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>

diff --git a/tree-diff.c b/tree-diff.c
index c8275823d0eb976e95b256f2bce5497f45d5da77..f89b9d31e4542724ff44b6f3c3bc6ae3adcaa1a6 100644 (file)
--- a/tree-diff.c
+++ b/tree-diff.c
@@ -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;

diff --git a/tree-walk.c b/tree-walk.c
index 70f899957e8ce511f0f5a470e8b6927d58d1b63e..a4a4e2a9892fb10df32b113ca8b05848d11aff78 100644 (file)
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -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);

diff --git a/tree-walk.h b/tree-walk.h
index e57befa4dac0854906d5b792ce546dab0e6dcdc3..a0d7afd89bee1746912c61164e839daaa05a9b0c 100644 (file)
--- a/tree-walk.h
+++ b/tree-walk.h
@@ -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 *);