// virtual file system - transparent access to files in archives;
// allows multiple mount points
//
// Copyright (c) 2004 Jan Wassenberg
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// Contact info:
//   Jan.Wassenberg@stud.uni-karlsruhe.de
//   http://www.stud.uni-karlsruhe.de/~urkt/

#ifndef __VFS_H__
#define __VFS_H__

#include "h_mgr.h"	// Handle
#include "posix.h"	// struct stat
#include "file.h"	// file open flags (renamed)


//
// VFS tree
//

// the VFS doesn't require this length restriction - VFS internal storage
// is not fixed-length. the purpose here is to give an indication of how
// large fixed-size user buffers should be. length includes trailing '\0'.
#define VFS_MAX_PATH 256

// VFS paths are of the form:
// "[dir/{subdir/}]file" or "[dir/{subdir/}]dir[/]".
// in English: '/' as path separator; trailing '/' allowed for dir names;
// no leading '/', since "" is the root dir.

// mount either a single archive or a directory into the VFS at
// <vfs_mount_point>, which is created if it does not yet exist.
// new files override the previous VFS contents if pri(ority) is not lower.
// if <name> is a directory, all archives in that directory (but not
// its subdirs - see add_dirent_cb) are also mounted in alphabetical order.
// name = "." or "./" isn't allowed - see implementation for rationale.
extern int vfs_mount(const char* vfs_mount_point, const char* name, uint pri);

// rebuild the VFS, i.e. re-mount everything. open files are not affected.
// necessary after loose files or directories change, so that the VFS
// "notices" the changes and updates file locations. res calls this after
// FAM reports changes; can also be called from the console after a
// rebuild command. there is no provision for updating single VFS dirs -
// it's not worth the trouble.
extern int vfs_rebuild();

// unmount a previously mounted item, and rebuild the VFS afterwards.
extern int vfs_unmount(const char* name);

extern int vfs_get_path(const char* path, char* vfs_path);


//
// directory entry
//

// information about a directory entry, returned by vfs_next_dirent.
struct vfsDirEnt
{
	// name of directory entry - does not include path.
	// valid until the directory handle is closed. must not be modified!
	// rationale for pointer and invalidation: see vfs_next_dirent.
	const char* name;
};

// open the directory for reading its entries via vfs_next_dirent.
// directory contents are cached here; subsequent changes to the dir
// are not returned by this handle. rationale: see VDir definition.
extern Handle vfs_open_dir(const char* dir);

// close the handle to a directory.
// all vfsDirEnt.name strings are now invalid.
extern int vfs_close_dir(Handle& hd);

// return the next remaining directory entry (in alphabetical order) matching
// filter, or a negative error code on error (e.g. end of directory reached).
// filter values:
// - 0: any file;
// - ".": any file without extension (filename doesn't contain '.');
// - ".ext": any file with extension ".ext" (which must not contain '.');
// - "/": any subdirectory
extern int vfs_next_dirent(Handle hd, vfsDirEnt* ent, const char* filter);


//
// file
//

// return actual path to the specified file:
// "<real_directory>/fn" or "<archive_name>/fn".
extern int vfs_realpath(const char* fn, char* realpath);

// return information about the specified file as in stat(2),
// most notably size. stat buffer is undefined on error.
extern int vfs_stat(const char* fn, struct stat*);

// open the file for synchronous or asynchronous IO. write access is
// requested via FILE_WRITE flag, and is not possible for files in archives.
// flags defined in file.h
extern Handle vfs_open(const char* fn, uint flags = 0);

// close the handle to a file.
extern int vfs_close(Handle& h);


//
// memory mapping
//

// map the entire file <hf> into memory. if already currently mapped,
// return the previous mapping (reference-counted).
// output parameters are zeroed on failure.
//
// the mapping will be removed (if still open) when its file is closed.
// however, map/unmap calls should still be paired so that the mapping
// may be removed when no longer needed.
extern int vfs_map(Handle hf, uint flags, void*& p, size_t& size);

// decrement the reference count for the mapping belonging to file <f>.
// fail if there are no references; remove the mapping if the count reaches 0.
//
// the mapping will be removed (if still open) when its file is closed.
// however, map/unmap calls should still be paired so that the mapping
// may be removed when no longer needed.
extern int vfs_unmap(Handle hf);


//
// asynchronous I/O
//

// begin transferring <size> bytes, starting at <ofs>. get result
// with vfs_wait_read; when no longer needed, free via vfs_discard_io.
extern Handle vfs_start_io(Handle hf, off_t ofs, size_t size, void* buf);

// wait until the transfer <hio> completes, and return its buffer.
// output parameters are zeroed on error.
extern int vfs_wait_io(Handle hio, void*& p, size_t& size);

// finished with transfer <hio> - free its buffer (returned by vfs_wait_read).
extern int vfs_discard_io(Handle& hio);


//
// synchronous I/O
//

// try to transfer <size> bytes, starting at <ofs>.
// (read or write access was chosen at file-open time).
// return bytes of actual data transferred, or a negative error code.
// TODO: buffer types
extern ssize_t vfs_io(Handle hf, off_t ofs, size_t size, void*& p);

// load the entire file <fn> into memory; return a memory handle to the
// buffer and its address/size. output parameters are zeroed on failure.
extern Handle vfs_load(const char* fn, void*& p, size_t& size);


#endif	// #ifndef __VFS_H__