import struct, sys

def unpack_bytes(len, bytes):
    if len == 3:
        bytes.extend(b'\x00')
    return struct.unpack('<I', bytes)[0]

def read_pgz_file(file_path):
    with open(file_path, 'rb') as file:
        # Read the file type signature (first byte)
        signature = file.read(1)
        
        # Determine the address and size format
        if signature == b'Z':
            address_size_format = 3	    # 24 bit
            print('Signature: "Z"  24-bit addresses\n')
        elif signature == b'z':
            address_size_format = 4     # 32 bit
            print('Signature: "z"  32-bit addresses \n')
        else:
            print("Invalid PGZ file. Signature 'Z' not found.")
            return 
        
        # Read segments
        segment_number = 1
        while True:
            address = unpack_bytes(address_size_format,bytearray(file.read(address_size_format)))
            #print(f'Adr: {address:06x}')
            size = unpack_bytes(address_size_format,bytearray(file.read(address_size_format)))

            if size == 0:
                # Final segment with size $000000 indicates the starting address of the executable
                print(f"Segment {segment_number}: Starting address of the executable: {hex(address)}")
                break

            print(f"Segment {segment_number}: Address: ${address:06x}, Size: ${size:06x}  ({size})")

            # Read data of the segment
            data = file.read(size)
            # Process or display data as needed
            # For example, you can print the data in hex format: print(f"Data: {data.hex()}")
            segment_number += 1
        print()

if __name__ == "__main__":
    if len(sys.argv) < 2:
        print("Add pgz argument to command.")
    else:    
        pgz_file_path = sys.argv[1]
        read_pgz_file(pgz_file_path)