Vanara/Core/Collections/NativeMemoryEnumerator.cs

105 lines
5.3 KiB
C#

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