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libcamera: camera: Handle camera objects through shared pointers

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The Camera class is explicitly reference-counted to manage the lifetime
of camera objects. Replace this open-coded implementation with usage of
the std::shared_ptr<> class.

This API change prevents pipeline handlers from subclassing the Camera
class. This isn't deemed to be an issue. Mark the class final to make
this explicit.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
This commit is contained in:
Laurent Pinchart
2019-01-17 16:23:25 +02:00
parent f3695e9b09
commit 21ff749a79
6 changed files with 54 additions and 45 deletions
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46
src/libcamera/camera.cpp
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@@ -41,19 +41,36 @@ namespace libcamera {
* streams from a single image source. It provides the main interface to
* configuring and controlling the device, and capturing image streams. It is
* the central object exposed by libcamera.
*
* To support the central nature of Camera objects, libcamera manages the
* lifetime of camera instances with std::shared_ptr<>. Instances shall be
* created with the create() function which returns a shared pointer. The
* Camera constructors and destructor are private, to prevent instances from
* being constructed and destroyed manually.
*/
/**
* \brief Construct a named camera device
* \brief Create a camera instance
* \param[in] name The name of the camera device
*
* \param[in] name The name to set on the camera device
* The caller is responsible for guaranteeing unicity of the camera name.
*
* The caller is responsible for guaranteeing unicity of the camera
* device name.
* \return A shared pointer to the newly created camera object
*/
Camera::Camera(const std::string &name)
: ref_(1), name_(name)
std::shared_ptr<Camera> Camera::create(const std::string &name)
{
struct Allocator : std::allocator<Camera> {
void construct(void *p, const std::string &name)
{
::new(p) Camera(name);
}
void destroy(Camera *p)
{
p->~Camera();
}
};
return std::allocate_shared<Camera>(Allocator(), name);
}
/**
@@ -66,24 +83,13 @@ const std::string &Camera::name() const
return name_;
}
/**
* \brief Acquire a reference to the camera
*/
void Camera::get()
Camera::Camera(const std::string &name)
: name_(name)
{
ref_++;
}
/**
* \brief Release a reference to the camera
*
* When the last reference is released the camera device is deleted. Callers
* shall not access the camera device after calling this function.
*/
void Camera::put()
Camera::~Camera()
{
if (--ref_ == 0)
delete this;
}
} /* namespace libcamera */