[libcamera-devel] [PATCH 5/8] libcamera: framebuffer_allocator: Get and return buffers

[Jacopo Mondi]

Add to the FrameBufferAllocator class two methods to get and
return buffers from the pool of buffers allocated for a Stream.

The two methods return pointer to the allocated buffers without
transferring ownership to the caller.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 include/libcamera/framebuffer_allocator.h |  5 ++
 src/libcamera/framebuffer_allocator.cpp   | 60 +++++++++++++++++++++--
 2 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/include/libcamera/framebuffer_allocator.h b/include/libcamera/framebuffer_allocator.h
index 2a4d538a0cb2..1f3f10d4ec03 100644
--- a/include/libcamera/framebuffer_allocator.h
+++ b/include/libcamera/framebuffer_allocator.h
@@ -9,6 +9,7 @@
 
 #include <map>
 #include <memory>
+#include <queue>
 #include <vector>
 
 namespace libcamera {
@@ -33,9 +34,13 @@ public:
 	bool allocated() const { return !buffers_.empty(); }
 	const std::vector<std::unique_ptr<FrameBuffer>> &buffers(Stream *stream) const;
 
+	FrameBuffer *getBuffer(Stream *stream);
+	void returnBuffer(Stream *stream, FrameBuffer *buffer);
+
 private:
 	std::shared_ptr<Camera> camera_;
 	std::map<Stream *, std::vector<std::unique_ptr<FrameBuffer>>> buffers_;
+	std::map<Stream *, std::queue<FrameBuffer *>> availableBuffers_;
 };
 
 } /* namespace libcamera */
diff --git a/src/libcamera/framebuffer_allocator.cpp b/src/libcamera/framebuffer_allocator.cpp
index 7ed80011c845..7429d6b9edb7 100644
--- a/src/libcamera/framebuffer_allocator.cpp
+++ b/src/libcamera/framebuffer_allocator.cpp
@@ -64,7 +64,7 @@ FrameBufferAllocator::FrameBufferAllocator(std::shared_ptr<Camera> camera)
 
 FrameBufferAllocator::~FrameBufferAllocator()
 {
-	buffers_.clear();
+	clear();
 }
 
 /**
@@ -93,11 +93,17 @@ int FrameBufferAllocator::allocate(Stream *stream)
 	}
 
 	int ret = camera_->exportFrameBuffers(stream, &buffers_[stream]);
-	if (ret == -EINVAL)
+	if (ret == -EINVAL) {
 		LOG(Allocator, Error)
 			<< "Stream is not part of " << camera_->id()
 			<< " active configuration";
-	return ret;
+		return ret;
+	}
+
+	for (const auto &buffer : buffers_[stream])
+		availableBuffers_[stream].push(buffer.get());
+
+	return 0;
 }
 
 /**
@@ -122,6 +128,9 @@ int FrameBufferAllocator::free(Stream *stream)
 	buffers.clear();
 	buffers_.erase(iter);
 
+	availableBuffers_[stream] = {};
+	availableBuffers_.erase(availableBuffers_.find(stream));
+
 	return 0;
 }
 
@@ -131,6 +140,7 @@ int FrameBufferAllocator::free(Stream *stream)
 void FrameBufferAllocator::clear()
 {
 	buffers_.clear();
+	availableBuffers_.clear();
 }
 
 /**
@@ -162,4 +172,48 @@ FrameBufferAllocator::buffers(Stream *stream) const
 	return iter->second;
 }
 
+/**
+ * \brief Get a pointer to a \a buffer for the \a stream
+ * \param[in] stream The stream to get a buffer for
+ *
+ * The method returns a pointer to a FrameBuffer but does transfer the buffer
+ * ownership to the caller: the returned pointer remains valid until the
+ * FrameBufferAllocator does not get deleted or the allocated buffers do not get
+ * released with a call for free() or clear().
+ *
+ * \return A FrameBuffer pointer or nullptr if the no buffers is available
+ */
+FrameBuffer *FrameBufferAllocator::getBuffer(Stream *stream)
+{
+	if (!allocated() || buffers_[stream].empty())
+		return nullptr;
+
+	FrameBuffer *frameBuffer = availableBuffers_[stream].front();
+	availableBuffers_[stream].pop();
+
+	return frameBuffer;
+}
+
+/**
+ * \brief Return a \a buffer to the list of buffers available for the a \a stream
+ * \param[in] stream The stream to return buffer to
+ * \param[in] buffer The buffer to return
+ */
+void FrameBufferAllocator::returnBuffer(Stream *stream, FrameBuffer *buffer)
+{
+	if (!allocated())
+		return;
+
+	for (const auto &b : buffers_[stream]) {
+		/*
+		 * Return the buffer to the available queue only if it was part
+		 * of the vector of buffers allocated for the Stream.
+		 */
+		if (b.get() != buffer)
+			continue;
+
+		availableBuffers_[stream].push(buffer);
+	}
+}
+
 } /* namespace libcamera */
-- 
2.28.0