add sort interface (#19)

* first version of sorter

* add sort interface

* remove first version of sorter

computer-core/src/main/java/com/baidu/hugegraph/computer/core/store/HgkvFile.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2017 HugeGraph Authors
+ *
+ * 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 com.baidu.hugegraph.computer.core.store;
+
+public interface HgkvFile {
+
+    /**
+     * The absolute path includes file name.
+     */
+    String path();
+
+    /**
+     * Return the count of entries.
+     */
+    long entries();
+
+    /**
+     * Return the version of file.
+     */
+    int version();
+}

computer-core/src/main/java/com/baidu/hugegraph/computer/core/store/KvEntry.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2017 HugeGraph Authors
+ *
+ * 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 com.baidu.hugegraph.computer.core.store;
+
+import java.util.Iterator;
+
+public interface KvEntry {
+
+    Pointer key();
+
+    /**
+     * Each pointer in iteration is values for a specific key. It mean's
+     * key's value in a file. It may be several fragments for a key in a file.
+     * The values in fragments are at increasing order. The upper layer read
+     * a fragment from a pointer each time.
+     */
+    Iterator<Pointer> values();
+}

computer-core/src/main/java/com/baidu/hugegraph/computer/core/store/Pointer.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2017 HugeGraph Authors
+ *
+ * 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 com.baidu.hugegraph.computer.core.store;
+
+import com.baidu.hugegraph.computer.core.io.RandomAccessInput;
+
+public interface Pointer extends Range {
+
+    RandomAccessInput input();
+}

computer-core/src/main/java/com/baidu/hugegraph/computer/core/store/Range.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2017 HugeGraph Authors
+ *
+ * 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 com.baidu.hugegraph.computer.core.store;
+
+public interface Range {
+
+    long offset();
+
+    long length();
+}

computer-core/src/main/java/com/baidu/hugegraph/computer/core/store/SortCombiner.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2017 HugeGraph Authors
+ *
+ * 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 com.baidu.hugegraph.computer.core.store;
+
+import java.util.List;
+
+import com.baidu.hugegraph.computer.core.io.RandomAccessOutput;
+
+public interface SortCombiner {
+
+    /**
+     * Combine the list of inputs, and write the combined result length and
+     * results to output.
+     */
+    void combine(List<Pointer> inputs, RandomAccessOutput output);
+}

computer-core/src/main/java/com/baidu/hugegraph/computer/core/store/Sorter.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2017 HugeGraph Authors
+ *
+ * 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 com.baidu.hugegraph.computer.core.store;
+
+import java.util.Iterator;
+import java.util.List;
+
+import com.baidu.hugegraph.computer.core.io.RandomAccessInput;
+import com.baidu.hugegraph.computer.core.io.RandomAccessOutput;
+
+public interface Sorter {
+
+    /**
+     * Sort the buffer by increasing order of key. Every key exists only once
+     * in output buffer.
+     * The input buffer format:
+     * | key1 length | key1 | value1 length | value1 |
+     * | key2 length | key2 | value2 length | value2 |
+     * | key1 length | key1 | value3 length | value3 |
+     * and so on.
+     * If a same key exists several time, combine the values.
+     * @param input The input buffer.
+     * @param valueCombiner The combiner for the same key.
+     * @param output The output after sort the buffer by increasing order of
+     *               the key.
+     */
+    void sortBuffer(RandomAccessInput input,
+                    SortCombiner valueCombiner,
+                    RandomAccessOutput output);
+
+    /**
+     * Merge the buffers by increasing order of key.
+     * The input buffers in list are in increasing order of the key.
+     * The input buffer format:
+     * | key1 length | key1 | value1 length | value1 |
+     * | key2 length | key2 | value2 length | value2 |
+     * and so on.
+     * @param inputBuffers The input buffer list.
+     * @param valueCombiner The combiner for the same key.
+     * @return HgkvFile after merge.
+     */
+     void mergeBuffers(List<RandomAccessInput> inputBuffers,
+                       SortCombiner valueCombiner,
+                       HgkvFile file);
+
+    /**
+     * Merge the n inputs into m outputs.
+     * 'n' is size of inputs, 'm' is size of outputs.
+     * The input files in list are in increasing order of the key.
+     * The input file format:
+     * | key1 length | key1 | value1 length | value1
+     * | key2 length | key2 | value2 length | value2 |
+     * and so on.
+     * The format of outputs is same as inputs.
+     * For example number of the inputs is 100, and m is 10, this method
+     * merge 100 inputs into 10 outputs.
+     * The outputs need to be as evenly distributed as possible. It might
+     * need to sort the inputs by desc order. Then select the inputs one by
+     * one assign to the output with least inputs. It makes the difference
+     * between the outputs below the least inputs.
+     * @return The outputs merged.
+     */
+    void mergeInputs(List<HgkvFile> inputs,
+                     SortCombiner valueCombiner,
+                     List<HgkvFile> outputs);
+
+    /**
+     * Get the iterator of <key, value> pair by increasing order of key.
+     */
+    Iterator<KvEntry> iterator(List<HgkvFile> inputs);
+}