typedef struct Alarm	Alarm;
typedef struct Alarms	Alarms;
typedef struct Block	Block;
typedef struct Blist	Blist;
typedef struct Chan	Chan;
typedef struct Dev	Dev;
typedef struct Dirtab	Dirtab;
typedef struct Env	Env;
typedef struct Envp	Envp;
typedef struct Envval	Envval;
typedef struct Etherpkt	Etherpkt;
typedef struct List	List;
typedef struct Mount	Mount;
typedef struct Mtab	Mtab;
typedef struct Note	Note;
typedef struct Orig	Orig;
typedef struct PTE	PTE;
typedef struct Page	Page;
typedef struct Pgrp	Pgrp;
typedef struct Proc	Proc;
typedef struct Qinfo	Qinfo;
typedef struct QLock	QLock;
typedef struct Queue	Queue;
typedef struct Ref	Ref;
typedef struct Rendez	Rendez;
typedef struct Seg	Seg;
typedef struct Stream	Stream;

typedef int Devgen(Chan*, Dirtab*, int, int, Dir*);

struct List
{
	void	*next;
};

struct Ref
{
	Lock;
	int	ref;
};

struct Rendez
{
	Lock;
	Proc	*p;
};

struct QLock
{
	Proc	*head;			/* next process waiting for object */
	Proc	*tail;			/* last process waiting for object */
	Lock	use;			/* to use object */
	Lock	queue;			/* to access list */
};

struct Alarm
{
	List;
	Lock;
	int	busy;
	long	dt;		/* may underflow in clock(); must be signed */
	void	(*f)(void*);
	void	*arg;
};

struct Alarms
{
	QLock;
	Proc	*head;
};

/* Block.flags */
#define S_DELIM 0x80
#define S_CLASS 0x07

/* Block.type */
#define M_DATA 0
#define M_CTL 1
#define M_HANGUP 2

struct Block
{
	Block	*next;
	uchar	*rptr;		/* first unconsumed byte */
	uchar	*wptr;		/* first empty byte */
	uchar	*lim;		/* 1 past the end of the buffer */
	uchar	*base;		/* start of the buffer */
	uchar	flags;
	uchar	type;
};

struct Blist {
	Lock;
	Block	*first;		/* first data block */
	Block	*last;		/* last data block */
	long	len;		/* length of list in bytes */
	int	nb;		/* number of blocks in list */
};

/*
 * Access types in namec
 */
enum
{
	Aaccess,	/* as in access, stat */
	Atodir,		/* as in chdir */
	Aopen,		/* for i/o */
	Amount,		/* to be mounted upon */
	Acreate,	/* file is to be created */
};

/*
 *  Chan.flags
 */
#define	COPEN	1	/* for i/o */
#define	CMOUNT	2	/* is result of a mount/bind */
#define	CCREATE	4	/* permits creation if CMOUNT */
#define	CCEXEC	8	/* close on exec */
#define	CFREE	16	/* not in use */

struct Chan
{
	QLock	rdl;			/* read access */
	QLock	wrl;			/* write access */
	Ref;
	union{
		Chan	*next;		/* allocation */
		ulong	offset;		/* in file */
	};
	ushort	type;
	ushort	dev;
	ushort	mode;			/* read/write */
	ushort	flag;
	Qid	qid;
	Mount	*mnt;			/* mount point that derived Chan */
	ulong	mountid;
	int	fid;			/* for devmnt */
	union {
		Stream	*stream;	/* for stream channels */
		void	*aux;
		Qid	pgrpid;		/* for #p/notepg */
		int	mntindex;	/* for devmnt */
	};
	Chan	*mchan;			/* channel to mounted server */
	Qid	mqid;			/* qid of root of mount point */
};

struct Dev
{
	void	 (*reset)(void);
	void	 (*init)(void);
	Chan	*(*attach)(char*);
	Chan	*(*clone)(Chan*, Chan*);
	int	 (*walk)(Chan*, char*);
	void	 (*stat)(Chan*, char*);
	Chan	*(*open)(Chan*, int);
	void	 (*create)(Chan*, char*, int, ulong);
	void	 (*close)(Chan*);
	long	 (*read)(Chan*, void*, long, ulong);
	long	 (*write)(Chan*, void*, long, ulong);
	void	 (*remove)(Chan*);
	void	 (*wstat)(Chan*, char*);
};

struct Dirtab
{
	char	name[NAMELEN];
	Qid	qid;
	long	length;
	long	perm;
};

struct Env
{
	Lock;
	Envval	*val;
	char	name[NAMELEN];
	Env	*next;			/* in chain of Envs for a pgrp */
	int	pgref;			/* # pgrps pointing here */
};

struct Envp
{
	Env	*env;
	int	chref;			/* # chans from pgrp pointing here */
};

/*
 *  Ethernet packet buffers.
 */
struct Etherpkt {
	uchar d[6];
	uchar s[6];
	uchar type[2];
	uchar data[1500];
	uchar crc[4];
};
#define	ETHERMINTU	60	/* minimum transmit size */
#define	ETHERMAXTU	1514	/* maximum transmit size */
#define ETHERHDRSIZE	14	/* size of an ethernet header */

struct Mount
{
	Ref;				/* also used as a lock when playing lists */
	short	term;			/* terminates list */
	ulong	mountid;
	Mount	*next;
	Chan	*c;			/* channel replacing underlying channel */
};

struct Mtab
{
	Chan	*c;			/* channel mounted upon */
	Mount	*mnt;			/* what's mounted upon it */
};

enum{
	NUser,				/* note provided externally */
	NExit,				/* process should exit */
	NDebug,				/* process should hang */
};

struct Note
{
	char	msg[ERRLEN];
	int	flag;			/* whether system posted it */
};

#define	OWRPERM	0x01	/* write permission */
#define	OPURE	0x02	/* original data mustn't be written */
#define	OCACHED	0x04	/* cached; don't discard on exit */

struct Orig
{
	Lock;
	Orig	*next;			/* for allocation */
	ushort	nproc;			/* processes using it */
	ushort	npage;			/* sum of refs of pages in it */
	ushort	flag;
	ulong	va;			/* va of 0th pte */
	ulong	npte;			/* #pte's in list */
	PTE	*pte;
	Chan	*chan;			/* channel deriving segment (if open) */
	ushort	type;			/* of channel (which could be non-open) */
	Qid	qid;
	Chan	*mchan;
	Qid	mqid;
	ulong	minca;			/* base of region in chan */
	ulong	maxca;			/* end of region in chan */
};

struct Page
{
	Orig	*o;			/* origin of segment owning page */
	ulong	va;			/* virtual address */
	ulong	pa;			/* physical address */
	ushort	ref;
	Page	*next;
	Page	*prev;
};

struct Pgrp
{
	Ref;				/* also used as a lock when mounting */
	Pgrp	*next;
	int	index;			/* index in pgrp table */
	ulong	pgrpid;
	char	user[NAMELEN];
	int	nmtab;			/* highest active mount table entry, +1 */
	int	nenv;			/* highest active env table entry, +1 */
	QLock	debug;			/* single access via devproc.c */
	Mtab	*mtab;
	Envp	*etab;
};

enum					/* Argument to forkpgrp call */
{
	FPall 	  = 0,			/* Concession to back portablility */
	FPnote 	  = 1,
	FPnamespc = 2,
	FPenv	  = 4,
	FPclear	  = 8,
};

/*
 *  process memory segments
 */
#define	SSEG	0
#define	TSEG	1
#define	DSEG	2
#define	BSEG	3
#define	ESEG	4	/* used by exec to build new stack */

struct Seg
{
	Proc	*proc;			/* process owning this segment */
	Orig	*o;			/* root list of pte's */
	ulong	minva;			/* va of 0th pte (not necessarily Seg->o->va) */
	ulong	maxva;			/* va of last pte */
	PTE	*mod;			/* list of modified pte's */
	ulong	pad[3]; /**/
};

/*
 * Process states
 */
enum
{
	Dead = 0,
	Moribund,
	Zombie,
	Ready,
	Scheding,
	Running,
	Queueing,
	MMUing,
	Exiting,
	Inwait,
	Wakeme,
	Broken,
};

/*
 * Proc.time
 */
enum
{
	TUser,
	TSys,
	TReal,
	TCUser,
	TCSys,
	TCReal,
};

struct Proc
{
	Label	sched;
	Mach	*mach;			/* machine running this proc */
	char	text[NAMELEN];
	Proc	*rnext;			/* next process in run queue */
	Proc	*qnext;			/* next process on queue for a QLock */
	QLock	*qlock;			/* address of qlock being queued for DEBUG */
	int	state;
	Page	*upage;			/* BUG: should be unlinked from page list */
	Seg	seg[NSEG];
	ulong	bssend;			/* initial top of bss seg */
	ulong	pid;
	int	nchild;
	QLock	wait;			/* exiting children to be waited for */
	Waitmsg	waitmsg;		/* this is large but must be addressable */
	Proc	*child;
	Proc	*parent;
	Pgrp	*pgrp;
	ulong	parentpid;
	ulong	time[6];		/* User, Sys, Real; child U, S, R */
	short	exiting;
	short	insyscall;
	int	fpstate;
	Lock	debug;			/* to access debugging elements of User */
	Rendez	*r;			/* rendezvous point slept on */
	Rendez	sleep;			/* place for tsleep and syssleep */
	int	wokeup;			/* whether sleep was interrupted */
	ulong	pc;			/* DEBUG only */
	int	kp;			/* true if a kernel process */
	Proc	*palarm;		/* Next alarm time */
	ulong	alarm;			/* Time of call */

	/*
	 *  machine specific MMU goo
	 */
	PMMU;
};

struct PTE
{
	Proc	*proc;			/* process owning this PTE (0 in Orig) */
	PTE	*nextmod;		/* next at this va */
	PTE	*nextva;		/* next in this proc at higher va */
	Page	*page;
};

/*
 *  operations available to a queue
 */
struct Qinfo
{
	void (*iput)(Queue*, Block*);	/* input routine */
	void (*oput)(Queue*, Block*);	/* output routine */
	void (*open)(Queue*, Stream*);
	void (*close)(Queue*);
	char *name;
	void (*reset)(void);		/* initialization */
	Qinfo *next;
};

/*
 *  Queue.flag
 */
#define QHUNGUP	0x1	/* flag bit meaning the stream has been hung up */
#define QINUSE	0x2
#define QHIWAT	0x4	/* queue has gone past the high water mark */	
#define QDEBUG	0x8

struct Queue {
	Blist;
	int	flag;
	Qinfo	*info;		/* line discipline definition */
	Queue	*other;		/* opposite direction, same line discipline */
	Queue	*next;		/* next queue in the stream */
	void	(*put)(Queue*, Block*);
	QLock	rlock;		/* mutex for processes sleeping at r */
	Rendez	r;		/* standard place to wait for flow control */
	Rendez	*rp;		/* where flow control wakeups go to */
	void	*ptr;		/* private info for the queue */
};

struct Stream {
	QLock;			/* structure lock */
	short	inuse;		/* number of processes in stream */
	short	opens;		/* number of processes with stream open */
	ushort	hread;		/* number of reads after hangup */
	ushort	type;		/* correlation with Chan */
	ushort	dev;		/* ... */
	ushort	id;		/* ... */
	QLock	rdlock;		/* read lock */
	Queue	*procq;		/* write queue at process end */
	Queue	*devq;		/* read queue at device end */
	Block	*err;		/* error message from down stream */
	int	forcedelim;	/* force a delimiter before the next message */
};

/*
 *  useful stream macros
 */
#define	RD(q)		((q)->other < (q) ? (q->other) : q)
#define	WR(q)		((q)->other > (q) ? (q->other) : q)
#define GLOBAL(a)	(((ulong)(a)) & 0x80000000)
#define STREAMTYPE(x)	((x)&0x1f)
#define STREAMID(x)	(((x)&~CHDIR)>>5)
#define STREAMQID(i,t)	(((i)<<5)|(t))
#define PUTNEXT(q,b)	(*(q)->next->put)((q)->next, b)
#define BLEN(b)		((b)->wptr - (b)->rptr)
#define QFULL(q)	((q)->flag & QHIWAT)
#define FLOWCTL(q)	{ if(QFULL(q->next)) flowctl(q); }

/*
 *  stream file qid's & high water mark
 */
enum {
	Shighqid = STREAMQID(1,0) - 1,
	Sdataqid = Shighqid,
	Sctlqid = Sdataqid-1,
	Slowqid = Sctlqid,
	Streamhi= (9*1024),	/* byte count high water mark */
	Streambhi= 32,		/* block count high water mark */
};

#define	PRINTSIZE	256
#define	NUMSIZE	12		/* size of formatted number */

extern	FPsave	initfp;
extern	Conf	conf;
extern	ulong	initcode[];
extern	Dev	devtab[];
extern	char	devchar[];
extern	char	user[NAMELEN];
extern	char	*errstrtab[];
extern	char	*statename[];

#define	CHDIR	0x80000000L
#define	CHAPPEND 0x40000000L
#define	CHEXCL	0x20000000L