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[5.0] Fix off-by-one when initializing Data with discontiguous, underestimated Sequences #23253

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Merged
merged 1 commit into from
Mar 13, 2019
Merged

[5.0] Fix off-by-one when initializing Data with discontiguous, underestimated Sequences #23253

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10 changes: 4 additions & 6 deletions stdlib/public/SDK/Foundation/Data.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -2084,9 +2084,8 @@ public struct Data : ReferenceConvertible, Equatable, Hashable, RandomAccessColl
// ... and append the rest byte-wise, buffering through an InlineData.
var buffer = InlineData()
while let element = iter.next() {
if buffer.count < buffer.capacity {
buffer.append(byte: element)
} else {
buffer.append(byte: element)
if buffer.count == buffer.capacity {
buffer.withUnsafeBytes { _representation.append(contentsOf: $0) }
buffer.count = 0
}
Expand Down Expand Up @@ -2378,9 +2377,8 @@ public struct Data : ReferenceConvertible, Equatable, Hashable, RandomAccessColl
// ... and append the rest byte-wise, buffering through an InlineData.
var buffer = InlineData()
while let element = iter.next() {
if buffer.count < buffer.capacity {
buffer.append(byte: element)
} else {
buffer.append(byte: element)
if buffer.count == buffer.capacity {
buffer.withUnsafeBytes { _representation.append(contentsOf: $0) }
buffer.count = 0
}
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14 changes: 10 additions & 4 deletions test/stdlib/TestData.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -1198,10 +1198,13 @@ class TestData : TestDataSuper {

// If we append a sequence of elements larger than a single InlineData, the internal append here should buffer.
// We want to make sure that buffering in this way does not accidentally drop trailing elements on the floor.
d.append(contentsOf: 0x03...0x17)
d.append(contentsOf: 0x03...0x2F)
expectEqual(Data([0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17]), d)
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F,
0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F]), d)
}

// This test is like test_appendingNonContiguousSequence_exactCount but uses a sequence which reports 0 for its `.underestimatedCount`.
Expand All @@ -1220,10 +1223,13 @@ class TestData : TestDataSuper {

// If we append a sequence of elements larger than a single InlineData, the internal append here should buffer.
// We want to make sure that buffering in this way does not accidentally drop trailing elements on the floor.
d.append(contentsOf: (0x03...0x17).makeIterator()) // `.makeIterator()` produces a sequence whose `.underestimatedCount` is 0.
d.append(contentsOf: (0x03...0x2F).makeIterator()) // `.makeIterator()` produces a sequence whose `.underestimatedCount` is 0.
expectEqual(Data([0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17]), d)
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F,
0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F]), d)
}

func test_sequenceInitializers() {
Expand Down