Golang：给定常量值的名称

Question

How do you get the name of a constant given its value ?

More specifically (and to get a more readable understanding), I'm working with the crypto/tls package. Cipher suites are defined as constants:

const (
    TLS_RSA_WITH_RC4_128_SHA            uint16 = 0x0005
    TLS_RSA_WITH_3DES_EDE_CBC_SHA       uint16 = 0x000a
    TLS_RSA_WITH_AES_128_CBC_SHA        uint16 = 0x002f
    TLS_RSA_WITH_AES_256_CBC_SHA        uint16 = 0x0035
    TLS_ECDHE_RSA_WITH_RC4_128_SHA      uint16 = 0xc011
    TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA uint16 = 0xc012
    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA  uint16 = 0xc013
    TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA  uint16 = 0xc014
)

After a successful handshake with a server, I can get to the Ciphersuite agreed on through the connection:

c, _ := tls.Dial("tcp", "somedomain.com:443", nil)
// Suppose everything went right

// This is the Ciphersuite for the conn:
cipher := c.ConnectionState().Ciphersuite

cipher here is an uint16. Is there a way to display it as a string, for instance TLS_RSA_WITH_3DES_EDE_CBC_SHA if that's what was agreed upon ?

Answer 1

I am afraid that is not possible.
The constants are resolved at compile time and there is nothing in the reflect package that allows you to retrieve the name.

What I suggest is creating a map with the names:

var constLookup = map[uint16]string{
    tls.TLS_RSA_WITH_RC4_128_SHA:      `TLS_RSA_WITH_RC4_128_SHA`,
    tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA: `TLS_RSA_WITH_3DES_EDE_CBC_SHA`,
    ...
}