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CRC32 support was initially implemented in the C extension as a separate set of functions instead of integrating it with existing code from the beginning. Functions for calculating AccurateRip and CRC32 checksums were called separately in the source code, which resulted in loading the same audio file twice. For FLAC files this meant double overhead related to FLAC format decoding. Refactoring the legacy code in the C extension allowed to merge the duplicated code into a single function that calculates all checksums but only loads the audio file once, avoiding the extra overhead. This results in FLAC processing becoming nearly twice as fast as before. The improvement is negligible for WAV files. To adapt the code accuraterip_checksums() and copy_crc() are replaced with get_checksums() which in turn is called by functions in Rip module. Adaptation of _audio_test.py is straightforward: since there are no separate functions for calculating AccurateRip and CRC32 checksums anymore, it is sufficient to test the exceptions just once. Separate set of tests for CRC32 became redundant and was removed. Adaptation of checksums_test.py follows the path of least resistance. AccurateRip and CRC32 tests remain separate, they simply extract the relevant part of the triple returned by get_checksums() and verify that.
26 lines
1 KiB
Python
26 lines
1 KiB
Python
"""Functions for calculating checksums of audio files."""
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from typing import Tuple
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from arver.audio import _audio # type: ignore
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# pylint: disable=c-extension-no-member
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def get_checksums(path: str, track_no: int, total_tracks: int) -> Tuple[int, int, int]:
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"""
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Calculate AccurateRip and CRC32 checksums of specified file.
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Return a triple of checksums (v1, v2, crc32) as unsigned integers.
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This function supports WAV and FLAC files compliant with CDDA
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standard (16-bit stereo LPCM, 44100 Hz). Underlying C extension
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will raise TypeError for any other audio format, or OSError when
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libsndfile can't load audio samples from the file for any reason.
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The track_no and total_tracks arguments are used to recognize
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if the track is the first or the last one on CD. These two
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tracks are treated specially by AccurateRip checksum algorithm.
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ValueError is raised if the track numbers are not valid. These
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arguments don't matter for CRC32 calculation.
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"""
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return _audio.checksums(path, track_no, total_tracks)
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