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[SR-6475] String needs a method to directly access either the ascii or unicode backing storage (compatible with cocoa storage too) #3780

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phausler opened this issue Nov 25, 2017 · 4 comments
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[SR-6475] String needs a method to directly access either the ascii or unicode backing storage (compatible with cocoa storage too) #3780

phausler opened this issue Nov 25, 2017 · 4 comments
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@milseman
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bug Foundation Standard Library

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@phausler
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Previous ID SR-6475
Radar None
Original Reporter @phausler
Type Bug
Status Resolved
Resolution Done
Additional Detail from JIRA
Votes 0
Component/s Foundation, Standard Library
Labels Bug
Assignee @milseman
Priority Medium

md5: 160572b7782ac20bbfdcd43f71047213

Issue Description:

This implementation of conversion from String to Data is in some cases 900x faster by taking advantage of fast paths. Ideally we should not drop performance like this on the floor and offer fast access to the appropriate backing storage. (note this is just a draft/toy version of what it should be but the concept should be implemented as API or SPI).

See the example at: https://gist.github.com/phausler/c6178bc9b0764f51d3ac182a293cede5
@phausler
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benchmarking this shows performance gains for many common usage patterns and no regression for non-common usage patterns.

@belkadan
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@milseman, is this already tracked somewhere?

@milseman
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Mannequin

milseman mannequin commented Dec 5, 2017

I don't think so.

For reference, the (highly in flux) _StringGuts branch is exploring things like an internal `withMutableASCIIStorage` or `withMutableUTF16Storage` call backs. Those currently (because they're for mutation) necessitate conversion to native storage of the appropriate width, but we could also have a read-only view that would work for any contiguous String, whether native Swift or from Cocoa.

@milseman
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Mannequin

milseman mannequin commented Apr 10, 2019

https://github.com/apple/swift-evolution/blob/master/proposals/0247-contiguous-strings.md

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@shahmishal shahmishal transferred this issue from apple/swift May 5, 2022
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@phausler @belkadan