Ковыряем deSPIRIA - Версия для печати

Код:
import struct

import sys



def lzss_decompress(data: bytes) -> bytes:

    print("  [LZSS] Checking input length...")

    if len(data) < 5:

        raise ValueError("LZSS input is too short")



    target_size = struct.unpack_from("<I", data, 0)[0]

    print(f"  [LZSS] Target size from header: {target_size} bytes")

    if target_size <= 0:

        raise ValueError(f"Invalid LZSS decompressed size: {target_size}")



    ring = bytearray(4096)

    ring_pos = 0xFEE

    src_pos = 4

    out = bytearray()



    print("  [LZSS] Starting decompression loop...")

    while src_pos < len(data) and len(out) < target_size:

        flags = data[src_pos]

        src_pos += 1



        for bit in range(8):

            if flags & (1 << bit):

                # Literal byte

                if src_pos >= len(data):

                    raise ValueError("Truncated LZSS literal")



                value = data[src_pos]

                src_pos += 1



                out.append(value)

                ring[ring_pos] = value

                ring_pos = (ring_pos + 1) & 0xFFF

            else:

                # Two-byte back-reference

                if src_pos + 1 >= len(data):

                    raise ValueError("Truncated LZSS back-reference")



                b0 = data[src_pos]

                b1 = data[src_pos + 1]

                src_pos += 2



                offset = b0 | ((b1 & 0xF0) << 4)

                length = (b1 & 0x0F) + 3



                for i in range(length):

                    value = ring[(offset + i) & 0xFFF]

                    out.append(value)

                    ring[ring_pos] = value

                    ring_pos = (ring_pos + 1) & 0xFFF



                    if len(out) >= target_size:

                        break



            if len(out) >= target_size:

                break



    if len(out) != target_size:

        raise ValueError(

            f"LZSS stream ended at {len(out):,} bytes; expected {target_size:,}"

        )



    return bytes(out)



def main():

    print("=== LZSS Decompressor started ===")

    if len(sys.argv) < 3:

        print("Usage: python lzss_decompress.py <input.cpr> <output.bin>")

        sys.exit(1)



    input_path = sys.argv[1]

    output_path = sys.argv[2]



    print(f"[MAIN] Input: {input_path}")

    print(f"[MAIN] Output: {output_path}")



    try:

        with open(input_path, "rb") as f:

            data = f.read()

        print(f"[MAIN] Read {len(data)} bytes from input file")

    except FileNotFoundError:

        print(f"ERROR: Input file not found: {input_path}", file=sys.stderr)

        sys.exit(1)

    except Exception as e:

        print(f"ERROR reading file: {e}", file=sys.stderr)

        sys.exit(1)



    try:

        decompressed = lzss_decompress(data)

        print(f"[MAIN] Decompressed to {len(decompressed)} bytes")

    except ValueError as e:

        print(f"LZSS decompression error: {e}", file=sys.stderr)

        sys.exit(1)

    except Exception as e:

        print(f"Unexpected error during decompression: {e}", file=sys.stderr)

        sys.exit(1)



    try:

        with open(output_path, "wb") as f:

            f.write(decompressed)

        print(f"[MAIN] Wrote {len(decompressed)} bytes to output file")

        print("=== Done ===")

    except Exception as e:

        print(f"Error writing output file: {e}", file=sys.stderr)

        sys.exit(1)



if __name__ == "__main__":

    main()