proj2.c

//Fork, setup shared buffer, signals to notify of buffer activity. When everything is finished, main process outputs table, child exits.
#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <sys/ipc.h>
#include <sys/signal.h>
#include <sys/wait.h>
#include <unistd.h>

#define PROD_SEM 0
#define CONS_SEM 1

#define PROD_SIG (SIGUSR1)
#define CONS_SIG (SIGUSR2)

static char *buffer_base;
static char *buffer;
static char *progress_buffer = NULL;
static char *progress_cursor = NULL;
static key_t semaphore;
static pid_t cons_pid = 0, prod_pid = 0, parent_pid = 0;
static size_t iFileLen = 0;

int sem_up(int idx) {
    struct sembuf op;
    op.sem_num = idx;
    op.sem_op = 1;
    op.sem_flg = 0;

    return semop(semaphore, &op, 1);
}

int sem_down(int idx) {
    struct sembuf op;
    op.sem_num = idx;
    op.sem_op = -1;
    op.sem_flg = 0;

    return semop(semaphore, &op, 1);
}

void producer_signal(int sig) {
    *(progress_cursor++) = 'P';
}

void consumer_signal(int sig) {
    *(progress_cursor++) = 'C';
}

int producer_proc(FILE *iFile){

    for(size_t i = 0; i < iFileLen; i++) {
        char nChar = 0;
        fread(&nChar, 1, 1, iFile);
	
	usleep((rand() % 3 + 1) * 100000);

        sem_down(CONS_SEM);
        //Submit the character
        *(buffer++) = nChar;
        sem_up(PROD_SEM);
        kill(parent_pid, SIGUSR1);
    }

    fclose(iFile);
    return 0;
}

int consumer_proc(FILE *oFile){
    for(size_t i = 0; i < iFileLen; i++) {

	usleep((rand() % 3 + 1) * 100000);

	sem_down(PROD_SEM);
        char nChar = *(buffer++);
        sem_up(CONS_SEM);
        kill(parent_pid, SIGUSR2);

        fwrite(&nChar, 1, 1, oFile);
    }

    fclose(oFile);
    return 0;
}


int main(int argc, char *argv[]) {

    bool showHelp = false;

    if(argc != 3) 
        showHelp = true;

    if(argc > 1 && strcmp(argv[1], "-h") == 0)
        showHelp = true;

    if(!showHelp) {

        FILE *iFile = fopen(argv[1], "rb");
        FILE *oFile = fopen(argv[2], "wb");

        fseek(iFile, 0, SEEK_END);
        iFileLen = ftell(iFile);
        fseek(iFile, 0, SEEK_SET);


        if(iFile == NULL)
        {
            printf("Failed to open input file.\n");
            return 0;
        }
        
        if(oFile == NULL)
        {
            printf("Failed to open output file.\n");
            return 0;
        }

        //Setup shared memory region
        int ident = shmget(IPC_PRIVATE, iFileLen, IPC_CREAT | 0666);
        if(ident < 0) {
            perror("Shared memory allocation failed");
            return 0;
        }

        //Initialize the semaphores
        semaphore = semget(IPC_PRIVATE, 2, IPC_CREAT | 0666);
        semctl(semaphore, PROD_SEM, SETVAL, 0);
        semctl(semaphore, CONS_SEM, SETVAL, iFileLen);

        //Setup shared memory
        buffer = buffer_base = shmat(ident, NULL, 0);
	if((int)buffer == -1){
		perror("shmat Failed.");
		return 0;
	}

        //Allocate progress buffer
        progress_cursor = progress_buffer = calloc(iFileLen * 2 + 1, sizeof(char));
        
        //setup signal handlers
        signal(PROD_SIG, producer_signal);
        signal(CONS_SIG, consumer_signal);

        //Get the parent process pid
        parent_pid = getpid();

        //Fork processes
        cons_pid = fork();

        //Create consumer
        if(cons_pid == 0) {
            fclose(iFile);
            consumer_proc(oFile);
        }else{
            //Create producer
            prod_pid = fork();
            if(prod_pid == 0) {
                fclose(oFile);
                producer_proc(iFile);
            }
        }
        shmdt(buffer);
        
        //Following only runs in the parent process
        if(cons_pid != 0 && prod_pid != 0) {
            //TODO: Wait for both processes to exit
            int status = 0;
            int cnt = 0;

            while(true) {
                pid_t pid = waitpid(-1, &status, 0); 
                if(errno == ECHILD) {
                    cnt++;
                    errno = 0;
                }
                if(cnt >= 2)
                    break;
            }

            shmctl(ident, IPC_RMID, 0);
            semctl(semaphore, IPC_RMID, 0);
            printf("%s\n", progress_buffer);
        }
        free(progress_buffer);
        printf("Exit ");
        if(cons_pid == 0)
            printf("Consumer\n");
        else if(prod_pid == 0)
            printf("Producer\n");
        else
            printf("Parent\n");
    }else {
        printf("%s [input file] [output file]\r\n", argv[0]);
    }

    return 0;
}