[gnome-maps/wip/mlundblad/transit-plugin-gtfs-local: 4/5] WIP: Add class for parsing GTFS files

[Marcus Lundblad <mlundblad src gnome org>]

commit 2b74748bb064c1d9cdd923e544e9d4acf52b5e05
Author: Marcus Lundblad <ml update uu se>
Date:   Sat Feb 15 09:29:35 2020 +0100

    WIP: Add class for parsing GTFS files

 lib/maps-gtfs.c | 256 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/maps-gtfs.h |  46 ++++++++++
 lib/meson.build |   2 +
 3 files changed, 304 insertions(+)
---
diff --git a/lib/maps-gtfs.c b/lib/maps-gtfs.c
new file mode 100644
index 00000000..ceac150f
--- /dev/null
+++ b/lib/maps-gtfs.c
@@ -0,0 +1,256 @@
+/*
+ * Copyright (c) 2020 Marcus Lundblad
+ *
+ * GNOME Maps 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.
+ *
+ * GNOME Maps 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 GNOME Maps; if not, see <http://www.gnu.org/licenses/>
+ *
+ * Author: Marcus Lundblad <ml update uu se>
+ */
+
+#include "maps-gtfs.h"
+#include "mapsintl.h"
+
+#include <archive.h>
+#include <archive_entry.h>
+#include <glib.h>
+
+#define MAPS_GTFS_ERROR maps_gtfs_error_quark ()
+
+static const int BLOCK_SIZE = 10 * 1024;
+
+GQuark
+maps_gtfs_error_quark (void)
+{
+  return g_quark_from_static_string ("maps-gtfs-error");
+}
+
+struct _MapsGTFSPrivate
+{
+  gchar *file;
+  gchar *read_buffer;
+  guint read_size;
+  guint read_pos;
+};
+
+enum {
+  PROP_0,
+};
+
+G_DEFINE_TYPE_WITH_PRIVATE (MapsGTFS, maps_gtfs, G_TYPE_OBJECT)
+
+static void
+maps_gtfs_dispose (GObject *object)
+{
+  MapsGTFS *gtfs = MAPS_GTFS (object);
+  MapsGTFSPrivate *priv = maps_gtfs_get_instance_private (gtfs);
+
+  g_free (priv->file);
+  priv->file = NULL;
+  g_free (priv->read_buffer);
+  priv->read_buffer = NULL;
+
+  G_OBJECT_CLASS (maps_gtfs_parent_class)->dispose (object);
+}
+
+static void
+maps_gtfs_class_init (MapsGTFSClass *klass)
+{
+  GObjectClass *maps_class = G_OBJECT_CLASS (klass);
+
+  maps_class->dispose = maps_gtfs_dispose;
+}
+
+static void
+maps_gtfs_init (MapsGTFS *gtfs)
+{
+  gtfs->priv = maps_gtfs_get_instance_private (gtfs);
+  gtfs->priv->file = NULL;
+  gtfs->priv->read_buffer = g_malloc (BLOCK_SIZE);
+  /* indicate we need to read a new chunk of data when reading the first line */
+  gtfs->priv->read_pos = 0;
+  gtfs->priv->read_size = 0;
+}
+
+MapsGTFS *
+maps_gtfs_new (char *file)
+{
+  MapsGTFS *gtfs = g_object_new (MAPS_TYPE_GTFS, NULL);
+  MapsGTFSPrivate *priv = maps_gtfs_get_instance_private (gtfs);
+
+  priv->file = g_strdup (file);
+  return gtfs;
+}
+
+static char *
+read_line (MapsGTFS *gtfs, struct archive *a)
+{
+  MapsGTFSPrivate *priv = maps_gtfs_get_instance_private (gtfs);
+  int i;
+  gchar *result;
+
+  if (priv->read_pos == priv->read_size) {
+    g_debug ("Read new chunk");
+    priv->read_size = archive_read_data (a, priv->read_buffer, BLOCK_SIZE);
+
+    if (priv->read_size < 0) {
+      g_error ("Failed to read data");
+      return NULL;
+    } else if (priv->read_size == 0) {
+      g_debug ("No more data to read");
+      return NULL;
+    }
+  }
+
+  g_debug ("Read pos at start: %d", priv->read_pos);
+
+  /* find next line break */
+  i = priv->read_pos;
+  while (priv->read_buffer[i] != '\n' && priv->read_buffer[i] != '\r' &&
+         i < priv->read_size) {
+    i++;
+  }
+
+  /* if we didn't read til the end of the buffer, just copy the line */
+  if (i < priv->read_size) {
+    result = g_strndup (priv->read_buffer + priv->read_pos, i - priv->read_pos);
+    priv->read_pos = i;
+    /* skip upcoming newline(s) */
+    while (priv->read_buffer[priv->read_pos] == '\n' ||
+           priv->read_buffer[priv->read_pos] == '\r') {
+      priv->read_pos++;
+    }
+  } else {
+    /* copy the first part up to the buffer end */
+    g_autofree gchar *first =
+      g_strndup (priv->read_buffer + priv->read_pos, i - priv->read_pos);
+
+    /* read next chunk */
+    g_debug ("Read next chunk");
+    priv->read_size = archive_read_data (a, priv->read_buffer, BLOCK_SIZE);
+    priv->read_pos = 0;
+
+    if (priv->read_size < 0) {
+      g_error ("Failed to read data");
+      return NULL;
+    } else if (priv->read_size == 0) {
+      g_debug ("No more data to read");
+      return NULL;
+    }
+
+    /* find next line break */
+    i = priv->read_pos;
+    while (priv->read_buffer[i] != '\n' && priv->read_buffer[i] != '\r' &&
+           i < priv->read_size) {
+      i++;
+    }
+    priv->read_pos = i;
+
+    /* copy next part, read from new buffer */
+    g_autofree gchar *second = g_strndup (priv->read_buffer, i);
+
+    /* skip upcoming newline(s) */
+    while (priv->read_buffer[priv->read_pos] == '\n' ||
+           priv->read_buffer[priv->read_pos] == '\r') {
+      priv->read_pos++;
+    }
+
+    /* concatenate parts */
+    result = g_strdup_printf("%s%s", first, second);
+  }
+
+  return result;
+}
+
+static gboolean
+parse_file (MapsGTFS *gtfs, struct archive *a, const gchar *filename)
+{
+  for (;;) {
+    g_autofree gchar *line = read_line (gtfs, a);
+    if (!line)
+      break;
+    g_debug ("Line: %s", line);
+  }
+
+  return TRUE;
+}
+
+static gboolean
+parse_entries (MapsGTFS *gtfs, struct archive *a)
+{
+  struct archive_entry *entry;
+  gboolean found_agency = FALSE;
+  gboolean found_stops = FALSE;
+  gboolean found_routes = FALSE;
+  gboolean found_trips = FALSE;
+  gboolean found_stop_times = FALSE;
+
+  while (archive_read_next_header(a, &entry) == ARCHIVE_OK) {
+    const char *filename = archive_entry_pathname (entry);
+
+    g_debug ("Entry %s", archive_entry_pathname(entry));
+
+    if (g_str_equal (filename, "agency.txt")) {
+      found_agency = TRUE;
+    } else if (g_str_equal (filename, "stops.txt")) {
+      found_stops = TRUE;
+    } else if (g_str_equal (filename, "routes.txt")) {
+      found_routes = TRUE;
+    } else if (g_str_equal (filename, "trips.txt")) {
+      found_trips = TRUE;
+    } else if (g_str_equal (filename, "stop_times.txt")) {
+      found_stop_times = TRUE;
+    }
+
+    if (g_str_equal (filename, "routes.txt"))
+      if (!parse_file (gtfs, a, filename))
+        return FALSE;
+
+    archive_read_data_skip (a);
+  }
+
+  if (found_agency && found_stops && found_routes && found_trips && found_stop_times)
+    return TRUE;
+  else
+    return FALSE;
+}
+
+void
+maps_gtfs_parse (MapsGTFS *gtfs, GError **error)
+{
+  MapsGTFSPrivate *priv = maps_gtfs_get_instance_private (gtfs);
+  struct archive *a;
+  int r;
+
+  a = archive_read_new ();
+  archive_read_support_format_zip (a);
+  r = archive_read_open_filename (a, priv->file, BLOCK_SIZE);
+
+  if (r != ARCHIVE_OK)
+    {
+      *error = g_error_new_literal (MAPS_GTFS_ERROR, 0,
+                                    _("Failed to open GTFS ZIP file"));
+      return;
+    }
+
+  if (!parse_entries (gtfs, a)) {
+    *error = g_error_new_literal (MAPS_GTFS_ERROR, 0,
+                                  _("Failed to parse GTFS file"));
+    return;
+  }
+
+  r = archive_read_free(a);
+  if (r != ARCHIVE_OK)
+    *error = g_error_new_literal (MAPS_GTFS_ERROR, 0,
+                                  _("Failed to free GTFS ZIP file"));
+
+}
diff --git a/lib/maps-gtfs.h b/lib/maps-gtfs.h
new file mode 100644
index 00000000..c1417eb9
--- /dev/null
+++ b/lib/maps-gtfs.h
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2020 Marcus Lundblad
+ *
+ * GNOME Maps 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.
+ *
+ * GNOME Maps 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 GNOME Maps; if not, see <http://www.gnu.org/licenses/>
+ *
+ * Author: Marcus Lundblad <ml update uu se>
+ */
+
+#ifndef __MAPS_GTFS__
+#define __MAPS_GTFS__
+
+#include <glib-object.h>
+
+#define MAPS_TYPE_GTFS maps_gtfs_get_type ()
+G_DECLARE_FINAL_TYPE(MapsGTFS, maps_gtfs, MAPS, GTFS, GObject)
+
+typedef struct _MapsGTFSPrivate MapsGTFSPrivate;
+
+struct _MapsGTFS
+{
+  GObject parent_instance;
+  MapsGTFSPrivate *priv;
+};
+
+
+struct _MapsGTFSClass
+{
+  GObjectClass parent_class;
+};
+
+MapsGTFS *maps_gtfs_new (char *file);
+
+void maps_gtfs_parse (MapsGTFS *gtfs, GError **error);
+
+#endif //__MAPS_GTFS__
diff --git a/lib/meson.build b/lib/meson.build
index 60543648..c2f72ac3 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -4,6 +4,7 @@ headers_private = files(
        'maps-contact.h',
        'maps-contact-store.h',
        'maps-file-tile-source.h',
+       'maps-gtfs.h',
        'maps-osm.h',
        'maps-osm-changeset.h',
        'maps-osm-node.h',
@@ -17,6 +18,7 @@ sources = files(
        'maps-contact.c',
        'maps-contact-store.c',
        'maps-file-tile-source.c',
+       'maps-gtfs.c',
        'maps-osm.c',
        'maps-osm-changeset.c',
        'maps-osm-node.c',