DSP: Allowed AudioBlocks of const elements

BREAKING-CHANGES.txt

@@ -4,6 +4,28 @@ JUCE breaking changes
 Develop
 =======
 
+Change
+------
+The AudioBlock class now differentiates between const and non-const data.
+
+Possible Issues
+---------------
+The return type of the getInputBlock() method of the ProcessContextReplacing
+and ProcessContextNonReplacing classes has changed from AudioBlock<X> to
+AudioBlock<const X>.
+
+Workaround
+----------
+For ProcessContextReplacing you should use getOutputBlock() instead of
+getInputBlock(). For ProcessContextNonReplacing attempting to modify the input
+block is very likely an error.
+
+Rationale
+---------
+This change makes the intent of the code much clearer and means that we can
+remove some const_cast operations.
+
+
 Change
 ------
 The formatting of floating point numbers written to XML and JSON files has

modules/juce_dsp/containers/juce_AudioBlock.h

@@ -32,10 +32,17 @@ namespace dsp
 #ifndef DOXYGEN
 namespace SampleTypeHelpers // Internal classes needed for handling sample type classes
 {
-    template <typename Container> struct ElementType { using Type = typename Container::value_type; };
-    template <> struct ElementType<float>            { using Type = float;  };
-    template <> struct ElementType<double>           { using Type = double; };
-    template <> struct ElementType<long double>      { using Type = long double; };
+    template <typename T, bool = std::is_floating_point<T>::value>
+    struct ElementType
+    {
+        using Type = T;
+    };
+
+    template <typename T>
+    struct ElementType<T, false>
+    {
+        using Type = typename T::value_type;
+    };
 }
 #endif
 
@@ -56,6 +63,15 @@ namespace SampleTypeHelpers // Internal classes needed for handling sample type
 template <typename SampleType>
 class AudioBlock
 {
+private:
+    template <typename OtherSampleType>
+    using MayUseConvertingConstructor =
+        std::enable_if_t<std::is_same<std::remove_const_t<SampleType>,
+                                      std::remove_const_t<OtherSampleType>>::value
+                             && std::is_const<SampleType>::value
+                             && ! std::is_const<OtherSampleType>::value,
+                         int>;
+
 public:
     //==============================================================================
     using NumericType = typename SampleTypeHelpers::ElementType<SampleType>::Type;
@@ -127,7 +143,8 @@ public:
         Therefore it is the user's responsibility to ensure that the buffer is retained
         throughout the life-time of the AudioBlock without being modified.
     */
-    AudioBlock (AudioBuffer<SampleType>& buffer) noexcept
+    template <typename OtherSampleType>
+    AudioBlock (AudioBuffer<OtherSampleType>& buffer) noexcept
         : channels (buffer.getArrayOfWritePointers()),
           numChannels (static_cast<ChannelCountType> (buffer.getNumChannels())),
           numSamples (static_cast<size_t> (buffer.getNumSamples()))
@@ -139,7 +156,8 @@ public:
         Therefore it is the user's responsibility to ensure that the buffer is retained
         throughout the life-time of the AudioBlock without being modified.
     */
-    AudioBlock (AudioBuffer<SampleType>& buffer, size_t startSampleIndex) noexcept
+    template <typename OtherSampleType>
+    AudioBlock (AudioBuffer<OtherSampleType>& buffer, size_t startSampleIndex) noexcept
         : channels (buffer.getArrayOfWritePointers()),
           numChannels (static_cast<ChannelCountType> (buffer.getNumChannels())),
           startSample (startSampleIndex),
@@ -151,16 +169,45 @@ public:
     AudioBlock (const AudioBlock& other) noexcept = default;
     AudioBlock& operator= (const AudioBlock& other) noexcept = default;
 
+    template <typename OtherSampleType, MayUseConvertingConstructor<OtherSampleType> = 0>
+    AudioBlock (const AudioBlock<OtherSampleType>& other) noexcept
+        : channels { other.channels },
+          numChannels { other.numChannels },
+          startSample { other.startSample },
+          numSamples { other.numSamples }
+    {
+    }
+
+    template <typename OtherSampleType, MayUseConvertingConstructor<OtherSampleType> = 0>
+    AudioBlock& operator= (const AudioBlock<OtherSampleType>& other) noexcept
+    {
+        AudioBlock copy { other };
+        swap (copy);
+        return *this;
+    }
+
+    void swap (AudioBlock& other) noexcept
+    {
+        std::swap (other.channels, channels);
+        std::swap (other.numChannels, numChannels);
+        std::swap (other.startSample, startSample);
+        std::swap (other.numSamples, numSamples);
+    }
+
     //==============================================================================
-    bool operator== (const AudioBlock& other) const noexcept
+    template <typename OtherSampleType>
+    bool operator== (const AudioBlock<OtherSampleType>& other) const noexcept
     {
-        return std::equal (channels,       channels + numChannels,
-                           other.channels, other.channels + other.numChannels)
-                   && startSample == other.startSample
-                   && numSamples == other.numSamples;
+        return std::equal (channels,
+                           channels + numChannels,
+                           other.channels,
+                           other.channels + other.numChannels)
+               && startSample == other.startSample
+               && numSamples == other.numSamples;
     }
 
-    bool operator!= (const AudioBlock& other) const noexcept
+    template <typename OtherSampleType>
+    bool operator!= (const AudioBlock<OtherSampleType>& other) const noexcept
     {
         return ! (*this == other);
     }
@@ -264,7 +311,8 @@ public:
     }
 
     /** Copy the values in src to the receiver. */
-    forcedinline AudioBlock& copy (AudioBlock src) noexcept
+    template <typename OtherSampleType>
+    forcedinline AudioBlock& copy (const AudioBlock<OtherSampleType>& src) noexcept
     {
         auto maxChannels = jmin (src.numChannels, numChannels);
         auto n = static_cast<int> (jmin (src.numSamples, numSamples) * sizeFactor);
@@ -381,7 +429,8 @@ public:
     }
 
     /** Adds the source values to the receiver. */
-    forcedinline AudioBlock& add (AudioBlock src) noexcept
+    template <typename OtherSampleType>
+    forcedinline AudioBlock& add (AudioBlock<OtherSampleType> src) noexcept
     {
         jassert (numChannels == src.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src.numSamples) * sizeFactor);
@@ -393,7 +442,8 @@ public:
     }
 
     /** Adds a fixed value to each source value and stores it in the destination array of the receiver. */
-    forcedinline AudioBlock& JUCE_VECTOR_CALLTYPE add (AudioBlock src, SampleType value) noexcept
+    template <typename OtherSampleType>
+    forcedinline AudioBlock& JUCE_VECTOR_CALLTYPE add (AudioBlock<OtherSampleType> src, SampleType value) noexcept
     {
         jassert (numChannels == src.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src.numSamples) * sizeFactor);
@@ -405,7 +455,8 @@ public:
     }
 
     /** Adds each source1 value to the corresponding source2 value and stores it in the destination array of the receiver. */
-    forcedinline AudioBlock& add (AudioBlock src1, AudioBlock src2) noexcept
+    template <typename Src1SampleType, typename Src2SampleType>
+    forcedinline AudioBlock& add (AudioBlock<Src1SampleType> src1, AudioBlock<Src2SampleType> src2) noexcept
     {
         jassert (numChannels == src1.numChannels && src1.numChannels == src2.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src1.numSamples, src2.numSamples) * sizeFactor);
@@ -423,7 +474,8 @@ public:
     }
 
     /** Subtracts the source values from the receiver. */
-    forcedinline AudioBlock& subtract (AudioBlock src) noexcept
+    template <typename OtherSampleType>
+    forcedinline AudioBlock& subtract (AudioBlock<OtherSampleType> src) noexcept
     {
         jassert (numChannels == src.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src.numSamples) * sizeFactor);
@@ -435,13 +487,15 @@ public:
     }
 
     /** Subtracts a fixed value from each source value and stores it in the destination array of the receiver. */
-    forcedinline AudioBlock& JUCE_VECTOR_CALLTYPE subtract (AudioBlock src, SampleType value) noexcept
+    template <typename OtherSampleType>
+    forcedinline AudioBlock& JUCE_VECTOR_CALLTYPE subtract (AudioBlock<OtherSampleType> src, SampleType value) noexcept
     {
         return add (src, static_cast<SampleType> (-1.0) * value);
     }
 
     /** Subtracts each source2 value from the corresponding source1 value and stores it in the destination array of the receiver. */
-    forcedinline AudioBlock& subtract (AudioBlock src1, AudioBlock src2) noexcept
+    template <typename Src1SampleType, typename Src2SampleType>
+    forcedinline AudioBlock& subtract (AudioBlock<Src1SampleType> src1, AudioBlock<Src2SampleType> src2) noexcept
     {
         jassert (numChannels == src1.numChannels && src1.numChannels == src2.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src1.numSamples, src2.numSamples) * sizeFactor);
@@ -464,7 +518,8 @@ public:
     }
 
     /** Multiplies the source values to the receiver. */
-    forcedinline AudioBlock& multiply (AudioBlock src) noexcept
+    template <typename OtherSampleType>
+    forcedinline AudioBlock& multiply (AudioBlock<OtherSampleType> src) noexcept
     {
         jassert (numChannels == src.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src.numSamples) * sizeFactor);
@@ -476,7 +531,8 @@ public:
     }
 
     /** Multiplies a fixed value to each source value and stores it in the destination array of the receiver. */
-    forcedinline AudioBlock& JUCE_VECTOR_CALLTYPE multiply (AudioBlock src, SampleType value) noexcept
+    template <typename OtherSampleType>
+    forcedinline AudioBlock& JUCE_VECTOR_CALLTYPE multiply (AudioBlock<OtherSampleType> src, SampleType value) noexcept
     {
         jassert (numChannels == src.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src.numSamples) * sizeFactor);
@@ -488,7 +544,8 @@ public:
     }
 
     /** Multiplies each source1 value to the corresponding source2 value and stores it in the destination array of the receiver. */
-    forcedinline AudioBlock& multiply (AudioBlock src1, AudioBlock src2) noexcept
+    template <typename Src1SampleType, typename Src2SampleType>
+    forcedinline AudioBlock& multiply (AudioBlock<Src1SampleType> src1, AudioBlock<Src2SampleType> src2) noexcept
     {
         jassert (numChannels == src1.numChannels && src1.numChannels == src2.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src1.numSamples, src2.numSamples) * sizeFactor);
@@ -522,8 +579,8 @@ public:
     }
 
     /** Multiplies all channels of the source by a smoothly changing value and stores them in the receiver. */
-    template <typename SmoothingType>
-    AudioBlock& multiply (AudioBlock src, SmoothedValue<SampleType, SmoothingType>& value) noexcept
+    template <typename OtherSampleType, typename SmoothingType>
+    AudioBlock& multiply (AudioBlock<OtherSampleType> src, SmoothedValue<SampleType, SmoothingType>& value) noexcept
     {
         jassert (numChannels == src.numChannels);
 
@@ -548,7 +605,8 @@ public:
     }
 
     /** Multiplies each value in src with factor and adds the result to the receiver. */
-    forcedinline AudioBlock& JUCE_VECTOR_CALLTYPE addWithMultiply (AudioBlock src, SampleType factor) noexcept
+    template <typename OtherSampleType>
+    forcedinline AudioBlock& JUCE_VECTOR_CALLTYPE addWithMultiply (AudioBlock<OtherSampleType> src, SampleType factor) noexcept
     {
         jassert (numChannels == src.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src.numSamples) * sizeFactor);
@@ -560,7 +618,8 @@ public:
     }
 
     /** Multiplies each value in srcA with the corresponding value in srcB and adds the result to the receiver. */
-    forcedinline AudioBlock& addWithMultiply (AudioBlock src1, AudioBlock src2) noexcept
+    template <typename Src1SampleType, typename Src2SampleType>
+    forcedinline AudioBlock& addWithMultiply (AudioBlock<Src1SampleType> src1, AudioBlock<Src2SampleType> src2) noexcept
     {
         jassert (numChannels == src1.numChannels && src1.numChannels == src2.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src1.numSamples, src2.numSamples) * sizeFactor);
@@ -578,7 +637,8 @@ public:
     }
 
     /** Negates each value of source and stores it in the receiver. */
-    forcedinline AudioBlock& replaceWithNegativeOf (AudioBlock src) noexcept
+    template <typename OtherSampleType>
+    forcedinline AudioBlock& replaceWithNegativeOf (AudioBlock<OtherSampleType> src) noexcept
     {
         jassert (numChannels == src.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src.numSamples) * sizeFactor);
@@ -590,7 +650,8 @@ public:
     }
 
     /** Takes the absolute value of each element of src and stores it inside the receiver. */
-    forcedinline AudioBlock& replaceWithAbsoluteValueOf (AudioBlock src) noexcept
+    template <typename OtherSampleType>
+    forcedinline AudioBlock& replaceWithAbsoluteValueOf (AudioBlock<OtherSampleType> src) noexcept
     {
         jassert (numChannels == src.numChannels);
         auto n = static_cast<int> (jmin (numSamples, src.numSamples) * sizeFactor);
@@ -602,7 +663,8 @@ public:
     }
 
     /** Each element of receiver will be the minimum of the corresponding element of the source arrays. */
-    forcedinline AudioBlock& min (AudioBlock src1, AudioBlock src2) noexcept
+    template <typename Src1SampleType, typename Src2SampleType>
+    forcedinline AudioBlock& min (AudioBlock<Src1SampleType> src1, AudioBlock<Src2SampleType> src2) noexcept
     {
         jassert (numChannels == src1.numChannels && src1.numChannels == src2.numChannels);
         auto n = static_cast<int> (jmin (src1.numSamples, src2.numSamples, numSamples) * sizeFactor);
@@ -614,7 +676,8 @@ public:
     }
 
     /** Each element of the receiver will be the maximum of the corresponding element of the source arrays. */
-    forcedinline AudioBlock& max (AudioBlock src1, AudioBlock src2) noexcept
+    template <typename Src1SampleType, typename Src2SampleType>
+    forcedinline AudioBlock& max (AudioBlock<Src1SampleType> src1, AudioBlock<Src2SampleType> src2) noexcept
     {
         jassert (numChannels == src1.numChannels && src1.numChannels == src2.numChannels);
         auto n = static_cast<int> (jmin (src1.numSamples, src2.numSamples, numSamples) * sizeFactor);
@@ -653,11 +716,11 @@ public:
 
     //==============================================================================
     // This class can only be used with floating point types
-    static_assert (std::is_same<SampleType, float>::value
-                    || std::is_same<SampleType, double>::value
+    static_assert (std::is_same<std::remove_const_t<SampleType>, float>::value
+                    || std::is_same<std::remove_const_t<SampleType>, double>::value
                   #if JUCE_USE_SIMD
-                    || std::is_same<SampleType, SIMDRegister<float>>::value
-                    || std::is_same<SampleType, SIMDRegister<double>>::value
+                    || std::is_same<std::remove_const_t<SampleType>, SIMDRegister<float>>::value
+                    || std::is_same<std::remove_const_t<SampleType>, SIMDRegister<double>>::value
                   #endif
                    , "AudioBlock only supports single or double precision floating point types");
 
@@ -666,8 +729,8 @@ public:
         The function supplied must take a SampleType as its parameter, and return a SampleType.
         The two blocks must have the same number of channels and samples.
     */
-    template <typename FunctionType>
-    static void process (AudioBlock inBlock, AudioBlock outBlock, FunctionType&& function)
+    template <typename Src1SampleType, typename Src2SampleType, typename FunctionType>
+    static void process (AudioBlock<Src1SampleType> inBlock, AudioBlock<Src2SampleType> outBlock, FunctionType&& function)
     {
         auto len = inBlock.getNumSamples();
         auto numChans = inBlock.getNumChannels();
@@ -707,6 +770,9 @@ private:
     SampleType* const* channels;
     ChannelCountType numChannels = 0;
     size_t startSample = 0, numSamples = 0;
+
+    template <typename OtherSampleType>
+    friend class AudioBlock;
 };
 
 } // namespace dsp

modules/juce_dsp/containers/juce_SIMDRegister.h

@@ -358,13 +358,6 @@ struct SIMDRegister
         return snapPointerToAlignment (ptr, SIMDRegisterSize);
     }
 
-   #ifndef DOXYGEN
-    static inline const ElementType* getNextSIMDAlignedPtr (const ElementType* ptr) noexcept
-    {
-        return snapPointerToAlignment (ptr, SIMDRegisterSize);
-    }
-   #endif
-
 private:
     static inline vMaskType JUCE_VECTOR_CALLTYPE toMaskType (vSIMDType a) noexcept
     {

modules/juce_dsp/frequency/juce_Convolution.cpp

@@ -718,7 +718,7 @@ struct Convolution::Pimpl  : private Thread
     /** Convolution processing handling interpolation between previous and new states
         of the convolution engines.
     */
-    void processSamples (const AudioBlock<float>& input, AudioBlock<float>& output)
+    void processSamples (const AudioBlock<const float>& input, AudioBlock<float>& output)
     {
         processFifo();
 
@@ -1197,7 +1197,7 @@ void Convolution::reset() noexcept
     pimpl->reset();
 }
 
-void Convolution::processSamples (const AudioBlock<float>& input, AudioBlock<float>& output, bool isBypassed) noexcept
+void Convolution::processSamples (const AudioBlock<const float>& input, AudioBlock<float>& output, bool isBypassed) noexcept
 {
     if (! isActive)
         return;

modules/juce_dsp/frequency/juce_Convolution.h

@@ -156,7 +156,7 @@ private:
     std::unique_ptr<Pimpl> pimpl;
 
     //==============================================================================
-    void processSamples (const AudioBlock<float>&, AudioBlock<float>&, bool isBypassed) noexcept;
+    void processSamples (const AudioBlock<const float>&, AudioBlock<float>&, bool isBypassed) noexcept;
 
     //==============================================================================
     double sampleRate;

modules/juce_dsp/native/juce_fallback_SIMDNativeOps.h

@@ -43,8 +43,8 @@ namespace SIMDInternal
     template <> struct MaskTypeFor <std::complex<float>>    { using type = uint32_t; };
     template <> struct MaskTypeFor <std::complex<double>>   { using type = uint64_t; };
 
-    template <typename Primitive> struct PrimitiveType                           { using type = Primitive; };
-    template <typename Primitive> struct PrimitiveType<std::complex<Primitive>>  { using type = Primitive; };
+    template <typename Primitive> struct PrimitiveType                           { using type = typename std::remove_cv<Primitive>::type; };
+    template <typename Primitive> struct PrimitiveType<std::complex<Primitive>>  { using type = typename std::remove_cv<Primitive>::type; };
 
     template <int n>    struct Log2Helper    { enum { value = Log2Helper<n/2>::value + 1 }; };
     template <>         struct Log2Helper<1> { enum { value = 0 }; };

modules/juce_dsp/processors/juce_FIRFilter_test.cpp

@@ -121,7 +121,7 @@ class FIRFilterTest : public UnitTest
         template <typename FloatType>
         static void run (FIR::Filter<FloatType>& filter, FloatType* src, FloatType* dst, size_t n)
         {
-            AudioBlock<FloatType> input  (&src, 1, n);
+            AudioBlock<const FloatType> input (&src, 1, n);
             AudioBlock<FloatType> output (&dst, 1, n);
             ProcessContextNonReplacing<FloatType> context (input, output);
 
@@ -151,7 +151,7 @@ class FIRFilterTest : public UnitTest
                 auto* src = input + i;
                 auto* dst = output + i;
 
-                AudioBlock<FloatType> inBlock  (&src, 1, len);
+                AudioBlock<const FloatType> inBlock (&src, 1, len);
                 AudioBlock<FloatType> outBlock (&dst, 1, len);
                 ProcessContextNonReplacing<FloatType> context (inBlock, outBlock);
 

modules/juce_dsp/processors/juce_ProcessContext.h

@@ -83,6 +83,7 @@ public:
     using SampleType     = ContextSampleType;
     /** The type of audio block that this context handles. */
     using AudioBlockType = AudioBlock<SampleType>;
+    using ConstAudioBlockType = AudioBlock<const SampleType>;
 
     /** Creates a ProcessContextReplacing that uses the given audio block.
         Note that the caller must not delete the block while it is still in use by this object!
@@ -93,10 +94,10 @@ public:
     ProcessContextReplacing (ProcessContextReplacing&&) = default;
 
     /** Returns the audio block to use as the input to a process function. */
-    const AudioBlockType& getInputBlock() const noexcept        { return ioBlock; }
+    const ConstAudioBlockType& getInputBlock() const noexcept   { return constBlock; }
 
     /** Returns the audio block to use as the output to a process function. */
-    AudioBlockType& getOutputBlock() const noexcept             { return const_cast<AudioBlockType&> (ioBlock); }
+    AudioBlockType& getOutputBlock() const noexcept             { return ioBlock; }
 
     /** All process context classes will define this constant method so that templated
         code can determine whether the input and output blocks refer to the same buffer,
@@ -111,6 +112,7 @@ public:
 
 private:
     AudioBlockType& ioBlock;
+    ConstAudioBlockType constBlock { ioBlock };
 };
 
 //==============================================================================
@@ -134,11 +136,12 @@ public:
     using SampleType     = ContextSampleType;
     /** The type of audio block that this context handles. */
     using AudioBlockType = AudioBlock<SampleType>;
+    using ConstAudioBlockType = AudioBlock<const SampleType>;
 
     /** Creates a ProcessContextReplacing that uses the given input and output blocks.
         Note that the caller must not delete these blocks while they are still in use by this object!
     */
-    ProcessContextNonReplacing (const AudioBlockType& input, AudioBlockType& output) noexcept
+    ProcessContextNonReplacing (const ConstAudioBlockType& input, AudioBlockType& output) noexcept
         : inputBlock (input), outputBlock (output)
     {
         // If the input and output blocks are the same then you should use
@@ -150,10 +153,10 @@ public:
     ProcessContextNonReplacing (ProcessContextNonReplacing&&) = default;
 
     /** Returns the audio block to use as the input to a process function. */
-    const AudioBlockType& getInputBlock() const noexcept        { return inputBlock; }
+    const ConstAudioBlockType& getInputBlock() const noexcept   { return inputBlock; }
 
     /** Returns the audio block to use as the output to a process function. */
-    AudioBlockType& getOutputBlock() const noexcept             { return const_cast<AudioBlockType&> (outputBlock); }
+    AudioBlockType& getOutputBlock() const noexcept             { return outputBlock; }
 
     /** All process context classes will define this constant method so that templated
         code can determine whether the input and output blocks refer to the same buffer,
@@ -167,7 +170,7 @@ public:
     bool isBypassed = false;
 
 private:
-    const AudioBlockType& inputBlock;
+    const ConstAudioBlockType& inputBlock;
     AudioBlockType& outputBlock;
 };
 

modules/juce_dsp/processors/juce_ProcessorDuplicator.h

@@ -89,8 +89,8 @@ private:
 
         size_t channel;
 
-        typename ProcessContext::AudioBlockType getInputBlock()  const noexcept       { return ProcessContext::getInputBlock().getSingleChannelBlock (channel); }
-        typename ProcessContext::AudioBlockType getOutputBlock() const noexcept       { return ProcessContext::getOutputBlock().getSingleChannelBlock (channel); }
+        typename ProcessContext::ConstAudioBlockType getInputBlock()  const noexcept       { return ProcessContext::getInputBlock() .getSingleChannelBlock (channel); }
+        typename ProcessContext::AudioBlockType      getOutputBlock() const noexcept       { return ProcessContext::getOutputBlock().getSingleChannelBlock (channel); }
     };
 
     juce::OwnedArray<MonoProcessorType> processors;