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Removes redundant buffer zeroing in StringGraphemeBreaking.swift by using `init(unsafeUninitializedCapacity:initializingWith:) #30132

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Merged
merged 1 commit into from
Mar 5, 2020
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Removes redundant buffer zeroing in StringGraphemeBreaking.swift by using `init(unsafeUninitializedCapacity:initializingWith:) #30132

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26 changes: 12 additions & 14 deletions stdlib/public/core/StringGraphemeBreaking.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -225,13 +225,12 @@ extension _StringGuts {

// TODO(String performance): Local small stack first, before making large
// array. Also, make a smaller initial array and grow over time.
var codeUnits = Array<UInt16>(repeating: 0, count: count)

codeUnits.withUnsafeMutableBufferPointer {
_cocoaStringCopyCharacters(
from: cocoa,
range: 0..<count,
into: $0.baseAddress._unsafelyUnwrappedUnchecked)
let codeUnits = Array<UInt16>(unsafeUninitializedCapacity: count) { buf, initializedCount in
_cocoaStringCopyCharacters(
from: cocoa,
range: 0..<count,
into: buf.baseAddress._unsafelyUnwrappedUnchecked)
initializedCount = count
}
return codeUnits.withUnsafeBufferPointer {
_measureCharacterStrideICU(of: $0, startingAt: i)
Expand Down Expand Up @@ -291,13 +290,12 @@ extension _StringGuts {

// TODO(String performance): Local small stack first, before making large
// array. Also, make a smaller initial array and grow over time.
var codeUnits = Array<UInt16>(repeating: 0, count: count)

codeUnits.withUnsafeMutableBufferPointer {
_cocoaStringCopyCharacters(
from: cocoa,
range: 0..<count,
into: $0.baseAddress._unsafelyUnwrappedUnchecked)
let codeUnits = Array<UInt16>(unsafeUninitializedCapacity: count) { buf, initializedCount in
_cocoaStringCopyCharacters(
from: cocoa,
range: 0..<count,
into: buf.baseAddress._unsafelyUnwrappedUnchecked)
initializedCount = count
}
return codeUnits.withUnsafeBufferPointer {
_measureCharacterStrideICU(of: $0, endingAt: i)
Expand Down