From ec28488329d766a939a28292ffff22fac3963736 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Fri, 1 Mar 2024 20:24:41 -0500
Subject: kernel/amd64: vfs_subr: Add path parsing helper

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/include/sys/vfs.h |  1 +
 sys/kern/vfs_subr.c   | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/sys/include/sys/vfs.h b/sys/include/sys/vfs.h
index 7aafecf..6b96cce 100644
--- a/sys/include/sys/vfs.h
+++ b/sys/include/sys/vfs.h
@@ -40,6 +40,7 @@ struct fs_info *vfs_byname(const char *name);
 
 struct vnode *vfs_path_to_node(const char *path);
 char *vfs_get_fname_at(const char *path, size_t idx);
+int vfs_rootname(const char *path, char **new_path);
 bool vfs_is_valid_path(const char *path);
 ssize_t vfs_hash_path(const char *path);
 #endif /* defined(_KERNEL) */
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 5338a8c..5740edf 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -159,3 +159,60 @@ vfs_alloc_vnode(struct vnode **vnode, struct mount *mp, int type)
     *vnode = new_vnode;
     return 0;
 }
+
+/*
+ * Returns the rootname of a path
+ * For example, "/foo/bar/" will be "foo" and
+ * "/foo/bar/baz" will also be "foo"
+ *
+ * There will be no slashes in the returned string
+ * unless "/" is passed.
+ *
+ * XXX: Returns memory allocated by dynalloc,
+ *      remember to free the memory with dynfree()
+ *
+ * @path: Path to get rootname of
+ * @new_path: New path will be placed here.
+ */
+int
+vfs_rootname(const char *path, char **new_path)
+{
+    char *tmp = NULL;
+    const char *ptr = path;
+    size_t len = 0;
+
+    if (!vfs_is_valid_path(path)) {
+        *new_path = NULL;
+        return -EINVAL;
+    }
+
+    if (*path == '/') {
+        /* Skip first '/' */
+        ++ptr;
+        ++path;
+    }
+
+    for (; *ptr != '\0' && *ptr != '/'; ++ptr) {
+        if (*ptr == '/') {
+            break;
+        }
+        ++len;
+    }
+
+    tmp = dynalloc(sizeof(char) * len + 1);
+    if (tmp == NULL) {
+        *new_path = NULL;
+        return -ENOMEM;
+    }
+
+    if (len == 0) {
+        /* Handle input that is just "/" */
+        tmp[0] = '/';
+        tmp[1] = '\0';
+    } else {
+        memcpy(tmp, path, len + 2);
+    }
+
+    *new_path = tmp;
+    return 0;
+}
-- 
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