GH-49720: [C++] Optimize base64_decode validation using lookup table#49748
Open
Reranko05 wants to merge 1 commit intoapache:mainfrom
Open
GH-49720: [C++] Optimize base64_decode validation using lookup table#49748Reranko05 wants to merge 1 commit intoapache:mainfrom
Reranko05 wants to merge 1 commit intoapache:mainfrom
Conversation
|
|
Reranko05
force-pushed
the
optimize-base64-lookup
branch
from
9c55ff0 to
e48fd5c
Compare
Contributor
Author
|
Hi @kou @dmitry-chirkov-dremio, this implements the lookup-table optimization we discussed in PR #49660 . |
This file contains hidden or 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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
Rationale for this change
The current implementation of
base64_decodevalidates characters usingstd::string::findfor each byte, which introduces unnecessary overhead due to repeated linear searches.This change replaces those lookups with a precomputed 256-entry lookup table, enabling constant-time validation and value lookup per character.
What changes are included in this PR?
kBase64Lookup) to map base64 characters to their corresponding valuesstd::string::findwith constant-time table lookup for character validationAre these changes tested?
Yes. Existing base64 decoding behavior remains unchanged and continues to pass all current tests. This change is a performance optimization and does not alter functional output.
Are there any user-facing changes?
No.
This change is internal and does not affect public APIs.
GitHub Issue: #49720