Clean up CRC-16 implementations

7 files changed, 33 insertions, 19 deletions

diff --git a/src/org/traccar/helper/Checksum.java b/src/org/traccar/helper/Checksum.java
index cdf1bbf50..69c9dd499 100644
--- a/src/org/traccar/helper/Checksum.java
+++ b/src/org/traccar/helper/Checksum.java
@@ -91,8 +91,14 @@ public class Checksum {
         0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
     };
 
-    public static final int CRC16_CCITT = 0xFFFF;
-    public static final int CRC16_CCITT_XOROUT = 0xFFFF;
+    // More info: http://reveng.sourceforge.net/crc-catalogue/16.htm
+    public static final String CRC16_X25 = "X-25";
+    public static final String CRC16_CCITT_FALSE = "CCITT-FALSE";
+    public static final String CRC16_KERMIT = "KERMIT";
+    public static final String CRC16_XMODEM = "XMODEM";
+    public static final String CRC16_AUG_CCITT = "AUG-CCITT";
+    public static final String CRC16_GENIBUS = "GENIBUS";
+    public static final String CRC16_MCRF4XX = "MCRF4XX";
 
     private static int crc16Unreflected(ByteBuffer buf, int crc_in, int[] table) {
         int crc16 = crc_in;
@@ -110,16 +116,24 @@ public class Checksum {
         return crc16 & 0xFFFF;
     }
 
-    public static int crc16Ccitt(ByteBuffer buf) {
-        return crc16Reflected(buf, 0xFFFF, CRC16_CCITT_TABLE_REVERSE) ^ 0xFFFF;
-    }
-
-    public static int crc16X25Ccitt(ByteBuffer buf) {
-        return crc16Unreflected(buf, 0xFFFF, CRC16_CCITT_TABLE);
-    }
-
-    public static int crc16Ccitt(ByteBuffer buf, int seed, int xorout) {
-        return crc16Reflected(buf, seed, CRC16_CCITT_TABLE_REVERSE) ^ xorout;
+    public static int crc16(String type, ByteBuffer buf) {
+        switch (type) {
+            case CRC16_X25:
+                return crc16Reflected(buf, 0xFFFF, CRC16_CCITT_TABLE_REVERSE) ^ 0xFFFF;
+            case CRC16_CCITT_FALSE:
+                return crc16Unreflected(buf, 0xFFFF, CRC16_CCITT_TABLE);
+            case CRC16_KERMIT:
+                return crc16Reflected(buf, 0, CRC16_CCITT_TABLE_REVERSE);
+            case CRC16_XMODEM:
+                return crc16Unreflected(buf, 0, CRC16_CCITT_TABLE);
+            case CRC16_AUG_CCITT:
+                return crc16Unreflected(buf, 0x1d0f, CRC16_CCITT_TABLE);
+            case CRC16_GENIBUS:
+                return crc16Unreflected(buf, 0xFFFF, CRC16_CCITT_TABLE) ^ 0xFFFF;
+            case CRC16_MCRF4XX:
+                return crc16Reflected(buf, 0xFFFF, CRC16_CCITT_TABLE_REVERSE);
+        }
+        throw new UnsupportedOperationException();
     }
 
     public static int crc32(ByteBuffer buf) {
diff --git a/src/org/traccar/protocol/CastelProtocolDecoder.java b/src/org/traccar/protocol/CastelProtocolDecoder.java
index f93b9762c..d7c6bbf46 100644
--- a/src/org/traccar/protocol/CastelProtocolDecoder.java
+++ b/src/org/traccar/protocol/CastelProtocolDecoder.java
@@ -95,7 +95,7 @@ public class CastelProtocolDecoder extends BaseProtocolDecoder {
                 response.writeByte(version);
                 response.writeBytes(id);
                 response.writeShort(ChannelBuffers.swapShort(MSG_HEARTBEAT_RESPONSE));
-                response.writeShort(Checksum.crc16Ccitt(response.toByteBuffer(0, response.writerIndex())));
+                response.writeShort(Checksum.crc16(Checksum.CRC16_X25, response.toByteBuffer(0, response.writerIndex())));
                 response.writeByte(0x0D); response.writeByte(0x0A);
                 channel.write(response, remoteAddress);
             }
@@ -123,7 +123,7 @@ public class CastelProtocolDecoder extends BaseProtocolDecoder {
                     response.writeInt(0xFFFFFFFF);
                     response.writeShort(0);
                     response.writeInt((int) (System.currentTimeMillis() / 1000));
-                    response.writeShort(Checksum.crc16Ccitt(response.toByteBuffer(0, response.writerIndex())));
+                    response.writeShort(Checksum.crc16(Checksum.CRC16_X25, response.toByteBuffer(0, response.writerIndex())));
                     response.writeByte(0x0D); response.writeByte(0x0A);
                     channel.write(response, remoteAddress);
                 }
diff --git a/src/org/traccar/protocol/CityeasyProtocolEncoder.java b/src/org/traccar/protocol/CityeasyProtocolEncoder.java
index cfe69a462..76c4199e1 100644
--- a/src/org/traccar/protocol/CityeasyProtocolEncoder.java
+++ b/src/org/traccar/protocol/CityeasyProtocolEncoder.java
@@ -33,7 +33,7 @@ public class CityeasyProtocolEncoder extends BaseProtocolEncoder {
         buf.writeShort(type);
         buf.writeBytes(content);
         buf.writeInt(0x0B);
-        buf.writeShort(Checksum.crc16Ccitt(buf.toByteBuffer(), 0, 0));
+        buf.writeShort(Checksum.crc16(Checksum.CRC16_KERMIT, buf.toByteBuffer()));
         buf.writeByte('\r');
         buf.writeByte('\n');
 
diff --git a/src/org/traccar/protocol/Gt06ProtocolDecoder.java b/src/org/traccar/protocol/Gt06ProtocolDecoder.java
index ab5c80cf6..4c744dd9f 100644
--- a/src/org/traccar/protocol/Gt06ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Gt06ProtocolDecoder.java
@@ -81,7 +81,7 @@ public class Gt06ProtocolDecoder extends BaseProtocolDecoder {
             response.writeByte(0x05); // size
             response.writeByte(type);
             response.writeShort(index);
-            response.writeShort(Checksum.crc16Ccitt(response.toByteBuffer(2, 4)));
+            response.writeShort(Checksum.crc16(Checksum.CRC16_X25, response.toByteBuffer(2, 4)));
             response.writeByte(0x0D); response.writeByte(0x0A); // ending
             channel.write(response);
         }
diff --git a/src/org/traccar/protocol/Gt06ProtocolEncoder.java b/src/org/traccar/protocol/Gt06ProtocolEncoder.java
index 9a1bb4571..f5b914b1c 100644
--- a/src/org/traccar/protocol/Gt06ProtocolEncoder.java
+++ b/src/org/traccar/protocol/Gt06ProtocolEncoder.java
@@ -40,7 +40,7 @@ public class Gt06ProtocolEncoder extends BaseProtocolEncoder {
 
         buf.writeShort(0); // message index
 
-        buf.writeShort(Checksum.crc16Ccitt(buf.toByteBuffer(2, buf.writerIndex() - 2)));
+        buf.writeShort(Checksum.crc16(Checksum.CRC16_X25, buf.toByteBuffer(2, buf.writerIndex() - 2)));
 
         buf.writeByte('\r');
         buf.writeByte('\n');
diff --git a/src/org/traccar/protocol/MeiligaoProtocolDecoder.java b/src/org/traccar/protocol/MeiligaoProtocolDecoder.java
index bde28492f..a7d8a884e 100644
--- a/src/org/traccar/protocol/MeiligaoProtocolDecoder.java
+++ b/src/org/traccar/protocol/MeiligaoProtocolDecoder.java
@@ -121,7 +121,7 @@ public class MeiligaoProtocolDecoder extends BaseProtocolDecoder {
             buf.writeBytes(id);
             buf.writeShort(type);
             buf.writeBytes(msg);
-            buf.writeShort(Checksum.crc16X25Ccitt(buf.toByteBuffer()));
+            buf.writeShort(Checksum.crc16(Checksum.CRC16_CCITT_FALSE, buf.toByteBuffer()));
             buf.writeByte('\r');
             buf.writeByte('\n');
 
diff --git a/src/org/traccar/protocol/NavigilProtocolDecoder.java b/src/org/traccar/protocol/NavigilProtocolDecoder.java
index 24c6618bb..142d19fc6 100644
--- a/src/org/traccar/protocol/NavigilProtocolDecoder.java
+++ b/src/org/traccar/protocol/NavigilProtocolDecoder.java
@@ -68,7 +68,7 @@ public class NavigilProtocolDecoder extends BaseProtocolDecoder {
         header.writeShort(MESSAGE_ACKNOWLEDGEMENT);
         header.writeShort(header.capacity() + data.capacity());
         header.writeShort(0);
-        header.writeShort(Checksum.crc16X25Ccitt(data.toByteBuffer()));
+        header.writeShort(Checksum.crc16(Checksum.CRC16_CCITT_FALSE, data.toByteBuffer()));
         header.writeInt(0);
         header.writeInt((int) (System.currentTimeMillis() / 1000) + LEAP_SECONDS_DELTA);