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P25 work in progress
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dennis.sheirer
265
src/decode/p25/message/tdu/TDULinkControlMessage.java
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265
src/decode/p25/message/tdu/TDULinkControlMessage.java
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package decode.p25.message.tdu;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import alias.AliasList;
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import bits.BitSetBuffer;
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import decode.p25.message.P25Message;
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import decode.p25.reference.DataUnitID;
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import decode.p25.reference.LinkControlOpcode;
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import decode.p25.reference.Vendor;
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import decode.p25.reference.VendorLinkControlOpcode;
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import edac.CRC;
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import edac.Galois24;
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import edac.ReedSolomon_24_12_13;
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public class TDULinkControlMessage extends P25Message
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{
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public final static Logger mLog = LoggerFactory.getLogger( TDULinkControlMessage.class );
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public static final int[] LC_HEX_0 = { 64,65,66,67,68,69 };
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public static final int[] LC_HEX_1 = { 70,71,72,73,74,75 };
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public static final int[] LC_HEX_2 = { 88,89,90,91,92,93 };
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public static final int[] LC_HEX_3 = { 94,95,96,97,98,99 };
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public static final int[] LC_HEX_4 = { 112,113,114,115,116,117 };
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public static final int[] LC_HEX_5 = { 118,119,120,121,122,123 };
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public static final int[] LC_HEX_6 = { 136,137,138,139,140,141 };
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public static final int[] LC_HEX_7 = { 142,143,144,145,146,147 };
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public static final int[] LC_HEX_8 = { 160,161,162,163,164,165 };
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public static final int[] LC_HEX_9 = { 166,167,168,169,170,171 };
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public static final int[] LC_HEX_10 = { 184,185,186,187,188,189 };
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public static final int[] LC_HEX_11 = { 190,191,192,193,194,195 };
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public static final int[] RS_HEX_0 = { 208,209,210,211,212,213 };
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public static final int[] RS_HEX_1 = { 214,215,216,217,218,219 };
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public static final int[] RS_HEX_2 = { 232,233,234,235,236,237 };
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public static final int[] RS_HEX_3 = { 238,239,240,241,242,243 };
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public static final int[] RS_HEX_4 = { 256,257,258,259,260,261 };
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public static final int[] RS_HEX_5 = { 262,263,264,265,266,267 };
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public static final int[] RS_HEX_6 = { 280,281,282,283,284,285 };
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public static final int[] RS_HEX_7 = { 286,287,288,289,290,291 };
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public static final int[] RS_HEX_8 = { 304,305,306,307,308,309 };
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public static final int[] RS_HEX_9 = { 310,311,312,313,314,315 };
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public static final int[] RS_HEX_10 = { 328,329,330,331,332,333 };
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public static final int[] RS_HEX_11 = { 334,335,336,337,338,339 };
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public static final int ENCRYPTION_FLAG = 64;
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public static final int IMPLICIT_VENDOR_FLAG = 65;
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public static final int[] OPCODE = { 66,67,68,69,70,71 };
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public static final int[] VENDOR = { 72,73,74,75,88,89,90,91 };
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public static final ReedSolomon_24_12_13 mReedSolomonDecoder =
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new ReedSolomon_24_12_13();
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public TDULinkControlMessage( BitSetBuffer message, DataUnitID duid,
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AliasList aliasList )
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{
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super( message, duid, aliasList );
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/* NID CRC is checked in the message framer so a constructed message
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* means it passed the CRC */
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mCRC = new CRC[ 3 ];
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mCRC[ 0 ] = CRC.PASSED;
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checkCRC();
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}
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/**
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* Constructs a TDULinkControl message from an existing message and bypasses
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* the CRC calculation.
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*/
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protected TDULinkControlMessage( TDULinkControlMessage message )
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{
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super( message.getSourceMessage(), DataUnitID.TDULC, message.getAliasList() );
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mCRC = message.getCRC();
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}
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public CRC[] getCRC()
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{
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return mCRC;
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}
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@Override
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public String getMessage()
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{
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StringBuilder sb = new StringBuilder();
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sb.append( getMessageStub() );
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sb.append( " " );
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sb.append( mMessage.toString() );
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return sb.toString();
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}
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public String getMessageStub()
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{
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StringBuilder sb = new StringBuilder();
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sb.append( "NAC:" );
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sb.append( getNAC() );
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sb.append( " " );
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sb.append( getDUID().getLabel() );
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sb.append( " " );
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if( isEncrypted() )
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{
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sb.append( "ENCRYPTED" );
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}
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else
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{
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if( isImplicitFormat() || getVendor() == Vendor.STANDARD )
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{
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sb.append( getOpcode().getLabel() );
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}
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else
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{
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sb.append( "VENDOR:" + getVendor().getLabel() + " " );
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sb.append( getVendorOpcode().getLabel() );
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}
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}
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return sb.toString();
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}
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public boolean isEncrypted()
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{
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return mMessage.get( ENCRYPTION_FLAG );
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}
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public boolean isImplicitFormat()
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{
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return mMessage.get( IMPLICIT_VENDOR_FLAG );
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}
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public LinkControlOpcode getOpcode()
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{
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return LinkControlOpcode.fromValue( mMessage.getInt( OPCODE ) );
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}
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public VendorLinkControlOpcode getVendorOpcode()
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{
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return VendorLinkControlOpcode.fromValue( mMessage.getInt( OPCODE ) );
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}
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public Vendor getVendor()
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{
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if( isImplicitFormat() )
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{
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return Vendor.STANDARD;
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}
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return Vendor.fromValue( mMessage.getInt( VENDOR ) );
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}
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/**
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* Checks and repairs the 12 x 24-bit golay(24,12,8) codewords and then
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* checks and repairs the 24 x 6-bit link control and reed-solomon
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* RS(24,12,13) parity codewords
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*/
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private void checkCRC()
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{
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/* Check the Golay codewords */
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int x = 64;
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mCRC[ 1 ] = CRC.PASSED;
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while( x < mMessage.size() )
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{
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boolean passes = Galois24.checkAndCorrect( mMessage, x );
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if( !passes )
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{
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mCRC[ 1 ] = CRC.FAILED_CRC;
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}
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x += 24;
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}
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/* Check the Reed-Solomon parity bits. The RS decoder expects the link
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* control data and reed solomon parity hex codewords in reverse order.
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* The RS(24,12,13) code used by P25 removes the left-hand 47 data hex
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* words, so we replace them with zeros. */
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int[] input = new int [63];
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int[] output = new int [63];
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input[ 0 ] = mMessage.getInt( RS_HEX_11 );
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input[ 1 ] = mMessage.getInt( RS_HEX_10 );
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input[ 2 ] = mMessage.getInt( RS_HEX_9 );
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input[ 3 ] = mMessage.getInt( RS_HEX_8 );
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input[ 4 ] = mMessage.getInt( RS_HEX_7 );
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input[ 5 ] = mMessage.getInt( RS_HEX_6 );
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input[ 6 ] = mMessage.getInt( RS_HEX_5 );
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input[ 7 ] = mMessage.getInt( RS_HEX_4 );
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input[ 8 ] = mMessage.getInt( RS_HEX_3 );
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input[ 9 ] = mMessage.getInt( RS_HEX_2 );
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input[ 10 ] = mMessage.getInt( RS_HEX_1 );
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input[ 11 ] = mMessage.getInt( RS_HEX_0 );
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input[ 12 ] = mMessage.getInt( LC_HEX_11 );
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input[ 13 ] = mMessage.getInt( LC_HEX_10 );
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input[ 14 ] = mMessage.getInt( LC_HEX_9 );
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input[ 15 ] = mMessage.getInt( LC_HEX_8 );
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input[ 16 ] = mMessage.getInt( LC_HEX_7 );
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input[ 17 ] = mMessage.getInt( LC_HEX_6 );
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input[ 18 ] = mMessage.getInt( LC_HEX_5 );
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input[ 19 ] = mMessage.getInt( LC_HEX_4 );
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input[ 20 ] = mMessage.getInt( LC_HEX_3 );
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input[ 21 ] = mMessage.getInt( LC_HEX_2 );
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input[ 22 ] = mMessage.getInt( LC_HEX_1 );
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input[ 23 ] = mMessage.getInt( LC_HEX_0 );
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/* indexes 24 - 62 are defaulted to zero */
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boolean irrecoverableErrors = mReedSolomonDecoder.decode( input, output );
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if( irrecoverableErrors )
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{
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mCRC[ 2 ] = CRC.FAILED_CRC;
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}
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else
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{
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mCRC[ 2 ] = CRC.PASSED;
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/* Only fix the link control data hex codewords */
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repairHexCodeword( input, output, 12, LC_HEX_11 );
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repairHexCodeword( input, output, 13, LC_HEX_10 );
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repairHexCodeword( input, output, 14, LC_HEX_9 );
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repairHexCodeword( input, output, 15, LC_HEX_8 );
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repairHexCodeword( input, output, 16, LC_HEX_7 );
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repairHexCodeword( input, output, 17, LC_HEX_6 );
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repairHexCodeword( input, output, 18, LC_HEX_5 );
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repairHexCodeword( input, output, 19, LC_HEX_4 );
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repairHexCodeword( input, output, 20, LC_HEX_3 );
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repairHexCodeword( input, output, 21, LC_HEX_2 );
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repairHexCodeword( input, output, 22, LC_HEX_1 );
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repairHexCodeword( input, output, 23, LC_HEX_0 );
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/* If the golay check failed, mark it as corrected too */
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if( mCRC[ 1 ] == CRC.FAILED_CRC )
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{
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mCRC[ 1 ] = CRC.CORRECTED;
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}
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}
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}
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private void repairHexCodeword( int[] input, int[] output, int index, int[] indexSet )
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{
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if( input[ index ] != output[ index ] )
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{
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mMessage.load( indexSet[ 0 ], 6, output[ index ] );
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mCRC[ 2 ] = CRC.CORRECTED;
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}
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}
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/**
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* Indicates if the message passed the golay and reed-solomon parity checks
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* or was corrected.
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*/
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public boolean isValid()
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{
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// mCRC[ 0 ] - always passes (otherwise message wouldn't be constructed )
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// mCRC[ 1 ] - golay - always passes or corrected if mCRC[2] is valid
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return mCRC[ 2 ] == CRC.PASSED || mCRC[ 2 ] == CRC.CORRECTED;
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}
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}
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