implement --reverse option

fixes mlj#41

castget.1.ronn

@@ -52,6 +52,9 @@ options as arguments.
 
 ### Global options
 
+  * `-R`, `--reverse`:
+    Reverse the order in which items in feeds are processed.
+
   * `-r`, `--resume`:
     Resume aborted downloads. Make sure not to use this option if the RSS feed uses the same filename for multiple enclosures as this will corrupt existing downloads.
 

src/castget.c

@@ -71,6 +71,7 @@ int main(int argc, char **argv)
   static gboolean first_only = FALSE;
   static gboolean resume = FALSE;
   static gboolean debug = FALSE;
+  static gboolean reverse = FALSE;
   static gboolean show_progress_bar = FALSE;
   static gchar *rcfile = NULL;
   static gchar *filter_regex = NULL;
@@ -103,6 +104,8 @@ int main(int argc, char **argv)
     { "quiet", 'q', 0, G_OPTION_ARG_NONE, &quiet, "only print error messages" },
     { "first-only", '1', 0, G_OPTION_ARG_NONE, &first_only,
       "only process the most recent item from each channel" },
+    { "reverse", 'R', 0, G_OPTION_ARG_NONE, &reverse,
+      "process the channel in reverse order" },
     { "filter", 'f', 0, G_OPTION_ARG_STRING, &filter_regex,
       "only process items whose enclosure names match a regular expression" },
 
@@ -143,6 +146,7 @@ int main(int argc, char **argv)
   opts->first_only = first_only;
   opts->resume = resume;
   opts->debug = debug;
+  opts->reverse = reverse;
   opts->show_progress_bar = show_progress_bar;
 
   if (catchup) {

src/channel.c

@@ -34,6 +34,9 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 
+void _initialize_index(channel_index *index, int num_items, int reverse);
+int _next_index(channel_index *index);
+
 static int _enclosure_pattern_match(enclosure_filter *filter,
                                     const enclosure *enclosure);
 
@@ -304,8 +307,12 @@ int channel_update(channel *c, void *user_data, channel_callback cb,
   if (!f)
     return 1;
 
+  channel_index index;
+  _initialize_index(&index, f->num_items, opts->reverse);
+
   /* Check enclosures in RSS file. */
-  for (i = 0; i < f->num_items; i++)
+  while (_next_index(&index)) {
+    i = index.current;
     if (f->items[i]->enclosure) {
       if (!g_hash_table_lookup_extended(c->downloaded_enclosures,
                                         f->items[i]->enclosure->url, NULL,
@@ -343,6 +350,7 @@ int channel_update(channel *c, void *user_data, channel_callback cb,
         }
       }
     }
+  }
 
   if (!opts->no_mark_read) {
     /* Update the RSS last fetched time and save the channel file again. */
@@ -360,6 +368,41 @@ int channel_update(channel *c, void *user_data, channel_callback cb,
   return 0;
 }
 
+void _initialize_index(channel_index *index, int num_items, int reverse) {
+  index->ended = 0;
+  index->reverse = reverse;
+  if (reverse) {
+    index->start = num_items -1;
+    index->stop = 0;
+    index->current = num_items;
+  } else {
+    index->start = 0;
+    index->stop = num_items - 1;
+    index->current = -1;
+  }
+}
+
+int _next_index(channel_index *index) {
+  if (index->ended)
+    return 0;
+
+  if (index->reverse) {
+    index->current--;
+    if (index->current < index->stop) {
+      index->current = -1;
+      index->ended = 1;
+    }
+  } else {
+    index->current++;
+    if (index->current > index->stop) {
+      index->current = -1;
+      index->ended = 1;
+    }
+  }
+
+  return index->ended ? 0 : 1;
+}
+
 /* Match the (file) name of an enclosure against a regexp. Letters
    in the pattern match both upper and lower case letters if
    'caseless' is TRUE. Returns TRUE if the pattern matches, FALSE

src/channel.h

@@ -60,12 +60,21 @@ typedef struct _option_info {
   int no_download;
   int no_mark_read;
   int first_only;
+  int reverse;
   int resume;
   enclosure_filter *filter;
   int debug;
   int show_progress_bar;
 } option_info;
 
+typedef struct _channel_index {
+  int start;
+  int stop;
+  int reverse;
+  int current;
+  int ended;
+} channel_index;
+
 typedef void (*channel_callback)(void *user_data, channel_action action,
                                  channel_info *channel_info,
                                  enclosure *enclosure, const char *filename);