How to understand StringToSliceByte in rpcx lib?

php editor Zimo will explain to you how to understand StringToSliceByte in rpcx lib. StringToSliceByte is a function in rpcx lib, its function is to convert a string into a byte slice. Before understanding this function, we need to understand the basic concepts and usage of rpcx lib. rpcx lib is a high-performance distributed RPC framework that helps developers quickly build distributed applications. The StringToSliceByte function converts a string into a byte slice, which is very useful when transmitting data in distributed applications. Understanding the usage and principles of this function can help developers better utilize rpcx lib to build high-performance distributed applications.

Question content

The following code snippet comes from rpcx lib.

func stringtoslicebyte(s string) []byte {
    x := (*[2]uintptr)(unsafe.pointer(&s))
    h := [3]uintptr{x[0], x[1], x[1]}
    return *(*[]byte)(unsafe.pointer(&h))
}

This code is used to efficiently convert a string into a slice of bytes, but how does it work? Can someone provide a thorough analysis of this code?

By the way, there is a more concise implementation:

func tobytes(s string) []byte {
    return *(*[]byte)(unsafe.pointer(&s))
}

It shows that the following code also works:

func StringToSliceByte(s string) []byte {
    x := (*[1]int8)(unsafe.Pointer(&s))
    return *(*[]byte)(unsafe.Pointer(&x[0]))
}

Solution

The string contains a pointer to the underlying array containing the string data and the string length. A slice contains a pointer to the underlying array, the length and capacity of the slice.

OK:

x := (*[2]uintptr)(unsafe.pointer(&s))

Access the internal representation of the string s.

Operation:

h := [3]uintptr{x[0], x[1], x[1]}

Create a slice h, pointing to the underlying array of s (x[0]), with a length and capacity equal to the string lenhth x[ 1].

It then returns it as a slice.

It can be seen from the use of unsafe that this is an unsafe code and it may not run in higher versions of go. It relies on the internal representation of the data type. It also violates the fact that strings are immutable in Go, returning the underlying array of strings as a slice. This is an optimization that prevents copying by sacrificing type safety and language assumptions. Avoid it.

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