swift - 调用函数后释放类变量

Question

我在 swift 中有一个函数，如下所示。有一个循环引用了此类实例中存在的变量。 (fftfilterbankReal 是类中的一个数组)。然而，在一次通过后，我在代码行 'for i in 0..

在调试器中，似乎在此循环的第 2 次迭代中，“self”下拉列表下没有变量。

如果我注释掉行 'vDSP_zvmul(&kernel!, 1, &fft1Input, 1, &result, 1, vDSP_Length(r.count), 1)' 然后循环运行，我可以随时调试并直观地看到调试器中的自变量。

我错过了什么似乎让这些变量消失了？我已经阅读了内存分配等内容，并且我的类变量是使用“var”声明的，仅此而已，因为它应该默认为 strong in swift。

func convolveInput(realsamples:[Float], imagsamples:[Float]) -> [Float]{
    realResult = Array(repeating: [], count: filterbankReal.count)
    imagResult = Array(repeating: [], count: filterbankReal.count)
    let x = realsamples
    let y = imagsamples
    var N = x.count
    var logN = 16          
    var fft1Setup = vDSP_create_fftsetup(UInt(logN), FFTRadix(FFT_RADIX2))!

    var paddedLength = x.count + filterbankReal.count - 1
    var halfPaddedLength = paddedLength/2
    var halfKernelLength = kernelLength/2
    //setup Complex Buffer 1
    var reals = [Float]()
    var imags = [Float]()
    for i in 0..<x.count{
        reals.append(x[i])
        imags.append(y[i])

    }
    var complexBuffer1 = DSPSplitComplex(realp: UnsafeMutablePointer(mutating: reals), imagp: UnsafeMutablePointer(mutating: imags))

    //Perform FFT on incoming samples
    var re = [Float](repeating:0.0, count: N)
    var im = [Float](repeating:0.0, count: N)
    var fft1Input = DSPSplitComplex(realp: UnsafeMutablePointer(mutating: re), imagp: UnsafeMutablePointer(mutating: im))

    var fftlength = 10
    vDSP_fft_zop(fft1Setup, &(complexBuffer1), 1, &fft1Input, 1, UInt(fftlength), Int32(FFT_FORWARD))

    //Remove DC from FFT Signal
    re.remove(at: 0)
    im.remove(at: 0)

for i in 0..<self.fftfilterbankReal.count {
 var r:[Float] = self.fftfilterbankReal[i]           
        var im:[Float] = self.fftfilterbankImag[i]          
        var kernel:DSPSplitComplex? = DSPSplitComplex(realp: &r, imagp: &im)
var res:Float = 0
        var ims:Float = 0
        var result:DSPSplitComplex = DSPSplitComplex(realp: &res, imagp: &ims)
        vDSP_zvmul(&kernel!, 1, &fft1Input, 1, &result, 1, vDSP_Length(r.count), 1)
        self.realResult[i].append(res)
        self.imagResult[i].append(ims)
    }

Answer 1

您的代码展示了使用数组和指针时的错误用法。

例如:

var complexBuffer1 = DSPSplitComplex(realp: UnsafeMutablePointer(mutating: reals), imagp: UnsafeMutablePointer(mutating: imags))

或:

var kernel:DSPSplitComplex? = DSPSplitComplex(realp: &r, imagp: &im)

DSPSplitComplex 分别持有实部和虚部两个指针，不复制内容。您不应为此类参数传递 Swift 数组。

代码中最关键的部分是...

var res:Float = 0
var ims:Float = 0
var result:DSPSplitComplex = DSPSplitComplex(realp: &res, imagp: &ims)
vDSP_zvmul(&kernel!, 1, &fft1Input, 1, &result, 1, vDSP_Length(r.count), 1)

vDSP_zvmul 生成N(在你的代码中N = vDSP_Length(r.count))复数，所以你需要准备一个可以容纳 N 个元素的区域。

一旦您使用当前代码调用 vDSP_zvmul，您就会破坏整个堆栈内容，从而导致您遇到的情况:

In the debugger it seems that on the 2nd iteration of this loop, there are no variables under the 'self' drop down.

---

你隐藏了代码的很多部分，所以很难猜测你真正想做什么，但如果我以更安全的方式重写你的代码，它会是这样的:

func convolveInput(realsamples:[Float], imagsamples:[Float]) -> [Float]{
    realResult = Array(repeating: [], count: filterbankReal.count)
    imagResult = Array(repeating: [], count: filterbankReal.count)
    let x = realsamples
    let y = imagsamples
    var N = x.count
    var logN = 16
    var fft1Setup = vDSP_create_fftsetup(UInt(logN), FFTRadix(FFT_RADIX2))!

    var paddedLength = x.count + filterbankReal.count - 1
    var halfPaddedLength = paddedLength/2
    var halfKernelLength = kernelLength/2
    //setup Complex Buffer 1
    var reals = UnsafeMutableBufferPointer<Float>.allocate(capacity: x.count)
    defer {reals.deallocate()}
    var imags = UnsafeMutableBufferPointer<Float>.allocate(capacity: y.count)
    defer {imags.deallocate()}
    _ = reals.initialize(from: x)
    _ = imags.initialize(from: y)
    var complexBuffer1 = DSPSplitComplex(realp: reals.baseAddress!, imagp: imags.baseAddress!)

    //Perform FFT on incoming samples
    var re = UnsafeMutableBufferPointer<Float>.allocate(capacity: N)
    defer {re.deallocate()}
    var im = UnsafeMutableBufferPointer<Float>.allocate(capacity: N)
    defer {im.deallocate()}
    var fft1Input = DSPSplitComplex(realp: re.baseAddress!, imagp: im.baseAddress!)

    let fftlength = 10
    vDSP_fft_zop(fft1Setup, &complexBuffer1, 1, &fft1Input, 1, UInt(fftlength), Int32(FFT_FORWARD))

    //Remove DC from FFT Signal
    fft1Input = DSPSplitComplex(realp: re.baseAddress!+1, imagp: im.baseAddress!+1)

    for i in 0..<self.fftfilterbankReal.count {
        self.fftfilterbankReal[i].withUnsafeMutableBufferPointer {rBuf in
            self.fftfilterbankImag[i].withUnsafeMutableBufferPointer {imBuf in
                var kernel = DSPSplitComplex(realp: rBuf.baseAddress!, imagp: imBuf.baseAddress!)
                var res = UnsafeMutableBufferPointer<Float>.allocate(capacity: rBuf.count)
                defer {res.deallocate()}
                var ims = UnsafeMutableBufferPointer<Float>.allocate(capacity: rBuf.count)
                defer {ims.deallocate()}
                var result:DSPSplitComplex = DSPSplitComplex(realp: res.baseAddress!, imagp: ims.baseAddress!)
                vDSP_zvmul(&kernel, 1, &fft1Input, 1, &result, 1, vDSP_Length(rBuf.count), 1)
                //vDSP_zvmul generates `N` complex numbers,
                // I do not understand what you really want to do...
                self.realResult[i].append(res[0])
                self.imagResult[i].append(ims[0])
            }
        }
    }

    //...
}

可能还有其他部分需要修复，但无论如何，请尝试看看你得到了什么。