Merge pull request #33 from ledgerwatch/rlp_u32

rlp.U32 method

rlp/parse.go

@@ -127,6 +127,28 @@ func U64(payload []byte, pos int) (int, uint64, error) {
 	return dataPos + dataLen, r, nil
 }
 
+// U32 parses uint64 number from given payload at given position
+func U32(payload []byte, pos int) (int, uint32, error) {
+	dataPos, dataLen, isList, err := Prefix(payload, pos)
+	if err != nil {
+		return 0, 0, err
+	}
+	if isList {
+		return 0, 0, fmt.Errorf("uint32 must be a string, not isList")
+	}
+	if dataLen > 4 {
+		return 0, 0, fmt.Errorf("uint32 must not be more than 4 bytes long, got %d", dataLen)
+	}
+	if dataLen > 0 && payload[dataPos] == 0 {
+		return 0, 0, fmt.Errorf("integer encoding for RLP must not have leading zeros: %x", payload[dataPos:dataPos+dataLen])
+	}
+	var r uint32
+	for _, b := range payload[dataPos : dataPos+dataLen] {
+		r = (r << 8) | uint32(b)
+	}
+	return dataPos + dataLen, r, nil
+}
+
 // U256 parses uint256 number from given payload at given position
 func U256(payload []byte, pos int, x *uint256.Int) (int, error) {
 	dataPos, dataLen, err := String(payload, pos)

rlp/parse_test.go

@@ -0,0 +1,58 @@
+package rlp
+
+import (
+	"encoding/hex"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func decodeHex(in string) []byte {
+	payload, err := hex.DecodeString(in)
+	if err != nil {
+		panic(err)
+	}
+	return payload
+}
+
+var parseU64Tests = []struct {
+	payload   []byte
+	expectPos int
+	expectRes uint64
+	expectErr error
+}{
+	{payload: decodeHex("820400"), expectPos: 3, expectRes: 1024},
+	{payload: decodeHex("07"), expectPos: 1, expectRes: 7},
+}
+
+var parseU32Tests = []struct {
+	payload   []byte
+	expectPos int
+	expectRes uint32
+	expectErr error
+}{
+	{payload: decodeHex("820400"), expectPos: 3, expectRes: 1024},
+	{payload: decodeHex("07"), expectPos: 1, expectRes: 7},
+}
+
+func TestPrimitives(t *testing.T) {
+	for i, tt := range parseU64Tests {
+		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+			assert := assert.New(t)
+			pos, res, err := U64(tt.payload, 0)
+			assert.NoError(err)
+			assert.Equal(tt.expectPos, pos)
+			assert.Equal(tt.expectRes, res)
+		})
+	}
+	for i, tt := range parseU32Tests {
+		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+			assert := assert.New(t)
+			pos, res, err := U32(tt.payload, 0)
+			assert.NoError(err)
+			assert.Equal(tt.expectPos, pos)
+			assert.Equal(tt.expectRes, res)
+		})
+	}
+}