Added support for custom attributes leveraging the new metadata logging

Now that littlefs has been rebuilt almost from the ground up with the
intention to support custom attributes, adding in custom attribute
support is relatively easy.

The highest bit in the 9-bit type structure indicates that an attribute
is a user-specified custom attribute. The user then has a full 8-bits to
specify the attribute type. Other than that, custom attributes are
treated the same as system-level attributes.

Also made some tweaks to custom attributes:
- Adopted the opencfg for file-level attributes provided by dpgeorge
- Changed setattrs/getattrs to the simpler setattr/getattr functions
  users will probably be more familiar with. Note that multiple
  attributes can still be committed atomically with files, though not
  with directories.
- Changed LFS_ATTRS_MAX -> LFS_ATTR_MAX since there's no longer a global
  limit on the sum of attribute sizes, which was rather confusing.
  Though they are still limited by what can fit in a metadata-pair.

lfs.c

@@ -364,7 +364,7 @@ static void lfs_alloc_ack(lfs_t *lfs) {
 //    d->block_count = lfs_fromle32(d->block_count);
 //    d->version     = lfs_fromle32(d->version);
 //    d->inline_size = lfs_fromle32(d->inline_size);
-//    d->attrs_size  = lfs_fromle32(d->attrs_size);
+//    d->attr_size  = lfs_fromle32(d->attr_size);
 //    d->name_size   = lfs_fromle32(d->name_size);
 //}
 //
@@ -375,7 +375,7 @@ static void lfs_alloc_ack(lfs_t *lfs) {
 //    d->block_count = lfs_tole32(d->block_count);
 //    d->version     = lfs_tole32(d->version);
 //    d->inline_size = lfs_tole32(d->inline_size);
-//    d->attrs_size  = lfs_tole32(d->attrs_size);
+//    d->attr_size  = lfs_tole32(d->attr_size);
 //    d->name_size   = lfs_tole32(d->name_size);
 //}
 
@@ -430,7 +430,7 @@ static inline bool lfs_pairsync(
     (((uint32_t)(type) << 22) | ((uint32_t)(id) << 12) | (uint32_t)(size))
 
 #define LFS_MKATTR(type, id, buffer, size, next) \
-    &(const lfs_mattr_t){(next), LFS_MKTAG(type, id, size), (buffer)}
+    &(const lfs_mattr_t){LFS_MKTAG(type, id, size), (buffer), (next)}
 
 static inline bool lfs_tagisvalid(uint32_t tag) {
     return !(tag & 0x80000000);
@@ -526,13 +526,20 @@ static int32_t lfs_commitget(lfs_t *lfs, lfs_block_t block, lfs_off_t off,
     return LFS_ERR_NOENT;
 }
 
+static int lfs_commitattrs(lfs_t *lfs, struct lfs_commit *commit,
+        uint16_t id, const struct lfs_attr *attrs);
+
 static int lfs_commitmove(lfs_t *lfs, struct lfs_commit *commit,
         uint16_t fromid, uint16_t toid,
         const lfs_mdir_t *dir, const lfs_mattr_t *attrs);
 
 static int lfs_commitattr(lfs_t *lfs, struct lfs_commit *commit,
         uint32_t tag, const void *buffer) {
-    if (lfs_tagtype(tag) == LFS_FROM_MOVE) {
+    if (lfs_tagtype(tag) == LFS_FROM_ATTRS) {
+        // special case for custom attributes
+        return lfs_commitattrs(lfs, commit,
+                lfs_tagid(tag), buffer);
+    } else if (lfs_tagtype(tag) == LFS_FROM_MOVE) {
         // special case for moves
         return lfs_commitmove(lfs, commit,
                 lfs_tagsize(tag), lfs_tagid(tag),
@@ -586,6 +593,19 @@ static int lfs_commitattr(lfs_t *lfs, struct lfs_commit *commit,
     return 0;
 }
 
+static int lfs_commitattrs(lfs_t *lfs, struct lfs_commit *commit,
+        uint16_t id, const struct lfs_attr *attrs) {
+    for (const struct lfs_attr *a = attrs; a; a = a->next) {
+        int err = lfs_commitattr(lfs, commit,
+                LFS_MKTAG(0x100 | a->type, id, a->size), a->buffer);
+        if (err) {
+            return err;
+        }
+    }
+
+    return 0;
+}
+
 static int lfs_commitmove(lfs_t *lfs, struct lfs_commit *commit,
         uint16_t fromid, uint16_t toid,
         const lfs_mdir_t *dir, const lfs_mattr_t *attrs) {
@@ -1378,9 +1398,6 @@ static int lfs_dir_getinfo(lfs_t *lfs, lfs_mdir_t *dir,
     }
 
     info->type = lfs_tagtype(tag);
-    if (lfs_tagsize(tag) > lfs->name_size) {
-        return LFS_ERR_RANGE;
-    }
 
     struct lfs_ctz ctz;
     tag = lfs_dir_get(lfs, dir, 0x7c3ff000,
@@ -1410,7 +1427,7 @@ int lfs_mkdir(lfs_t *lfs, const char *path) {
 
     lfs_mdir_t cwd;
     int32_t res = lfs_dir_lookup(lfs, &cwd, &path);
-    if (res != LFS_ERR_NOENT || !path) {
+    if (!(res == LFS_ERR_NOENT && path)) {
         return (res < 0) ? res : LFS_ERR_EXIST;
     }
 
@@ -1792,8 +1809,9 @@ static int lfs_ctztraverse(lfs_t *lfs,
 
 
 /// Top level file operations ///
-int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
-        const char *path, int flags) {
+int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
+        const char *path, int flags,
+        const struct lfs_file_config *cfg) {
     // deorphan if we haven't yet, needed at most once after poweron
     if ((flags & 3) != LFS_O_RDONLY && !lfs->deorphaned) {
         int err = lfs_deorphan(lfs);
@@ -1805,7 +1823,7 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
     // allocate entry for file if it doesn't exist
     lfs_mdir_t cwd;
     int32_t tag = lfs_dir_lookup(lfs, &cwd, &path);
-    if (tag < 0 && (tag != LFS_ERR_NOENT || !path)) {
+    if (tag < 0 && !(tag == LFS_ERR_NOENT && path)) {
         return tag;
     }
 
@@ -1859,6 +1877,7 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
     }
 
     // setup file struct
+    file->cfg = cfg;
     file->pair[0] = cwd.pair[0];
     file->pair[1] = cwd.pair[1];
     file->id = lfs_tagid(tag);
@@ -1866,9 +1885,34 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
     file->pos = 0;
     file->attrs = NULL;
 
+    if (cfg && cfg->attrs) {
+        // fetch attrs
+        for (const struct lfs_attr *a = cfg->attrs; a; a = a->next) {
+            if ((file->flags & 3) != LFS_O_WRONLY) {
+                int32_t res = lfs_dir_get(lfs, &cwd, 0x7ffff000,
+                        LFS_MKTAG(0x100 | a->type, file->id, a->size), a->buffer);
+                if (res < 0 && res != LFS_ERR_NOENT) {
+                    return res;
+                }
+            }
+
+            if ((file->flags & 3) != LFS_O_RDONLY) {
+                if (a->size > lfs->attr_size) {
+                    return LFS_ERR_NOSPC;
+                }
+
+                file->flags |= LFS_F_DIRTY;
+            }
+        }
+
+        file->attrs = cfg->attrs;
+    }
+
     // allocate buffer if needed
     file->cache.block = 0xffffffff;
-    if (lfs->cfg->file_buffer) {
+    if (file->cfg && file->cfg->buffer) {
+        file->cache.buffer = file->cfg->buffer;
+    } else if (lfs->cfg->file_buffer) {
         file->cache.buffer = lfs->cfg->file_buffer;
     } else if ((file->flags & 3) == LFS_O_RDONLY) {
         file->cache.buffer = lfs_malloc(lfs->cfg->read_size);
@@ -1909,6 +1953,11 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
     return 0;
 }
 
+int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
+        const char *path, int flags) {
+    return lfs_file_opencfg(lfs, file, path, flags, NULL);
+}
+
 int lfs_file_close(lfs_t *lfs, lfs_file_t *file) {
     int err = lfs_file_sync(lfs, file);
 
@@ -1921,7 +1970,7 @@ int lfs_file_close(lfs_t *lfs, lfs_file_t *file) {
     }
 
     // clean up memory
-    if (!lfs->cfg->file_buffer) {
+    if (!(file->cfg && file->cfg->buffer) && !lfs->cfg->file_buffer) {
         lfs_free(file->cache.buffer);
     }
 
@@ -2071,7 +2120,8 @@ int lfs_file_sync(lfs_t *lfs, lfs_file_t *file) {
             int err = lfs_dir_commit(lfs, &cwd,
                     LFS_MKATTR(LFS_TYPE_CTZSTRUCT, file->id,
                         &file->ctz.head, sizeof(file->ctz),
-                    file->attrs));
+                    LFS_MKATTR(LFS_FROM_ATTRS, file->id, file->attrs, 0,
+                    NULL)));
             if (err) {
                 return err;
             }
@@ -2079,7 +2129,8 @@ int lfs_file_sync(lfs_t *lfs, lfs_file_t *file) {
             int err = lfs_dir_commit(lfs, &cwd,
                     LFS_MKATTR(LFS_TYPE_INLINESTRUCT, file->id,
                             file->cache.buffer, file->ctz.size,
-                    file->attrs));
+                    LFS_MKATTR(LFS_FROM_ATTRS, file->id, file->attrs, 0,
+                    NULL)));
             if (err) {
                 return err;
             }
@@ -2688,7 +2739,85 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
     return 0;
 }
 
-//int lfs_getattrs(lfs_t *lfs, const char *path,
+lfs_ssize_t lfs_getattr(lfs_t *lfs, const char *path,
+        uint8_t type, void *buffer, lfs_size_t size) {
+    lfs_mdir_t cwd;
+    int32_t res = lfs_dir_lookup(lfs, &cwd, &path);
+    if (res < 0) {
+        return res;
+    }
+
+    res = lfs_dir_get(lfs, &cwd, 0x7ffff000,
+            LFS_MKTAG(0x100 | type, lfs_tagid(res),
+                lfs_min(size, lfs->attr_size)), buffer);
+    if (res < 0) {
+        if (res == LFS_ERR_NOENT) {
+            return LFS_ERR_NOATTR;
+        }
+        return res;
+    }
+
+    return lfs_tagsize(res);
+}
+
+int lfs_setattr(lfs_t *lfs, const char *path,
+        uint8_t type, const void *buffer, lfs_size_t size) {
+    if (size > lfs->attr_size) {
+        return LFS_ERR_NOSPC;
+    }
+
+    lfs_mdir_t cwd;
+    int32_t res = lfs_dir_lookup(lfs, &cwd, &path);
+    if (res < 0) {
+        return res;
+    }
+
+    return lfs_dir_commit(lfs, &cwd,
+        LFS_MKATTR(0x100 | type, lfs_tagid(res), buffer, size,
+        NULL));
+}
+
+lfs_ssize_t lfs_fs_getattr(lfs_t *lfs,
+        uint8_t type, void *buffer, lfs_size_t size) {
+    lfs_mdir_t superdir;
+    int err = lfs_dir_fetch(lfs, &superdir, (const lfs_block_t[2]){0, 1});
+    if (err) {
+        return err;
+    }
+
+    int32_t res = lfs_dir_get(lfs, &superdir, 0x7ffff000,
+            LFS_MKTAG(0x100 | type, 0,
+                lfs_min(size, lfs->attr_size)), buffer);
+    if (res < 0) {
+        if (res == LFS_ERR_NOENT) {
+            return LFS_ERR_NOATTR;
+        }
+        return res;
+    }
+
+    return lfs_tagsize(res);
+}
+
+int lfs_fs_setattr(lfs_t *lfs,
+        uint8_t type, const void *buffer, lfs_size_t size) {
+    if (size > lfs->attr_size) {
+        return LFS_ERR_NOSPC;
+    }
+
+    lfs_mdir_t superdir;
+    int err = lfs_dir_fetch(lfs, &superdir, (const lfs_block_t[2]){0, 1});
+    if (err) {
+        return err;
+    }
+
+    return lfs_dir_commit(lfs, &superdir,
+        LFS_MKATTR(0x100 | type, 0, buffer, size,
+        NULL));
+}
+
+//
+//
+//
 //        const struct lfs_attr *attrs, int count) {
 //    lfs_mdir_t cwd;
 //    int err = lfs_dir_fetch(lfs, &cwd, lfs->root);
@@ -2777,10 +2906,10 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
         lfs->inline_size = lfs_min(LFS_INLINE_MAX, lfs->cfg->read_size);
     }
 
-    LFS_ASSERT(lfs->cfg->attrs_size <= LFS_ATTRS_MAX);
-    lfs->attrs_size = lfs->cfg->attrs_size;
-    if (!lfs->attrs_size) {
-        lfs->attrs_size = LFS_ATTRS_MAX;
+    LFS_ASSERT(lfs->cfg->attr_size <= LFS_ATTR_MAX);
+    lfs->attr_size = lfs->cfg->attr_size;
+    if (!lfs->attr_size) {
+        lfs->attr_size = LFS_ATTR_MAX;
     }
 
     LFS_ASSERT(lfs->cfg->name_size <= LFS_NAME_MAX);
@@ -2873,7 +3002,7 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
         .block_size  = lfs->cfg->block_size,
         .block_count = lfs->cfg->block_count,
         .inline_size = lfs->inline_size,
-        .attrs_size  = lfs->attrs_size,
+        .attr_size   = lfs->attr_size,
         .name_size   = lfs->name_size,
     };
 
@@ -2954,14 +3083,14 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
         lfs->inline_size = superblock.inline_size;
     }
 
-    if (superblock.attrs_size) {
-        if (superblock.attrs_size > lfs->attrs_size) {
-            LFS_ERROR("Unsupported attrs size (%d > %d)",
-                    superblock.attrs_size, lfs->attrs_size);
+    if (superblock.attr_size) {
+        if (superblock.attr_size > lfs->attr_size) {
+            LFS_ERROR("Unsupported attr size (%d > %d)",
+                    superblock.attr_size, lfs->attr_size);
             return LFS_ERR_INVAL;
         }
 
-        lfs->attrs_size = superblock.attrs_size;
+        lfs->attr_size = superblock.attr_size;
     }
 
     if (superblock.name_size) {