Use a binary heap instead of an unsorted list to track unvisited

entries in ISO images.  This makes "tar tvf" up to 10 times faster.

SVN-Revision: 1419

diff --git a/libarchive/archive_read_support_format_iso9660.c b/libarchive/archive_read_support_format_iso9660.c
index a6ae2cf7530265731492b4c132b3d73b7071e5fa..57f51793e899383dabf00d36bc2f7fd91db9b2ef 100644 (file)
--- a/libarchive/archive_read_support_format_iso9660.c
+++ b/libarchive/archive_read_support_format_iso9660.c
@@ -1158,6 +1158,9 @@ parse_file_info(struct iso9660 *iso9660, struct file_info *parent,
 static void
 add_entry(struct iso9660 *iso9660, struct file_info *file)
 {
+       uint64_t file_offset, parent_offset;
+       int hole, parent;
+
        /* Expand our pending files list as necessary. */
        if (iso9660->pending_files_used >= iso9660->pending_files_allocated) {
                struct file_info **new_pending_files;
@@ -1179,7 +1182,25 @@ add_entry(struct iso9660 *iso9660, struct file_info *file)
                iso9660->pending_files_allocated = new_size;
        }
 
-       iso9660->pending_files[iso9660->pending_files_used++] = file;
+       file_offset = file->offset + file->size;
+
+       /*
+        * Start with hole at end, walk it up tree to find insertion point.
+        */
+       hole = iso9660->pending_files_used++;
+       while (hole > 0) {
+               parent = (hole - 1)/2;
+               parent_offset = iso9660->pending_files[parent]->offset
+                   + iso9660->pending_files[parent]->size;
+               if (file_offset >= parent_offset) {
+                       iso9660->pending_files[hole] = file;
+                       return;
+               }
+               // Move parent into hole <==> move hole up tree.
+               iso9660->pending_files[hole] = iso9660->pending_files[parent];
+               hole = parent;
+       }
+       iso9660->pending_files[0] = file;
 }
 
 static void
@@ -1685,37 +1706,52 @@ next_entry_seek(struct archive_read *a, struct iso9660 *iso9660,
 static struct file_info *
 next_entry(struct iso9660 *iso9660)
 {
-       int least_index;
-       uint64_t least_end_offset;
-       int i;
-       struct file_info *r;
+       uint64_t a_offset, b_offset, c_offset;
+       int a, b, c;
+       struct file_info *r, *tmp;
 
        if (iso9660->pending_files_used < 1)
                return (NULL);
 
-       /* Assume the first file in the list is the earliest on disk. */
-       least_index = 0;
-       least_end_offset = iso9660->pending_files[0]->offset
-           + iso9660->pending_files[0]->size;
-
-       /* Now, try to find an earlier one. */
-       for (i = 0; i < iso9660->pending_files_used; i++) {
-               /* Use the position of the file *end* as our comparison. */
-               uint64_t end_offset = iso9660->pending_files[i]->offset
-                   + iso9660->pending_files[i]->size;
-               if (iso9660->pending_files[i]->ce_offset > 0
-                   && iso9660->pending_files[i]->ce_offset < iso9660->pending_files[i]->offset)
-                       end_offset = iso9660->pending_files[i]->ce_offset
-                   + iso9660->pending_files[i]->ce_size;
-               if (least_end_offset > end_offset) {
-                       least_index = i;
-                       least_end_offset = end_offset;
+       /*
+        * The first file in the list is the earliest; we'll return this.
+        */
+       r = iso9660->pending_files[0];
+
+       /*
+        * Move the last item in the heap to the root of the tree
+        */
+       iso9660->pending_files[0]
+           = iso9660->pending_files[--iso9660->pending_files_used];
+
+       /*
+        * Rebalance the heap.
+        */
+       a = 0; // Starting element and its offset
+       a_offset = iso9660->pending_files[a]->offset
+           + iso9660->pending_files[a]->size;
+       for (;;) {
+               b = a + a + 1; // First child
+               if (b >= iso9660->pending_files_used)
+                       return (r);
+               b_offset = iso9660->pending_files[b]->offset
+                   + iso9660->pending_files[b]->size;
+               c = b + 1; // Use second child if it is smaller.
+               if (c < iso9660->pending_files_used) {
+                       c_offset = iso9660->pending_files[c]->offset
+                           + iso9660->pending_files[c]->size;
+                       if (c_offset < b_offset) {
+                               b = c;
+                               b_offset = c_offset;
+                       }
                }
+               if (a_offset <= b_offset)
+                       return (r);
+               tmp = iso9660->pending_files[a];
+               iso9660->pending_files[a] = iso9660->pending_files[b];
+               iso9660->pending_files[b] = tmp;
+               a = b;
        }
-       r = iso9660->pending_files[least_index];
-       iso9660->pending_files[least_index]
-           = iso9660->pending_files[--iso9660->pending_files_used];
-       return (r);
 }
 
 static unsigned int