package pkg

import (
	"reflect"
	"unsafe"
)

/*
    使用 unsafe 的方式转换 bytes string

bench-review
cpu: Intel(R) Core(TM) i7-10700 CPU @ 2.90GHz
    BenchmarkB2sFast
    BenchmarkB2sFast       	1000000000	         0.2215 ns/op	       0 B/op	       0 allocs/op
    BenchmarkB2sFast-4     	1000000000	         0.2188 ns/op	       0 B/op	       0 allocs/op
    BenchmarkB2sFast-8     	1000000000	         0.2187 ns/op	       0 B/op	       0 allocs/op
    BenchmarkB2sFast-16    	1000000000	         0.2190 ns/op	       0 B/op	       0 allocs/op
    BenchmarkB2sStd
    BenchmarkB2sStd        	46913166	        25.01 ns/op	      48 B/op	       1 allocs/op
    BenchmarkB2sStd-4      	53604633	        21.23 ns/op	      48 B/op	       1 allocs/op
    BenchmarkB2sStd-8      	53374398	        21.27 ns/op	      48 B/op	       1 allocs/op
    BenchmarkB2sStd-16     	55482764	        21.51 ns/op	      48 B/op	       1 allocs/op
    BenchmarkS2BFast
    BenchmarkS2BFast       	1000000000	         0.2187 ns/op	       0 B/op	       0 allocs/op
    BenchmarkS2BFast-4     	1000000000	         0.2187 ns/op	       0 B/op	       0 allocs/op
    BenchmarkS2BFast-8     	1000000000	         0.2184 ns/op	       0 B/op	       0 allocs/op
    BenchmarkS2BFast-16    	1000000000	         0.2188 ns/op	       0 B/op	       0 allocs/op
    BenchmarkS2BStd
    BenchmarkS2BStd        	56877040	        21.31 ns/op	      48 B/op	       1 allocs/op
    BenchmarkS2BStd-4      	65751385	        17.43 ns/op	      48 B/op	       1 allocs/op
    BenchmarkS2BStd-8      	67193628	        17.55 ns/op	      48 B/op	       1 allocs/op
    BenchmarkS2BStd-16     	66711826	        17.61 ns/op	      48 B/op	       1 allocs/op

*/

// B2S converts byte slice to a string without memory allocation.
// See https://groups.google.com/forum/#!msg/Golang-Nuts/ENgbUzYvCuU/90yGx7GUAgAJ .
//
// Note it may break if string and/or slice header will change
// in the future go versions.
func B2S(b []byte) string {
	/* #nosec G103 */
	return *(*string)(unsafe.Pointer(&b))
}

// S2B converts string to a byte slice without memory allocation.
//
// Note it may break if string and/or slice header will change
// in the future go versions.
func S2B(s string) (b []byte) {
	/* #nosec G103 */
	bh := (*reflect.SliceHeader)(unsafe.Pointer(&b))
	/* #nosec G103 */
	sh := (*reflect.StringHeader)(unsafe.Pointer(&s))
	bh.Data = sh.Data
	bh.Cap = sh.Len
	bh.Len = sh.Len
	return b
}