gst_plugin/

element.rs

// Copyright (C) 2017 Sebastian Dröge <sebastian@centricular.com>
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use std::any::Any;
use std::mem;
use std::ptr;

use libc;

use glib_ffi;
use gobject_ffi;
use gst_ffi;

use glib;
use glib::translate::*;
use gst;
use gst::prelude::*;

use gobject_subclass::anyimpl::*;
use gobject_subclass::object::*;

use object::*;

pub trait ElementImpl<T: ElementBase>: ObjectImpl<T> + AnyImpl + Send + Sync + 'static
where
    T::InstanceStructType: PanicPoison,
{
    fn change_state(&self, element: &T, transition: gst::StateChange) -> gst::StateChangeReturn {
        element.parent_change_state(transition)
    }

    fn request_new_pad(
        &self,
        _element: &T,
        _templ: &gst::PadTemplate,
        _name: Option<String>,
        _caps: Option<&gst::CapsRef>,
    ) -> Option<gst::Pad> {
        None
    }

    fn release_pad(&self, _element: &T, _pad: &gst::Pad) {}

    fn send_event(&self, element: &T, event: gst::Event) -> bool {
        element.parent_send_event(event)
    }

    fn query(&self, element: &T, query: &mut gst::QueryRef) -> bool {
        element.parent_query(query)
    }

    fn set_context(&self, element: &T, context: &gst::Context) {
        element.parent_set_context(context)
    }
}

pub trait ElementImplExt<T> {
    fn catch_panic_pad_function<R, F: FnOnce(&Self, &T) -> R, G: FnOnce() -> R>(
        parent: &Option<gst::Object>,
        fallback: G,
        f: F,
    ) -> R;
}

impl<S: ElementImpl<T>, T: ObjectType + glib::IsA<gst::Element> + glib::IsA<gst::Object>>
    ElementImplExt<T> for S
where
    T::InstanceStructType: PanicPoison,
{
    fn catch_panic_pad_function<R, F: FnOnce(&Self, &T) -> R, G: FnOnce() -> R>(
        parent: &Option<gst::Object>,
        fallback: G,
        f: F,
    ) -> R {
        // FIXME: Does this work for element subclasses?
        let element = parent.as_ref().unwrap().downcast_ref::<T>().unwrap();
        let imp = element.get_impl();
        let imp = Any::downcast_ref::<Box<ElementImpl<T> + 'static>>(imp).unwrap();
        let imp = imp.downcast_ref::<S>().unwrap();
        element.catch_panic(fallback, |element| f(imp, element))
    }
}

any_impl!(ElementBase, ElementImpl, PanicPoison);

pub unsafe trait ElementBase: IsA<gst::Element> + ObjectType
where
    Self::InstanceStructType: PanicPoison,
{
    fn parent_change_state(&self, transition: gst::StateChange) -> gst::StateChangeReturn {
        unsafe {
            let klass = self.get_class();
            let parent_klass = (*klass).get_parent_class() as *const gst_ffi::GstElementClass;
            (*parent_klass)
                .change_state
                .map(|f| from_glib(f(self.to_glib_none().0, transition.to_glib())))
                .unwrap_or(gst::StateChangeReturn::Success)
        }
    }

    fn parent_send_event(&self, event: gst::Event) -> bool {
        unsafe {
            let klass = self.get_class();
            let parent_klass = (*klass).get_parent_class() as *const gst_ffi::GstElementClass;
            (*parent_klass)
                .send_event
                .map(|f| from_glib(f(self.to_glib_none().0, event.into_ptr())))
                .unwrap_or(false)
        }
    }

    fn parent_query(&self, query: &mut gst::QueryRef) -> bool {
        unsafe {
            let klass = self.get_class();
            let parent_klass = (*klass).get_parent_class() as *const gst_ffi::GstElementClass;
            (*parent_klass)
                .query
                .map(|f| from_glib(f(self.to_glib_none().0, query.as_mut_ptr())))
                .unwrap_or(false)
        }
    }

    fn parent_set_context(&self, context: &gst::Context) {
        unsafe {
            let klass = self.get_class();
            let parent_klass = (*klass).get_parent_class() as *const gst_ffi::GstElementClass;
            (*parent_klass)
                .set_context
                .map(|f| f(self.to_glib_none().0, context.to_glib_none().0))
                .unwrap_or(())
        }
    }

    fn catch_panic<T, F: FnOnce(&Self) -> T, G: FnOnce() -> T>(&self, fallback: G, f: F) -> T {
        let panicked = unsafe { &(*self.get_instance()).panicked() };
        panic_to_error!(self, panicked, fallback(), { f(self) })
    }
}

pub unsafe trait ElementClassExt<T: ElementBase>
where
    T::ImplType: ElementImpl<T>,
    T::InstanceStructType: PanicPoison,
{
    fn add_pad_template(&mut self, pad_template: gst::PadTemplate) {
        unsafe {
            gst_ffi::gst_element_class_add_pad_template(
                self as *const Self as *mut gst_ffi::GstElementClass,
                pad_template.to_glib_none().0,
            );
        }
    }

    fn set_metadata(
        &mut self,
        long_name: &str,
        classification: &str,
        description: &str,
        author: &str,
    ) {
        unsafe {
            gst_ffi::gst_element_class_set_metadata(
                self as *const Self as *mut gst_ffi::GstElementClass,
                long_name.to_glib_none().0,
                classification.to_glib_none().0,
                description.to_glib_none().0,
                author.to_glib_none().0,
            );
        }
    }

    fn override_vfuncs(&mut self, _: &ClassInitToken) {
        unsafe {
            let klass = &mut *(self as *const Self as *mut gst_ffi::GstElementClass);
            klass.change_state = Some(element_change_state::<T>);
            klass.request_new_pad = Some(element_request_new_pad::<T>);
            klass.release_pad = Some(element_release_pad::<T>);
            klass.send_event = Some(element_send_event::<T>);
            klass.query = Some(element_query::<T>);
            klass.set_context = Some(element_set_context::<T>);
        }
    }
}

glib_wrapper! {
    pub struct Element(Object<ElementInstanceStruct<Element>>):
        [gst::Element => gst_ffi::GstElement,
         gst::Object => gst_ffi::GstObject];

    match fn {
        get_type => || get_type::<Element>(),
    }
}

unsafe impl<T: IsA<gst::Element> + ObjectType> ElementBase for T where
    Self::InstanceStructType: PanicPoison
{
}

pub type ElementClass = ClassStruct<Element>;

// FIXME: Boilerplate
unsafe impl ElementClassExt<Element> for ElementClass {}
unsafe impl ObjectClassExt<Element> for ElementClass {}

unsafe impl Send for Element {}
unsafe impl Sync for Element {}

#[macro_export]
macro_rules! box_element_impl(
    ($name:ident) => {
        box_object_impl!($name, PanicPoison);

        impl<T: ElementBase> ElementImpl<T> for Box<$name<T>>
        where
            T::InstanceStructType: PanicPoison
        {
            fn change_state(
                &self,
                element: &T,
                transition: gst::StateChange,
            ) -> gst::StateChangeReturn {
                let imp: &$name<T> = self.as_ref();
                imp.change_state(element, transition)
            }

            fn request_new_pad(&self, element: &T, templ: &gst::PadTemplate, name: Option<String>, caps: Option<&gst::CapsRef>) -> Option<gst::Pad> {
                let imp: &$name<T> = self.as_ref();
                imp.request_new_pad(element, templ, name, caps)
            }

            fn release_pad(&self, element: &T, pad: &gst::Pad) {
                let imp: &$name<T> = self.as_ref();
                imp.release_pad(element, pad)
            }

            fn send_event(&self, element: &T, event: gst::Event) -> bool {
                let imp: &$name<T> = self.as_ref();
                imp.send_event(element, event)
            }

            fn query(&self, element: &T, query: &mut gst::QueryRef) -> bool {
                let imp: &$name<T> = self.as_ref();
                ElementImpl::query(imp, element, query)
            }

            fn set_context(&self, element: &T, context: &gst::Context) {
                let imp: &$name<T> = self.as_ref();
                imp.set_context(element, context)
            }
        }
    };
);

box_element_impl!(ElementImpl);

impl ObjectType for Element {
    const NAME: &'static str = "RsElement";
    type ParentType = gst::Element;
    type ImplType = Box<ElementImpl<Self>>;
    type InstanceStructType = ElementInstanceStruct<Self>;

    fn class_init(token: &ClassInitToken, klass: &mut ElementClass) {
        ObjectClassExt::override_vfuncs(klass, token);
        ElementClassExt::override_vfuncs(klass, token);
    }

    object_type_fns!();
}

unsafe extern "C" fn element_change_state<T: ElementBase>(
    ptr: *mut gst_ffi::GstElement,
    transition: gst_ffi::GstStateChange,
) -> gst_ffi::GstStateChangeReturn
where
    T::ImplType: ElementImpl<T>,
    T::InstanceStructType: PanicPoison,
{
    floating_reference_guard!(ptr);
    let element = &*(ptr as *mut T::InstanceStructType);
    let wrap: T = from_glib_borrow(ptr as *mut T::InstanceStructType);
    let imp = element.get_impl();

    // *Never* fail downwards state changes, this causes bugs in GStreamer
    // and leads to crashes and deadlocks.
    let transition = from_glib(transition);
    let fallback = match transition {
        gst::StateChange::PlayingToPaused
        | gst::StateChange::PausedToReady
        | gst::StateChange::ReadyToNull => gst::StateChangeReturn::Success,
        _ => gst::StateChangeReturn::Failure,
    };

    panic_to_error!(&wrap, &element.panicked(), fallback, {
        imp.change_state(&wrap, transition)
    })
    .to_glib()
}

unsafe extern "C" fn element_request_new_pad<T: ElementBase>(
    ptr: *mut gst_ffi::GstElement,
    templ: *mut gst_ffi::GstPadTemplate,
    name: *const libc::c_char,
    caps: *const gst_ffi::GstCaps,
) -> *mut gst_ffi::GstPad
where
    T::ImplType: ElementImpl<T>,
    T::InstanceStructType: PanicPoison,
{
    floating_reference_guard!(ptr);
    let element = &*(ptr as *mut T::InstanceStructType);
    let wrap: T = from_glib_borrow(ptr as *mut T::InstanceStructType);
    let imp = element.get_impl();
    let caps = if caps.is_null() {
        None
    } else {
        Some(gst::CapsRef::from_ptr(caps))
    };

    // XXX: This is effectively unsafe but the best we can do
    // See https://bugzilla.gnome.org/show_bug.cgi?id=791193
    let pad = panic_to_error!(&wrap, &element.panicked(), None, {
        imp.request_new_pad(&wrap, &from_glib_borrow(templ), from_glib_none(name), caps)
    });

    // Ensure that the pad is owned by the element now, if a pad was returned
    if let Some(ref pad) = pad {
        assert_eq!(
            pad.get_parent(),
            Some(gst::Object::from_glib_borrow(
                ptr as *mut gst_ffi::GstObject
            ))
        );
    }

    pad.to_glib_none().0
}

unsafe extern "C" fn element_release_pad<T: ElementBase>(
    ptr: *mut gst_ffi::GstElement,
    pad: *mut gst_ffi::GstPad,
) where
    T::ImplType: ElementImpl<T>,
    T::InstanceStructType: PanicPoison,
{
    floating_reference_guard!(ptr);
    let element = &*(ptr as *mut T::InstanceStructType);
    let wrap: T = from_glib_borrow(ptr as *mut T::InstanceStructType);
    let imp = element.get_impl();

    panic_to_error!(&wrap, &element.panicked(), (), {
        imp.release_pad(&wrap, &from_glib_borrow(pad))
    })
}

unsafe extern "C" fn element_send_event<T: ElementBase>(
    ptr: *mut gst_ffi::GstElement,
    event: *mut gst_ffi::GstEvent,
) -> glib_ffi::gboolean
where
    T::ImplType: ElementImpl<T>,
    T::InstanceStructType: PanicPoison,
{
    floating_reference_guard!(ptr);
    let element = &*(ptr as *mut T::InstanceStructType);
    let wrap: T = from_glib_borrow(ptr as *mut T::InstanceStructType);
    let imp = element.get_impl();

    panic_to_error!(&wrap, &element.panicked(), false, {
        imp.send_event(&wrap, from_glib_full(event))
    })
    .to_glib()
}

unsafe extern "C" fn element_query<T: ElementBase>(
    ptr: *mut gst_ffi::GstElement,
    query: *mut gst_ffi::GstQuery,
) -> glib_ffi::gboolean
where
    T::ImplType: ElementImpl<T>,
    T::InstanceStructType: PanicPoison,
{
    floating_reference_guard!(ptr);
    let element = &*(ptr as *mut T::InstanceStructType);
    let wrap: T = from_glib_borrow(ptr as *mut T::InstanceStructType);
    let imp = element.get_impl();
    let query = gst::QueryRef::from_mut_ptr(query);

    panic_to_error!(&wrap, &element.panicked(), false, {
        imp.query(&wrap, query)
    })
    .to_glib()
}

unsafe extern "C" fn element_set_context<T: ElementBase>(
    ptr: *mut gst_ffi::GstElement,
    context: *mut gst_ffi::GstContext,
) where
    T::ImplType: ElementImpl<T>,
    T::InstanceStructType: PanicPoison,
{
    floating_reference_guard!(ptr);
    let element = &*(ptr as *mut T::InstanceStructType);
    let wrap: T = from_glib_borrow(ptr as *mut T::InstanceStructType);
    let imp = element.get_impl();

    panic_to_error!(&wrap, &element.panicked(), (), {
        imp.set_context(&wrap, &from_glib_borrow(context))
    })
}