From 50efcfc95afbb7d3d81026797c667751b243e42a Mon Sep 17 00:00:00 2001
From: Jean Pierre Cimalando <jp-dev@inbox.ru>
Date: Thu, 11 Jun 2020 02:54:10 +0200
Subject: [PATCH] Support fixed padding for AudioBuffer

---
 src/sfizz/AudioBuffer.h | 41 ++++++++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/src/sfizz/AudioBuffer.h b/src/sfizz/AudioBuffer.h
index 51500d0a..011e5a70 100644
--- a/src/sfizz/AudioBuffer.h
+++ b/src/sfizz/AudioBuffer.h
@@ -26,7 +26,9 @@ namespace sfz
  * @tparam MaxChannels the maximum number of channels in the buffer
  * @tparam Alignment the alignment for the buffers
  */
-template <class Type, size_t MaxChannels = sfz::config::numChannels, unsigned int Alignment = SIMDConfig::defaultAlignment>
+template <class Type, size_t MaxChannels = sfz::config::numChannels,
+          unsigned int Alignment = SIMDConfig::defaultAlignment,
+          size_t PaddingLeft_ = 0, size_t PaddingRight = 0>
 class AudioBuffer {
 public:
     using value_type = typename std::remove_cv<Type>::type;
@@ -35,6 +37,13 @@ public:
     using iterator = pointer;
     using const_iterator = const_pointer;
 
+    enum {
+        //! Increased left padding to preserve required alignment
+        PaddingLeft = PaddingLeft_ + (Alignment - (PaddingLeft_ % Alignment)) % Alignment,
+        //! Total padding left and right
+        PaddingTotal = PaddingLeft + PaddingRight,
+    };
+
     /**
      * @brief Construct a new Audio Buffer object
      *
@@ -55,7 +64,7 @@ public:
         , numFrames(numFrames)
     {
         for (size_t i = 0; i < numChannels; ++i)
-            buffers[i] = absl::make_unique<buffer_type>(numFrames);
+            buffers[i] = absl::make_unique<buffer_type>(numFrames + PaddingTotal);
     }
 
     /**
@@ -70,7 +79,7 @@ public:
         bool returnedOK = true;
 
         for (size_t i = 0; i < numChannels; ++i)
-            returnedOK &= buffers[i]->resize(newSize, std::nothrow);
+            returnedOK &= buffers[i]->resize(newSize + PaddingTotal, std::nothrow);
 
         if (returnedOK)
             numFrames = newSize;
@@ -86,7 +95,7 @@ public:
     void resize(size_t newSize)
     {
         for (size_t i = 0; i < numChannels; ++i)
-            buffers[i]->resize(newSize);
+            buffers[i]->resize(newSize + PaddingTotal);
 
         numFrames = newSize;
     }
@@ -101,7 +110,7 @@ public:
     {
         ASSERT(channelIndex < numChannels);
         if (channelIndex < numChannels)
-            return buffers[channelIndex]->data();
+            return buffers[channelIndex]->data() + PaddingLeft;
 
         return {};
     }
@@ -116,7 +125,7 @@ public:
     {
         ASSERT(channelIndex < numChannels);
         if (channelIndex < numChannels)
-            return buffers[channelIndex]->end();
+            return buffers[channelIndex]->end() - PaddingRight;
 
         return {};
     }
@@ -131,7 +140,7 @@ public:
     {
         ASSERT(channelIndex < numChannels);
         if (channelIndex < numChannels)
-            return buffers[channelIndex]->data();
+            return buffers[channelIndex]->data() + PaddingLeft;
 
         return {};
     }
@@ -146,7 +155,7 @@ public:
     {
         ASSERT(channelIndex < numChannels);
         if (channelIndex < numChannels)
-            return buffers[channelIndex]->end();
+            return buffers[channelIndex]->end() - PaddingRight;
 
         return {};
     }
@@ -161,7 +170,7 @@ public:
     {
         ASSERT(channelIndex < numChannels);
         if (channelIndex < numChannels)
-            return { buffers[channelIndex]->data(), buffers[channelIndex]->size() };
+            return { buffers[channelIndex]->data() + PaddingLeft, numFrames };
 
         return {};
     }
@@ -184,7 +193,7 @@ public:
     void addChannel()
     {
         if (numChannels < MaxChannels)
-            buffers[numChannels++] = absl::make_unique<buffer_type>(numFrames);
+            buffers[numChannels++] = absl::make_unique<buffer_type>(numFrames + PaddingTotal);
     }
 
     /**
@@ -233,7 +242,7 @@ public:
         ASSERT(buffers[channelIndex] != nullptr);
         ASSERT(frameIndex < numFrames);
 
-        return *(buffers[channelIndex]->data() + frameIndex);
+        return *(buffers[channelIndex]->data() + PaddingLeft + frameIndex);
     }
 
     /**
@@ -265,8 +274,10 @@ public:
      */
     void clear()
     {
-        for (size_t i = 0; i < numChannels; ++i)
-            fill<Type>(getSpan(i), Type{ 0.0 });
+        for (size_t i = 0; i < numChannels; ++i) {
+            absl::Span<Type> paddedSpan { buffers[i]->data(), numFrames + PaddingTotal };
+            fill<Type>(paddedSpan, Type{ 0.0 });
+        }
     }
 
     /**
@@ -284,7 +295,7 @@ public:
     /**
      * @brief Convert implicitly to a pointer of channels
      */
-    operator const float* const*() const noexcept
+    operator const Type* const*() const noexcept
     {
         return buffers.data();
     }
@@ -292,7 +303,7 @@ public:
     /**
      * @brief Convert implicitly to a pointer of channels
      */
-    operator float* const*() noexcept
+    operator Type* const*() noexcept
     {
         return buffers.data();
     }