ReadProcessMemory 函数的 ByRef 与 ByVal

ReadProcessMemory 函数是一种在Windows操作系统中使用的函数，它用于从一个进程的内存中读取数据。该函数可以通过使用ByRef和ByVal参数来指定数据传递方式。在本文中，我们将详细介绍这两个参数的区别，并提供一些示例代码来说明它们的用法。

vb
Declare Function ReadProcessMemory Lib "kernel32" (ByVal hProcess As IntPtr, ByVal lpBaseAddress As IntPtr, ByRef lpBuffer As Byte(), ByVal nSize As Integer, ByRef lpNumberOfBytesRead As Integer) As Boolean
Sub Main()
    Dim processHandle As IntPtr = OpenProcess(ProcessAccessFlags.All, False, processId)
    Dim buffer(1024) As Byte
    Dim bytesRead As Integer = 0
    ReadProcessMemory(processHandle, baseAddress, buffer, buffer.Length, bytesRead)
    ' 使用读取到的数据做更多的操作...
    CloseHandle(processHandle)
End Sub

vb
Declare Function ReadProcessMemory Lib "kernel32" (ByVal hProcess As IntPtr, ByVal lpBaseAddress As IntPtr, ByVal lpBuffer As IntPtr, ByVal nSize As Integer, ByVal lpNumberOfBytesRead As IntPtr) As Boolean
Sub Main()
    Dim processHandle As IntPtr = OpenProcess(ProcessAccessFlags.All, False, processId)
    Dim bufferAddress As IntPtr = Marshal.AllocHGlobal(bufferSize)
    Dim bytesReadAddress As IntPtr = Marshal.AllocHGlobal(Marshal.SizeOf(GetType(Integer)))
    ReadProcessMemory(processHandle, baseAddress, bufferAddress, bufferSize, bytesReadAddress)
    Dim bytesRead As Integer = Marshal.ReadInt32(bytesReadAddress)
    Dim buffer(bufferSize - 1) As Byte
    Marshal.Copy(bufferAddress, buffer, 0, buffer.Length)
    ' 使用读取到的数据做更多的操作...
    Marshal.FreeHGlobal(bufferAddress)
    Marshal.FreeHGlobal(bytesReadAddress)
    CloseHandle(processHandle)
End Sub