lib: fs: implement mounting filesystems; reading, writing from files

lib/libfs/file.c

@@ -0,0 +1,41 @@
+#include "file.h"
+
+struct fs_inode *fs_file_get_inode(const struct fs_file *f)
+{
+	return f->f_inode;
+}
+
+size_t fs_file_get_cursor(const struct fs_file *f)
+{
+	return f->f_seek;
+}
+
+enum fs_status fs_file_read(
+	struct fs_file *f,
+	struct xpc_buffer *buf,
+	size_t count)
+{
+	if (!f->f_ops || !f->f_ops->f_read) {
+		return FS_ERR_NOT_IMPLEMENTED;
+	}
+
+	off_t seek = f->f_seek;
+	enum fs_status status = f->f_ops->f_read(f, buf, count, &seek);
+	f->f_seek = seek;
+	return status;
+}
+
+enum fs_status fs_file_write(
+	struct fs_file *f,
+	struct xpc_buffer *buf,
+	size_t count)
+{
+	if (!f->f_ops || !f->f_ops->f_write) {
+		return FS_ERR_NOT_IMPLEMENTED;
+	}
+
+	off_t seek = f->f_seek;
+	enum fs_status status = f->f_ops->f_write(f, buf, count, &seek);
+	f->f_seek = seek;
+	return status;
+}