57 lines
1.1 KiB
Java
57 lines
1.1 KiB
Java
/**
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* DataInputStream for decoding fast-compact encoded number sequences
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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 MixCoderDataInputStream extends DataInputStream
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{
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private long lastValue;
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private long repCount;
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public MixCoderDataInputStream( InputStream is )
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{
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super( is );
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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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public long readMixed() throws IOException
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{
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if ( repCount == 0 )
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{
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long b = readByte() & 0xff;
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long repCode = b >> 6;
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long diffcode = b & 0x3f;
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repCount = repCode == 0 ? readUnsigned() : repCode;
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lastValue += diffcode == 0 ? readSigned() : diffcode - 32;
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}
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repCount--;
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return lastValue;
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}
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}
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