62 lines
1.6 KiB
Java
62 lines
1.6 KiB
Java
package btools.util;
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public final class ByteArrayUnifier implements IByteArrayUnifier
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{
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private byte[][] byteArrayCache;
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private int[] crcCrosscheck;
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private int size;
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public ByteArrayUnifier( int size, boolean validateImmutability )
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{
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this.size = size;
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byteArrayCache = new byte[size][];
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if ( validateImmutability ) crcCrosscheck = new int[size];
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}
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/**
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* Unify a byte array in order to reuse instances when possible.
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* The byte arrays are assumed to be treated as immutable,
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* allowing the reuse
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* @param ab the byte array to unify
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* @return the cached instance or the input instanced if not cached
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*/
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public byte[] unify( byte[] ab )
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{
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return unify( ab, 0, ab.length );
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}
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public byte[] unify( byte[] ab, int offset, int len )
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{
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int crc = Crc32.crc( ab, offset, len );
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int idx = ( crc & 0xfffffff ) % size;
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byte[] abc = byteArrayCache[idx];
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if ( abc != null && abc.length == len )
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{
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int i = 0;
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while (i < len)
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{
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if ( ab[offset + i] != abc[i] )
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break;
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i++;
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}
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if ( i == len )
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return abc;
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}
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if ( crcCrosscheck != null )
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{
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if ( byteArrayCache[idx] != null )
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{
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byte[] abold = byteArrayCache[idx];
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int crcold = Crc32.crc( abold, 0, abold.length );
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if ( crcold != crcCrosscheck[idx] )
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throw new IllegalArgumentException( "ByteArrayUnifier: immutablity validation failed!" );
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}
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crcCrosscheck[idx] = crc;
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}
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byte[] nab = new byte[len];
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System.arraycopy( ab, offset, nab, 0, len );
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byteArrayCache[idx] = nab;
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return nab;
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}
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}
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