souffle

main.go

package main

import (
	"fmt"
	"runtime"

	"github.com/cwarden/souffle-go-example/SwigInterface"
)

var (
	// Use a channel to pass data from the Souffle program
	// Can be modified to be a slice or whatever data type you require
	// The channel will be initialized on main
	ch chan int64
)

func callSouffle() {
	// Not sure if instantiating multiple times is something that works in this context
	// I've simplified the scenario and focused the scenario on a single instance for now:
	p := SwigInterface.NewInstance("example")
	p.SetNumThreads(int64(runtime.NumCPU()))

	if p.Swigcptr() == 0 {
		panic("Souffle program not found")
	}
	p.LoadAll(".")

	edges := p.GetRelation("edge")

	edges.Purge()

	t := edges.NewTuple()
	t.PutInteger(4)
	t.PutInteger(5)
	t.Insert()
	SwigInterface.DeleteSWIGSouffleTuple(t)

	t = edges.NewTuple()
	t.PutInteger(5)
	t.PutInteger(6)
	t.Insert()
	SwigInterface.DeleteSWIGSouffleTuple(t)

	t = edges.NewTuple()
	t.PutInteger(1)
	t.PutInteger(4)
	t.Insert()
	SwigInterface.DeleteSWIGSouffleTuple(t)
	SwigInterface.DeleteSWIGSouffleRelation(edges)

	p.Run()
	paths := p.GetRelation("path")

	arity := paths.GetArity()
	size := paths.Size()

	// Not sure how you use this value, I've added this condition
	// to avoid Golang compiler errors:
	if arity == 0 {
	}
	var i, j uint
	for i = 0; i < size; i++ {
		tuple := paths.Next()
		tuple.GetInteger(j)
		n := tuple.GetInteger(j)

		// Here I'm just writing the tuple.GetInteger value to the channel
		ch <- n
		SwigInterface.DeleteSWIGSouffleTuple(tuple)
	}
	SwigInterface.DeleteSWIGSouffleRelation(paths)
	SwigInterface.DeleteSWIGSouffleProgram(p)

	// Write -1 to the channel as a way of signaling that callSouffle finished:
	ch <- -1
}

func main() {
	// Initialize the channel:
	ch = make(chan int64)
	// Close the channel when this main function ends:
	defer close(ch)

	// Use a goroutine to handle everything:
	go callSouffle()

	// This main loop would just wait for data to be available on the channel:
	for {
		n := <-ch
		if n == -1 {
			fmt.Println("Got -1, closing the channel, main program returns")
			break
		}
		// Use incoming n values:
		// fmt.Println("Got:", n)
	}
}