jstring std::string互转

#include <string>
#include <locale>
#include <codecvt>

static std::string UTF16StringToUTF8String(const char16_t* chars, size_t len) {
    std::u16string u16_string(chars, len);
    return std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>{}
            .to_bytes(u16_string);
}

std::string JavaStringToString(JNIEnv* env, jstring str) {
    if (env == nullptr || str == nullptr) {
        return "";
    }
    const jchar* chars = env->GetStringChars(str, NULL);
    if (chars == nullptr) {
        return "";
    }
    std::string u8_string = UTF16StringToUTF8String(
            reinterpret_cast<const char16_t*>(chars), env->GetStringLength(str));
    env->ReleaseStringChars(str, chars);
    return u8_string;
}

static std::u16string UTF8StringToUTF16String(const std::string& string) {
    return std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>{}
            .from_bytes(string);
}

jstring StringToJavaString(JNIEnv* env,
                           const std::string& u8_string) {
    std::u16string u16_string = UTF8StringToUTF16String(u8_string);
    auto result =env->NewString(reinterpret_cast<const jchar*>(u16_string.data()),
                                u16_string.length());
    return result;
}

• https://github.com/CentForever/AndroidJniObjectTest.git