在PowerShell中從C#訪問固定大小的陣列元素

尋找訪問單個陣列元素的方法（此問題的繼續）

$CSharpCode = @"
using System;
namespace TestStructure
{
    public struct TestStructure
    {
       public byte Field1;
       public unsafe fixed byte Field2[4];
    }
}
"@

$cp = New-Object System.CodeDom.Compiler.CompilerParameters
$cp.CompilerOptions = '/unsafe'
Add-Type -TypeDefinition $CSharpCode -CompilerParameters $cp

function ConvertTo-Struct
{
  # Only accept struct types (sealed value types that are neither primitive nor enum)
  param(
    [Parameter(Mandatory = $true)]
    [ValidateScript({ $_.IsValueType -and $_.IsSealed -and -not($_.IsPrimitive -or $_.IsEnum) })]
    [Type]$TargetType,

    [Parameter(Mandatory = $true)]
    [byte[]]$BinaryData
  )

  # Start by calculating minimum size of the underlying memory allocation for the new struct
  $memSize = [System.Runtime.InteropServices.Marshal]::SizeOf([type]$TargetType)

  # Make sure user actually passed enough data to initialize struct
  if($memSize -gt $BinaryData.Length){
    Write-Error "Not enough binary data to create an instance of [$($TargetType.FullName)]"
    return
  }

  # now we just need some unmanaged memory in which to create our struct instance
  $memPtr = [IntPtr]::Zero
  try {
    $memPtr = [System.Runtime.InteropServices.Marshal]::AllocHGlobal($memSize)

    # copy byte array to allocated unmanaged memory from previous step
    [System.Runtime.InteropServices.Marshal]::Copy($BinaryData, 0, $memPtr, $memSize)

    # then marshal the new memory region as a struct and return
    return [System.Runtime.InteropServices.Marshal]::PtrToStructure($memPtr, [type]$TargetType)
  }
  finally {
    # and finally remember to clean up the allocated memory
    if($memPtr -ne [IntPtr]::Zero){
      [System.Runtime.InteropServices.Marshal]::FreeHGlobal($memPtr)
    }
  }
}

$testStructure = ConvertTo-Struct -TargetType ([TestStructure.TestStructure]) -BinaryData (1..100 -as [byte[]])
$testStructure.Field1
$testStructure.Field2

這會產生以下輸出：

1

FixedElementField
-----------------
                2

• 只有第一個陣列元素$Field2是可見的，不能訪問其他使用$testStructure.Field2[x]

尋找一種方法來迭代已知型別/大小的 FixedBuffer

$testStructure.Field2.GetType() 說<Field2>e__FixedBuffer0 $testStructure.Field2.FixedElementField.GetType() 是位元組

• 看不到訪問陣列其他元素的方法。

uj5u.com熱心網友回復：

PowerShell 的型別配接器實際上并沒有任何東西來處理unsafe fixed byte[]欄位，從底層型別系統的角度來看，實際上是原始指標。

底層記憶體分配的宣告大小僅存盤在元資料中，您可以按如下方式定位：

# Locate appropriate field metadata
$fieldInfo = $testStructure.GetType().GetField('Field2')

# Discover fixed buffer attribute
$fixedBufferAttribute = $fieldInfo.CustomAttributes.Where({$_.AttributeType -eq [System.Runtime.CompilerServices.FixedBufferAttribute]}) |Select -First 1

現在我們可以確定大小和預期的陣列元素型別：

if($fixedBufferAttribute)
{
    # Grab array element type   size from FixedBuffer attribute
    $elemType,$size = $fixedBufferAttribute.ConstructorArguments

    # Create array of appropriate size
    $values = $elemType.MakeArrayType()::new($size)

    # Copy values from fixed buffer pointer to managed array
    try {
        $fixedBufferHandle = [System.Runtime.InteropServices.GCHandle]::Alloc($TestStructure.Field2, 'Pinned')
        [System.Runtime.InteropServices.Marshal]::Copy($fixedBufferHandle.AddrOfPinnedObject(), $values, 0, $size)

        return $values
    }
    finally {
        $fixedBufferHandle.Free()
    }
}

您會發現$values現在包含預期的位元組值 2、3、4 和 5

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