Reduce string allocations in mimetype code #4440
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The code handling mimetypes was using strings.Split() to split the string and that allocates. We can use strings.IndexByte() to get an index and subslice instead. I also refactored some code to avoid duplicating mimetype split logic. The new internal/repository/mime package exists to avoid cycling imports. NOTE: The split logic is slightly different because a second / would be includes as part of the subtype now but as far as I can see from reading the spec (https://specifications.freedesktop.org/shared-mime-info-spec/shared-mime-info-spec-0.21.html) it should not be a problem as the format is "mainType/subType;weight" so there should not be any more separators.
andydotxyz
approved these changes
Dec 7, 2023
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Description:
The code handling mimetypes was using strings.Split() to split the string and that allocates. We can use strings.IndexByte() to get an index and subslice instead. I also refactored some code to avoid duplicating part of the logic.
The new internal/repository/mime package exists to avoid cyclic imports.
NOTE: The split logic is slightly different because a second / would be includes as part of the subtype now but as far as I can see from reading the spec (https://specifications.freedesktop.org/shared-mime-info-spec/shared-mime-info-spec-0.21.html) it should not be a problem as the format is "mainType/subType:weight" so there should not be any more separators, I think. I also did a ripgrep
cat /usr/share/mime/globs2 | rg "\d\d:\w+/.+/"on my local mime database and nothing contains a second slash.Checklist: