Add a zeroInitialise() method to the Portable objects and collections

Add a zeroInitialise() method to the PortableObject and PortableCollection
templates that erases the data in the Buffer by writing zeros (bytes
containing '\0') to it.

On the host, zeroInitialise() can be called without arguments to execute
immediately, or with a queue to be run asynchronously.

On the device, zeroInitialise() requires a queue and can only be run
asynchronously.

Author: fwyzard

DataFormats/Portable/interface/PortableDeviceCollection.h

@@ -70,6 +70,12 @@ class PortableDeviceCollection {
   ConstBuffer buffer() const { return *buffer_; }
   ConstBuffer const_buffer() const { return *buffer_; }
 
+  // erases the data in the Buffer by writing zeros (bytes containing '\0') to it
+  template <typename TQueue, typename = std::enable_if_t<alpaka::isQueue<TQueue>>>
+  void zeroInitialise(TQueue&& queue) {
+    alpaka::memset(std::forward<TQueue>(queue), *buffer_, 0x00);
+  }
+
 private:
   std::optional<Buffer> buffer_;  //!
   Layout layout_;                 //
@@ -275,7 +281,13 @@ class PortableDeviceMultiCollection {
   ConstBuffer buffer() const { return *buffer_; }
   ConstBuffer const_buffer() const { return *buffer_; }
 
-  // Extract the sizes array
+  // erases the data in the Buffer by writing zeros (bytes containing '\0') to it
+  template <typename TQueue, typename = std::enable_if_t<alpaka::isQueue<TQueue>>>
+  void zeroInitialise(TQueue&& queue) {
+    alpaka::memset(std::forward<TQueue>(queue), *buffer_, 0x00);
+  }
+
+  // extract the sizes array
   SizesArray sizes() const {
     SizesArray ret;
     portablecollection::constexpr_for<0, members_>([&](auto i) { ret[i] = get<i>().layout_.metadata().size(); });

DataFormats/Portable/interface/PortableDeviceObject.h

@@ -50,9 +50,11 @@ class PortableDeviceObject {
   // access the product
   Product& value() { return *buffer_->data(); }
   Product const& value() const { return *buffer_->data(); }
+  Product const& const_value() const { return *buffer_->data(); }
 
   Product* data() { return buffer_->data(); }
   Product const* data() const { return buffer_->data(); }
+  Product const* const_data() const { return buffer_->data(); }
 
   Product& operator*() { return *buffer_->data(); }
   Product const& operator*() const { return *buffer_->data(); }
@@ -65,6 +67,12 @@ class PortableDeviceObject {
   ConstBuffer buffer() const { return *buffer_; }
   ConstBuffer const_buffer() const { return *buffer_; }
 
+  // erases the data in the Buffer by writing zeros (bytes containing '\0') to it
+  template <typename TQueue, typename = std::enable_if_t<alpaka::isQueue<TQueue>>>
+  void zeroInitialise(TQueue&& queue) {
+    alpaka::memset(std::forward<TQueue>(queue), *buffer_, 0x00);
+  }
+
 private:
   std::optional<Buffer> buffer_;
 };

DataFormats/Portable/interface/PortableHostCollection.h

@@ -69,6 +69,16 @@ class PortableHostCollection {
   ConstBuffer buffer() const { return *buffer_; }
   ConstBuffer const_buffer() const { return *buffer_; }
 
+  // erases the data in the Buffer by writing zeros (bytes containing '\0') to it
+  void zeroInitialise() {
+    std::memset(std::data(*buffer_), 0x00, alpaka::getExtentProduct(*buffer_) * sizeof(std::byte));
+  }
+
+  template <typename TQueue, typename = std::enable_if_t<alpaka::isQueue<TQueue>>>
+  void zeroInitialise(TQueue&& queue) {
+    alpaka::memset(std::forward<TQueue>(queue), *buffer_, 0x00);
+  }
+
   // part of the ROOT read streamer
   static void ROOTReadStreamer(PortableHostCollection* newObj, Layout& layout) {
     // destroy the default-constructed collection
@@ -278,12 +288,23 @@ class PortableHostMultiCollection {
   ConstBuffer buffer() const { return *buffer_; }
   ConstBuffer const_buffer() const { return *buffer_; }
 
-  // Extract the sizes array
+  // erases the data in the Buffer by writing zeros (bytes containing '\0') to it
+  void zeroInitialise() {
+    std::memset(std::data(*buffer_), 0x00, alpaka::getExtentProduct(*buffer_) * sizeof(std::byte));
+  }
+
+  template <typename TQueue, typename = std::enable_if_t<alpaka::isQueue<TQueue>>>
+  void zeroInitialise(TQueue&& queue) {
+    alpaka::memset(std::forward<TQueue>(queue), *buffer_, 0x00);
+  }
+
+  // extract the sizes array
   SizesArray sizes() const {
     SizesArray ret;
     portablecollection::constexpr_for<0, members_>([&](auto i) { ret[i] = get<i>().layout_.metadata().size(); });
     return ret;
   }
+
   // part of the ROOT read streamer
   static void ROOTReadStreamer(PortableHostMultiCollection* newObj, Implementation& onfileImpl) {
     newObj->~PortableHostMultiCollection();

DataFormats/Portable/interface/PortableHostObject.h

@@ -48,9 +48,11 @@ class PortableHostObject {
   // access the product
   Product& value() { return *product_; }
   Product const& value() const { return *product_; }
+  Product const& const_value() const { return *product_; }
 
   Product* data() { return product_; }
   Product const* data() const { return product_; }
+  Product const* const_data() const { return product_; }
 
   Product& operator*() { return *product_; }
   Product const& operator*() const { return *product_; }
@@ -63,6 +65,16 @@ class PortableHostObject {
   ConstBuffer buffer() const { return *buffer_; }
   ConstBuffer const_buffer() const { return *buffer_; }
 
+  // erases the data in the Buffer by writing zeros (bytes containing '\0') to it
+  void zeroInitialise() {
+    std::memset(std::data(*buffer_), 0x00, alpaka::getExtentProduct(*buffer_) * sizeof(std::byte));
+  }
+
+  template <typename TQueue, typename = std::enable_if_t<alpaka::isQueue<TQueue>>>
+  void zeroInitialise(TQueue&& queue) {
+    alpaka::memset(std::forward<TQueue>(queue), *buffer_, 0x00);
+  }
+
   // part of the ROOT read streamer
   static void ROOTReadStreamer(PortableHostObject* newObj, Product& product) {
     // destroy the default-constructed object