From 5a4eaafdacb48f2709d2fabdd3a10f9635e23d2b Mon Sep 17 00:00:00 2001
From: Emilio Perez <emiliopeju@gmail.com>
Date: Thu, 19 Oct 2023 17:03:19 +0100
Subject: [PATCH] Provide a way to override frame memory allocation

It can be done local to a `NDArrayPool` by overriding `frameMalloc` and
`frameFree`.
It can also be also done globally by using the static method
`setDefaultFrameMemoryFunctions`
---
 ADApp/ADSrc/NDArray.cpp     |  9 ++++++--
 ADApp/ADSrc/NDArray.h       |  9 ++++++++
 ADApp/ADSrc/NDArrayPool.cpp | 43 +++++++++++++++++++++++++++++++++++--
 3 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/ADApp/ADSrc/NDArray.cpp b/ADApp/ADSrc/NDArray.cpp
index 2447a9bc6..257d5de7e 100644
--- a/ADApp/ADSrc/NDArray.cpp
+++ b/ADApp/ADSrc/NDArray.cpp
@@ -64,7 +64,7 @@ NDArray::NDArray(int nDims, size_t *dims, NDDataType_t dataType, size_t dataSize
   if (pData) {
     this->pData = pData;
   } else {
-    this->pData = malloc(dataSize);
+    this->pData = defaultFrameMalloc(dataSize);
     this->dataSize = dataSize;
   }
 }
@@ -73,7 +73,12 @@ NDArray::NDArray(int nDims, size_t *dims, NDDataType_t dataType, size_t dataSize
   * Frees the data array, deletes all attributes, frees the attribute list and destroys the mutex. */
 NDArray::~NDArray()
 {
-  if (this->pData) free(this->pData);
+  if (this->pData) {
+      if (this->pNDArrayPool)
+        this->pNDArrayPool->frameFree(this->pData);
+      else
+        defaultFrameFree(this->pData);
+  }
   delete this->pAttributeList;
 }
 
diff --git a/ADApp/ADSrc/NDArray.h b/ADApp/ADSrc/NDArray.h
index f7ad79b69..43868b740 100644
--- a/ADApp/ADSrc/NDArray.h
+++ b/ADApp/ADSrc/NDArray.h
@@ -25,6 +25,11 @@
 /** The maximum number of dimensions in an NDArray */
 #define ND_ARRAY_MAX_DIMS 10
 
+typedef void *(*MallocFunc_t)(size_t size);
+typedef void (*FreeFunc_t)(void *ptr);
+extern MallocFunc_t defaultFrameMalloc;
+extern FreeFunc_t defaultFrameFree;
+
 /** Enumeration of color modes for NDArray attribute "colorMode" */
 typedef enum
 {
@@ -182,6 +187,10 @@ class ADCORE_API NDArrayPool {
     size_t       getMemorySize();
     int          getNumFree();
     void         emptyFreeList();
+    static void  setDefaultFrameMemoryFunctions(MallocFunc_t newMalloc,
+                                                FreeFunc_t newFree);
+    virtual void* frameMalloc(size_t size);
+    virtual void frameFree(void *ptr);
 
 protected:
     /** The following methods should be implemented by a pool class
diff --git a/ADApp/ADSrc/NDArrayPool.cpp b/ADApp/ADSrc/NDArrayPool.cpp
index b28122e53..bea77dad8 100644
--- a/ADApp/ADSrc/NDArrayPool.cpp
+++ b/ADApp/ADSrc/NDArrayPool.cpp
@@ -29,6 +29,10 @@
 
 static const char *driverName = "NDArrayPool";
 
+// This provides a way of overriding the default memory functions for frame
+// buffer allocation and freeing
+MallocFunc_t defaultFrameMalloc = malloc;
+FreeFunc_t defaultFrameFree = free;
 
 /** eraseNDAttributes is a global flag the controls whether NDArray::clearAttributes() is called
   * each time a new array is allocated with NDArrayPool->alloc().
@@ -53,6 +57,41 @@ NDArrayPool::NDArrayPool(class asynNDArrayDriver *pDriver, size_t maxMemory)
   listLock_ = epicsMutexCreate();
 }
 
+/** Set default frame buffer allocation and deallocation functions
+  * \param[in] newMalloc Pointer to a function that will be used by default to
+  *            allocate a frame buffer
+  * \param[in] newFree Pointer to a function that will be used by default to
+  *            deallocate a frame buffer
+ * **/
+void NDArrayPool::setDefaultFrameMemoryFunctions(
+    MallocFunc_t newMalloc, FreeFunc_t newFree)
+{
+    if (newMalloc)
+        defaultFrameMalloc = newMalloc;
+
+    if (newFree)
+        defaultFrameFree = newFree;
+}
+
+/** Used to allocate a frame buffer
+ * This method can be overriden in subclasses to use custom memory allocation
+  * \param[in] size Required buffer size
+  * Returns pointer to buffer of size specified
+ */
+void* NDArrayPool::frameMalloc(size_t size)
+{
+    return defaultFrameMalloc(size);
+}
+
+/** Used to free a frame buffer
+ * This method can be overriden in subclasses to use custom memory deallocation
+  * \param[in] ptr Pointer to memory that will be deallocated
+ */
+void NDArrayPool::frameFree(void *ptr)
+{
+    defaultFrameFree(ptr);
+}
+
 /** Create new NDArray object.
   * This method should be overriden by a pool class that manages objects
   * that derive from NDArray class.
@@ -139,7 +178,7 @@ NDArray* NDArrayPool::alloc(int ndims, size_t *dims, NDDataType_t dataType, size
     if (pData || (pListElement->dataSize_ > (dataSize * THRESHOLD_SIZE_RATIO))) {
       // We found an array but it is too large.  Set the size to 0 so it will be allocated below.
       memorySize_ -= pArray->dataSize;
-      free(pArray->pData);
+      frameFree(pArray->pData);
       pArray->pData = NULL;
     }
     freeList_.erase(pListElement);
@@ -193,7 +232,7 @@ NDArray* NDArrayPool::alloc(int ndims, size_t *dims, NDDataType_t dataType, size
              "%s: error: reached limit of %ld memory (%d buffers)\n",
              functionName, (long)maxMemory_, numBuffers_);
     } else {
-      pArray->pData = malloc(dataSize);
+      pArray->pData = frameMalloc(dataSize);
       if (pArray->pData) {
         pArray->dataSize = dataSize;
         pArray->compressedSize = dataSize;