@matheusbsbs / matheus-bagliano / commits / 7146e66f08

tree-walk: finally switch over tree descriptors to contain a pre-parsed entry

This continues 4651ece8 (Switch over tree descriptors to contain a pre-parsed entry) and moves the only rest computational part mode = canon_mode(mode) from tree_entry_extract() to tree entry decode phase - to decode_tree_entry(). The reason to do it, is that canon_mode() is at least 2 conditional jumps for regular files, and that could be noticeable should canon_mode() be invoked several times. That does not matter for current Git codebase, where typical tree traversal is while (t->size) { sha1 = tree_entry_extract(t, &path, &mode); ... update_tree_entry(t); } i.e. we do t -> sha1,path.mode "extraction" only once per entry. In such cases, it does not matter performance-wise, where that mode canonicalization is done - either once in tree_entry_extract(), or once in decode_tree_entry() called by update_tree_entry() - it is approximately the same. But for future code, which could need to work with several tree_desc's in parallel, it could be handy to operate on tree_desc descriptors, and do "extracts" only when needed, or at all, access only relevant part of it through structure fields directly. And for such situations, having canon_mode() be done once in decode phase is better - we won't need to pay the performance price of 2 extra conditional jumps on every t->mode access. So let's move mode canonicalization to decode_tree_entry(). That was the final bit. Now after tree entry is decoded, it is fully ready and could be accessed either directly via field, or through tree_entry_extract() which this time got really "totally trivial". Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Kirill Smelkov committed Feb 6, 2014 at 15:36 UTC 7146e66f0861c720f9b32dc9d80ab80495a33e43

2 files changed +2 -2

tree-walk.c

+1 -1

@@ -37,7 +37,7 @@ static void decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned

38 /* Initialize the descriptor entry */

39 desc->entry.path = path;

40 - desc->entry.mode = mode;

40 + desc->entry.mode = canon_mode(mode);

41 desc->entry.sha1 = (const unsigned char *)(path + len);

42 }

tree-walk.h

+1 -1

@@ -16,7 +16,7 @@ struct tree_desc {

16 static inline const unsigned char *tree_entry_extract(struct tree_desc *desc, const char **pathp, unsigned int *modep)

17 {

18 *pathp = desc->entry.path;

19 - *modep = canon_mode(desc->entry.mode);

19 + *modep = desc->entry.mode;

20 return desc->entry.sha1;

21 }