Struct AVAssetResourceLoadingDataRequest

Source

#[repr(C)]
pub struct AVAssetResourceLoadingDataRequest { /* private fields */ }

Available on crate feature AVAssetResourceLoader only.

Expand description

Apple’s documentation

Implementations§

Source §

pub unsafe fn requestedOffset(&self) -> c_longlong

The position within the resource of the first byte requested.

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pub unsafe fn requestedLength(&self) -> NSInteger

The length of the data requested.

Note that requestsAllDataToEndOfResource will be set to YES when the entire remaining length of the resource is being requested from requestedOffset to the end of the resource. This can occur even when the content length has not yet been reported by you via a prior finished loading request. When requestsAllDataToEndOfResource has a value of YES, you should disregard the value of requestedLength and incrementally provide as much data starting from the requestedOffset as the resource contains, until you have provided all of the available data successfully and invoked -finishLoading, until you have encountered a failure and invoked -finishLoadingWithError:, or until you have received -resourceLoader:didCancelLoadingRequest: for the AVAssetResourceLoadingRequest from which the AVAssetResourceLoadingDataRequest was obtained. When requestsAllDataToEndOfResource is YES and the content length has not yet been provided by you via a prior finished loading request, the value of requestedLength is set to NSIntegerMax. Starting in macOS 10.11 and iOS 9.0, in 32-bit applications requestedLength is also set to NSIntegerMax when all of the remaining resource data is being requested and the known length of the remaining data exceeds NSIntegerMax.

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pub unsafe fn requestsAllDataToEndOfResource(&self) -> bool

Specifies that the entire remaining length of the resource from requestedOffset to the end of the resource is being requested.

When requestsAllDataToEndOfResource has a value of YES, you should disregard the value of requestedLength and incrementally provide as much data starting from the requestedOffset as the resource contains, until you have provided all of the available data successfully and invoked -finishLoading, until you have encountered a failure and invoked -finishLoadingWithError:, or until you have received -resourceLoader:didCancelLoadingRequest: for the AVAssetResourceLoadingRequest from which the AVAssetResourceLoadingDataRequest was obtained.

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pub unsafe fn currentOffset(&self) -> c_longlong

The position within the resource of the next byte within the resource following the bytes that have already been provided via prior invocations of -respondWithData.

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pub unsafe fn respondWithData(&self, data: &NSData)

Provides data to the receiver.

Parameter data: An instance of NSData containing some or all of the requested bytes.

May be invoked multiple times on the same instance of AVAssetResourceLoadingDataRequest to provide the full range of requested data incrementally. Upon each invocation, the value of currentOffset will be updated to accord with the amount of data provided. The instance of NSData that you provide may be retained for use in parsing or other processing for an indefinite period of time after this method returns. For this reason, if you are providing an instance of NSMutableData, you should avoid mutating it further after sharing its contents. If you are managing your own memory pool for I/O and resource loading, consider using -[NSData initWithBytesNoCopy:length:deallocator:] in order to receive notification of the earliest opportunity for safe recycling of the underlying memory.

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`
    }
}