create_buffer.py

#!/usr/bin/env python3

# Copyright 2018-2019 Google LLC
#
# This is part of the Google Cloud IoT Device SDK for Embedded C.
# It is licensed under the BSD 3-Clause license; you may not use this file
# except in compliance with the License.
#
# You may obtain a copy of the License at:
#  https://opensource.org/licenses/BSD-3-Clause
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import argparse
import os.path
import struct
from pprint import pprint

h_file_name = ""
c_file_name = ""

ROOTCA_LIST_LEN_MACRO = "IOTC_ROOTCA_LIST_BYTE_LENGTH"
PATTERN = "0x%02x"
NEWLINE = "\n"
INDENT = 4 * " "
PER_LINE = 16


def tabs_2_spaces(s):
    return s.replace("\t", "    ")


h_pro = tabs_2_spaces(
    """\
/* Copyright 2018-2019 Google LLC
 *
 * This is part of the Google Cloud IoT Device SDK for Embedded C.
 * It is licensed under the BSD 3-Clause license; you may not use this file
 * except in compliance with the License.
 *
 * You may obtain a copy of the License at:
 *  https://opensource.org/licenses/BSD-3-Clause
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
""")
h_guard_beg = tabs_2_spaces("#ifndef __%(name)s_H__\n#define __%(name)s_H__")
h_guard_end = tabs_2_spaces("#endif /* __%s_H__ */")
cpp_beg = tabs_2_spaces("#ifdef __cplusplus\nextern \"C\" {\n#endif")
cpp_end = tabs_2_spaces("#ifdef __cplusplus\n}\n#endif")

src_usage_msg = \
    """\
/* generated by create_buffer.py from a PEM file. Example:
 * ./create_buffer.py --file_name res/trusted_RootCA_certs/roots.pem
 *    --array_name iotc_RootCA_list --out_path src/libiotc/tls/certs --no-pretend
 *
 * The buffer is terminated with '\\n' for consistency with POSIX filesystem reads
 */
"""


def load_file(file_name):
    if not os.path.isfile(file_name):
        raise RuntimeError("There is no such file: [%s]!" % file_name)

    data = []

    with open(file_name, "rb") as f:
        byte = f.read(1)

        while byte:
            data.append(struct.unpack('B', byte)[0])
            byte = f.read(1)

    return data


def convert_to_c_array(data, array_name):
    out = "unsigned char %s[ %s ] = {" % (array_name, ROOTCA_LIST_LEN_MACRO)
    out += NEWLINE
    out += INDENT

    while data:
        head = data[0: PER_LINE]
        data = data[PER_LINE:]

        for byte in head[0: -1]:
            out += PATTERN % byte
            out += ", "

        out += PATTERN % head[-1]

        if data:
            out += ","
            out += NEWLINE
            out += INDENT

    out += " };"

    return out


def create_c_file(data, array_name):
    out = h_pro + "\n"
    out += cpp_beg + "\n\n"

    out += '#include "%s"' % (os.path.basename(h_file_name))
    out += "\n\n"

    out += src_usage_msg
    out += convert_to_c_array(data, array_name)
    out += "\n\n"
    out += cpp_end + "\n"

    return out


def create_h_file(data, array_name):
    out = h_pro + "\n\n"
    out += (h_guard_beg % {"name": array_name.upper()}) + "\n\n"
    out += cpp_beg + "\n\n"
    out += "#ifndef %s" % (ROOTCA_LIST_LEN_MACRO)
    out += "\n"
    out += "#define %s %d" % (ROOTCA_LIST_LEN_MACRO, len(data))
    out += "\n"
    out += "#endif /* %s */" % (ROOTCA_LIST_LEN_MACRO)
    out += "\n\n"
    out += "extern unsigned char %s[ %s ];\n\n" % (
        array_name, ROOTCA_LIST_LEN_MACRO)
    out += cpp_end + "\n\n"
    out += (h_guard_end % (array_name.upper())) + "\n"

    return out


def write_to_file(file_name, s):

    print("writing to: %s" % file_name)

    with open(file_name, "w") as f:
        f.write(s)


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description="libiotc buffer creator")
    parser.add_argument('--file_name', dest='file_name', type=str,
                        required='True', help='file name that is going to be converted')
    parser.add_argument('--out_path', dest='out_path',
                        type=str, help='output path')
    parser.add_argument('--array_name', dest='array_name', type=str,
                        required='True', help='array name that is going to be used as an output')
    parser.add_argument('--no-pretend', dest='no_pret', action='store_const', const=True,
                        default=False, help='disable printing to the console and enables writing to files')

    args = parser.parse_args()

    file_name = args.file_name
    array_name = args.array_name
    out_path = args.out_path

    if out_path:
        path = out_path
    else:
        path = os.path.join('.', 'src', 'libiotc')

    h_file_name = os.path.join(path, array_name + ".h")
    c_file_name = os.path.join(path, array_name + ".c")

    data = load_file(file_name)

    if args.no_pret:
        write_to_file(h_file_name, create_h_file(data, array_name))
        write_to_file(c_file_name, create_c_file(data, array_name))
    else:
        print((create_h_file(data, array_name)))
        print((create_c_file(data, array_name)))