Concept explainers
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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Chapter 12 Solutions
Computer Systems: A Programmer's Perspective (3rd Edition)
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