spigotcpp/Spigot.cpp

#include <iostream>
#include <cmath>
#include <cassert>
#include "Spigot.hpp"

Spigot::Spigot(int requestedNumDigits) {
    /* create list for number of digits times 10 / 3 */
    this->spigotListLength = (requestedNumDigits * 10) / 3;
    this->spigotList.resize(this->spigotListLength, 2); // list is initialized with all 2
    this->carry = 0;
    return;
}

void Spigot::pump(void) {
    int tempPreDigit = 0;
    int j = this->spigotListLength - 1;
    int i = j;

    /*
     * This could be handled using boost::compute
     * with a BOOST_COMPUTE_FUNCTION that just
     * multiplies every item by 10.
     */
    while(i >= 0) {
        this->spigotList[i] *= 10;
        i--;
    }
    this->carry = 0;
    i = j;
    // note this does *not* handle the i=0 case
    /*
     * This might also be able to be sped up
     * with OpenCL/boost::compute by creating
     * another custom function, but because
     * the carry has to be passed along this might
     * not work well
     */
    while(i > 0) {
        this->spigotList[i] += this->carry;
        this->carry = (this->spigotList[i] / (i * 2 + 1)) * i;
        this->spigotList[i] = this->spigotList[i] % (i * 2 + 1);
        i--;
    }
    // special case of i = 0
    this->spigotList[0] += this->carry;
    tempPreDigit = this->spigotList[0] / 10;
    this->spigotList[0] -= (tempPreDigit * 10);

    try {
        // handle the cases depending on the tempPreDigit
        if(tempPreDigit >= 0 && tempPreDigit <= 8) {
            // output all predigits
            long unsigned pdLen = this->preDigits.size();
            for(long unsigned int j = 0; j < pdLen; j++) {
                std::cout << this->preDigits.back();
                this->preDigits.pop_back();
            }
            this->preDigits.insert(this->preDigits.begin(), tempPreDigit);

        } else if(tempPreDigit == 9) {
            this->preDigits.insert(this->preDigits.begin(), tempPreDigit);
        } else if(tempPreDigit == 10) {
            tempPreDigit = 0;
            long unsigned pdLen = this->preDigits.size();
            for(long unsigned int j = 0; j < pdLen; j++) {
                std::cout << (this->preDigits.back() + 1) % 10;
                this->preDigits.pop_back();
            }
            this->preDigits.insert(this->preDigits.begin(), tempPreDigit);
        } else {
            std::cout << "We should never have gotten here -- shit has hit the fan!" << std::endl;
        }
    } catch (int e) {
        std::cout << "An exception " << e << " occurred." << std::endl;
    }
    std::cout << std::flush;
    return;
}