#!/usr/bin/env python3

# Copyright (c) 2019 - 2020 Nordic Semiconductor ASA
# Copyright (c) 2019 Linaro Limited
# SPDX-License-Identifier: BSD-3-Clause

# This script uses edtlib to generate a header file from a devicetree
# (.dts) file. Information from binding files in YAML format is used
# as well.
#
# Bindings are files that describe devicetree nodes. Devicetree nodes are
# usually mapped to bindings via their 'compatible = "..."' property.
#
# See Zephyr's Devicetree user guide for details.
#
# Note: Do not access private (_-prefixed) identifiers from edtlib here (and
# also note that edtlib is not meant to expose the dtlib API directly).
# Instead, think of what API you need, and add it as a public documented API in
# edtlib. This will keep this script simple.

import argparse
from collections import defaultdict
import os
import pathlib
import pickle
import re
import sys

import edtlib

def main():
    global header_file
    global flash_area_num

    args = parse_args()

    try:
        edt = edtlib.EDT(args.dts, args.bindings_dirs,
                         # Suppress this warning if it's suppressed in dtc
                         warn_reg_unit_address_mismatch=
                             "-Wno-simple_bus_reg" not in args.dtc_flags,
                         default_prop_types=True,
                         infer_binding_for_paths=["/zephyr,user"])
    except edtlib.EDTError as e:
        sys.exit(f"devicetree error: {e}")

    flash_area_num = 0

    # Save merged DTS source, as a debugging aid
    with open(args.dts_out, "w", encoding="utf-8") as f:
        print(edt.dts_source, file=f)

    # The raw index into edt.compat2nodes[compat] is used for node
    # instance numbering within a compatible.
    #
    # As a way to satisfy people's intuitions about instance numbers,
    # though, we sort this list so enabled instances come first.
    #
    # This might look like a hack, but it keeps drivers and
    # applications which don't use instance numbers carefully working
    # as expected, since e.g. instance number 0 is always the
    # singleton instance if there's just one enabled node of a
    # particular compatible.
    #
    # This doesn't violate any devicetree.h API guarantees about
    # instance ordering, since we make no promises that instance
    # numbers are stable across builds.
    for compat, nodes in edt.compat2nodes.items():
        edt.compat2nodes[compat] = sorted(
            nodes, key=lambda node: 0 if node.status == "okay" else 1)

    # Create the generated header.
    with open(args.header_out, "w", encoding="utf-8") as header_file:
        write_top_comment(edt)

        # populate all z_path_id first so any children references will
        # work correctly.
        for node in sorted(edt.nodes, key=lambda node: node.dep_ordinal):
            node.z_path_id = node_z_path_id(node)

        for node in sorted(edt.nodes, key=lambda node: node.dep_ordinal):
            write_node_comment(node)

            if node.parent is not None:
                out_comment(f"Node parent ({node.parent.path}) identifier:")
                out_dt_define(f"{node.z_path_id}_PARENT",
                              f"DT_{node.parent.z_path_id}")

            write_child_functions(node)
            write_idents_and_existence(node)
            write_bus(node)
            write_special_props(node)
            write_vanilla_props(node)

        write_chosen(edt)
        write_global_compat_info(edt)

    if args.edt_pickle_out:
        write_pickled_edt(edt, args.edt_pickle_out)


def node_z_path_id(node):
    # Return the node specific bit of the node's path identifier:
    #
    # - the root node's path "/" has path identifier "N"
    # - "/foo" has "N_S_foo"
    # - "/foo/bar" has "N_S_foo_S_bar"
    # - "/foo/bar@123" has "N_S_foo_S_bar_123"
    #
    # This is used throughout this file to generate macros related to
    # the node.

    components = ["N"]
    if node.parent is not None:
        components.extend(f"S_{str2ident(component)}" for component in
                          node.path.split("/")[1:])

    return "_".join(components)

def parse_args():
    # Returns parsed command-line arguments

    parser = argparse.ArgumentParser()
    parser.add_argument("--dts", required=True, help="DTS file")
    parser.add_argument("--dtc-flags",
                        help="'dtc' devicetree compiler flags, some of which "
                             "might be respected here")
    parser.add_argument("--bindings-dirs", nargs='+', required=True,
                        help="directory with bindings in YAML format, "
                        "we allow multiple")
    parser.add_argument("--header-out", required=True,
                        help="path to write header to")
    parser.add_argument("--dts-out", required=True,
                        help="path to write merged DTS source code to (e.g. "
                             "as a debugging aid)")
    parser.add_argument("--edt-pickle-out",
                        help="path to write pickled edtlib.EDT object to")

    return parser.parse_args()


def write_top_comment(edt):
    # Writes an overview comment with misc. info at the top of the header and
    # configuration file

    s = f"""\
Generated by gen_defines.py

DTS input file:
  {edt.dts_path}

Directories with bindings:
  {", ".join(map(relativize, edt.bindings_dirs))}

Nodes in dependency order (ordinal and path):
"""

    for scc in edt.scc_order():
        if len(scc) > 1:
            err("cycle in devicetree involving "
                + ", ".join(node.path for node in scc))
        s += f"  {scc[0].dep_ordinal:<3} {scc[0].path}\n"

    s += """
Definitions derived from these nodes in dependency order are next,
followed by /chosen nodes.
"""

    out_comment(s, blank_before=False)


def write_node_comment(node):
    # Writes a comment describing 'node' to the header and configuration file

    s = f"""\
Devicetree node: {node.path}

Node's generated path identifier: DT_{node.z_path_id}
"""

    if node.matching_compat:
        if node.binding_path:
            s += f"""
Binding (compatible = {node.matching_compat}):
  {relativize(node.binding_path)}
"""
        else:
            s += f"""
Binding (compatible = {node.matching_compat}):
  No yaml (bindings inferred from properties)
"""

    s += f"\nDependency Ordinal: {node.dep_ordinal}\n"

    if node.depends_on:
        s += "\nRequires:\n"
        for dep in node.depends_on:
            s += f"  {dep.dep_ordinal:<3} {dep.path}\n"

    if node.required_by:
        s += "\nSupports:\n"
        for req in node.required_by:
            s += f"  {req.dep_ordinal:<3} {req.path}\n"

    if node.description:
        # Indent description by two spaces
        s += "\nDescription:\n" + \
            "\n".join("  " + line for line in
                      node.description.splitlines()) + \
            "\n"

    out_comment(s)


def relativize(path):
    # If 'path' is within $ZEPHYR_BASE, returns it relative to $ZEPHYR_BASE,
    # with a "$ZEPHYR_BASE/..." hint at the start of the string. Otherwise,
    # returns 'path' unchanged.

    zbase = os.getenv("ZEPHYR_BASE")
    if zbase is None:
        return path

    try:
        return str("$ZEPHYR_BASE" / pathlib.Path(path).relative_to(zbase))
    except ValueError:
        # Not within ZEPHYR_BASE
        return path


def write_idents_and_existence(node):
    # Writes macros related to the node's aliases, labels, etc.,
    # as well as existence flags.

    # Aliases
    idents = [f"N_ALIAS_{str2ident(alias)}" for alias in node.aliases]
    # Instances
    for compat in node.compats:
        instance_no = node.edt.compat2nodes[compat].index(node)
        idents.append(f"N_INST_{instance_no}_{str2ident(compat)}")
    # Node labels
    idents.extend(f"N_NODELABEL_{str2ident(label)}" for label in node.labels)

    out_comment("Existence and alternate IDs:")
    out_dt_define(node.z_path_id + "_EXISTS", 1)

    # Only determine maxlen if we have any idents
    if idents:
        maxlen = max(len("DT_" + ident) for ident in idents)
    for ident in idents:
        out_dt_define(ident, "DT_" + node.z_path_id, width=maxlen)


def write_bus(node):
    # Macros about the node's bus controller, if there is one

    bus = node.bus_node
    if not bus:
        return

    if not bus.label:
        err(f"missing 'label' property on bus node {bus!r}")

    out_comment(f"Bus info (controller: '{bus.path}', type: '{node.on_bus}')")
    out_dt_define(f"{node.z_path_id}_BUS_{str2ident(node.on_bus)}", 1)
    out_dt_define(f"{node.z_path_id}_BUS", f"DT_{bus.z_path_id}")


def write_special_props(node):
    # Writes required macros for special case properties, when the
    # data cannot otherwise be obtained from write_vanilla_props()
    # results

    global flash_area_num

    out_comment("Special property macros:")

    # Macros that are special to the devicetree specification
    write_regs(node)
    write_interrupts(node)
    write_compatibles(node)
    write_status(node)

    if node.parent and "fixed-partitions" in node.parent.compats:
        macro = f"{node.z_path_id}_PARTITION_ID"
        out_dt_define(macro, flash_area_num)
        flash_area_num += 1

def write_regs(node):
    # reg property: edtlib knows the right #address-cells and
    # #size-cells, and can therefore pack the register base addresses
    # and sizes correctly

    idx_vals = []
    name_vals = []
    path_id = node.z_path_id

    if node.regs is not None:
        idx_vals.append((f"{path_id}_REG_NUM", len(node.regs)))

    for i, reg in enumerate(node.regs):
        idx_vals.append((f"{path_id}_REG_IDX_{i}_EXISTS", 1))
        if reg.addr is not None:
            idx_macro = f"{path_id}_REG_IDX_{i}_VAL_ADDRESS"
            idx_vals.append((idx_macro,
                             f"{reg.addr} /* {hex(reg.addr)} */"))
            if reg.name:
                name_macro = f"{path_id}_REG_NAME_{reg.name}_VAL_ADDRESS"
                name_vals.append((name_macro, f"DT_{idx_macro}"))

        if reg.size is not None:
            idx_macro = f"{path_id}_REG_IDX_{i}_VAL_SIZE"
            idx_vals.append((idx_macro,
                             f"{reg.size} /* {hex(reg.size)} */"))
            if reg.name:
                name_macro = f"{path_id}_REG_NAME_{reg.name}_VAL_SIZE"
                name_vals.append((name_macro, f"DT_{idx_macro}"))

    for macro, val in idx_vals:
        out_dt_define(macro, val)
    for macro, val in name_vals:
        out_dt_define(macro, val)

def write_interrupts(node):
    # interrupts property: we have some hard-coded logic for interrupt
    # mapping here.
    #
    # TODO: can we push map_arm_gic_irq_type() and
    # encode_zephyr_multi_level_irq() out of Python and into C with
    # macro magic in devicetree.h?

    def map_arm_gic_irq_type(irq, irq_num):
        # Maps ARM GIC IRQ (type)+(index) combo to linear IRQ number
        if "type" not in irq.data:
            err(f"Expected binding for {irq.controller!r} to have 'type' in "
                "interrupt-cells")
        irq_type = irq.data["type"]

        if irq_type == 0:  # GIC_SPI
            return irq_num + 32
        if irq_type == 1:  # GIC_PPI
            return irq_num + 16
        err(f"Invalid interrupt type specified for {irq!r}")

    def encode_zephyr_multi_level_irq(irq, irq_num):
        # See doc/reference/kernel/other/interrupts.rst for details
        # on how this encoding works

        irq_ctrl = irq.controller
        # Look for interrupt controller parent until we have none
        while irq_ctrl.interrupts:
            irq_num = (irq_num + 1) << 8
            if "irq" not in irq_ctrl.interrupts[0].data:
                err(f"Expected binding for {irq_ctrl!r} to have 'irq' in "
                    "interrupt-cells")
            irq_num |= irq_ctrl.interrupts[0].data["irq"]
            irq_ctrl = irq_ctrl.interrupts[0].controller
        return irq_num

    idx_vals = []
    name_vals = []
    path_id = node.z_path_id

    if node.interrupts is not None:
        idx_vals.append((f"{path_id}_IRQ_NUM", len(node.interrupts)))

    for i, irq in enumerate(node.interrupts):
        for cell_name, cell_value in irq.data.items():
            name = str2ident(cell_name)

            if cell_name == "irq":
                if "arm,gic" in irq.controller.compats:
                    cell_value = map_arm_gic_irq_type(irq, cell_value)
                cell_value = encode_zephyr_multi_level_irq(irq, cell_value)

            idx_vals.append((f"{path_id}_IRQ_IDX_{i}_EXISTS", 1))
            idx_macro = f"{path_id}_IRQ_IDX_{i}_VAL_{name}"
            idx_vals.append((idx_macro, cell_value))
            idx_vals.append((idx_macro + "_EXISTS", 1))
            if irq.name:
                name_macro = \
                    f"{path_id}_IRQ_NAME_{str2ident(irq.name)}_VAL_{name}"
                name_vals.append((name_macro, f"DT_{idx_macro}"))
                name_vals.append((name_macro + "_EXISTS", 1))

    for macro, val in idx_vals:
        out_dt_define(macro, val)
    for macro, val in name_vals:
        out_dt_define(macro, val)


def write_compatibles(node):
    # Writes a macro for each of the node's compatibles. We don't care
    # about whether edtlib / Zephyr's binding language recognizes
    # them. The compatibles the node provides are what is important.

    for compat in node.compats:
        out_dt_define(
            f"{node.z_path_id}_COMPAT_MATCHES_{str2ident(compat)}", 1)


def write_child_functions(node):
    # Writes macro that are helpers that will call a macro/function
    # for each child node.

    out_dt_define(f"{node.z_path_id}_FOREACH_CHILD(fn)",
            " ".join(f"fn(DT_{child.z_path_id})" for child in
                node.children.values()))


def write_status(node):
    out_dt_define(f"{node.z_path_id}_STATUS_{str2ident(node.status)}", 1)


def write_vanilla_props(node):
    # Writes macros for any and all properties defined in the
    # "properties" section of the binding for the node.
    #
    # This does generate macros for special properties as well, like
    # regs, etc. Just let that be rather than bothering to add
    # never-ending amounts of special case code here to skip special
    # properties. This function's macros can't conflict with
    # write_special_props() macros, because they're in different
    # namespaces. Special cases aren't special enough to break the rules.

    macro2val = {}
    for prop_name, prop in node.props.items():
        macro = f"{node.z_path_id}_P_{str2ident(prop_name)}"
        val = prop2value(prop)
        if val is not None:
            # DT_N_<node-id>_P_<prop-id>
            macro2val[macro] = val

        if prop.enum_index is not None:
            # DT_N_<node-id>_P_<prop-id>_ENUM_IDX
            macro2val[macro + "_ENUM_IDX"] = prop.enum_index

        if "phandle" in prop.type:
            macro2val.update(phandle_macros(prop, macro))
        elif "array" in prop.type:
            # DT_N_<node-id>_P_<prop-id>_IDX_<i>
            for i, subval in enumerate(prop.val):
                if isinstance(subval, str):
                    macro2val[macro + f"_IDX_{i}"] = quote_str(subval)
                else:
                    macro2val[macro + f"_IDX_{i}"] = subval

        plen = prop_len(prop)
        if plen is not None:
            # DT_N_<node-id>_P_<prop-id>_LEN
            macro2val[macro + "_LEN"] = plen

        macro2val[f"{macro}_EXISTS"] = 1

    if macro2val:
        out_comment("Generic property macros:")
        for macro, val in macro2val.items():
            out_dt_define(macro, val)
    else:
        out_comment("(No generic property macros)")


def prop2value(prop):
    # Gets the macro value for property 'prop', if there is
    # a single well-defined C rvalue that it can be represented as.
    # Returns None if there isn't one.

    if prop.type == "string":
        return quote_str(prop.val)

    if prop.type == "int":
        return prop.val

    if prop.type == "boolean":
        return 1 if prop.val else 0

    if prop.type in ["array", "uint8-array"]:
        return list2init(f"{val} /* {hex(val)} */" for val in prop.val)

    if prop.type == "string-array":
        return list2init(quote_str(val) for val in prop.val)

    # phandle, phandles, phandle-array, path, compound: nothing
    return None


def prop_len(prop):
    # Returns the property's length if and only if we should generate
    # a _LEN macro for the property. Otherwise, returns None.
    #
    # This deliberately excludes reg and interrupts.
    # While they have array type, their lengths as arrays are
    # basically nonsense semantically due to #address-cells and
    # #size-cells for "reg" and #interrupt-cells for "interrupts".
    #
    # We have special purpose macros for the number of register blocks
    # / interrupt specifiers. Excluding them from this list means
    # DT_PROP_LEN(node_id, ...) fails fast at the devicetree.h layer
    # with a build error. This forces users to switch to the right
    # macros.

    if prop.type == "phandle":
        return 1

    if (prop.type in ["array", "uint8-array", "string-array",
                      "phandles", "phandle-array"] and
                prop.name not in ["reg", "interrupts"]):
        return len(prop.val)

    return None


def phandle_macros(prop, macro):
    # Returns a dict of macros for phandle or phandles property 'prop'.
    #
    # The 'macro' argument is the N_<node-id>_P_<prop-id> bit.
    #
    # These are currently special because we can't serialize their
    # values without using label properties, which we're trying to get
    # away from needing in Zephyr. (Label properties are great for
    # humans, but have drawbacks for code size and boot time.)
    #
    # The names look a bit weird to make it easier for devicetree.h
    # to use the same macros for phandle, phandles, and phandle-array.

    ret = {}

    if prop.type == "phandle":
        # A phandle is treated as a phandles with fixed length 1.
        ret[f"{macro}_IDX_0_PH"] = f"DT_{prop.val.z_path_id}"
    elif prop.type == "phandles":
        for i, node in enumerate(prop.val):
            ret[f"{macro}_IDX_{i}_PH"] = f"DT_{node.z_path_id}"
    elif prop.type == "phandle-array":
        for i, entry in enumerate(prop.val):
            ret.update(controller_and_data_macros(entry, i, macro))

    return ret


def controller_and_data_macros(entry, i, macro):
    # Helper procedure used by phandle_macros().
    #
    # Its purpose is to write the "controller" (i.e. label property of
    # the phandle's node) and associated data macros for a
    # ControllerAndData.

    ret = {}
    data = entry.data

    # DT_N_<node-id>_P_<prop-id>_IDX_<i>_PH
    ret[f"{macro}_IDX_{i}_PH"] = f"DT_{entry.controller.z_path_id}"
    # DT_N_<node-id>_P_<prop-id>_IDX_<i>_VAL_<VAL>
    for cell, val in data.items():
        ret[f"{macro}_IDX_{i}_VAL_{str2ident(cell)}"] = val
        ret[f"{macro}_IDX_{i}_VAL_{str2ident(cell)}_EXISTS"] = 1

    if not entry.name:
        return ret

    name = str2ident(entry.name)
    # DT_N_<node-id>_P_<prop-id>_IDX_<i>_EXISTS
    ret[f"{macro}_IDX_{i}_EXISTS"] = 1
    # DT_N_<node-id>_P_<prop-id>_IDX_<i>_NAME
    ret[f"{macro}_IDX_{i}_NAME"] = quote_str(entry.name)
    # DT_N_<node-id>_P_<prop-id>_NAME_<NAME>_PH
    ret[f"{macro}_NAME_{name}_PH"] = f"DT_{entry.controller.z_path_id}"
    # DT_N_<node-id>_P_<prop-id>_NAME_<NAME>_EXISTS
    ret[f"{macro}_NAME_{name}_EXISTS"] = 1
    # DT_N_<node-id>_P_<prop-id>_NAME_<NAME>_VAL_<VAL>
    for cell, val in data.items():
        cell_ident = str2ident(cell)
        ret[f"{macro}_NAME_{name}_VAL_{cell_ident}"] = \
            f"DT_{macro}_IDX_{i}_VAL_{cell_ident}"
        ret[f"{macro}_NAME_{name}_VAL_{cell_ident}_EXISTS"] = 1

    return ret


def write_chosen(edt):
    # Tree-wide information such as chosen nodes is printed here.

    out_comment("Chosen nodes\n")
    chosen = {}
    for name, node in edt.chosen_nodes.items():
        chosen[f"DT_CHOSEN_{str2ident(name)}"] = f"DT_{node.z_path_id}"
        chosen[f"DT_CHOSEN_{str2ident(name)}_EXISTS"] = 1
    max_len = max(map(len, chosen), default=0)
    for macro, value in chosen.items():
        out_define(macro, value, width=max_len)


def write_global_compat_info(edt):
    # Tree-wide information related to each compatible, such as number
    # of instances with status "okay", is printed here.

    n_okay_macros = {}
    for_each_macros = {}
    compat2buses = defaultdict(list)  # just for "okay" nodes
    for compat, okay_nodes in edt.compat2okay.items():
        for node in okay_nodes:
            bus = node.on_bus
            if bus is not None and bus not in compat2buses[compat]:
                compat2buses[compat].append(bus)

        ident = str2ident(compat)
        n_okay_macros[f"DT_N_INST_{ident}_NUM_OKAY"] = len(okay_nodes)
        for_each_macros[f"DT_FOREACH_OKAY_INST_{ident}(fn)"] = \
            " ".join(f"fn({edt.compat2nodes[compat].index(node)})"
                     for node in okay_nodes)

    for compat, nodes in edt.compat2nodes.items():
        for node in nodes:
            if compat == "fixed-partitions":
                for child in node.children.values():
                    if "label" in child.props:
                        label = child.props["label"].val
                        macro = f"COMPAT_{str2ident(compat)}_LABEL_{str2ident(label)}"
                        val = f"DT_{child.z_path_id}"

                        out_dt_define(macro, val)
                        out_dt_define(macro + "_EXISTS", 1)

    out_comment('Macros for compatibles with status "okay" nodes\n')
    for compat, okay_nodes in edt.compat2okay.items():
        if okay_nodes:
            out_define(f"DT_COMPAT_HAS_OKAY_{str2ident(compat)}", 1)

    out_comment('Macros for status "okay" instances of each compatible\n')
    for macro, value in n_okay_macros.items():
        out_define(macro, value)
    for macro, value in for_each_macros.items():
        out_define(macro, value)

    out_comment('Bus information for status "okay" nodes of each compatible\n')
    for compat, buses in compat2buses.items():
        for bus in buses:
            out_define(
                f"DT_COMPAT_{str2ident(compat)}_BUS_{str2ident(bus)}", 1)

def str2ident(s):
    # Converts 's' to a form suitable for (part of) an identifier

    return re.sub('[-,.@/+]', '_', s.lower())


def list2init(l):
    # Converts 'l', a Python list (or iterable), to a C array initializer

    return "{" + ", ".join(l) + "}"


def out_dt_define(macro, val, width=None, deprecation_msg=None):
    # Writes "#define DT_<macro> <val>" to the header file
    #
    # The macro will be left-justified to 'width' characters if that
    # is specified, and the value will follow immediately after in
    # that case. Otherwise, this function decides how to add
    # whitespace between 'macro' and 'val'.
    #
    # If a 'deprecation_msg' string is passed, the generated identifiers will
    # generate a warning if used, via __WARN(<deprecation_msg>)).
    #
    # Returns the full generated macro for 'macro', with leading "DT_".
    ret = "DT_" + macro
    out_define(ret, val, width=width, deprecation_msg=deprecation_msg)
    return ret


def out_define(macro, val, width=None, deprecation_msg=None):
    # Helper for out_dt_define(). Outputs "#define <macro> <val>",
    # adds a deprecation message if given, and allocates whitespace
    # unless told not to.

    warn = fr' __WARN("{deprecation_msg}")' if deprecation_msg else ""

    if width:
        s = f"#define {macro.ljust(width)}{warn} {val}"
    else:
        s = f"#define {macro}{warn} {val}"

    print(s, file=header_file)


def out_comment(s, blank_before=True):
    # Writes 's' as a comment to the header and configuration file. 's' is
    # allowed to have multiple lines. blank_before=True adds a blank line
    # before the comment.

    if blank_before:
        print(file=header_file)

    if "\n" in s:
        # Format multi-line comments like
        #
        #   /*
        #    * first line
        #    * second line
        #    *
        #    * empty line before this line
        #    */
        res = ["/*"]
        for line in s.splitlines():
            # Avoid an extra space after '*' for empty lines. They turn red in
            # Vim if space error checking is on, which is annoying.
            res.append(" *" if not line.strip() else " * " + line)
        res.append(" */")
        print("\n".join(res), file=header_file)
    else:
        # Format single-line comments like
        #
        #   /* foo bar */
        print("/* " + s + " */", file=header_file)


def escape(s):
    # Backslash-escapes any double quotes and backslashes in 's'

    # \ must be escaped before " to avoid double escaping
    return s.replace("\\", "\\\\").replace('"', '\\"')


def quote_str(s):
    # Puts quotes around 's' and escapes any double quotes and
    # backslashes within it

    return f'"{escape(s)}"'


def write_pickled_edt(edt, out_file):
    # Writes the edt object in pickle format to out_file.

    with open(out_file, 'wb') as f:
        # Pickle protocol version 4 is the default as of Python 3.8
        # and was introduced in 3.4, so it is both available and
        # recommended on all versions of Python that Zephyr supports
        # (at time of writing, Python 3.6 was Zephyr's minimum
        # version, and 3.8 the most recent CPython release).
        #
        # Using a common protocol version here will hopefully avoid
        # reproducibility issues in different Python installations.
        pickle.dump(edt, f, protocol=4)


def err(s):
    raise Exception(s)


if __name__ == "__main__":
    main()