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  3. FCbPackage

FCbPackage

A package is an object with a tree of referenced attachments.

API > API/Runtime > API/Runtime/Core > API/Runtime/Core/Serialization

References

   
Module Core
Header /Engine/Source/Runtime/Core/Public/Serialization/CompactBinaryPackage.h
Include #include "Serialization/CompactBinaryPackage.h"

Syntax

class FCbPackage

Remarks

A package is an object with a tree of referenced attachments.

A package is a Merkle tree with an object as its root and non-leaf nodes, and either binary or objects as its leaf nodes. Nodes reference their children from fields of type BinaryAttachment or ObjectAttachment, which store the raw hash of the referenced attachment.

It is invalid for a package to include attachments that are not referenced by its object or by one of its referenced object attachments. This invariant needs to be maintained if attachments are added explicitly instead of being discovered by the attachment resolver. If any attachment is not referenced, it may not survive a round-trip through certain storage systems.

It is valid for a package to exclude referenced attachments, but then it is the responsibility of the package consumer to have a mechanism for resolving those references when necessary.

A package is serialized as a sequence of compact binary fields with no name. The object may be both preceded and followed by attachments. The object is only serialized when it is non-empty, starting with its hash, in a Hash field, followed by the object, in an Object field. A package ends with a Null field. The canonical order of components is the object and its hash, followed by the attachments ordered by hash, followed by a Null field. It is valid for the a package to have its attachments serialized in any order relative to each other and to the object.

Constructors

  Type Name Description
Public function   Construct a null package.
Public function  

FCbPackage ( FCbObject InObject
)

 Construct a package from a root object without gathering attachments.
Public function  

FCbPackage ( FCbObject InObject,
FAttachmentResolver InResolver
)

 Construct a package from a root object and gather attachments using the resolver.
Public function  

FCbPackage ( FCbObject InObject,
const FIoHash& InObjectHash
)

 Construct a package from a root object without gathering attachments.
Public function  

FCbPackage ( FCbObject InObject,
const FIoHash& InObjectHash,
FAttachmentResolver InResolver
)

 Construct a package from a root object and gather attachments using the resolver.

Functions

  Type Name Description
Public function void

AddAttachment ( const FCbAttachment& Attachment,
FAttachmentResolver Resolver
)

 Add the attachment to this package, along with any references that can be resolved.
Public function void

AddAttachment ( const FCbAttachment& Attachment
)

 Add the attachment to this package.
Public function Const bool

Equals ( const FCbPackage& Package
)

 Compares packages by their object and attachment hashes.
Public function Const const FCbAttachment *

FindAttachment ( const FCbAttachment& Attachment
)

 Find an attachment if it exists in the package.
Public function Const const FCbAttachment *

FindAttachment ( const FIoHash& Hash
)

 Find an attachment by its hash.
Public function Const TConstArrayView< FCbAttachment > Returns the attachments in this package.
Public function Const const FCbObject & Returns the object for the package.
Public function Const const FIoHash & Returns the hash of the object for the package.
Public function Const bool

IsNull ()

 Whether the package has an empty object and no attachments.
Public function int32

RemoveAttachment ( const FCbAttachment& Attachment
)

  
Public function int32

RemoveAttachment ( const FIoHash& Hash
)

 Remove an attachment by hash.
Public function void

Reset ()

 Reset this to a null package.
Public function Const void

Save ( FCbWriter& Writer
)

 Save the object and attachments into the writer as a stream of compact binary fields.
Public function Const void

Save ( FArchive& Ar
)

 Save the object and attachments into the archive as a stream of compact binary fields.
Public function void

SetObject ( FCbObject InObject
)

 Set the root object without gathering attachments.
Public function void

SetObject ( FCbObject InObject,
FAttachmentResolver InResolver
)

 Set the root object and gather attachments using the resolver.
Public function void

SetObject ( FCbObject InObject,
const FIoHash& InObjectHash
)

 Set the root object without gathering attachments.
Public function void

SetObject ( FCbObject InObject,
const FIoHash& InObjectHash,
FAttachmentResolver InResolver
)

 Set the root object and gather attachments using the resolver.
Public function bool Load the object and attachments from compact binary as written by Save.
Public function bool

TryLoad ( FArchive& Ar,
FCbBufferAllocator Allocator
)

 Load the object and attachments from compact binary as written by Save.

Operators

  Type Name Description
Public function Const   Whether the package has a non-empty object or attachments.
Public function Const bool

operator!= ( const FCbPackage& Package
)

  
Public function Const bool

operator== ( const FCbPackage& Package
)

  

Typedefs

Name Description
FAttachmentResolver A function that resolves a hash to a buffer containing the data matching that hash.

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