mapreduce.h

// DO NOT modify this file! This is your program's API, which must be held
// constant.
#ifndef MAPREDUCE_H
#define MAPREDUCE_H

// typedefs
typedef void (*Mapper)(char* file_name);
typedef void (*Reducer)(char* key, unsigned int partition_idx);

// library functions that must be implemented

/**
* Run the MapReduce framework
* Parameters:
*     file_count   - Number of files (i.e. input splits)
*     file_names   - Array of filenames
*     mapper       - Function pointer to the map function
*     reducer      - Function pointer to the reduce function
*     num_workers  - Number of threads in the thread pool
*     num_parts    - Number of partitions to be created
*/
void MR_Run(unsigned int file_count, char* file_names[],
            Mapper mapper, Reducer reducer,
            unsigned int num_workers, unsigned int num_parts);

/**
* Write a specific map output, a <key, value> pair, to a partition
* Parameters:
*     key           - Key of the output
*     value         - Value of the output
*/
void MR_Emit(char* key, char* value);

/**
* Hash a mapper's output to determine the partition that will hold it
* Parameters:
*     key           - Key of a specific map output
*     num_partitions- Total number of partitions
* Return:
*     unsigned int  - Index of the partition
*/
unsigned int MR_Partitioner(char* key, unsigned int num_partitions);

/**
* Run the reducer callback function for each <key, (list of values)>
* retrieved from a partition
* Parameters:
*     threadarg     - Pointer to a hidden args object
*/
void MR_Reduce(void* threadarg);

/**
* Get the next value of the given key in the partition
* Parameters:
*     key           - Key of the values being reduced
*     partition_idx - Index of the partition containing this key
* Return:
*     char *        - Value of the next <key, value> pair if its key is the current key
*     NULL          - Otherwise
*/
char* MR_GetNext(char* key, unsigned int partition_idx);

#endif