Chapter 12, Problem 12.25HW

Explanation of Solution

Given C code:

//Include libraries

#include "csapp.h"

#include "sbuf.h"

#include<pthread.h>

#define NTHREADS 4

#define SBUFSIZE 16

//Declare variable

static int byte_cnt;

//Declare variable

static sem_t mutex;

//Define method init_echo_cnt

static void init_echo_cnt(void)

{

//Call method

Sem_init(&mutex, 0, 1);

//Assign value

byte_cnt = 0;

}

//Define method echo_cnt

void echo_cnt(int connfd)

{

//Declare variable

int n;

//Declare array

char buf[MAXLINE];

//Create instance

rio_t rio;

//Assign value

static pthread_once_t once = PTHREAD_ONCE_INIT;

//Call method

pthread_once(&once, init_echo_cnt);

//Call method

Rio_readinitb(&rio, connfd);

//Loop

while((n = Rio_readlineb(&rio, buf, MAXLINE)) != 0)

{

//Decrement

P(&mutex);

//Update value

byte_cnt += n;

//Display message

printf("server received %d (%d total) bytes on fd %d\n", n, byte_cnt, connfd...