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Diffstat (limited to 'src/mscorlib/shared/System/ReadOnlySpan.cs')
| -rw-r--r-- | src/mscorlib/shared/System/ReadOnlySpan.cs | 323 |
1 files changed, 323 insertions, 0 deletions
diff --git a/src/mscorlib/shared/System/ReadOnlySpan.cs b/src/mscorlib/shared/System/ReadOnlySpan.cs new file mode 100644 index 0000000000..8ec431f6fb --- /dev/null +++ b/src/mscorlib/shared/System/ReadOnlySpan.cs @@ -0,0 +1,323 @@ +// Licensed to the .NET Foundation under one or more agreements. +// The .NET Foundation licenses this file to you under the MIT license. +// See the LICENSE file in the project root for more information. + +using System.Diagnostics; +using System.Runtime.CompilerServices; +using EditorBrowsableState = System.ComponentModel.EditorBrowsableState; +using EditorBrowsableAttribute = System.ComponentModel.EditorBrowsableAttribute; + +#pragma warning disable 0809 //warning CS0809: Obsolete member 'Span<T>.Equals(object)' overrides non-obsolete member 'object.Equals(object)' + +namespace System +{ + /// <summary> + /// ReadOnlySpan represents a contiguous region of arbitrary memory. Unlike arrays, it can point to either managed + /// or native memory, or to memory allocated on the stack. It is type- and memory-safe. + /// </summary> + public struct ReadOnlySpan<T> + { + /// <summary>A byref or a native ptr.</summary> + private readonly ByReference<T> _pointer; + /// <summary>The number of elements this ReadOnlySpan contains.</summary> +#if PROJECTN + [Bound] +#endif + private readonly int _length; + + /// <summary> + /// Creates a new read-only span over the entirety of the target array. + /// </summary> + /// <param name="array">The target array.</param> + /// <exception cref="System.ArgumentNullException">Thrown when <paramref name="array"/> is a null + /// reference (Nothing in Visual Basic).</exception> + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public ReadOnlySpan(T[] array) + { + if (array == null) + ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array); + + _pointer = new ByReference<T>(ref Unsafe.As<byte, T>(ref array.GetRawSzArrayData())); + _length = array.Length; + } + + /// <summary> + /// Creates a new read-only span over the portion of the target array beginning + /// at 'start' index and covering the remainder of the array. + /// </summary> + /// <param name="array">The target array.</param> + /// <param name="start">The index at which to begin the read-only span.</param> + /// <exception cref="System.ArgumentNullException">Thrown when <paramref name="array"/> is a null + /// reference (Nothing in Visual Basic).</exception> + /// <exception cref="System.ArgumentOutOfRangeException"> + /// Thrown when the specified <paramref name="start"/> is not in the range (<0 or >=Length). + /// </exception> + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public ReadOnlySpan(T[] array, int start) + { + if (array == null) + ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array); + if ((uint)start > (uint)array.Length) + ThrowHelper.ThrowArgumentOutOfRangeException(); + + _pointer = new ByReference<T>(ref Unsafe.Add(ref Unsafe.As<byte, T>(ref array.GetRawSzArrayData()), start)); + _length = array.Length - start; + } + + /// <summary> + /// Creates a new read-only span over the portion of the target array beginning + /// at 'start' index and ending at 'end' index (exclusive). + /// </summary> + /// <param name="array">The target array.</param> + /// <param name="start">The index at which to begin the read-only span.</param> + /// <param name="length">The number of items in the read-only span.</param> + /// <exception cref="System.ArgumentNullException">Thrown when <paramref name="array"/> is a null + /// reference (Nothing in Visual Basic).</exception> + /// <exception cref="System.ArgumentOutOfRangeException"> + /// Thrown when the specified <paramref name="start"/> or end index is not in the range (<0 or >=Length). + /// </exception> + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public ReadOnlySpan(T[] array, int start, int length) + { + if (array == null) + ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array); + if ((uint)start > (uint)array.Length || (uint)length > (uint)(array.Length - start)) + ThrowHelper.ThrowArgumentOutOfRangeException(); + + _pointer = new ByReference<T>(ref Unsafe.Add(ref Unsafe.As<byte, T>(ref array.GetRawSzArrayData()), start)); + _length = length; + } + + /// <summary> + /// Creates a new read-only span over the target unmanaged buffer. Clearly this + /// is quite dangerous, because we are creating arbitrarily typed T's + /// out of a void*-typed block of memory. And the length is not checked. + /// But if this creation is correct, then all subsequent uses are correct. + /// </summary> + /// <param name="pointer">An unmanaged pointer to memory.</param> + /// <param name="length">The number of <typeparamref name="T"/> elements the memory contains.</param> + /// <exception cref="System.ArgumentException"> + /// Thrown when <typeparamref name="T"/> is reference type or contains pointers and hence cannot be stored in unmanaged memory. + /// </exception> + /// <exception cref="System.ArgumentOutOfRangeException"> + /// Thrown when the specified <paramref name="length"/> is negative. + /// </exception> + [CLSCompliant(false)] + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public unsafe ReadOnlySpan(void* pointer, int length) + { + if (RuntimeHelpers.IsReferenceOrContainsReferences<T>()) + ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(T)); + if (length < 0) + ThrowHelper.ThrowArgumentOutOfRangeException(); + + _pointer = new ByReference<T>(ref Unsafe.As<byte, T>(ref *(byte*)pointer)); + _length = length; + } + + /// <summary> + /// Create a new read-only span over a portion of a regular managed object. This can be useful + /// if part of a managed object represents a "fixed array." This is dangerous because neither the + /// <paramref name="length"/> is checked, nor <paramref name="obj"/> being null, nor the fact that + /// "rawPointer" actually lies within <paramref name="obj"/>. + /// </summary> + /// <param name="obj">The managed object that contains the data to span over.</param> + /// <param name="objectData">A reference to data within that object.</param> + /// <param name="length">The number of <typeparamref name="T"/> elements the memory contains.</param> + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public static ReadOnlySpan<T> DangerousCreate(object obj, ref T objectData, int length) => new ReadOnlySpan<T>(ref objectData, length); + + // Constructor for internal use only. + [MethodImpl(MethodImplOptions.AggressiveInlining)] + internal ReadOnlySpan(ref T ptr, int length) + { + Debug.Assert(length >= 0); + + _pointer = new ByReference<T>(ref ptr); + _length = length; + } + + /// <summary> + /// Returns a reference to the 0th element of the Span. If the Span is empty, returns a reference to the location where the 0th element + /// would have been stored. Such a reference can be used for pinning but must never be dereferenced. + /// </summary> + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public ref T DangerousGetPinnableReference() + { + return ref _pointer.Value; + } + + /// <summary> + /// The number of items in the read-only span. + /// </summary> + public int Length => _length; + + /// <summary> + /// Returns true if Length is 0. + /// </summary> + public bool IsEmpty => _length == 0; + + /// <summary> + /// Returns the specified element of the read-only span. + /// </summary> + /// <param name="index"></param> + /// <returns></returns> + /// <exception cref="System.IndexOutOfRangeException"> + /// Thrown when index less than 0 or index greater than or equal to Length + /// </exception> + public T this[int index] + { +#if PROJECTN + [BoundsChecking] + get + { + return Unsafe.Add(ref _pointer.Value, index); + } +#else + [MethodImpl(MethodImplOptions.AggressiveInlining)] + get + { + if ((uint)index >= (uint)_length) + ThrowHelper.ThrowIndexOutOfRangeException(); + return Unsafe.Add(ref _pointer.Value, index); + } +#endif + } + + /// <summary> + /// Copies the contents of this read-only span into destination span. If the source + /// and destinations overlap, this method behaves as if the original values in + /// a temporary location before the destination is overwritten. + /// + /// <param name="destination">The span to copy items into.</param> + /// <exception cref="System.ArgumentException"> + /// Thrown when the destination Span is shorter than the source Span. + /// </exception> + /// </summary> + public void CopyTo(Span<T> destination) + { + if (!TryCopyTo(destination)) + ThrowHelper.ThrowArgumentException_DestinationTooShort(); + } + + /// Copies the contents of this read-only span into destination span. If the source + /// and destinations overlap, this method behaves as if the original values in + /// a temporary location before the destination is overwritten. + /// </summary> + /// <returns>If the destination span is shorter than the source span, this method + /// return false and no data is written to the destination.</returns> + /// <param name="destination">The span to copy items into.</param> + public bool TryCopyTo(Span<T> destination) + { + if ((uint)_length > (uint)destination.Length) + return false; + + Span.CopyTo<T>(ref destination.DangerousGetPinnableReference(), ref _pointer.Value, _length); + return true; + } + + /// <summary> + /// Returns true if left and right point at the same memory and have the same length. Note that + /// this does *not* check to see if the *contents* are equal. + /// </summary> + public static bool operator ==(ReadOnlySpan<T> left, ReadOnlySpan<T> right) + { + return left._length == right._length && Unsafe.AreSame<T>(ref left._pointer.Value, ref right._pointer.Value); + } + + /// <summary> + /// Returns false if left and right point at the same memory and have the same length. Note that + /// this does *not* check to see if the *contents* are equal. + /// </summary> + public static bool operator !=(ReadOnlySpan<T> left, ReadOnlySpan<T> right) => !(left == right); + + /// <summary> + /// This method is not supported as spans cannot be boxed. To compare two spans, use operator==. + /// <exception cref="System.NotSupportedException"> + /// Always thrown by this method. + /// </exception> + /// </summary> + [Obsolete("Equals() on Span will always throw an exception. Use == instead.")] + [EditorBrowsable(EditorBrowsableState.Never)] + public override bool Equals(object obj) + { + throw new NotSupportedException(SR.NotSupported_CannotCallEqualsOnSpan); + } + + /// <summary> + /// This method is not supported as spans cannot be boxed. + /// <exception cref="System.NotSupportedException"> + /// Always thrown by this method. + /// </exception> + /// </summary> + [Obsolete("GetHashCode() on Span will always throw an exception.")] + [EditorBrowsable(EditorBrowsableState.Never)] + public override int GetHashCode() + { + throw new NotSupportedException(SR.NotSupported_CannotCallGetHashCodeOnSpan); + } + + /// <summary> + /// Defines an implicit conversion of an array to a <see cref="ReadOnlySpan{T}"/> + /// </summary> + public static implicit operator ReadOnlySpan<T>(T[] array) => new ReadOnlySpan<T>(array); + + /// <summary> + /// Defines an implicit conversion of a <see cref="ArraySegment{T}"/> to a <see cref="ReadOnlySpan{T}"/> + /// </summary> + public static implicit operator ReadOnlySpan<T>(ArraySegment<T> arraySegment) => new ReadOnlySpan<T>(arraySegment.Array, arraySegment.Offset, arraySegment.Count); + + /// <summary> + /// Forms a slice out of the given read-only span, beginning at 'start'. + /// </summary> + /// <param name="start">The index at which to begin this slice.</param> + /// <exception cref="System.ArgumentOutOfRangeException"> + /// Thrown when the specified <paramref name="start"/> index is not in range (<0 or >=Length). + /// </exception> + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public ReadOnlySpan<T> Slice(int start) + { + if ((uint)start > (uint)_length) + ThrowHelper.ThrowArgumentOutOfRangeException(); + + return new ReadOnlySpan<T>(ref Unsafe.Add(ref _pointer.Value, start), _length - start); + } + + /// <summary> + /// Forms a slice out of the given read-only span, beginning at 'start', of given length + /// </summary> + /// <param name="start">The index at which to begin this slice.</param> + /// <param name="length">The desired length for the slice (exclusive).</param> + /// <exception cref="System.ArgumentOutOfRangeException"> + /// Thrown when the specified <paramref name="start"/> or end index is not in range (<0 or >=Length). + /// </exception> + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public ReadOnlySpan<T> Slice(int start, int length) + { + if ((uint)start > (uint)_length || (uint)length > (uint)(_length - start)) + ThrowHelper.ThrowArgumentOutOfRangeException(); + + return new ReadOnlySpan<T>(ref Unsafe.Add(ref _pointer.Value, start), length); + } + + /// <summary> + /// Copies the contents of this read-only span into a new array. This heap + /// allocates, so should generally be avoided, however it is sometimes + /// necessary to bridge the gap with APIs written in terms of arrays. + /// </summary> + public T[] ToArray() + { + if (_length == 0) + return Array.Empty<T>(); + + var destination = new T[_length]; + Span.CopyTo<T>(ref Unsafe.As<byte, T>(ref destination.GetRawSzArrayData()), ref _pointer.Value, _length); + return destination; + } + + /// <summary> + /// Returns a 0-length read-only span whose base is the null pointer. + /// </summary> + public static ReadOnlySpan<T> Empty => default(ReadOnlySpan<T>); + } +} |