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[Foundation] Address exclusivity violation in Data #15823

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Merged
merged 1 commit into from
Apr 10, 2018
Merged

[Foundation] Address exclusivity violation in Data #15823

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13 changes: 11 additions & 2 deletions stdlib/public/SDK/Foundation/Data.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -1762,14 +1762,23 @@ public struct Data : ReferenceConvertible, Equatable, Hashable, RandomAccessColl
}

public struct Iterator : IteratorProtocol {
private let _data: Data
// Both _data and _endIdx should be 'let' rather than 'var'.
// They are 'var' so that the stored properties can be read
// independently of the other contents of the struct. This prevents
// an exclusivity violation when reading '_endIdx' and '_data'
// while simultaneously mutating '_buffer' with the call to
// withUnsafeMutablePointer(). Once we support accessing struct
// let properties independently we should make these variables
// 'let' again.

private var _data: Data
private var _buffer: (
UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8,
UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8,
UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8,
UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8)
private var _idx: Data.Index
private let _endIdx: Data.Index
private var _endIdx: Data.Index

fileprivate init(_ data: Data) {
_data = data
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