Added possibility to open multiple files with LFS_NO_MALLOC enabled.

lfs.c

@@ -1283,7 +1283,7 @@ static int lfs_ctz_traverse(lfs_t *lfs,
 
 /// Top level file operations ///
 int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
-        const char *path, int flags) {
+        const char *path, int flags, void *file_buffer) {
     // 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);
@@ -1340,7 +1340,10 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
     }
 
     // allocate buffer if needed
-    if (lfs->cfg->file_buffer) {
+    file->cache.block = 0xffffffff;
+    if (file_buffer) {
+        file->cache.buffer = file_buffer;
+    } else if (lfs->cfg->file_buffer) {
         if (lfs->files) {
             // already in use
             return LFS_ERR_NOMEM;

lfs.h

@@ -334,7 +334,7 @@ int lfs_stat(lfs_t *lfs, const char *path, struct lfs_info *info);
 //
 // Returns a negative error code on failure.
 int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
-        const char *path, int flags);
+        const char *path, int flags, void *file_buffer);
 
 // Close a file
 //