Module fs::vfs

Virtual Filesystem (VFS) Layer Minimal inode-based VFS with driver registration. Freestanding-safe.

A filesystem driver is a context struct with methods; the traits below name them. Vfs::mount / mount_ro build the VfsOps table from those methods at compile time (one thunk per method, instantiated for the driver's type), so a driver writes no function table of its own:

FsRead      open, read, readdir                  FatCtx, Ext2Ctx
FsWrite     write, unlink, mkdir
FileSystem  FsRead + FsWrite                     TmpfsCtx

struct TmpfsCtx tmp; tmp.init();
vfs_init();
vfs_root.mount("/tmp", &tmp);       // read-write: needs a FileSystem
vfs_root.mount_ro("/sd", &fat);     // read-only: any FsRead

Paths a driver sees are relative to its mountpoint ("/" for the root). A driver need not set VfsNode.fs_ctx: the VFS fills it in.