9 files changed, 353 insertions, 28 deletions

diff --git a/.gitignore b/.gitignore
index 4eaec97..c4c9ac3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 # Files I don't care to see in git-status/commit
 cgit
 *.o
+*~
diff --git a/Makefile b/Makefile
index 4e72b07..243f590 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,9 @@ INSTALL_BIN = /var/www/htdocs/cgit.cgi
 INSTALL_CSS = /var/www/htdocs/cgit.css
 
 EXTLIBS = ../git/libgit.a ../git/xdiff/lib.a -lz -lcrypto
-OBJECTS = cgit.o config.o html.o
+OBJECTS = cgit.o config.o html.o cache.o
+
+CFLAGS += -Wall
 
 all: cgit
 
@@ -15,6 +17,6 @@ clean:
         rm -f cgit *.o
 
 cgit: $(OBJECTS)
-        $(CC) -o cgit $(OBJECTS) $(EXTLIBS)
+        $(CC) $(CFLAGS) -o cgit $(OBJECTS) $(EXTLIBS)
 
 $(OBJECTS): cgit.h git.h
diff --git a/README b/README
new file mode 100644
index 0000000..5917c37
--- /dev/null
+++ b/README
@@ -0,0 +1,54 @@
+Cache algorithm
+===============
+
+Cgit normally returns cached pages when invoked. If there is no cache file, or
+the cache file has expired, it is regenerated. Finally, the cache file is 
+printed on stdout.
+
+When it is decided that a cache file needs to be regenerated, an attempt is 
+made to create a corresponding lockfile. If this fails, the process gives up
+and uses the expired cache file instead.
+
+When there is no cache file for a request, an attempt is made to create a 
+corresponding lockfile. If this fails, the process calls sched_yield(2) before
+restarting the request handling.
+
+In pseudocode:
+
+        name = generate_cache_name(request);
+top:
+        if (!exists(name)) {
+                if (lock_cache(name)) {
+                        generate_cache(request, name);
+                        unlock_cache(name);
+                } else {
+                        sched_yield();
+                        goto top;
+                }
+        } else if (expired(name)) {
+                if (lock_cache(name)) {
+                        generate_cache(request, name);
+                        unlock_cache(name);
+                }
+        }
+        print_file(name);
+
+
+The following options can be set in /etc/cgitrc to control cache behaviour:
+  cache-root:        root directory for cache files
+  cache-root-ttl:    TTL for the repo listing page
+  cache-repo-ttl:    TTL for any repos summary page
+  cache-dynamic-ttl: TTL for pages with symbolic references (not SHA1)
+  cache-static-ttl:  TTL for pages with sha1 references
+
+TTL is specified in minutes, -1 meaning "infinite caching". 
+
+
+Naming of cache files
+---------------------
+Repository listing:  <cachedir>/index.html
+Repository summary:  <cachedir>/<repo>/index.html
+Repository subpage:  <cachedir>/<repo>/<page>/<querystring>.html
+
+The corresponding lock files have a ".lock" suffix.
+
diff --git a/cache.c b/cache.c
new file mode 100644
index 0000000..1be1ea4
--- /dev/null
+++ b/cache.c
@@ -0,0 +1,86 @@
+#include "cgit.h"
+
+const int NOLOCK = -1;
+
+int cache_lookup(struct cacheitem *item)
+{
+        if (!cgit_query_repo) {
+                item->name = xstrdup(fmt("%s/index.html", cgit_cache_root));
+                item->ttl = cgit_cache_root_ttl;
+        } else if (!cgit_query_page) {
+                item->name = xstrdup(fmt("%s/%s/index.html", cgit_cache_root, 
+                           cgit_query_repo));
+                item->ttl = cgit_cache_repo_ttl;
+        } else {
+                item->name = xstrdup(fmt("%s/%s/%s/%s.html", cgit_cache_root, 
+                           cgit_query_repo, cgit_query_page, 
+                           cgit_querystring));
+                if (cgit_query_has_symref)
+                        item->ttl = cgit_cache_dynamic_ttl;
+                else if (cgit_query_has_sha1)
+                        item->ttl = cgit_cache_static_ttl;
+                else
+                        item->ttl = cgit_cache_repo_ttl;
+        }
+        if (stat(item->name, &item->st)) {
+                item->st.st_mtime = 0;
+                return 0;
+        }
+        return 1;
+}
+
+int cache_create_dirs()
+{
+        char *path;
+
+        if (!cgit_query_repo)
+                return 0;
+
+        path = fmt("%s/%s", cgit_cache_root, cgit_query_repo);
+        if (mkdir(path, S_IRWXU) && errno!=EEXIST)
+                return 0;
+
+        if (cgit_query_page) {
+                path = fmt("%s/%s/%s", cgit_cache_root, cgit_query_repo, 
+                           cgit_query_page);
+                if (mkdir(path, S_IRWXU) && errno!=EEXIST)
+                        return 0;
+        }
+        return 1;
+}
+
+int cache_lock(struct cacheitem *item)
+{
+        int ret;
+        char *lockfile = fmt("%s.lock", item->name);
+
+ top:  
+        item->fd = open(lockfile, O_WRONLY | O_CREAT | O_EXCL, S_IRUSR|S_IWUSR);
+        if (item->fd == NOLOCK && errno == ENOENT && cache_create_dirs())
+                goto top;
+        if (item->fd == NOLOCK && errno == EEXIST) {
+                struct stat st;
+                time_t t;
+                if (stat(lockfile, &st))
+                        return ret;
+                t = time(NULL);
+                if (t-st.st_mtime > cgit_cache_max_create_time && 
+                    !unlink(lockfile))
+                        goto top;
+                return 0;
+        }
+        return (item->fd > 0);
+}
+
+int cache_unlock(struct cacheitem *item)
+{
+        close(item->fd);
+        return (rename(fmt("%s.lock", item->name), item->name) == 0);
+}
+
+int cache_expired(struct cacheitem *item)
+{
+        if (item->ttl < 0)
+                return 0;
+        return item->st.st_mtime + item->ttl * 60 < time(NULL);
+}
diff --git a/cgit.c b/cgit.c
index 4c14f77..09c857c 100644
--- a/cgit.c
+++ b/cgit.c
@@ -10,29 +10,47 @@ static const char cgit_error[] =
 static const char cgit_lib_error[] =
 "<div class='error'>%s: %s</div>";
 
+int htmlfd = 0;
 
-char *cgit_root         = "/var/git";
+char *cgit_root         = "/usr/src/git";
 char *cgit_root_title   = "Git repository browser";
 char *cgit_css          = "/cgit.css";
 char *cgit_logo         = "/git-logo.png";
 char *cgit_logo_link    = "http://www.kernel.org/pub/software/scm/git/docs/";
 char *cgit_virtual_root = NULL;
 
+char *cgit_cache_root   = "/var/cache/cgit";
+
+int cgit_cache_root_ttl        =  5;
+int cgit_cache_repo_ttl        =  5;
+int cgit_cache_dynamic_ttl     =  5;
+int cgit_cache_static_ttl      = -1;
+int cgit_cache_max_create_time =  5;
+
 char *cgit_repo_name    = NULL;
 char *cgit_repo_desc    = NULL;
 char *cgit_repo_owner   = NULL;
 
+int cgit_query_has_symref = 0;
+int cgit_query_has_sha1   = 0;
+
+char *cgit_querystring  = NULL;
 char *cgit_query_repo   = NULL;
 char *cgit_query_page   = NULL;
 char *cgit_query_head   = NULL;
+char *cgit_query_sha1   = NULL;
+
+struct cacheitem cacheitem;
 
 int cgit_parse_query(char *txt, configfn fn)
 {
-        char *t = txt, *value = NULL, c;
+        char *t, *value = NULL, c;
 
         if (!txt)
                 return 0;
 
+        t = txt = xstrdup(txt);
+ 
         while((c=*t) != '\0') {
                 if (c=='=') {
                         *t = '\0';
@@ -82,8 +100,13 @@ void cgit_querystring_cb(const char *name, const char *value)
                 cgit_query_repo = xstrdup(value);
         else if (!strcmp(name, "p"))
                 cgit_query_page = xstrdup(value);
-        else if (!strcmp(name, "h"))
+        else if (!strcmp(name, "h")) {
                 cgit_query_head = xstrdup(value);
+                cgit_query_has_symref = 1;
+        } else if (!strcmp(name, "id")) {
+                cgit_query_sha1 = xstrdup(value);
+                cgit_query_has_sha1 = 1;
+        }
 }
 
 char *cgit_repourl(const char *reponame)
@@ -136,9 +159,32 @@ static int cgit_print_branch_cb(const char *refname, const unsigned char *sha1,
         return 0;
 }
 
+/* Sun, 06 Nov 1994 08:49:37 GMT */
+static char *http_date(time_t t)
+{
+        static char day[][4] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
+        static char month[][4] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
+                                  "Jul", "Aug", "Sep", "Oct", "Now", "Dec"};
+        struct tm *tm = gmtime(&t);
+        return fmt("%s, %02d %s %04d %02d:%02d:%02d GMT", day[tm->tm_wday],
+                   tm->tm_mday, month[tm->tm_mon], 1900+tm->tm_year,
+                   tm->tm_hour, tm->tm_min, tm->tm_sec);
+}
+
+static int ttl_seconds(int ttl)
+{