hiload/src/filewatcher/filewatch.c

#include "filewatch.h"

#include "common.h"
#include "filewatch_context.h"
#include "filewatch_type.h"

#include <errno.h>
#include <string.h>
#include <sys/inotify.h>
#include <unistd.h>

/*
 * File Watch
 */

struct WatchMaskParams {
  u32 file_mask;
  u32 parent_mask;
};

static inline struct WatchMaskParams inode_watch_masks_create(u32 flags) {

  u32 file_mask = 0u;
  u32 parent_mask = 0u;

  if (has_mask(flags, HI_FILE_MODIFY)) {
    file_mask |= IN_MODIFY;
  }
  if (has_mask(flags, HI_FILE_CREATE)) {
    parent_mask |= IN_CREATE;
  }
  if (has_mask(flags, HI_FILE_DELETE)) {
    file_mask |= IN_DELETE_SELF;
    parent_mask |= IN_DELETE;
  }
  if (has_mask(flags, HI_FILE_MOVE)) {
    file_mask |= IN_MOVE_SELF;
    parent_mask |= IN_MOVED_TO;
  }

  // Append if watch exists
  file_mask |= IN_MASK_ADD;
  parent_mask |= IN_MASK_ADD;

  return (struct WatchMaskParams){.file_mask = file_mask,
                                  .parent_mask = parent_mask};
}

static void file_watch_destroy(int fd, FileWatch *fw) {
  inotify_rm_watch(fd, fw->wd);
  free((void *)fw->path);

  fw->wd = -1;
  fw->path = NULL;
}

void file_watch_destroy_watches(FileWatcherContext *ctx) {
  for (size_t i = 0; i < sc_array_size(&ctx->watches); i++) {
    FileWatch *fw = &sc_array_at(&ctx->watches, i);
    file_watch_destroy(ctx->fd, fw);
  }
  sc_array_term(&ctx->watches);
}

FileWatch *file_watch_find_by_wd(FileWatcherContext *ctx, int wd,
                                   size_t *index) {
  struct sc_array_fwatch *watches = &ctx->watches;

  for (size_t i = 0; i < sc_array_size(watches); ++i) {
    FileWatch *fw = &sc_array_at(watches, i);
    if (fw->wd == wd) {
      if (index) {
        *index = i;
      }
      return fw;
    }
  }
  return NULL;
}

FileWatch *file_watch_find_by_path(FileWatcherContext *ctx,
                                     const char *path, size_t *index) {
  for (size_t i = 0; i < sc_array_size(&ctx->watches); i++) {
    FileWatch *watch = &sc_array_at(&ctx->watches, i);
    if (strcmp(watch->path, path) == 0) {
      if (index) {
        *index = i;
      }
      return watch;
    }
  }
  return NULL;
}

/**
 * Return null terminated char array with the parent, or NULL if no path
 * separator was found.
 * */
static char *get_parent_folder(const char path[static 1]) {
  const char *last_separator = strrchr(path, '/');
  if (!last_separator)
    return NULL;

  // add one for the trailing slash
  size_t length = last_separator - path + 1;
  char *parent = calloc(length, sizeof(char));
  strncpy(parent, path, length);
  parent[length - 1] = '/';
  parent[length] = '\0';
  return parent;
}

HiResult file_watch_add(FileWatcherContext *ctx, u32 mask,
                            const char *path) {
  if (!ctx || ctx->fd == -1) {
    log_error("Invalid inotify context\n");
    return HI_FAIL;
  }
  struct WatchMaskParams params = inode_watch_masks_create(mask);

  FileWatch *watch = file_watch_find_by_path(ctx, path, NULL);
  if (!watch) {
    int wd = inotify_add_watch(ctx->fd, path, params.file_mask);
    if (wd == -1) {
      log_error("Couldn't watch: %s: %s\n", path, strerror(errno));
      return HI_FAIL;
    }
    FileWatch wp = {.wd = wd, .mask = mask, .path = strdup(path)};
    sc_array_add(&ctx->watches, wp);
    watch = &sc_array_last(&ctx->watches);
  } else {
    inotify_add_watch(ctx->fd, path, params.file_mask);
  }

  if (!has_mask(HI_FILE_PARENT, mask)) {
    char *parent_name = get_parent_folder(path);
    FileWatch *parent_watch = file_watch_find_by_path(ctx, parent_name, NULL);
    if (!parent_watch) {
      // parent not yet watched
      int wd = inotify_add_watch(ctx->fd, parent_name, params.parent_mask);
      FileWatch wp = {.wd = wd, .mask = HI_FILE_PARENT, .path = parent_name};
      sc_array_init(&wp.files);
      sc_array_add(&wp.files, strdup(watch->path));
      sc_array_add(&ctx->watches, wp);
    } else {
      free(parent_name);
      inotify_add_watch(ctx->fd, parent_watch->path, params.parent_mask);
      {
        // Make sure we don't add a duplicate if the file is already marked
        bool exists = false;
        for (size_t i = 0; i < sc_array_size(&parent_watch->files); i++) {
          const char *file = sc_array_at(&parent_watch->files, i);
          // we store the pointer directly, so this should be fine :D
          if (file == watch->path) {
            exists = true;
            break;
          }
        }
        if (!exists) {
          sc_array_add(&parent_watch->files, watch->path);
        }
      }
    }
  }

  return HI_OK;
}

HiResult file_watch_remove(FileWatcherContext *ctx, const char *path) {

  size_t i = 0;
  FileWatch *watch = file_watch_find_by_path(ctx, path, &i);
  if (watch) {

    // Destroy parent reference. We assume it will only have one.
    char *parent = get_parent_folder(path);
    if (parent) {
      FileWatch *pw = file_watch_find_by_path(ctx, parent, NULL);
      if (pw) {
        for (size_t i = 0; i < sc_array_size(&pw->files); i++) {
          const char *fn = sc_array_at(&pw->files, i);
          if (fn == watch->path) {
            sc_array_del(&pw->files, i);
            break;
          }
        }
      }
      free(parent);
    }
    file_watch_destroy(ctx->fd, watch);
    sc_array_del(&ctx->watches, i);
    return HI_OK;
  }
  return HI_FAIL;
}