lib: save one strdup by using GNU basename() implementation

POSIX states that basename(3) may modify its input string. For this
reason, strdup(3) is used in__nvme_transport_handle_open_direct() so
that it is safe to call basename(3) on a const char*.

This patch introduces an nvme_basename() function that is guaranteed to
never modify its input and is thus safe to be used on string literals.
It is a copy of basename(3) implementation from glibc.

This change allows us to avoid one needless dynamic allocation.

Signed-off-by: Michal Rábek <[email protected]>

Author: MichaelRabek

libnvme/src/nvme/lib.c

@@ -125,15 +125,11 @@ static int __nvme_transport_handle_open_direct(
 {
 	struct nvme_passthru_cmd dummy = { 0 };
 	_cleanup_free_ char *path = NULL;
-	_cleanup_free_ char *_devname = NULL;
 	char *name;
 	int ret, id, ns;
 	bool c = true;
 
-	_devname = strdup(devname);
-	if (!_devname)
-		return -ENOMEM;
-	name = basename(_devname);
+	name = nvme_basename(devname);
 
 	hdl->type = NVME_TRANSPORT_HANDLE_TYPE_DIRECT;
 

libnvme/src/nvme/util.c

@@ -981,3 +981,12 @@ const struct ifaddrs *nvme_getifaddrs(struct nvme_global_ctx *ctx)
 
 	return ctx->ifaddrs_cache;
 }
+
+/* This used instead of basename() due to behavioral differences between
+ * the POSIX and the GNU version. This is the glibc implementation.
+ * Original source: https://github.com/bminor/glibc/blob/master/string/basename.c */
+char *nvme_basename(const char *path)
+{
+	char *p = (char *) strrchr(path, '/');
+	return p ? p + 1 : (char *) path;
+}

libnvme/src/nvme/util.h

@@ -218,3 +218,10 @@ int nvme_uuid_random(unsigned char uuid[NVME_UUID_LEN]);
  */
 int nvme_uuid_find(struct nvme_id_uuid_list *uuid_list, const unsigned char uuid[NVME_UUID_LEN]);
 
+/**
+ * nvme_basename - Return the final path component (the one after the last '/')
+ * @path: A string containing a filesystem path
+ *
+ * Return: A pointer into the original null-terminated path string.
+ */
+char *nvme_basename(const char *path);