示例：C++

/** Vivox Token Generation Example - C++* Note: This example uses C++11, and is written to not use external libraries to demonstrate the token generation process.* However, because HMACSHA256 is required, this example uses OpenSSL 1.1.0+.**/#include <openssl/sha.h>#include <openssl/evp.h>#include <openssl/hmac.h>#include <iostream>#include <iomanip>#include <sstream>#include <string>using namespace std;typedef unsigned char uchar;static const string b = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_+/";/** You can use Base64URL encoding or Base64 and URL encoding libraries in place of this implementation* Note: Any trailing ='s must be removed from the encoded string.*/static string base64_encode(const string &in){    string out;    int val = 0, valb = -6;    for (const char c : in) {        val = (val << 8) + static_cast<unsigned char>(c);        valb += 8;        while (valb >= 0) {            out.push_back(b[(val >> valb) & 0x3F]);            valb -= 6;        }    }    if (valb >- 6) out.push_back(b[((val << 8) >> (valb + 8))& 0x3F]);    return out;}#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)static HMAC_CTX *HMAC_CTX_new(void){    HMAC_CTX *ctx = static_cast<HMAC_CTX *>(OPENSSL_malloc(sizeof(*ctx)));    if (ctx != nullptr) {        HMAC_CTX_init(ctx);    }    return ctx;}static void HMAC_CTX_free(HMAC_CTX *ctx){    if (ctx != nullptr) {        HMAC_CTX_cleanup(ctx);        OPENSSL_free(ctx);    }}#endif/** Uses OpenSSL 1.1.0+ to encode data with a secret using HMAC SHA-256*/string hmac(string key, string msg){    unsigned char hash[32];    HMAC_CTX *hmac = HMAC_CTX_new();    HMAC_Init_ex(hmac, &key[0], static_cast<int>(key.length()), EVP_sha256(), nullptr);    HMAC_Update(hmac, reinterpret_cast<const unsigned char *>(&msg[0]), msg.length());    unsigned int len = 32;    HMAC_Final(hmac, hash, &len);    HMAC_CTX_free(hmac);    stringstream ss;    ss << setfill('0');    for (unsigned int i = 0; i < len; i++) {        ss << hash[i];    }    return ss.str();}static string vx_generate_token(const string &key, const string &issuer, int exp, const string &vxa, int vxi, const string &f, const string &t){    // Header is static - base64url encoded {}    string header = base64_encode("{}");  // Can also be defined as a constant "e30"    // Create payload and base64 encode    stringstream ss;    ss << "{ \"iss\": \"" << issuer << "\",";    ss << "\"exp\": " << exp << ",";    ss << "\"vxa\": \"" << vxa << "\",";    ss << "\"vxi\": " << vxi << ",";    ss << "\"t\": \"" << t << "\",";    ss << "\"f\": \"" << f << "\" }";    string payload = base64_encode(ss.str());    // Join segments to prepare for signing    string to_sign = header + "." + payload;    // Sign token with key and HMACSHA256, then base64 encode    string signed_payload = base64_encode(hmac(key, to_sign));    // Combine header and payload with signature    return to_sign + "." + signed_payload;}int main(){    string token = vx_generate_token("secret", "issuer", 1559359105, "join", 123456, "sip:.username.@domain.vivox.com", "sip:confctl-g-channelname@domain.vivox.com");    cout << token << endl;    return 0;}