mirror of https://github.com/dahall/Vanara.git
105 lines
5.3 KiB
C#
105 lines
5.3 KiB
C#
using System.Collections;
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using System.Collections.Generic;
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namespace Vanara.PInvoke.Collections;
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/// <summary>Provides a generic enumerator over native memory.</summary>
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/// <typeparam name="T">The type of the element to extract from memory.</typeparam>
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/// <seealso cref="IEnumerator{T}"/>
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/// <seealso cref="IEnumerable{T}"/>
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public class NativeMemoryEnumerator<T> : UntypedNativeMemoryEnumerator, IEnumerator<T?>, IEnumerable<T?>
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{
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/// <summary>Initializes a new instance of the <see cref="NativeMemoryEnumerator{T}"/> class.</summary>
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/// <param name="ptr">A pointer to the starting address of a specified number of <typeparamref name="T"/> elements in memory.</param>
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/// <param name="length">The number of <typeparamref name="T"/> elements to be included in the enumeration.</param>
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/// <param name="prefixBytes">Bytes to skip before reading the first element.</param>
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/// <param name="allocatedBytes">If known, the total number of bytes allocated to the native memory in <paramref name="ptr"/>.</param>
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/// <exception cref="ArgumentOutOfRangeException">count</exception>
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/// <exception cref="InsufficientMemoryException"></exception>
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public NativeMemoryEnumerator(IntPtr ptr, int length, int prefixBytes = 0, SizeT allocatedBytes = default) : base(ptr, typeof(T), length, prefixBytes, allocatedBytes) { }
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/// <summary>Gets the element in the collection at the current position of the enumerator.</summary>
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public new T? Current => (T?)base.Current;
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/// <summary>Returns an enumerator that iterates through the collection.</summary>
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/// <returns>A <see cref="T:System.Collections.Generic.IEnumerator`1"/> that can be used to iterate through the collection.</returns>
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public new IEnumerator<T?> GetEnumerator() => this;
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}
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/// <summary>Provides an enumerator over native memory.</summary>
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/// <seealso cref="IEnumerator"/>
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/// <seealso cref="IEnumerable"/>
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public class UntypedNativeMemoryEnumerator : IEnumerator, IEnumerable
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{
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/// <summary>The number of allocated bytes.</summary>
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protected SizeT allocated;
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/// <summary>The number of elements in the enumeration.</summary>
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protected int count;
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/// <summary>The index of the current item. (-2) signifies an error. (-1) means MoveNext has not been called..</summary>
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protected int index = -1;
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/// <summary>The number of bytes to skip before reading the first element.</summary>
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protected int prefix;
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/// <summary>A pointer to the starting address of a specified number of <see cref="type"/> elements in memory.</summary>
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protected IntPtr ptr;
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/// <summary>The size of <see cref="type"/>.</summary>
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protected SizeT stSize;
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/// <summary>The type of the element to extract from memory.</summary>
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protected Type type;
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/// <summary>Initializes a new instance of the <see cref="NativeMemoryEnumerator{T}"/> class.</summary>
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/// <param name="ptr">A pointer to the starting address of a specified number of <paramref name="type"/> elements in memory.</param>
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/// <param name="type">The type of the element to extract from memory.</param>
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/// <param name="length">The number of <paramref name="type"/> elements to be included in the enumeration.</param>
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/// <param name="prefixBytes">Bytes to skip before reading the first element.</param>
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/// <param name="allocatedBytes">If known, the total number of bytes allocated to the native memory in <paramref name="ptr"/>.</param>
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/// <exception cref="ArgumentOutOfRangeException">count</exception>
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/// <exception cref="ArgumentNullException">type</exception>
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/// <exception cref="InsufficientMemoryException"></exception>
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public UntypedNativeMemoryEnumerator(IntPtr ptr, Type type, int length, int prefixBytes = 0, SizeT allocatedBytes = default)
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{
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if (length < 0 || ptr == IntPtr.Zero && length != 0)
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throw new ArgumentOutOfRangeException(nameof(length));
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if (type is null)
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throw new ArgumentNullException(nameof(type));
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this.type = type;
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this.ptr = ptr;
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count = length;
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prefix = prefixBytes;
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allocated = allocatedBytes == default ? (SizeT)uint.MaxValue : allocatedBytes;
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stSize = InteropExtensions.SizeOf(type);
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if (allocatedBytes > 0 && stSize * length + prefixBytes > allocatedBytes)
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throw new InsufficientMemoryException();
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}
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/// <summary>Gets the element in the collection at the current position of the enumerator.</summary>
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public virtual object? Current => index >= 0 && index < count
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? ptr.ToStructure(type, allocated, prefix + index * stSize, out _)
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: throw new ArgumentOutOfRangeException(nameof(index));
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/// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
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public virtual void Dispose() { }
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/// <summary>Returns an enumerator that iterates through a collection.</summary>
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/// <returns>An <see cref="T:System.Collections.IEnumerator"/> object that can be used to iterate through the collection.</returns>
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public IEnumerator GetEnumerator() => this;
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/// <summary>Advances the enumerator to the next element of the collection.</summary>
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/// <returns>
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/// true if the enumerator was successfully advanced to the next element; false if the enumerator has passed the end of the collection.
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/// </returns>
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public bool MoveNext()
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{
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if (++index >= count)
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index = -2;
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return index >= 0;
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}
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/// <summary>Sets the enumerator to its initial position, which is before the first element in the collection.</summary>
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public void Reset() => index = -1;
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} |