safeish

README

honnef.co/go/safeish

Somewhat safe unsafe helpers for Go. See documentation.

Documentation

Overview

Package safeish provides safe-ish unsafe helpers.

Index

• func AsBytes[E any, T *E](ptr T) []byte
• func Cast[Dst, Src any](x Src) Dst
• func FindNull(s *byte) int
• func Index[E any, S ~[]E, Int constraints.Integer](ptr S, idx Int) *E
• func SliceCast[Dst ~[]DstE, Src ~[]SrcE, DstE, SrcE any](x Src) Dst
• func SliceCastPtr[Dst ~*DstE, Src ~[]SrcE, DstE, SrcE any](x Src) Dst

Examples

• SliceCast

Functions

func AsBytes

func AsBytes[E any, T *E](ptr T) []byte

AsBytes returns the underlying byte representation of the value pointed to by ptr.

func Cast

func Cast[Dst, Src any](x Src) Dst

Cast casts x from type Src to type Dst. It uses generics to provide a syntactic alternative to the common unsafe.Pointer conversion pattern.

Example:

var x Foo

_ = Cast[Bar](x)
// the above is identical to the below
_ = *(*Bar)(unsafe.Pointer(&x))

func FindNull

func FindNull(s *byte) int

func Index

func Index[E any, S ~[]E, Int constraints.Integer](ptr S, idx Int) *E

Index provides unsafe slice indexing without bounds checks. This function has absolutely no safety checks.

func SliceCast

func SliceCast[Dst ~[]DstE, Src ~[]SrcE, DstE, SrcE any](x Src) Dst

SliceCast casts a slice of underlying type []SrcE to a slice of underlying type []DstE, automatically adjusting the length and capacity based on the ratio of sizeof(SrcE) to sizeof(DstE). sizeof(DstE) may be both larger or smaller than sizeof(SrcE).

The ratio is expected to be integer, but non-integer ratios will not cause invalid memory accesses.

The type parameters are ordered so that at most the first one has to be provided explicitly.

SliceCast is fully inlinable.

Example

type S struct {
	A, B uint32
}

x := make([]byte, 32, 60)
s := SliceCast[[]S](x)
fmt.Println(len(s), cap(s))

Output:

4 7

func SliceCastPtr

func SliceCastPtr[Dst ~*DstE, Src ~[]SrcE, DstE, SrcE any](x Src) Dst

SliceCastPtr casts a slice of underlying type []SrcE to a pointer of underlying type *DstE to the slice's first element, or nil if the slice's capacity is 0. It ensures that the pointer doesn't extend past the end of the slice.