Added error when opening multiple files with a statically allocated buffer

Opening multiple files simultaneously is not supported without dynamic memory,
but the previous behaviour would just let the files overwrite each other, which
could lead to bad errors down the line

found by husigeza

lfs.c

@@ -783,26 +783,19 @@ static int lfs_dir_find(lfs_t *lfs, lfs_dir_t *dir,
         lfs_entry_t *entry, const char **path) {
     const char *pathname = *path;
     size_t pathlen;
+    entry->d.type = LFS_TYPE_DIR;
+    entry->d.elen = sizeof(entry->d) - 4;
+    entry->d.alen = 0;
+    entry->d.nlen = 0;
+    entry->d.u.dir[0] = lfs->root[0];
+    entry->d.u.dir[1] = lfs->root[1];
 
     while (true) {
-    nextname:
+nextname:
         // skip slashes
         pathname += strspn(pathname, "/");
         pathlen = strcspn(pathname, "/");
 
-        // special case for root dir
-        if (pathname[0] == '\0') {
-            *entry = (lfs_entry_t){
-                .d.type = LFS_TYPE_DIR,
-                .d.elen = sizeof(entry->d) - 4,
-                .d.alen = 0,
-                .d.nlen = 0,
-                .d.u.dir[0] = lfs->root[0],
-                .d.u.dir[1] = lfs->root[1],
-            };
-            return 0;
-        }
-
         // skip '.' and root '..'
         if ((pathlen == 1 && memcmp(pathname, ".", 1) == 0) ||
             (pathlen == 2 && memcmp(pathname, "..", 2) == 0)) {
@@ -834,10 +827,25 @@ static int lfs_dir_find(lfs_t *lfs, lfs_dir_t *dir,
             suffix += sufflen;
         }
 
+        // found path
+        if (pathname[0] == '\0') {
+            return 0;
+        }
+
         // update what we've found
         *path = pathname;
 
-        // find path
+        // continue on if we hit a directory
+        if (entry->d.type != LFS_TYPE_DIR) {
+            return LFS_ERR_NOTDIR;
+        }
+
+        int err = lfs_dir_fetch(lfs, dir, entry->d.u.dir);
+        if (err) {
+            return err;
+        }
+
+        // find entry matching name
         while (true) {
             int err = lfs_dir_next(lfs, dir, entry);
             if (err) {
@@ -873,21 +881,8 @@ static int lfs_dir_find(lfs_t *lfs, lfs_dir_t *dir,
             entry->d.type &= ~0x80;
         }
 
+        // to next name
         pathname += pathlen;
-        pathname += strspn(pathname, "/");
-        if (pathname[0] == '\0') {
-            return 0;
-        }
-
-        // continue on if we hit a directory
-        if (entry->d.type != LFS_TYPE_DIR) {
-            return LFS_ERR_NOTDIR;
-        }
-
-        int err = lfs_dir_fetch(lfs, dir, entry->d.u.dir);
-        if (err) {
-            return err;
-        }
     }
 }
 
@@ -904,13 +899,8 @@ int lfs_mkdir(lfs_t *lfs, const char *path) {
 
     // fetch parent directory
     lfs_dir_t cwd;
-    int err = lfs_dir_fetch(lfs, &cwd, lfs->root);
-    if (err) {
-        return err;
-    }
-
     lfs_entry_t entry;
-    err = lfs_dir_find(lfs, &cwd, &entry, &path);
+    int err = lfs_dir_find(lfs, &cwd, &entry, &path);
     if (err != LFS_ERR_NOENT || strchr(path, '/') != NULL) {
         return err ? err : LFS_ERR_EXIST;
     }
@@ -954,13 +944,8 @@ int lfs_dir_open(lfs_t *lfs, lfs_dir_t *dir, const char *path) {
     dir->pair[0] = lfs->root[0];
     dir->pair[1] = lfs->root[1];
 
-    int err = lfs_dir_fetch(lfs, dir, dir->pair);
-    if (err) {
-        return err;
-    }
-
     lfs_entry_t entry;
-    err = lfs_dir_find(lfs, dir, &entry, &path);
+    int err = lfs_dir_find(lfs, dir, &entry, &path);
     if (err) {
         return err;
     } else if (entry.d.type != LFS_TYPE_DIR) {
@@ -1302,13 +1287,8 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
 
     // allocate entry for file if it doesn't exist
     lfs_dir_t cwd;
-    int err = lfs_dir_fetch(lfs, &cwd, lfs->root);
-    if (err) {
-        return err;
-    }
-
     lfs_entry_t entry;
-    err = lfs_dir_find(lfs, &cwd, &entry, &path);
+    int err = lfs_dir_find(lfs, &cwd, &entry, &path);
     if (err && (err != LFS_ERR_NOENT || strchr(path, '/') != NULL)) {
         return err;
     }
@@ -1355,6 +1335,10 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
     // allocate buffer if needed
     file->cache.block = 0xffffffff;
     if (lfs->cfg->file_buffer) {
+        if (lfs->files) {
+            // already in use
+            return LFS_ERR_NOMEM;
+        }
         file->cache.buffer = lfs->cfg->file_buffer;
     } else if ((file->flags & 3) == LFS_O_RDONLY) {
         file->cache.buffer = lfs_malloc(lfs->cfg->read_size);
@@ -1814,13 +1798,8 @@ lfs_soff_t lfs_file_size(lfs_t *lfs, lfs_file_t *file) {
 /// General fs operations ///
 int lfs_stat(lfs_t *lfs, const char *path, struct lfs_info *info) {
     lfs_dir_t cwd;
-    int err = lfs_dir_fetch(lfs, &cwd, lfs->root);
-    if (err) {
-        return err;
-    }
-
     lfs_entry_t entry;
-    err = lfs_dir_find(lfs, &cwd, &entry, &path);
+    int err = lfs_dir_find(lfs, &cwd, &entry, &path);
     if (err) {
         return err;
     }
@@ -1855,13 +1834,8 @@ int lfs_remove(lfs_t *lfs, const char *path) {
     }
 
     lfs_dir_t cwd;
-    int err = lfs_dir_fetch(lfs, &cwd, lfs->root);
-    if (err) {
-        return err;
-    }
-
     lfs_entry_t entry;
-    err = lfs_dir_find(lfs, &cwd, &entry, &path);
+    int err = lfs_dir_find(lfs, &cwd, &entry, &path);
     if (err) {
         return err;
     }
@@ -1916,24 +1890,14 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
 
     // find old entry
     lfs_dir_t oldcwd;
-    int err = lfs_dir_fetch(lfs, &oldcwd, lfs->root);
-    if (err) {
-        return err;
-    }
-
     lfs_entry_t oldentry;
-    err = lfs_dir_find(lfs, &oldcwd, &oldentry, &oldpath);
+    int err = lfs_dir_find(lfs, &oldcwd, &oldentry, &oldpath);
     if (err) {
         return err;
     }
 
     // allocate new entry
     lfs_dir_t newcwd;
-    err = lfs_dir_fetch(lfs, &newcwd, lfs->root);
-    if (err) {
-        return err;
-    }
-
     lfs_entry_t preventry;
     err = lfs_dir_find(lfs, &newcwd, &preventry, &newpath);
     if (err && (err != LFS_ERR_NOENT || strchr(newpath, '/') != NULL)) {

tests/test_paths.sh

@@ -90,6 +90,22 @@ tests/test.py << TEST
     lfs_unmount(&lfs) => 0;
 TEST
 
+echo "--- Trailing dot path tests ---"
+tests/test.py << TEST
+    lfs_mount(&lfs, &cfg) => 0;
+    lfs_stat(&lfs, "tea/hottea/", &info) => 0;
+    strcmp(info.name, "hottea") => 0;
+    lfs_stat(&lfs, "tea/hottea/.", &info) => 0;
+    strcmp(info.name, "hottea") => 0;
+    lfs_stat(&lfs, "tea/hottea/./.", &info) => 0;
+    strcmp(info.name, "hottea") => 0;
+    lfs_stat(&lfs, "tea/hottea/..", &info) => 0;
+    strcmp(info.name, "tea") => 0;
+    lfs_stat(&lfs, "tea/hottea/../.", &info) => 0;
+    strcmp(info.name, "tea") => 0;
+    lfs_unmount(&lfs) => 0;
+TEST
+
 echo "--- Root dot dot path tests ---"
 tests/test.py << TEST
     lfs_mount(&lfs, &cfg) => 0;