| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.lucene.util.fst; |
| |
| |
| import java.io.IOException; |
| |
| import org.apache.lucene.store.DataInput; |
| import org.apache.lucene.store.DataOutput; |
| import org.apache.lucene.util.BytesRef; |
| import org.apache.lucene.util.RamUsageEstimator; |
| import org.apache.lucene.util.StringHelper; |
| |
| /** |
| * An FST {@link Outputs} implementation where each output |
| * is a sequence of bytes. |
| * |
| * @lucene.experimental |
| */ |
| |
| public final class ByteSequenceOutputs extends Outputs<BytesRef> { |
| |
| private final static BytesRef NO_OUTPUT = new BytesRef(); |
| private final static ByteSequenceOutputs singleton = new ByteSequenceOutputs(); |
| |
| private ByteSequenceOutputs() { |
| } |
| |
| public static ByteSequenceOutputs getSingleton() { |
| return singleton; |
| } |
| |
| @Override |
| public BytesRef common(BytesRef output1, BytesRef output2) { |
| assert output1 != null; |
| assert output2 != null; |
| |
| int pos1 = output1.offset; |
| int pos2 = output2.offset; |
| int stopAt1 = pos1 + Math.min(output1.length, output2.length); |
| while(pos1 < stopAt1) { |
| if (output1.bytes[pos1] != output2.bytes[pos2]) { |
| break; |
| } |
| pos1++; |
| pos2++; |
| } |
| |
| if (pos1 == output1.offset) { |
| // no common prefix |
| return NO_OUTPUT; |
| } else if (pos1 == output1.offset + output1.length) { |
| // output1 is a prefix of output2 |
| return output1; |
| } else if (pos2 == output2.offset + output2.length) { |
| // output2 is a prefix of output1 |
| return output2; |
| } else { |
| return new BytesRef(output1.bytes, output1.offset, pos1-output1.offset); |
| } |
| } |
| |
| @Override |
| public BytesRef subtract(BytesRef output, BytesRef inc) { |
| assert output != null; |
| assert inc != null; |
| if (inc == NO_OUTPUT) { |
| // no prefix removed |
| return output; |
| } else { |
| assert StringHelper.startsWith(output, inc); |
| if (inc.length == output.length) { |
| // entire output removed |
| return NO_OUTPUT; |
| } else { |
| assert inc.length < output.length: "inc.length=" + inc.length + " vs output.length=" + output.length; |
| assert inc.length > 0; |
| return new BytesRef(output.bytes, output.offset + inc.length, output.length-inc.length); |
| } |
| } |
| } |
| |
| @Override |
| public BytesRef add(BytesRef prefix, BytesRef output) { |
| assert prefix != null; |
| assert output != null; |
| if (prefix == NO_OUTPUT) { |
| return output; |
| } else if (output == NO_OUTPUT) { |
| return prefix; |
| } else { |
| assert prefix.length > 0; |
| assert output.length > 0; |
| BytesRef result = new BytesRef(prefix.length + output.length); |
| System.arraycopy(prefix.bytes, prefix.offset, result.bytes, 0, prefix.length); |
| System.arraycopy(output.bytes, output.offset, result.bytes, prefix.length, output.length); |
| result.length = prefix.length + output.length; |
| return result; |
| } |
| } |
| |
| @Override |
| public void write(BytesRef prefix, DataOutput out) throws IOException { |
| assert prefix != null; |
| out.writeVInt(prefix.length); |
| out.writeBytes(prefix.bytes, prefix.offset, prefix.length); |
| } |
| |
| @Override |
| public BytesRef read(DataInput in) throws IOException { |
| final int len = in.readVInt(); |
| if (len == 0) { |
| return NO_OUTPUT; |
| } else { |
| final BytesRef output = new BytesRef(len); |
| in.readBytes(output.bytes, 0, len); |
| output.length = len; |
| return output; |
| } |
| } |
| |
| @Override |
| public void skipOutput(DataInput in) throws IOException { |
| final int len = in.readVInt(); |
| if (len != 0) { |
| in.skipBytes(len); |
| } |
| } |
| |
| @Override |
| public BytesRef getNoOutput() { |
| return NO_OUTPUT; |
| } |
| |
| @Override |
| public String outputToString(BytesRef output) { |
| return output.toString(); |
| } |
| |
| private static final long BASE_NUM_BYTES = RamUsageEstimator.shallowSizeOf(NO_OUTPUT); |
| |
| @Override |
| public long ramBytesUsed(BytesRef output) { |
| return BASE_NUM_BYTES + RamUsageEstimator.sizeOf(output.bytes); |
| } |
| |
| @Override |
| public String toString() { |
| return "ByteSequenceOutputs"; |
| } |
| } |