unpack-trees.c: prepare for looking ahead in the index

This prepares but does not yet implement a look-ahead in the index entries
when traverse-trees.c decides to give us tree entries in an order that
does not match what is in the index.

A case where a look-ahead in the index is necessary happens when merging
branch B into branch A while the index matches the current branch A, using
a tree O as their common ancestor, and these three trees looks like this:

   O        A       B
   t                t
   t-i      t-i     t-i
   t-j      t-j
            t/1
            t/2

The traverse_trees() function gets "t", "t-i" and "t" from trees O, A and
B first, and notices that A may have a matching "t" behind "t-i" and "t-j"
(indeed it does), and tells A to give that entry instead.  After unpacking
blob "t" from tree B (as it hasn't changed since O in B and A removed it,
it will result in its removal), it descends into directory "t/".

The side that walked index in parallel to the tree traversal used to be
implemented with one pointer, o->pos, that points at the next index entry
to be processed.  When this happens, the pointer o->pos still points at
"t-i" that is the first entry.  We should be able to skip "t-i" and "t-j"
and locate "t/1" from the index while the recursive invocation of
traverse_trees() walks and match entries found there, and later come back
to process "t-i".

While that look-ahead is not implemented yet, this adds a flag bit,
CE_UNPACKED, to mark the entries in the index that has already been
processed.  o->pos pointer has been renamed to o->cache_bottom and it
points at the first entry that may still need to be processed.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/cache.h b/cache.h
index bf468e52352c193b355222b718d9f5125c26052c..9a9596386d704742ee3f381edd893515f179bcf8 100644 (file)
--- a/cache.h
+++ b/cache.h
@@ -178,6 +178,8 @@ struct cache_entry {
 #define CE_HASHED    (0x100000)
 #define CE_UNHASHED  (0x200000)
 
+#define CE_UNPACKED  (0x1000000)
+
 /*
  * Extended on-disk flags
  */

diff --git a/diff-lib.c b/diff-lib.c
index adf1c5fdee2bc836f03eaa89160573973bb46a67..f759917d33ea174800b57e34c5f192ad43977f49 100644 (file)
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -359,21 +359,6 @@ static void do_oneway_diff(struct unpack_trees_options *o,
        show_modified(revs, tree, idx, 1, cached, match_missing);
 }
 
-static inline void skip_same_name(struct cache_entry *ce, struct unpack_trees_options *o)
-{
-       int len = ce_namelen(ce);
-       const struct index_state *index = o->src_index;
-
-       while (o->pos < index->cache_nr) {
-               struct cache_entry *next = index->cache[o->pos];
-               if (len != ce_namelen(next))
-                       break;
-               if (memcmp(ce->name, next->name, len))
-                       break;
-               o->pos++;
-       }
-}
-
 /*
  * The unpack_trees() interface is designed for merging, so
  * the different source entries are designed primarily for
@@ -395,9 +380,6 @@ static int oneway_diff(struct cache_entry **src, struct unpack_trees_options *o)
        struct cache_entry *tree = src[1];
        struct rev_info *revs = o->unpack_data;
 
-       if (idx && ce_stage(idx))
-               skip_same_name(idx, o);
-
        /*
         * Unpack-trees generates a DF/conflict entry if
         * there was a directory in the index and a tree

diff --git a/unpack-trees.c b/unpack-trees.c
index 7413ff0b93c92efd46c4eadce4016b41a2415957..685adb4b7723a510fc90f09c1a65a1382bff8c74 100644 (file)
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -126,18 +126,109 @@ static inline int call_unpack_fn(struct cache_entry **src, struct unpack_trees_o
        return ret;
 }
 
-static int unpack_index_entry(struct cache_entry *ce, struct unpack_trees_options *o)
+static void mark_ce_used(struct cache_entry *ce, struct unpack_trees_options *o)
+{
+       ce->ce_flags |= CE_UNPACKED;
+
+       if (o->cache_bottom < o->src_index->cache_nr &&
+           o->src_index->cache[o->cache_bottom] == ce) {
+               int bottom = o->cache_bottom;
+               while (bottom < o->src_index->cache_nr &&
+                      o->src_index->cache[bottom]->ce_flags & CE_UNPACKED)
+                       bottom++;
+               o->cache_bottom = bottom;
+       }
+}
+
+static void mark_all_ce_unused(struct index_state *index)
+{
+       int i;
+       for (i = 0; i < index->cache_nr; i++)
+               index->cache[i]->ce_flags &= ~CE_UNPACKED;
+}
+
+static int locate_in_src_index(struct cache_entry *ce,
+                              struct unpack_trees_options *o)
+{
+       struct index_state *index = o->src_index;
+       int len = ce_namelen(ce);
+       int pos = index_name_pos(index, ce->name, len);
+       if (pos < 0)
+               pos = -1 - pos;
+       return pos;
+}
+
+/*
+ * We call unpack_index_entry() with an unmerged cache entry
+ * only in diff-index, and it wants a single callback.  Skip
+ * the other unmerged entry with the same name.
+ */
+static void mark_ce_used_same_name(struct cache_entry *ce,
+                                  struct unpack_trees_options *o)
+{
+       struct index_state *index = o->src_index;
+       int len = ce_namelen(ce);
+       int pos;
+
+       for (pos = locate_in_src_index(ce, o); pos < index->cache_nr; pos++) {
+               struct cache_entry *next = index->cache[pos];
+               if (len != ce_namelen(next) ||
+                   memcmp(ce->name, next->name, len))
+                       break;
+               mark_ce_used(next, o);
+       }
+}
+
+static struct cache_entry *next_cache_entry(struct unpack_trees_options *o)
+{
+       const struct index_state *index = o->src_index;
+       int pos = o->cache_bottom;
+
+       while (pos < index->cache_nr) {
+               struct cache_entry *ce = index->cache[pos];
+               if (!(ce->ce_flags & CE_UNPACKED))
+                       return ce;
+               pos++;
+       }
+       return NULL;
+}
+
+static void add_same_unmerged(struct cache_entry *ce,
+                             struct unpack_trees_options *o)
+{
+       struct index_state *index = o->src_index;
+       int len = ce_namelen(ce);
+       int pos = index_name_pos(index, ce->name, len);
+
+       if (0 <= pos)
+               die("programming error in a caller of mark_ce_used_same_name");
+       for (pos = -pos - 1; pos < index->cache_nr; pos++) {
+               struct cache_entry *next = index->cache[pos];
+               if (len != ce_namelen(next) ||
+                   memcmp(ce->name, next->name, len))
+                       break;
+               add_entry(o, next, 0, 0);
+               mark_ce_used(next, o);
+       }
+}
+
+static int unpack_index_entry(struct cache_entry *ce,
+                             struct unpack_trees_options *o)
 {
        struct cache_entry *src[5] = { ce, NULL, };
+       int ret;
 
-       o->pos++;
+       mark_ce_used(ce, o);
        if (ce_stage(ce)) {
                if (o->skip_unmerged) {
                        add_entry(o, ce, 0, 0);
                        return 0;
                }
        }
-       return call_unpack_fn(src, o);
+       ret = call_unpack_fn(src, o);
+       if (ce_stage(ce))
+               mark_ce_used_same_name(ce, o);
+       return ret;
 }
 
 static int traverse_trees_recursive(int n, unsigned long dirmask, unsigned long df_conflicts, struct name_entry *names, struct traverse_info *info)
@@ -212,6 +303,20 @@ static int compare_entry(const struct cache_entry *ce, const struct traverse_inf
        return ce_namelen(ce) > traverse_path_len(info, n);
 }
 
+static int ce_in_traverse_path(const struct cache_entry *ce,
+                              const struct traverse_info *info)
+{
+       if (!info->prev)
+               return 1;
+       if (do_compare_entry(ce, info->prev, &info->name))
+               return 0;
+       /*
+        * If ce (blob) is the same name as the path (which is a tree
+        * we will be descending into), it won't be inside it.
+        */
+       return (info->pathlen < ce_namelen(ce));
+}
+
 static struct cache_entry *create_ce_entry(const struct traverse_info *info, const struct name_entry *n, int stage)
 {
        int len = traverse_path_len(info, n);
@@ -300,23 +405,27 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
 
        /* Are we supposed to look at the index too? */
        if (o->merge) {
-               while (o->pos < o->src_index->cache_nr) {
-                       struct cache_entry *ce = o->src_index->cache[o->pos];
-                       int cmp = compare_entry(ce, info, p);
+               while (1) {
+                       struct cache_entry *ce = next_cache_entry(o);
+                       int cmp;
+                       if (!ce)
+                               break;
+                       cmp = compare_entry(ce, info, p);
                        if (cmp < 0) {
                                if (unpack_index_entry(ce, o) < 0)
                                        return unpack_failed(o, NULL);
                                continue;
                        }
                        if (!cmp) {
-                               o->pos++;
                                if (ce_stage(ce)) {
                                        /*
-                                        * If we skip unmerged index entries, we'll skip this
-                                        * entry *and* the tree entries associated with it!
+                                        * If we skip unmerged index
+                                        * entries, we'll skip this
+                                        * entry *and* the tree
+                                        * entries associated with it!
                                         */
                                        if (o->skip_unmerged) {
-                                               add_entry(o, ce, 0, 0);
+                                               add_same_unmerged(ce, o);
                                                return mask;
                                        }
                                }
@@ -329,6 +438,13 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
        if (unpack_nondirectories(n, mask, dirmask, src, names, info) < 0)
                return -1;
 
+       if (src[0]) {
+               if (ce_stage(src[0]))
+                       mark_ce_used_same_name(src[0], o);
+               else
+                       mark_ce_used(src[0], o);
+       }
+
        /* Now handle any directories.. */
        if (dirmask) {
                unsigned long conflicts = mask & ~dirmask;
@@ -345,11 +461,13 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
                        matches = cache_tree_matches_traversal(o->src_index->cache_tree,
                                                               names, info);
                        /*
-                        * Everything under the name matches.  Adjust o->pos to
-                        * skip the entire hierarchy.
+                        * Everything under the name matches; skip the
+                        * entire hierarchy.  diff_index_cached codepath
+                        * special cases D/F conflicts in such a way that
+                        * it does not do any look-ahead, so this is safe.
                         */
                        if (matches) {
-                               o->pos += matches;
+                               o->cache_bottom += matches;
                                return mask;
                        }
                }
@@ -382,11 +500,10 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 
        memset(&o->result, 0, sizeof(o->result));
        o->result.initialized = 1;
-       if (o->src_index) {
-               o->result.timestamp.sec = o->src_index->timestamp.sec;
-               o->result.timestamp.nsec = o->src_index->timestamp.nsec;
-       }
+       o->result.timestamp.sec = o->src_index->timestamp.sec;
+       o->result.timestamp.nsec = o->src_index->timestamp.nsec;
        o->merge_size = len;
+       mark_all_ce_unused(o->src_index);
 
        if (!dfc)
                dfc = xcalloc(1, cache_entry_size(0));
@@ -400,18 +517,38 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
                info.fn = unpack_callback;
                info.data = o;
 
+               if (o->prefix) {
+                       /*
+                        * Unpack existing index entries that sort before the
+                        * prefix the tree is spliced into.  Note that o->merge
+                        * is always true in this case.
+                        */
+                       while (1) {
+                               struct cache_entry *ce = next_cache_entry(o);
+                               if (!ce)
+                                       break;
+                               if (ce_in_traverse_path(ce, &info))
+                                       break;
+                               if (unpack_index_entry(ce, o) < 0)
+                                       goto return_failed;
+                       }
+               }
+
                if (traverse_trees(len, t, &info) < 0)
-                       return unpack_failed(o, NULL);
+                       goto return_failed;
        }
 
        /* Any left-over entries in the index? */
        if (o->merge) {
-               while (o->pos < o->src_index->cache_nr) {
-                       struct cache_entry *ce = o->src_index->cache[o->pos];
+               while (1) {
+                       struct cache_entry *ce = next_cache_entry(o);
+                       if (!ce)
+                               break;
                        if (unpack_index_entry(ce, o) < 0)
-                               return unpack_failed(o, NULL);
+                               goto return_failed;
                }
        }
+       mark_all_ce_unused(o->src_index);
 
        if (o->trivial_merges_only && o->nontrivial_merge)
                return unpack_failed(o, "Merge requires file-level merging");
@@ -421,6 +558,10 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
        if (o->dst_index)
                *o->dst_index = o->result;
        return ret;
+
+return_failed:
+       mark_all_ce_unused(o->src_index);
+       return unpack_failed(o, NULL);
 }
 
 /* Here come the merge functions */
@@ -522,7 +663,9 @@ static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
         * in that directory.
         */
        namelen = strlen(ce->name);
-       for (i = o->pos; i < o->src_index->cache_nr; i++) {
+       for (i = locate_in_src_index(ce, o);
+            i < o->src_index->cache_nr;
+            i++) {
                struct cache_entry *ce2 = o->src_index->cache[i];
                int len = ce_namelen(ce2);
                if (len < namelen ||
@@ -530,12 +673,14 @@ static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
                    ce2->name[namelen] != '/')
                        break;
                /*
-                * ce2->name is an entry in the subdirectory.
+                * ce2->name is an entry in the subdirectory to be
+                * removed.
                 */
                if (!ce_stage(ce2)) {
                        if (verify_uptodate(ce2, o))
                                return -1;
                        add_entry(o, ce2, CE_REMOVE, 0);
+                       mark_ce_used(ce2, o);
                }
                cnt++;
        }
@@ -591,7 +736,6 @@ static int verify_absent(struct cache_entry *ce, const char *action,
                return 0;
 
        if (!lstat(ce->name, &st)) {
-               int ret;
                int dtype = ce_to_dtype(ce);
                struct cache_entry *result;
 
@@ -619,28 +763,8 @@ static int verify_absent(struct cache_entry *ce, const char *action,
                         * files that are in "foo/" we would lose
                         * them.
                         */
-                       ret = verify_clean_subdirectory(ce, action, o);
-                       if (ret < 0)
-                               return ret;
-
-                       /*
-                        * If this removed entries from the index,
-                        * what that means is:
-                        *
-                        * (1) the caller unpack_callback() saw path/foo
-                        * in the index, and it has not removed it because
-                        * it thinks it is handling 'path' as blob with
-                        * D/F conflict;
-                        * (2) we will return "ok, we placed a merged entry
-                        * in the index" which would cause o->pos to be
-                        * incremented by one;
-                        * (3) however, original o->pos now has 'path/foo'
-                        * marked with "to be removed".
-                        *
-                        * We need to increment it by the number of
-                        * deleted entries here.
-                        */
-                       o->pos += ret;
+                       if (verify_clean_subdirectory(ce, action, o) < 0)
+                               return -1;
                        return 0;
                }
 

diff --git a/unpack-trees.h b/unpack-trees.h
index d19df44f4070ca1bda29382e56fbced53aacd994..9a0733ea8545efd33e1d608255612080afc670e7 100644 (file)
--- a/unpack-trees.h
+++ b/unpack-trees.h
@@ -30,7 +30,7 @@ struct unpack_trees_options {
                     diff_index_cached,
                     gently;
        const char *prefix;
-       int pos;
+       int cache_bottom;
        struct dir_struct *dir;
        merge_fn_t fn;
        struct unpack_trees_error_msgs msgs;