Struct MPSVectorDescriptor

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pub struct MPSVectorDescriptor { /* private fields */ }

Available on crate feature MPSMatrix only.

Expand description

Dependencies: This depends on Metal.framework

A MPSVectorDescriptor describes the length and data type of a an array of 1-dimensional vectors. All vectors are stored as contiguous arrays of data.

Implementations§

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impl MPSVectorDescriptor

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pub unsafe fn length(&self) -> NSUInteger

Available on crate feature MPSCore only.

The number of elements in the vector.

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pub unsafe fn setLength(&self, length: NSUInteger)

Available on crate feature MPSCore only.

Setter for length.

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pub unsafe fn vectors(&self) -> NSUInteger

Available on crate feature MPSCore only.

The number of vectors.

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pub unsafe fn dataType(&self) -> MPSDataType

Available on crate features MPSCore and MPSCoreTypes only.

The type of the data which makes up the values of the vector.

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pub unsafe fn setDataType(&self, data_type: MPSDataType)

Available on crate features MPSCore and MPSCoreTypes only.

Setter for dataType.

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pub unsafe fn vectorBytes(&self) -> NSUInteger

Available on crate feature MPSCore only.

The stride, in bytes, between corresponding elements of consecutive vectors. Must be a multiple of the element size

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pub unsafe fn vectorDescriptorWithLength_dataType( length: NSUInteger, data_type: MPSDataType, ) -> Retained<Self>

Available on crate features MPSCore and MPSCoreTypes only.

Create a MPSVectorDescriptor with the specified length and data type.

Parameter length: The number of elements in a single vector.

Parameter dataType: The type of the data to be stored in the vector.

Use this function for creating a descriptor of a MPSVector object containing a single vector.

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pub unsafe fn vectorDescriptorWithLength_vectors_vectorBytes_dataType( length: NSUInteger, vectors: NSUInteger, vector_bytes: NSUInteger, data_type: MPSDataType, ) -> Retained<Self>

Available on crate features MPSCore and MPSCoreTypes only.

Create a MPSVectorDescriptor with the specified length and data type.

Parameter length: The number of elements in a single vector.

Parameter vectors: The number of vectors in the MPSVector object.

Parameter vectorBytes: The number of bytes between starting elements of consecutive vectors.

Parameter dataType: The type of the data to be stored in the vector.

For performance considerations the optimal stride between vectors may not necessarily be equal to the vector length. The MPSVectorDescriptor class provides a method which may be used to determine this value, see the vectorBytesForLength API.

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pub unsafe fn vectorBytesForLength_dataType( length: NSUInteger, data_type: MPSDataType, ) -> usize

Available on crate features MPSCore and MPSCoreTypes only.

Return the recommended stride, in bytes, to be used for an array of vectors of a given length.

Parameter length: The number of elements in a single vector.

Parameter dataType: The type of vector data values.

To achieve best performance the optimal stride between vectors within an array of vectors is not necessarily equivalent to the number of elements per vector. This method returns the stride, in bytes, which gives best performance for a given vector length. Using this stride to construct your array is recommended, but not required (provided that the stride used is still large enough to allocate a full vector of data).

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impl MPSVectorDescriptor

Methods declared on superclass NSObject.

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pub unsafe fn init(this: Allocated<Self>) -> Retained<Self>

Available on crate feature MPSCore only.

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pub unsafe fn new() -> Retained<Self>

Available on crate feature MPSCore only.

Methods from Deref<Target = NSObject>§

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pub fn doesNotRecognizeSelector(&self, sel: Sel) -> !

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>§

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pub fn class(&self) -> &'static AnyClass

Dynamically find the class of this object.

§Panics

May panic if the object is invalid (which may be the case for objects returned from unavailable init/new methods).

§Example

Check that an instance of NSObject has the precise class NSObject.

use objc2::ClassType;
use objc2::runtime::NSObject;

let obj = NSObject::new();
assert_eq!(obj.class(), NSObject::class());

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pub unsafe fn get_ivar<T>(&self, name: &str) -> &T
where T: Encode,

👎Deprecated: this is difficult to use correctly, use Ivar::load instead.

Use Ivar::load instead.

§Safety

The object must have an instance variable with the given name, and it must be of type T.

See Ivar::load_ptr for details surrounding this.

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pub fn downcast_ref<T>(&self) -> Option<&T>
where T: DowncastTarget,

Attempt to downcast the object to a class of type T.

This is the reference-variant. Use Retained::downcast if you want to convert a retained object to another type.

§Mutable classes

Some classes have immutable and mutable variants, such as NSString and NSMutableString.

When some Objective-C API signature says it gives you an immutable class, it generally expects you to not mutate that, even though it may technically be mutable “under the hood”.

So using this method to convert a NSString to a NSMutableString, while not unsound, is generally frowned upon unless you created the string yourself, or the API explicitly documents the string to be mutable.

See Apple’s documentation on mutability and on isKindOfClass: for more details.

§Generic classes

Objective-C generics are called “lightweight generics”, and that’s because they aren’t exposed in the runtime. This makes it impossible to safely downcast to generic collections, so this is disallowed by this method.

You can, however, safely downcast to generic collections where all the type-parameters are AnyObject.

§Panics

This works internally by calling isKindOfClass:. That means that the object must have the instance method of that name, and an exception will be thrown (if CoreFoundation is linked) or the process will abort if that is not the case. In the vast majority of cases, you don’t need to worry about this, since both root objects NSObject and NSProxy implement this method.

§Examples

Cast an NSString back and forth from NSObject.

use objc2::rc::Retained;
use objc2_foundation::{NSObject, NSString};

let obj: Retained<NSObject> = NSString::new().into_super();
let string = obj.downcast_ref::<NSString>().unwrap();
// Or with `downcast`, if we do not need the object afterwards
let string = obj.downcast::<NSString>().unwrap();

Try (and fail) to cast an NSObject to an NSString.

use objc2_foundation::{NSObject, NSString};

let obj = NSObject::new();
assert!(obj.downcast_ref::<NSString>().is_none());

Try to cast to an array of strings.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);
// This is invalid and doesn't type check.
let arr = arr.downcast_ref::<NSArray<NSString>>();

This fails to compile, since it would require enumerating over the array to ensure that each element is of the desired type, which is a performance pitfall.

Downcast when processing each element instead.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);

for elem in arr {
    if let Some(data) = elem.downcast_ref::<NSString>() {
        // handle `data`
    }
}