LZSS decoder for textures in Resident Evil Outbreak

OutbreakLZSSDecoder.cpp

#include <cstdint>
#include <cstdlib>
#include <cstdio>
#include <cstring>

int main(int argc, char* argv[])
{
    char* inputFilename = argv[1];
    char* outputFilename = argv[2];
    
    FILE* inputFP = fopen(inputFilename, "rb+");
    fseek(inputFP, 0, SEEK_END);
    size_t srcSize = ftell(inputFP);
    fseek(inputFP, 0, SEEK_SET);
    
    FILE* outputFP = fopen(outputFilename, "wb+");
    
    uint16_t* dest = (uint16_t*)malloc(16 * 1024 * 1024);
    memset(dest, 0x00, 16 * 1024 * 1024);
    uint32_t dest_pos = 0;
    uint32_t blockSize = 0;
    uint16_t flag = 0;
    while (ftell(inputFP) < srcSize)
    {
        if (blockSize == 0)
        {
            fread(&flag, 2, 1, inputFP);
            blockSize = 16;
        }
        
        if (flag & 0x8000)
        {
            uint16_t mode;
            fread(&mode, 2, 1, inputFP);
            
            uint16_t count = mode >> 0xb;
            if (count == 0)
            {
                fread(&count, 2, 1, inputFP);
            }
            
            uint16_t offset = mode & 0x7ff;
            if (offset == 0)
            {
                for (int i = 0; i < count; i++)
                {
                    dest[dest_pos] = 0;
                    dest_pos++;
                }
            }
            else
            {
                uint32_t pos = dest_pos - offset;
                for (int i = 0; i < count; i++)
                {
                    dest[dest_pos] = dest[pos + i];
                    dest_pos++;
                }
            }
        }
        else
        {
            uint16_t val;
            fread(&val, 2, 1, inputFP);
            dest[dest_pos] = val;
            dest_pos++;
        }
        flag = flag << 1;
        blockSize--;
    }
    
    fwrite(dest, dest_pos*2, 1, outputFP);
    fclose(inputFP);
    fclose(outputFP);
    return 1;
}