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fuchsia.component

PROTOCOLS

Binder

Defined in fuchsia.component/binder.fidl

A framework-provided protocol that allows components that use it to bind to the component that exposes it. The act of connecting to this protocol will trigger the bind. Thus, this protocol contains no methods. For more details on binding, see https://fuchsia.dev/fuchsia-src/concepts/components/v2/lifecycle#binding.

When a component connects to protocol, the component exposing this capability will be started if it's not already running. Upon a failure to start, the component framework will close the server end of the channel with a zx.status epitaph.

Note: The component doesn't need to serve this protocol, it is implemented by the framework.

ChildIterator

Defined in fuchsia.component/realm.fidl

A protocol to iterate over the list of children in a realm.

Next

Advance the iterator and return the next batch of children.

Returns a vector of ChildRef. Returns an empty vector when there are no more children.

Request

<EMPTY>

Response

NameType
children vector<fuchsia.component.decl/ChildRef>[128]

Realm

Defined in fuchsia.component/realm.fidl

A protocol used by a component instance to manage its own realm, such as for binding to its children.

Requests to this protocol are processed in the order they are received. Clients that wish to send requests in parallel should open multiple connections.

The component framework provides this service to components that use fuchsia.component.Realm.

CreateChild

Creates a child component instance dynamically. When this function returns successfully, the instance exists, but it may not be running.

The environment of the child instance is determined by the environment of the collection. decl must not set environment.

Errors:

  • INVALID_ARGUMENTS: collection is not a valid reference or child is not a valid declaration.
  • COLLECTION_NOT_FOUND: collection does not exist.
  • INSTANCE_ALREADY_EXISTS: decl.name already exists in collection.
  • INSTANCE_CANNOT_RESOLVE: child's component declaration failed to resolve in a SingleRun collection.
  • NO_SPACE: Could not allocate storage for the new instance.
  • INSTANCE_DIED: This realm no longer exists.

Request

NameType
collection fuchsia.component.decl/CollectionRef
decl fuchsia.component.decl/Child
args CreateChildArgs

Response

NameType
result Realm_CreateChild_Result

DestroyChild

Destroys a dynamically-created component instance. When this function returns, the instance is destroyed and has stopped running. However, cleanup of the component's resources (such as its isolated storage) may happen in the background after this function returns.

Errors:

  • INVALID_ARGUMENTS: child is not a valid reference or does not refer to a dynamic instance.
  • INSTANCE_NOT_FOUND: child does not exist.
  • COLLECTION_NOT_FOUND: collection does not exist.
  • INSTANCE_DIED: This realm no longer exists.

Request

NameType
child fuchsia.component.decl/ChildRef

Response

NameType
result Realm_DestroyChild_Result

ListChildren

Returns an iterator that lists all instances in a collection.

NOTE: The results are not guaranteed to be consistent. Instances may be created or destroyed while the iterator is live, but those changes won't be observed by the iterator after this method returns.

Errors:

  • INVALID_ARGUMENTS: collection is not a valid reference or iter does not have ZX_RIGHT_WAIT.
  • COLLECTION_NOT_FOUND: collection does not exist.
  • INSTANCE_DIED: This realm no longer exists.
  • If iter does not have standard channel rights, this function may return ACCESS_DENIED or component manager may close iter.

Request

NameType
collection fuchsia.component.decl/CollectionRef
iter request<ChildIterator>

Response

NameType
result Realm_ListChildren_Result

OpenExposedDir

Opens the exposed directory of a child component instance. When this function successfully returns, exposed_dir is bound to a directory that contains the capabilities which the child exposed to its realm via ComponentDecl.exposes (specified via "expose" declarations in the component's manifest). The child component will not start as a result of this call. Instead, starting will occur iff the parent binds to one of the capabilities contained within exposed_dir.

exposed_dir is open as long as child exists.

Errors:

  • INVALID_ARGUMENTS: child is not a valid child reference.
  • INSTANCE_NOT_FOUND: child does not exist.
  • INSTANCE_CANNOT_RESOLVE: child's component declaration failed to resolve.
  • INSTANCE_DIED: This realm no longer exists.

Request

NameType
child fuchsia.component.decl/ChildRef
exposed_dir request<fuchsia.io/Directory>

Response

NameType
result Realm_OpenExposedDir_Result

STRUCTS

Realm_CreateChild_Response

Defined in fuchsia.component/realm.fidl

<EMPTY>

Realm_DestroyChild_Response

Defined in fuchsia.component/realm.fidl

<EMPTY>

Realm_ListChildren_Response

Defined in fuchsia.component/realm.fidl

<EMPTY>

Realm_OpenExposedDir_Response

Defined in fuchsia.component/realm.fidl

<EMPTY>

ENUMS

Error strict

Type: uint32

Defined in fuchsia.component/error.fidl

Standard error codes for component framework protocols.

NameValueDescription
INTERNAL 1

Component manager encountered an otherwise unspecified error while performing the operation.
INVALID_ARGUMENTS 2

At least one argument had an invalid format.
UNSUPPORTED 3

The feature is not yet supported.
ACCESS_DENIED 4

The caller did not have permission to perform the specified operation, or one of the handles provided to the call had insufficient rights.
INSTANCE_NOT_FOUND 5

The component instance was not found.
INSTANCE_ALREADY_EXISTS 6

The component instance already exists.
INSTANCE_CANNOT_START 7

The component instance could not be started.
INSTANCE_CANNOT_RESOLVE 8

Failed to resolve the component's declaration.
COLLECTION_NOT_FOUND 9

The component collection was not found.
RESOURCE_UNAVAILABLE 10

There were insufficient resources to perform the operation.
INSTANCE_DIED 11

The component instance died unexpectedly.
RESOURCE_NOT_FOUND 12

The requested resource does not exist.

TABLES

CreateChildArgs resource

Defined in fuchsia.component/realm.fidl

OrdinalFieldTypeDescription
1 numbered_handles vector<fuchsia.process/HandleInfo>[128]

The numbered handles to pass to the component instance.

Only PA_FD and PA_USER* handles are valid arguments, and inclusion of any other handles will result in an error. This argument is only supported for components in a collection with SingleRun durability.

If the runner for the component does not support the numbered handles it is expected to close the handles.
2 dynamic_offers vector<fuchsia.component.decl/Offer>[128]

Dynamic offers that will target the component instance.

Including OfferDecls in this vector will cause additional capabilities to be offered to the newly created child, beyond the OfferDecls in the parent's ComponentDecl that target the collection.

Any kind of offer (e.g., protocol, directory) can be used as a dynamic offer. Any source that would be valid for a static offer is also valid for a dynamic offer. Additionally, unlike static offers, dynamic offers can use a "sibling" dynamic child component as a source by setting the source to a ChildRef that sets the collection field.

Dynamic offers always target the newly created child component. As a result, OfferDecls in dynamic_offers must not set the target field, as its value is implied.

If either the source (that is, the component named in the source field of the OfferDecl) or the target of a dynamic offer is destroyed, the offer itself is destroyed simultaneously.

In order to set this field to a non-empty value, the collection in which the child component is being created must specify ComponentDecl.allowed_offers = STATIC_AND_DYNAMIC.

TODO(fxbug.dev/81109): Implementation is in progress.

UNIONS

Realm_CreateChild_Result strict

Defined in fuchsia.component/realm.fidl

Ordinal
VariantTypeDescription
1 response Realm_CreateChild_Response
2 err Error

Realm_DestroyChild_Result strict

Defined in fuchsia.component/realm.fidl

Ordinal
VariantTypeDescription
1 response Realm_DestroyChild_Response
2 err Error

Realm_ListChildren_Result strict

Defined in fuchsia.component/realm.fidl

Ordinal
VariantTypeDescription
1 response Realm_ListChildren_Response
2 err Error

Realm_OpenExposedDir_Result strict

Defined in fuchsia.component/realm.fidl

Ordinal
VariantTypeDescription
1 response Realm_OpenExposedDir_Response
2 err Error

CONSTANTS

NameValueTypeDescription
MAX_CHILD_COUNT 128 uint32

The maximum number of children that the a call ChildIterator.Next can return. Note, this is not a limit on the number of children that can be added to a component. This is merely a limit for a single invocation of the Next method.
MAX_DYNAMIC_OFFER_COUNT 128 uint32

The maximum number of dynamic offers that can target a created component.
MAX_HANDLE_COUNT 128 uint32

The maximum number of handles that can be passed to a created component.
MAX_MONIKER_LENGTH 4096 uint32
MAX_NAME_LENGTH 100 uint32
MAX_NUM_EVENTS_RECEIVED 100 uint64

The maximum number of events that a receiver can listen to.
MAX_PATH_LENGTH 1024 uint32
MAX_SUBSCRIPTION_REQUESTS 2 uint32

The maximum number of requests per event subscription.
MAX_URL_SCHEME_LENGTH 100 uint32

TYPE ALIASES

NameValueDescription
name string[MAX_NAME_LENGTH]
url_scheme string[MAX_URL_SCHEME_LENGTH]