rofiles-fuse: Build using FUSE 3 if possible, falling back to FUSE 2

This adds build-time configuration logic to automatically detect
and switch between libfuse 2.x and 3.x.

Signed-off-by: Simon McVittie <smcv@collabora.com>
Co-authored-by: Luca BRUNO <luca.bruno@coreos.com>

src/rofiles-fuse/main.c

@@ -17,7 +17,11 @@
  * License along with this library. If not, see <https://www.gnu.org/licenses/>.
  */
 
-#define FUSE_USE_VERSION 26
+#include "config.h"
+
+#ifndef FUSE_USE_VERSION
+#error config.h needs to define FUSE_USE_VERSION
+#endif
 
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -55,7 +59,11 @@ ENSURE_RELPATH (const char *path)
 }
 
 static int
+#if FUSE_USE_VERSION >= 31
+callback_getattr (const char *path, struct stat *st_data, struct fuse_file_info *finfo)
+#else
 callback_getattr (const char *path, struct stat *st_data)
+#endif
 {
   path = ENSURE_RELPATH (path);
   if (!*path)
@@ -89,8 +97,13 @@ callback_readlink (const char *path, char *buf, size_t size)
 }
 
 static int
+#if FUSE_USE_VERSION >= 31
+callback_readdir (const char *path, void *buf, fuse_fill_dir_t filler,
+                  off_t offset, struct fuse_file_info *fi, enum fuse_readdir_flags flags)
+#else
 callback_readdir (const char *path, void *buf, fuse_fill_dir_t filler,
                   off_t offset, struct fuse_file_info *fi)
+#endif
 {
   DIR *dp;
   struct dirent *de;
@@ -123,8 +136,14 @@ callback_readdir (const char *path, void *buf, fuse_fill_dir_t filler,
       memset (&st, 0, sizeof (st));
       st.st_ino = de->d_ino;
       st.st_mode = de->d_type << 12;
+
+#if FUSE_USE_VERSION >= 31
+      if (filler (buf, de->d_name, &st, 0, 0))
+        break;
+#else
       if (filler (buf, de->d_name, &st, 0))
         break;
+#endif
     }
 
   (void) closedir (dp);
@@ -184,11 +203,21 @@ callback_symlink (const char *from, const char *to)
 }
 
 static int
+#if FUSE_USE_VERSION >= 31
+callback_rename (const char *from, const char *to, unsigned int flags)
+#else
 callback_rename (const char *from, const char *to)
+#endif
 {
+#if FUSE_USE_VERSION < 31
+  unsigned int flags = 0;
+#endif
+
   from = ENSURE_RELPATH (from);
   to = ENSURE_RELPATH (to);
-  if (renameat (basefd, from, basefd, to) == -1)
+
+  /* This assumes Linux 3.15+ */
+  if (renameat2 (basefd, from, basefd, to, flags) == -1)
     return -errno;
   return 0;
 }
@@ -299,7 +328,11 @@ verify_write_or_copyup (const char *path, const struct stat *stbuf,
   } while (0)
 
 static int
+#if FUSE_USE_VERSION >= 31
+callback_chmod (const char *path, mode_t mode, struct fuse_file_info *finfo)
+#else
 callback_chmod (const char *path, mode_t mode)
+#endif
 {
   PATH_WRITE_ENTRYPOINT (path);
 
@@ -313,7 +346,11 @@ callback_chmod (const char *path, mode_t mode)
 }
 
 static int
+#if FUSE_USE_VERSION >= 31
+callback_chown (const char *path, uid_t uid, gid_t gid, struct fuse_file_info *finfo)
+#else
 callback_chown (const char *path, uid_t uid, gid_t gid)
+#endif
 {
   PATH_WRITE_ENTRYPOINT (path);
 
@@ -323,7 +360,11 @@ callback_chown (const char *path, uid_t uid, gid_t gid)
 }
 
 static int
+#if FUSE_USE_VERSION >= 31
+callback_truncate (const char *path, off_t size, struct fuse_file_info *finfo)
+#else
 callback_truncate (const char *path, off_t size)
+#endif
 {
   PATH_WRITE_ENTRYPOINT (path);
 
@@ -338,7 +379,11 @@ callback_truncate (const char *path, off_t size)
 }
 
 static int
+#if FUSE_USE_VERSION >= 31
+callback_utimens (const char *path, const struct timespec tv[2], struct fuse_file_info *finfo)
+#else
 callback_utimens (const char *path, const struct timespec tv[2])
+#endif
 {
   /* This one isn't write-verified, we support changing times
    * even for hardlinked files.