Add span API for concatenate. Empty span support.

Author: vitalsong

include/dsplib/slice.h

@@ -20,11 +20,18 @@ template<typename T>
 class const_slice_t;
 
 //----------------------------------------------------------------------------------------
+//TODO: support empty slices
 class base_slice_t
 {
 public:
+    base_slice_t() = default;
+
     explicit base_slice_t(int n, int i1, int i2, int m) {
-        DSPLIB_ASSERT(n != 0, "Slicing from an empty array");
+        //is empty
+        if (n == 0) {
+            return;
+        }
+
         DSPLIB_ASSERT(m != 0, "Slice stride cannot be zero");
 
         _m = m;
@@ -56,6 +63,10 @@ class base_slice_t
         }
     }
 
+    bool empty() const noexcept {
+        return (_nc == 0);
+    }
+
 protected:
     int _i1{0};
     int _i2{0};
@@ -73,6 +84,8 @@ class const_slice_t : public base_slice_t
     friend class slice_t<T>;
     using const_iterator = SliceIterator<const T>;
 
+    const_slice_t() = default;
+
     const_slice_t(const T* data, int size, int i1, int i2, int m)
       : base_slice_t(size, i1, i2, m)
       , _data{data} {
@@ -123,6 +136,8 @@ class slice_t : public base_slice_t
     using iterator = SliceIterator<T>;
     using const_iterator = SliceIterator<const T>;
 
+    slice_t() = default;
+
     slice_t(T* data, int size, int i1, int i2, int m)
       : base_slice_t(size, i1, i2, m)
       , _data{data} {

include/dsplib/span.h

@@ -28,6 +28,8 @@ class mut_span_t : public slice_t<T>
 public:
     friend class span_t<T>;
 
+    mut_span_t() = default;
+
     explicit mut_span_t(T* data, int size)
       : slice_t<T>(data, size, 0, size, 1)
       , _ptr{data}
@@ -129,6 +131,8 @@ class span_t : public const_slice_t<T>
 public:
     friend class mut_span_t<T>;
 
+    span_t() = default;
+
     explicit span_t(const T* data, int size)
       : const_slice_t<T>(data, size, 0, size, 1)
       , _ptr{data}

include/dsplib/utils.h

@@ -57,28 +57,9 @@ template<typename T1, typename T2, typename T3, class R = typename enable_if_som
 }
 
 //join a sequence of arrays
-//TODO: add impl for slice/span
-template<class T>
-T concatenate(const T& a1, const T& a2, const T& a3 = T(), const T& a4 = T(), const T& a5 = T()) {
-    std::array<const T*, 5> arrays{&a1, &a2, &a3, &a4, &a5};
-
-    size_t nr = 0;
-    for (auto array : arrays) {
-        nr += array->size();
-    }
-
-    T r(nr);
-    auto* pr = r.data();
-    for (auto array : arrays) {
-        const auto* pa = array->data();
-        for (int i = 0; i < array->size(); ++i) {
-            *pr = pa[i];
-            pr++;
-        }
-    }
-
-    return r;
-}
+//TODO: add slice args?
+arr_real concatenate(span_real x1, span_real x2, span_real x3 = {}, span_real x4 = {}, span_real x5 = {});
+arr_cmplx concatenate(span_cmplx x1, span_cmplx x2, span_cmplx x3 = {}, span_cmplx x4 = {}, span_cmplx x5 = {});
 
 //create array of all zeros
 inline arr_real zeros(int n) {

lib/fft/czt.cpp

@@ -36,7 +36,7 @@ class CztPlanImpl
         }
 
         const arr_cmplx dp = chirp.slice(0, m + n - 1);
-        _ich = _fft2->solve((1.0 / dp) | zeros(n2 - m - n + 1));
+        _ich = _fft2->solve(zeropad((1.0 / dp), n2));
         _rp = chirp.slice(_n - 1, _m + _n - 1);
     }
 

lib/hilbert.cpp

@@ -30,13 +30,13 @@ arr_cmplx HilbertFilter::design_fir(int flen, real_t fs, real_t f1) {
 
     const auto lm = power(arange(k1 - 1) / (k1 - 1), 8);
     const auto rm = flip(lm);
-    const arr_cmplx H = complex(lm | ones(k2 - k1 + 1) | rm | zeros(N / 2 - 1));
+    const arr_cmplx H = complex(concatenate(lm, ones(k2 - k1 + 1), rm, zeros(N / 2 - 1)));
     const arr_cmplx h = ifft(H);   // desired impulse response
 
     const auto w = window::kaiser(M, 8);
-    const auto wzp = *w.slice(M / 2, M) | zeros(N - M) | *w.slice(0, M / 2);
+    const auto wzp = concatenate(w.slice(M / 2, M), zeros(N - M), w.slice(0, M / 2));
     const auto hw = wzp * h;   // single-sideband FIR filter, zero-centered
-    const auto hh = *hw.slice(N - (M / 2), N) | *hw.slice(0, (M + 1) / 2);   // casual FIR
+    const auto hh = concatenate(hw.slice(N - (M / 2), N), hw.slice(0, (M + 1) / 2));   // casual FIR
     return hh;
 }
 

lib/medfilt.cpp

@@ -69,7 +69,7 @@ arr_real medfilt(arr_real& x, int n) {
     auto flt = MedianFilter(n);
     const int n1 = (n / 2);
     const int n2 = (n % 2 == 1) ? (n / 2) : (n / 2 - 1);
-    arr_real xp = zeros(n1) | x | zeros(n2);
+    arr_real xp = concatenate(zeros(n1), x, zeros(n2));
     auto y = flt.process(xp);
     return y.slice(n - 1, indexing::end);
 }

lib/utils.cpp

@@ -200,32 +200,60 @@ static int _finddelay(const base_array<T>& x1, const base_array<T>& x2) {
     return -delay;
 }
 
-int finddelay(const dsplib::arr_real& x1, const dsplib::arr_real& x2) {
+int finddelay(const arr_real& x1, const arr_real& x2) {
     return _finddelay(x1, x2);
 }
 
-int finddelay(const dsplib::arr_cmplx& x1, const dsplib::arr_cmplx& x2) {
+int finddelay(const arr_cmplx& x1, const arr_cmplx& x2) {
     return _finddelay(x1, x2);
 }
 
-arr_real zeropad(span_t<real_t> x, int n) {
+template<typename T>
+static base_array<T> _zeropad(span_t<T> x, int n) {
     DSPLIB_ASSERT(x.size() <= n, "padding size error");
     if (x.size() == n) {
         return x;
     }
-    arr_real r(n);
+    base_array<T> r(n);
     r.slice(0, x.size()) = x;
     return r;
 }
 
+arr_real zeropad(span_t<real_t> x, int n) {
+    return _zeropad<real_t>(x, n);
+}
+
 arr_cmplx zeropad(span_t<cmplx_t> x, int n) {
-    DSPLIB_ASSERT(x.size() <= n, "padding size error");
-    if (x.size() == n) {
-        return x;
+    return _zeropad<cmplx_t>(x, n);
+}
+
+template<class T>
+static base_array<T> _concatenate(span_t<T> a1, span_t<T> a2, span_t<T> a3, span_t<T> a4, span_t<T> a5) {
+    std::array<span_t<T>, 5> span_list{a1, a2, a3, a4, a5};
+
+    size_t nr = 0;
+    for (const auto& x : span_list) {
+        nr += x.size();
+    }
+
+    base_array<T> r(nr);
+    auto* pr = r.data();
+    for (const auto& x : span_list) {
+        if (x.empty()) {
+            continue;
+        }
+        std::memcpy(pr, x.data(), x.size() * sizeof(T));
+        pr += x.size();
     }
-    arr_cmplx r(n);
-    r.slice(0, x.size()) = x;
     return r;
 }
 
+arr_real concatenate(span_real x1, span_real x2, span_real x3, span_real x4, span_real x5) {
+    return _concatenate<real_t>(x1, x2, x3, x4, x5);
+}
+
+arr_cmplx concatenate(span_cmplx x1, span_cmplx x2, span_cmplx x3, span_cmplx x4, span_cmplx x5) {
+    return _concatenate<cmplx_t>(x1, x2, x3, x4, x5);
+}
+
 }   // namespace dsplib

lib/window.cpp

@@ -109,7 +109,7 @@ arr_real kaiser(int nw, real_t beta) {
         w[i] = std::abs(_besseli0(beta * std::sqrt(1 - (xi / xind))) / bes);
     }
     const arr_real wl = flip(*w.slice(odd, n));
-    return (wl | w);
+    return concatenate(wl, w);
 }
 
 }   // namespace window