49 lines
916 B
Java
49 lines
916 B
Java
/**
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* DataInputStream extended by varlength diff coding
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*
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* @author ab
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*/
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package btools.util;
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import java.io.DataInputStream;
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import java.io.IOException;
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import java.io.InputStream;
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public final class DiffCoderDataInputStream extends DataInputStream
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{
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private long[] lastValues = new long[10];
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public DiffCoderDataInputStream( InputStream is )
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{
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super( is );
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}
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public long readDiffed( int idx ) throws IOException
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{
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long d = readSigned();
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long v = lastValues[idx] + d;
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lastValues[idx] = v;
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return v;
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}
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public long readSigned() throws IOException
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{
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long v = readUnsigned();
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return ( v & 1 ) == 0 ? v >> 1 : -(v >> 1 );
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}
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public long readUnsigned() throws IOException
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{
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long v = 0;
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int shift = 0;
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for(;;)
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{
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long i7 = readByte() & 0xff;
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v |= (( i7 & 0x7f ) << shift);
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if ( ( i7 & 0x80 ) == 0 ) break;
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shift += 7;
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}
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return v;
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}
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}
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