jstring(JNI) to std::string(c++) with utf8 characters

Question

How to convert jstring (JNI) to std::string (c++) with utf8 characters?

this is my code. it worked with non-utf8 characters, but i

Answer 1

explanation is here:

http://www.club.cc.cmu.edu/~cmccabe/blog_jni_flaws.html https://developer.android.com/training/articles/perf-jni (Region calls)

jsize
string_j2c(JNIEnv *env, jstring p, char *buffer) {

    if (buffer != NULL) {
        // Returns the length (the count of Unicode characters) of a
        // Java string.
        const jsize len = (*env).GetStringLength(p);

        // Translates 'len' number of Unicode characters into modified
        // UTF-8 encoding and place the result in the given buffer.
        (*env).GetStringUTFRegion(p, 0, len, buffer);

        // Returns JNI_TRUE when there is a pending exception;
        // otherwise, returns JNI_FALSE.
        const jboolean is_error = (*env).ExceptionCheck();

        if (is_error == JNI_TRUE) {
            return -1;
        }
    }

    // Returns the length in bytes of the modified UTF-8
    // representation of a string.
    const jsize len = (*env).GetStringUTFLength(p);
    return len;
}

const jsize len = string_j2c(env, p, NULL);
char buffer[len];
const jsize ret = string_j2c(env, p, buffer);

if (ret == -1) { // error
}
else {
    __android_log_print(ANDROID_LOG_DEBUG, "Native", "%s", buffer);
}