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Remove Sendable from AsyncBufferedByteIterator #220

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Merged
merged 1 commit into from
Oct 20, 2022
Merged

Remove Sendable from AsyncBufferedByteIterator #220

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29 changes: 7 additions & 22 deletions Sources/AsyncAlgorithms/AsyncBufferedByteIterator.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,7 @@
/// }
///
///
public struct AsyncBufferedByteIterator: AsyncIteratorProtocol, Sendable {
public struct AsyncBufferedByteIterator: AsyncIteratorProtocol {
public typealias Element = UInt8
@usableFromInline var buffer: _AsyncBytesBuffer

Expand All @@ -64,10 +64,13 @@ public struct AsyncBufferedByteIterator: AsyncIteratorProtocol, Sendable {
}
}

@available(*, unavailable)
extension AsyncBufferedByteIterator: Sendable { }

@frozen @usableFromInline
internal struct _AsyncBytesBuffer: @unchecked Sendable {
internal struct _AsyncBytesBuffer {
@usableFromInline
final class Storage: Sendable {
final class Storage {
fileprivate let buffer: UnsafeMutableRawBufferPointer

init(
Expand All @@ -85,7 +88,7 @@ internal struct _AsyncBytesBuffer: @unchecked Sendable {
}
}

@usableFromInline internal var storage: Storage
@usableFromInline internal let storage: Storage
@usableFromInline internal var nextPointer: UnsafeRawPointer
@usableFromInline internal var endPointer: UnsafeRawPointer

Expand All @@ -110,24 +113,6 @@ internal struct _AsyncBytesBuffer: @unchecked Sendable {
}
try Task.checkCancellation()
do {
// If two tasks have access to this iterator then the references on
// the storage will be non uniquely owned. This means that any reload
// must happen into its own fresh buffer. The consumption of those
// bytes between two tasks are inherently defined as potential
// duplication by the nature of sending that buffer across the two
// tasks - this means that the brief period in which they may be
// sharing non reloaded bytes is to be expected; basically in that
// edge case of making the iterator and sending that across to two
// places to iterate is asking for something bizzare and the answer
// should not be crash, but it definitely cannot be consistent.
//
// The unique ref check is here to prevent the potentials of a crashing
// scenario.
if !isKnownUniquelyReferenced(&storage) {
// The count is not mutated across invocations so the access is safe.
let capacity = storage.buffer.count
storage = Storage(capacity: capacity)
}
let readSize: Int = try await readFunction(storage.buffer)
if readSize == 0 {
finished = true
Expand Down