gistfile1.c

#define _XOPEN_SOURCE 600

#include <ucontext.h>
#include <stdlib.h>

/*** Globals ***/
#define THREAD_ARRAY_SIZE 100

static int max_klt;
static int current_klt;
static ucontext_t* ctx[THREAD_ARRAY_SIZE];
static int pos;
static int running_pos;


/*** Functions ***/
void system_init(int max_number_of_klt){
	max_klt = max_number_of_klt;
	current_klt = 0;
	pos = 0;
	running_pos = -1;
}

int uthread_create(void func()){
	if(pos < THREAD_ARRAY_SIZE){
		ctx[pos] = malloc(sizeof(ucontext_t));
		getcontext(ctx[pos]);
		//Allocate memory for the context stack
		ctx[pos]->uc_stack.ss_sp = malloc(16384);
		ctx[pos]->uc_stack.ss_size = 16384;
		makecontext(ctx[pos], func, 0);
		pos++;
		if(current_klt < max_klt){
			void *child_stack;
			child_stack = (void *)malloc(16384);
			clone(func, child_stack, 0, NULL);
			running_pos = -1;
			current_klt++;
		}
		return 0;
	}
	return -1;
}

int uthread_yield(){
	if(running_pos >= 0 && running_pos < pos){
		setcontext(ctx[running_pos + 1]);
		running_pos++;
		return 0;
	}
	return -1;
}

void uthread_exit(){
	if(running_pos >= 0 && running_pos < pos){
		setcontext(ctx[running_pos + 1]);
		running_pos++;
	}
	else{
		exit(running_pos);
	}
}