Question

我认为我以错误的方式使用了指针，GetLastError()并没有告诉我更多错误信息。

我真的不知道指针在FFI::Pointer和FFI::MemoryPointer之间是如何工作的

require 'ffi'

module Win32
    extend FFI::Library

    PROCESS_VM_READ = 0x0010
    PROCESS_VM_WRITE = 0x0020
    PROCESS_ALL_ACCESS = PROCESS_VM_READ | PROCESS_VM_WRITE

    ffi_lib 'kernel32'
    ffi_convention :stdcall

    attach_function :OpenProcess, [:uint, :bool, :uint], :pointer
    attach_function :CloseHandle, [:pointer], :bool
    attach_function :ReadProcessMemory, [:pointer, :pointer, :pointer, :size_t, :pointer], :int
    attach_function :WriteProcessMemory, [:pointer, :pointer, :pointer, :size_t, :pointer], :int
    attach_function :GetLastError, [], :uint

    class << self
        def read(handle, address)
            addr = FFI::Pointer.new(:pointer, address)
            buffer = FFI::MemoryPointer.new(:pointer)
            if ReadProcessMemory(handle, addr, buffer, 4, nil) == 0
                puts "Error: #{GetLastError()}"
            end
            return buffer.get_int(0)
        end
        def write(handle, address, value)
            addr = FFI::Pointer.new(:pointer, address)
            buffer = FFI::MemoryPointer.new(:long, 4)
            buffer.put_int(0, value)
            if WriteProcessMemory(handle, addr, buffer, 4, nil) == 0
                "Error: #{GetLastError()}"
            end
        end
    end
end

pid = 4984
handle = Win32.OpenProcess(Win32::PROCESS_ALL_ACCESS, false, pid)

puts Win32.read(handle, 0x0192D514) # => 45
puts Win32.write(handle, 0x0192D514, 20) # => Error: 0
puts Win32.read(handle, 0x0192D514) # => 45

Win32.CloseHandle(handle)

输出：

45
Error: 0
45

Answer 1

我发现了问题，这是手柄的访问权限，请更改：

handle = Win32.OpenProcess(Win32::PROCESS_ALL_ACCESS, false, pid)

到

handle = Win32.OpenProcess(Win32::PROCESS_VM_OPERATION | Win32::PROCESS_ALL_ACCESS, false, pid)

并添加模块Win32：

PROCESS_VM_OPERATION = 0x0008

我希望能对某人有所帮助，谢谢！

如何在Ruby和FFI中传递指针？

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