task.c

solutions for some problems in Linux

/******************************************************************************
 * task.c
 * This file is part of "Assignment 2: Memory Management" 
 * Copyright (C) 2008 - c506001 (email: [e-mail] )
 *
 * Note:
 * -----
 * These codes are used for reference, but not complete. Students can modified
 * them to satisfy the requirements.
 * 
 * Content:
 * -------- 
 * Implementation of task-related functions
 *
 * System and Networking Department
 * Faculty of Computer Science and Engineering
 * Ho Chi Minh City University of Technology
 ******************************************************************************/

#include <stdlib.h>
#include <string.h>
#include "sys.h"

/**
 * addTask2List: add a task to a list of tasks
 * @taskList: list of tasks
 * @task: task will be added
 * 
 * @return: always 0
 **/
int addTask2List(struct TaskList *taskList, struct Task *task) 
{
	if (taskList->first == NULL) {
		taskList->first = task;
		task->next = task;
		task->prev = task;
	} else {
		struct Task *last = taskList->first->prev;
		last->next = task;
		task->next = taskList->first;
		taskList->first->prev = task;
		task->prev = last;
	}    
	taskList->nTasks++;
	return 0;
}

/**
 * removeTask: remove a task out of list
 * @taskList: list of tasks
 * @task: task will be removed
 * 
 * @return: always 0
 **/
int removeTask(struct TaskList *taskList, struct Task *task)
{
	(task->prev)->next = task->next;
	(task->next)->prev = task->prev;
	taskList->nTasks--;

	if (taskList->nTasks == 0) {
		taskList->first = NULL;
	}
	else if (taskList->first == task) {
		taskList->first = task->next;
	}
	/* free Task */
	free(task);

	return 0;
}

/**
 * getFrameFromMem: from logical address, find the appropriate frame
 * @task: task
 * @memAddr: logical address
 * 
 * @return: a pointer to appropriate page
 **/
struct PageStatus* getFrameFromMem(struct Task *task, int memAddr)
{
	int section;
	int page;
	int pageTblOffset;
	struct PageTable *pageTbl;

	section = (memAddr >> N_OFFSET_BITS);
	page = section & ((1 << N_PAGE_BITS) - 1); // get page number
	section = (section >> N_PAGE_BITS); // get section number
	pageTblOffset = task->sectionTbl->elems[section];
	pageTbl = &(task->pageTbl[pageTblOffset]);
	return &(pageTbl->elems[page]);
}

/**
 * getFrameFromPage: from (section, page), find the appropriate frame
 * @task: task
 * @section: the first 10bit in logical address
 * @page: the next 10bit in logical address
 * 
 * @return: a pointer to appropriate page
 **/
struct PageStatus* getFrameFromPage(struct Task *task, int section, int page)
{
	int pageTblOffset = task->sectionTbl->elems[section];
	struct PageTable *pageTbl = &(task->pageTbl[pageTblOffset]);
	return &(pageTbl->elems[page]);
}

/**
 * updatePage: using a frame for a page
 * @page: page
 * @frame: frame
 * 
 * @return: always 0
 **/
int updatePage(struct PageStatus *page, int frame, int pid, int memAddr, FILE *outFile)
{
//	printf("Updating Page...\n");
	page->frame = frame;
	page->state = VALID;
	/* Do something more if necessary */

	page->lastAccessTime = 1;	// not necessary

	int section;
	int p;
	section = (memAddr >> N_OFFSET_BITS);
	p = section & ((1 << N_PAGE_BITS) - 1); // get page number
	section = (section >> N_PAGE_BITS); // get section number

	fprintf(outFile,"SETVALID %d %d %d %d\n",pid, section, p, frame);

	return 0;
}

/**
 * findUnusedPage: in a task, find the first INVALID page
 * @task: task
 * 
 * @return: the first INVALID page
 **/
struct PageStatus *findUnusedPage(struct Task *task)
{
	struct PageStatus *page = NULL;
	int i = 0;
	int j = 0;

	for (i = 0; i < (1 << N_SECTION_BITS); i++) {
		for (j = 0; j < (1 << N_PAGE_BITS); j++) {
			page = getFrameFromPage(task, i, j);
			if (page->state == INVALID) {
				return page;
			}
		}
	}
	return NULL;
}

/**
 * initTask: initialize values of fields in task
 * @task: task
 **/
int initTask(struct Task *task)
{
	memset(task, 0, sizeof(struct Task));
	return 0;
}