Computer Systems: A Programmer's Perspective Plus Mastering Engineering With Pearson Etext -- Access Card Package (3rd Edition)
Computer Systems: A Programmer's Perspective Plus Mastering Engineering With Pearson Etext -- Access Card Package (3rd Edition)
3rd Edition
ISBN: 9780134123837
Author: Randal E. Bryant, David R. O'Hallaron
Publisher: PEARSON
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Chapter 12, Problem 12.38HW

Explanation of Solution

Implementation of a concurrent prethreaded version of the TINY web server:

Modified code for “sbuf.h” file:

The modified code for “sbuf.h” from section 12.5.4 in book is given below:

#ifndef SBUF_HEADER

#define SBUF_HEADER

#include "csapp.h"

typedef struct

{

int *buf;          /* Buffer array */

int n;             /* Maximum number of slots */

int front;         /* buf[(front+1)%n] is first item */

int rear;          /* buf[rear%n] is last item */

sem_t mutex;       /* Protects accesses to buf */

sem_t slots;       /* Counts available slots */

sem_t items;       /* Counts available items */

} sbuf_t;

//Function declaration

void sbuf_init(sbuf_t *sp, int n);

void sbuf_deinit(sbuf_t *sp);

void sbuf_insert(sbuf_t *sp, int item);

int sbuf_remove(sbuf_t *sp);

//Function declaration for sbuf_empty

int sbuf_empty(sbuf_t *sp);

//Function declaration for sbuf_full

int sbuf_full(sbuf_t *sp);

#endif

Modified code for “sbuf.c” file:

The modified code for “sbuf.c” from section 12.5.4 in book is given below:

#include "csapp.h"

#include "sbuf.h"

/* Create an empty, bounded, shared FIFO buffer with n slots */

void sbuf_init(sbuf_t *sp, int n)

{

  sp->buf = Calloc(n, sizeof(int));

  sp->n = n;                       /* Buffer holds max of n items */

  sp->front = sp->rear = 0;        /* Empty buffer if front == rear */

  Sem_init(&sp->mutex, 0, 1);      /* Binary semaphore for locking */

  Sem_init(&sp->slots, 0, n);      /* Initially, buf has n empty slots */

  Sem_init(&sp->items, 0, 0);      /* Initially, buf has zero data items */

}

/* Clean up buffer sp */

void sbuf_deinit(sbuf_t *sp)

{

  Free(sp->buf);

}

/* Insert item onto the rear of shared buffer sp */

void sbuf_insert(sbuf_t *sp, int item)

{

  P(&sp->slots);                          /* Wait for available slot */

  P(&sp->mutex);                          /* Lock the buffer */

  sp->buf[(++sp->rear)%(sp->n)] = item;   /* Insert the item */

  V(&sp->mutex);                          /* Unlock the buffer */

  V(&sp->items);                          /* Announce available item */

}

/* Remove and return the first item from buffer sp */

int sbuf_remove(sbuf_t *sp)

{

int item;

  P(&sp->items);                          /* Wait for available item */

  P(&sp->mutex);                          /* Lock the buffer */

  item = sp->buf[(++sp->front)%(sp->n)];  /* Remove the item */

  V(&sp->mutex);                          /* Unlock the buffer */

  V(&sp->slots);                          /* Announce available slot */

return item;

}

//Function definition for empty buffer

int sbuf_empty(sbuf_t *sp)

{

//Declare variable

int ne;

//For lock the buffer

  P(&sp->mutex);                        

  ne = sp->front == sp->rear;

//For lock the buffer

  V(&sp->mutex);                         

return ne;

}

//Function definition for full buffer

int sbuf_full(sbuf_t *sp)

{

//Declare variable

int fn;

//For lock the buffer

  P(&sp->mutex);                        

  fn = (sp->rear - sp->front) == sp->n;

//For lock the buffer

  V(&sp->mutex);                        

return fn;

}

For code “tiny.c” and “tiny.h”:

Same code as section 11.6 in book.

sample.html:

<!DOCTYPE html>

<html>

<head>

<meta charset="utf-8" />

<title>Home</title>

</head>

<body>

Tiny server Example

</body>

</html>

main.c:

#include <stdio.h>

#include "csapp.h"

#include "tiny.h"

#include "sbuf...

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