implemented smart contract utility function FromAddress (#88)

* implemented smart contract utility function FromAddress

* bumped version

VERSION

@@ -1 +1 @@
-0.44.5
+0.44.6

examples/token-sale/token_sale.go

@@ -3,6 +3,7 @@ package tokensale
 import (
 	"github.com/CityOfZion/neo-go/pkg/vm/api/runtime"
 	"github.com/CityOfZion/neo-go/pkg/vm/api/storage"
+	"github.com/CityOfZion/neo-go/pkg/vm/api/util"
 )
 
 const (
@@ -10,7 +11,7 @@ const (
 	multiplier = decimals * 10
 )
 
-var owner = []byte{0xaf, 0x12, 0xa8, 0x68, 0x7b, 0x14, 0x94, 0x8b, 0xc4, 0xa0, 0x08, 0x12, 0x8a, 0x55, 0x0a, 0x63, 0x69, 0x5b, 0xc1, 0xa5}
+var owner = util.FromAddress("AJX1jGfj3qPBbpAKjY527nPbnrnvSx9nCg")
 
 // TokenConfig holds information about the token we want to use for the sale.
 type TokenConfig struct {

pkg/vm/api/util/util.go

@@ -0,0 +1,6 @@
+package util
+
+// FromAddress returns the underlying bytes from the given address string.
+func FromAddress(address string) []byte {
+	return nil
+}

pkg/vm/compiler/README.md

@@ -32,6 +32,9 @@ The neo-go compiler compiles Go programs to bytecode that the NEO virtual machin
 - Hash256
 - Hash160
 
+### Custom utility functions
+- `FromAddress(address string) []byte`
+
 ## Not yet implemented
 - range
 - some parts of the interop layer (VM API)
@@ -109,9 +112,12 @@ Will output something like:
 ```Golang
 package mycontract
 
-import "github.com/CityOfZion/neo-go/pkg/vm/api/runtime"
+import (
+    "github.com/CityOfZion/neo-go/pkg/vm/api/runtime"
+    "github.com/CityOfZion/neo-go/pkg/vm/api/util"
+)
 
-var owner = []byte{0xaf, 0x12, 0xa8, 0x68, 0x7b, 0x14, 0x94, 0x8b, 0xc4, 0xa0, 0x08, 0x12, 0x8a, 0x55, 0x0a, 0x63, 0x69, 0x5b, 0xc1, 0xa5}
+var owner = util.FromAddress("AJX1jGfj3qPBbpAKjY527nPbnrnvSx9nCg") 
 
 func Main() bool {
     isOwner := runtime.CheckWitness(owner)
@@ -135,7 +141,7 @@ import (
 	"github.com/CityOfZion/neo-go/pkg/vm/api/storage"
 )
 
-var owner = []byte{0xaf, 0x12, 0xa8, 0x68, 0x7b, 0x14, 0x94, 0x8b, 0xc4, 0xa0, 0x08, 0x12, 0x8a, 0x55, 0x0a, 0x63, 0x69, 0x5b, 0xc1, 0xa5}
+var owner = util.FromAddress("AJX1jGfj3qPBbpAKjY527nPbnrnvSx9nCg") 
 
 type Token struct {
 	Name        string

pkg/vm/compiler/analysis.go

@@ -14,7 +14,7 @@ var (
 	// Go language builtin functions and custom builtin utility functions.
 	builtinFuncs = []string{
 		"len", "append", "SHA256",
-		"SHA1", "Hash256", "Hash160",
+		"SHA1", "Hash256", "Hash160", "FromAddress",
 	}
 
 	// VM system calls that have no return value.

pkg/vm/compiler/codegen.go

@@ -8,10 +8,13 @@ import (
 	"go/token"
 	"go/types"
 	"log"
+	"strings"
 
+	"github.com/CityOfZion/neo-go/pkg/crypto"
 	"github.com/CityOfZion/neo-go/pkg/vm"
 )
 
+// The identifier of the entry function. Default set to Main.
 const mainIdent = "Main"
 
 type codegen struct {
@@ -188,7 +191,7 @@ func (c *codegen) convertFuncDecl(file *ast.File, decl *ast.FuncDecl) {
 
 	ast.Walk(c, decl.Body)
 
-	// If this function returs the void (no return stmt) we will cleanup its junk on the stack.
+	// If this function returns the void (no return stmt) we will cleanup its junk on the stack.
 	if !hasReturnStmt(decl) {
 		emitOpcode(c.prog, vm.Ofromaltstack)
 		emitOpcode(c.prog, vm.Odrop)
@@ -564,6 +567,18 @@ func (c *codegen) convertBuiltin(expr *ast.CallExpr) {
 		emitOpcode(c.prog, vm.Ohash256)
 	case "Hash160":
 		emitOpcode(c.prog, vm.Ohash160)
+	case "FromAddress":
+		// We can be sure that this is a ast.BasicLit just containing a simple
+		// address string. Note that the string returned from callin Value will
+		// contain double qoutes that need to be stripped.
+		addressStr := expr.Args[0].(*ast.BasicLit).Value
+		addressStr = strings.Replace(addressStr, "\"", "", 2)
+		uint160, err := crypto.Uint160DecodeAddress(addressStr)
+		if err != nil {
+			log.Fatal(err)
+		}
+		bytes := uint160.Bytes()
+		emitBytes(c.prog, bytes)
 	}
 }