From 2e587973eb105ee2d0eaa5cf9c980364af94c330 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fabian=20H=C3=BC=C3=9Fler?= <fabian.huessler@st.ovgu.de>
Date: Fri, 22 Jul 2022 09:23:50 +0200
Subject: [PATCH] sys/vfs_util: add recursive unlink

---
 sys/include/vfs_util.h  |  27 ++++++++
 sys/vfs_util/vfs_util.c | 137 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 164 insertions(+)

diff --git a/sys/include/vfs_util.h b/sys/include/vfs_util.h
index a6ae1ec911..f2e11b95d0 100644
--- a/sys/include/vfs_util.h
+++ b/sys/include/vfs_util.h
@@ -101,6 +101,33 @@ int vfs_file_sha256(const char* file, void *digest,
                     void *work_buf, size_t work_buf_len);
 #endif
 
+/**
+ * @brief   Checks if @p path is a file or a directory.
+ *
+ * This function uses @ref vfs_stat(), so if you need @ref vfs_stat() anyway,
+ * you should not do double work and check it yourself.
+ *
+ * @param[in]   path        Path to check
+ *
+ * @return < 0 on FS error
+ * @return 0 if @p path is a file
+ * @return > 0 if @p path is a directory
+ */
+int vfs_is_dir(const char *path);
+
+/**
+ * @brief    Behaves like `rm -r @p root`.
+ *
+ * @param[in]   root        FS root directory to be deleted
+ * @param[in]   path_buf    Buffer that must be able to store the longest path
+ *                          of the file or directory being deleted
+ * @param[in]   max_size    Size of @p path_buf
+ *
+ * @return < 0 on error
+ * @return 0
+ */
+int vfs_unlink_recursive(const char *root, char *path_buf, size_t max_size);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/sys/vfs_util/vfs_util.c b/sys/vfs_util/vfs_util.c
index adf7e7f13f..be92d0d66e 100644
--- a/sys/vfs_util/vfs_util.c
+++ b/sys/vfs_util/vfs_util.c
@@ -154,3 +154,140 @@ int vfs_file_sha256(const char* file, void *digest,
 
 }
 #endif /* MODULE_HASHES */
+
+int vfs_is_dir(const char *path)
+{
+    assert(path);
+
+    int err;
+    struct stat stat;
+    if (*path != '/') {
+        /* only accept absolute paths */
+        return -EINVAL;
+    }
+    if ((err = vfs_stat(path, &stat)) < 0) {
+        return err;
+    }
+    return ((stat.st_mode & S_IFMT) == S_IFDIR);
+}
+
+/**
+ * @brief   Removes additional "/" slashes from @p path
+ *
+ * @param[in]   path    Path to be prepared
+ */
+static void _vfs_prepare_path(char *path)
+{
+    assert(path);
+    assert(*path == '/');
+
+    int path_len = strlen(path);
+    char *p_write = path; /* end of so far constructed path */
+    int len = 0;
+    const char *p_read = p_write; /* segment to be appended to the path */
+    while (p_read < path + path_len) {
+        len = 0;
+        while (*p_read && *p_read == '/') {
+            p_read++; /* skip slashes */
+        }
+        while (p_read[len] && p_read[len] != '/') {
+            len++; /* length of segment to be copied */
+        }
+        if (*p_read && p_write + len + 1 <= path + path_len) {
+            memmove(p_write + 1, p_read, len);
+            p_write = p_write + len + 1; /* advance write pointer by segment length + 1 */
+            *p_write = p_read[len]; /* either '\0' or '/' */
+        }
+        p_read += len; /* advance read pointer by segment length */
+    }
+    if (*p_write) {
+        *++p_write = '\0';
+    }
+}
+
+int vfs_unlink_recursive(const char *root, char *path_buf, size_t max_size)
+{
+    assert(root);
+    assert(path_buf);
+
+    /* This function works like a Depth-first search (DFS).
+       First, we go as deep as we can into a directory and delete contained files.
+       Then we delete the now empty directory and go to the parent directory
+       and repeat the process. */
+    int err;
+    if (*root != '/' || !strcmp(root, "/")) {
+        /* only accept absolute paths and not the FS root */
+        return -EINVAL;
+    }
+    if (strlen(root) >= max_size) {
+        return -ENOBUFS;
+    }
+    strcpy(path_buf, root);
+    _vfs_prepare_path(path_buf);
+    if (path_buf[strlen(path_buf) - 1] != '/') {
+        if ((err = vfs_is_dir(path_buf)) < 0) {
+            return err; /* early unexpected error */
+        }
+        else if (!err) {
+            /* just a file */
+            return vfs_unlink(path_buf);
+        }
+        strcat(path_buf, "/");
+    }
+    vfs_DIR dir;
+    vfs_dirent_t entry;
+    char seg[VFS_NAME_MAX + 1] = {0}; /* + 1 to append a '/' */
+    size_t seg_len, root_len, fin = strlen(path_buf);
+    while ((root_len = strlen(path_buf)) >= fin) {
+        strcat(path_buf, seg);
+        *seg = '\0';
+        if ((err = vfs_opendir(&dir, path_buf)) < 0) { /* this works with a trailing '/' */
+            return err;
+        }
+        while (vfs_readdir(&dir, &entry) > 0) {
+            if (!strcmp(entry.d_name, "..")) {
+                continue;
+            }
+            seg_len = strlen(entry.d_name);
+            root_len = strlen(path_buf);
+            if (root_len + seg_len >= max_size) {
+                vfs_closedir(&dir);
+                return -ENOBUFS;
+            }
+            strcat(path_buf, entry.d_name);
+            if ((err = vfs_is_dir(path_buf)) < 0) {
+                /* error */
+                vfs_closedir(&dir);
+                return err;
+            }
+            else if (err) {
+                /* is dir */
+                if (*seg == '\0') {
+                    strcat(seg, entry.d_name);
+                    strcat(seg, "/");
+                }
+            }
+            else {
+                /* is file */
+                if ((err = vfs_unlink(path_buf)) < 0) {
+                    vfs_closedir(&dir);
+                    return err;
+                }
+            }
+            path_buf[root_len] = '\0';
+        }
+        vfs_closedir(&dir);
+        if (*seg == '\0') {
+            /* no files and no subdirectory */
+            if ((err = vfs_rmdir(path_buf)) < 0) {
+                return err;
+            }
+            /* go one segment up */
+            char *end = &path_buf[strlen(path_buf) - 1];
+            assert(*end == '/');
+            while (*--end != '/') { }
+            *++end = '\0';
+        }
+    }
+    return 0;
+}