dat.h

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

enum {
	Maxtrack		= 200,
	Ntrack		= Maxtrack+1,
	BScdrom		= 2048,
	BScdda		= 2352,
	BScdxa		= 2336,
	BSmax		= 2352,
	Nalloc		= 12*BScdda,
	DictBlock	= 1,

	TypeDA		= 0,		/* Direct Access */
	TypeSA		= 1,		/* Sequential Access */
	TypeWO		= 4,		/* Worm */
	TypeCD		= 5,		/* CD-ROM */
	TypeMO		= 7,		/* rewriteable Magneto-Optical */
	TypeMC		= 8,		/* Medium Changer */

	TypeNone	= 0,
	TypeAudio,
	TypeAwritable,
	TypeData,
	TypeDwritable,
	TypeDisk,
	TypeBlank,

	Cwrite = 1<<0,
	Ccdda = 1<<1,

	Nblock = 12,
};

typedef struct Buf Buf;
typedef struct Drive Drive;
typedef struct Track Track;
typedef struct Otrack Otrack;
typedef struct Dev Dev;
typedef struct Msf Msf;	/* minute, second, frame */

struct Msf {
	int m;
	int s;
	int f;
};

struct Track
{
	/* initialized while obtaining the toc (gettoc) */
	vlong	size;		/* total size in bytes */
	long	bs;		/* block size in bytes */
	ulong	beg;		/* beginning block number */
	ulong	end;		/* ending block number */
	int	type;
	Msf	mbeg;
	Msf	mend;


	/* initialized by fs */
	char	name[32];
	int	mode;
	int	mtime;
};

struct DTrack
{
	uchar	name[32];
	uchar	beg[4];
	uchar	end[4];
	uchar	size[8];
	uchar	magic[4];
};

struct Otrack
{
	Track *track;
	Drive *drive;
	int nchange;
	int omode;
	Buf *buf;

	int nref;	/* kept by file server */
};

struct Dev
{
	Otrack* (*openrd)(Drive *d, int trackno);
	Otrack* (*create)(Drive *d, int bs);
	long (*read)(Otrack *t, void *v, long n, long off);
	long (*write)(Otrack *t, void *v, long n);
	void (*close)(Otrack *t);
	int (*gettoc)(Drive*);
	int (*fixate)(Drive *d);
	char* (*ctl)(Drive *d, int argc, char **argv);
	char* (*setspeed)(Drive *d, int r, int w);
};

struct Drive
{
	QLock;
	Scsi;

	int	type;
	int	nopen;
	int	firsttrack;
	int	ntrack;
	int	nchange;
	int	changetime;
	int	nameok;
	int	writeok;
	Track	track[Ntrack];
	ulong	cap;
	uchar	blkbuf[BScdda];
	int	maxreadspeed;
	int	maxwritespeed;
	int	readspeed;
	int	writespeed;
	Dev;

	void *aux;	/* kept by driver */
};

struct Buf
{
	uchar *data;	/* buffer */
	long off;		/* data[0] at offset off in file */
	int bs;		/* block size */
	long ndata;	/* no. valid bytes in data */
	int nblock;	/* total buffer size in blocks */
	int	omode;	/* OREAD, OWRITE */
	long	(*fn)(Buf*, void*, long, long);	/* read, write */

	/* used only by client */
	Otrack *otrack;
};

extern int	vflag;