# ---------------------------------------------------------------------------------------------------------------------
# link_bitstreams.py
# ---------------------------------------------------------------------------------------------------------------------
#
# Glue iCE40 bitstream to the main FPGA bitstream. The MKM bitstream is aligned on a sector boundary.
#
# ---------------------------------------------------------------------------------------------------------------------
#
# Copyright 2021 The Commons Conservancy Cryptech Project
#
# SPDX-License-Identifier: BSD-3-Clause
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice,
#   this list of conditions and the following disclaimer.
#
# * Redistributions in binary form must reproduce the above copyright notice,
#   this list of conditions and the following disclaimer in the documentation
#   and/or other materials provided with the distribution.
#
# * Neither the name of the copyright holder nor the names of its contributors
#   may be used to endorse or promote products derived from this software
#   without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
# OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
# OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
# ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
# ---------------------------------------------------------------------------------------------------------------------


# ---------------------------------------------------------------------------------------------------------------------
# Imports
# ---------------------------------------------------------------------------------------------------------------------
import os
import sys
import math


# ---------------------------------------------------------------------------------------------------------------------
# More Imports
# ---------------------------------------------------------------------------------------------------------------------
from enum import Enum
from typing import Optional


# ---------------------------------------------------------------------------------------------------------------------
# Markers
# ---------------------------------------------------------------------------------------------------------------------
MARKER_XILINX = b"\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF" \
                b"\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF" \
                b"\x00\x00\x00\xBB\x11\x22\x00\x44\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF" \
                b"\xAA\x99\x55\x66"

MARKER_LATTICE = b"\x7E\xAA\x99\x7E"


# ---------------------------------------------------------------------------------------------------------------------
class FPGA(Enum):
    Artix7 = 'artix7'
    iCE40 = 'ice40'
# ---------------------------------------------------------------------------------------------------------------------


# ---------------------------------------------------------------------------------------------------------------------
# Settings
# ---------------------------------------------------------------------------------------------------------------------
PROM_PAGE_BYTES = 256
PROM_SECTOR_BYTES = 256 * PROM_PAGE_BYTES

MARKER_DICT = {FPGA.Artix7: MARKER_XILINX,
               FPGA.iCE40: MARKER_LATTICE}


# ---------------------------------------------------------------------------------------------------------------------
def _load_bitstream(filename: str, fpga: FPGA) -> Optional[bytes]:

    # try to load input bitstream
    try:
        with open(filename, 'rb') as f:
            bitstream = f.read()

    except FileNotFoundError:
        print("File '%s' not found." % filename)
        return

    finally:
        len_bitstream_orig = len(bitstream)
        print("File '%s' loaded, %d bytes." % (filename, len_bitstream_orig))

    # check magic marker and strip leading bytes
    bitstream = _check_marker(bitstream, fpga)

    # done
    return bitstream
# ---------------------------------------------------------------------------------------------------------------------


# ---------------------------------------------------------------------------------------------------------------------
def _check_marker(bitstream: bytes, fpga: FPGA) -> Optional[bytes]:

    len_bitstream_orig = len(bitstream)
    marker = MARKER_DICT[fpga]

    # check, that marker is present
    if marker not in bitstream:
        print("  Magic marker for device '%s' not found, did you specify the right filename?" % fpga.value)
        return

    # try to strip leading redundant bytes
    while not bitstream.startswith(marker):
        bitstream = bitstream[1:]

    # print how many bytes we stripped
    num_stripped_bytes = len_bitstream_orig - len(bitstream)
    print("  Stripped %d bytes before the magic marker." % num_stripped_bytes)

    # done
    return bitstream
# ---------------------------------------------------------------------------------------------------------------------


# ---------------------------------------------------------------------------------------------------------------------
def _save_bit(bitstream: bytes, filename: str) -> int:

    # write memory to file
    with open(filename, 'wb') as f:
        f.write(bitstream)

    print("Output bitstream written.")

    # done
    return 0
# ---------------------------------------------------------------------------------------------------------------------


# ---------------------------------------------------------------------------------------------------------------------
def _link_bitstreams(filename_artix7: str, filename_ice40: str, filename_output: str) -> int:

    # load bitstream
    bitstream_artix7 = _load_bitstream(filename_artix7, FPGA.Artix7)
    bitstream_ice40 = _load_bitstream(filename_ice40, FPGA.iCE40)
    if bitstream_artix7 is None or bitstream_ice40 is None:
        return 1

    # grow main bitstream to sector boundary
    num_sectors_artix7 = math.ceil(len(bitstream_artix7) / PROM_SECTOR_BYTES)
    num_padding_bytes = num_sectors_artix7 * PROM_SECTOR_BYTES - len(bitstream_artix7)
    print("Added %d byte(s) after the main bitstream to align the MKM bitmap on sector boundary." % num_padding_bytes)
    padding_bytes = bytes(0xFF for _ in range(num_padding_bytes))
    bitstream_artix7_padded = bitstream_artix7 + padding_bytes

    # glue two bitstreams
    bitstream_output = bitstream_artix7_padded + bitstream_ice40

    # fill bitstream with 0xFF's up to page boundary
    num_padding_bytes = PROM_PAGE_BYTES - (len(bitstream_output) % 256)
    print("Added %d byte(s) after the mkm bitmap to align output on page boundary." % num_padding_bytes)
    padding_bytes = bytes(0xFF for _ in range(num_padding_bytes))
    bitstream_output += padding_bytes

    # save bit
    return _save_bit(bitstream_output, filename_output)
# ---------------------------------------------------------------------------------------------------------------------


# ---------------------------------------------------------------------------------------------------------------------
def print_usage() -> int:
    print("USAGE: %s <fpga_bitstream.bit> <mkm_bitmap.bin> <combined_bitstream.bit>" %
          os.path.basename(sys.argv[0]))
    return 2
# ---------------------------------------------------------------------------------------------------------------------


# ---------------------------------------------------------------------------------------------------------------------
def main() -> int:

    # check, that exactly three arguments were supplied
    if len(sys.argv) != 4:
        return print_usage()

    # now run the script
    return _link_bitstreams(*sys.argv[1:4])
# ---------------------------------------------------------------------------------------------------------------------


# ---------------------------------------------------------------------------------------------------------------------
if __name__ == '__main__':
    sys.exit(main())
# ---------------------------------------------------------------------------------------------------------------------


# ---------------------------------------------------------------------------------------------------------------------
# End-of-File
# ---------------------------------------------------------------------------------------------------------------------