fish: Allow events to be processed in guestfish.

Add 'event', 'list-events' and 'delete-event' commands so that event
handlers can be registered, listed and deleted in guestfish.  The
event handler is a shell script snippet or host command.

Cc: Pádraig Brady <P@draigBrady.com>

1 files changed, 272 insertions, 0 deletions

diff --git a/fish/events.c b/fish/events.c
new file mode 100644
index 00000000..11063723
--- /dev/null
+++ b/fish/events.c
@@ -0,0 +1,272 @@
+/* guestfish - the filesystem interactive shell
+ * Copyright (C) 2011 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include <assert.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include <guestfs.h>
+
+#include "hash.h"
+#include "hash-pjw.h"
+
+#include "fish.h"
+
+/* The hash table maps names to multiple (linked list of) event handlers. */
+static Hash_table *event_handlers;
+
+struct entry {
+  struct entry *next;           /* Next entry in linked list. */
+  char *name;                   /* Event name. */
+  char *command;                /* Shell script / command that runs. */
+  uint64_t event_bitmask;       /* Events this is registered for. */
+  int eh;        /* Event handle (from guestfs_set_event_callback). */
+};
+
+static void
+entry_free (void *x)
+{
+  if (x) {
+    struct entry *p = x;
+    entry_free (p->next);
+    free (p->name);
+    free (p->command);
+    free (p);
+  }
+}
+
+static size_t
+entry_hash (void const *x, size_t table_size)
+{
+  struct entry const *p = x;
+  return hash_pjw (p->name, table_size);
+}
+
+static bool
+entry_compare (void const *x, void const *y)
+{
+  struct entry const *p = x;
+  struct entry const *q = y;
+  return STREQ (p->name, q->name);
+}
+
+void
+init_event_handlers (void)
+{
+  assert (event_handlers == NULL);
+  event_handlers =
+    hash_initialize (64, NULL, entry_hash, entry_compare, entry_free);
+}
+
+void
+free_event_handlers (void)
+{
+  assert (event_handlers != NULL);
+  hash_free (event_handlers);
+  event_handlers = NULL;
+}
+
+static void
+do_event_handler (guestfs_h *g,
+                  void *opaque,
+                  uint64_t event,
+                  int event_handle,
+                  int flags,
+                  const char *buf, size_t buf_len,
+                  const uint64_t *array, size_t array_len)
+{
+  pid_t pid;
+  const char *argv[8 + array_len];
+  const char *shell;
+  struct entry *entry = opaque;
+  size_t i, j;
+  char *s;
+
+  pid = fork ();
+  if (pid == -1) {
+    perror ("event handler: fork");
+    return;
+  }
+
+  if (pid == 0) {               /* Child process. */
+    shell = getenv ("SHELL");
+    if (!shell)
+      shell = "/bin/sh";
+
+    setenv ("EVENT", event_name_of_event_bitmask (event), 1);
+
+    /* Construct the command and arguments. */
+    i = 0;
+    argv[i++] = shell;
+    argv[i++] = "-c";
+    argv[i++] = entry->command;
+    argv[i++] = ""; /* $0 */
+
+    if (buf != NULL)
+      /* XXX: So far, buf is always ASCII NUL-terminated.  There is no
+       * way to pass arbitrary 8 bit buffers.
+       */
+      argv[i++] = buf;
+
+    for (j = 0; j < array_len; ++j) {
+      if (asprintf (&s, "%" PRIu64, array[j]) == -1) {
+        perror ("event handler: asprintf");
+        _exit (EXIT_FAILURE);
+      }
+      argv[i++] = s;
+    }
+
+    argv[i++] = NULL;
+
+    execvp (argv[0], (void *) argv);
+    perror (argv[0]);
+
+    _exit (EXIT_FAILURE);
+  }
+
+  if (waitpid (pid, NULL, 0) == -1)
+    perror ("event handler: waitpid");
+}
+
+int
+run_event (const char *cmd, size_t argc, char *argv[])
+{
+  int r;
+  struct entry *entry = NULL, *old_entry;
+
+  if (argc != 3) {
+    fprintf (stderr,
+             _("use 'event <name> <eventset> <script>' to register an event handler\n"));
+    goto error;
+  }
+
+  entry = calloc (1, sizeof *entry);
+  if (entry == NULL) {
+    perror ("calloc");
+    goto error;
+  }
+  entry->eh = -1;
+
+  r = event_bitmask_of_event_set (argv[1], &entry->event_bitmask);
+  if (r == -1)
+    goto error;
+
+  entry->name = strdup (argv[0]);
+  if (entry->name == NULL) {
+    perror ("strdup");
+    goto error;
+  }
+  entry->command = strdup (argv[2]);
+  if (entry->command == NULL) {
+    perror ("strdup");
+    goto error;
+  }
+
+  entry->eh =
+    guestfs_set_event_callback (g, do_event_handler,
+                                entry->event_bitmask, 0, entry);
+  if (entry->eh == -1)
+    goto error;
+
+  r = hash_insert_if_absent (event_handlers, entry, (const void **) &old_entry);
+  if (r == -1)
+    goto error;
+  if (r == 0) {                 /* old_entry set to existing entry */
+    entry->next = old_entry->next;
+    /* XXX are we allowed to update the old entry? */
+    old_entry->next = entry;
+  }
+
+  return 0;
+
+ error:
+  if (entry) {
+    if (entry->eh >= 0)
+      guestfs_delete_event_callback (g, entry->eh);
+    free (entry->name);
+    free (entry->command);
+    free (entry);
+  }
+  return -1;
+}
+
+int
+run_delete_event (const char *cmd, size_t argc, char *argv[])
+{
+  if (argc != 1) {
+    fprintf (stderr,
+             _("use 'delete-event <name>' to delete an event handler\n"));
+    return -1;
+  }
+
+  const struct entry key = { .name = bad_cast (argv[0]) };
+  struct entry *entry, *p;
+
+  entry = hash_delete (event_handlers, &key);
+  if (!entry) {
+    fprintf (stderr, _("delete-event: %s: no such event handler\n"), argv[0]);
+    return -1;
+  }
+
+  /* Delete them from the handle. */
+  p = entry;
+  while (p) {
+    guestfs_delete_event_callback (g, p->eh);
+    p = p->next;
+  }
+
+  /* Free the structures. */
+  entry_free (entry);
+
+  return 0;
+}
+
+static bool
+list_event (void *x, void *data)
+{
+  struct entry *entry = x;
+
+  while (entry) {
+    printf ("\"%s\" (%d): ", entry->name, entry->eh);
+    print_event_set (entry->event_bitmask, stdout);
+    printf (": %s\n", entry->command);
+    entry = entry->next;
+  }
+
+  return 1;
+}
+
+int
+run_list_events (const char *cmd, size_t argc, char *argv[])
+{
+  if (argc != 0) {
+    fprintf (stderr,
+             _("use 'list-events' to list event handlers\n"));
+    return -1;
+  }
+
+  hash_do_for_each (event_handlers, list_event, NULL);
+  return 0;
+}