/**

  * LPT signal generator

  * Copyright © 2017 František Kučera (frantovo.cz)

  *

  * This program is free software: you can redistribute it and/or modify

  * it under the terms of the GNU General Public License as published by

  * the Free Software Foundation, either version 3 of the License, or

  * (at your option) any later version.

  *

  * This program is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

  * GNU General Public License for more details.

  *

  * You should have received a copy of the GNU General Public License

  * along with this program. If not, see <http://www.gnu.org/licenses/>.

  */

 #include <stdlib.h>

 #include <iostream>

 #include <stdio.h>

 #include <math.h>

 #include <sys/io.h>

 #include <unistd.h>

 /**

  * can not mix printf and wprintf

  * see https://stackoverflow.com/questions/8681623/printf-and-wprintf-in-single-c-code

  * > This is to be expected; your code is invoking undefined behavior.

  * > Per the C standard, each FILE stream has associated with it an "orientation" (either "byte" or "wide)

  * > which is set by the first operation performed on it, and which can be inspected with the fwide function.

  * > Calling any function whose orientation conflicts with the orientation of the stream results in undefined behavior.

  */

 #include <wchar.h>

 #include <locale.h>

 using namespace std;

 // run this program: g++ lpt.cpp && time chrt 1 ./a.out

 // depending to frequency and machine performance the total time will be more than given duration

 // despite the real-time priority, because some additional time is spent in outb() functions

 // so "duration" means total sleep time

 int main() {

   //cout << "LPT!" << endl; // same as using printf → breaks all folllowing wprintf() calls, see note above

   /*

    * if setlocale() is missing, unicode characters are replaced with ? or „→“ with „->“ because C/POSIX locale is used, 

    * see man setlocale:

    * > On startup of the main program, the portable "C" locale is selected as default.

    * > If locale is an empty string, "", each part of the locale that should be modified is set according to the environment variables.

    */

   setlocale(LC_ALL,"");

   int addr = 0xe400; // parallel port address; first number of given port in: cat /proc/ioports | grep parport

   int baseFreq = 10000; // base frequency in Hz, should be between 5 000 between 10 000 Hz; lower frequency leads to dashed/dotted lines instead of greyscale

   int outputPower = 10; // duty cycle; 100 = 100 %

   int duration = 5; // in seconds; total sleep time, see note above

   int valueWidth =  10; // just for padding of printed values

   int labelWidth = -15; // just for padding of printed labels

   // ' = thousand separator

   // * = padding

   wprintf(L"%*ls %*x\n",     labelWidth, L"Parallel port:", valueWidth, addr); // or %#*x – adds 0x prefix

   wprintf(L"%*ls %'*d Hz\n", labelWidth, L"Base frequency:", valueWidth, baseFreq);

   wprintf(L"%*ls %*d %%\n",  labelWidth, L"Output power:", valueWidth, outputPower);

   wprintf(L"%*ls %'*d s\n",  labelWidth, L"Duration:", valueWidth, duration);

   // in microseconds:

   int oneSecond = 1000 * 1000;

   int timeOn =  oneSecond *        outputPower  / 100 / baseFreq;

   int timeOff = oneSecond * (100 - outputPower) / 100 / baseFreq;

   int cycleCount = duration * baseFreq;

   wprintf(L"%*ls %'*d ×\n", labelWidth, L"Cycle count:", valueWidth, cycleCount);

   wprintf(L"%*ls %'*d μs in each cycle\n", labelWidth, L"Time on:",  valueWidth, timeOn);

   wprintf(L"%*ls %'*d μs in each cycle\n", labelWidth, L"Time off:", valueWidth, timeOff);

   wprintf(L"%*ls %*ls\n", labelWidth, L"unicode test:", valueWidth, L"čeština → …");

   if (ioperm(addr,1,1)) { fwprintf(stderr, L"Access denied to port %#x\n", addr), exit(1); }

   outb(0b00000000, addr);

   for (int i = 0; i < cycleCount; i++) {

     outb(0b00000001, addr);

     usleep(timeOn);

     outb(0b00000000, addr);

     usleep(timeOff);

   }

   wprintf(L"finished\n");

 }