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/*
* Test the equivalent execution of this propgram with `du`:
*
* du --block-size=512 -s <path>
*
*/
#include <dirent.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#define MAX_PATH_LEN 1024
int
WAIT(int id_sem, int n)
{
struct sembuf sops[1] = { { n, -1, 0 } };
return semop(id_sem, sops, 1);
}
int
SIGNAL(int id_sem, int n)
{
struct sembuf sops[1] = { { n, 1, 0 } };
return semop(id_sem, sops, 1);
}
void
handle_scanner_end(int id_shm, int id_sem, int id_scanner, char* pathname)
{
char* msg;
if ((msg = (char*)shmat(id_shm, NULL, 0)) == (char*)-1) {
perror("shmat");
exit(1);
}
WAIT(id_sem, 0);
sprintf(msg, "%d;END;%s", id_scanner, pathname);
SIGNAL(id_sem, 1);
}
void
stater(int id_shm, int id_sem, int* scanners, int scanners_n)
{
char* msg;
int n;
struct stat sb;
char* token;
char* pathname;
int sid;
if ((msg = (char*)shmat(id_shm, NULL, 0)) == (char*)-1) {
perror("shmat");
exit(1);
}
n = 0;
while (n < scanners_n) {
WAIT(id_sem, 1);
/* I previously opened the file with `open` so I know I can read
* that. So now I open that file with stat, because `msg` contains
* the patname as string.
* But first I have to parse the `msg` receiving the scanner id.
*/
token = strtok(msg, ";");
sid = atoi(token);
pathname = strtok(NULL, ";");
if (strcmp(pathname, "END") == 0) {
pathname = strtok(NULL, ";");
printf("%d\t%s\n", scanners[sid], pathname);
n++;
} else {
stat(pathname, &sb);
scanners[sid] += sb.st_blocks;
}
SIGNAL(id_sem, 0);
}
}
void
scanner(int id_shm, int id_sem, int scanner_id, char* pathname)
{
char* msg;
struct stat sb;
struct dirent* db;
int fd;
DIR* dp;
char buffer[MAX_PATH_LEN];
if ((msg = (char*)shmat(id_shm, NULL, 0)) == (char*)-1) {
perror("shmat");
exit(1);
}
if ((fd = open(pathname, O_RDONLY)) == -1) {
perror("open");
exit(1);
}
fstat(fd, &sb);
if ((sb.st_mode & S_IFMT) == S_IFDIR) {
if ((dp = opendir(pathname)) == NULL) {
perror("opendir");
exit(1);
}
while ((db = readdir(dp)) != NULL) {
if ((strcmp(db->d_name, ".") == 0) || strcmp(db->d_name, "..") == 0)
continue;
sprintf(buffer, "%s/%s", pathname, db->d_name);
scanner(id_shm, id_sem, scanner_id, buffer);
}
closedir(dp);
}
WAIT(id_sem, 0);
sprintf(msg, "%d;%s", scanner_id, pathname);
SIGNAL(id_sem, 1);
}
int
main(int argc, char* argv[])
{
int id_shm;
int i;
pid_t pid;
pid_t pid_scanners[argc - 1];
int scanners[argc - 1];
int id_sem;
for (i = 0; i < argc - 1; ++i)
scanners[i] = 0;
if ((id_shm = shmget(IPC_PRIVATE, 1024, IPC_CREAT | IPC_EXCL | 0644)) == -1) {
perror("shmget");
exit(1);
}
if ((id_sem = semget(IPC_PRIVATE, 2, IPC_CREAT | IPC_EXCL | 0644)) == -1) {
perror("semget");
exit(1);
}
semctl(id_sem, 0, SETVAL, 1);
semctl(id_sem, 1, SETVAL, 0);
if (argc < 2) {
exit(0);
}
pid = fork();
if (pid == -1) {
perror("fork");
exit(1);
}
if (pid == 0) {
stater(id_shm, id_sem, scanners, argc - 1);
exit(0);
}
for (i = 1; i < argc; ++i) {
pid_scanners[i - 1] = fork();
if (pid_scanners[i - 1] == -1) {
perror("fork");
exit(1);
}
if (pid_scanners[i - 1] == 0) {
scanner(id_shm, id_sem, i - 1, argv[i]);
handle_scanner_end(id_shm, id_sem, i - 1, argv[i]);
exit(0);
}
}
for (i = 0; i < argc; ++i)
wait(NULL);
if (shmctl(id_shm, IPC_RMID, NULL) == -1) {
perror("shmctl");
exit(1);
}
if (semctl(id_sem, 2, IPC_RMID) == -1) {
perror("semctl");
exit(1);
}
return 0;
}
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