner_size, m_meta.name);
}
if (sector_count > 1) // If last sector is present
{
m_dec->decrypt(last_sec.address_aligned, last_sec.buf.data(), last_sec.size_aligned, m_meta.name);
memcpy(&reinterpret_cast<u8*>(buffer)[max_size - last_sec.size], last_sec.buf.data(), last_sec.size);
}
return max_size;
}