cache.c: make all io-related functions return errno on error

We'll need proper return-values from these functions to make the cache
behave correctly (which includes giving proper error messages).

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

1 files changed, 24 insertions, 9 deletions

diff --git a/cache.c b/cache.c
index add647e..6847202 100644
--- a/cache.c
+++ b/cache.c
@@ -45,160 +45,175 @@ static int open_slot(struct cache_slot *slot)
 	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));
 	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 void close_slot(struct cache_slot *slot)
+static int close_slot(struct cache_slot *slot)
 {
+	int err = 0;
 	if (slot->cache_fd > 0) {
-		close(slot->cache_fd);
-		slot->cache_fd = -1;
+		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;
 
 	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);
 
 	if (j < 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 void close_lock(struct cache_slot *slot)
+static int close_lock(struct cache_slot *slot)
 {
+	int err = 0;
 	if (slot->lock_fd > 0) {
-		close(slot->lock_fd);
-		slot->lock_fd = -1;
+		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;
-	write(slot->lock_fd, slot->key, slot->keylen + 1);
+	if (write(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);
-	return err;
+
+	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 */
-	close(tmp);
+	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;
 }