ruffle/core/src/avm2/traits.rs

//! Active trait definitions

use crate::avm2::class::Class;
use crate::avm2::method::Method;
use crate::avm2::names::{Multiname, QName};
use crate::avm2::script::TranslationUnit;
use crate::avm2::value::{abc_default_value, Value};
use crate::avm2::Error;
use crate::context::UpdateContext;
use bitflags::bitflags;
use gc_arena::{Collect, GcCell};
use swf::avm2::types::{Trait as AbcTrait, TraitKind as AbcTraitKind};

bitflags! {
    /// All attributes a trait can have.
    pub struct  TraitAttributes: u8 {
        /// Whether or not traits in downstream classes are allowed to override
        /// this trait.
        const FINAL    = 1 << 0;

        /// Whether or not this trait is intended to override an upstream class's
        /// trait.
        const OVERRIDE = 1 << 1;
    }
}

/// Represents a trait as loaded into the VM.
///
/// A trait is an uninstantiated AVM2 property. Traits are used by objects to
/// track how to construct their properties when first accessed.
///
/// This type exists primarily to support classes with native methods. Adobe's
/// implementation of AVM2 handles native classes by having a special ABC file
/// load before all other code. We instead generate an initial heap in the same
/// manner as we do in AVM1, which means that we need to have a way to
/// dynamically originate traits that do not come from any particular ABC file.
#[derive(Clone, Debug, Collect)]
#[collect(no_drop)]
pub struct Trait<'gc> {
    /// The name of this trait.
    name: QName<'gc>,

    /// The attributes set on this trait.
    #[collect(require_static)]
    attributes: TraitAttributes,

    /// The kind of trait in use.
    kind: TraitKind<'gc>,
}

fn trait_attribs_from_abc_traits(abc_trait: &AbcTrait) -> TraitAttributes {
    let mut attributes = TraitAttributes::empty();
    attributes.set(TraitAttributes::FINAL, abc_trait.is_final);
    attributes.set(TraitAttributes::OVERRIDE, abc_trait.is_override);
    attributes
}

/// The fields for a particular kind of trait.
///
/// The kind of a trait also determines how it's instantiated on the object.
/// See each individual variant for more information.
#[derive(Clone, Debug, Collect)]
#[collect(no_drop)]
pub enum TraitKind<'gc> {
    /// A data field on an object instance that can be read from and written
    /// to.
    Slot {
        slot_id: u32,
        type_name: Multiname<'gc>,
        default_value: Option<Value<'gc>>,
    },

    /// A method on an object that can be called.
    Method { disp_id: u32, method: Method<'gc> },

    /// A getter property on an object that can be read.
    Getter { disp_id: u32, method: Method<'gc> },

    /// A setter property on an object that can be written.
    Setter { disp_id: u32, method: Method<'gc> },

    /// A class property on an object that can be used to construct more
    /// objects.
    Class {
        slot_id: u32,
        class: GcCell<'gc, Class<'gc>>,
    },

    /// A free function (not an instance method) that can be called.
    Function { slot_id: u32, function: Method<'gc> },

    /// A data field on an object that is always a particular value, and cannot
    /// be overridden.
    Const {
        slot_id: u32,
        type_name: Multiname<'gc>,
        default_value: Option<Value<'gc>>,
    },
}

impl<'gc> Trait<'gc> {
    pub fn from_class(class: GcCell<'gc, Class<'gc>>) -> Self {
        let name = class.read().name().clone();

        Trait {
            name,
            attributes: TraitAttributes::empty(),
            kind: TraitKind::Class { slot_id: 0, class },
        }
    }

    pub fn from_method(name: QName<'gc>, method: Method<'gc>) -> Self {
        Trait {
            name,
            attributes: TraitAttributes::empty(),
            kind: TraitKind::Method { disp_id: 0, method },
        }
    }

    pub fn from_getter(name: QName<'gc>, method: Method<'gc>) -> Self {
        Trait {
            name,
            attributes: TraitAttributes::empty(),
            kind: TraitKind::Getter { disp_id: 0, method },
        }
    }

    pub fn from_setter(name: QName<'gc>, method: Method<'gc>) -> Self {
        Trait {
            name,
            attributes: TraitAttributes::empty(),
            kind: TraitKind::Setter { disp_id: 0, method },
        }
    }

    pub fn from_function(name: QName<'gc>, function: Method<'gc>) -> Self {
        Trait {
            name,
            attributes: TraitAttributes::empty(),
            kind: TraitKind::Function {
                slot_id: 0,
                function,
            },
        }
    }

    pub fn from_slot(
        name: QName<'gc>,
        type_name: Multiname<'gc>,
        default_value: Option<Value<'gc>>,
    ) -> Self {
        Trait {
            name,
            attributes: TraitAttributes::empty(),
            kind: TraitKind::Slot {
                slot_id: 0,
                type_name,
                default_value,
            },
        }
    }

    pub fn from_const(
        name: QName<'gc>,
        type_name: Multiname<'gc>,
        default_value: Option<Value<'gc>>,
    ) -> Self {
        Trait {
            name,
            attributes: TraitAttributes::empty(),
            kind: TraitKind::Slot {
                slot_id: 0,
                type_name,
                default_value,
            },
        }
    }

    /// Convert an ABC trait into a loaded trait.
    pub fn from_abc_trait(
        unit: TranslationUnit<'gc>,
        abc_trait: &AbcTrait,
        uc: &mut UpdateContext<'_, 'gc, '_>,
    ) -> Result<Self, Error> {
        let name = QName::from_abc_multiname(unit, abc_trait.name.clone(), uc.gc_context)?;

        Ok(match &abc_trait.kind {
            AbcTraitKind::Slot {
                slot_id,
                type_name,
                value,
            } => Trait {
                name,
                attributes: trait_attribs_from_abc_traits(abc_trait),
                kind: TraitKind::Slot {
                    slot_id: *slot_id,
                    type_name: if type_name.0 == 0 {
                        Multiname::any()
                    } else {
                        Multiname::from_abc_multiname_static(
                            unit,
                            type_name.clone(),
                            uc.gc_context,
                        )?
                    },
                    default_value: if let Some(dv) = value {
                        Some(abc_default_value(unit, dv, uc)?)
                    } else {
                        None
                    },
                },
            },
            AbcTraitKind::Method { disp_id, method } => Trait {
                name,
                attributes: trait_attribs_from_abc_traits(abc_trait),
                kind: TraitKind::Method {
                    disp_id: *disp_id,
                    method: unit.load_method(method.0, uc.gc_context)?,
                },
            },
            AbcTraitKind::Getter { disp_id, method } => Trait {
                name,
                attributes: trait_attribs_from_abc_traits(abc_trait),
                kind: TraitKind::Getter {
                    disp_id: *disp_id,
                    method: unit.load_method(method.0, uc.gc_context)?,
                },
            },
            AbcTraitKind::Setter { disp_id, method } => Trait {
                name,
                attributes: trait_attribs_from_abc_traits(abc_trait),
                kind: TraitKind::Setter {
                    disp_id: *disp_id,
                    method: unit.load_method(method.0, uc.gc_context)?,
                },
            },
            AbcTraitKind::Class { slot_id, class } => Trait {
                name,
                attributes: trait_attribs_from_abc_traits(abc_trait),
                kind: TraitKind::Class {
                    slot_id: *slot_id,
                    class: unit.load_class(class.0, uc)?,
                },
            },
            AbcTraitKind::Function { slot_id, function } => Trait {
                name,
                attributes: trait_attribs_from_abc_traits(abc_trait),
                kind: TraitKind::Function {
                    slot_id: *slot_id,
                    function: unit.load_method(function.0, uc.gc_context)?,
                },
            },
            AbcTraitKind::Const {
                slot_id,
                type_name,
                value,
            } => Trait {
                name,
                attributes: trait_attribs_from_abc_traits(abc_trait),
                kind: TraitKind::Const {
                    slot_id: *slot_id,
                    type_name: if type_name.0 == 0 {
                        Multiname::any()
                    } else {
                        Multiname::from_abc_multiname_static(
                            unit,
                            type_name.clone(),
                            uc.gc_context,
                        )?
                    },
                    default_value: if let Some(dv) = value {
                        Some(abc_default_value(unit, dv, uc)?)
                    } else {
                        None
                    },
                },
            },
        })
    }

    pub fn name(&self) -> &QName<'gc> {
        &self.name
    }

    pub fn kind(&self) -> &TraitKind<'gc> {
        &self.kind
    }

    pub fn is_final(&self) -> bool {
        self.attributes.contains(TraitAttributes::FINAL)
    }

    pub fn is_override(&self) -> bool {
        self.attributes.contains(TraitAttributes::OVERRIDE)
    }

    pub fn set_attributes(&mut self, attribs: TraitAttributes) {
        self.attributes = attribs;
    }

    /// Convenience chaining method that adds the override flag to a trait.
    pub fn with_override(mut self) -> Self {
        self.attributes |= TraitAttributes::OVERRIDE;

        self
    }

    /// Set the slot or dispatch ID of this trait.
    pub fn set_slot_id(&mut self, id: u32) {
        match &mut self.kind {
            TraitKind::Slot { slot_id, .. } => *slot_id = id,
            TraitKind::Method { disp_id, .. } => *disp_id = id,
            TraitKind::Getter { disp_id, .. } => *disp_id = id,
            TraitKind::Setter { disp_id, .. } => *disp_id = id,
            TraitKind::Class { slot_id, .. } => *slot_id = id,
            TraitKind::Function { slot_id, .. } => *slot_id = id,
            TraitKind::Const { slot_id, .. } => *slot_id = id,
        }
    }
}