Snippet

Zero-Copy String to Slice Inspection via Unsafe Pointer Memory Primitives

Modern Go (1.20+) provides unsafe.StringData and unsafe.Slice to construct byte slice headers directly over immutable string backing arrays without heap allocations. While zero-copy conversions enhance read operations, mutating the resulting byte slice triggers undefined runtime behavior due to writing into read-only memory segments.

snippet.go

package main
 
import (
	"fmt"
	"reflect"
	"unsafe"
)
 
func readOnlyByteView(s string) []byte {
	if len(s) == 0 {
		return nil
	}
	return unsafe.Slice(unsafe.StringData(s), len(s))
}
 
func inspectSliceHeader(b []byte) (uintptr, int, int) {
	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&b))
	return hdr.Data, hdr.Len, hdr.Cap
}
 
func main() {
	str := "Immutable Memory String"
	view := readOnlyByteView(str)
	ptr, l, c := inspectSliceHeader(view)
	fmt.Printf("Address: 0x%x, Length: %d, Capacity: %d\n", ptr, l, c)
	fmt.Printf("Content: %s\n", string(view))
}

Breakdown

return unsafe.Slice(unsafe.StringData(s), len(s))

Creates a slice view pointing to the underlying bytes of string 's' without copying memory.

hdr := (*reflect.SliceHeader)(unsafe.Pointer(&b))

Casts the slice address to access structural header metadata fields directly.

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Zero-Copy String to Slice Inspection via Unsafe Pointer Memory Primitives

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