golang/sample/pack_func_closure_return.go

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/*!
 * \brief Sample golang application to demonstrate go-closure returned from a callback function.
 * \file pack_func_closure_return.go
 */

package main

import (
    "fmt"
    "./gotvm"
)

// sampleFunctionCb returns a function closure which is embed as packed function in TVMValue.
func sampleFunctionCb(args ...*gotvm.Value) (retVal interface{}, err error) {
    funccall := func (cargs ...*gotvm.Value) (fret interface{}, ferr error) {
        for _, v := range cargs {
            fmt.Printf("ARGS:%T : %v\n", v.AsInt64(), v.AsInt64())
        }
        val1 := cargs[0].AsInt64()
        val2 := cargs[1].AsInt64()
        fret = int64(val1+val2)
        return
    }
    retVal = funccall
    return
}

// main
func main() {
    // Not passing a function name implicitely
    // picks the name from reflection as "main.sampleDunctionCb"
    gotvm.RegisterFunction(sampleFunctionCb);
    fmt.Printf("Registered: sampleFunctionCb\n")

    // Get registered global function
    funp, err := gotvm.GetGlobalFunction("main.sampleFunctionCb")
    if err != nil {
        fmt.Print(err)
        return
    }
    fmt.Printf("GetGlobalFunction: main.sampleFunctionCb - Success\n")

    // Call function
    result, err := funp.Invoke()
    if err != nil {
        fmt.Print(err)
        return
    }
    fmt.Printf("Invoked main.sampleFunctionCb via Function handle\n")

    pfunc := result.AsFunction()
    fmt.Printf("Function Handle received via Packed Function call:%T - %v \n", pfunc, pfunc)

    pfuncRet, err := pfunc.Invoke(30, 40)
    fmt.Printf("Invoked closure inside sampleFunctionCb result:%v\n", pfuncRet.AsInt64())
}