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 * ________________________________________________________________
 * National Laboratory for Applied Network Research 
 * National Center for Supercomputing Applications 
 * University of Illinois at Urbana-Champaign 
 * http://www.ncsa.uiuc.edu
 * ________________________________________________________________ 
 * Extractor.cpp
 * by Ajay Tirumala (tirumala@ncsa.uiuc.edu)
 * -------------------------------------------------------------------
 * Extract data from a file, used to measure the transfer rates
 * for various stream formats. 
 *
 * E.g. Use a gzipped file to measure the transfer rates for 
 * compressed data
 * Use an MPEG file to measure the transfer rates of 
 * Multimedia data formats
 * Use a plain BMP file to measure the transfer rates of 
 * Uncompressed data
 *
 * This is beneficial especially in measuring bandwidth across WAN
 * links where data compression takes place before data transmission 
 * ------------------------------------------------------------------- 
 */

#include "Extractor.hpp"


/**
 * Constructor
 * @arg fileName   Name of the file 
 * @arg size       Block size for reading
 * Open the file and set the block size
 */
Extractor::Extractor(char *fileName, int inSize) {

    if ( (in = fopen (fileName, "rb")) == NULL ) {
        printf("Unable to open the file stream\n");
        printf("Will use the default data stream\n");
        return;
    }
    size =  inSize;
}


/**
 * Constructor
 * @arg fp         File Pointer 
 * @arg size       Block size for reading
 * Set the block size,file pointer
 */
Extractor::Extractor(FILE *fp, int inSize) {
    in = fp;
    size =  inSize;
}


/**
 * Destructor - Close the file
 */
Extractor::~Extractor() {
    if ( in != NULL )
        fclose(in);
}


/*
 * Fetches the next data block from 
 * the file
 * @arg block     Pointer to the data read
 * @return        Number of bytes read
 */
int Extractor::getNextDataBlock(char *data) {
    if ( canRead() ) {
        return(fread(data, 1, size, in));
    }
    return 0;
}

/**
 * Function which determines whether
 * the file stream is still readable
 * @return boolean    true, if readable; false, if not
 */
bool Extractor::canRead() {
    return((in != NULL) && !(feof(in)));
}

/**
 * This is used to reduce the read size
 * Used in UDP transfer to accomodate the
 * the header (timestamp)
 * @arg delta         Size to reduce
 */
void Extractor::reduceReadSize(int delta) {
    size -= delta;
}



















































