stream.hls_playlist: refactor M3U8Parser #4540
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- Generate a mapping of tags->callbacks on parser init once and cache mapping as class attribute (avoid parent class lookups) - Performance: look up tags in cached mapping in `parse_line()` - Re-order `parse_tag_...` methods by definition order of RFC 8216 - Add docstring to each `parse_tag_...` method with link to RFC 8216 - Add typing annotations to each `parse_tag_...` method - Fix minor typing issues in regards to optional URIs in Key and Media and update parse methods accordingly - Pass keywords to various named tuples instead of positional args
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and cache mapping as class attribute (avoid parent class lookups)
parse_line()parse_tag_...methods by definition order of RFC 8216parse_tag_...method with link to RFC 8216parse_tag_...methodand update parse methods accordingly
This improves the performance of the
M3U8Parser, as it doesn't have to generate a string with the name of supported tag methods for each tag anymore, and it can simply look up tags in a pre-generated mapping of tags->callbacks that get only built once after the first instantiation of the class. This is fully compatible withM3U8Parsersubclasses which override or add tag methods, and nothing has to be changed by those subclasses (tag method names stay the same). Subclasses have their own cache.One thing to note is that the parser doesn't call
tag.lower()anymore inparse_line(), which means that if for some reason an HLS playlist includes lowercase tag names or anything that doesn't match the exact case of the tag names, those invalid tags won't be recognized anymore, because tags are case sensitive.These changes will introduce a merge conflict with #4538.