# node_slot.rs - source
Source of the Rust file `maplibre/src/render/graph/node_slot.rs`.
Keywords: rust, rustlang, rust-lang

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    use crate::render::resource::TextureView;
    use std::rc::Rc;
    use std::{borrow::Cow, fmt};

    /// A value passed between render [`Nodes`](super::Node).
    /// Corresponds to the [`SlotType`] specified in the [`RenderGraph`](super::RenderGraph).
    ///
    /// Slots can have four different types of values:
    /// [`Buffer`], [`TextureView`], [`Sampler`] and [`Entity`].
    ///
    /// These values do not contain the actual render data, but only the ids to retrieve them.
    #[derive(Clone, Debug)]
    pub enum SlotValue {
        /// A GPU-accessible [`Buffer`].
        Buffer(Rc<wgpu::Buffer>),
        /// A [`TextureView`] describes a texture used in a pipeline.
        TextureView(Rc<TextureView>),
        /// A texture [`Sampler`] defines how a pipeline will sample from a [`TextureView`].
        Sampler(Rc<wgpu::Sampler>),
    }

    impl SlotValue {
        /// Returns the [`SlotType`] of this value.
        pub fn slot_type(&self) -> SlotType {
            match self {
                SlotValue::Buffer(_) => SlotType::Buffer,
                SlotValue::TextureView(_) => SlotType::TextureView,
                SlotValue::Sampler(_) => SlotType::Sampler,
            }
        }
    }

    impl From<wgpu::Buffer> for SlotValue {
        fn from(value: wgpu::Buffer) -> Self {
            SlotValue::Buffer(Rc::new(value))
        }
    }

    impl From<TextureView> for SlotValue {
        fn from(value: TextureView) -> Self {
            SlotValue::TextureView(Rc::new(value))
        }
    }

    impl From<wgpu::Sampler> for SlotValue {
        fn from(value: wgpu::Sampler) -> Self {
            SlotValue::Sampler(Rc::new(value))
        }
    }

    /// Describes the render resources created (output) or used (input) by
    /// the render [`Nodes`](super::Node).
    ///
    /// This should not be confused with [`SlotValue`], which actually contains the passed data.
    #[derive(Debug, Copy, Clone, Eq, PartialEq)]
    pub enum SlotType {
        /// A GPU-accessible [`Buffer`].
        Buffer,
        /// A [`TextureView`] describes a texture used in a pipeline.
        TextureView,
        /// A texture [`Sampler`] defines how a pipeline will sample from a [`TextureView`].
        Sampler,
    }

    impl fmt::Display for SlotType {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            let s = match self {
                SlotType::Buffer => "Buffer",
                SlotType::TextureView => "TextureView",
                SlotType::Sampler => "Sampler",
            };

            f.write_str(s)
        }
    }

    /// A [`SlotLabel`] is used to reference a slot by either its name or index
    /// inside the [`RenderGraph`](super::RenderGraph).
    #[derive(Debug, Clone, Eq, PartialEq)]
    pub enum SlotLabel {
        Index(usize),
        Name(Cow<'static, str>),
    }

    impl From<&SlotLabel> for SlotLabel {
        fn from(value: &SlotLabel) -> Self {
            value.clone()
        }
    }

    impl From<String> for SlotLabel {
        fn from(value: String) -> Self {
            SlotLabel::Name(value.into())
        }
    }

    impl From<&'static str> for SlotLabel {
        fn from(value: &'static str) -> Self {
            SlotLabel::Name(value.into())
        }
    }

    impl From<Cow<'static, str>> for SlotLabel {
        fn from(value: Cow<'static, str>) -> Self {
            SlotLabel::Name(value.clone())
        }
    }

    impl From<usize> for SlotLabel {
        fn from(value: usize) -> Self {
            SlotLabel::Index(value)
        }
    }

    /// The internal representation of a slot, which specifies its [`SlotType`] and name.
    #[derive(Clone, Debug)]
    pub struct SlotInfo {
        pub name: Cow<'static, str>,
        pub slot_type: SlotType,
    }

    impl SlotInfo {
        pub fn new(name: impl Into<Cow<'static, str>>, slot_type: SlotType) -> Self {
            SlotInfo {
                name: name.into(),
                slot_type,
            }
        }
    }

    /// A collection of input or output [`SlotInfos`](SlotInfo) for
    /// a [`NodeState`](super::NodeState).
    #[derive(Default, Debug)]
    pub struct SlotInfos {
        slots: Vec<SlotInfo>,
    }

    impl<T: IntoIterator<Item = SlotInfo>> From<T> for SlotInfos {
        fn from(slots: T) -> Self {
            SlotInfos {
                slots: slots.into_iter().collect(),
            }
        }
    }

    impl SlotInfos {
        /// Returns the count of slots.
        #[inline]
        pub fn len(&self) -> usize {
            self.slots.len()
        }

        /// Returns true if there are no slots.
        #[inline]
        pub fn is_empty(&self) -> bool {
            self.slots.is_empty()
        }

        /// Retrieves the [`SlotInfo`] for the provided label.
        pub fn get_slot(&self, label: impl Into<SlotLabel>) -> Option<&SlotInfo> {
            let label = label.into();
            let index = self.get_slot_index(&label)?;
            self.slots.get(index)
        }

        /// Retrieves the [`SlotInfo`] for the provided label mutably.
        pub fn get_slot_mut(&mut self, label: impl Into<SlotLabel>) -> Option<&mut SlotInfo> {
            let label = label.into();
            let index = self.get_slot_index(&label)?;
            self.slots.get_mut(index)
        }

        /// Retrieves the index (inside input or output slots) of the slot for the provided label.
        pub fn get_slot_index(&self, label: impl Into<SlotLabel>) -> Option<usize> {
            let label = label.into();
            match label {
                SlotLabel::Index(index) => Some(index),
                SlotLabel::Name(ref name) => self
                    .slots
                    .iter()
                    .enumerate()
                    .find(|(_i, s)| s.name == *name)
                    .map(|(i, _s)| i),
            }
        }

        /// Returns an iterator over the slot infos.
        pub fn iter(&self) -> impl Iterator<Item = &SlotInfo> {
            self.slots.iter()
        }
    }