| -rw-r--r-- | cache.c | 4 |
1 files changed, 2 insertions, 2 deletions
@@ -1,439 +1,439 @@ /* cache.c: cache management * * Copyright (C) 2006 Lars Hjemli * * Licensed under GNU General Public License v2 * (see COPYING for full license text) * * * The cache is just a directory structure where each file is a cache slot, * and each filename is based on the hash of some key (e.g. the cgit url). * Each file contains the full key followed by the cached content for that * key. * */ #include "cgit.h" #include "cache.h" #define CACHE_BUFSIZE (1024 * 4) struct cache_slot { const char *key; int keylen; int ttl; cache_fill_fn fn; void *cbdata; int cache_fd; int lock_fd; const char *cache_name; const char *lock_name; int match; struct stat cache_st; struct stat lock_st; int bufsize; char buf[CACHE_BUFSIZE]; }; /* Open an existing cache slot and fill the cache buffer with * (part of) the content of the cache file. Return 0 on success * and errno otherwise. */ static int open_slot(struct cache_slot *slot) { char *bufz; int bufkeylen = -1; slot->cache_fd = open(slot->cache_name, O_RDONLY); if (slot->cache_fd == -1) return errno; if (fstat(slot->cache_fd, &slot->cache_st)) return errno; slot->bufsize = xread(slot->cache_fd, slot->buf, sizeof(slot->buf)); if (slot->bufsize < 0) return errno; bufz = memchr(slot->buf, 0, slot->bufsize); if (bufz) bufkeylen = bufz - slot->buf; slot->match = bufkeylen == slot->keylen && !memcmp(slot->key, slot->buf, bufkeylen + 1); return 0; } /* Close the active cache slot */ static int close_slot(struct cache_slot *slot) { int err = 0; if (slot->cache_fd > 0) { if (close(slot->cache_fd)) err = errno; else slot->cache_fd = -1; } return err; } /* Print the content of the active cache slot (but skip the key). */ static int print_slot(struct cache_slot *slot) { ssize_t i, j; i = lseek(slot->cache_fd, slot->keylen + 1, SEEK_SET); if (i != slot->keylen + 1) return errno; do { i = j = xread(slot->cache_fd, slot->buf, sizeof(slot->buf)); if (i > 0) j = xwrite(STDOUT_FILENO, slot->buf, i); } while (i > 0 && j == i); if (i < 0 || j != i) return errno; else return 0; } /* Check if the slot has expired */ static int is_expired(struct cache_slot *slot) { if (slot->ttl < 0) return 0; else return slot->cache_st.st_mtime + slot->ttl*60 < time(NULL); } /* Check if the slot has been modified since we opened it. * NB: If stat() fails, we pretend the file is modified. */ static int is_modified(struct cache_slot *slot) { struct stat st; if (stat(slot->cache_name, &st)) return 1; return (st.st_ino != slot->cache_st.st_ino || st.st_mtime != slot->cache_st.st_mtime || st.st_size != slot->cache_st.st_size); } /* Close an open lockfile */ static int close_lock(struct cache_slot *slot) { int err = 0; if (slot->lock_fd > 0) { if (close(slot->lock_fd)) err = errno; else slot->lock_fd = -1; } return err; } /* Create a lockfile used to store the generated content for a cache * slot, and write the slot key + \0 into it. * Returns 0 on success and errno otherwise. */ static int lock_slot(struct cache_slot *slot) { slot->lock_fd = open(slot->lock_name, O_RDWR|O_CREAT|O_EXCL, S_IRUSR|S_IWUSR); if (slot->lock_fd == -1) return errno; if (xwrite(slot->lock_fd, slot->key, slot->keylen + 1) < 0) return errno; return 0; } /* Release the current lockfile. If `replace_old_slot` is set the * lockfile replaces the old cache slot, otherwise the lockfile is * just deleted. */ static int unlock_slot(struct cache_slot *slot, int replace_old_slot) { int err; if (replace_old_slot) err = rename(slot->lock_name, slot->cache_name); else err = unlink(slot->lock_name); if (err) return errno; return 0; } /* Generate the content for the current cache slot by redirecting * stdout to the lock-fd and invoking the callback function */ static int fill_slot(struct cache_slot *slot) { int tmp; /* Preserve stdout */ tmp = dup(STDOUT_FILENO); if (tmp == -1) return errno; /* Redirect stdout to lockfile */ if (dup2(slot->lock_fd, STDOUT_FILENO) == -1) return errno; /* Generate cache content */ slot->fn(slot->cbdata); /* Restore stdout */ if (dup2(tmp, STDOUT_FILENO) == -1) return errno; /* Close the temporary filedescriptor */ if (close(tmp)) return errno; return 0; } /* Crude implementation of 32-bit FNV-1 hash algorithm, * see http://www.isthe.com/chongo/tech/comp/fnv/ for details * about the magic numbers. */ #define FNV_OFFSET 0x811c9dc5 #define FNV_PRIME 0x01000193 unsigned long hash_str(const char *str) { unsigned long h = FNV_OFFSET; unsigned char *s = (unsigned char *)str; if (!s) return h; while(*s) { h *= FNV_PRIME; h ^= *s++; } return h; } static int process_slot(struct cache_slot *slot) { int err; err = open_slot(slot); if (!err && slot->match) { if (is_expired(slot)) { if (!lock_slot(slot)) { /* If the cachefile has been replaced between * `open_slot` and `lock_slot`, we'll just * serve the stale content from the original * cachefile. This way we avoid pruning the * newly generated slot. The same code-path * is chosen if fill_slot() fails for some * reason. * * TODO? check if the new slot contains the * same key as the old one, since we would * prefer to serve the newest content. * This will require us to open yet another * file-descriptor and read and compare the * key from the new file, so for now we're * lazy and just ignore the new file. */ if (is_modified(slot) || fill_slot(slot)) { unlock_slot(slot, 0); close_lock(slot); } else { close_slot(slot); unlock_slot(slot, 1); slot->cache_fd = slot->lock_fd; } } } if ((err = print_slot(slot)) != 0) { cache_log("[cgit] error printing cache %s: %s (%d)\n", slot->cache_name, strerror(err), err); } close_slot(slot); return err; } /* If the cache slot does not exist (or its key doesn't match the * current key), lets try to create a new cache slot for this * request. If this fails (for whatever reason), lets just generate * the content without caching it and fool the caller to belive * everything worked out (but print a warning on stdout). */ close_slot(slot); if ((err = lock_slot(slot)) != 0) { cache_log("[cgit] Unable to lock slot %s: %s (%d)\n", slot->lock_name, strerror(err), err); slot->fn(slot->cbdata); return 0; } if ((err = fill_slot(slot)) != 0) { cache_log("[cgit] Unable to fill slot %s: %s (%d)\n", slot->lock_name, strerror(err), err); unlock_slot(slot, 0); close_lock(slot); slot->fn(slot->cbdata); return 0; } // We've got a valid cache slot in the lock file, which // is about to replace the old cache slot. But if we // release the lockfile and then try to open the new cache // slot, we might get a race condition with a concurrent // writer for the same cache slot (with a different key). // Lets avoid such a race by just printing the content of // the lock file. slot->cache_fd = slot->lock_fd; unlock_slot(slot, 1); if ((err = print_slot(slot)) != 0) { cache_log("[cgit] error printing cache %s: %s (%d)\n", slot->cache_name, strerror(err), err); } close_slot(slot); return err; } /* Print cached content to stdout, generate the content if necessary. */ int cache_process(int size, const char *path, const char *key, int ttl, cache_fill_fn fn, void *cbdata) { unsigned long hash; int len, i; char filename[1024]; char lockname[1024 + 5]; /* 5 = ".lock" */ struct cache_slot slot; /* If the cache is disabled, just generate the content */ if (size <= 0) { fn(cbdata); return 0; } /* Verify input, calculate filenames */ if (!path) { cache_log("[cgit] Cache path not specified, caching is disabled\n"); fn(cbdata); return 0; } len = strlen(path); if (len > sizeof(filename) - 10) { /* 10 = "/01234567\0" */ cache_log("[cgit] Cache path too long, caching is disabled: %s\n", path); fn(cbdata); return 0; } if (!key) key = ""; hash = hash_str(key) % size; strcpy(filename, path); if (filename[len - 1] != '/') filename[len++] = '/'; for(i = 0; i < 8; i++) { sprintf(filename + len++, "%x", (unsigned char)(hash & 0xf)); hash >>= 4; } filename[len] = '\0'; strcpy(lockname, filename); strcpy(lockname + len, ".lock"); slot.fn = fn; slot.cbdata = cbdata; slot.ttl = ttl; slot.cache_name = filename; slot.lock_name = lockname; slot.key = key; slot.keylen = strlen(key); return process_slot(&slot); } /* Return a strftime formatted date/time * NB: the result from this function is to shared memory */ char *sprintftime(const char *format, time_t time) { static char buf[64]; struct tm *tm; if (!time) return NULL; tm = gmtime(&time); strftime(buf, sizeof(buf)-1, format, tm); return buf; } int cache_ls(const char *path) { DIR *dir; struct dirent *ent; int err = 0; struct cache_slot slot; char fullname[1024]; char *name; if (!path) { cache_log("[cgit] cache path not specified\n"); return -1; } if (strlen(path) > 1024 - 10) { cache_log("[cgit] cache path too long: %s\n", path); return -1; } dir = opendir(path); if (!dir) { err = errno; cache_log("[cgit] unable to open path %s: %s (%d)\n", path, strerror(err), err); return err; } strcpy(fullname, path); name = fullname + strlen(path); if (*(name - 1) != '/') { *name++ = '/'; *name = '\0'; } slot.cache_name = fullname; while((ent = readdir(dir)) != NULL) { if (strlen(ent->d_name) != 8) continue; strcpy(name, ent->d_name); if ((err = open_slot(&slot)) != 0) { cache_log("[cgit] unable to open path %s: %s (%d)\n", fullname, strerror(err), err); continue; } - printf("%s %s %10zd %s\n", + printf("%s %s %10"PRIuMAX" %s\n", name, sprintftime("%Y-%m-%d %H:%M:%S", slot.cache_st.st_mtime), - slot.cache_st.st_size, + (uintmax_t)slot.cache_st.st_size, slot.buf); close_slot(&slot); } closedir(dir); return 0; } /* Print a message to stdout */ void cache_log(const char *format, ...) { va_list args; va_start(args, format); vfprintf(stderr, format, args); va_end(args); } |