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预期行为：中间 C 在一个 midi 乐器上演奏，然后是另一个。实际行为：DL 弃用警告并且没有声音。运行 Windows 7。

编码：

require "dl/import"

class LiveMIDI
    ON = 0x90
    OFF =0x80
    PC = 0xc0

    def initialize
        open
    end

    def note_on(channel, note, velocity=64)
        message(ON | channel, note, velocity)
    end

    def note_off(channel, note, velocity=64)
        message(OFF | channel, note, velocity)
    end

    def program_change(channel, preset) 
        message(PC | channel, preset)
    end

    module C
        extend DL::Importer
        dlload "winmm"

        extern "int midiOutOpen(HMIDIOUT*, int, int, int, int)"
        extern "int midiOutClose(int)"
        extern "int midiOutShortMsg(int, int)"
    end

    def open
        @device = DL.malloc(DL::Importer.sizeof("int"))
        C.midiOutOpen(@device, -1, 0, 0, 0)
    end

    def close
        C.midiOutClose(@device.ptr.to_i)
    end

    def message(one, two=0, three=0)
        message = one + (two << 8) + (three << 16)
        C.midiOutShortMsg(DL::CPtr.to_ptr(@device).to_i, message)
    end
end

midi = LiveMIDI.new
midi.note_on(0, 60, 100)
sleep(1)
midi.note_off(0, 60)
midi.program_change(1, 40)
midi.note_on(1, 60, 100)
sleep(1)
midi.note_off(1, 60)

摘自《实用 Ruby 项目》一书。根据第 2 章 11-15 页上的数字。代码稍作修改以处理 Ruby 1.9 中对 Ruby DL 的更改。

4

1 回答 1

2

你必须写

DL::CPtr.malloc(DL::Importer.sizeof("int")

代替

DL.malloc(DL::Importer.sizeof("int"))

创建一个指针对象 ( DL::CPtr) 而不仅仅是获取一个整数地址。

还

DL::CPtr.to_ptr(@device).to_i

必须

@device.ptr.to_i

甚至可能

@device.ptr

这是使用 DL 的替换Fiddle的代码的固定版本：

require 'fiddle/import'
require 'fiddle/types'

class LiveMIDI
  ON = 0x90
  OFF = 0x80
  PC = 0xc0

  def initialize
    open
  end

  def note_on(channel, note, velocity = 64)
    message(ON | channel, note, velocity)
  end

  def note_off(channel, note, velocity = 64)
    message(OFF | channel, note, velocity)
  end

  def program_change(channel, preset)
    message(PC | channel, preset)
  end

  module C
    extend Fiddle::Importer
    dlload 'winmm'
    # defines a few Windows-specific types such as DWORD or UINT
    include Fiddle::Win32Types
    # some other types not defined by the previous line
    typealias 'HMIDIOUT', 'void*'
    typealias 'LPHMIDIOUT', 'HMIDIOUT*'
    typealias 'DWORD_PTR', 'uintptr_t'
    typealias 'MMRESULT', 'UINT'

    extern 'MMRESULT midiOutOpen(LPHMIDIOUT, UINT, DWORD_PTR, DWORD_PTR, DWORD)'
    extern 'MMRESULT midiOutClose(HMIDIOUT)'
    extern 'MMRESULT midiOutShortMsg(HMIDIOUT, DWORD)'
  end

  def open
    @device = Fiddle::Pointer.malloc(Fiddle::SIZEOF_VOIDP)
    C.midiOutOpen(@device, -1, 0, 0, 0)
  end

  def close
    C.midiOutClose(@device.ptr)
  end

  def message(one, two = 0, three = 0)
    message = one + (two << 8) + (three << 16)
    C.midiOutShortMsg(@device.ptr, message)
  end
end

除了我根据MSDN 上的文档添加或更正的类型之外，它或多或少是相同的。错误的类型可能会导致不明显的问题。

于 2015-09-17T07:27:42.780 回答