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[stdlib] tolerate empty source buffers in UMRBP.copyMemory #41836

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Merged
merged 2 commits into from
Mar 16, 2022
Merged

[stdlib] tolerate empty source buffers in UMRBP.copyMemory #41836

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e40e0f7
[stdlib] improve UnsafeMutableRawBufferPointer.copyMemory
glessard Mar 16, 2022
cc60db7
[test] validate behaviour when copying from an empty buffer
glessard Mar 16, 2022
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4 changes: 3 additions & 1 deletion stdlib/public/core/UnsafeRawBufferPointer.swift.gyb
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Original file line number Diff line number Diff line change
Expand Up @@ -438,7 +438,9 @@ extension Unsafe${Mutable}RawBufferPointer {
public func copyMemory(from source: UnsafeRawBufferPointer) {
_debugPrecondition(source.count <= self.count,
"${Self}.copyMemory source has too many elements")
baseAddress?.copyMemory(from: source.baseAddress!, byteCount: source.count)
if let baseAddress = baseAddress, let sourceAddress = source.baseAddress {
baseAddress.copyMemory(from: sourceAddress, byteCount: source.count)
}
}

/// Copies from a collection of `UInt8` into this buffer's memory.
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24 changes: 24 additions & 0 deletions validation-test/stdlib/UnsafeBufferPointer.swift.gyb
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Expand Up @@ -179,6 +179,30 @@ ${SelfName}TestSuite.test("nilBaseAddress") {
expectEqualSequence([], emptyBuffer)
}

% if IsMutable:
${SelfName}TestSuite.test("copyFromEmptyBuffer") {
% if IsRaw:
var memory: UnsafeMutableRawPointer
let empty = UnsafeRawBufferPointer(start: nil, count: 0)
% else:
var memory: UnsafeMutablePointer<Float>
let empty = UnsafeBufferPointer<Float>(start: nil, count: 0)
% end

let count = 4
memory = allocateFor${Raw}Buffer(count: count)
defer { deallocateFor${Raw}Buffer(memory, count: count) }

let buffer = UnsafeMutable${Raw}BufferPointer(start: memory, count: count)

% if IsRaw:
buffer.copyMemory(from: empty)
% else:
_ = buffer.initialize(from: empty)
% end
}
% end

${SelfName}TestSuite.test("nonNilButEmpty") {
let emptyAllocated = UnsafeMutablePointer<Float>.allocate(capacity: 0)
defer { emptyAllocated.deallocate() }
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