Teach fast-import to import subtrees named by tree id
[gitweb.git] / tree-walk.c
index a0fe88c55d2a5063c2367fcff1999d959b6d4909..67a9a0c5a5bf7d7125765679318cfcd68c160da7 100644 (file)
@@ -60,13 +60,6 @@ void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1)
        return buf;
 }
 
-static int entry_compare(struct name_entry *a, struct name_entry *b)
-{
-       return df_name_compare(
-                       a->path, tree_entry_len(a->path, a->sha1), a->mode,
-                       b->path, tree_entry_len(b->path, b->sha1), b->mode);
-}
-
 static void entry_clear(struct name_entry *a)
 {
        memset(a, 0, sizeof(*a));
@@ -138,66 +131,264 @@ char *make_traverse_path(char *path, const struct traverse_info *info, const str
        return path;
 }
 
+struct tree_desc_skip {
+       struct tree_desc_skip *prev;
+       const void *ptr;
+};
+
+struct tree_desc_x {
+       struct tree_desc d;
+       struct tree_desc_skip *skip;
+};
+
+static int name_compare(const char *a, int a_len,
+                       const char *b, int b_len)
+{
+       int len = (a_len < b_len) ? a_len : b_len;
+       int cmp = memcmp(a, b, len);
+       if (cmp)
+               return cmp;
+       return (a_len - b_len);
+}
+
+static int check_entry_match(const char *a, int a_len, const char *b, int b_len)
+{
+       /*
+        * The caller wants to pick *a* from a tree or nothing.
+        * We are looking at *b* in a tree.
+        *
+        * (0) If a and b are the same name, we are trivially happy.
+        *
+        * There are three possibilities where *a* could be hiding
+        * behind *b*.
+        *
+        * (1) *a* == "t",   *b* == "ab"  i.e. *b* sorts earlier than *a* no
+        *                                matter what.
+        * (2) *a* == "t",   *b* == "t-2" and "t" is a subtree in the tree;
+        * (3) *a* == "t-2", *b* == "t"   and "t-2" is a blob in the tree.
+        *
+        * Otherwise we know *a* won't appear in the tree without
+        * scanning further.
+        */
+
+       int cmp = name_compare(a, a_len, b, b_len);
+
+       /* Most common case first -- reading sync'd trees */
+       if (!cmp)
+               return cmp;
+
+       if (0 < cmp) {
+               /* a comes after b; it does not matter if it is case (3)
+               if (b_len < a_len && !memcmp(a, b, b_len) && a[b_len] < '/')
+                       return 1;
+               */
+               return 1; /* keep looking */
+       }
+
+       /* b comes after a; are we looking at case (2)? */
+       if (a_len < b_len && !memcmp(a, b, a_len) && b[a_len] < '/')
+               return 1; /* keep looking */
+
+       return -1; /* a cannot appear in the tree */
+}
+
+/*
+ * From the extended tree_desc, extract the first name entry, while
+ * paying attention to the candidate "first" name.  Most importantly,
+ * when looking for an entry, if there are entries that sorts earlier
+ * in the tree object representation than that name, skip them and
+ * process the named entry first.  We will remember that we haven't
+ * processed the first entry yet, and in the later call skip the
+ * entry we processed early when update_extended_entry() is called.
+ *
+ * E.g. if the underlying tree object has these entries:
+ *
+ *    blob    "t-1"
+ *    blob    "t-2"
+ *    tree    "t"
+ *    blob    "t=1"
+ *
+ * and the "first" asks for "t", remember that we still need to
+ * process "t-1" and "t-2" but extract "t".  After processing the
+ * entry "t" from this call, the caller will let us know by calling
+ * update_extended_entry() that we can remember "t" has been processed
+ * already.
+ */
+
+static void extended_entry_extract(struct tree_desc_x *t,
+                                  struct name_entry *a,
+                                  const char *first,
+                                  int first_len)
+{
+       const char *path;
+       int len;
+       struct tree_desc probe;
+       struct tree_desc_skip *skip;
+
+       /*
+        * Extract the first entry from the tree_desc, but skip the
+        * ones that we already returned in earlier rounds.
+        */
+       while (1) {
+               if (!t->d.size) {
+                       entry_clear(a);
+                       break; /* not found */
+               }
+               entry_extract(&t->d, a);
+               for (skip = t->skip; skip; skip = skip->prev)
+                       if (a->path == skip->ptr)
+                               break; /* found */
+               if (!skip)
+                       break;
+               /* We have processed this entry already. */
+               update_tree_entry(&t->d);
+       }
+
+       if (!first || !a->path)
+               return;
+
+       /*
+        * The caller wants "first" from this tree, or nothing.
+        */
+       path = a->path;
+       len = tree_entry_len(a->path, a->sha1);
+       switch (check_entry_match(first, first_len, path, len)) {
+       case -1:
+               entry_clear(a);
+       case 0:
+               return;
+       default:
+               break;
+       }
+
+       /*
+        * We need to look-ahead -- we suspect that a subtree whose
+        * name is "first" may be hiding behind the current entry "path".
+        */
+       probe = t->d;
+       while (probe.size) {
+               entry_extract(&probe, a);
+               path = a->path;
+               len = tree_entry_len(a->path, a->sha1);
+               switch (check_entry_match(first, first_len, path, len)) {
+               case -1:
+                       entry_clear(a);
+               case 0:
+                       return;
+               default:
+                       update_tree_entry(&probe);
+                       break;
+               }
+               /* keep looking */
+       }
+       entry_clear(a);
+}
+
+static void update_extended_entry(struct tree_desc_x *t, struct name_entry *a)
+{
+       if (t->d.entry.path == a->path) {
+               update_tree_entry(&t->d);
+       } else {
+               /* we have returned this entry early */
+               struct tree_desc_skip *skip = xmalloc(sizeof(*skip));
+               skip->ptr = a->path;
+               skip->prev = t->skip;
+               t->skip = skip;
+       }
+}
+
+static void free_extended_entry(struct tree_desc_x *t)
+{
+       struct tree_desc_skip *p, *s;
+
+       for (s = t->skip; s; s = p) {
+               p = s->prev;
+               free(s);
+       }
+}
+
 int traverse_trees(int n, struct tree_desc *t, struct traverse_info *info)
 {
        int ret = 0;
        struct name_entry *entry = xmalloc(n*sizeof(*entry));
+       int i;
+       struct tree_desc_x *tx = xcalloc(n, sizeof(*tx));
+
+       for (i = 0; i < n; i++)
+               tx[i].d = t[i];
 
        for (;;) {
-               unsigned long mask = 0;
-               unsigned long dirmask = 0;
-               int i, last;
+               unsigned long mask, dirmask;
+               const char *first = NULL;
+               int first_len = 0;
+               struct name_entry *e;
+               int len;
 
-               last = -1;
                for (i = 0; i < n; i++) {
-                       if (!t[i].size)
+                       e = entry + i;
+                       extended_entry_extract(tx + i, e, NULL, 0);
+               }
+
+               /*
+                * A tree may have "t-2" at the current location even
+                * though it may have "t" that is a subtree behind it,
+                * and another tree may return "t".  We want to grab
+                * all "t" from all trees to match in such a case.
+                */
+               for (i = 0; i < n; i++) {
+                       e = entry + i;
+                       if (!e->path)
                                continue;
-                       entry_extract(t+i, entry+i);
-                       if (last >= 0) {
-                               int cmp = entry_compare(entry+i, entry+last);
-
-                               /*
-                                * Is the new name bigger than the old one?
-                                * Ignore it
-                                */
-                               if (cmp > 0)
+                       len = tree_entry_len(e->path, e->sha1);
+                       if (!first) {
+                               first = e->path;
+                               first_len = len;
+                               continue;
+                       }
+                       if (name_compare(e->path, len, first, first_len) < 0) {
+                               first = e->path;
+                               first_len = len;
+                       }
+               }
+
+               if (first) {
+                       for (i = 0; i < n; i++) {
+                               e = entry + i;
+                               extended_entry_extract(tx + i, e, first, first_len);
+                               /* Cull the ones that are not the earliest */
+                               if (!e->path)
                                        continue;
-                               /*
-                                * Is the new name smaller than the old one?
-                                * Ignore all old ones
-                                */
-                               if (cmp < 0)
-                                       mask = 0;
+                               len = tree_entry_len(e->path, e->sha1);
+                               if (name_compare(e->path, len, first, first_len))
+                                       entry_clear(e);
                        }
+               }
+
+               /* Now we have in entry[i] the earliest name from the trees */
+               mask = 0;
+               dirmask = 0;
+               for (i = 0; i < n; i++) {
+                       if (!entry[i].path)
+                               continue;
                        mask |= 1ul << i;
                        if (S_ISDIR(entry[i].mode))
                                dirmask |= 1ul << i;
-                       last = i;
                }
                if (!mask)
                        break;
-               dirmask &= mask;
-
-               /*
-                * Clear all the unused name-entries.
-                */
-               for (i = 0; i < n; i++) {
-                       if (mask & (1ul << i))
-                               continue;
-                       entry_clear(entry + i);
-               }
                ret = info->fn(n, mask, dirmask, entry, info);
                if (ret < 0)
                        break;
-               if (ret)
-                       mask &= ret;
+               mask &= ret;
                ret = 0;
-               for (i = 0; i < n; i++) {
+               for (i = 0; i < n; i++)
                        if (mask & (1ul << i))
-                               update_tree_entry(t + i);
-               }
+                               update_extended_entry(tx + i, entry + i);
        }
        free(entry);
+       for (i = 0; i < n; i++)
+               free_extended_entry(tx + i);
+       free(tx);
        return ret;
 }