github.com/kchristidis/fabric@v1.0.4-0.20171028114726-837acd08cde1/examples/chaincode/go/invokereturnsvalue/invokereturnsvalue.go (about)

     1  /*
     2  Copyright IBM Corp. 2016 All Rights Reserved.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8  		 http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package main
    18  
    19  //WARNING - this chaincode's ID is hard-coded in chaincode_example04 to illustrate one way of
    20  //calling chaincode from a chaincode. If this example is modified, chaincode_example04.go has
    21  //to be modified as well with the new ID of chaincode_example02.
    22  //chaincode_example05 show's how chaincode ID can be passed in as a parameter instead of
    23  //hard-coding.
    24  
    25  import (
    26  	"fmt"
    27  	"strconv"
    28  
    29  	"github.com/hyperledger/fabric/core/chaincode/shim"
    30  	pb "github.com/hyperledger/fabric/protos/peer"
    31  )
    32  
    33  // SimpleChaincode example simple Chaincode implementation
    34  type SimpleChaincode struct {
    35  }
    36  
    37  // Init method of chaincode
    38  func (t *SimpleChaincode) Init(stub shim.ChaincodeStubInterface) pb.Response {
    39  	_, args := stub.GetFunctionAndParameters()
    40  	var A, B string    // Entities
    41  	var Aval, Bval int // Asset holdings
    42  	var err error
    43  
    44  	if len(args) != 4 {
    45  		return shim.Error("Incorrect number of arguments. Expecting 4")
    46  	}
    47  
    48  	// Initialize the chaincode
    49  	A = args[0]
    50  	Aval, err = strconv.Atoi(args[1])
    51  	if err != nil {
    52  		return shim.Error("Expecting integer value for asset holding")
    53  	}
    54  	B = args[2]
    55  	Bval, err = strconv.Atoi(args[3])
    56  	if err != nil {
    57  		return shim.Error("Expecting integer value for asset holding")
    58  	}
    59  	fmt.Printf("Aval = %d, Bval = %d\n", Aval, Bval)
    60  
    61  	// Write the state to the ledger
    62  	err = stub.PutState(A, []byte(strconv.Itoa(Aval)))
    63  	if err != nil {
    64  		return shim.Error(err.Error())
    65  	}
    66  
    67  	err = stub.PutState(B, []byte(strconv.Itoa(Bval)))
    68  	if err != nil {
    69  		return shim.Error(err.Error())
    70  	}
    71  
    72  	return shim.Success([]byte("OK"))
    73  }
    74  
    75  // Invoke transaction makes payment of X units from A to B
    76  func (t *SimpleChaincode) Invoke(stub shim.ChaincodeStubInterface) pb.Response {
    77  	_, args := stub.GetFunctionAndParameters()
    78  
    79  	var A, B string    // Entities
    80  	var Aval, Bval int // Asset holdings
    81  	var X int          // Transaction value
    82  	var err error
    83  
    84  	if len(args) != 3 {
    85  		return shim.Error("Incorrect number of arguments. Expecting 3")
    86  	}
    87  
    88  	A = args[0]
    89  	B = args[1]
    90  
    91  	// Get the state from the ledger
    92  	// TODO: will be nice to have a GetAllState call to ledger
    93  	Avalbytes, err := stub.GetState(A)
    94  	if err != nil {
    95  		return shim.Error("Failed to get state")
    96  	}
    97  	if Avalbytes == nil {
    98  		return shim.Error("Entity not found")
    99  	}
   100  	Aval, _ = strconv.Atoi(string(Avalbytes))
   101  
   102  	Bvalbytes, err := stub.GetState(B)
   103  	if err != nil {
   104  		return shim.Error("Failed to get state")
   105  	}
   106  	if Bvalbytes == nil {
   107  		return shim.Error("Entity not found")
   108  	}
   109  	Bval, _ = strconv.Atoi(string(Bvalbytes))
   110  
   111  	// Perform the execution
   112  	X, err = strconv.Atoi(args[2])
   113  	if err != nil {
   114  		return shim.Error("Invalid transaction amount, expecting a integer value")
   115  	}
   116  	Aval = Aval - X
   117  	Bval = Bval + X
   118  	fmt.Printf("Aval = %d, Bval = %d\n", Aval, Bval)
   119  
   120  	// Write the state back to the ledger
   121  	err = stub.PutState(A, []byte(strconv.Itoa(Aval)))
   122  	if err != nil {
   123  		return shim.Error(err.Error())
   124  	}
   125  
   126  	err = stub.PutState(B, []byte(strconv.Itoa(Bval)))
   127  	if err != nil {
   128  		return shim.Error(err.Error())
   129  	}
   130  
   131  	return shim.Success([]byte(fmt.Sprintf("{%d,%d}", Aval, Bval)))
   132  }
   133  
   134  func main() {
   135  	err := shim.Start(new(SimpleChaincode))
   136  	if err != nil {
   137  		fmt.Printf("Error starting Simple chaincode: %s", err)
   138  	}
   139  }