|
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Collections.Generic;
using System.Diagnostics;
using System.Runtime.InteropServices;
using static System.Linq.Utilities;
namespace System.Linq
{
public static partial class Enumerable
{
private sealed partial class IEnumerableSelectIterator<TSource, TResult>
{
public override TResult[] ToArray()
{
SegmentedArrayBuilder<TResult>.ScratchBuffer scratch = default;
SegmentedArrayBuilder<TResult> builder = new(scratch);
Func<TSource, TResult> selector = _selector;
foreach (TSource item in _source)
{
builder.Add(selector(item));
}
TResult[] result = builder.ToArray();
builder.Dispose();
return result;
}
public override List<TResult> ToList()
{
var list = new List<TResult>();
Func<TSource, TResult> selector = _selector;
foreach (TSource item in _source)
{
list.Add(selector(item));
}
return list;
}
public override int GetCount(bool onlyIfCheap)
{
// In case someone uses Count() to force evaluation of
// the selector, run it provided `onlyIfCheap` is false.
if (onlyIfCheap)
{
return -1;
}
int count = 0;
foreach (TSource item in _source)
{
_selector(item);
checked
{
count++;
}
}
return count;
}
public override TResult? TryGetElementAt(int index, out bool found)
{
if (index >= 0)
{
IEnumerator<TSource> e = _source.GetEnumerator();
try
{
while (e.MoveNext())
{
if (index == 0)
{
found = true;
return _selector(e.Current);
}
index--;
}
}
finally
{
(e as IDisposable)?.Dispose();
}
}
found = false;
return default;
}
public override TResult? TryGetFirst(out bool found)
{
using IEnumerator<TSource> e = _source.GetEnumerator();
if (e.MoveNext())
{
found = true;
return _selector(e.Current);
}
found = false;
return default;
}
public override TResult? TryGetLast(out bool found)
{
using IEnumerator<TSource> e = _source.GetEnumerator();
if (e.MoveNext())
{
found = true;
TSource last = e.Current;
while (e.MoveNext())
{
last = e.Current;
}
return _selector(last);
}
found = false;
return default;
}
}
private sealed partial class ArraySelectIterator<TSource, TResult>
{
public override TResult[] ToArray()
{
// See assert in constructor.
// Since _source should never be empty, we don't check for 0/return Array.Empty.
TSource[] source = _source;
Debug.Assert(source.Length > 0);
var results = new TResult[source.Length];
Fill(source, results, _selector);
return results;
}
public override List<TResult> ToList()
{
TSource[] source = _source;
Debug.Assert(source.Length > 0);
var results = new List<TResult>(source.Length);
Fill(source, SetCountAndGetSpan(results, source.Length), _selector);
return results;
}
private static void Fill(ReadOnlySpan<TSource> source, Span<TResult> destination, Func<TSource, TResult> func)
{
for (int i = 0; i < destination.Length; i++)
{
destination[i] = func(source[i]);
}
}
public override int GetCount(bool onlyIfCheap)
{
// In case someone uses Count() to force evaluation of
// the selector, run it provided `onlyIfCheap` is false.
if (!onlyIfCheap)
{
foreach (TSource item in _source)
{
_selector(item);
}
}
return _source.Length;
}
public override Iterator<TResult>? Skip(int count)
{
Debug.Assert(count > 0);
if (count >= _source.Length)
{
return null;
}
return new IListSkipTakeSelectIterator<TSource, TResult>(_source, _selector, count, int.MaxValue);
}
public override Iterator<TResult> Take(int count)
{
Debug.Assert(count > 0);
return count >= _source.Length ?
this :
new IListSkipTakeSelectIterator<TSource, TResult>(_source, _selector, 0, count - 1);
}
public override TResult? TryGetElementAt(int index, out bool found)
{
TSource[] source = _source;
if ((uint)index < (uint)source.Length)
{
found = true;
return _selector(source[index]);
}
found = false;
return default;
}
public override TResult TryGetFirst(out bool found)
{
Debug.Assert(_source.Length > 0); // See assert in constructor
found = true;
return _selector(_source[0]);
}
public override TResult TryGetLast(out bool found)
{
Debug.Assert(_source.Length > 0); // See assert in constructor
found = true;
return _selector(_source[^1]);
}
}
private sealed partial class RangeSelectIterator<TResult> : Iterator<TResult>
{
private readonly int _start;
private readonly int _end;
private readonly Func<int, TResult> _selector;
public RangeSelectIterator(int start, int end, Func<int, TResult> selector)
{
Debug.Assert(start < end);
Debug.Assert((uint)(end - start) <= (uint)int.MaxValue);
Debug.Assert(selector is not null);
_start = start;
_end = end;
_selector = selector;
}
private protected override Iterator<TResult> Clone() =>
new RangeSelectIterator<TResult>(_start, _end, _selector);
public override bool MoveNext()
{
if (_state < 1 || _state == (_end - _start + 1))
{
Dispose();
return false;
}
int index = _state++ - 1;
Debug.Assert(_start < _end - index);
_current = _selector(_start + index);
return true;
}
public override IEnumerable<TResult2> Select<TResult2>(Func<TResult, TResult2> selector) =>
new RangeSelectIterator<TResult2>(_start, _end, CombineSelectors(_selector, selector));
public override TResult[] ToArray()
{
var results = new TResult[_end - _start];
Fill(results, _start, _selector);
return results;
}
public override List<TResult> ToList()
{
var results = new List<TResult>(_end - _start);
Fill(SetCountAndGetSpan(results, _end - _start), _start, _selector);
return results;
}
private static void Fill(Span<TResult> results, int start, Func<int, TResult> func)
{
for (int i = 0; i < results.Length; i++, start++)
{
results[i] = func(start);
}
}
public override int GetCount(bool onlyIfCheap)
{
// In case someone uses Count() to force evaluation of the selector,
// run it provided `onlyIfCheap` is false.
if (!onlyIfCheap)
{
for (int i = _start; i != _end; i++)
{
_selector(i);
}
}
return _end - _start;
}
public override Iterator<TResult>? Skip(int count)
{
Debug.Assert(count > 0);
if (count >= (_end - _start))
{
return null;
}
return new RangeSelectIterator<TResult>(_start + count, _end, _selector);
}
public override Iterator<TResult> Take(int count)
{
Debug.Assert(count > 0);
if (count >= (_end - _start))
{
return this;
}
return new RangeSelectIterator<TResult>(_start, _start + count, _selector);
}
public override TResult? TryGetElementAt(int index, out bool found)
{
if ((uint)index < (uint)(_end - _start))
{
found = true;
return _selector(_start + index);
}
found = false;
return default;
}
public override TResult TryGetFirst(out bool found)
{
Debug.Assert(_end > _start);
found = true;
return _selector(_start);
}
public override TResult TryGetLast(out bool found)
{
Debug.Assert(_end > _start);
found = true;
return _selector(_end - 1);
}
}
private sealed partial class ListSelectIterator<TSource, TResult>
{
public override TResult[] ToArray()
{
ReadOnlySpan<TSource> source = CollectionsMarshal.AsSpan(_source);
if (source.Length == 0)
{
return [];
}
var results = new TResult[source.Length];
Fill(source, results, _selector);
return results;
}
public override List<TResult> ToList()
{
ReadOnlySpan<TSource> source = CollectionsMarshal.AsSpan(_source);
var results = new List<TResult>(source.Length);
Fill(source, SetCountAndGetSpan(results, source.Length), _selector);
return results;
}
private static void Fill(ReadOnlySpan<TSource> source, Span<TResult> destination, Func<TSource, TResult> func)
{
for (int i = 0; i < destination.Length; i++)
{
destination[i] = func(source[i]);
}
}
public override int GetCount(bool onlyIfCheap)
{
// In case someone uses Count() to force evaluation of
// the selector, run it provided `onlyIfCheap` is false.
int count = _source.Count;
if (!onlyIfCheap)
{
for (int i = 0; i < count; i++)
{
_selector(_source[i]);
}
}
return count;
}
public override Iterator<TResult> Skip(int count)
{
Debug.Assert(count > 0);
return new IListSkipTakeSelectIterator<TSource, TResult>(_source, _selector, count, int.MaxValue);
}
public override Iterator<TResult> Take(int count)
{
Debug.Assert(count > 0);
return new IListSkipTakeSelectIterator<TSource, TResult>(_source, _selector, 0, count - 1);
}
public override TResult? TryGetElementAt(int index, out bool found)
{
if ((uint)index < (uint)_source.Count)
{
found = true;
return _selector(_source[index]);
}
found = false;
return default;
}
public override TResult? TryGetFirst(out bool found)
{
if (_source.Count != 0)
{
found = true;
return _selector(_source[0]);
}
found = false;
return default;
}
public override TResult? TryGetLast(out bool found)
{
int len = _source.Count;
if (len != 0)
{
found = true;
return _selector(_source[len - 1]);
}
found = false;
return default;
}
}
private sealed partial class IListSelectIterator<TSource, TResult>
{
public override TResult[] ToArray()
{
int count = _source.Count;
if (count == 0)
{
return [];
}
var results = new TResult[count];
Fill(_source, results, _selector);
return results;
}
public override List<TResult> ToList()
{
IList<TSource> source = _source;
int count = _source.Count;
var results = new List<TResult>(count);
Fill(source, SetCountAndGetSpan(results, count), _selector);
return results;
}
private static void Fill(IList<TSource> source, Span<TResult> results, Func<TSource, TResult> func)
{
for (int i = 0; i < results.Length; i++)
{
results[i] = func(source[i]);
}
}
public override int GetCount(bool onlyIfCheap)
{
// In case someone uses Count() to force evaluation of
// the selector, run it provided `onlyIfCheap` is false.
int count = _source.Count;
if (!onlyIfCheap)
{
for (int i = 0; i < count; i++)
{
_selector(_source[i]);
}
}
return count;
}
public override Iterator<TResult> Skip(int count)
{
Debug.Assert(count > 0);
return new IListSkipTakeSelectIterator<TSource, TResult>(_source, _selector, count, int.MaxValue);
}
public override Iterator<TResult> Take(int count)
{
Debug.Assert(count > 0);
return new IListSkipTakeSelectIterator<TSource, TResult>(_source, _selector, 0, count - 1);
}
public override TResult? TryGetElementAt(int index, out bool found)
{
if ((uint)index < (uint)_source.Count)
{
found = true;
return _selector(_source[index]);
}
found = false;
return default;
}
public override TResult? TryGetFirst(out bool found)
{
if (_source.Count != 0)
{
found = true;
return _selector(_source[0]);
}
found = false;
return default;
}
public override TResult? TryGetLast(out bool found)
{
int len = _source.Count;
if (len != 0)
{
found = true;
return _selector(_source[len - 1]);
}
found = false;
return default;
}
}
/// <summary>
/// An iterator that maps each item of an <see cref="Iterator{TSource}"/>.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TResult">The type of the mapped items.</typeparam>
private sealed class IteratorSelectIterator<TSource, TResult> : Iterator<TResult>
{
private readonly Iterator<TSource> _source;
private readonly Func<TSource, TResult> _selector;
private Iterator<TSource>? _enumerator;
public IteratorSelectIterator(Iterator<TSource> source, Func<TSource, TResult> selector)
{
Debug.Assert(source is not null);
Debug.Assert(selector is not null);
_source = source;
_selector = selector;
}
private protected override Iterator<TResult> Clone() =>
new IteratorSelectIterator<TSource, TResult>(_source, _selector);
public override bool MoveNext()
{
switch (_state)
{
case 1:
_enumerator = _source.GetEnumerator();
_state = 2;
goto case 2;
case 2:
Debug.Assert(_enumerator is not null);
if (_enumerator.MoveNext())
{
_current = _selector(_enumerator.Current);
return true;
}
Dispose();
break;
}
return false;
}
public override void Dispose()
{
if (_enumerator is not null)
{
_enumerator.Dispose();
_enumerator = null;
}
base.Dispose();
}
public override IEnumerable<TResult2> Select<TResult2>(Func<TResult, TResult2> selector) =>
new IteratorSelectIterator<TSource, TResult2>(_source, CombineSelectors(_selector, selector));
public override Iterator<TResult>? Skip(int count)
{
Debug.Assert(count > 0);
Iterator<TSource>? source = _source.Skip(count);
return source is null ? null : new IteratorSelectIterator<TSource, TResult>(source, _selector);
}
public override Iterator<TResult>? Take(int count)
{
Debug.Assert(count > 0);
Iterator<TSource>? source = _source.Take(count);
return source is null ? null : new IteratorSelectIterator<TSource, TResult>(source, _selector);
}
public override TResult? TryGetElementAt(int index, out bool found)
{
bool sourceFound;
TSource? input = _source.TryGetElementAt(index, out sourceFound);
found = sourceFound;
return sourceFound ? _selector(input!) : default!;
}
public override TResult? TryGetFirst(out bool found)
{
bool sourceFound;
TSource? input = _source.TryGetFirst(out sourceFound);
found = sourceFound;
return sourceFound ? _selector(input!) : default!;
}
public override TResult? TryGetLast(out bool found)
{
bool sourceFound;
TSource? input = _source.TryGetLast(out sourceFound);
found = sourceFound;
return sourceFound ? _selector(input!) : default!;
}
private TResult[] LazyToArray()
{
Debug.Assert(_source.GetCount(onlyIfCheap: true) == -1);
SegmentedArrayBuilder<TResult>.ScratchBuffer scratch = default;
SegmentedArrayBuilder<TResult> builder = new(scratch);
Func<TSource, TResult> selector = _selector;
foreach (TSource input in _source)
{
builder.Add(selector(input));
}
TResult[] result = builder.ToArray();
builder.Dispose();
return result;
}
private TResult[] PreallocatingToArray(int count)
{
Debug.Assert(count > 0);
Debug.Assert(count == _source.GetCount(onlyIfCheap: true));
TResult[] array = new TResult[count];
Fill(_source, array, _selector);
return array;
}
public override TResult[] ToArray()
{
int count = _source.GetCount(onlyIfCheap: true);
return count switch
{
-1 => LazyToArray(),
0 => [],
_ => PreallocatingToArray(count),
};
}
public override List<TResult> ToList()
{
int count = _source.GetCount(onlyIfCheap: true);
List<TResult> list;
switch (count)
{
case -1:
list = new List<TResult>();
foreach (TSource input in _source)
{
list.Add(_selector(input));
}
break;
case 0:
list = new List<TResult>();
break;
default:
list = new List<TResult>(count);
Fill(_source, SetCountAndGetSpan(list, count), _selector);
break;
}
return list;
}
private static void Fill(Iterator<TSource> source, Span<TResult> results, Func<TSource, TResult> func)
{
int index = 0;
foreach (TSource item in source)
{
results[index] = func(item);
++index;
}
Debug.Assert(index == results.Length, "All list elements were not initialized.");
}
public override int GetCount(bool onlyIfCheap)
{
if (!onlyIfCheap)
{
// In case someone uses Count() to force evaluation of
// the selector, run it provided `onlyIfCheap` is false.
int count = 0;
foreach (TSource item in _source)
{
_selector(item);
checked { count++; }
}
return count;
}
return _source.GetCount(onlyIfCheap);
}
}
/// <summary>
/// An iterator that maps each item of part of an <see cref="IList{TSource}"/>.
/// </summary>
/// <typeparam name="TSource">The type of the source list.</typeparam>
/// <typeparam name="TResult">The type of the mapped items.</typeparam>
[DebuggerDisplay("Count = {Count}")]
private sealed class IListSkipTakeSelectIterator<TSource, TResult> : Iterator<TResult>
{
private readonly IList<TSource> _source;
private readonly Func<TSource, TResult> _selector;
private readonly int _minIndexInclusive;
private readonly int _maxIndexInclusive;
public IListSkipTakeSelectIterator(IList<TSource> source, Func<TSource, TResult> selector, int minIndexInclusive, int maxIndexInclusive)
{
Debug.Assert(source is not null);
Debug.Assert(selector is not null);
Debug.Assert(minIndexInclusive >= 0);
Debug.Assert(minIndexInclusive <= maxIndexInclusive);
_source = source;
_selector = selector;
_minIndexInclusive = minIndexInclusive;
_maxIndexInclusive = maxIndexInclusive;
}
private protected override Iterator<TResult> Clone() =>
new IListSkipTakeSelectIterator<TSource, TResult>(_source, _selector, _minIndexInclusive, _maxIndexInclusive);
public override bool MoveNext()
{
// _state - 1 represents the zero-based index into the list.
// Having a separate field for the index would be more readable. However, we save it
// into _state with a bias to minimize field size of the iterator.
int index = _state - 1;
if ((uint)index <= (uint)(_maxIndexInclusive - _minIndexInclusive) && index < _source.Count - _minIndexInclusive)
{
_current = _selector(_source[_minIndexInclusive + index]);
++_state;
return true;
}
Dispose();
return false;
}
public override IEnumerable<TResult2> Select<TResult2>(Func<TResult, TResult2> selector) =>
new IListSkipTakeSelectIterator<TSource, TResult2>(_source, CombineSelectors(_selector, selector), _minIndexInclusive, _maxIndexInclusive);
public override Iterator<TResult>? Skip(int count)
{
Debug.Assert(count > 0);
int minIndex = _minIndexInclusive + count;
return (uint)minIndex > (uint)_maxIndexInclusive ? null : new IListSkipTakeSelectIterator<TSource, TResult>(_source, _selector, minIndex, _maxIndexInclusive);
}
public override Iterator<TResult> Take(int count)
{
Debug.Assert(count > 0);
int maxIndex = _minIndexInclusive + count - 1;
return (uint)maxIndex >= (uint)_maxIndexInclusive ? this : new IListSkipTakeSelectIterator<TSource, TResult>(_source, _selector, _minIndexInclusive, maxIndex);
}
public override TResult? TryGetElementAt(int index, out bool found)
{
if ((uint)index <= (uint)(_maxIndexInclusive - _minIndexInclusive) && index < _source.Count - _minIndexInclusive)
{
found = true;
return _selector(_source[_minIndexInclusive + index]);
}
found = false;
return default;
}
public override TResult? TryGetFirst(out bool found)
{
if (_source.Count > _minIndexInclusive)
{
found = true;
return _selector(_source[_minIndexInclusive]);
}
found = false;
return default;
}
public override TResult? TryGetLast(out bool found)
{
int lastIndex = _source.Count - 1;
if (lastIndex >= _minIndexInclusive)
{
found = true;
return _selector(_source[Math.Min(lastIndex, _maxIndexInclusive)]);
}
found = false;
return default;
}
private int Count
{
get
{
int count = _source.Count;
if (count <= _minIndexInclusive)
{
return 0;
}
return Math.Min(count - 1, _maxIndexInclusive) - _minIndexInclusive + 1;
}
}
public override TResult[] ToArray()
{
int count = Count;
if (count == 0)
{
return [];
}
TResult[] array = new TResult[count];
Fill(_source, array, _selector, _minIndexInclusive);
return array;
}
public override List<TResult> ToList()
{
int count = Count;
if (count == 0)
{
return new List<TResult>();
}
List<TResult> list = new List<TResult>(count);
Fill(_source, SetCountAndGetSpan(list, count), _selector, _minIndexInclusive);
return list;
}
private static void Fill(IList<TSource> source, Span<TResult> destination, Func<TSource, TResult> func, int sourceIndex)
{
for (int i = 0; i < destination.Length; i++, sourceIndex++)
{
destination[i] = func(source[sourceIndex]);
}
}
public override int GetCount(bool onlyIfCheap)
{
// In case someone uses Count() to force evaluation of
// the selector, run it provided `onlyIfCheap` is false.
int count = Count;
if (!onlyIfCheap)
{
int end = _minIndexInclusive + count;
for (int i = _minIndexInclusive; i != end; ++i)
{
_selector(_source[i]);
}
}
return count;
}
}
}
}
|