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/*
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 *  format of cache on disk
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 */
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typedef struct Dptr	Dptr;
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typedef struct Dahdr	Dahdr;
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typedef struct Dalloc	Dalloc;
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typedef struct Fphdr	Fphdr;
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typedef struct Fptr	Fptr;
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typedef struct Inode	Inode;
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typedef struct Dihdr	Dihdr;
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typedef struct Dinode	Dinode;
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enum
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{
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	Amagic= 	0xbebeefed,	/* allocation block magic */
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	Imagic=		0xbadc00ce,	/* inode block magic */
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	BtoUL=		8*sizeof(ulong),/* bits in a ulong */
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	CACHENAMELEN=	128
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};
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#define	Indbno		0x80000000	/* indirect block */
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#define	Notabno		0xFFFFFFFF	/* not a block number */
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/*
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 *  Allocation blocks at the begining of the disk.  There are
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 *  enough of these blocks to supply 1 bit for each block on the
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 *  disk;
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 */
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struct Dahdr
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{
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	ulong	magic;
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	ulong	bsize;		/* logical block size */
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	char	name[CACHENAMELEN];
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	short	nab;		/* number of allocation blocks */
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};
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struct Dalloc
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{
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	Dahdr;
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	ulong	bits[1];
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};
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/*
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 *  A pointer to disk data
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 */
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struct Dptr
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{
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	ulong	fbno;		/* file block number */
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	ulong	bno;		/* disk block number */
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	ushort	start;		/* offset into block of valid data */
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	ushort	end;		/* offset into block after valid data */
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};
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/*
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 *  A file descriptor.
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 */
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struct Inode
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{
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	Qid	qid;
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	vlong	length;
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	Dptr	ptr;		/* pointer page */
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	char	inuse;
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};
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/*
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 *  inode blocks (after allocation blocks)
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 */
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struct Dihdr
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{
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	ulong	magic;
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	ulong	nino;		/* number of inodes */
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};
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struct Dinode
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{
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	Dihdr;
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	Inode	inode[1];
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};