#!/usr/bin/env python3.5
# Copyright 2014-2017 Robert Jordens <jordens@gmail.com>
# after
# https://github.com/mfischer/fpgadev-zynq/blob/master/top/python/bit_to_zynq_bin.py

import struct


def flip32(data):
    sl = struct.Struct("<I")
    sb = struct.Struct(">I")
    b = memoryview(data)
    d = bytearray(len(data))
    for offset in range(0, len(data), sl.size):
         sb.pack_into(d, offset, *sl.unpack_from(b, offset))
    return d


def bit2bin(bit, bin, flip=False):
    with open(bit, "rb") as bitfile:
        l, = struct.unpack(">H", bitfile.read(2))
        if l != 9:
            raise ValueError("Missing <0009> header, not a bit file")

        bitfile.read(l)
        d = bitfile.read(*struct.unpack(">H", bitfile.read(2)))
        if d != b"a":
            raise ValueError("Missing <a> header, not a bit file")

        d = bitfile.read(*struct.unpack(">H", bitfile.read(2)))
        print("Design name:", d)

        while True:
            key = bitfile.read(1)
            if not key:
                break
            if key in b"bcd":
                d = bitfile.read(*struct.unpack(">H", bitfile.read(2)))
                name = {b"b": "Partname", b"c": "Date", b"d": "Time"}[key]
                print(name, d)
            elif key == b"e":
                l, = struct.unpack(">I", bitfile.read(4))
                print("found binary data length:", l)
                d = bitfile.read(l)
                if flip:
                    d = flip32(d)
                with open(bin, "wb") as f:
                    f.write(d)
            else:
                d = bitfile.read(*struct.unpack(">H", bitfile.read(2)))
                print("Unexpected key: ", key, d)


if __name__ == "__main__":
    import argparse
    parser = argparse.ArgumentParser(
        description="Convert FPGA bit files to raw bin format "
                    "suitable for flashing")
    parser.add_argument("-f", "--flip", dest="flip", action="store_true",
            default=False, help="Flip 32-bit endianess (needed for Zynq)")
    parser.add_argument("bitfile", metavar="BITFILE",
                        help="Input bit file name")
    parser.add_argument("binfile", metavar="BINFILE",
                        help="Output bin file name")
    args = parser.parse_args()

    bit2bin(args.bitfile, args.binfile, args.flip)