Go语言中[]byte和string类型相互转换时的性能分析和优化 | yoko blog

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type slice struct {
	array unsafe.Pointer
	len   int
	cap   int
}

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type stringStruct struct {
	str unsafe.Pointer
	len int
}

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func slicebytetostringtmp(b []byte) string {
	// Return a "string" referring to the actual []byte bytes.
	// This is only for use by internal compiler optimizations
	// that know that the string form will be discarded before
	// the calling goroutine could possibly modify the original
	// slice or synchronize with another goroutine.
	// First such case is a m[string(k)] lookup where
	// m is a string-keyed map and k is a []byte.
	// Second such case is "<"+string(b)+">" concatenation where b is []byte.
	// Third such case is string(b)=="foo" comparison where b is []byte.

if raceenabled && len(b) > 0 {
		racereadrangepc(unsafe.Pointer(&b[0]),
			uintptr(len(b)),
			getcallerpc(unsafe.Pointer(&b)),
			funcPC(slicebytetostringtmp))
	}
	return *(*string)(unsafe.Pointer(&b))
}

func stringtoslicebytetmp(s string) []byte {
	// Return a slice referring to the actual string bytes.
	// This is only for use by internal compiler optimizations
	// that know that the slice won't be mutated.
	// The only such case today is:
	// for i, c := range []byte(str)

str := (*stringStruct)(unsafe.Pointer(&s))
	ret := slice{array: unsafe.Pointer(str.str), len: str.len, cap: str.len}
	return *(*[]byte)(unsafe.Pointer(&ret))
}