gstreamer: Add gst::Allocator subclassing support

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1147>

gstreamer/src/allocation_params.rs

@@ -8,6 +8,7 @@ use crate::MemoryFlags;
 
 #[derive(Debug, Clone)]
 #[doc(alias = "GstAllocationParams")]
+#[repr(transparent)]
 pub struct AllocationParams(ffi::GstAllocationParams);
 
 unsafe impl Send for AllocationParams {}
@@ -36,7 +37,7 @@ impl AllocationParams {
 
     pub fn new(flags: MemoryFlags, align: usize, prefix: usize, padding: usize) -> Self {
         assert_initialized_main_thread!();
-        let allocationparams = unsafe {
+        let params = unsafe {
             ffi::GstAllocationParams {
                 flags: flags.into_glib(),
                 align,
@@ -46,7 +47,7 @@ impl AllocationParams {
             }
         };
 
-        AllocationParams(allocationparams)
+        params.into()
     }
 
     pub fn as_ptr(&self) -> *const ffi::GstAllocationParams {
@@ -74,6 +75,6 @@ impl FromGlib<ffi::GstAllocationParams> for AllocationParams {
     #[allow(unused_unsafe)]
     unsafe fn from_glib(value: ffi::GstAllocationParams) -> Self {
         assert_initialized_main_thread!();
-        AllocationParams(value)
+        Self::from(value)
     }
 }

gstreamer/src/subclass/allocator.rs

@@ -0,0 +1,187 @@
+// Take a look at the license at the top of the repository in the LICENSE file.
+
+use super::prelude::*;
+use crate::{AllocationParams, Allocator, Memory};
+use glib::{bool_error, prelude::*, subclass::prelude::*, translate::*, BoolError};
+use std::ptr;
+
+pub trait AllocatorImpl: AllocatorImplExt + GstObjectImpl + Send + Sync {
+    fn alloc(&self, size: usize, params: Option<&AllocationParams>) -> Result<Memory, BoolError> {
+        self.parent_alloc(size, params)
+    }
+
+    fn free(&self, memory: Memory) {
+        self.parent_free(memory)
+    }
+}
+
+pub trait AllocatorImplExt: ObjectSubclass {
+    fn parent_alloc(
+        &self,
+        size: usize,
+        params: Option<&AllocationParams>,
+    ) -> Result<Memory, BoolError>;
+
+    fn parent_free(&self, memory: Memory);
+}
+
+impl<T: AllocatorImpl> AllocatorImplExt for T {
+    fn parent_alloc(
+        &self,
+        size: usize,
+        params: Option<&AllocationParams>,
+    ) -> Result<Memory, BoolError> {
+        unsafe {
+            let data = Self::type_data();
+            let parent_class = data.as_ref().parent_class() as *mut ffi::GstAllocatorClass;
+
+            if let Some(f) = (*parent_class).alloc {
+                from_glib_full::<*mut ffi::GstMemory, Option<_>>(f(
+                    self.instance()
+                        .unsafe_cast_ref::<Allocator>()
+                        .to_glib_none()
+                        .0,
+                    size,
+                    mut_override(params.to_glib_none().0),
+                ))
+                .ok_or_else(|| bool_error!("Allocation failed"))
+            } else {
+                Err(bool_error!("No allocation method on parent class"))
+            }
+        }
+    }
+
+    fn parent_free(&self, memory: Memory) {
+        unsafe {
+            let data = Self::type_data();
+            let parent_class = data.as_ref().parent_class() as *mut ffi::GstAllocatorClass;
+
+            if let Some(f) = (*parent_class).free {
+                f(
+                    self.instance()
+                        .unsafe_cast_ref::<Allocator>()
+                        .to_glib_none()
+                        .0,
+                    memory.into_glib_ptr(),
+                )
+            }
+        }
+    }
+}
+
+unsafe impl<T: AllocatorImpl> IsSubclassable<T> for Allocator {
+    fn class_init(klass: &mut glib::Class<Self>) {
+        Self::parent_class_init::<T>(klass);
+        let klass = klass.as_mut();
+        klass.alloc = Some(alloc::<T>);
+        klass.free = Some(free::<T>);
+    }
+}
+
+unsafe extern "C" fn alloc<T: AllocatorImpl>(
+    ptr: *mut ffi::GstAllocator,
+    size: usize,
+    params: *mut ffi::GstAllocationParams,
+) -> *mut ffi::GstMemory {
+    let instance = &*(ptr as *mut T::Instance);
+    let imp = instance.imp();
+    let instance = imp.obj();
+
+    let params = if params.is_null() {
+        None
+    } else {
+        Some(&*(params as *mut AllocationParams))
+    };
+
+    imp.alloc(size, params)
+        .map(|memory| memory.into_glib_ptr())
+        .unwrap_or_else(|error| {
+            error!(crate::CAT_RUST, obj: instance, "{:?}", error);
+
+            ptr::null_mut()
+        })
+}
+
+unsafe extern "C" fn free<T: AllocatorImpl>(
+    ptr: *mut ffi::GstAllocator,
+    memory: *mut ffi::GstMemory,
+) {
+    let instance = &*(ptr as *mut T::Instance);
+    let imp = instance.imp();
+    let memory = from_glib_full(memory);
+
+    imp.free(memory);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::prelude::*;
+
+    pub mod imp {
+        use super::*;
+
+        #[derive(Default)]
+        pub struct TestAllocator;
+
+        impl ObjectImpl for TestAllocator {}
+        impl GstObjectImpl for TestAllocator {}
+        impl AllocatorImpl for TestAllocator {
+            fn alloc(
+                &self,
+                size: usize,
+                _params: Option<&AllocationParams>,
+            ) -> Result<Memory, BoolError> {
+                Ok(Memory::from_slice(vec![0; size]))
+            }
+
+            fn free(&self, memory: Memory) {
+                self.parent_free(memory)
+            }
+        }
+
+        #[glib::object_subclass]
+        impl ObjectSubclass for TestAllocator {
+            const NAME: &'static str = "TestAllocator";
+            type Type = super::TestAllocator;
+            type ParentType = Allocator;
+        }
+    }
+
+    glib::wrapper! {
+        pub struct TestAllocator(ObjectSubclass<imp::TestAllocator>) @extends Allocator, crate::Object;
+    }
+
+    impl Default for TestAllocator {
+        fn default() -> Self {
+            glib::Object::new(&[])
+        }
+    }
+
+    #[test]
+    fn test_allocator_registration() {
+        crate::init().unwrap();
+
+        const TEST_ALLOCATOR_NAME: &str = "TestAllocator";
+
+        let allocator = TestAllocator::default();
+        Allocator::register(TEST_ALLOCATOR_NAME, &allocator);
+
+        let allocator = Allocator::find(Some(TEST_ALLOCATOR_NAME));
+
+        assert!(allocator.is_some());
+    }
+
+    #[test]
+    fn test_allocator_alloc() {
+        crate::init().unwrap();
+
+        const SIZE: usize = 1024;
+
+        let allocator = TestAllocator::default();
+
+        let memory = allocator.alloc(SIZE, None).unwrap();
+
+        assert_eq!(memory.size(), SIZE);
+    }
+}

gstreamer/src/subclass/mod.rs

@@ -8,6 +8,7 @@ mod error;
 #[macro_use]
 mod plugin;
 
+mod allocator;
 mod bin;
 mod buffer_pool;
 mod child_proxy;
@@ -42,6 +43,7 @@ pub mod prelude {
     #[doc(hidden)]
     pub use glib::subclass::prelude::*;
 
+    pub use super::allocator::{AllocatorImpl, AllocatorImplExt};
     pub use super::bin::{BinImpl, BinImplExt};
     pub use super::buffer_pool::{BufferPoolImpl, BufferPoolImplExt};
     pub use super::child_proxy::{ChildProxyImpl, ChildProxyImplExt};