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unpack-trees.c: prepare for looking ahead in the index
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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>
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Junio C Hamano committed Jan 7, 2010
1 parent cee2d6a commit da165f4
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Showing 4 changed files with 173 additions and 65 deletions.
2 changes: 2 additions & 0 deletions cache.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -178,6 +178,8 @@ struct cache_entry {
#define CE_HASHED (0x100000)
#define CE_UNHASHED (0x200000)

#define CE_UNPACKED (0x1000000)

/*
* Extended on-disk flags
*/
Expand Down
18 changes: 0 additions & 18 deletions diff-lib.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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
Expand Down
216 changes: 170 additions & 46 deletions unpack-trees.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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)
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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;
}
}
Expand All @@ -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;
Expand All @@ -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;
}
}
Expand Down Expand Up @@ -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));
Expand All @@ -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");
Expand All @@ -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 */
Expand Down Expand Up @@ -522,20 +663,24 @@ 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 ||
strncmp(ce->name, ce2->name, namelen) ||
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++;
}
Expand Down Expand Up @@ -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;

Expand Down Expand Up @@ -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;
}

Expand Down
2 changes: 1 addition & 1 deletion unpack-trees.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down

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