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Pipes.hh
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/**
* 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.
*/
#ifndef HADOOP_PIPES_HH
#define HADOOP_PIPES_HH
#ifdef SWIG
%module (directors="1") HadoopPipes
%include "std_string.i"
%feature("director") Mapper;
%feature("director") Reducer;
%feature("director") Partitioner;
%feature("director") RecordReader;
%feature("director") RecordWriter;
%feature("director") Factory;
#else
#include <string>
#endif
#include <stdint.h>
namespace HadoopPipes {
/**
* This interface defines the interface between application code and the
* foreign code interface to Hadoop Map/Reduce.
*/
/**
* A JobConf defines the properties for a job.
*/
class JobConf {
public:
virtual bool hasKey(const std::string& key) const = 0;
virtual const std::string& get(const std::string& key) const = 0;
virtual int getInt(const std::string& key) const = 0;
virtual float getFloat(const std::string& key) const = 0;
virtual bool getBoolean(const std::string&key) const = 0;
virtual ~JobConf() {}
};
/**
* Task context provides the information about the task and job.
*/
class TaskContext {
public:
/**
* Counter to keep track of a property and its value.
*/
class Counter {
private:
int id;
public:
Counter(int counterId) : id(counterId) {}
Counter(const Counter& counter) : id(counter.id) {}
int getId() const { return id; }
};
/**
* Get the JobConf for the current task.
*/
virtual const JobConf* getJobConf() = 0;
/**
* Get the current key.
* @return the current key
*/
virtual const std::string& getInputKey() = 0;
/**
* Get the current value.
* @return the current value
*/
virtual const std::string& getInputValue() = 0;
/**
* Generate an output record
*/
virtual void emit(const std::string& key, const std::string& value) = 0;
/**
* Mark your task as having made progress without changing the status
* message.
*/
virtual void progress() = 0;
/**
* Set the status message and call progress.
*/
virtual void setStatus(const std::string& status) = 0;
/**
* Register a counter with the given group and name.
*/
virtual Counter*
getCounter(const std::string& group, const std::string& name) = 0;
/**
* Increment the value of the counter with the given amount.
*/
virtual void incrementCounter(const Counter* counter, uint64_t amount) = 0;
virtual ~TaskContext() {}
};
class MapContext: public TaskContext {
public:
/**
* Access the InputSplit of the mapper.
*/
virtual const std::string& getInputSplit() = 0;
/**
* Get the name of the key class of the input to this task.
*/
virtual const std::string& getInputKeyClass() = 0;
/**
* Get the name of the value class of the input to this task.
*/
virtual const std::string& getInputValueClass() = 0;
};
class ReduceContext: public TaskContext {
public:
/**
* Advance to the next value.
*/
virtual bool nextValue() = 0;
};
class Closable {
public:
virtual void close() {}
virtual ~Closable() {}
};
/**
* The application's mapper class to do map.
*/
class Mapper: public Closable {
public:
virtual void map(MapContext& context) = 0;
};
/**
* The application's reducer class to do reduce.
*/
class Reducer: public Closable {
public:
virtual void reduce(ReduceContext& context) = 0;
};
/**
* User code to decide where each key should be sent.
*/
class Partitioner {
public:
virtual int partition(const std::string& key, int numOfReduces) = 0;
virtual ~Partitioner() {}
};
/**
* For applications that want to read the input directly for the map function
* they can define RecordReaders in C++.
*/
class RecordReader: public Closable {
public:
virtual bool next(std::string& key, std::string& value) = 0;
/**
* The progress of the record reader through the split as a value between
* 0.0 and 1.0.
*/
virtual float getProgress() = 0;
};
/**
* An object to write key/value pairs as they are emited from the reduce.
*/
class RecordWriter: public Closable {
public:
virtual void emit(const std::string& key,
const std::string& value) = 0;
};
/**
* A factory to create the necessary application objects.
*/
class Factory {
public:
virtual Mapper* createMapper(MapContext& context) const = 0;
virtual Reducer* createReducer(ReduceContext& context) const = 0;
/**
* Create a combiner, if this application has one.
* @return the new combiner or NULL, if one is not needed
*/
virtual Reducer* createCombiner(MapContext& context) const {
return NULL;
}
/**
* Create an application partitioner object.
* @return the new partitioner or NULL, if the default partitioner should be
* used.
*/
virtual Partitioner* createPartitioner(MapContext& context) const {
return NULL;
}
/**
* Create an application record reader.
* @return the new RecordReader or NULL, if the Java RecordReader should be
* used.
*/
virtual RecordReader* createRecordReader(MapContext& context) const {
return NULL;
}
/**
* Create an application record writer.
* @return the new RecordWriter or NULL, if the Java RecordWriter should be
* used.
*/
virtual RecordWriter* createRecordWriter(ReduceContext& context) const {
return NULL;
}
virtual ~Factory() {}
};
/**
* Run the assigned task in the framework.
* The user's main function should set the various functions using the
* set* functions above and then call this.
* @return true, if the task succeeded.
*/
bool runTask(const Factory& factory);
}
#endif

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