C - URL encoding

Question

Is there a simple way to do URL encode in C? I'm using libcurl but I haven't found a method. Specifically, I need to do percent escapes.

Answer 1

In C based on wikipedia, without having to alloc and free. Make sure output buffer is at least 3X input URL string. Usually you only need to encode up to maybe 4K as URLs tend to be short so just do it on the stack.

char rfc3986[256] = {0};
char html5[256] = {0};

void url_encoder_rfc_tables_init(){

    int i;

    for (i = 0; i < 256; i++){

        rfc3986[i] = isalnum( i) || i == '~' || i == '-' || i == '.' || i == '_' ? i : 0;
        html5[i] = isalnum( i) || i == '*' || i == '-' || i == '.' || i == '_' ? i : (i == ' ') ? '+' : 0;
    }
}

char *url_encode( char *table, unsigned char *s, char *enc){

    for (; *s; s++){

        if (table[*s]) *enc = table[*s];
        else sprintf( enc, "%%%02X", *s);
        while (*++enc);
    }

    return( enc);
}

Use it like this

url_encoder_rfc_tables_init();

url_encode( html5, url, url_encoded);

Answer 2

curl_escape

which apparently has been superseded by

curl_easy_escape