cache.c: use xread()/xwrite() from libgit

These functions handles EINTR/EAGAIN errors during read/write operations,
which is something cache.c didn't.

While at it, fix a bug in print_slot() where errors during reading from the
cache slot might go by unnoticed.

Noticed-by: Jim Meyering <jim@meyering.net>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/cache.c b/cache.c
index 6847202..a996109 100644
--- a/cache.c
+++ b/cache.c
@@ -1,401 +1,401 @@
 /* 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 = read(slot->cache_fd, slot->buf, sizeof(slot->buf));
+	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 = 0;
+	ssize_t i;
 
 	i = lseek(slot->cache_fd, slot->keylen + 1, SEEK_SET);
 	if (i != slot->keylen + 1)
 		return errno;
 
-	while((i=read(slot->cache_fd, slot->buf, sizeof(slot->buf))) > 0)
-		j = write(STDOUT_FILENO, slot->buf, i);
+	while((i = xread(slot->cache_fd, slot->buf, sizeof(slot->buf))) > 0)
+		i = xwrite(STDOUT_FILENO, slot->buf, i);
 
-	if (j < 0)
+	if (i < 0)
 		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 (write(slot->lock_fd, slot->key, slot->keylen + 1) < 0)
+	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;
 				}
 			}
 		}
 		print_slot(slot);
 		close_slot(slot);
 		return 0;
 	}
 
 	/* 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);
 	err = print_slot(slot);
 	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) {