Merge pull request #2435 from obscuren/abi-array-fixes

accounts/abi: refactored ABI package

8 files changed, 733 insertions, 362 deletions

diff --git a/accounts/abi/abi.go b/accounts/abi/abi.go
index 9ef7c0f0d..32df6f19d 100644
--- a/accounts/abi/abi.go
+++ b/accounts/abi/abi.go
@@ -48,42 +48,6 @@ func JSON(reader io.Reader) (ABI, error) {
 	return abi, nil
 }
 
-// tests, tests whether the given input would result in a successful
-// call. Checks argument list count and matches input to `input`.
-func (abi ABI) pack(method Method, args ...interface{}) ([]byte, error) {
-	// variable input is the output appended at the end of packed
-	// output. This is used for strings and bytes types input.
-	var variableInput []byte
-
-	var ret []byte
-	for i, a := range args {
-		input := method.Inputs[i]
-		// pack the input
-		packed, err := input.Type.pack(a)
-		if err != nil {
-			return nil, fmt.Errorf("`%s` %v", method.Name, err)
-		}
-
-		// check for a slice type (string, bytes, slice)
-		if input.Type.T == StringTy || input.Type.T == BytesTy || input.Type.IsSlice {
-			// calculate the offset
-			offset := len(method.Inputs)*32 + len(variableInput)
-			// set the offset
-			ret = append(ret, packNum(reflect.ValueOf(offset), UintTy)...)
-			// Append the packed output to the variable input. The variable input
-			// will be appended at the end of the input.
-			variableInput = append(variableInput, packed...)
-		} else {
-			// append the packed value to the input
-			ret = append(ret, packed...)
-		}
-	}
-	// append the variable input at the end of the packed input
-	ret = append(ret, variableInput...)
-
-	return ret, nil
-}
-
 // Pack the given method name to conform the ABI. Method call's data
 // will consist of method_id, args0, arg1, ... argN. Method id consists
 // of 4 bytes and arguments are all 32 bytes.
@@ -102,11 +66,7 @@ func (abi ABI) Pack(name string, args ...interface{}) ([]byte, error) {
 		}
 		method = m
 	}
-	// Make sure arguments match up and pack them
-	if len(args) != len(method.Inputs) {
-		return nil, fmt.Errorf("argument count mismatch: %d for %d", len(args), len(method.Inputs))
-	}
-	arguments, err := abi.pack(method, args...)
+	arguments, err := method.pack(method, args...)
 	if err != nil {
 		return nil, err
 	}
@@ -126,18 +86,21 @@ func toGoSlice(i int, t Argument, output []byte) (interface{}, error) {
 	if index+32 > len(output) {
 		return nil, fmt.Errorf("abi: cannot marshal in to go slice: insufficient size output %d require %d", len(output), index+32)
 	}
+	elem := t.Type.Elem
 
 	// first we need to create a slice of the type
 	var refSlice reflect.Value
-	switch t.Type.T {
+	switch elem.T {
 	case IntTy, UintTy, BoolTy: // int, uint, bool can all be of type big int.
 		refSlice = reflect.ValueOf([]*big.Int(nil))
 	case AddressTy: // address must be of slice Address
 		refSlice = reflect.ValueOf([]common.Address(nil))
 	case HashTy: // hash must be of slice hash
 		refSlice = reflect.ValueOf([]common.Hash(nil))
+	case FixedBytesTy:
+		refSlice = reflect.ValueOf([]byte(nil))
 	default: // no other types are supported
-		return nil, fmt.Errorf("abi: unsupported slice type %v", t.Type.T)
+		return nil, fmt.Errorf("abi: unsupported slice type %v", elem.T)
 	}
 	// get the offset which determines the start of this array ...
 	offset := int(common.BytesToBig(output[index : index+32]).Uint64())
@@ -164,7 +127,7 @@ func toGoSlice(i int, t Argument, output []byte) (interface{}, error) {
 		)
 
 		// set inter to the correct type (cast)
-		switch t.Type.T {
+		switch elem.T {
 		case IntTy, UintTy:
 			inter = common.BytesToBig(returnOutput)
 		case BoolTy:
@@ -186,7 +149,7 @@ func toGoSlice(i int, t Argument, output []byte) (interface{}, error) {
 // argument in T.
 func toGoType(i int, t Argument, output []byte) (interface{}, error) {
 	// we need to treat slices differently
-	if t.Type.IsSlice {
+	if (t.Type.IsSlice || t.Type.IsArray) && t.Type.T != BytesTy && t.Type.T != StringTy && t.Type.T != FixedBytesTy {
 		return toGoSlice(i, t, output)
 	}
 
@@ -217,12 +180,33 @@ func toGoType(i int, t Argument, output []byte) (interface{}, error) {
 		returnOutput = output[index : index+32]
 	}
 
-	// cast bytes to abi return type
+	// convert the bytes to whatever is specified by the ABI.
 	switch t.Type.T {
-	case IntTy:
-		return common.BytesToBig(returnOutput), nil
-	case UintTy:
-		return common.BytesToBig(returnOutput), nil
+	case IntTy, UintTy:
+		bigNum := common.BytesToBig(returnOutput)
+
+		// If the type is a integer convert to the integer type
+		// specified by the ABI.
+		switch t.Type.Kind {
+		case reflect.Uint8:
+			return uint8(bigNum.Uint64()), nil
+		case reflect.Uint16:
+			return uint16(bigNum.Uint64()), nil
+		case reflect.Uint32:
+			return uint32(bigNum.Uint64()), nil
+		case reflect.Uint64:
+			return uint64(bigNum.Uint64()), nil
+		case reflect.Int8:
+			return int8(bigNum.Int64()), nil
+		case reflect.Int16:
+			return int16(bigNum.Int64()), nil
+		case reflect.Int32:
+			return int32(bigNum.Int64()), nil
+		case reflect.Int64:
+			return int64(bigNum.Int64()), nil
+		case reflect.Ptr:
+			return bigNum, nil
+		}
 	case BoolTy:
 		return common.BytesToBig(returnOutput).Uint64() > 0, nil
 	case AddressTy:
@@ -328,10 +312,12 @@ func set(dst, src reflect.Value, output Argument) error {
 			return fmt.Errorf("abi: cannot unmarshal %v in to array of elem %v", src.Type(), dstType.Elem())
 		}
 
-		if dst.Len() < output.Type.Size {
-			return fmt.Errorf("abi: cannot unmarshal src (len=%d) in to dst (len=%d)", output.Type.Size, dst.Len())
+		if dst.Len() < output.Type.SliceSize {
+			return fmt.Errorf("abi: cannot unmarshal src (len=%d) in to dst (len=%d)", output.Type.SliceSize, dst.Len())
 		}
 		reflect.Copy(dst, src)
+	case dstType.Kind() == reflect.Interface:
+		dst.Set(src)
 	default:
 		return fmt.Errorf("abi: cannot unmarshal %v in to %v", src.Type(), dst.Type())
 	}
diff --git a/accounts/abi/abi_test.go b/accounts/abi/abi_test.go
index a1b3e62d9..05535b3b5 100644
--- a/accounts/abi/abi_test.go
+++ b/accounts/abi/abi_test.go
@@ -29,66 +29,391 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 )
 
-const jsondata = `
-[
-	{ "type" : "function", "name" : "balance", "const" : true },
-	{ "type" : "function", "name" : "send", "const" : false, "inputs" : [ { "name" : "amount", "type" : "uint256" } ] }
-]`
+// formatSilceOutput add padding to the value and adds a size
+func formatSliceOutput(v ...[]byte) []byte {
+	off := common.LeftPadBytes(big.NewInt(int64(len(v))).Bytes(), 32)
+	output := append(off, make([]byte, 0, len(v)*32)...)
 
-const jsondata2 = `
-[
-	{ "type" : "function", "name" : "balance", "const" : true },
-	{ "type" : "function", "name" : "send", "const" : false, "inputs" : [ { "name" : "amount", "type" : "uint256" } ] },
-	{ "type" : "function", "name" : "test", "const" : false, "inputs" : [ { "name" : "number", "type" : "uint32" } ] },
-	{ "type" : "function", "name" : "string", "const" : false, "inputs" : [ { "name" : "inputs", "type" : "string" } ] },
-	{ "type" : "function", "name" : "bool", "const" : false, "inputs" : [ { "name" : "inputs", "type" : "bool" } ] },
-	{ "type" : "function", "name" : "address", "const" : false, "inputs" : [ { "name" : "inputs", "type" : "address" } ] },
-	{ "type" : "function", "name" : "string32", "const" : false, "inputs" : [ { "name" : "inputs", "type" : "string32" } ] },
-	{ "type" : "function", "name" : "uint64[2]", "const" : false, "inputs" : [ { "name" : "inputs", "type" : "uint64[2]" } ] },
-	{ "type" : "function", "name" : "uint64[]", "const" : false, "inputs" : [ { "name" : "inputs", "type" : "uint64[]" } ] },
-	{ "type" : "function", "name" : "foo", "const" : false, "inputs" : [ { "name" : "inputs", "type" : "uint32" } ] },
-	{ "type" : "function", "name" : "bar", "const" : false, "inputs" : [ { "name" : "inputs", "type" : "uint32" }, { "name" : "string", "type" : "uint16" } ] },
-	{ "type" : "function", "name" : "slice", "const" : false, "inputs" : [ { "name" : "inputs", "type" : "uint32[2]" } ] },
-	{ "type" : "function", "name" : "slice256", "const" : false, "inputs" : [ { "name" : "inputs", "type" : "uint256[2]" } ] },
-	{ "type" : "function", "name" : "sliceAddress", "const" : false, "inputs" : [ { "name" : "inputs", "type" : "address[]" } ] },
-	{ "type" : "function", "name" : "sliceMultiAddress", "const" : false, "inputs" : [ { "name" : "a", "type" : "address[]" }, { "name" : "b", "type" : "address[]" } ] }
-]`
+	for _, value := range v {
+		output = append(output, common.LeftPadBytes(value, 32)...)
+	}
+	return output
+}
 
-func TestType(t *testing.T) {
-	typ, err := NewType("uint32")
-	if err != nil {
-		t.Error(err)
+// quick helper padding
+func pad(input []byte, size int, left bool) []byte {
+	if left {
+		return common.LeftPadBytes(input, size)
 	}
-	if typ.Kind != reflect.Uint {
-		t.Error("expected uint32 to have kind Ptr")
+	return common.RightPadBytes(input, size)
+}
+
+func TestTypeCheck(t *testing.T) {
+	for i, test := range []struct {
+		typ   string
+		input interface{}
+		err   string
+	}{
+		{"uint", big.NewInt(1), ""},
+		{"int", big.NewInt(1), ""},
+		{"uint30", big.NewInt(1), ""},
+		{"uint30", uint8(1), "abi: cannot use uint8 as type ptr as argument"},
+		{"uint16", uint16(1), ""},
+		{"uint16", uint8(1), "abi: cannot use uint8 as type uint16 as argument"},
+		{"uint16[]", []uint16{1, 2, 3}, ""},
+		{"uint16[]", [3]uint16{1, 2, 3}, ""},
+		{"uint16[]", []uint32{1, 2, 3}, "abi: cannot use []uint32 as type []uint16 as argument"},
+		{"uint16[3]", [3]uint32{1, 2, 3}, "abi: cannot use [3]uint32 as type [3]uint16 as argument"},
+		{"uint16[3]", [4]uint16{1, 2, 3}, "abi: cannot use [4]uint16 as type [3]uint16 as argument"},
+		{"uint16[3]", []uint16{1, 2, 3}, ""},
+		{"uint16[3]", []uint16{1, 2, 3, 4}, "abi: cannot use [4]uint16 as type [3]uint16 as argument"},
+		{"address[]", []common.Address{common.Address{1}}, ""},
+		{"address[1]", []common.Address{common.Address{1}}, ""},
+		{"address[1]", [1]common.Address{common.Address{1}}, ""},
+		{"address[2]", [1]common.Address{common.Address{1}}, "abi: cannot use [1]array as type [2]array as argument"},
+		{"bytes32", [32]byte{}, ""},
+		{"bytes32", [33]byte{}, "abi: cannot use [33]uint8 as type [32]uint8 as argument"},
+		{"bytes32", common.Hash{1}, ""},
+		{"bytes31", [31]byte{}, ""},
+		{"bytes31", [32]byte{}, "abi: cannot use [32]uint8 as type [31]uint8 as argument"},
+		{"bytes", []byte{0, 1}, ""},
+		{"bytes", [2]byte{0, 1}, ""},
+		{"bytes", common.Hash{1}, ""},
+		{"string", "hello world", ""},
+		{"bytes32[]", [][32]byte{[32]byte{}}, ""},
+	} {
+		typ, err := NewType(test.typ)
+		if err != nil {
+			t.Fatal("unexpected parse error:", err)
+		}
+
+		err = typeCheck(typ, reflect.ValueOf(test.input))
+		if err != nil && len(test.err) == 0 {
+			t.Errorf("%d failed. Expected no err but got: %v", i, err)
+			continue
+		}
+		if err == nil && len(test.err) != 0 {
+			t.Errorf("%d failed. Expected err: %v but got none", i, test.err)
+			continue
+		}
+
+		if err != nil && len(test.err) != 0 && err.Error() != test.err {
+			t.Errorf("%d failed. Expected err: '%v' got err: '%v'", i, test.err, err)
+		}
 	}
+}
 
-	typ, err = NewType("uint32[]")
+func TestSimpleMethodUnpack(t *testing.T) {
+	for i, test := range []struct {
+		def              string      // definition of the **output** ABI params
+		marshalledOutput []byte      // evm return data
+		expectedOut      interface{} // the expected output
+		outVar           string      // the output variable (e.g. uint32, *big.Int, etc)
+		err              string      // empty or error if expected
+	}{
+		{
+			`[ { "type": "uint32" } ]`,
+			pad([]byte{1}, 32, true),
+			uint32(1),
+			"uint32",
+			"",
+		},
+		{
+			`[ { "type": "uint32" } ]`,
+			pad([]byte{1}, 32, true),
+			nil,
+			"uint16",
+			"abi: cannot unmarshal uint32 in to uint16",
+		},
+		{
+			`[ { "type": "uint17" } ]`,
+			pad([]byte{1}, 32, true),
+			nil,
+			"uint16",
+			"abi: cannot unmarshal *big.Int in to uint16",
+		},
+		{
+			`[ { "type": "uint17" } ]`,
+			pad([]byte{1}, 32, true),
+			big.NewInt(1),
+			"*big.Int",
+			"",
+		},
+
+		{
+			`[ { "type": "int32" } ]`,
+			pad([]byte{1}, 32, true),
+			int32(1),
+			"int32",
+			"",
+		},
+		{
+			`[ { "type": "int32" } ]`,
+			pad([]byte{1}, 32, true),
+			nil,
+			"int16",
+			"abi: cannot unmarshal int32 in to int16",
+		},
+		{
+			`[ { "type": "int17" } ]`,
+			pad([]byte{1}, 32, true),
+			nil,
+			"int16",
+			"abi: cannot unmarshal *big.Int in to int16",
+		},
+		{
+			`[ { "type": "int17" } ]`,
+			pad([]byte{1}, 32, true),
+			big.NewInt(1),
+			"*big.Int",
+			"",
+		},
+
+		{
+			`[ { "type": "address" } ]`,
+			pad(pad([]byte{1}, 20, false), 32, true),
+			common.Address{1},
+			"address",
+			"",
+		},
+		{
+			`[ { "type": "bytes32" } ]`,
+			pad([]byte{1}, 32, false),
+			pad([]byte{1}, 32, false),
+			"bytes",
+			"",
+		},
+		{
+			`[ { "type": "bytes32" } ]`,
+			pad([]byte{1}, 32, false),
+			pad([]byte{1}, 32, false),
+			"hash",
+			"",
+		},
+		{
+			`[ { "type": "bytes32" } ]`,
+			pad([]byte{1}, 32, false),
+			pad([]byte{1}, 32, false),
+			"interface",
+			"",
+		},
+	} {
+		abiDefinition := fmt.Sprintf(`[{ "name" : "method", "outputs": %s}]`, test.def)
+		abi, err := JSON(strings.NewReader(abiDefinition))
+		if err != nil {
+			t.Errorf("%d failed. %v", i, err)
+			continue
+		}
+
+		var outvar interface{}
+		switch test.outVar {
+		case "uint8":
+			var v uint8
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "uint16":
+			var v uint16
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "uint32":
+			var v uint32
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "uint64":
+			var v uint64
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "int8":
+			var v int8
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "int16":
+			var v int16
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "int32":
+			var v int32
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "int64":
+			var v int64
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "*big.Int":
+			var v *big.Int
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "address":
+			var v common.Address
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "bytes":
+			var v []byte
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "hash":
+			var v common.Hash
+			err = abi.Unpack(&v, "method", test.marshalledOutput)
+			outvar = v
+		case "interface":
+			err = abi.Unpack(&outvar, "method", test.marshalledOutput)
+		default:
+			t.Errorf("unsupported type '%v' please add it to the switch statement in this test", test.outVar)
+			continue
+		}
+
+		if err != nil && len(test.err) == 0 {
+			t.Errorf("%d failed. Expected no err but got: %v", i, err)
+			continue
+		}
+		if err == nil && len(test.err) != 0 {
+			t.Errorf("%d failed. Expected err: %v but got none", i, test.err)
+			continue
+		}
+		if err != nil && len(test.err) != 0 && err.Error() != test.err {
+			t.Errorf("%d failed. Expected err: '%v' got err: '%v'", i, test.err, err)
+			continue
+		}
+
+		if err == nil {
+			// bit of an ugly hack for hash type but I don't feel like finding a proper solution
+			if test.outVar == "hash" {
+				tmp := outvar.(common.Hash) // without assignment it's unaddressable
+				outvar = tmp[:]
+			}
+
+			if !reflect.DeepEqual(test.expectedOut, outvar) {
+				t.Errorf("%d failed. Output error: expected %v, got %v", i, test.expectedOut, outvar)
+			}
+		}
+	}
+}
+
+func TestPack(t *testing.T) {
+	for i, test := range []struct {
+		typ string
+
+		input  interface{}
+		output []byte
+	}{
+		{"uint16", uint16(2), pad([]byte{2}, 32, true)},
+		{"uint16[]", []uint16{1, 2}, formatSliceOutput([]byte{1}, []byte{2})},
+		{"bytes20", [20]byte{1}, pad([]byte{1}, 32, false)},
+		{"uint256[]", []*big.Int{big.NewInt(1), big.NewInt(2)}, formatSliceOutput([]byte{1}, []byte{2})},
+		{"address[]", []common.Address{common.Address{1}, common.Address{2}}, formatSliceOutput(pad([]byte{1}, 20, false), pad([]byte{2}, 20, false))},
+		{"bytes32[]", []common.Hash{common.Hash{1}, common.Hash{2}}, formatSliceOutput(pad([]byte{1}, 32, false), pad([]byte{2}, 32, false))},
+	} {
+		typ, err := NewType(test.typ)
+		if err != nil {
+			t.Fatal("unexpected parse error:", err)
+		}
+
+		output, err := typ.pack(reflect.ValueOf(test.input))
+		if err != nil {
+			t.Fatal("unexpected pack error:", err)
+		}
+
+		if !bytes.Equal(output, test.output) {
+			t.Errorf("%d failed. Expected bytes: '%x' Got: '%x'", i, test.output, output)
+		}
+	}
+}
+
+func TestMethodPack(t *testing.T) {
+	abi, err := JSON(strings.NewReader(jsondata2))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	sig := abi.Methods["slice"].Id()
+	sig = append(sig, common.LeftPadBytes([]byte{32}, 32)...)
+	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
+	sig = append(sig, common.LeftPadBytes([]byte{1}, 32)...)
+	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
+
+	packed, err := abi.Pack("slice", []uint32{1, 2})
 	if err != nil {
 		t.Error(err)
 	}
-	if !typ.IsSlice {
-		t.Error("expected uint32[] to be slice")
+
+	if !bytes.Equal(packed, sig) {
+		t.Errorf("expected %x got %x", sig, packed)
 	}
-	if typ.Type != ubig_t {
-		t.Error("expcted uith32[] to have type uint64")
+
+	var addrA, addrB = common.Address{1}, common.Address{2}
+	sig = abi.Methods["sliceAddress"].Id()
+	sig = append(sig, common.LeftPadBytes([]byte{32}, 32)...)
+	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
+	sig = append(sig, common.LeftPadBytes(addrA[:], 32)...)
+	sig = append(sig, common.LeftPadBytes(addrB[:], 32)...)
+
+	packed, err = abi.Pack("sliceAddress", []common.Address{addrA, addrB})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(packed, sig) {
+		t.Errorf("expected %x got %x", sig, packed)
 	}
 
-	typ, err = NewType("uint32[2]")
+	var addrC, addrD = common.Address{3}, common.Address{4}
+	sig = abi.Methods["sliceMultiAddress"].Id()
+	sig = append(sig, common.LeftPadBytes([]byte{64}, 32)...)
+	sig = append(sig, common.LeftPadBytes([]byte{160}, 32)...)
+	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
+	sig = append(sig, common.LeftPadBytes(addrA[:], 32)...)
+	sig = append(sig, common.LeftPadBytes(addrB[:], 32)...)
+	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
+	sig = append(sig, common.LeftPadBytes(addrC[:], 32)...)
+	sig = append(sig, common.LeftPadBytes(addrD[:], 32)...)
+
+	packed, err = abi.Pack("sliceMultiAddress", []common.Address{addrA, addrB}, []common.Address{addrC, addrD})
 	if err != nil {
-		t.Error(err)
+		t.Fatal(err)
 	}
-	if !typ.IsSlice {
-		t.Error("expected uint32[2] to be slice")
+	if !bytes.Equal(packed, sig) {
+		t.Errorf("expected %x got %x", sig, packed)
 	}
-	if typ.Type != ubig_t {
-		t.Error("expcted uith32[2] to have type uint64")
+
+	sig = abi.Methods["slice256"].Id()
+	sig = append(sig, common.LeftPadBytes([]byte{32}, 32)...)
+	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
+	sig = append(sig, common.LeftPadBytes([]byte{1}, 32)...)
+	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
+
+	packed, err = abi.Pack("slice256", []*big.Int{big.NewInt(1), big.NewInt(2)})
+	if err != nil {
+		t.Error(err)
 	}
-	if typ.SliceSize != 2 {
-		t.Error("expected uint32[2] to have a size of 2")
+
+	if !bytes.Equal(packed, sig) {
+		t.Errorf("expected %x got %x", sig, packed)
 	}
 }
 
+const jsondata = `
+[
+	{ "type" : "function", "name" : "balance", "constant" : true },
+	{ "type" : "function", "name" : "send", "constant" : false, "inputs" : [ { "name" : "amount", "type" : "uint256" } ] }
+]`
+
+const jsondata2 = `
+[
+	{ "type" : "function", "name" : "balance", "constant" : true },
+	{ "type" : "function", "name" : "send", "constant" : false, "inputs" : [ { "name" : "amount", "type" : "uint256" } ] },
+	{ "type" : "function", "name" : "test", "constant" : false, "inputs" : [ { "name" : "number", "type" : "uint32" } ] },
+	{ "type" : "function", "name" : "string", "constant" : false, "inputs" : [ { "name" : "inputs", "type" : "string" } ] },
+	{ "type" : "function", "name" : "bool", "constant" : false, "inputs" : [ { "name" : "inputs", "type" : "bool" } ] },
+	{ "type" : "function", "name" : "address", "constant" : false, "inputs" : [ { "name" : "inputs", "type" : "address" } ] },
+	{ "type" : "function", "name" : "uint64[2]", "constant" : false, "inputs" : [ { "name" : "inputs", "type" : "uint64[2]" } ] },
+	{ "type" : "function", "name" : "uint64[]", "constant" : false, "inputs" : [ { "name" : "inputs", "type" : "uint64[]" } ] },
+	{ "type" : "function", "name" : "foo", "constant" : false, "inputs" : [ { "name" : "inputs", "type" : "uint32" } ] },
+	{ "type" : "function", "name" : "bar", "constant" : false, "inputs" : [ { "name" : "inputs", "type" : "uint32" }, { "name" : "string", "type" : "uint16" } ] },
+	{ "type" : "function", "name" : "slice", "constant" : false, "inputs" : [ { "name" : "inputs", "type" : "uint32[2]" } ] },
+	{ "type" : "function", "name" : "slice256", "constant" : false, "inputs" : [ { "name" : "inputs", "type" : "uint256[2]" } ] },
+	{ "type" : "function", "name" : "sliceAddress", "constant" : false, "inputs" : [ { "name" : "inputs", "type" : "address[]" } ] },
+	{ "type" : "function", "name" : "sliceMultiAddress", "constant" : false, "inputs" : [ { "name" : "a", "type" : "address[]" }, { "name" : "b", "type" : "address[]" } ] }
+]`
+
 func TestReader(t *testing.T) {
 	Uint256, _ := NewType("uint256")
 	exp := ABI{
@@ -164,21 +489,6 @@ func TestTestString(t *testing.T) {
 	if _, err := abi.Pack("string", "hello world"); err != nil {
 		t.Error(err)
 	}
-
-	str10 := string(make([]byte, 10))
-	if _, err := abi.Pack("string32", str10); err != nil {
-		t.Error(err)
-	}
-
-	str32 := string(make([]byte, 32))
-	if _, err := abi.Pack("string32", str32); err != nil {
-		t.Error(err)
-	}
-
-	str33 := string(make([]byte, 33))
-	if _, err := abi.Pack("string32", str33); err == nil {
-		t.Error("expected str33 to throw out of bound error")
-	}
 }
 
 func TestTestBool(t *testing.T) {
@@ -210,26 +520,10 @@ func TestTestSlice(t *testing.T) {
 	}
 }
 
-func TestImplicitTypeCasts(t *testing.T) {
-	abi, err := JSON(strings.NewReader(jsondata2))
-	if err != nil {
-		t.Error(err)
-		t.FailNow()
-	}
-
-	slice := make([]uint8, 2)
-	_, err = abi.Pack("uint64[2]", slice)
-	expStr := "`uint64[2]` abi: cannot use type uint8 as type uint64"
-	if err.Error() != expStr {
-		t.Errorf("expected %v, got %v", expStr, err)
-	}
-}
-
 func TestMethodSignature(t *testing.T) {
 	String, _ := NewType("string")
-	String32, _ := NewType("string32")
-	m := Method{"foo", false, []Argument{Argument{"bar", String32, false}, Argument{"baz", String, false}}, nil}
-	exp := "foo(string32,string)"
+	m := Method{"foo", false, []Argument{Argument{"bar", String, false}, Argument{"baz", String, false}}, nil}
+	exp := "foo(string,string)"
 	if m.Sig() != exp {
 		t.Error("signature mismatch", exp, "!=", m.Sig())
 	}
@@ -247,28 +541,6 @@ func TestMethodSignature(t *testing.T) {
 	}
 }
 
-func TestPack(t *testing.T) {
-	abi, err := JSON(strings.NewReader(jsondata2))
-	if err != nil {
-		t.Error(err)
-		t.FailNow()
-	}
-
-	sig := crypto.Keccak256([]byte("foo(uint32)"))[:4]
-	sig = append(sig, make([]byte, 32)...)
-	sig[35] = 10
-
-	packed, err := abi.Pack("foo", uint32(10))
-	if err != nil {
-		t.Error(err)
-		t.FailNow()
-	}
-
-	if !bytes.Equal(packed, sig) {
-		t.Errorf("expected %x got %x", sig, packed)
-	}
-}
-
 func TestMultiPack(t *testing.T) {
 	abi, err := JSON(strings.NewReader(jsondata2))
 	if err != nil {
@@ -292,77 +564,6 @@ func TestMultiPack(t *testing.T) {
 	}
 }
 
-func TestPackSlice(t *testing.T) {
-	abi, err := JSON(strings.NewReader(jsondata2))
-	if err != nil {
-		t.Error(err)
-		t.FailNow()
-	}
-
-	sig := crypto.Keccak256([]byte("slice(uint32[2])"))[:4]
-	sig = append(sig, common.LeftPadBytes([]byte{32}, 32)...)
-	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
-	sig = append(sig, common.LeftPadBytes([]byte{1}, 32)...)
-	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
-
-	packed, err := abi.Pack("slice", []uint32{1, 2})
-	if err != nil {
-		t.Error(err)
-	}
-
-	if !bytes.Equal(packed, sig) {
-		t.Errorf("expected %x got %x", sig, packed)
-	}
-
-	var addrA, addrB = common.Address{1}, common.Address{2}
-	sig = abi.Methods["sliceAddress"].Id()
-	sig = append(sig, common.LeftPadBytes([]byte{32}, 32)...)
-	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
-	sig = append(sig, common.LeftPadBytes(addrA[:], 32)...)
-	sig = append(sig, common.LeftPadBytes(addrB[:], 32)...)
-
-	packed, err = abi.Pack("sliceAddress", []common.Address{addrA, addrB})
-	if err != nil {
-		t.Fatal(err)
-	}
-	if !bytes.Equal(packed, sig) {
-		t.Errorf("expected %x got %x", sig, packed)
-	}
-
-	var addrC, addrD = common.Address{3}, common.Address{4}
-	sig = abi.Methods["sliceMultiAddress"].Id()
-	sig = append(sig, common.LeftPadBytes([]byte{64}, 32)...)
-	sig = append(sig, common.LeftPadBytes([]byte{160}, 32)...)
-	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
-	sig = append(sig, common.LeftPadBytes(addrA[:], 32)...)
-	sig = append(sig, common.LeftPadBytes(addrB[:], 32)...)
-	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
-	sig = append(sig, common.LeftPadBytes(addrC[:], 32)...)
-	sig = append(sig, common.LeftPadBytes(addrD[:], 32)...)
-
-	packed, err = abi.Pack("sliceMultiAddress", []common.Address{addrA, addrB}, []common.Address{addrC, addrD})
-	if err != nil {
-		t.Fatal(err)
-	}
-	if !bytes.Equal(packed, sig) {
-		t.Errorf("expected %x got %x", sig, packed)
-	}
-
-	sig = crypto.Keccak256([]byte("slice256(uint256[2])"))[:4]
-	sig = append(sig, common.LeftPadBytes([]byte{32}, 32)...)
-	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
-	sig = append(sig, common.LeftPadBytes([]byte{1}, 32)...)
-	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
-
-	packed, err = abi.Pack("slice256", []*big.Int{big.NewInt(1), big.NewInt(2)})
-	if err != nil {
-		t.Error(err)
-	}
-
-	if !bytes.Equal(packed, sig) {
-		t.Errorf("expected %x got %x", sig, packed)
-	}
-}
 func ExampleJSON() {
 	const definition = `[{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"isBar","outputs":[{"name":"","type":"bool"}],"type":"function"}]`
 
@@ -382,9 +583,9 @@ func ExampleJSON() {
 
 func TestInputVariableInputLength(t *testing.T) {
 	const definition = `[
-	{ "type" : "function", "name" : "strOne", "const" : true, "inputs" : [ { "name" : "str", "type" : "string" } ] },
-	{ "type" : "function", "name" : "bytesOne", "const" : true, "inputs" : [ { "name" : "str", "type" : "bytes" } ] },
-	{ "type" : "function", "name" : "strTwo", "const" : true, "inputs" : [ { "name" : "str", "type" : "string" }, { "name" : "str1", "type" : "string" } ] }
+	{ "type" : "function", "name" : "strOne", "constant" : true, "inputs" : [ { "name" : "str", "type" : "string" } ] },
+	{ "type" : "function", "name" : "bytesOne", "constant" : true, "inputs" : [ { "name" : "str", "type" : "bytes" } ] },
+	{ "type" : "function", "name" : "strTwo", "constant" : true, "inputs" : [ { "name" : "str", "type" : "string" }, { "name" : "str1", "type" : "string" } ] }
 	]`
 
 	abi, err := JSON(strings.NewReader(definition))
@@ -546,7 +747,7 @@ func TestBareEvents(t *testing.T) {
 
 func TestMultiReturnWithStruct(t *testing.T) {
 	const definition = `[
-	{ "name" : "multi", "const" : false, "outputs": [ { "name": "Int", "type": "uint256" }, { "name": "String", "type": "string" } ] }]`
+	{ "name" : "multi", "constant" : false, "outputs": [ { "name": "Int", "type": "uint256" }, { "name": "String", "type": "string" } ] }]`
 
 	abi, err := JSON(strings.NewReader(definition))
 	if err != nil {
@@ -599,7 +800,7 @@ func TestMultiReturnWithStruct(t *testing.T) {
 
 func TestMultiReturnWithSlice(t *testing.T) {
 	const definition = `[
-	{ "name" : "multi", "const" : false, "outputs": [ { "name": "Int", "type": "uint256" }, { "name": "String", "type": "string" } ] }]`
+	{ "name" : "multi", "constant" : false, "outputs": [ { "name": "Int", "type": "uint256" }, { "name": "String", "type": "string" } ] }]`
 
 	abi, err := JSON(strings.NewReader(definition))
 	if err != nil {
@@ -635,8 +836,8 @@ func TestMultiReturnWithSlice(t *testing.T) {
 
 func TestMarshalArrays(t *testing.T) {
 	const definition = `[
-	{ "name" : "bytes32", "const" : false, "outputs": [ { "type": "bytes32" } ] },
-	{ "name" : "bytes10", "const" : false, "outputs": [ { "type": "bytes10" } ] }
+	{ "name" : "bytes32", "constant" : false, "outputs": [ { "type": "bytes32" } ] },
+	{ "name" : "bytes10", "constant" : false, "outputs": [ { "type": "bytes10" } ] }
 	]`
 
 	abi, err := JSON(strings.NewReader(definition))
@@ -694,14 +895,14 @@ func TestMarshalArrays(t *testing.T) {
 
 func TestUnmarshal(t *testing.T) {
 	const definition = `[
-	{ "name" : "int", "const" : false, "outputs": [ { "type": "uint256" } ] },
-	{ "name" : "bool", "const" : false, "outputs": [ { "type": "bool" } ] },
-	{ "name" : "bytes", "const" : false, "outputs": [ { "type": "bytes" } ] },
-	{ "name" : "fixed", "const" : false, "outputs": [ { "type": "bytes32" } ] },
-	{ "name" : "multi", "const" : false, "outputs": [ { "type": "bytes" }, { "type": "bytes" } ] },
-	{ "name" : "addressSliceSingle", "const" : false, "outputs": [ { "type": "address[]" } ] },
-	{ "name" : "addressSliceDouble", "const" : false, "outputs": [ { "name": "a", "type": "address[]" }, { "name": "b", "type": "address[]" } ] },
-	{ "name" : "mixedBytes", "const" : true, "outputs": [ { "name": "a", "type": "bytes" }, { "name": "b", "type": "bytes32" } ] }]`
+	{ "name" : "int", "constant" : false, "outputs": [ { "type": "uint256" } ] },
+	{ "name" : "bool", "constant" : false, "outputs": [ { "type": "bool" } ] },
+	{ "name" : "bytes", "constant" : false, "outputs": [ { "type": "bytes" } ] },
+	{ "name" : "fixed", "constant" : false, "outputs": [ { "type": "bytes32" } ] },
+	{ "name" : "multi", "constant" : false, "outputs": [ { "type": "bytes" }, { "type": "bytes" } ] },
+	{ "name" : "addressSliceSingle", "constant" : false, "outputs": [ { "type": "address[]" } ] },
+	{ "name" : "addressSliceDouble", "constant" : false, "outputs": [ { "name": "a", "type": "address[]" }, { "name": "b", "type": "address[]" } ] },
+	{ "name" : "mixedBytes", "constant" : true, "outputs": [ { "name": "a", "type": "bytes" }, { "name": "b", "type": "bytes32" } ] }]`
 
 	abi, err := JSON(strings.NewReader(definition))
 	if err != nil {
diff --git a/accounts/abi/error.go b/accounts/abi/error.go
new file mode 100644
index 000000000..67739c21d
--- /dev/null
+++ b/accounts/abi/error.go
@@ -0,0 +1,79 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package abi
+
+import (
+	"fmt"
+	"reflect"
+)
+
+// formatSliceString formats the reflection kind with the given slice size
+// and returns a formatted string representation.
+func formatSliceString(kind reflect.Kind, sliceSize int) string {
+	if sliceSize == -1 {
+		return fmt.Sprintf("[]%v", kind)
+	}
+	return fmt.Sprintf("[%d]%v", sliceSize, kind)
+}
+
+// sliceTypeCheck checks that the given slice can by assigned to the reflection
+// type in t.
+func sliceTypeCheck(t Type, val reflect.Value) error {
+	if val.Kind() != reflect.Slice && val.Kind() != reflect.Array {
+		return typeErr(formatSliceString(t.Kind, t.SliceSize), val.Type())
+	}
+	if t.IsArray && val.Len() != t.SliceSize {
+		return typeErr(formatSliceString(t.Elem.Kind, t.SliceSize), formatSliceString(val.Type().Elem().Kind(), val.Len()))
+	}
+
+	if t.Elem.IsSlice {
+		if val.Len() > 0 {
+			return sliceTypeCheck(*t.Elem, val.Index(0))
+		}
+	} else if t.Elem.IsArray {
+		return sliceTypeCheck(*t.Elem, val.Index(0))
+	}
+
+	if elemKind := val.Type().Elem().Kind(); elemKind != t.Elem.Kind {
+		return typeErr(formatSliceString(t.Elem.Kind, t.SliceSize), val.Type())
+	}
+	return nil
+}
+
+// typeCheck checks that the given reflection value can be assigned to the reflection
+// type in t.
+func typeCheck(t Type, value reflect.Value) error {
+	if t.IsSlice || t.IsArray {
+		return sliceTypeCheck(t, value)
+	}
+
+	// Check base type validity. Element types will be checked later on.
+	if t.Kind != value.Kind() {
+		return typeErr(t.Kind, value.Kind())
+	}
+	return nil
+}
+
+// varErr returns a formatted error.
+func varErr(expected, got reflect.Kind) error {
+	return typeErr(expected, got)
+}
+
+// typeErr returns a formatted type casting error.
+func typeErr(expected, got interface{}) error {
+	return fmt.Errorf("abi: cannot use %v as type %v as argument", got, expected)
+}
diff --git a/accounts/abi/method.go b/accounts/abi/method.go
index 206c7d408..f3d1a44b5 100644
--- a/accounts/abi/method.go
+++ b/accounts/abi/method.go
@@ -18,6 +18,7 @@ package abi
 
 import (
 	"fmt"
+	"reflect"
 	"strings"
 
 	"github.com/ethereum/go-ethereum/crypto"
@@ -38,6 +39,44 @@ type Method struct {
 	Outputs []Argument
 }
 
+func (m Method) pack(method Method, args ...interface{}) ([]byte, error) {
+	// Make sure arguments match up and pack them
+	if len(args) != len(method.Inputs) {
+		return nil, fmt.Errorf("argument count mismatch: %d for %d", len(args), len(method.Inputs))
+	}
+	// variable input is the output appended at the end of packed
+	// output. This is used for strings and bytes types input.
+	var variableInput []byte
+
+	var ret []byte
+	for i, a := range args {
+		input := method.Inputs[i]
+		// pack the input
+		packed, err := input.Type.pack(reflect.ValueOf(a))
+		if err != nil {
+			return nil, fmt.Errorf("`%s` %v", method.Name, err)
+		}
+
+		// check for a slice type (string, bytes, slice)
+		if input.Type.requiresLengthPrefix() {
+			// calculate the offset
+			offset := len(method.Inputs)*32 + len(variableInput)
+			// set the offset
+			ret = append(ret, packNum(reflect.ValueOf(offset), UintTy)...)
+			// Append the packed output to the variable input. The variable input
+			// will be appended at the end of the input.
+			variableInput = append(variableInput, packed...)
+		} else {
+			// append the packed value to the input
+			ret = append(ret, packed...)
+		}
+	}
+	// append the variable input at the end of the packed input
+	ret = append(ret, variableInput...)
+
+	return ret, nil
+}
+
 // Sig returns the methods string signature according to the ABI spec.
 //
 // Example
diff --git a/accounts/abi/numbers.go b/accounts/abi/numbers.go
index 084701de5..5a31cf2b5 100644
--- a/accounts/abi/numbers.go
+++ b/accounts/abi/numbers.go
@@ -24,8 +24,8 @@ import (
 )
 
 var (
-	big_t     = reflect.TypeOf(&big.Int{})
-	ubig_t    = reflect.TypeOf(&big.Int{})
+	big_t     = reflect.TypeOf(big.Int{})
+	ubig_t    = reflect.TypeOf(big.Int{})
 	byte_t    = reflect.TypeOf(byte(0))
 	byte_ts   = reflect.TypeOf([]byte(nil))
 	uint_t    = reflect.TypeOf(uint(0))
diff --git a/accounts/abi/packing.go b/accounts/abi/packing.go
new file mode 100644
index 000000000..c765dfdf3
--- /dev/null
+++ b/accounts/abi/packing.go
@@ -0,0 +1,65 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package abi
+
+import (
+	"reflect"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+// packBytesSlice packs the given bytes as [L, V] as the canonical representation
+// bytes slice
+func packBytesSlice(bytes []byte, l int) []byte {
+	len := packNum(reflect.ValueOf(l), UintTy)
+	return append(len, common.RightPadBytes(bytes, (l+31)/32*32)...)
+}
+
+// packElement packs the given reflect value according to the abi specification in
+// t.
+func packElement(t Type, reflectValue reflect.Value) []byte {
+	switch t.T {
+	case IntTy, UintTy:
+		return packNum(reflectValue, t.T)
+	case StringTy:
+		return packBytesSlice([]byte(reflectValue.String()), reflectValue.Len())
+	case AddressTy:
+		if reflectValue.Kind() == reflect.Array {
+			reflectValue = mustArrayToByteSlice(reflectValue)
+		}
+
+		return common.LeftPadBytes(reflectValue.Bytes(), 32)
+	case BoolTy:
+		if reflectValue.Bool() {
+			return common.LeftPadBytes(common.Big1.Bytes(), 32)
+		} else {
+			return common.LeftPadBytes(common.Big0.Bytes(), 32)
+		}
+	case BytesTy:
+		if reflectValue.Kind() == reflect.Array {
+			reflectValue = mustArrayToByteSlice(reflectValue)
+		}
+		return packBytesSlice(reflectValue.Bytes(), reflectValue.Len())
+	case FixedBytesTy:
+		if reflectValue.Kind() == reflect.Array {
+			reflectValue = mustArrayToByteSlice(reflectValue)
+		}
+
+		return common.RightPadBytes(reflectValue.Bytes(), 32)
+	}
+	panic("abi: fatal error")
+}
diff --git a/accounts/abi/reflect.go b/accounts/abi/reflect.go
new file mode 100644
index 000000000..780c64c66
--- /dev/null
+++ b/accounts/abi/reflect.go
@@ -0,0 +1,64 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package abi
+
+import "reflect"
+
+// indirect recursively dereferences the value until it either gets the value
+// or finds a big.Int
+func indirect(v reflect.Value) reflect.Value {
+	if v.Kind() == reflect.Ptr && v.Elem().Type() != big_t {
+		return indirect(v.Elem())
+	}
+	return v
+}
+
+// reflectIntKind returns the reflect using the given size and
+// unsignedness.
+func reflectIntKind(unsigned bool, size int) reflect.Kind {
+	switch size {
+	case 8:
+		if unsigned {
+			return reflect.Uint8
+		}
+		return reflect.Int8
+	case 16:
+		if unsigned {
+			return reflect.Uint16
+		}
+		return reflect.Int16
+	case 32:
+		if unsigned {
+			return reflect.Uint32
+		}
+		return reflect.Int32
+	case 64:
+		if unsigned {
+			return reflect.Uint64
+		}
+		return reflect.Int64
+	}
+	return reflect.Ptr
+}
+
+// mustArrayToBytesSlice creates a new byte slice with the exact same size as value
+// and copies the bytes in value to the new slice.
+func mustArrayToByteSlice(value reflect.Value) reflect.Value {
+	slice := reflect.MakeSlice(reflect.TypeOf([]byte{}), value.Len(), value.Len())
+	reflect.Copy(slice, value)
+	return slice
+}
diff --git a/accounts/abi/type.go b/accounts/abi/type.go
index 5a5a5ac49..2235bad61 100644
--- a/accounts/abi/type.go
+++ b/accounts/abi/type.go
@@ -21,8 +21,6 @@ import (
 	"reflect"
 	"regexp"
 	"strconv"
-
-	"github.com/ethereum/go-ethereum/common"
 )
 
 const (
@@ -40,53 +38,60 @@ const (
 
 // Type is the reflection of the supported argument type
 type Type struct {
-	IsSlice   bool
-	SliceSize int
+	IsSlice, IsArray bool
+	SliceSize        int
+
+	Elem *Type
+
+	Kind reflect.Kind
+	Type reflect.Type
+	Size int
+	T    byte // Our own type checking
 
-	Kind       reflect.Kind
-	Type       reflect.Type
-	Size       int
-	T          byte   // Our own type checking
 	stringKind string // holds the unparsed string for deriving signatures
 }
 
 var (
+	// fullTypeRegex parses the abi types
+	//
+	// Types can be in the format of:
+	//
+	// 	Input  = Type [ "[" [ Number ] "]" ] Name .
+	// 	Type   = [ "u" ] "int" [ Number ] .
+	//
+	// Examples:
+	//
+	//      string     int       uint       real
+	//      string32   int8      uint8      uint[]
+	//      address    int256    uint256    real[2]
 	fullTypeRegex = regexp.MustCompile("([a-zA-Z0-9]+)(\\[([0-9]*)?\\])?")
-	typeRegex     = regexp.MustCompile("([a-zA-Z]+)([0-9]*)?")
+	// typeRegex parses the abi sub types
+	typeRegex = regexp.MustCompile("([a-zA-Z]+)([0-9]*)?")
 )
 
-// NewType returns a fully parsed Type given by the input string or an error if it  can't be parsed.
-//
-// Strings can be in the format of:
-//
-// 	Input  = Type [ "[" [ Number ] "]" ] Name .
-// 	Type   = [ "u" ] "int" [ Number ] .
-//
-// Examples:
-//
-//      string     int       uint       real
-//      string32   int8      uint8      uint[]
-//      address    int256    uint256    real[2]
+// NewType creates a new reflection type of abi type given in t.
 func NewType(t string) (typ Type, err error) {
-	// 1. full string 2. type 3. (opt.) is slice 4. (opt.) size
-	// parse the full representation of the abi-type definition; including:
-	// * full string
-	// * type
-	// 	* is slice
-	//	* slice size
 	res := fullTypeRegex.FindAllStringSubmatch(t, -1)[0]
-
 	// check if type is slice and parse type.
 	switch {
 	case res[3] != "":
 		// err is ignored. Already checked for number through the regexp
 		typ.SliceSize, _ = strconv.Atoi(res[3])
-		typ.IsSlice = true
+		typ.IsArray = true
 	case res[2] != "":
 		typ.IsSlice, typ.SliceSize = true, -1
 	case res[0] == "":
 		return Type{}, fmt.Errorf("abi: type parse error: %s", t)
 	}
+	if typ.IsArray || typ.IsSlice {
+		sliceType, err := NewType(res[1])
+		if err != nil {
+			return Type{}, err
+		}
+		typ.Elem = &sliceType
+		typ.stringKind = sliceType.stringKind + t[len(res[1]):]
+		return typ, nil
+	}
 
 	// parse the type and size of the abi-type.
 	parsedType := typeRegex.FindAllStringSubmatch(res[1], -1)[0]
@@ -106,24 +111,24 @@ func NewType(t string) (typ Type, err error) {
 		varSize = 256
 		t += "256"
 	}
+	typ.stringKind = t
 
 	switch varType {
 	case "int":
-		typ.Kind = reflect.Int
+		typ.Kind = reflectIntKind(false, varSize)
 		typ.Type = big_t
 		typ.Size = varSize
 		typ.T = IntTy
 	case "uint":
-		typ.Kind = reflect.Uint
+		typ.Kind = reflectIntKind(true, varSize)
 		typ.Type = ubig_t
 		typ.Size = varSize
 		typ.T = UintTy
 	case "bool":
 		typ.Kind = reflect.Bool
 		typ.T = BoolTy
-	case "real": // TODO
-		typ.Kind = reflect.Invalid
 	case "address":
+		typ.Kind = reflect.Array
 		typ.Type = address_t
 		typ.Size = 20
 		typ.T = AddressTy
@@ -131,123 +136,55 @@ func NewType(t string) (typ Type, err error) {
 		typ.Kind = reflect.String
 		typ.Size = -1
 		typ.T = StringTy
-		if varSize > 0 {
-			typ.Size = 32
-		}
-	case "hash":
-		typ.Kind = reflect.Array
-		typ.Size = 32
-		typ.Type = hash_t
-		typ.T = HashTy
 	case "bytes":
-		typ.Kind = reflect.Array
-		typ.Type = byte_ts
-		typ.Size = varSize
+		sliceType, _ := NewType("uint8")
+		typ.Elem = &sliceType
 		if varSize == 0 {
+			typ.IsSlice = true
 			typ.T = BytesTy
+			typ.SliceSize = -1
 		} else {
+			typ.IsArray = true
 			typ.T = FixedBytesTy
+			typ.SliceSize = varSize
 		}
 	default:
 		return Type{}, fmt.Errorf("unsupported arg type: %s", t)
 	}
-	typ.stringKind = t
 
 	return
 }
 
+// String implements Stringer
 func (t Type) String() (out string) {
 	return t.stringKind
 }
 
-// packBytesSlice packs the given bytes as [L, V] as the canonical representation
-// bytes slice
-func packBytesSlice(bytes []byte, l int) []byte {
-	len := packNum(reflect.ValueOf(l), UintTy)
-	return append(len, common.RightPadBytes(bytes, (l+31)/32*32)...)
-}
-
-// Test the given input parameter `v` and checks if it matches certain
-// criteria
-// * Big integers are checks for ptr types and if the given value is
-//   assignable
-// * Integer are checked for size
-// * Strings, addresses and bytes are checks for type and size
-func (t Type) pack(v interface{}) ([]byte, error) {
-	value := reflect.ValueOf(v)
-	switch kind := value.Kind(); kind {
-	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
-		// check input is unsigned
-		if t.Type != ubig_t {
-			return nil, fmt.Errorf("abi: type mismatch: %s for %T", t.Type, v)
-		}
-
-		// no implicit type casting
-		if int(value.Type().Size()*8) != t.Size {
-			return nil, fmt.Errorf("abi: cannot use type %T as type uint%d", v, t.Size)
-		}
-
-		return packNum(value, t.T), nil
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		if t.Type != ubig_t {
-			return nil, fmt.Errorf("type mismatch: %s for %T", t.Type, v)
-		}
-
-		// no implicit type casting
-		if int(value.Type().Size()*8) != t.Size {
-			return nil, fmt.Errorf("abi: cannot use type %T as type uint%d", v, t.Size)
-		}
-		return packNum(value, t.T), nil
-	case reflect.Ptr:
-		// If the value is a ptr do a assign check (only used by
-		// big.Int for now)
-		if t.Type == ubig_t && value.Type() != ubig_t {
-			return nil, fmt.Errorf("type mismatch: %s for %T", t.Type, v)
-		}
-		return packNum(value, t.T), nil
-	case reflect.String:
-		if t.Size > -1 && value.Len() > t.Size {
-			return nil, fmt.Errorf("%v out of bound. %d for %d", value.Kind(), value.Len(), t.Size)
-		}
-
-		return packBytesSlice([]byte(value.String()), value.Len()), nil
-	case reflect.Slice:
-		// Byte slice is a special case, it gets treated as a single value
-		if t.T == BytesTy {
-			return packBytesSlice(value.Bytes(), value.Len()), nil
-		}
-
-		if t.SliceSize > -1 && value.Len() > t.SliceSize {
-			return nil, fmt.Errorf("%v out of bound. %d for %d", value.Kind(), value.Len(), t.Size)
-		}
+func (t Type) pack(v reflect.Value) ([]byte, error) {
+	// dereference pointer first if it's a pointer
+	v = indirect(v)
 
-		// Signed / Unsigned check
-		if value.Type() == big_t && (t.T != IntTy && isSigned(value)) || (t.T == UintTy && isSigned(value)) {
-			return nil, fmt.Errorf("slice of incompatible types.")
-		}
+	if err := typeCheck(t, v); err != nil {
+		return nil, err
+	}
 
+	if (t.IsSlice || t.IsArray) && t.T != BytesTy && t.T != FixedBytesTy {
 		var packed []byte
-		for i := 0; i < value.Len(); i++ {
-			val, err := t.pack(value.Index(i).Interface())
+		for i := 0; i < v.Len(); i++ {
+			val, err := t.Elem.pack(v.Index(i))
 			if err != nil {
 				return nil, err
 			}
 			packed = append(packed, val...)
 		}
-		return packBytesSlice(packed, value.Len()), nil
-	case reflect.Bool:
-		if value.Bool() {
-			return common.LeftPadBytes(common.Big1.Bytes(), 32), nil
-		} else {
-			return common.LeftPadBytes(common.Big0.Bytes(), 32), nil
-		}
-	case reflect.Array:
-		if v, ok := value.Interface().(common.Address); ok {
-			return common.LeftPadBytes(v[:], 32), nil
-		} else if v, ok := value.Interface().(common.Hash); ok {
-			return v[:], nil
-		}
+		return packBytesSlice(packed, v.Len()), nil
 	}
 
-	return nil, fmt.Errorf("ABI: bad input given %v", value.Kind())
+	return packElement(t, v), nil
+}
+
+// requireLengthPrefix returns whether the type requires any sort of length
+// prefixing.
+func (t Type) requiresLengthPrefix() bool {
+	return t.T != FixedBytesTy && (t.T == StringTy || t.T == BytesTy || t.IsSlice || t.IsArray)
 }