ui-repolist: implement lazy caching of repo->mtime

When sorting the list of repositories by their last modification time,
cgit would (in the worst case) invoke fstat(3) four times and open(3)
twice for each callback from qsort(3). This obviously scales very badly.

Now, the calculated modtime for each repo is saved in repo->mtime, thus
keeping the number of stat/open invocations identical for sorted and
unsorted repo-listings.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

3 files changed, 14 insertions, 4 deletions

diff --git a/cgit.h b/cgit.h
index ea90833..c99d337 100644
--- a/cgit.h
+++ b/cgit.h
@@ -16,96 +16,97 @@
 #include <log-tree.h>
 #include <archive.h>
 #include <xdiff/xdiff.h>
 #include <utf8.h>
 
 
 /*
  * Dateformats used on misc. pages
  */
 #define FMT_LONGDATE "%Y-%m-%d %H:%M:%S (%Z)"
 #define FMT_SHORTDATE "%Y-%m-%d"
 #define FMT_ATOMDATE "%Y-%m-%dT%H:%M:%SZ"
 
 
 /*
  * Limits used for relative dates
  */
 #define TM_MIN    60
 #define TM_HOUR  (TM_MIN * 60)
 #define TM_DAY   (TM_HOUR * 24)
 #define TM_WEEK  (TM_DAY * 7)
 #define TM_YEAR  (TM_DAY * 365)
 #define TM_MONTH (TM_YEAR / 12.0)
 
 
 /*
  * Default encoding
  */
 #define PAGE_ENCODING "UTF-8"
 
 typedef void (*configfn)(const char *name, const char *value);
 typedef void (*filepair_fn)(struct diff_filepair *pair);
 typedef void (*linediff_fn)(char *line, int len);
 
 struct cgit_repo {
 	char *url;
 	char *name;
 	char *path;
 	char *desc;
 	char *owner;
 	char *defbranch;
 	char *group;
 	char *module_link;
 	char *readme;
 	char *clone_url;
 	int snapshots;
 	int enable_log_filecount;
 	int enable_log_linecount;
+	time_t mtime;
 };
 
 struct cgit_repolist {
 	int length;
 	int count;
 	struct cgit_repo *repos;
 };
 
 struct commitinfo {
 	struct commit *commit;
 	char *author;
 	char *author_email;
 	unsigned long author_date;
 	char *committer;
 	char *committer_email;
 	unsigned long committer_date;
 	char *subject;
 	char *msg;
 	char *msg_encoding;
 };
 
 struct taginfo {
 	char *tagger;
 	char *tagger_email;
 	unsigned long tagger_date;
 	char *msg;
 };
 
 struct refinfo {
 	const char *refname;
 	struct object *object;
 	union {
 		struct taginfo *tag;
 		struct commitinfo *commit;
 	};
 };
 
 struct reflist {
 	struct refinfo **refs;
 	int alloc;
 	int count;
 };
 
 struct cgit_query {
 	int has_symref;
 	int has_sha1;
 	char *raw;
 	char *repo;
diff --git a/shared.c b/shared.c
index f5875e4..89d1bab 100644
--- a/shared.c
+++ b/shared.c
@@ -15,96 +15,97 @@ int cgit_cmd;
 int chk_zero(int result, char *msg)
 {
 	if (result != 0)
 		die("%s: %s", msg, strerror(errno));
 	return result;
 }
 
 int chk_positive(int result, char *msg)
 {
 	if (result <= 0)
 		die("%s: %s", msg, strerror(errno));
 	return result;
 }
 
 int chk_non_negative(int result, char *msg)
 {
     	if (result < 0)
 	    	die("%s: %s",msg, strerror(errno));
 	return result;
 }
 
 struct cgit_repo *cgit_add_repo(const char *url)
 {
 	struct cgit_repo *ret;
 
 	if (++cgit_repolist.count > cgit_repolist.length) {
 		if (cgit_repolist.length == 0)
 			cgit_repolist.length = 8;
 		else
 			cgit_repolist.length *= 2;
 		cgit_repolist.repos = xrealloc(cgit_repolist.repos,
 					       cgit_repolist.length *
 					       sizeof(struct cgit_repo));
 	}
 
 	ret = &cgit_repolist.repos[cgit_repolist.count-1];
 	ret->url = trim_end(url, '/');
 	ret->name = ret->url;
 	ret->path = NULL;
 	ret->desc = "[no description]";
 	ret->owner = NULL;
 	ret->group = ctx.cfg.repo_group;
 	ret->defbranch = "master";
 	ret->snapshots = ctx.cfg.snapshots;
 	ret->enable_log_filecount = ctx.cfg.enable_log_filecount;
 	ret->enable_log_linecount = ctx.cfg.enable_log_linecount;
 	ret->module_link = ctx.cfg.module_link;
 	ret->readme = NULL;
+	ret->mtime = -1;
 	return ret;
 }
 
 struct cgit_repo *cgit_get_repoinfo(const char *url)
 {
 	int i;
 	struct cgit_repo *repo;
 
 	for (i=0; i<cgit_repolist.count; i++) {
 		repo = &cgit_repolist.repos[i];
 		if (!strcmp(repo->url, url))
 			return repo;
 	}
 	return NULL;
 }
 
 void *cgit_free_commitinfo(struct commitinfo *info)
 {
 	free(info->author);
 	free(info->author_email);
 	free(info->committer);
 	free(info->committer_email);
 	free(info->subject);
 	free(info->msg);
 	free(info->msg_encoding);
 	free(info);
 	return NULL;
 }
 
 char *trim_end(const char *str, char c)
 {
 	int len;
 	char *s, *t;
 
 	if (str == NULL)
 		return NULL;
 	t = (char *)str;
 	len = strlen(t);
 	while(len > 0 && t[len - 1] == c)
 		len--;
 
 	if (len == 0)
 		return NULL;
 
 	c = t[len];
 	t[len] = '\0';
 	s = xstrdup(t);
 	t[len] = c;
diff --git a/ui-repolist.c b/ui-repolist.c
index cf27cb3..aa743bf 100644
--- a/ui-repolist.c
+++ b/ui-repolist.c
@@ -1,95 +1,103 @@
 /* ui-repolist.c: functions for generating the repolist page
  *
  * Copyright (C) 2006 Lars Hjemli
  *
  * Licensed under GNU General Public License v2
  *   (see COPYING for full license text)
  */
 
 #include <time.h>
 
 #include "cgit.h"
 #include "html.h"
 #include "ui-shared.h"
 
 time_t read_agefile(char *path)
 {
 	FILE *f;
 	static char buf[64], buf2[64];
 
 	if (!(f = fopen(path, "r")))
 		return -1;
 	if (fgets(buf, sizeof(buf), f) == NULL)
 		return -1;
 	fclose(f);
 	if (parse_date(buf, buf2, sizeof(buf2)))
 		return strtoul(buf2, NULL, 10);
 	else
 		return 0;
 }
 
 static int get_repo_modtime(const struct cgit_repo *repo, time_t *mtime)
 {
 	char *path;
 	struct stat s;
+	struct cgit_repo *r = (struct cgit_repo *)repo;
 
+	if (repo->mtime != -1) {
+		*mtime = repo->mtime;
+		return 1;
+	}
 	path = fmt("%s/%s", repo->path, ctx.cfg.agefile);
 	if (stat(path, &s) == 0) {
 		*mtime = read_agefile(path);
+		r->mtime = *mtime;
 		return 1;
 	}
 
 	path = fmt("%s/refs/heads/%s", repo->path, repo->defbranch);
-	if (stat(path, &s) == 0) {
+	if (stat(path, &s) == 0)
 		*mtime = s.st_mtime;
-		return 1;
-	}
-	return 0;
+	else
+		*mtime = 0;
+
+	r->mtime = *mtime;
+	return (r->mtime != 0);
 }
 
 static void print_modtime(struct cgit_repo *repo)
 {
 	time_t t;
 	if (get_repo_modtime(repo, &t))
 		cgit_print_age(t, -1, NULL);
 }
 
 int is_match(struct cgit_repo *repo)
 {
 	if (!ctx.qry.search)
 		return 1;
 	if (repo->url && strcasestr(repo->url, ctx.qry.search))
 		return 1;
 	if (repo->name && strcasestr(repo->name, ctx.qry.search))
 		return 1;
 	if (repo->desc && strcasestr(repo->desc, ctx.qry.search))
 		return 1;
 	if (repo->owner && strcasestr(repo->owner, ctx.qry.search))
 		return 1;
 	return 0;
 }
 
 int is_in_url(struct cgit_repo *repo)
 {
 	if (!ctx.qry.url)
 		return 1;
 	if (repo->url && !prefixcmp(repo->url, ctx.qry.url))
 		return 1;
 	return 0;
 }
 
 void print_sort_header(const char *title, const char *sort)
 {
 	htmlf("<th class='left'><a href='./?s=%s", sort);
 	if (ctx.qry.search) {
 		html("&q=");
 		html_url_arg(ctx.qry.search);
 	}
 	htmlf("'>%s</a></th>", title);
 }
 
 void print_header(int columns)
 {
 	html("<tr class='nohover'>");
 	print_sort_header("Name", "name");
 	print_sort_header("Description", "desc");