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1#!/usr/bin/env python
2
3# Copyright (c) 2016 Google Inc.
4#
5# Licensed under the Apache License, Version 2.0 (the "License");
6# you may not use this file except in compliance with the License.
7# You may obtain a copy of the License at
8#
9#     http://www.apache.org/licenses/LICENSE-2.0
10#
11# Unless required by applicable law or agreed to in writing, software
12# distributed under the License is distributed on an "AS IS" BASIS,
13# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14# See the License for the specific language governing permissions and
15# limitations under the License.
16
17# Updates an output file with version info unless the new content is the same
18# as the existing content.
19#
20# Args: <spirv-tools_dir> <output-file>
21#
22# The output file will contain a line of text consisting of two C source syntax
23# string literals separated by a comma:
24#  - The software version deduced from the CHANGES file in the given directory.
25#  - A longer string with the project name, the software version number, and
26#    git commit information for the directory.  The commit information
27#    is the output of "git describe" if that succeeds, or "git rev-parse HEAD"
28#    if that succeeds, or otherwise a message containing the phrase
29#    "unknown hash".
30# The string contents are escaped as necessary.
31
32import datetime
33import errno
34import os
35import os.path
36import re
37import subprocess
38import sys
39import time
40
41
42def mkdir_p(directory):
43    """Make the directory, and all its ancestors as required.  Any of the
44    directories are allowed to already exist."""
45
46    if directory == "":
47        # We're being asked to make the current directory.
48        return
49
50    try:
51        os.makedirs(directory)
52    except OSError as e:
53        if e.errno == errno.EEXIST and os.path.isdir(directory):
54            pass
55        else:
56            raise
57
58
59def command_output(cmd, directory):
60    """Runs a command in a directory and returns its standard output stream.
61
62    Captures the standard error stream.
63
64    Raises a RuntimeError if the command fails to launch or otherwise fails.
65    """
66    p = subprocess.Popen(cmd,
67                         cwd=directory,
68                         stdout=subprocess.PIPE,
69                         stderr=subprocess.PIPE)
70    (stdout, _) = p.communicate()
71    if p.returncode != 0:
72        raise RuntimeError('Failed to run %s in %s' % (cmd, directory))
73    return stdout
74
75
76def deduce_software_version(directory):
77    """Returns a software version number parsed from the CHANGES file
78    in the given directory.
79
80    The CHANGES file describes most recent versions first.
81    """
82
83    # Match the first well-formed version-and-date line.
84    # Allow trailing whitespace in the checked-out source code has
85    # unexpected carriage returns on a linefeed-only system such as
86    # Linux.
87    pattern = re.compile(r'^(v\d+\.\d+(-dev)?) \d\d\d\d-\d\d-\d\d\s*$')
88    changes_file = os.path.join(directory, 'CHANGES')
89    with open(changes_file, mode='r') as f:
90        for line in f.readlines():
91            match = pattern.match(line)
92            if match:
93                return match.group(1)
94    raise Exception('No version number found in {}'.format(changes_file))
95
96
97def describe(directory):
98    """Returns a string describing the current Git HEAD version as descriptively
99    as possible.
100
101    Runs 'git describe', or alternately 'git rev-parse HEAD', in directory.  If
102    successful, returns the output; otherwise returns 'unknown hash, <date>'."""
103    try:
104        # decode() is needed here for Python3 compatibility. In Python2,
105        # str and bytes are the same type, but not in Python3.
106        # Popen.communicate() returns a bytes instance, which needs to be
107        # decoded into text data first in Python3. And this decode() won't
108        # hurt Python2.
109        return command_output(['git', 'describe'], directory).rstrip().decode()
110    except:
111        try:
112            return command_output(
113                ['git', 'rev-parse', 'HEAD'], directory).rstrip().decode()
114        except:
115            # This is the fallback case where git gives us no information,
116            # e.g. because the source tree might not be in a git tree.
117            # In this case, usually use a timestamp.  However, to ensure
118            # reproducible builds, allow the builder to override the wall
119            # clock time with environment variable SOURCE_DATE_EPOCH
120            # containing a (presumably) fixed timestamp.
121            timestamp = int(os.environ.get('SOURCE_DATE_EPOCH', time.time()))
122            formatted = datetime.datetime.utcfromtimestamp(timestamp).isoformat()
123            return 'unknown hash, {}'.format(formatted)
124
125
126def main():
127    if len(sys.argv) != 3:
128        print('usage: {} <spirv-tools-dir> <output-file>'.format(sys.argv[0]))
129        sys.exit(1)
130
131    output_file = sys.argv[2]
132    mkdir_p(os.path.dirname(output_file))
133
134    software_version = deduce_software_version(sys.argv[1])
135    new_content = '"{}", "SPIRV-Tools {} {}"\n'.format(
136        software_version, software_version,
137        describe(sys.argv[1]).replace('"', '\\"'))
138
139    if os.path.isfile(output_file):
140        with open(output_file, 'r') as f:
141            if new_content == f.read():
142                return
143
144    with open(output_file, 'w') as f:
145        f.write(new_content)
146
147if __name__ == '__main__':
148    main()
149