Switch over tree descriptors to contain a pre-parsed entry

This makes the tree descriptor contain a "struct name_entry" as part of
it, and it gets filled in so that it always contains a valid entry. On
some benchmarks, it improves performance by up to 15%.

That makes tree entry "extract" trivial, and means that we only actually
need to decode each tree entry just once: we decode the first one when
we initialize the tree descriptor, and each subsequent one when doing
"update_tree_entry()".  In particular, this means that we don't need to
do strlen() both at extract time _and_ at update time.

Finally, it also allows more sharing of code (entry_extract(), that
wanted a "struct name_entry", just got totally trivial, along with the
"tree_entry()" function).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/tree-walk.c b/tree-walk.c
index c65492c02d5e37840bbaed9535b93404482b90a1..cbb24eb3f663cd0370f528d983a2266a55b91c4f 100644 (file)
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -2,10 +2,42 @@
 #include "tree-walk.h"
 #include "tree.h"
 
+static const char *get_mode(const char *str, unsigned int *modep)
+{
+       unsigned char c;
+       unsigned int mode = 0;
+
+       while ((c = *str++) != ' ') {
+               if (c < '0' || c > '7')
+                       return NULL;
+               mode = (mode << 3) + (c - '0');
+       }
+       *modep = mode;
+       return str;
+}
+
+static void decode_tree_entry(struct tree_desc *desc, const void *buf, unsigned long size)
+{
+       const char *path;
+       unsigned int mode, len;
+
+       path = get_mode(buf, &mode);
+       if (!path)
+               die("corrupt tree file");
+       len = strlen(path) + 1;
+
+       /* Initialize the descriptor entry */
+       desc->entry.path = path;
+       desc->entry.mode = mode;
+       desc->entry.sha1 = (const unsigned char *)(path + len);
+}
+
 void init_tree_desc(struct tree_desc *desc, const void *buffer, unsigned long size)
 {
        desc->buffer = buffer;
        desc->size = size;
+       if (size)
+               decode_tree_entry(desc, buffer, size);
 }
 
 void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1)
@@ -36,78 +68,33 @@ static void entry_clear(struct name_entry *a)
 
 static void entry_extract(struct tree_desc *t, struct name_entry *a)
 {
-       a->sha1 = tree_entry_extract(t, &a->path, &a->mode);
+       *a = t->entry;
 }
 
 void update_tree_entry(struct tree_desc *desc)
 {
        const void *buf = desc->buffer;
+       const unsigned char *end = desc->entry.sha1 + 20;
        unsigned long size = desc->size;
-       int len = strlen(buf) + 1 + 20;
+       unsigned long len = end - (const unsigned char *)buf;
 
        if (size < len)
                die("corrupt tree file");
-       desc->buffer = (char *) buf + len;
-       desc->size = size - len;
-}
-
-static const char *get_mode(const char *str, unsigned int *modep)
-{
-       unsigned char c;
-       unsigned int mode = 0;
-
-       while ((c = *str++) != ' ') {
-               if (c < '0' || c > '7')
-                       return NULL;
-               mode = (mode << 3) + (c - '0');
-       }
-       *modep = mode;
-       return str;
-}
-
-const unsigned char *tree_entry_extract(struct tree_desc *desc, const char **pathp, unsigned int *modep)
-{
-       const void *tree = desc->buffer;
-       unsigned long size = desc->size;
-       int len = strlen(tree)+1;
-       const unsigned char *sha1 = (unsigned char *) tree + len;
-       const char *path;
-       unsigned int mode;
-
-       path = get_mode(tree, &mode);
-       if (!path || size < len + 20)
-               die("corrupt tree file");
-       *pathp = path;
-       *modep = canon_mode(mode);
-       return sha1;
+       buf = end;
+       size -= len;
+       desc->buffer = buf;
+       desc->size = size;
+       if (size)
+               decode_tree_entry(desc, buf, size);
 }
 
 int tree_entry(struct tree_desc *desc, struct name_entry *entry)
 {
-       const void *tree = desc->buffer;
-       const char *path;
-       unsigned long len, size = desc->size;
-
-       if (!size)
+       if (!desc->size)
                return 0;
 
-       path = get_mode(tree, &entry->mode);
-       if (!path)
-               die("corrupt tree file");
-
-       entry->path = path;
-       len = strlen(path);
-
-       path += len + 1;
-       entry->sha1 = (const unsigned char *) path;
-
-       path += 20;
-       len = path - (char *) tree;
-       if (len > size)
-               die("corrupt tree file");
-
-       desc->buffer = path;
-       desc->size = size - len;
+       *entry = desc->entry;
+       update_tree_entry(desc);
        return 1;
 }
 

diff --git a/tree-walk.h b/tree-walk.h
index ca0c29fb1ac7d6e5c0d364fd27845515de151469..43458cf8ce3a115ee22bb3512749d456c93f783c 100644 (file)
--- a/tree-walk.h
+++ b/tree-walk.h
@@ -1,17 +1,25 @@
 #ifndef TREE_WALK_H
 #define TREE_WALK_H
 
-struct tree_desc {
-       const void *buffer;
-       unsigned int size;
-};
-
 struct name_entry {
        const unsigned char *sha1;
        const char *path;
        unsigned int mode;
 };
 
+struct tree_desc {
+       const void *buffer;
+       struct name_entry entry;
+       unsigned int size;
+};
+
+static inline const unsigned char *tree_entry_extract(struct tree_desc *desc, const char **pathp, unsigned int *modep)
+{
+       *pathp = desc->entry.path;
+       *modep = canon_mode(desc->entry.mode);
+       return desc->entry.sha1;
+}
+
 static inline int tree_entry_len(const char *name, const unsigned char *sha1)
 {
        return (char *)sha1 - (char *)name - 1;