Release 2.0

I really hope I don't have to change the API again.

2.0/nfc/crc.go

@@ -0,0 +1,106 @@
+// Copyright (c) 2014, Robert Clausecker <[email protected]>
+//
+// This program 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, version 3.
+//
+// This program 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 General Public License for
+// more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>
+
+// The code in this file is a very direct translation of the code in
+// iso14443-subr.c of the libnfc version 1.7.0 translated to Go for performance
+// reasons.
+
+package nfc
+
+// Calculate an ISO 14443a CRC. Code translated from the code in
+// iso14443a_crc().
+func ISO14443aCRC(data []byte) [2]byte {
+	crc := uint32(0x6363)
+	for _, bt := range data {
+		bt ^= uint8(crc & 0xff)
+		bt ^= bt << 4
+		bt32 := uint32(bt)
+		crc = (crc >> 8) ^ (bt32 << 8) ^ (bt32 << 3) ^ (bt32 >> 4)
+	}
+
+	return [2]byte{byte(crc & 0xff), byte((crc >> 8) & 0xff)}
+}
+
+// Calculate an ISO 14443a CRC and append it to the supplied slice.
+func AppendISO14443aCRC(data []byte) []byte {
+	crc := ISO14443aCRC(data)
+	return append(data, crc[0], crc[1])
+}
+
+// Calculate an ISO 14443b CRC. Code translated from the code in
+// iso14443b_crc().
+func ISO14443bCRC(data []byte) [2]byte {
+	crc := uint32(0xffff)
+	for _, bt := range data {
+		bt ^= uint8(crc & 0xff)
+		bt ^= bt << 4
+		bt32 := uint32(bt)
+		crc = (crc >> 8) ^ (bt32 << 8) ^ (bt32 << 3) ^ (bt32 >> 4)
+	}
+
+	return [2]byte{byte(crc & 0xff), byte((crc >> 8) & 0xff)}
+}
+
+// Calculate an ISO 14443b CRC and append it to the supplied slice.
+func AppendISO14443bCRC(data []byte) []byte {
+	crc := ISO14443bCRC(data)
+	return append(data, crc[0], crc[1])
+}
+
+// Locate historical bytes according to ISO/IEC 14443-4 sec. 5.2.7. Return nil
+// if that fails.
+func ISO14443aLocateHistoricalBytes(ats []byte) []byte {
+	if len(ats) > 0 {
+		offset := 1
+		if ats[0]&0x10 != 0 {
+			offset++
+		}
+
+		if ats[1]&0x20 != 0 {
+			offset++
+		}
+
+		if ats[2]&0x40 != 0 {
+			offset++
+		}
+
+		if len(ats) > offset {
+			return ats[offset:]
+		}
+	}
+
+	return nil
+}
+
+// Add cascade tags (0x88) in UID. See ISO/IEC 14443-3 sec. 6.4.4.
+func ISO14443CascadeUID(uid []byte) (cascadedUID []byte) {
+	switch len(uid) {
+	case 7:
+		cascadedUID = make([]byte, 8)
+		cascadedUID[0] = 0x88
+		copy(cascadedUID[1:], uid)
+	case 10:
+		cascadedUID = make([]byte, 12)
+		cascadedUID[0] = 0x88
+		copy(cascadedUID[1:4], uid)
+		cascadedUID[4] = 0x88
+		copy(cascadedUID[5:], uid[3:])
+	case 4:
+		fallthrough
+	default:
+		cascadedUID = append(cascadedUID, uid...)
+	}
+
+	return
+}