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Simplified Position API #1990

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Dec 20, 2017
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Simplified Position API #1990

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12 changes: 6 additions & 6 deletions samples/LowAllocationWebServer/LowAllocationWebServerLibrary/BufferSequence.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -55,9 +55,9 @@ public bool TryGet(ref Position position, out Memory<byte> item, bool advance =
return false;
}

var sequence = position.GetItem<BufferSequence>();
item = sequence.Memory.Slice(0, sequence._written);
if (advance) { position = Position.Create(sequence._next); }
var (buffer, index) = position.Get<BufferSequence>();
item = buffer.Memory.Slice(index, buffer._written - index);
if (advance) { position = Position.Create(buffer._next); }
return true;
}

Expand All @@ -69,9 +69,9 @@ public bool TryGet(ref Position position, out ReadOnlyMemory<byte> item, bool ad
return false;
}

var sequence = position.GetItem<BufferSequence>();
item = sequence.WrittenMemory;
if (advance) { position = Position.Create(sequence._next); }
var (buffer, index) = position.Get<BufferSequence>();
item = buffer.WrittenMemory.Slice(index);
if (advance) { position = Position.Create(buffer._next); }
return true;
}

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6 changes: 3 additions & 3 deletions src/System.Buffers.Experimental/System/Buffers/Sequences/MemoryList.cs
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Expand Up @@ -79,9 +79,9 @@ public bool TryGet(ref Position position, out Memory<byte> item, bool advance =
return false;
}

var sequence = position.GetItem<MemoryList>();
item = sequence._data;
if (advance) { position = Position.Create(sequence._next); }
var (list, index) = position.Get<MemoryList>();
item = list._data.Slice(index);
if (advance) { position = Position.Create(list._next); }
return true;
}

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18 changes: 9 additions & 9 deletions src/System.Buffers.Experimental/System/Buffers/Sequences/ReadOnlyBytes.cs
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Expand Up @@ -140,8 +140,8 @@ public ReadOnlyBytes Slice(Position position)
switch (kind)
{
case Type.Array:
var array = position.GetItem<byte[]>();
return new ReadOnlyBytes(array, position.Index, array.Length - position.Index);
var (array, index) = position.Get<byte[]>();
return new ReadOnlyBytes(array, index, array.Length - index);
case Type.MemoryList:
return Slice(position, Position.Create((IMemoryList<byte>)_end, _endIndex));
default: throw new NotImplementedException();
Expand All @@ -154,12 +154,12 @@ public ReadOnlyBytes Slice(Position start, Position end)
switch (kind)
{
case Type.Array:
var startArray = start.GetItem<byte[]>();
return new ReadOnlyBytes(startArray, start.Index, end.Index - start.Index);
var (array, index) = start.Get<byte[]>();
return new ReadOnlyBytes(array, index, (int)end - index);
case Type.MemoryList:
var startList = start.GetItem<IMemoryList<byte>>();
var endList = end.GetItem<IMemoryList<byte>>();
return new ReadOnlyBytes(startList, start.Index, endList, end.Index);
var (startList, startIndex) = start.Get<IMemoryList<byte>>();
var (endList, endIndex) = end.Get<IMemoryList<byte>>();
return new ReadOnlyBytes(startList, startIndex, endList, endIndex);
default:
throw new NotImplementedException();
}
Expand Down Expand Up @@ -281,8 +281,8 @@ public bool TryGet(ref Position position, out ReadOnlyMemory<byte> item, bool ad
var array = _start as byte[];
if (array != null)
{
var start = position.Index;
var length = _endIndex - position.Index;
var start = (int)position;
var length = _endIndex - (int)position;
item = new ReadOnlyMemory<byte>(array, start, length);
if (advance) position = default;
return true;
Expand Down
18 changes: 9 additions & 9 deletions src/System.Buffers.Experimental/System/Buffers/Sequences/ReadWriteBytes.cs
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Expand Up @@ -136,8 +136,8 @@ public ReadWriteBytes Slice(Position position)
switch (kind)
{
case Type.Array:
var array = position.GetItem<byte[]>();
return new ReadWriteBytes(array, position.Index, array.Length - position.Index);
var (array, index) = position.Get<byte[]>();
return new ReadWriteBytes(array, index, array.Length - index);
case Type.MemoryList:
return Slice(position, Position.Create((IMemoryList<byte>)_end, _endIndex));
default: throw new NotImplementedException();
Expand All @@ -150,12 +150,12 @@ public ReadWriteBytes Slice(Position start, Position end)
switch (kind)
{
case Type.Array:
var startArray = start.GetItem<byte[]>();
return new ReadWriteBytes(startArray, start.Index, end.Index - start.Index);
var (array, index) = start.Get<byte[]>();
return new ReadWriteBytes(array, index, (int)end - index);
case Type.MemoryList:
var startList = start.GetItem<IMemoryList<byte>>();
var endList = end.GetItem<IMemoryList<byte>>();
return new ReadWriteBytes(startList, start.Index, endList, end.Index);
var (startList, startIndex) = start.Get<IMemoryList<byte>>();
var (endList, endIndex) = end.Get<IMemoryList<byte>>();
return new ReadWriteBytes(startList, startIndex, endList, endIndex);
default:
throw new NotImplementedException();
}
Expand Down Expand Up @@ -278,8 +278,8 @@ public bool TryGet(ref Position position, out Memory<byte> item, bool advance =
var array = _start as byte[];
if (array != null)
{
var start = _startIndex + position.Index;
var length = _endIndex - _startIndex - position.Index;
var start = _startIndex + (int)position;
var length = _endIndex - _startIndex - (int)position;
item = new Memory<byte>(array, start, length);
if (advance) position = default;
return true;
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17 changes: 5 additions & 12 deletions src/System.Buffers.Experimental/System/Buffers/Text/BufferReader.cs
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Expand Up @@ -93,8 +93,8 @@ public bool TryReadBytes(out ReadOnlyBytes bytes, byte delimiter)
return false;
}

var startObj = range.Start.GetItem<object>();
var endObj = range.End.GetItem<object>();
var (startObj, startIndex) = range.Start.Get<object>();
var (endObj, endIndex) = range.End.Get<object>();
// TODO: this is a hack. Once we move this to System.Memory, we should remove
if (startObj == null || endObj == null)
{
Expand Down Expand Up @@ -302,14 +302,7 @@ public bool TryRead(out int value, bool littleEndian = false)

ReadOnlySpan<byte> Unread => _currentSpan.Slice(_currentSpanIndex);

Position Position
{
get {
var result = _currentSegmentPosition;
result += _currentSpanIndex;
return result;
}
}
Position Position =>_currentSegmentPosition + _currentSpanIndex;

Position? AdvanceToDelimiter(byte value)
{
Expand Down Expand Up @@ -358,10 +351,10 @@ Position Position
if(index != -1 && unread.Length - index < value.Length)
{
Span<byte> temp = stackalloc byte[value.Length];
int copied = Sequence.Copy(_bytes, _currentSegmentPosition + _currentSpanIndex + index, temp);
int copied = Sequence.Copy(_bytes, _currentSegmentPosition + (_currentSpanIndex + index), temp);
if (copied < value.Length) return null;

if (temp.SequenceEqual(value)) return _currentSegmentPosition + _currentSpanIndex + index;
if (temp.SequenceEqual(value)) return _currentSegmentPosition + (_currentSpanIndex + index);
else throw new NotImplementedException(); // need to check farther in this span
}

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28 changes: 16 additions & 12 deletions src/System.Collections.Sequences/System/Collections/Sequences/Position.cs
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Expand Up @@ -16,20 +16,19 @@ public static Position Create<T>(T item, int index = 0) where T : class

public static implicit operator Position(int index) => new Position(index, null);
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Do we need all these operators, Get<T>, and static Create method?
Can we just expose item and index and add a single public constructor that takes them?

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Also in all of the usages of Get<T> you never check that item is not null. Do we need to add some kind of validation that position was of an expected type?

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That's how it was originally, but you guys wanted to make it harder for people to get access to the object. Get/Create allow you to store an internal type in object to make it impossible to retrieve by third party code.

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You can always do Get<object> and get around it. And ReadOnlyBuffer stores publicly available types there. I don't think we can protect it from retrieving the item.

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Yes, but I wanted to change the check to only return the object if typeof(T) == _item.GetType().
I was planing to do it in a subsequent PR.


public static explicit operator int(Position position) => position.Index;

public int Index => _index;

[MethodImpl(MethodImplOptions.AggressiveInlining)]
public T GetItem<T>() => _item == null ? default : (T)_item;
public static explicit operator int(Position position) => position._index;

[MethodImpl(MethodImplOptions.AggressiveInlining)]
public (T item, int index) Get<T>() => (GetItem<T>(), (int)this);
public (T item, int index) Get<T>() {
var item = _item == null ? default : (T) _item;
return (item, _index);
}

public static bool operator ==(Position left, Position right) => left.Index == right.Index && left._item == right._item;
public static bool operator !=(Position left, Position right) => left.Index != right.Index || left._item != right._item;
public static bool operator ==(Position left, Position right) => left._index == right._index && left._item == right._item;
public static bool operator !=(Position left, Position right) => left._index != right._index || left._item != right._item;

public static Position operator +(Position position, int offset) => new Position(position.Index + offset, position._item);
public static Position operator +(Position value, int index)
=> new Position(value._index + index, value._item);

[EditorBrowsable(EditorBrowsableState.Never)]
public bool Equals(Position position) => this == position;
Expand All @@ -40,16 +39,21 @@ public override bool Equals(object obj) =>

[EditorBrowsable(EditorBrowsableState.Never)]
public override int GetHashCode() =>
Index.GetHashCode() ^ (_item == null ? 0 : _item.GetHashCode());
_index.GetHashCode() ^ (_item == null ? 0 : _item.GetHashCode());

[EditorBrowsable(EditorBrowsableState.Never)]
public override string ToString() =>
this==default ? "(default)" : _item == null ? $"{Index}" : $"{Index}, {_item}";
this==default ? "(default)" : _item == null ? $"{_index}" : $"{_index}, {_item}";

private Position(int index, object item)
{
_item = item;
_index = index;
}
private Position(int index)
{
_item = null;
_index = index;
}
}
}
2 changes: 1 addition & 1 deletion src/System.Collections.Sequences/System/Collections/Sequences/ResizableArray.cs
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Expand Up @@ -111,7 +111,7 @@ public bool TryGet(ref Position position, out T item, bool advance = true)
int index = (int)position;
if (index < _count) {
item = _array[index];
if (advance) { position += 1; }
if (advance) { position +=1; }
return true;
}

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4 changes: 2 additions & 2 deletions tests/System.Collections.Sequences.Tests/SampleCollections/LinkedContainer.cs
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Expand Up @@ -36,8 +36,8 @@ public bool TryGet(ref Position position, out T item, bool advance = true)
return false;
}

var node = position.GetItem<Node>();
if (node == null) {
var (node, index) = position.Get<Node>();
if (node == null || index != 0) {
item = default;
position = default;
return false;
Expand Down