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Avoid unnecessary strlen() calls 

This is a micro-optimization that grew out of the mailing list discussion
about "strlen()" showing up in profiles.

We used to pass regular C strings around to the low-level tree walking
routines, and while this worked fine, it meant that we needed to call
strlen() on strings that the caller always actually knew the size of
anyway.

So pass the length of the string down wih the string, and avoid
unnecessary calls to strlen(). Also, when extracting a pathname from a
tree entry, use "tree_entry_len()" instead of strlen(), since the length
of the pathname is directly calculable from the decoded tree entry itself
without having to actually do another strlen().

This shaves off another ~5-10% from some loads that are very tree
intensive (notably doing commit filtering by a pathspec).

Signed-off-by: Linus Torvalds  <torvalds@linux-foundation.org>"
Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Linus Torvalds 2007-03-17 20:06:24 -07:00 коммит произвёл Junio C Hamano
Родитель a0cba10847
Коммит 304de2d2d6
3 изменённых файлов: 36 добавлений и 29 удалений
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56
tree-diff.c
Просмотреть файл

@ -5,9 +5,8 @@
#include "diff.h"
#include "tree.h"
static char *malloc_base(const char *base, const char *path, int pathlen)
static char *malloc_base(const char *base, int baselen, const char *path, int pathlen)
{
int baselen = strlen(base);
char *newbase = xmalloc(baselen + pathlen + 2);
memcpy(newbase, base, baselen);
memcpy(newbase + baselen, path, pathlen);
@ -16,9 +15,9 @@ static char *malloc_base(const char *base, const char *path, int pathlen)
}
static void show_entry(struct diff_options *opt, const char *prefix, struct tree_desc *desc,
const char *base);
const char *base, int baselen);
static int compare_tree_entry(struct tree_desc *t1, struct tree_desc *t2, const char *base, struct diff_options *opt)
static int compare_tree_entry(struct tree_desc *t1, struct tree_desc *t2, const char *base, int baselen, struct diff_options *opt)
{
unsigned mode1, mode2;
const char *path1, *path2;
@ -28,15 +27,15 @@ static int compare_tree_entry(struct tree_desc *t1, struct tree_desc *t2, const
sha1 = tree_entry_extract(t1, &path1, &mode1);
sha2 = tree_entry_extract(t2, &path2, &mode2);
pathlen1 = strlen(path1);
pathlen2 = strlen(path2);
pathlen1 = tree_entry_len(path1, sha1);
pathlen2 = tree_entry_len(path2, sha2);
cmp = base_name_compare(path1, pathlen1, mode1, path2, pathlen2, mode2);
if (cmp < 0) {
show_entry(opt, "-", t1, base);
show_entry(opt, "-", t1, base, baselen);
return -1;
}
if (cmp > 0) {
show_entry(opt, "+", t2, base);
show_entry(opt, "+", t2, base, baselen);
return 1;
}
if (!opt->find_copies_harder && !hashcmp(sha1, sha2) && mode1 == mode2)
@ -47,14 +46,14 @@ static int compare_tree_entry(struct tree_desc *t1, struct tree_desc *t2, const
* file, we need to consider it a remove and an add.
*/
if (S_ISDIR(mode1) != S_ISDIR(mode2)) {
show_entry(opt, "-", t1, base);
show_entry(opt, "+", t2, base);
show_entry(opt, "-", t1, base, baselen);
show_entry(opt, "+", t2, base, baselen);
return 0;
}
if (opt->recursive && S_ISDIR(mode1)) {
int retval;
char *newbase = malloc_base(base, path1, pathlen1);
char *newbase = malloc_base(base, baselen, path1, pathlen1);
if (opt->tree_in_recursive)
opt->change(opt, mode1, mode2,
sha1, sha2, base, path1);
@ -67,20 +66,20 @@ static int compare_tree_entry(struct tree_desc *t1, struct tree_desc *t2, const
return 0;
}
static int interesting(struct tree_desc *desc, const char *base, struct diff_options *opt)
static int interesting(struct tree_desc *desc, const char *base, int baselen, struct diff_options *opt)
{
const char *path;
const unsigned char *sha1;
unsigned mode;
int i;
int baselen, pathlen;
int pathlen;
if (!opt->nr_paths)
return 1;
(void)tree_entry_extract(desc, &path, &mode);
sha1 = tree_entry_extract(desc, &path, &mode);
pathlen = strlen(path);
baselen = strlen(base);
pathlen = tree_entry_len(path, sha1);
for (i=0; i < opt->nr_paths; i++) {
const char *match = opt->paths[i];
@ -121,18 +120,18 @@ static int interesting(struct tree_desc *desc, const char *base, struct diff_opt
}
/* A whole sub-tree went away or appeared */
static void show_tree(struct diff_options *opt, const char *prefix, struct tree_desc *desc, const char *base)
static void show_tree(struct diff_options *opt, const char *prefix, struct tree_desc *desc, const char *base, int baselen)
{
while (desc->size) {
if (interesting(desc, base, opt))
show_entry(opt, prefix, desc, base);
if (interesting(desc, base, baselen, opt))
show_entry(opt, prefix, desc, base, baselen);
update_tree_entry(desc);
}
}
/* A file entry went away or appeared */
static void show_entry(struct diff_options *opt, const char *prefix, struct tree_desc *desc,
const char *base)
const char *base, int baselen)
{
unsigned mode;
const char *path;
@ -140,7 +139,8 @@ static void show_entry(struct diff_options *opt, const char *prefix, struct tree
if (opt->recursive && S_ISDIR(mode)) {
enum object_type type;
char *newbase = malloc_base(base, path, strlen(path));
int pathlen = tree_entry_len(path, sha1);
char *newbase = malloc_base(base, baselen, path, pathlen);
struct tree_desc inner;
void *tree;
@ -149,7 +149,7 @@ static void show_entry(struct diff_options *opt, const char *prefix, struct tree
die("corrupt tree sha %s", sha1_to_hex(sha1));
inner.buf = tree;
show_tree(opt, prefix, &inner, newbase);
show_tree(opt, prefix, &inner, newbase, baselen + 1 + pathlen);
free(tree);
free(newbase);
@ -160,26 +160,28 @@ static void show_entry(struct diff_options *opt, const char *prefix, struct tree
int diff_tree(struct tree_desc *t1, struct tree_desc *t2, const char *base, struct diff_options *opt)
{
int baselen = strlen(base);
while (t1->size | t2->size) {
if (opt->nr_paths && t1->size && !interesting(t1, base, opt)) {
if (opt->nr_paths && t1->size && !interesting(t1, base, baselen, opt)) {
update_tree_entry(t1);
continue;
}
if (opt->nr_paths && t2->size && !interesting(t2, base, opt)) {
if (opt->nr_paths && t2->size && !interesting(t2, base, baselen, opt)) {
update_tree_entry(t2);
continue;
}
if (!t1->size) {
show_entry(opt, "+", t2, base);
show_entry(opt, "+", t2, base, baselen);
update_tree_entry(t2);
continue;
}
if (!t2->size) {
show_entry(opt, "-", t1, base);
show_entry(opt, "-", t1, base, baselen);
update_tree_entry(t1);
continue;
}
switch (compare_tree_entry(t1, t2, base, opt)) {
switch (compare_tree_entry(t1, t2, base, baselen, opt)) {
case -1:
update_tree_entry(t1);
continue;

4
tree-walk.c
Просмотреть файл

@ -32,7 +32,7 @@ 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->pathlen = strlen(a->path);
a->pathlen = tree_entry_len(a->path, a->sha1);
}
void update_tree_entry(struct tree_desc *desc)
@ -169,7 +169,7 @@ static int find_tree_entry(struct tree_desc *t, const char *name, unsigned char
sha1 = tree_entry_extract(t, &entry, mode);
update_tree_entry(t);
entrylen = strlen(entry);
entrylen = tree_entry_len(entry, sha1);
if (entrylen > namelen)
continue;
cmp = memcmp(name, entry, entrylen);

5
tree-walk.h
Просмотреть файл

@ -13,6 +13,11 @@ struct name_entry {
int pathlen;
};
static inline int tree_entry_len(const char *name, const unsigned char *sha1)
{
return (char *)sha1 - (char *)name - 1;
}
void update_tree_entry(struct tree_desc *);
const unsigned char *tree_entry_extract(struct tree_desc *, const char **, unsigned int *);