Documentation
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Overview ¶
Package value provides runtime utilities for working with generic type parameters as payload values in bart data structures.
The package offers three main categories of utilities:
Zero-Sized Type (ZST) Detection ¶
IsZST[V] detects whether a type parameter V is a zero-sized type (such as struct{} or [0]byte). This serves two purposes:
- Runtime validation: Fast[V] cannot work correctly with zero-sized types and must reject them. PanicOnZST enables a safety check that panics during Fast.Insert and Fast.InsertPersist operations.
- Debug output clarity: Zero-sized types carry no information in their values. Omitting them from dumps and prints reduces line noise and improves readability.
Value Equality ¶
The Equaler[V] interface and Equal function enable custom equality logic for payload values. When V implements Equaler[V], the Equal function uses that implementation, avoiding the potentially expensive reflect.DeepEqual.
Value Cloning ¶
The Cloner[V] interface and associated functions (CloneFnFactory, CloneVal, CopyVal) support deep copying of payload values for persistent operations. When V implements Cloner[V], bart methods like InsertPersist, DeletePersist, and UnionPersist use the Clone method to create independent copies.
This is an internal package used by the bart data structure implementation.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func CloneVal ¶
func CloneVal[V any](val V) V
CloneVal returns a deep clone of val by calling Clone when val implements Cloner[V]. If val does not implement Cloner[V] or the Cloner receiver is nil (val is a nil pointer), CloneVal returns val unchanged.
func Equal ¶
Equal compares two values of type V for equality. If V implements Equaler[V], that custom equality method is used, avoiding the potentially expensive reflect.DeepEqual. Otherwise, reflect.DeepEqual is used as a fallback.
func IsZST ¶
IsZST reports whether type V is a zero-sized type (ZST).
Zero-sized types such as struct{}, [0]byte, or structs/arrays with no fields occupy no memory. The Go runtime optimizes allocations of ZSTs by returning pointers to the same memory address (typically runtime.zerobase).
This function exploits that optimization: it allocates two instances of V and compares their addresses. If the addresses are equal, V must be a ZST, since distinct non-zero-sized allocations would have different addresses.
The helper escapeToHeap ensures both allocations reach the heap and prevents the compiler from proving address equality at compile time, which would invalidate the runtime check.
func PanicOnZST ¶
func PanicOnZST[V any]()
PanicOnZST panics if V is a zero sized type. bart.Fast must reject zero-sized types as payload.
Types ¶
type CloneFunc ¶
type CloneFunc[V any] func(V) V
CloneFunc is a type definition for a function that takes a value of type V and returns the (possibly cloned) value of type V.
func CloneFnFactory ¶
CloneFnFactory returns a CloneFunc. If V implements Cloner[V], the returned function should perform a deep copy using Clone(), otherwise it returns nil.
type Cloner ¶
type Cloner[V any] interface { Clone() V }
Cloner is an interface that enables deep cloning of values of type V. If a value implements Cloner[V], Table methods such as InsertPersist, ModifyPersist, DeletePersist, UnionPersist, Union and Clone will use its Clone method to perform deep copies.
type Equaler ¶
Equaler is a generic interface for types that can decide their own equality logic. It can be used to override the potentially expensive default comparison with reflect.DeepEqual.
Source Files