vac.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

typedef struct DirEntry DirEntry;
typedef struct MetaBlock MetaBlock;
typedef struct MetaEntry MetaEntry;

enum {
	MetaMagic = 0x5656fc7a,
	MetaHeaderSize = 12,
	MetaIndexSize = 4,
	IndexEntrySize = 8,
	DirMagic = 0x1c4d9072,
};

/*
 * Mode bits
 */
enum {
	ModeOtherExec = (1<<0),
	ModeOtherWrite = (1<<1),
	ModeOtherRead = (1<<2),
	ModeGroupExec = (1<<3),
	ModeGroupWrite = (1<<4),
	ModeGroupRead = (1<<5),
	ModeOwnerExec = (1<<6),
	ModeOwnerWrite = (1<<7),
	ModeOwnerRead = (1<<8),
	ModeSticky = (1<<9),
	ModeSetUid = (1<<10),
	ModeSetGid = (1<<11),
	ModeAppend = (1<<12),		/* append only file */
	ModeExclusive = (1<<13),	/* lock file - plan 9 */
	ModeLink = (1<<14),		/* sym link */
	ModeDir	= (1<<15),		/* duplicate of DirEntry */
	ModeHidden = (1<<16),		/* MS-DOS */
	ModeSystem = (1<<17),		/* MS-DOS */
	ModeArchive = (1<<18),		/* MS-DOS */
	ModeTemporary = (1<<19),	/* MS-DOS */
	ModeSnapshot = (1<<20),		/* read only snapshot */
};

/* optional directory entry fields */
enum {
	DePlan9 = 1,	/* not valid in version >= 9 */
	DeNT,		/* not valid in version >= 9 */
	DeQidSpace,
	DeGen,		/* not valid in version >= 9 */
};

struct DirEntry {
	char *elem;		/* path element */
	ulong entry;		/* entry in directory for data */
	ulong gen;		/* generation of data entry */
	ulong mentry;		/* entry in directory for meta */
	ulong mgen;		/* generation of meta entry */
	uvlong size;		/* size of file */
	uvlong qid;		/* unique file id */

	char *uid;		/* owner id */
	char *gid;		/* group id */
	char *mid;		/* last modified by */
	ulong mtime;		/* last modified time */
	ulong mcount;		/* number of modifications: can wrap! */
	ulong ctime;		/* directory entry last changed */
	ulong atime;		/* last time accessed */
	ulong mode;		/* various mode bits */

	/* plan 9 */
	int plan9;
	uvlong p9path;
	ulong p9version;

	/* sub space of qid */
	int qidSpace;
	uvlong qidOffset;	/* qid offset */
	uvlong qidMax;		/* qid maximum */
};

struct MetaEntry {
	uchar *p;
	ushort size;
};

struct MetaBlock {
	int maxsize;		/* size of block */
	int size;		/* size used */
	int free;		/* free space within used size */
	int maxindex;		/* entries allocated for table */
	int nindex;		/* amount of table used */
	int botch;		/* compensate for my stupidity */
	uchar *buf;
};

void	deCleanup(DirEntry*);
void	deCopy(DirEntry*, DirEntry*);
int	deSize(DirEntry*);
void	dePack(DirEntry*, MetaEntry*);
int	deUnpack(DirEntry*, MetaEntry*);

void	mbInit(MetaBlock*, uchar*, int, int);
int	mbUnpack(MetaBlock*, uchar*, int);
void	mbInsert(MetaBlock*, int, MetaEntry*);
void	mbDelete(MetaBlock*, int);
void	mbPack(MetaBlock*);
uchar	*mbAlloc(MetaBlock*, int);
int	mbResize(MetaBlock*, MetaEntry*, int);
int	mbSearch(MetaBlock*, char*, int*, MetaEntry*);

void	meUnpack(MetaEntry*, MetaBlock*, int);