Function js::jsapi::JS_GetStringEncodingLength

pub unsafe extern "C" fn JS_GetStringEncodingLength(
    cx: *mut JSContext, 
    str: *mut JSString
) -> usize

Get number of bytes in the string encoding (without accounting for a terminating zero bytes. The function returns (size_t) -1 if the string can not be encoded into bytes and reports an error using cx accordingly.