Atmosphere/exosphere/loader_stub/source/secmon_loader_uncompress.cpp
2020-06-14 22:07:45 -07:00

103 lines
3.8 KiB
C++

/*
* Copyright (c) 2018-2020 Atmosphère-NX
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <exosphere.hpp>
#include "secmon_loader_uncompress.hpp"
namespace ams::secmon::loader {
namespace {
class Lz4Uncompressor {
private:
const u8 *src;
size_t src_size;
size_t src_offset;
u8 *dst;
size_t dst_size;
size_t dst_offset;
public:
Lz4Uncompressor(void *dst, size_t dst_size, const void *src, size_t src_size) : src(static_cast<const u8 *>(src)), src_size(src_size), src_offset(0), dst(static_cast<u8 *>(dst)), dst_size(dst_size), dst_offset(0) {
/* ... */
}
void Uncompress() {
while (true) {
/* Read a control byte. */
const u8 control = this->ReadByte();
/* Copy what it specifies we should copy. */
this->Copy(this->GetCopySize(control >> 4));
/* If we've exceeded size, we're done. */
if (this->src_offset >= this->src_size) {
break;
}
/* Read the wide copy offset. */
u16 wide_offset = this->ReadByte();
AMS_ABORT_UNLESS(this->CanRead());
wide_offset |= (this->ReadByte() << 8);
/* Determine the copy size. */
const size_t wide_copy_size = this->GetCopySize(control & 0xF);
/* Copy bytes. */
const size_t end_offset = this->dst_offset + wide_copy_size + 4;
for (size_t cur_offset = this->dst_offset; cur_offset < end_offset; this->dst_offset = (++cur_offset)) {
AMS_ABORT_UNLESS(wide_offset <= cur_offset);
this->dst[cur_offset] = this->dst[cur_offset - wide_offset];
}
}
}
private:
u8 ReadByte() {
return this->src[this->src_offset++];
}
bool CanRead() const {
return this->src_offset < this->src_size;
}
size_t GetCopySize(u8 control) {
size_t size = control;
if (control >= 0xF) {
do {
AMS_ABORT_UNLESS(this->CanRead());
control = this->ReadByte();
size += control;
} while (control == 0xFF);
}
return size;
}
void Copy(size_t size) {
__builtin_memcpy(this->dst + this->dst_offset, this->src + this->src_offset, size);
this->dst_offset += size;
this->src_offset += size;
}
};
}
void Uncompress(void *dst, size_t dst_size, const void *src, size_t src_size) {
/* Create an execute a decompressor. */
Lz4Uncompressor(dst, dst_size, src, src_size).Uncompress();
}
}