/* 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 (32 on VMUNIX). All but the low bit index the temp
* file; the last is used by global commands. The parameters below control
* how much the other bits are shifted left before they index the temp file.
* Larger shifts give more slop in the temp file but allow larger files
* 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.
* For VMUNIX you get more than you could ever want.
* VMUNIX uses long (32 bit) integers giving much more
* space in the temp file and no waste. This doubles core
* requirements but allows files of essentially unlimited size to be edited.
#define BLKMSK 0777 /* 01777 */
#define INCRMT 0200 /* 0100 */
#define LBTMSK 0770 /* 0760 */
#define NMBLKS 506 /* 1018 */
#define OFFMSK 0177 /* 077 */
* 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 BUFSIZ character
* blocks. 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 */
* 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
/* This definition also appears in expreserve.c... beware */
time_t Time
; /* Time temp file last updated */
short Flines
; /* Number of lines in file */
char Savedfile
[FNSIZE
]; /* The current file name */
short Blocks
[LBLKS
]; /* Blocks where line pointers stashed */
#define savedfile H.Savedfile
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