aboba/watcher.c

#include <stdalign.h>
#include <dirent.h>
#include <signal.h>
#include <errno.h>
#include <sys/inotify.h>

#define STB_DS_IMPLEMENTATION
#include "stb/stb_ds.h"
#define GEBS_NO_PREFIX
#define GEBS_IMPLEMENTATION
#include "gebs/gebs.h"

#define EVENT_BUFFER_SIZE (5 * (sizeof(struct inotify_event) + NAME_MAX + 1))
#define EVENT_BUFFER_ALIGNMENT __attribute__((aligned(alignof(struct inotify_event))))

typedef struct {
    int key;        // watch descriptor
    char *value;    // the path
} File_Map;

typedef struct {
    File_Map *fmap;
    int fd;
    NString_List ignored;
} Watcher;

bool watcher_make(Watcher *w)
{
    String_Builder watcherignore = {0};
    defer { sb_free(&watcherignore); }
    if (sb_read_file(&watcherignore, "./.watcherignore")) {
        sb_finish(&watcherignore);

        char *line = strtok(watcherignore.items, "\n");
        while (line != nil) {
            char *line_copy = malloc(strlen(line)+1);
            strcpy(line_copy, line);
            list_append(&w->ignored, line_copy);
            line = strtok(nil, "\n");
        }
    }

    if ((w->fd = inotify_init1(IN_NONBLOCK)) < 0) {
        LOGE("inotify_init1(): %s\n", strerror(errno));
        return false;
    }

    return true;
}

void watcher_free(Watcher *w)
{

    for (size_t i = 0; i < w->ignored.count; i++) {
        free(w->ignored.items[i]);
    }
    list_free(&w->ignored);

    for (size_t i = 0; i < hmlen(w->fmap); i++) {
        free(w->fmap[i].value);
        inotify_rm_watch(w->fd, w->fmap[i].key);
    }
    hmfree(w->fmap);

    close(w->fd);
}

void watcher_add_file1(Watcher *w, int wd, char *path)
{
    char *path_copy = gebs_malloc(&default_allocator, strlen(path)+1);
    strcpy(path_copy, path);
    hmput(w->fmap, wd, path_copy);
}

void watcher_add_file(Watcher *w, char *path)
{
    uint32_t file_mask = IN_MODIFY | IN_DONT_FOLLOW;
    int file_wd = inotify_add_watch(w->fd, path, file_mask);
    if (file_wd < 0) {
        LOGE("Could not add %s to watcher\n", path);
        return;
    }
    
    watcher_add_file1(w, file_wd, path);
}

void watcher_add_all(Watcher *w, char *root)
{
    DIR *dir;
    struct dirent *entry;

    if ((dir = opendir(root)) == nil) {
        LOGE("Could not open dir %s\n", root);
        return;
    }
    defer { closedir(dir); }

    while ((entry = readdir(dir)) != nil) {
        if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0) {
            continue;
        }

        char path[PATH_MAX];
        snprintf(path, sizeof(path), "%s/%s", root, entry->d_name);

        for (size_t i = 0; i < w->ignored.count; i++) {
            if (strcmp(w->ignored.items[i], path) == 0) {
                LOGI("Skipping %s\n", path);
                goto next;
            }
        }

        if (entry->d_type == DT_DIR) {
            watcher_add_all(w, path);
        } else {
            watcher_add_file(w, path);
        }
next:
    }
}

char *prog = nil;
bool running = true;

void handle_sigint(int signo)
{
    running = false;
}

int main(int argc, char ** argv)
{
    prog = SHIFT(&argc, &argv);
    if (argc < 2) {
        LOGI("Usage: ./watcher <dir> <command>\n");
        return 0;
    }

    char *watch_dir = SHIFT(&argc, &argv);
    Cmd cmd = {0};
    defer { cmd_free(&cmd); }
    while (argc > 0) {
        cmd_append(&cmd, SHIFT(&argc, &argv));
    }

    signal(SIGINT, &handle_sigint);

    Watcher watcher = {0};
    if (!watcher_make(&watcher)) {
        LOGE("Failed to create the watcher\n");
        return 1;
    }
    defer { watcher_free(&watcher); }

    watcher_add_all(&watcher, watch_dir);

    pid_t cmd_pid = cmd_run_async(&cmd);

    char event_buffer[EVENT_BUFFER_SIZE] EVENT_BUFFER_ALIGNMENT;
    while (running) {
        ssize_t nread;
        if ((nread = read(watcher.fd, event_buffer, EVENT_BUFFER_SIZE)) < 0) {
            if (errno != EAGAIN) {
                LOGE("read(): %s\n", strerror(errno));
                return 1;
            } else {
                continue;
            }
        }

        for (char *event_ptr = event_buffer; event_ptr < event_buffer + nread; ) {
            const struct inotify_event *event = (const struct inotify_event *)event_ptr;

            ssize_t idx = hmgeti(watcher.fmap, event->wd);
            char *path = watcher.fmap[idx].value;

            if (event->mask & IN_IGNORED) {
                hmdel(watcher.fmap, event->wd);
                watcher_add_file(&watcher, path);
            }

            if (event->mask & (IN_MODIFY | IN_IGNORED)) {
                LOGI("%s changed (%04x)\n", path, event->mask);

                if (cmd_pid != -1) {
                    LOGI("Killing %d\n", cmd_pid);
                    kill(cmd_pid, SIGKILL);
                }

                cmd_pid = cmd_run_async(&cmd);
            }

            event_ptr += sizeof(struct inotify_event) + event->len;
        }

        sleep(1);
    }

    return 0;
}