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c5a677da9e
The update_file.py tool now preserves the end of line of the updated file. Fix the "make regen-frozen" command: it no longer changes the end of line of PCbuild/ files on Unix. Git changes the end of line depending on the platform.
64 lines
1.9 KiB
Python
64 lines
1.9 KiB
Python
"""
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A script that replaces an old file with a new one, only if the contents
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actually changed. If not, the new file is simply deleted.
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This avoids wholesale rebuilds when a code (re)generation phase does not
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actually change the in-tree generated code.
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"""
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import contextlib
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import os
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import os.path
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import sys
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@contextlib.contextmanager
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def updating_file_with_tmpfile(filename, tmpfile=None):
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"""A context manager for updating a file via a temp file.
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The context manager provides two open files: the source file open
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for reading, and the temp file, open for writing.
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Upon exiting: both files are closed, and the source file is replaced
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with the temp file.
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"""
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# XXX Optionally use tempfile.TemporaryFile?
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if not tmpfile:
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tmpfile = filename + '.tmp'
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elif os.path.isdir(tmpfile):
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tmpfile = os.path.join(tmpfile, filename + '.tmp')
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with open(filename, 'rb') as infile:
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line = infile.readline()
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if line.endswith(b'\r\n'):
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newline = "\r\n"
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elif line.endswith(b'\r'):
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newline = "\r"
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elif line.endswith(b'\n'):
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newline = "\n"
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else:
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raise ValueError(f"unknown end of line: {filename}: {line!a}")
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with open(tmpfile, 'w', newline=newline) as outfile:
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with open(filename) as infile:
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yield infile, outfile
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update_file_with_tmpfile(filename, tmpfile)
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def update_file_with_tmpfile(filename, tmpfile):
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with open(filename, 'rb') as f:
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old_contents = f.read()
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with open(tmpfile, 'rb') as f:
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new_contents = f.read()
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if old_contents != new_contents:
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os.replace(tmpfile, filename)
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else:
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os.unlink(tmpfile)
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if __name__ == '__main__':
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if len(sys.argv) != 3:
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print("Usage: %s <path to be updated> <path with new contents>" % (sys.argv[0],))
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sys.exit(1)
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update_file_with_tmpfile(sys.argv[1], sys.argv[2])
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