File: games-scores-backend.c

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/* games-scores-backend.c
 *
 * Copyright (C) 2005 Callum McKenzie
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <config.h>

#include <glib.h>
#include <glib-object.h>

#include <string.h>
#include <stdlib.h>

#include "games-score.h"
#include "games-scores.h"
#include "games-scores-backend.h"


#ifdef ENABLE_SETGID
#include "games-setgid-io.h"
#endif

struct _GamesScoresBackendPrivate {
  GamesScoreStyle style;
  time_t timestamp;
  gchar *filename;
  gint fd;
};

G_DEFINE_TYPE (GamesScoresBackend, games_scores_backend, G_TYPE_OBJECT);

static void
games_scores_backend_finalize (GObject *object)
{
  GamesScoresBackend *backend = GAMES_SCORES_BACKEND (object);
  GamesScoresBackendPrivate *priv = backend->priv;

  g_free (priv->filename);
  /* FIXME: more to do? */

  G_OBJECT_CLASS (games_scores_backend_parent_class)->finalize (object);
}

static void
games_scores_backend_class_init (GamesScoresBackendClass * klass)
{
  GObjectClass *oclass = G_OBJECT_CLASS (klass);

  g_type_class_add_private (klass, sizeof (GamesScoresBackendPrivate));
  oclass->finalize = games_scores_backend_finalize;
}

static void
games_scores_backend_init (GamesScoresBackend * backend)
{
  backend->priv = G_TYPE_INSTANCE_GET_PRIVATE (backend,
					       GAMES_TYPE_SCORES_BACKEND,
					       GamesScoresBackendPrivate);
}

GamesScoresBackend *
games_scores_backend_new (GamesScoreStyle style,
			  char *base_name,
                          char *name)
{
  GamesScoresBackend *backend;
  gchar *fullname;

  backend = GAMES_SCORES_BACKEND (g_object_new (GAMES_TYPE_SCORES_BACKEND,
						NULL));

  if (name[0] == '\0')		/* Name is "" */
    fullname = g_strjoin (".", base_name, "scores", NULL);
  else
    fullname = g_strjoin (".", base_name, name, "scores", NULL);

  backend->priv->timestamp = 0;
  backend->priv->style = style;
  backend->scores_list = NULL;
  backend->priv->filename = g_build_filename (SCOREDIR,
                                              fullname, NULL);
  g_free (fullname);

  backend->priv->fd = -1;

  return backend;
}

#ifdef ENABLE_SETGID

/* Get a lock on the scores file. Block until it is available.
 * This also supplies the file descriptor we need. The return value
 * is whether we were succesful or not. */
static gboolean
games_scores_backend_get_lock (GamesScoresBackend * self)
{
  gint error;

  if (self->priv->fd != -1) {
    /* Assume we already have the lock and rewind the file to
     * the beginning. */
    setgid_io_seek (self->priv->fd, 0, SEEK_SET);
    return TRUE;		/* Assume we already have the lock. */
  }

  self->priv->fd = setgid_io_open (self->priv->filename, O_RDWR);
  if (self->priv->fd == -1) {
    return FALSE;
  }

  error = setgid_io_lock (self->priv->fd);

  if (error == -1) {
    setgid_io_close (self->priv->fd);
    self->priv->fd = -1;
    return FALSE;
  }

  return TRUE;
}

/* Release the lock on the scores file and dispose of the fd. */
/* We ignore errors, there is nothing we can do about them. */
static void
games_scores_backend_release_lock (GamesScoresBackend * self)
{
  /* We don't have a lock, ignore this call. */
  if (self->priv->fd == -1)
    return;

  setgid_io_unlock (self->priv->fd);

  setgid_io_close (self->priv->fd);

  self->priv->fd = -1;
}

#endif /* ENABLE_SETGID */

/* You can alter the list returned by this function, but you must
 * make sure you set it again with the _set_scores method or discard it
 * with with the _discard_scores method. Otherwise deadlocks will ensue. */
GList *
games_scores_backend_get_scores (GamesScoresBackend * self)
{
#ifdef ENABLE_SETGID
  gchar *buffer;
  gchar *eol;
  gchar *scorestr;
  gchar *timestr;
  gchar *namestr;
  GamesScore *newscore;
  struct stat info;
  int error;
  ssize_t length, target;
  GList *t;

  /* Check for a change in the scores file and update if necessary. */
  error = setgid_io_stat (self->priv->filename, &info);

  /* If an error occurs then we give up on the file and return NULL. */
  if (error != 0)
    return NULL;

  if ((info.st_mtime > self->priv->timestamp) || (self->scores_list == NULL)) {
    self->priv->timestamp = info.st_mtime;

    /* Dump the old list of scores. */
    t = self->scores_list;
    while (t != NULL) {
      games_score_destroy ((GamesScore *) t->data);
      t = g_list_next (t);
    }
    g_list_free (self->scores_list);
    self->scores_list = NULL;

    /* Lock the file and get the list. */
    if (!games_scores_backend_get_lock (self))
      return NULL;

    buffer = g_malloc (info.st_size + 1);
    if (buffer == NULL) {
      games_scores_backend_release_lock (self);
      return NULL;
    }

    target = info.st_size;
    length = 0;
    do {
      target -= length;
      length = setgid_io_read (self->priv->fd, buffer, info.st_size);
      if (length == -1) {
	games_scores_backend_release_lock (self);
	g_free (buffer);
	return NULL;
      }
    } while (length < target);

    buffer[info.st_size] = '\0';

    /* FIXME: These details should be in a sub-class. */

    /* Parse the list. We start by breaking it into lines. */
    /* Since the buffer is null-terminated
     * we can do the string stuff reasonably safely. */
    eol = strchr (buffer, '\n');
    scorestr = buffer;
    while (eol != NULL) {
      *eol++ = '\0';
      timestr = strchr (scorestr, ' ');
      if (timestr == NULL)
	break;
      *timestr++ = '\0';
      namestr = strchr (timestr, ' ');
      if (namestr == NULL)
	break;
      *namestr++ = '\0';
      /* At this point we have three strings, all null terminated. All
       * part of the original buffer. */
      newscore = games_score_new ();
      newscore->name = g_strdup (namestr);
      newscore->time = g_ascii_strtoull (timestr, NULL, 10);
      switch (self->priv->style) {
      case GAMES_SCORES_STYLE_PLAIN_DESCENDING:
      case GAMES_SCORES_STYLE_PLAIN_ASCENDING:
	newscore->value.plain = g_ascii_strtod (scorestr, NULL);
	break;
      case GAMES_SCORES_STYLE_TIME_DESCENDING:
      case GAMES_SCORES_STYLE_TIME_ASCENDING:
	newscore->value.time_double = g_ascii_strtod (scorestr, NULL);
	break;
      default:
        g_assert_not_reached ();
      }
      self->scores_list = g_list_append (self->scores_list, newscore);
      /* Setup again for the next time around. */
      scorestr = eol;
      eol = strchr (eol, '\n');
    }

    g_free (buffer);
  }

  /* FIXME: Sort the scores! We shouldn't rely on the file being sorted. */

  return self->scores_list;
#else
  return NULL;
#endif /* ENABLE_SETGID */
}

gboolean
games_scores_backend_set_scores (GamesScoresBackend * self, GList * list)
{
#ifdef ENABLE_SETGID
  GList *s;
  GamesScore *d;
  gchar *buffer;
  gint output_length = 0;
  gchar dtostrbuf[G_ASCII_DTOSTR_BUF_SIZE];

  if (!games_scores_backend_get_lock (self))
    return FALSE;

  self->scores_list = list;

  s = list;
  while (s != NULL) {
    gdouble rscore;
    guint64 rtime;
    gchar *rname;

    d = (GamesScore *) s->data;
    rscore = 0.0;
    switch (self->priv->style) {
    case GAMES_SCORES_STYLE_PLAIN_DESCENDING:
    case GAMES_SCORES_STYLE_PLAIN_ASCENDING:
      rscore = d->value.plain;
      break;
    case GAMES_SCORES_STYLE_TIME_DESCENDING:
    case GAMES_SCORES_STYLE_TIME_ASCENDING:
      rscore = d->value.time_double;
      break;
    default:
      g_assert_not_reached ();
    }
    rtime = d->time;
    rname = d->name;

    buffer = g_strdup_printf ("%s %lld %s\n",
			      g_ascii_dtostr (dtostrbuf, sizeof (dtostrbuf),
					      rscore), rtime, rname);
    setgid_io_write (self->priv->fd, buffer, strlen (buffer));
    output_length += strlen (buffer);
    /* Ignore any errors and blunder on. */
    g_free (buffer);

    s = g_list_next (s);
  }

  /* Remove any content in the file that hasn't yet been overwritten. */
  setgid_io_truncate (self->priv->fd, output_length--);

  /* Update the timestamp so we don't reread the scores unnecessarily. */
  self->priv->timestamp = time (NULL);

  games_scores_backend_release_lock (self);

  return TRUE;
#else
  return FALSE;
#endif /* ENABLE_SETGID */
}

void
games_scores_backend_discard_scores (GamesScoresBackend * self)
{
#ifdef ENABLE_SETGID
  games_scores_backend_release_lock (self);
#endif
}