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[SR-11999] Substring.UTF8View does not provide an implementation for withContiguousStorageIfAvailable #54434

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Lukasa opened this issue Jan 9, 2020 · 3 comments
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[SR-11999] Substring.UTF8View does not provide an implementation for withContiguousStorageIfAvailable #54434

Lukasa opened this issue Jan 9, 2020 · 3 comments
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@milseman
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. standard library Area: Standard library umbrella

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@Lukasa
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Lukasa commented Jan 9, 2020

Previous ID SR-11999
Radar rdar://problem/58663804
Original Reporter @Lukasa
Type Bug
Status Resolved
Resolution Done
Additional Detail from JIRA
Votes 0
Component/s Standard Library
Labels Bug
Assignee @milseman
Priority Medium

md5: 0e12af38d6e41ffcc6bfa3efeeec376e

Issue Description:

While String is very good at providing fast access to its backing storage, Substring is less friendly. Try running the program below:

let x = "Hello, world!"

let basePointer = x.utf8.withContiguousStorageIfAvailable {
    UInt(bitPattern: $0.baseAddress!)
}

let slicePointer = x[...].utf8.withContiguousStorageIfAvailable {
    UInt(bitPattern: $0.baseAddress!)
}

if let ptr = basePointer {
    print("✅ String has fast pointer to storage: \(ptr)")
} else {
    print("⚠️  String has no fast pointer to storage")
}

if let ptr = slicePointer {
    print("✅ Substring has fast pointer to storage: \(ptr)")
} else {
    print("⚠️  Substring has no fast pointer to storage")
}

I would expect the output to be:

✅ String has fast pointer to storage: 140732689800216
✅ Substring has fast pointer to storage: 140732689800216

But instead I get

✅ String has fast pointer to storage: 140732689800216
⚠️  Substring has no fast pointer to storage
@Lukasa
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Lukasa commented Jan 9, 2020

Patch available in #29094

@swift-ci
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Comment by Kyle Macomber (JIRA)

@swift-ci create

@milseman
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Mannequin

milseman mannequin commented Jan 22, 2020

Great work @Lukasa!

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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@milseman milseman

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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. standard library Area: Standard library umbrella
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@Lukasa @swift-ci