[unix-history] / .ref-BSD-2 / src / ex / ex_temp.h

/* Copyright (c) 1979 Regents of the University of California */
/*
 * The editor uses a temporary file for files being edited, in a structure
 * similar to that of ed.  The first block of the file is used for a header
 * block which guides recovery after editor/system crashes.
 * Lines are represented in core by a pointer into the temporary file which
 * is packed into 16 bits.  15 of these bits index the temporary file,
 * the 16'th is used by global commands.  The parameters below control
 * how much the 15 bits are shifted left before they index the temp file.
 * Larger shifts give more slop in the temp file but allow larger files
 * to be edited.
 *
 * The editor does not garbage collect the temporary file.  When a new
 * file is edited, the temporary file is rather discarded and a new one
 * created for the new file.  Garbage collection would be rather complicated
 * in ex because of the general undo, and in any case would require more
 * work when throwing lines away because marks would have be carefully
 * checked before reallocating temporary file space.  Said another way,
 * each time you create a new line in the temporary file you get a unique
 * number back, and this is a property used by marks.
 *
 * The following temp file parameters allow 256k bytes in the temporary
 * file.  By changing to the numbers in comments you can get 512k.
 * By typedefing line to long (32 bit) integers you could get much more
 * space in the temp file with (then) no waste.  This would double core
 * requirements and would probably require some editor debugging.
 */
#define	BLKMSK	0777		/* 01777 */
#define	BNDRY	8		/* 16 */
#define	INCRMT	0200		/* 0100 */
#define	LBTMSK	0770		/* 0760 */
#define	NMBLKS	506		/* 1018 */
#define	OFFBTS	7		/* 6 */
#define	OFFMSK	0177		/* 077 */
#define	SHFT	2		/* 3 */

/*
 * The editor uses three buffers into the temporary file (ed uses two
 * and is very similar).  These are two read buffers and one write buffer.
 * Basically, the editor deals with the file as a sequence of 512 character
 * blocks (BUFSIZ).  Each block contains some number of lines (and lines
 * can run across block boundaries.
 *
 * New lines are written into the last block in the temporary file
 * which is in core as obuf.  When a line is needed which isn't in obuf,
 * then it is brought into an input buffer.  As there are two, the choice
 * is to take the buffer into which the last read (of the two) didn't go.
 * Thus this is a 2 buffer LRU replacement strategy.  Measurement
 * shows that this saves roughly 25% of the buffer reads over a one
 * input buffer strategy.  Since the editor (on our VAX over 1 week)
 * spends (spent) roughly 30% of its time in the system read routine,
 * this can be a big help.
 */
bool	hitin2;			/* Last read hit was ibuff2 not ibuff */
bool	ichang2;		/* Have actually changed ibuff2 */
bool	ichanged;		/* Have actually changed ibuff */
short	iblock;			/* Temp file block number of ibuff (or -1) */
short	iblock2;		/* Temp file block number of ibuff2 (or -1) */
short	ninbuf;			/* Number useful chars left in input buffer */
short	nleft;			/* Number usable chars left in output buffer */
short	oblock;			/* Temp file block number of obuff (or -1) */
short	tline;			/* Current temp file ptr */

char	ibuff[BUFSIZ];
char	ibuff2[BUFSIZ];
char	obuff[BUFSIZ];

/*
 * Structure of the descriptor block which resides
 * in the first block of the temporary file and is
 * the guiding light for crash recovery.
 *
 * As the Blocks field below implies, there are temporary file blocks
 * devoted to (some) image of the incore array of pointers into the temp
 * file.  Thus, to recover from a crash we use these indices to get the
 * line pointers back, and then use the line pointers to get the text back.
 * Except for possible lost lines due to sandbagged I/O, the entire
 * file (at the time of the last editor "sync") can be recovered from
 * the temp file.
 */

/* This definition also appears in expreserve.c... beware */
struct 	header {
	time_t	Time;			/* Time temp file last updated */
	short	Uid;
	short	Flines;			/* Number of lines in file */
	char	Savedfile[FNSIZE];	/* The current file name */
	short	Blocks[LBLKS];		/* Blocks where line pointers stashed */
} H;

#define	uid		H.Uid
#define	flines		H.Flines
#define	savedfile	H.Savedfile
#define	blocks		H.Blocks
Commit	Line	Data
a3869972 BJ	1	/* Copyright (c) 1979 Regents of the University of California */
	2	/*
	3	* The editor uses a temporary file for files being edited, in a structure
	4	* similar to that of ed. The first block of the file is used for a header
	5	* block which guides recovery after editor/system crashes.
	6	* Lines are represented in core by a pointer into the temporary file which
	7	* is packed into 16 bits. 15 of these bits index the temporary file,
	8	* the 16'th is used by global commands. The parameters below control
	9	* how much the 15 bits are shifted left before they index the temp file.
	10	* Larger shifts give more slop in the temp file but allow larger files
	11	* to be edited.
	12	*
	13	* The editor does not garbage collect the temporary file. When a new
	14	* file is edited, the temporary file is rather discarded and a new one
	15	* created for the new file. Garbage collection would be rather complicated
	16	* in ex because of the general undo, and in any case would require more
	17	* work when throwing lines away because marks would have be carefully
	18	* checked before reallocating temporary file space. Said another way,
	19	* each time you create a new line in the temporary file you get a unique
	20	* number back, and this is a property used by marks.
	21	*
	22	* The following temp file parameters allow 256k bytes in the temporary
	23	* file. By changing to the numbers in comments you can get 512k.
	24	* By typedefing line to long (32 bit) integers you could get much more
	25	* space in the temp file with (then) no waste. This would double core
	26	* requirements and would probably require some editor debugging.
	27	*/
	28	#define BLKMSK 0777 /* 01777 */
	29	#define BNDRY 8 /* 16 */
	30	#define INCRMT 0200 /* 0100 */
	31	#define LBTMSK 0770 /* 0760 */
	32	#define NMBLKS 506 /* 1018 */
	33	#define OFFBTS 7 /* 6 */
	34	#define OFFMSK 0177 /* 077 */
	35	#define SHFT 2 /* 3 */
	36
	37	/*
	38	* The editor uses three buffers into the temporary file (ed uses two
	39	* and is very similar). These are two read buffers and one write buffer.
	40	* Basically, the editor deals with the file as a sequence of 512 character
	41	* blocks (BUFSIZ). Each block contains some number of lines (and lines
	42	* can run across block boundaries.
	43	*
	44	* New lines are written into the last block in the temporary file
	45	* which is in core as obuf. When a line is needed which isn't in obuf,
	46	* then it is brought into an input buffer. As there are two, the choice
	47	* is to take the buffer into which the last read (of the two) didn't go.
	48	* Thus this is a 2 buffer LRU replacement strategy. Measurement
	49	* shows that this saves roughly 25% of the buffer reads over a one
	50	* input buffer strategy. Since the editor (on our VAX over 1 week)
	51	* spends (spent) roughly 30% of its time in the system read routine,
	52	* this can be a big help.
	53	*/
	54	bool hitin2; /* Last read hit was ibuff2 not ibuff */
	55	bool ichang2; /* Have actually changed ibuff2 */
	56	bool ichanged; /* Have actually changed ibuff */
	57	short iblock; /* Temp file block number of ibuff (or -1) */
	58	short iblock2; /* Temp file block number of ibuff2 (or -1) */
	59	short ninbuf; /* Number useful chars left in input buffer */
	60	short nleft; /* Number usable chars left in output buffer */
	61	short oblock; /* Temp file block number of obuff (or -1) */
	62	short tline; /* Current temp file ptr */
	63
	64	char ibuff[BUFSIZ];
65	char ibuff2[BUFSIZ];
66	char obuff[BUFSIZ];
67
68	/*
69	* Structure of the descriptor block which resides
70	* in the first block of the temporary file and is
71	* the guiding light for crash recovery.
72	*
73	* As the Blocks field below implies, there are temporary file blocks
74	* devoted to (some) image of the incore array of pointers into the temp
75	* file. Thus, to recover from a crash we use these indices to get the
76	* line pointers back, and then use the line pointers to get the text back.
77	* Except for possible lost lines due to sandbagged I/O, the entire
78	* file (at the time of the last editor "sync") can be recovered from
79	* the temp file.
80	*/
81
82	/* This definition also appears in expreserve.c... beware */
83	struct header {
84	time_t Time; /* Time temp file last updated */
85	short Uid;
86	short Flines; /* Number of lines in file */
87	char Savedfile[FNSIZE]; /* The current file name */
88	short Blocks[LBLKS]; /* Blocks where line pointers stashed */
89	} H;
90
91	#define uid H.Uid
92	#define flines H.Flines
93	#define savedfile H.Savedfile
94	#define blocks H.Blocks