added address utils to find network for address (#174)

Author: bjartek

address.go

@@ -0,0 +1,70 @@
+package overflow
+
+import (
+	"math/big"
+	"strings"
+)
+
+var (
+	linearCodeN = 64
+
+	parityCheckMatrixColumns = []*big.Int{
+		big.NewInt(0x00001), big.NewInt(0x00002), big.NewInt(0x00004), big.NewInt(0x00008),
+		big.NewInt(0x00010), big.NewInt(0x00020), big.NewInt(0x00040), big.NewInt(0x00080),
+		big.NewInt(0x00100), big.NewInt(0x00200), big.NewInt(0x00400), big.NewInt(0x00800),
+		big.NewInt(0x01000), big.NewInt(0x02000), big.NewInt(0x04000), big.NewInt(0x08000),
+		big.NewInt(0x10000), big.NewInt(0x20000), big.NewInt(0x40000), big.NewInt(0x7328d),
+		big.NewInt(0x6689a), big.NewInt(0x6112f), big.NewInt(0x6084b), big.NewInt(0x433fd),
+		big.NewInt(0x42aab), big.NewInt(0x41951), big.NewInt(0x233ce), big.NewInt(0x22a81),
+		big.NewInt(0x21948), big.NewInt(0x1ef60), big.NewInt(0x1deca), big.NewInt(0x1c639),
+		big.NewInt(0x1bdd8), big.NewInt(0x1a535), big.NewInt(0x194ac), big.NewInt(0x18c46),
+		big.NewInt(0x1632b), big.NewInt(0x1529b), big.NewInt(0x14a43), big.NewInt(0x13184),
+		big.NewInt(0x12942), big.NewInt(0x118c1), big.NewInt(0x0f812), big.NewInt(0x0e027),
+		big.NewInt(0x0d00e), big.NewInt(0x0c83c), big.NewInt(0x0b01d), big.NewInt(0x0a831),
+		big.NewInt(0x982b), big.NewInt(0x07034), big.NewInt(0x0682a), big.NewInt(0x05819),
+		big.NewInt(0x03807), big.NewInt(0x007d2), big.NewInt(0x00727), big.NewInt(0x0068e),
+		big.NewInt(0x0067c), big.NewInt(0x0059d), big.NewInt(0x004eb), big.NewInt(0x003b4),
+		big.NewInt(0x0036a), big.NewInt(0x002d9), big.NewInt(0x001c7), big.NewInt(0x0003f),
+	}
+)
+
+func GetNetworkFromAddress(input string) string {
+	address := strings.TrimPrefix(input, "0x")
+	testnet, _ := new(big.Int).SetString("6834ba37b3980209", 16)
+	emulator, _ := new(big.Int).SetString("1cb159857af02018", 16)
+
+	networkCodewords := map[string]*big.Int{
+		"mainnet":  big.NewInt(0),
+		"testnet":  testnet,
+		"emulator": emulator,
+	}
+
+	for network, codeWord := range networkCodewords {
+		if IsValidAddressForNetwork(address, network, codeWord) {
+			return network
+		}
+	}
+	return ""
+}
+
+func IsValidAddressForNetwork(address, network string, codeWord *big.Int) bool {
+	flowAddress, ok := new(big.Int).SetString(address, 16)
+	if !ok {
+		panic("not valid address")
+	}
+	codeWord.Xor(codeWord, flowAddress)
+
+	if codeWord.Cmp(big.NewInt(0)) == 0 {
+		return false
+	}
+
+	parity := big.NewInt(0)
+	for i := 0; i < linearCodeN; i++ {
+		if codeWord.Bit(0) == 1 {
+			parity.Xor(parity, parityCheckMatrixColumns[i])
+		}
+		codeWord.Rsh(codeWord, 1)
+	}
+
+	return parity.Cmp(big.NewInt(0)) == 0 && codeWord.Cmp(big.NewInt(0)) == 0
+}

address_test.go

@@ -23,3 +23,18 @@ func TestGetAddress(t *testing.T) {
 		})
 	}
 }
+
+func TestAddressNetworks(t *testing.T) {
+	t.Run("emulator with prefix", func(t *testing.T) {
+		assert.Equal(t, "emulator", GetNetworkFromAddress("0xf8d6e0586b0a20c7"))
+	})
+	t.Run("emulator", func(t *testing.T) {
+		assert.Equal(t, "emulator", GetNetworkFromAddress("f8d6e0586b0a20c7"))
+	})
+	t.Run("testnet", func(t *testing.T) {
+		assert.Equal(t, "testnet", GetNetworkFromAddress("9a0766d93b6608b7"))
+	})
+	t.Run("mainnet", func(t *testing.T) {
+		assert.Equal(t, "mainnet", GetNetworkFromAddress("f233dcee88fe0abe"))
+	})
+}