Generating FPGA Interchange Format Parsers/Deparsers for C++

[clavin-xlnx]

Generating the C++ parser/deparser code for the FPGA Interchange in Cap’n Proto is pretty simple. I was able to do it in just a couple of minutes. In my Ubuntu instance (WSL), I did the following:

sudo apt-get install capnproto
git clone https://github.com/chipsalliance/fpga-interchange-schema.git
cd fpga-interchange-schema/interchange
mkdir capnp
wget https://raw.githubusercontent.com/capnproto/capnproto/v2/c%2B%2B/src/capnp/c%2B%2B.capnp -O capnp/c++.capnp

Next, you will need to modify the *.capnp schema files and comment out the 3 Java reference lines and update the path of the c++.capnp file, for example the top of my DeviceResources.capnp looks like this:

#using Java = import "/capnp/java.capnp";
using Ref = import "References.capnp";
using Dir = import "LogicalNetlist.capnp";
#$Java.package("com.xilinx.rapidwright.interchange");
#$Java.outerClassname("DeviceResources");

using Cxx = import "capnp/c++.capnp";
$Cxx.namespace("DeviceResources");

Then you can run the Cap’n Proto compiler:

capnp compile -oc++ *.capnp

Which will generate the C++ and header files you need:

$ ls -l
total 1724
-rw-r--r-- 1 rapidwright rapidwright  27935 Oct  9 11:48 DeviceResources.capnp
-rw-r--r-- 1 rapidwright rapidwright 427657 Oct  9 11:49 DeviceResources.capnp.c++
-rw-r--r-- 1 rapidwright rapidwright 779377 Oct  9 11:49 DeviceResources.capnp.h
-rw-r--r-- 1 rapidwright rapidwright   4444 Oct  9 11:49 LogicalNetlist.capnp
-rw-r--r-- 1 rapidwright rapidwright  88248 Oct  9 11:49 LogicalNetlist.capnp.c++
-rw-r--r-- 1 rapidwright rapidwright 140776 Oct  9 11:49 LogicalNetlist.capnp.h
-rw-r--r-- 1 rapidwright rapidwright   4380 Oct  9 11:49 PhysicalNetlist.capnp
-rw-r--r-- 1 rapidwright rapidwright 106000 Oct  9 11:49 PhysicalNetlist.capnp.c++
-rw-r--r-- 1 rapidwright rapidwright 150939 Oct  9 11:49 PhysicalNetlist.capnp.h
-rw-r--r-- 1 rapidwright rapidwright    866 Oct  9 11:48 References.capnp
-rw-r--r-- 1 rapidwright rapidwright   3683 Oct  9 11:49 References.capnp.c++
-rw-r--r-- 1 rapidwright rapidwright   1131 Oct  9 11:49 References.capnp.h
drwxr-xr-x 2 rapidwright rapidwright   4096 Oct  9 11:46 capnp

Comment below if you have any issues or suggestions.

[codepilot]

I made capnp reader for node. js, I will put public repo for it shortly. It's pretty quick at making an SVG of the device for viewing it in the browser. I used the c++ capnp and more c++ to make the typescript. I am available to help anyone with the process and working with capnp in more languages if needed.

Daniel