Added file-level and fs-level custom attribute APIs

In the form of lfs_file_setattr, lfs_file_getattr, lfs_fs_setattr,
lfs_fs_getattr.

This enables atomic updates of custom attributes as described in
6c754c8, and provides a custom attribute API that allows custom attributes
to be stored on the filesystem itself.

lfs.c

@@ -932,11 +932,11 @@ shift:
     // shift over any files/directories that are affected
     for (lfs_file_t *f = lfs->files; f; f = f->next) {
         if (lfs_paircmp(f->pair, dir->pair) == 0) {
-            if (f->poff == entry->off && entry->size == 0) {
+            if (f->pairoff == entry->off && entry->size == 0) {
                 f->pair[0] = 0xffffffff;
                 f->pair[1] = 0xffffffff;
-            } else if (f->poff > entry->off) {
+            } else if (f->pairoff > entry->off) {
-                f->poff += diff;
+                f->pairoff += diff;
             }
         }
     }
@@ -1135,8 +1135,8 @@ static int lfs_dir_getattrs(lfs_t *lfs,
         }
 
         for (int j = 0; j < count; j++) {
-            if (attr.d.type == attrs[j].type) {
+            if (attrs[j].type == attr.d.type) {
-                if (attr.d.len > attrs[j].size) {
+                if (attrs[j].size < attr.d.len) {
                     return LFS_ERR_RANGE;
                 }
 
@@ -1190,8 +1190,8 @@ static lfs_ssize_t lfs_dir_checkattrs(lfs_t *lfs,
     }
 
     if (nsize > lfs->attrs_size || (
-            (0x7fffffff & dir->d.size) + lfs_entry_size(entry) -
+            lfs_entry_size(entry) - lfs_entry_alen(entry) + nsize
-            lfs_entry_alen(entry) + nsize > lfs->cfg->block_size)) {
+                > lfs->cfg->block_size)) {
         return LFS_ERR_NOSPC;
     }
 
@@ -1688,7 +1688,7 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
     // setup file struct
     file->pair[0] = cwd.pair[0];
     file->pair[1] = cwd.pair[1];
-    file->poff = entry.off;
+    file->pairoff = entry.off;
     file->flags = flags;
     file->pos = 0;
 
@@ -1754,10 +1754,10 @@ int lfs_file_close(lfs_t *lfs, lfs_file_t *file) {
         }
 
         return err;
-}
+    }
 
-static int lfs_file_relocate(lfs_t *lfs, lfs_file_t *file) {
+    static int lfs_file_relocate(lfs_t *lfs, lfs_file_t *file) {
-relocate:;
+    relocate:;
         // just relocate what exists into new block
         lfs_block_t nblock;
         int err = lfs_alloc(lfs, &nblock);
@@ -1800,9 +1800,9 @@ relocate:;
 
         file->block = nblock;
         return 0;
-}
+    }
 
-static int lfs_file_flush(lfs_t *lfs, lfs_file_t *file) {
+    static int lfs_file_flush(lfs_t *lfs, lfs_file_t *file) {
         if (file->flags & LFS_F_READING) {
             file->flags &= ~LFS_F_READING;
         }
@@ -1892,43 +1892,55 @@ int lfs_file_sync(lfs_t *lfs, lfs_file_t *file) {
             return err;
         }
 
-        lfs_entry_t entry = {.off = file->poff};
+        lfs_entry_t entry = {.off = file->pairoff};
         err = lfs_dir_get(lfs, &cwd, entry.off, &entry.d, sizeof(entry.d));
         lfs_entry_fromle32(&entry.d);
         if (err) {
             return err;
         }
+        entry.size = lfs_entry_size(&entry);
 
         LFS_ASSERT((0xf & entry.d.type) == LFS_TYPE_REG);
-        lfs_size_t oldlen = lfs_entry_elen(&entry);
+        lfs_size_t oldelen = lfs_entry_elen(&entry);
-        entry.size = lfs_entry_size(&entry);
+        lfs_size_t oldalen = lfs_entry_alen(&entry);
+        const void *buffer;
+        lfs_size_t size;
 
         // either update the references or inline the whole file
         if (!(file->flags & LFS_F_INLINE)) {
             entry.d.type = LFS_STRUCT_CTZ | LFS_TYPE_REG;
-            entry.d.elen = sizeof(entry.d)-4;
             entry.d.u.file.head = file->head;
             entry.d.u.file.size = file->size;
 
-            err = lfs_dir_set(lfs, &cwd, &entry, (struct lfs_region[]){
+            buffer = (const uint8_t *)&entry.d + 4;
-                    {LFS_FROM_MEM, 0, 4+oldlen,
+            size = sizeof(entry.d) - 4;
-                        &entry.d, sizeof(entry.d)}}, 1);
-            if (err) {
-                return err;
-            }
         } else {
             entry.d.type = LFS_STRUCT_INLINE | LFS_TYPE_REG;
-            entry.d.elen = file->size & 0xff;
-            entry.d.alen = (entry.d.alen & 0x3f) | ((file->size >> 2) & 0xc0);
 
+            buffer = file->cache.buffer;
+            size = file->size;
+        }
+
+        // get new alen from disk
+        lfs_ssize_t newalen = lfs_dir_checkattrs(lfs, &cwd, &entry,
+                file->attrs, file->attrcount);
+        if (newalen < 0) {
+            return newalen;
+        }
+
+        entry.d.elen = size & 0xff;
+        entry.d.alen = (newalen & 0x3f) | ((size >> 2) & 0xc0);
+
+        // write out update
         err = lfs_dir_set(lfs, &cwd, &entry, (struct lfs_region[]){
-                    {LFS_FROM_MEM, 0, 0, &entry.d, 4},
+                {LFS_FROM_MEM, 0, 4, &entry.d, 4},
-                    {LFS_FROM_MEM, 0, 4+oldlen,
+                {LFS_FROM_MEM, 4, oldelen, buffer, size},
-                        file->cache.buffer, file->size}}, 2);
+                {LFS_FROM_ATTRS, 4+oldelen, oldalen,
+                    &(struct lfs_region_attrs){file->attrs, file->attrcount},
+                    newalen}}, 3);
         if (err) {
             return err;
         }
-        }
 
         file->flags &= ~LFS_F_DIRTY;
     }
@@ -2221,6 +2233,81 @@ lfs_soff_t lfs_file_size(lfs_t *lfs, lfs_file_t *file) {
     }
 }
 
+int lfs_file_getattrs(lfs_t *lfs, lfs_file_t *file,
+        const struct lfs_attr *attrs, int count) {
+    // set to null in case we can't find the attrs (missing file?)
+    for (int j = 0; j < count; j++) {
+        memset(attrs[j].buffer, 0, attrs[j].size);
+    }
+
+    // load from disk if we haven't already been deleted
+    if (!lfs_pairisnull(file->pair)) {
+        lfs_dir_t cwd;
+        int err = lfs_dir_fetch(lfs, &cwd, file->pair);
+        if (err) {
+            return err;
+        }
+
+        lfs_entry_t entry = {.off = file->pairoff};
+        err = lfs_dir_get(lfs, &cwd, entry.off, &entry.d, sizeof(entry.d));
+        if (err) {
+            return err;
+        }
+        entry.size = lfs_entry_size(&entry);
+
+        err = lfs_dir_getattrs(lfs, &cwd, &entry, attrs, count);
+        if (err) {
+            return err;
+        }
+    }
+
+    // override an attrs we have stored locally
+    for (int i = 0; i < file->attrcount; i++) {
+        for (int j = 0; j < count; j++) {
+            if (attrs[j].type == file->attrs[i].type) {
+                if (attrs[j].size < file->attrs[i].size) {
+                    return LFS_ERR_RANGE;
+                }
+
+                memcpy(attrs[j].buffer,
+                        file->attrs[i].buffer, file->attrs[i].size);
+            }
+        }
+    }
+
+    return 0;
+}
+
+int lfs_file_setattrs(lfs_t *lfs, lfs_file_t *file,
+        const struct lfs_attr *attrs, int count) {
+    // just tack to the file, will be written at sync time
+    file->attrs = attrs;
+    file->attrcount = count;
+
+    // at least make sure attributes fit
+    if (!lfs_pairisnull(file->pair)) {
+        lfs_dir_t cwd;
+        int err = lfs_dir_fetch(lfs, &cwd, file->pair);
+        if (err) {
+            return err;
+        }
+
+        lfs_entry_t entry = {.off = file->pairoff};
+        err = lfs_dir_get(lfs, &cwd, entry.off, &entry.d, sizeof(entry.d));
+        if (err) {
+            return err;
+        }
+        entry.size = lfs_entry_size(&entry);
+
+        lfs_ssize_t res = lfs_dir_checkattrs(lfs, &cwd, &entry, attrs, count);
+        if (res < 0) {
+            return res;
+        }
+    }
+
+    return 0;
+}
+
 
 /// General fs operations ///
 int lfs_stat(lfs_t *lfs, const char *path, struct lfs_info *info) {
@@ -2427,8 +2514,6 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
     return 0;
 }
 
-
-/// Attribute operations ///
 int lfs_getattrs(lfs_t *lfs, const char *path,
         const struct lfs_attr *attrs, int count) {
     lfs_dir_t cwd;
@@ -2646,10 +2731,6 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
 
     // load superblock
     lfs_dir_t dir;
-    lfs_entry_t entry;
-    lfs_superblock_t superblock;
-    char magic[8];
-
     err = lfs_dir_fetch(lfs, &dir, (const lfs_block_t[2]){0, 1});
     if (err) {
         if (err == LFS_ERR_CORRUPT) {
@@ -2658,11 +2739,13 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
         return err;
     }
 
-    err = lfs_dir_get(lfs, &dir, sizeof(dir.d), &entry.d, sizeof(entry.d));
+    lfs_entry_t entry = {.off = sizeof(dir.d)};
+    err = lfs_dir_get(lfs, &dir, entry.off, &entry.d, sizeof(entry.d));
     if (err) {
         return err;
     }
 
+    lfs_superblock_t superblock;
     memset(&superblock.d, 0, sizeof(superblock.d));
     err = lfs_dir_get(lfs, &dir,
             sizeof(dir.d)+4, &superblock.d,
@@ -2672,6 +2755,7 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
         return err;
     }
 
+    char magic[8];
     err = lfs_dir_get(lfs, &dir,
             sizeof(dir.d)+lfs_entry_size(&entry)-entry.d.nlen, magic,
             lfs_min(sizeof(magic), entry.d.nlen));
@@ -2733,7 +2817,7 @@ int lfs_unmount(lfs_t *lfs) {
 }
 
 
-/// Littlefs specific operations ///
+/// Internal filesystem filesystem operations ///
 int lfs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data) {
     if (lfs_pairisnull(lfs->root)) {
         return 0;
@@ -3064,3 +3148,38 @@ int lfs_deorphan(lfs_t *lfs) {
     return 0;
 }
 
+
+/// External filesystem filesystem operations ///
+int lfs_fs_getattrs(lfs_t *lfs, const struct lfs_attr *attrs, int count) {
+    lfs_dir_t dir;
+    int err = lfs_dir_fetch(lfs, &dir, (const lfs_block_t[2]){0, 1});
+    if (err) {
+        return err;
+    }
+
+    lfs_entry_t entry = {.off = sizeof(dir.d)};
+    err = lfs_dir_get(lfs, &dir, entry.off, &entry.d, sizeof(entry.d));
+    if (err) {
+        return err;
+    }
+    entry.size = lfs_entry_size(&entry);
+
+    return lfs_dir_getattrs(lfs, &dir, &entry, attrs, count);
+}
+
+int lfs_fs_setattrs(lfs_t *lfs, const struct lfs_attr *attrs, int count) {
+    lfs_dir_t dir;
+    int err = lfs_dir_fetch(lfs, &dir, (const lfs_block_t[2]){0, 1});
+    if (err) {
+        return err;
+    }
+
+    lfs_entry_t entry = {.off = sizeof(dir.d)};
+    err = lfs_dir_get(lfs, &dir, entry.off, &entry.d, sizeof(entry.d));
+    if (err) {
+        return err;
+    }
+    entry.size = lfs_entry_size(&entry);
+
+    return lfs_dir_setattrs(lfs, &dir, &entry, attrs, count);
+}

lfs.h

@@ -283,7 +283,7 @@ typedef struct lfs_cache {
 typedef struct lfs_file {
     struct lfs_file *next;
     lfs_block_t pair[2];
-    lfs_off_t poff;
+    lfs_off_t pairoff;
 
     lfs_block_t head;
     lfs_size_t size;
@@ -294,6 +294,9 @@ typedef struct lfs_file {
     lfs_block_t block;
     lfs_off_t off;
     lfs_cache_t cache;
+
+    const struct lfs_attr *attrs;
+    int attrcount;
 } lfs_file_t;
 
 typedef struct lfs_dir {