FCbFieldView

An atom of data in the compact binary format.

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Inheritance Hierarchy

FCbFieldView

	FCbArrayView
	FCbObjectView

References

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

Syntax

class FCbFieldView

Remarks

An atom of data in the compact binary format.

Accessing the value of a field is always a safe operation, even if accessed as the wrong type. An invalid access will return a default value for the requested type, and set an error code on the field that can be checked with GetLastError and HasLastError. A valid access will clear an error from a previous invalid access.

A field is encoded in one or more bytes, depending on its type and the type of object or array that contains it. A field of an object or array which is non-uniform encodes its field type in the first byte, and includes the HasFieldName flag for a field in an object. The field name is encoded in a variable-length unsigned integer of its size in bytes, for named fields, followed by that many bytes of the UTF-8 encoding of the name with no null terminator. The remainder of the field is the value which is described in the field type enum. Every field must be uniquely addressable when encoded, which means a zero-byte field is not permitted, and only arises in a uniform array of fields with no value, where the answer is to encode as a non-uniform array.

This type only provides a view into memory and does not perform any memory management itself. Use FCbField to hold a reference to the underlying memory when necessary.

Constructors

	Name	Description
	FCbFieldView()	Construct a field with no name and no value.
	FCbFieldView ( const FCbValue& Value )	Construct a field from a value, without access to the name.
	FCbFieldView ( const void* Data, ECbFieldType Type )	Construct a field from a pointer to its data and an optional externally-provided type.

Functions

	Name	Description
void	AppendHash ( FIoHashBuilder& Builder )	Append the hash of the field, including the type and name.
FCbArrayView	AsArrayView()	Access the field as an array. Defaults to an empty array on error.
FIoHash	AsAttachment ( const FIoHash& Default )	Access the field as a hash referencing an attachment. Returns the provided default on error.
FIoHash	AsBinaryAttachment ( const FIoHash& Default )	Access the field as a hash referencing a binary attachment. Returns the provided default on error.
FMemoryView	AsBinaryView ( FMemoryView Default )	Access the field as binary. Returns the provided default on error.
bool	AsBool ( bool bDefault )	Access the field as a bool. Returns the provided default on error.
FMemoryView	AsCustom ( FUtf8StringView Name, FMemoryView Default )	Access the field as a custom sub-type with a string identifier.
FMemoryView	AsCustom ( uint64 Id, FMemoryView Default )	Access the field as a custom sub-type with an integer identifier.
FCbCustomByI...	AsCustomById ( FCbCustomById Default )	Access the field as a custom sub-type with an integer identifier.
FCbCustomByN...	AsCustomByName ( FCbCustomByName Default )	Access the field as a custom sub-type with a string identifier.
FDateTime	AsDateTime()	Access the field as a date/time. Returns a date/time at the epoch on error.
FDateTime	AsDateTime ( FDateTime Default )	Access the field as a date/time. Returns the provided default on error.
int64	AsDateTimeTicks ( int64 Default )	Access the field as a date/time tick count. Returns the provided default on error.
double	AsDouble ( double Default )	Access the field as a double. Returns the provided default on error.
float	AsFloat ( float Default )	Access the field as a float. Returns the provided default on error.
FIoHash	AsHash ( const FIoHash& Default )	Access the field as a hash. Returns the provided default on error.
int16	AsInt16 ( int16 Default )	Access the field as an int16. Returns the provided default on error.
int32	AsInt32 ( int32 Default )	Access the field as an int32. Returns the provided default on error.
int64	AsInt64 ( int64 Default )	Access the field as an int64. Returns the provided default on error.
int8	AsInt8 ( int8 Default )	Access the field as an int8. Returns the provided default on error.
FIoHash	AsObjectAttachment ( const FIoHash& Default )	Access the field as a hash referencing an object attachment. Returns the provided default on error.
FCbObjectId	AsObjectId ( const FCbObjectId& Default )	Access the field as an object identifier. Returns the provided default on error.
FCbObjectVie...	AsObjectView()	Access the field as an object. Defaults to an empty object on error.
void	Assign ( const void* InData, const ECbFieldType InType )	Assign a field from a pointer to its data and an optional externally-provided type.
FUtf8StringV...	AsString ( FUtf8StringView Default )	Access the field as a string. Returns the provided default on error.
FTimespan	AsTimeSpan ( FTimespan Default )	Access the field as a timespan. Returns the provided default on error.
FTimespan	AsTimeSpan()	Access the field as a timespan. Returns an empty timespan on error.
int64	AsTimeSpanTicks ( int64 Default )	Access the field as a timespan tick count. Returns the provided default on error.
uint16	AsUInt16 ( uint16 Default )	Access the field as a uint16. Returns the provided default on error.
uint32	AsUInt32 ( uint32 Default )	Access the field as a uint32. Returns the provided default on error.
uint64	AsUInt64 ( uint64 Default )	Access the field as a uint64. Returns the provided default on error.
uint8	AsUInt8 ( uint8 Default )	Access the field as a uint8. Returns the provided default on error.
FGuid	AsUuid ( const FGuid& Default )	Access the field as a UUID. Returns the provided default on error.
FGuid	AsUuid()	Access the field as a UUID. Returns a nil UUID on error.
FCbFieldView...	begin()	DO NOT USE DIRECTLY. These functions enable range-based for loop support.
void	CopyTo ( FArchive& Ar )	Copy the field into an archive, including its type and name.
void	CopyTo ( FMutableMemoryView Buffer )	Copy the field into a buffer of exactly GetSize() bytes, including the type and name.
FCbFieldView...	CreateViewIterator()	Create an iterator for the fields of an array or object, otherwise an empty iterator.
constexpr FC...	end()
bool	Equals ( const FCbFieldView& Other )	Whether this field is identical to the other field.
constexpr EC...	GetError()	The type of error that occurred on the last field access, or None.
FIoHash	GetHash()	Calculate the hash of the field, including the type and name.
constexpr FU...	GetName()	Returns the name of the field if it has a name, otherwise an empty view.
uint64	GetSize()	Returns the size of the field in bytes, including the type and name.
constexpr EC...	GetType()	Returns the type of the field excluding flags.
constexpr EC...	GetTypeWithFlags()	Returns the type of the field including flags.
FCbValue	GetValue()	Returns the value for unchecked access. Prefer the typed accessors below.
constexpr co...	GetValueData()	Returns the start of the value.
const void &...	GetValueEnd()	Returns the end of the value.
uint64	GetValueSize()	Returns the size of the value in bytes, which is the field excluding the type and name.
FMemoryView	GetValueView()	Returns a view of the value, which excludes the type and name.
FMemoryView	GetView()	Returns a view of the field, including the type and name when present.
FMemoryView	GetViewNoType()	Returns a view of the name and value, which excludes the type.
constexpr bo...	HasError()	Whether the last field access encountered an error.
constexpr bo...	HasName()	True if the field has a name.
constexpr bo...	HasValue()	Whether the field has a value.
constexpr bo...	IsArray()
constexpr bo...	IsAttachment()
constexpr bo...	IsBinary()
constexpr bo...	IsBinaryAttachment()
constexpr bo...	IsBool()
constexpr bo...	IsCustomById()
constexpr bo...	IsCustomByName()
constexpr bo...	IsDateTime()
constexpr bo...	IsFloat()	Whether the field is a float, or integer that supports implicit conversion.
constexpr bo...	IsHash()
constexpr bo...	IsInteger()	Whether the field is an integer of unspecified range and sign.
constexpr bo...	IsNull()
constexpr bo...	IsObject()
constexpr bo...	IsObjectAttachment()
constexpr bo...	IsObjectId()
constexpr bo...	IsString()
constexpr bo...	IsTimeSpan()
constexpr bo...	IsUuid()
void	IterateAttachments ( FCbFieldVisitor Visitor )	Invoke the visitor for every attachment in the field.
bool	TryGetView ( FMemoryView& OutView )	Try to get a view of the field as it would be serialized, such as by CopyTo.

Operators

		Name	Description
	constexpr	operator bool()	Whether the field has a value.
	FCbFieldView	operator[] ( FUtf8StringView Name )	Find a field of an object by case-sensitive name comparison, otherwise a field with no value.