Struct bevy::ptr::PtrMut

pub struct PtrMut<'a, A = Aligned>(/* private fields */)
where
    A: IsAligned;

Type-erased mutable borrow of some unknown type chosen when constructing this type.

This type tries to act “borrow-like” which means that:

• Pointer is considered exclusive and mutable. It cannot be cloned as this would lead to aliased mutability.
• It must always points to a valid value of whatever the pointee type is.
• The lifetime 'a accurately represents how long the pointer is valid for.
• Must be sufficiently aligned for the unknown pointee type.

It may be helpful to think of this type as similar to &'a mut dyn Any but without the metadata and able to point to data that does not correspond to a Rust type.

Implementations

impl<'a> PtrMut<'a>

pub fn to_unaligned(self) -> PtrMut<'a, Unaligned>

Removes the alignment requirement of this pointer

impl<A> PtrMut<'_, A>

where A: IsAligned,

pub unsafe fn byte_offset(self, count: isize) -> PtrMut<'_, A>

Calculates the offset from a pointer. As the pointer is type-erased, there is no size information available. The provided count parameter is in raw bytes.

See also: ptr::offset

Safety

• The offset cannot make the existing ptr null, or take it out of bounds for its allocation.
• If the A type parameter is Aligned then the offset must not make the resulting pointer be unaligned for the pointee type.

pub unsafe fn byte_add(self, count: usize) -> PtrMut<'_, A>

Calculates the offset from a pointer (convenience for .offset(count as isize)). As the pointer is type-erased, there is no size information available. The provided count parameter is in raw bytes.

See also: ptr::add

Safety

• The offset cannot make the existing ptr null, or take it out of bounds for its allocation.
• If the A type parameter is Aligned then the offset must not make the resulting pointer be unaligned for the pointee type.

impl<'a, A> PtrMut<'a, A>

where A: IsAligned,

pub unsafe fn new(inner: NonNull<u8>) -> PtrMut<'a, A>

Creates a new instance from a raw pointer.

Safety

• inner must point to valid value of whatever the pointee type is.
• If the A type parameter is Aligned then inner must be sufficiently aligned for the pointee type.
• inner must have correct provenance to allow read and writes of the pointee type.
• The lifetime 'a must be constrained such that this PtrMut will stay valid and nothing else can read or mutate the pointee while this PtrMut is live.

pub unsafe fn promote(self) -> OwningPtr<'a, A>

Transforms this PtrMut into an OwningPtr

Safety

Must have right to drop or move out of PtrMut.

pub unsafe fn deref_mut<T>(self) -> &'a mut T

Transforms this PtrMut<T> into a &mut T with the same lifetime

Safety

• T must be the erased pointee type for this PtrMut.
• If the type parameter A is Unaligned then this pointer must be sufficiently aligned for the pointee type T.

pub fn as_ptr(&self) -> *mut u8

Gets the underlying pointer, erasing the associated lifetime.

If possible, it is strongly encouraged to use deref_mut over this function, as it retains the lifetime.

Examples found in repository

examples/ecs/dynamic.rs (line 163)

fn main() {
    let mut world = World::new();
    let mut lines = std::io::stdin().lines();
    let mut component_names = HashMap::<String, ComponentId>::new();
    let mut component_info = HashMap::<ComponentId, ComponentInfo>::new();

    println!("{}", PROMPT);
    loop {
        print!("\n> ");
        let _ = std::io::stdout().flush();
        let Some(Ok(line)) = lines.next() else {
            return;
        };

        if line.is_empty() {
            return;
        };

        let Some((first, rest)) = line.trim().split_once(|c: char| c.is_whitespace()) else {
            match &line.chars().next() {
                Some('c') => println!("{}", COMPONENT_PROMPT),
                Some('s') => println!("{}", ENTITY_PROMPT),
                Some('q') => println!("{}", QUERY_PROMPT),
                _ => println!("{}", PROMPT),
            }
            continue;
        };

        match &first[0..1] {
            "c" => {
                rest.split(',').for_each(|component| {
                    let mut component = component.split_whitespace();
                    let Some(name) = component.next() else {
                        return;
                    };
                    let size = match component.next().map(|s| s.parse::<usize>()) {
                        Some(Ok(size)) => size,
                        _ => 0,
                    };
                    // Register our new component to the world with a layout specified by it's size
                    // SAFETY: [u64] is Send + Sync
                    let id = world.init_component_with_descriptor(unsafe {
                        ComponentDescriptor::new_with_layout(
                            name.to_string(),
                            StorageType::Table,
                            Layout::array::<u64>(size).unwrap(),
                            None,
                        )
                    });
                    let Some(info) = world.components().get_info(id) else {
                        return;
                    };
                    component_names.insert(name.to_string(), id);
                    component_info.insert(id, info.clone());
                    println!("Component {} created with id: {:?}", name, id.index());
                });
            }
            "s" => {
                let mut to_insert_ids = Vec::new();
                let mut to_insert_data = Vec::new();
                rest.split(',').for_each(|component| {
                    let mut component = component.split_whitespace();
                    let Some(name) = component.next() else {
                        return;
                    };

                    // Get the id for the component with the given name
                    let Some(&id) = component_names.get(name) else {
                        println!("Component {} does not exist", name);
                        return;
                    };

                    // Calculate the length for the array based on the layout created for this component id
                    let info = world.components().get_info(id).unwrap();
                    let len = info.layout().size() / std::mem::size_of::<u64>();
                    let mut values: Vec<u64> = component
                        .take(len)
                        .filter_map(|value| value.parse::<u64>().ok())
                        .collect();
                    values.resize(len, 0);

                    // Collect the id and array to be inserted onto our entity
                    to_insert_ids.push(id);
                    to_insert_data.push(values);
                });

                let mut entity = world.spawn_empty();

                // Construct an `OwningPtr` for each component in `to_insert_data`
                let to_insert_ptr = to_owning_ptrs(&mut to_insert_data);

                // SAFETY:
                // - Component ids have been taken from the same world
                // - Each array is created to the layout specified in the world
                unsafe {
                    entity.insert_by_ids(&to_insert_ids, to_insert_ptr.into_iter());
                }

                println!("Entity spawned with id: {:?}", entity.id());
            }
            "q" => {
                let mut builder = QueryBuilder::<FilteredEntityMut>::new(&mut world);
                parse_query(rest, &mut builder, &component_names);
                let mut query = builder.build();

                query.iter_mut(&mut world).for_each(|filtered_entity| {
                    let terms = filtered_entity
                        .components()
                        .map(|id| {
                            let ptr = filtered_entity.get_by_id(id).unwrap();
                            let info = component_info.get(&id).unwrap();
                            let len = info.layout().size() / std::mem::size_of::<u64>();

                            // SAFETY:
                            // - All components are created with layout [u64]
                            // - len is calculated from the component descriptor
                            let data = unsafe {
                                std::slice::from_raw_parts_mut(
                                    ptr.assert_unique().as_ptr().cast::<u64>(),
                                    len,
                                )
                            };

                            // If we have write access, increment each value once
                            if filtered_entity.access().has_write(id) {
                                data.iter_mut().for_each(|data| {
                                    *data += 1;
                                });
                            }

                            format!("{}: {:?}", info.name(), data[0..len].to_vec())
                        })
                        .collect::<Vec<_>>()
                        .join(", ");

                    println!("{:?}: {}", filtered_entity.id(), terms);
                });
            }
            _ => continue,
        }
    }
}

pub fn reborrow(&mut self) -> PtrMut<'_, A>

Gets a PtrMut from this with a smaller lifetime.

pub fn as_ref(&self) -> Ptr<'_, A>

Gets an immutable reference from this mutable reference

Trait Implementations

impl<'a, T> From<&'a mut T> for PtrMut<'a>

fn from(val: &'a mut T) -> PtrMut<'a>

Converts to this type from the input type.

impl<'a, A> From<PtrMut<'a, A>> for NonNull<u8>

where A: IsAligned,

fn from(ptr: PtrMut<'a, A>) -> NonNull<u8>

Converts to this type from the input type.

impl<A> Pointer for PtrMut<'_, A>

where A: IsAligned,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.