Implement WitnessCalc in native apps Pt.1

In this short guide we will roughly implement generated witnesscalc .cpp files from circom in react-native app.

I'll do it in

And finally, we will use

• configure path in your .bashrc or .zshrc config file
  
  

• clone




• follow readme "preparation" to install necessary deps

Now let's take a look at src folder:

1. create witnesscalc_auth.cpp and witnesscalc_auth.h files under src folder

You could check all the same files, their content is exact same, except the name, so we have done like so.

1. now add these files to ./CMakeLists.txt
   

as before, you should notice, that this code is the same as code above in this file, so we just copied them and changed name

And these steps should be done for every .cpp & .dat files you will add.

in this case you can use

in root ./CMakeLists.txt file

and also except src/witnesscalc.h, it’s necessary too

Now you can run these commands to compile your executable files

./build_gmp.sh android // only once

make android // every time u want to compile new wtns calcs

The result:

to turn it on.

We will implement our generated file in for that.

so let's start

npx create-react-native-library@latest wtnscalcs

this is what we see after scaffolding our module, and to modify the code, it’s would be better to open via android-studio

we ARE NOT going to open this android folder, but should open a root android folder, this one:

here is our module, and by modifying it, our code in ./modules/[module]/android folder will be changed too

so what we see now:

and the cmake structure which points to our CMakeLists.txt, which is register our future cpp file with logic

and then .h file for it

Now, let’s back to our "frontend perspective" e.g IDE or editor where your react-native project are, and take a look in to spec file in module, which responsible to register our module with native code and define top-level interface

By defining methods in this "Spec" interface

And by exposing method from index.tsx we will be able to call method from module as a regular npm-pkg

Nice, now let's jump straight in to hard mode:

let's define what we need:

1) first of all, at the very top level we have "inputs" which witness calculator will accept in the future

2) we need to send these inputs to our native module, pass it to .so file

3) execute and return bytes, it should be the same as circom compiles .wtns file, but we will keep file content in ram, instead of file

Now, let's write this implementation code, and leave it empty for a while

and paste there our auth.dat file

1. get back to "Frontend perspective", create lib folder under modules/android directory and paste there a .so file

cmake_minimum_required(VERSION 3.4.1)

project(RnWtnscalcs)



set (CMAKE_VERBOSE_MAKEFILE ON)

set (CMAKE_CXX_STANDARD 14)



add_library(rn-wtnscalcs            SHARED

            ../cpp/rn-wtnscalcs.cpp

            cpp-adapter.cpp

)



# Specifies a path to native header files.

include_directories(

            ../cpp

)



link_directories(lib)



add_library(auth SHARED IMPORTED)

set_target_properties(auth PROPERTIES IMPORTED_LOCATION ${CMAKE_SOURCE_DIR}/lib/libwitnesscalc_auth.so)



target_link_libraries(rn-wtnscalcs

        android

        auth)

what we have done:

1. We linked directories where we've placed our .so file


2. Registered our .so file as library


3. And finally ‘target_link_libraries’ will compile it for us in one executable file, which we can call in runtime

After these steps we will be able to execute .so file in runtime

let's write the code to call it:

these steps will create binded function in our rn-wtnscalcs.cpp file, but let’s move it to cpp-adapter.cpp

and use it in implemented function in our module.kt file, which we have leaved empty:

Part 2 (ios)