1 files changed, 190 insertions, 0 deletions
diff --git a/common/icap.go b/common/icap.go
new file mode 100644
index 000000000..a36e669b3
--- /dev/null
+++ b/common/icap.go
@@ -0,0 +1,190 @@
+// Copyright 2015 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/>.
+
+// Spec at https://github.com/ethereum/wiki/wiki/ICAP:-Inter-exchange-Client-Address-Protocol
+
+package common
+
+import (
+	"errors"
+	"math/big"
+	"strconv"
+	"strings"
+)
+
+var (
+	Base36Chars          = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	ICAPLengthError      = errors.New("Invalid ICAP length")
+	ICAPEncodingError    = errors.New("Invalid ICAP encoding")
+	ICAPChecksumError    = errors.New("Invalid ICAP checksum")
+	ICAPCountryCodeError = errors.New("Invalid ICAP country code")
+	ICAPAssetIdentError  = errors.New("Invalid ICAP asset identifier")
+	ICAPInstCodeError    = errors.New("Invalid ICAP institution code")
+	ICAPClientIdentError = errors.New("Invalid ICAP client identifier")
+)
+
+func ICAPToAddress(s string) (Address, error) {
+	switch len(s) {
+	case 35: // "XE" + 2 digit checksum + 31 base-36 chars of address
+		return parseICAP(s)
+	case 34: // "XE" + 2 digit checksum + 30 base-36 chars of address
+		return parseICAP(s)
+	case 20: // "XE" + 2 digit checksum + 3-char asset identifier +
+		// 4-char institution identifier + 9-char institution client identifier
+		return parseIndirectICAP(s)
+	default:
+		return Address{}, ICAPLengthError
+	}
+}
+
+func parseICAP(s string) (Address, error) {
+	if !strings.HasPrefix(s, "XE") {
+		return Address{}, ICAPCountryCodeError
+	}
+	if err := validCheckSum(s); err != nil {
+		return Address{}, err
+	}
+	// checksum is ISO13616, Ethereum address is base-36
+	bigAddr, _ := new(big.Int).SetString(s[4:], 36)
+	return BigToAddress(bigAddr), nil
+}
+
+func parseIndirectICAP(s string) (Address, error) {
+	if !strings.HasPrefix(s, "XE") {
+		return Address{}, ICAPCountryCodeError
+	}
+	if s[4:7] != "ETH" {
+		return Address{}, ICAPAssetIdentError
+	}
+	if err := validCheckSum(s); err != nil {
+		return Address{}, err
+	}
+	// TODO: integrate with ICAP namereg
+	return Address{}, errors.New("not implemented")
+}
+
+func AddressToICAP(a Address) (string, error) {
+	enc := base36Encode(a.Big())
+	// zero padd encoded address to Direct ICAP length if needed
+	if len(enc) < 30 {
+		enc = join(strings.Repeat("0", 30-len(enc)), enc)
+	}
+	icap := join("XE", checkDigits(enc), enc)
+	return icap, nil
+}
+
+// TODO: integrate with ICAP namereg when it's available
+func AddressToIndirectICAP(a Address, instCode string) (string, error) {
+	// return addressToIndirectICAP(a, instCode)
+	return "", errors.New("not implemented")
+}
+
+func addressToIndirectICAP(a Address, instCode string) (string, error) {
+	// TODO: add addressToClientIdent which grabs client ident from ICAP namereg
+	//clientIdent := addressToClientIdent(a)
+	clientIdent := "todo"
+	return clientIdentToIndirectICAP(instCode, clientIdent)
+}
+
+func clientIdentToIndirectICAP(instCode, clientIdent string) (string, error) {
+	if len(instCode) != 4 || !validBase36(instCode) {
+		return "", ICAPInstCodeError
+	}
+	if len(clientIdent) != 9 || !validBase36(instCode) {
+		return "", ICAPClientIdentError
+	}
+
+	// currently ETH is only valid asset identifier
+	s := join("ETH", instCode, clientIdent)
+	return join("XE", checkDigits(s), s), nil
+}
+
+// https://en.wikipedia.org/wiki/International_Bank_Account_Number#Validating_the_IBAN
+func validCheckSum(s string) error {
+	s = join(s[4:], s[:4])
+	expanded, err := iso13616Expand(s)
+	if err != nil {
+		return err
+	}
+	checkSumNum, _ := new(big.Int).SetString(expanded, 10)
+	if checkSumNum.Mod(checkSumNum, Big97).Cmp(Big1) != 0 {
+		return ICAPChecksumError
+	}
+	return nil
+}
+
+func checkDigits(s string) string {
+	expanded, _ := iso13616Expand(strings.Join([]string{s, "XE00"}, ""))
+	num, _ := new(big.Int).SetString(expanded, 10)
+	num.Sub(Big98, num.Mod(num, Big97))
+
+	checkDigits := num.String()
+	// zero padd checksum
+	if len(checkDigits) == 1 {
+		checkDigits = join("0", checkDigits)
+	}
+	return checkDigits
+}
+
+// not base-36, but expansion to decimal literal: A = 10, B = 11, ... Z = 35
+func iso13616Expand(s string) (string, error) {
+	var parts []string
+	if !validBase36(s) {
+		return "", ICAPEncodingError
+	}
+	for _, c := range s {
+		i := uint64(c)
+		if i >= 65 {
+			parts = append(parts, strconv.FormatUint(uint64(c)-55, 10))
+		} else {
+			parts = append(parts, string(c))
+		}
+	}
+	return join(parts...), nil
+}
+
+func base36Encode(i *big.Int) string {
+	var chars []rune
+	x := new(big.Int)
+	for {
+		x.Mod(i, Big36)
+		chars = append(chars, rune(Base36Chars[x.Uint64()]))
+		i.Div(i, Big36)
+		if i.Cmp(Big0) == 0 {
+			break
+		}
+	}
+	// reverse slice
+	for i, j := 0, len(chars)-1; i < j; i, j = i+1, j-1 {
+		chars[i], chars[j] = chars[j], chars[i]
+	}
+	return string(chars)
+}
+
+func validBase36(s string) bool {
+	for _, c := range s {
+		i := uint64(c)
+		// 0-9 or A-Z
+		if i < 48 || (i > 57 && i < 65) || i > 90 {
+			return false
+		}
+	}
+	return true
+}
+
+func join(s ...string) string {
+	return strings.Join(s, "")
+}