====== C language project: Part C1 ======
<fc #FF0000>''WARNING: This information might be out of date. This version is up-to-date for the winter term 2016/2017.''</fc>

The aim of this project is to understand the phases of program creation and compilation in the C language in the POSIX environment and the ''Makefile'' file creation for an automated build of the whole project.

===== Create a library =====
Implement a ''Makefile'' that creates a shared library ''libnsd.so'' from the source codes. [[http://labe.felk.cvut.cz/~stepan/33OSS/files/nsd.c|nsd.c]], [[http://labe.felk.cvut.cz/~stepan/33OSS/files/nsd.h|nsd.h]], [[http://labe.felk.cvut.cz/~stepan/33OSS/files/nd.c|nd.c]] and [[http://labe.felk.cvut.cz/~stepan/33OSS/files/nd.h|nd.h]]. The header files contain definition of the following functions:
  * ''nsd'' -- the greatest common divisor
  * ''nd'' -- the greatest divisor

//Note//: If the previous links do not work, download the files from the [[http://labe.felk.cvut.cz/~stepan/33OSS/semestralky-makefile.html|Czech version]] of the course.
===== Create an application =====
Create a main program that uses the ''libnsd.so'' library. The program reads lines from stdin and interprets each line as two integer numbers (space separated). In case of erroneous input data, the program outputs an usage help onto the standard error output.

If the user entered two primes, output a string ''prime'' (ended by the EOL character). In other cases print the greatest common divisor of both numbers found (a number and an EOL).

The program continues reading (and processing) the stdin until the stdin is closed (an EOF char received). Before the program exits, it prints a ''DONE'' string to stderr.

Create a ''Makefile'' that has at least the following three targets:
  * ''lib'' -- for creation of shared library
  * ''all'' -- for creation of executable application
  * ''clean'' -- for cleaning all generated files


The target ''all'' is the default one (when the ''make'' is invoked with no arguments). Write the makefile so that only changed sources are compiled.


The task is evaluated automatically. You have to stick to the output format and to the makefile targets for the task to be accepted.


Into the [[http://cw.felk.cvut.cz/upload/|Upload System]] upload only a ''zip'' file containing **ONLY** the source files (''.h'' and ''.c'' including the ''nsd.h'', ''nsd.c'', ''nd.h'' and ''nd.c'' files) and the ''Makefile''.

==== Related links ====
[[http://blog.feabhas.com/2014/04/static-and-dynamic-libraries-on-linux/|General information of static and dynamic libraries]]

[[http://www.yolinux.com/TUTORIALS/LibraryArchives-StaticAndDynamic.html|Tutorial on static and dynamic libraries]]

**Hint**: [[http://en.wikipedia.org/wiki/Prime_number|Prime number definition]]


====== C language project: Part C2 ======
===== Process creation in C language =====
This assignment is oriented towards the basic operation related to creating processes in the C language.
===== Specification =====
In the C or C++ language create a program that creates two processes (''fork'' function) and connects them via pipe (the ''pipe'' function).

The first descendant redirects its' stdout into the pipe and writes (space separated) pairs of random numbers into it (function ''rand''). Delay the output of the numbers (i.e. by 1 second). The first descendant has to treat the SIGUSR1 signal (''sigaction'' function) and in case of receiving such signal it prints a string "TERMINATED" to it's stderr and terminates.

The second descendant redirects the pipe output to it's stdin, redirects it's stdout into a file called ''out.txt'' in the current directory and executes a binary file (''execl'' function) for finding the greatest common divisor (the output of ''C1'' task).

The parent process waits 5 seconds and then sends ''SIGUSR1'' to the first process (number generator). This should perform a correct termination of both processes. It waits for the sub-processes to terminate (''wait'' function) and terminates itself.

In fact you are implementing something like this: ''while : ; do echo $RANDOM $RANDOM ; sleep 1; done | ./c1_task > out.txt''

==== Implementation notes ====
  * The pipe has to be created before you create the descendants (in order to connect them both).
  * The parent process does not need the pipe after creating the descendants (and should close it).
  * For stdin/stdout redirection use the ''dup'' function.
  * Any repeated constants must be defined in the top part of the file.
  * Ease your work and move repeated code in a library.

Create a ''Makefile'' that builds a binary application. In case of need the ''Makefile'' must also build the application for computing the greatest common divisor in a separate directory.

==== Evaluation ====
<note important>There is no AutomatedEvaluation script available. The script will be reviewed by your teacher.

Make sure you followed the specification.

Make sure your code works on the computers in the lab.</note>

In case to verify the correct implementation of your task you should((This is a requirement if you want the C2 to be evaluated without physically attending the class. In such case make sure you follow the specification. Usually, many review-request are sent the last day so do not expect the teacher to review your code more than once that day...)) implement the following commandline options (the order is not fixed, may repeat also):
  * ''--seed <num>'' -- a seed for random generator
  * ''--verify'' -- turns on verification of the sequence numbers in the second sub-process
  * ''--error'' -- changes randomly selected numbers in the random sequence of the first sub-process

The parent process should share the seed with both descendants.

Both the sub-processes use the seed for initializing the random sequence((The sequence of pseudo-random numbers would be equal on both sides.)). 

If the ''--seed <num>'' option is not specified, use a random seed. In such case print the 'seed' to the stderr (''Seed: <SEED>'').

If the ''--verify'' option is specified, the second subprocess verifies whether the numbers received from the first sub-process are correct (match the sequence). In case it detects an error it prints a message: ''Error, expected: <ORIGINAL>, received: <RECEIVED>'' to stderr (substituting relevant values). It's wise to implement this in the (modified) program C1.

If the ''--error'' option is specified, the first subprocess randomly replaces some number(s) from the sequence with different numbers. Therefore only a few numbers of the sequence are incorrect. In case of error injection it prints the message ''Modified <ORIGINAL> to <NEW>'' to stderr (substituting relevant values).

Create an application (modify the C1 task program) that can verify the 'out.txt' file: Provided with a seed (as as ''--seed <num>'' parameter) it generates the same sequence of input values and verifies the ''out.txt'' file. Add it as a ''Makefile'' target: ''make test''

====== C language project: Part C3 ======
===== x86 Assembly language within C language =====

<code>
/*
(Please update this header. Not updating it is an act of ignorance.)
Name: John Doe
Course: AE3B33OSD
Semester: Summer term, 2016
Short description: ...

I confess to plagiarism and other sins...

*/
int main() {
   char str[]="XX hex is 150\n";
   unsigned char a=150;

   asm volatile (
      "mov %%eax, %%ebx;"
      "shr $4, %%eax;"
      "and $15, %%eax;"
      "cmpl $9, %%eax;"
      "jg 1f;"
      "add $'0', %%eax;"
      "jmp 2f;"
      "1: add $'A', %%eax;"
      "2: movb %%al, (%%ecx);"
/* Task: Complete the task below:
	1) Understand what the code does
	2) Complete the remaining part
	3) Use syscall WRITE to print out the resulting string (str[])
	4) Write the resulting string (str[]) to a file: 
		4a) Using the open() function
		4b) Using the open() syscall
*/

	/* TODO: Insert your code here... */


      : : "a" (a), "c" (str) : "ebx", "edx");

   return 0;
}
</code>