mirror of https://github.com/dahall/Vanara.git
Added SafeElementArray class to Core to handle BLOB types
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using System;
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using System.Collections;
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using System.Collections.Generic;
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using System.Linq;
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using System.Runtime.InteropServices;
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using Vanara.Extensions;
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namespace Vanara.InteropServices
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{
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/// <summary>
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/// A safe unmanaged array of structures allocated on the global heap with a prefix type (usually a uint or int) that determines the count of elements.
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/// </summary>
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public class SafeElementArray<TElem, TPrefix, TMem> : SafeMemoryHandle<TMem>, IEnumerable<TElem> where TMem : IMemoryMethods, new() where TElem : struct where TPrefix : IConvertible
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{
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private static int ElemSize = Marshal.SizeOf(typeof(TElem));
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private static int PrefixSize = Marshal.SizeOf(typeof(TPrefix));
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/// <summary>Initializes a new instance of the <see cref="SafeElementArray{TElem, TPrefix, TMem}"/> class.</summary>
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protected SafeElementArray() : this(0) { }
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/// <summary>Initializes a new instance of the <see cref="SafeElementArray"/> class and allocates <paramref name="byteCount"/> bytes.</summary>
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/// <param name="byteCount">The TElem count to allocate.</param>
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protected SafeElementArray(TPrefix elementCount) : this(Convert.ToInt32(elementCount)) { }
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/// <summary>Initializes a new instance of the <see cref="SafeElementArray"/> class from a copy of a managed TElem array.</summary>
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/// <param name="array">The array of bytes to copy.</param>
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protected SafeElementArray(TElem[] array, Func<TElem, int> getElemSize = null) : base(IntPtr.Zero, 0, true) { GetElemSize = getElemSize; Elements = array; }
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/// <summary>Initializes a new instance of the <see cref="SafeElementArray{TElem, TPrefix, TMem}"/> class.</summary>
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/// <param name="byteSize">Size of the byte.</param>
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/// <param name="elementCount">The element count. This value can be 0.</param>
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protected SafeElementArray(int byteSize, int elementCount) : base(byteSize)
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{
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Zero();
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if (elementCount > 0)
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IntCount = elementCount;
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}
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private SafeElementArray(int elementCount) : base(GetRequiredSize(elementCount)) { }
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/// <summary>Gets the number of elements contained in the <see cref="SafeElementArray{TElem, TPrefix, TMem}"/>.</summary>
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protected TPrefix Count
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{
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get => IsInvalid ? default(TPrefix) : handle.ToStructure<TPrefix>();
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private set { if (!IsInvalid) Marshal.StructureToPtr(value, handle, false); }
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}
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/// <summary>Gets or sets the elements.</summary>
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/// <value>The elements of the array.</value>
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protected TElem[] Elements
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{
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get => handle.ToArray<TElem>(IntCount, PrefixSize);
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set
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{
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Size = GetElemSize != null ? PrefixSize + value.Sum(GetElemSize) : GetRequiredSize(value.Length);
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InteropExtensions.MarshalToPtr(value, handle, PrefixSize);
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IntCount = value.Length;
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}
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}
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protected Func<TElem, int> GetElemSize { get; set; }
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private int IntCount
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{
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get => Convert.ToInt32(Count);
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set => Count = (TPrefix)Convert.ChangeType(value, typeof(TPrefix));
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}
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/// <summary>Returns an enumerator that iterates through the collection.</summary>
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/// <returns>A <see cref="IEnumerator{TElem}"/> that can be used to iterate through the collection.</returns>
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public IEnumerator<TElem> GetEnumerator() => ((IEnumerable<TElem>)Elements).GetEnumerator();
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/// <summary>Returns an enumerator that iterates through a collection.</summary>
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/// <returns>An <see cref="IEnumerator"/> object that can be used to iterate through the collection.</returns>
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IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
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/// <summary>Converts a byte count to a element count.</summary>
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/// <param name="byteSize">The byte count.</param>
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/// <returns>The converted element count.</returns>
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/// <exception cref="ArgumentException">Byte count does not match this structure.</exception>
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protected static uint BytesToCount(uint byteSize)
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{
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if ((byteSize - PrefixSize) % ElemSize != 0) throw new ArgumentException("Byte count does not match this structure.");
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return (uint)((byteSize - PrefixSize) / ElemSize);
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}
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private static int GetRequiredSize(int elementCount) => PrefixSize + ElemSize * elementCount;
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}
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}
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