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/* lowbuf.c */
/* Copyright 1995 by Steve Kirkendall */


/* This file contains functions which divide the session file into several
* buffers. These functions use session.c, and are used by buffer.c
*/

#include "elvis.h"
#ifdef FEATURE_RCSID
char id_lowbuf[] = "$Id: lowbuf.c,v 2.46 2003/10/17 17:41:23 steve Exp $";
#endif

/* These control the sizes of some tiny caches for storing line offsets and
* info about random offsets. You can disable these by making them 0. This
* is intended to make lowline() run faster.
*/
#define LINECACHE 4

#if USE_PROTOTYPES
static short checksum(BLK *blk);
static BLKNO delblock(_BLKNO_ blklist, _LBLKNO_ lblkno, COUNT *ncharsptr, COUNT *nlinesptr);
static BLKNO insblock(_BLKNO_ blklist, _LBLKNO_ before, _BLKNO_ chars, _COUNT_ nchars, _COUNT_ nlines);
static BLKNO lockchars(_BLKNO_ bufinfo, _LBLKNO_ lblkno, _BLKNO_ blkno);
static void unlockchars(_BLKNO_ bufinfo, _LBLKNO_ lblkno, _BLKNO_ blkno, int chgchars, int chglines);
static void helpinit(_BLKNO_ bufinfo, void (*bufproc)(_BLKNO_ bufinfo, long nchars, long nlines, long changes, long prevloc, CHAR *name));
#endif

#if LINECACHE
static void clobbercache P_((_BLKNO_ dst));
#endif

/******************************************************************************/
/* Some internal functions... */

/* Compute the checksum for a bufinfo block */
static short checksum(blk)
BLK *blk; /* block whose checksum should be calculated */
{
short oldsum;
register short sum;
register short *scan;

/* remember the old sum, and then force it to 0 temporarily */
oldsum = blk->bufinfo.checksum;
blk->bufinfo.checksum = 0;

/* count the sum, treating the block as an array of BLKNOs. */
for (sum = 0, scan = &blk->sumshorts[o_blksize / sizeof(short)];
scan != blk->sumshorts;
)
{
/* We know that o_blksize is a power of 2, >= 256. We can
* safely assume that sizeof(short) is also a power of 2, <=16,
* so we can safely unroll this loop.
*/
sum += scan[-1] + scan[-2] + scan[-3] + scan[-4]
+ scan[-5] + scan[-6] + scan[-7] + scan[-8]
+ scan[-9] + scan[-10] + scan[-11] + scan[-12]
+ scan[-13] + scan[-14] + scan[-15] + scan[-16];
scan -= 16;
}

/* restore the old sum, but then return the new sum */
blk->bufinfo.checksum = oldsum;
return sum;
}


/* This function deletes one whole CHARS block from a BLKLIST block, and
* returns the BLKNO of the altered version of the block which the "blklist"
* argument referred to. This function is recursive.
*/
static BLKNO delblock(blklist, lblkno, ncharsptr, nlinesptr)
_BLKNO_ blklist; /* a BLKLIST block */
_LBLKNO_ lblkno; /* index into blklist's array of blocks */
COUNT *ncharsptr; /* number of characters deleted */
COUNT *nlinesptr; /* number of lines deleted */
{
BLKNO next;
BLK *blk;

assert(blklist != 0);

/* if the lblkno is in a later block, then delete it recursively
* and watch out for the next blklist being copied-on-write!
*/
if (lblkno >= SES_MAXBLKLIST)
{
blklist = seslock(blklist, ElvTrue, SES_BLKLIST);
blk = sesblk(blklist);
next = delblock(blk->blklist.next, (LBLKNO)(lblkno - SES_MAXBLKLIST), ncharsptr, nlinesptr);
if (next == blk->blklist.next)
{
sesunlock(blklist, ElvFalse);
}
else
{
blk->blklist.next = next;
sesunlock(blklist, ElvTrue);
}
return blklist;
}

/* the doomed lblkno is in this block. Free the char block */
(void)seslock(blklist, ElvFalse, SES_BLKLIST);
blk = sesblk(blklist);
assert(blk->blklist.blk[lblkno].blkno != 0);
sesfree(blk->blklist.blk[lblkno].blkno);

/* copy the chars & lines counts to caller's variables */
if (ncharsptr) *ncharsptr = blk->blklist.blk[lblkno].nchars;
if (nlinesptr) *nlinesptr = blk->blklist.blk[lblkno].nlines;

/* If it is the only block in this blklist (and, by implication,
* this is the final blklist), then free the blklist block.
*/
if (lblkno == 0 && blk->blklist.blk[1].blkno == 0)
{
sesunlock(blklist, ElvFalse);
sesfree(blklist);
return 0;
}
sesunlock(blklist, ElvFalse);

/* shift this blklist's blk[] array to delete the element */
blklist = seslock(blklist, ElvTrue, SES_BLKLIST);
blk = sesblk(blklist);
while (lblkno < SES_MAXBLKLIST - 1)
{
blk->blklist.blk[lblkno] = blk->blklist.blk[lblkno + 1];
lblkno++;
}

/* shift in a 0 (in the last block) or the first item from the
* next blklist block.
*/
if (blk->blklist.next == 0)
{
/* shift in a 0 */
blk->blklist.blk[lblkno].blkno = 0;
blk->blklist.blk[lblkno].nchars = 0;
blk->blklist.blk[lblkno].nlines = 0;
}
else
{
/* shift in the first element of the next blklist's blk[] */
next = blk->blklist.next;
(void)seslock(next, ElvFalse, SES_BLKLIST);
blk->blklist.blk[lblkno] = sesblk(next)->blklist.blk[0];
sesalloc(blk->blklist.blk[lblkno].blkno, SES_CHARS);
sesunlock(next, ElvFalse);

/* recursively shift following blklists' blk[] arrays */
blk->blklist.next = delblock(next, 0, (COUNT *)0, (COUNT *)0);
}

/* return BLKNO of altered version of this blklist */
sesunlock(blklist, ElvTrue);
return blklist;
}

/* This function inserts a CHARS block into the blklist, at a given LBLKNO.
* If necessary, it will also allocate a new BLKLIST block to extend the
* blklist.
*
* This function is recursive; each invocation returns the blklist argument,
* or the blkno of an updated version of that block.
*/
static BLKNO insblock(blklist, before, chars, nchars, nlines)
_BLKNO_ blklist; /* a BLKLIST */
_LBLKNO_ before; /* where to insert a block */
_BLKNO_ chars; /* the CHARS block to be inserted */
_COUNT_ nchars; /* number of character in "chars" */
_COUNT_ nlines; /* number of lines in "chars" */
{
BLKNO next; /* the block after blklist */
BLK *blk; /* contents of a BUFINFO or BLKLIST block */
int i;

assert(chars != 0 && nchars != 0 && nchars < SES_MAXCHARS && nlines <= nchars);

/* if no blklist, then create one */
if (!blklist)
{
assert(before == 0);

/* give the buffer its first blkno */
blklist = sesalloc(0, SES_BLKLIST);

/* make the new CHARS block be its first entry */
(void)seslock(blklist, ElvTrue, SES_BLKLIST);
blk = sesblk(blklist);
blk->blklist.blk[0].blkno = chars;
blk->blklist.blk[0].nchars = nchars;
blk->blklist.blk[0].nlines = nlines;
sesunlock(blklist, ElvTrue);
}
/* should the chars block be inserted into this blklist block? */
else if (before < SES_MAXBLKLIST)
{
/* yes! Get this blocklist block */
blklist = seslock(blklist, ElvTrue, SES_BLKLIST);
blk = sesblk(blklist);

/* if the blklist is full, then insert the last item of
* this block before the first item in the next block.
*/
i = SES_MAXBLKLIST - 1;
if (blk->blklist.blk[i].blkno)
{
blk->blklist.next = insblock(blk->blklist.next, 0,
blk->blklist.blk[i].blkno,
blk->blklist.blk[i].nchars,
blk->blklist.blk[i].nlines);
}

/* insert the chars block into this blklist block */
for (; (unsigned)i > before; --i)
{
blk->blklist.blk[i] = blk->blklist.blk[i - 1];
}
blk->blklist.blk[before].blkno = chars;
blk->blklist.blk[before].nchars = nchars;
blk->blklist.blk[before].nlines = nlines;

/* done! */
sesunlock(blklist, ElvTrue);
}
else /* chars will be inserted into a later blklist block */
{
blklist = seslock(blklist, ElvTrue, SES_BLKLIST);
blk = sesblk(blklist);
next = insblock(blk->blklist.next, (LBLKNO)(before - SES_MAXBLKLIST), chars, nchars, nlines);
if (blk->blklist.next != next)
{
blk->blklist.next = next;
sesunlock(blklist, ElvTrue);
}
else
{
sesunlock(blklist, ElvFalse);
}
}
return blklist;
}

/* This function locks a CHARS block for writing. Doing this may require
* doing a copy-on-write, which may in turn require doing a copy-on-write
* of the blklist block which refers to the CHARS block, and so on back to
* the bufinfo block. Returns the BLKNO of the CHARS block.
*/
static BLKNO lockchars(bufinfo, lblkno, blkno)
_BLKNO_ bufinfo; /* a BUFINFO block */
_LBLKNO_ lblkno; /* index info BLKLIST of the CHARS block */
_BLKNO_ blkno; /* physical block number of the CHARS block */
{
BLKNO locked; /* BLKNO of various blocks after locking */
BLKNO blklist, next; /* BLKLIST blocks */
BLK *blk;

assert(bufinfo != 0 && blkno != 0);
#ifdef DEBUG_SCAN
scan__nobuf();
#endif

/* step 1: lock the chars block. If its BLKNO remains unchanged,
* then we're done.
*/
locked = seslock(blkno, ElvTrue, SES_CHARS);
if (locked == blkno)
{
return blkno;
}

/* step 2: fetch the bufinfo block. */
next = seslock(bufinfo, ElvFalse, SES_BUFINFO);
assert(next == bufinfo);
blk = sesblk(bufinfo);

/* step 3: lock the blklist block which contains the requested
* chars block. Since blklist blocks are never shared, this
* shouldn't require copy-on-write.
*/
blklist = seslock(blk->bufinfo.first, ElvTrue, SES_BLKLIST);
blk = sesblk(blklist);
while (lblkno >= SES_MAXBLKLIST)
{
next = seslock(blk->blklist.next, ElvTrue, SES_BLKLIST);
assert(next != 0);
sesunlock(blklist, ElvFalse);
blklist = next;
lblkno -= SES_MAXBLKLIST;
blk = sesblk(blklist);
}
assert(blk->blklist.blk[lblkno].blkno == blkno);

/* step 4: replace the blkno in the blklist */
blk->blklist.blk[lblkno].blkno = locked;
sesunlock(blklist, ElvTrue);
sesunlock(bufinfo, ElvFalse);
return locked;
}

/* This function unlocks a CHARS block which has been locked by lockchars(),
* and then updates the nchars and nlines statistics in the blklist block.
* It is assumed that no copy-on-write will be necessary for the blklist block;
* if it was, lockchars() would have done it.
*/
static void unlockchars(bufinfo, lblkno, blkno, chgchars, chglines)
_BLKNO_ bufinfo; /* a BUFINFO block */
_LBLKNO_ lblkno; /* index into BLKLIST of the CHARS block */
_BLKNO_ blkno; /* physical block number of CHARS block */
int chgchars; /* change in the number of characters */
int chglines; /* change in the number of lines */
{
BLKNO blklist, next;
BLK *blk;

assert(bufinfo != 0 && blkno != 0);

/* update block statistics, if necessary */
if (chgchars != 0 || chglines != 0)
{
/* locate the BLKLIST block that refers to this CHARS block */
(void)seslock(bufinfo, ElvFalse, SES_BUFINFO);
blklist = sesblk(bufinfo)->bufinfo.first;
assert(blklist != 0);
sesunlock(bufinfo, ElvFalse);
for (; lblkno >= SES_MAXBLKLIST; lblkno -= SES_MAXBLKLIST)
{
(void)seslock(blklist, ElvFalse, SES_BLKLIST);
next = sesblk(blklist)->blklist.next;
sesunlock(blklist, ElvFalse);
blklist = next;
assert(blklist != 0);
}

/* update the nchars and nlines counts */
next = seslock(blklist, ElvTrue, SES_BLKLIST);
assert(next == blklist);
blk = sesblk(blklist);
blk->blklist.blk[lblkno].nchars += chgchars;
assert(blk->blklist.blk[lblkno].nchars != 0
&& blk->blklist.blk[lblkno].nchars < SES_MAXCHARS);
blk->blklist.blk[lblkno].nlines += chglines;
assert(blk->blklist.blk[lblkno].nlines < SES_MAXCHARS);
assert(blk->blklist.blk[lblkno].blkno == blkno);
sesunlock(blklist, ElvTrue);
}

/* unlock the chars block for writing */
sesunlock(blkno, ElvTrue);
}

/******************************************************************************/
/* session restarting function */

#ifdef FEATURE_MISC
/* This function helps lowinit(), by initializing a single buffer from the
* session file.
*/
static void helpinit(bufinfo, bufproc)
_BLKNO_ bufinfo; /* a BUFINFO block */
void (*bufproc)P_((_BLKNO_ bufinfo, long nchars, long nlines, long changes, long prevloc, CHAR *name));
{
BLKNO blklist, next;
BLK *binfo, *blist;
long nchars = 0, nlines = 0;
int i;

/* mark the bufinfo block as being "allocated", and lock it in memory */
next = sesalloc(bufinfo, SES_BUFINFO);
assert(next == bufinfo);
(void)seslock(bufinfo, ElvFalse, SES_BUFINFO);
binfo = sesblk(bufinfo);

/* if it is damaged, skip it */
if (checksum(binfo) != binfo->bufinfo.checksum)
{
fprintf(stderr, "found a bad version of \"%s\"\n", binfo->bufinfo.name);
sesunlock(bufinfo, ElvFalse);
return;
}

/* for each blklist block... */
for (blklist = binfo->bufinfo.first; blklist; blklist = next)
{
/* mark the blklist block as being "allocated", & lock it */
(void)seslock(sesalloc(blklist, SES_BLKLIST), ElvFalse, SES_BLKLIST);
blist = sesblk(blklist);

/* For each chars block mentioned in the BLKLIST... */
for (i = 0; (unsigned)i < SES_MAXBLKLIST && blist->blklist.blk[i].blkno; i++)
{
assert(blist->blklist.blk[i].nchars < SES_MAXCHARS);
assert(blist->blklist.blk[i].nlines <= blist->blklist.blk[i].nchars);

/* mark the CHARS block as being "allocated" */
next = sesalloc(blist->blklist.blk[i].blkno, SES_CHARS);
assert(next == blist->blklist.blk[i].blkno);

/* count lines & chars in block */
nchars += blist->blklist.blk[i].nchars;
nlines += blist->blklist.blk[i].nlines;
}

/* find the next blklist, and then unlock this one */
next = blist->blklist.next;
sesunlock(blklist, ElvFalse);
}

/* let the BUFFER module initialize itself */
(*bufproc)(bufinfo, nchars, nlines, binfo->bufinfo.changes, binfo->bufinfo.prevloc, toCHAR(binfo->bufinfo.name));

/* unlock the bufinfo block */
sesunlock(bufinfo, ElvFalse);
}
#endif /* FEATURE_MISC */


/* This function uses sesopen() to open or create a session file. Then it
* looks for any existing buffers, and marks their blocks as being "allocated".
* It also calls a function (supplied as an argument) so that the BUFFER module
* can also do its own bookkeeping for the found buffer.
*/
void lowinit(bufproc)
void (*bufproc) P_((_BLKNO_ bufinfo, long nchars, long nlines, long changes, long prevloc, CHAR *name));
{
#ifdef FEATURE_MISC
BLK *blk;
BLKNO blkno, next;
int i;
#endif

/* create or open the session file */
sesopen(o_recovering);

#ifdef FEATURE_MISC
/* lock the superblock */
(void)seslock(0, ElvFalse, SES_SUPER);
blk = sesblk(0);

/* for each buffer mentioned in the superblock... */
for (i = 0; (unsigned)i < SES_MAXSUPER; i++)
{
/* ... skipping empty slots... */
if (blk->super.buf[i])
{
/* process the buffer */
helpinit(blk->super.buf[i], bufproc);
}
}

/* continue on to SUPER2 blocks, if any. Be sure to mark the SUPER2's
* as being "allocated".
*/
blkno = blk->super.next;
sesunlock(0, ElvFalse);
while (blkno)
{
/* mark the block as allocated, and lock it into memory */
(void)seslock(sesalloc(blkno, SES_SUPER2), ElvFalse, SES_SUPER2);

/* for each buffer mentioned in the superblock... */
for (i = 0; (unsigned)i < SES_MAXSUPER2; i++)
{
/* ... skipping empty slots... */
if (blk->super2.buf[i])
{
/* process the buffer */
helpinit(blk->super2.buf[i], bufproc);
}
}

/* find the next block */
next = blk->super2.next;
sesunlock(blkno, ElvFalse);
blkno = next;
}
#endif /* FEATURE_MISC */
}


/******************************************************************************/
/* buffer creation/destruction functions. */

/* Create a new buffer in the session file */
BLKNO lowalloc(name)
char *name; /* name of the buffer to create */
{
BLKNO bufinfo;
BLKNO super;
BLKNO next;
BLK *blk;
int i;

safeinspect();

/* Allocate a block, and lock it for writing */
bufinfo = seslock(sesalloc(0, SES_BUFINFO), ElvTrue, SES_BUFINFO);

/* Fill in the block's info */
blk = sesblk(bufinfo);
blk->bufinfo.changes = 0L;
blk->bufinfo.prevloc = 0L;
blk->bufinfo.reserved = 0;
blk->bufinfo.first = 0;
strncpy(blk->bufinfo.name, name, (size_t)SES_MAXBUFINFO);
blk->bufinfo.checksum = checksum(blk);

/* Unlock the block */
sesunlock(bufinfo, ElvTrue);

/* Lock the superblock for writing */
super = seslock(0, ElvTrue, SES_SUPER);
assert(super == 0);
blk = sesblk(super);

/* Find an empty slot in the bufs list, and put this buffer there */
i = -1;
do
{
/* if we reached the end of this block, start next */
if ((unsigned)++i >= (super==0 ? SES_MAXSUPER : SES_MAXSUPER2))
{
sesunlock(super, ElvFalse);
next = (super==0 ? blk->super.next : blk->super2.next);
if (next == 0)
{
/* need to allocate a new super2 */
next = seslock(super, ElvTrue, SES_SUPER);
assert(next == super);
next = sesalloc(0, SES_SUPER2);
if (super == 0)
{
blk->super.buf[i] = next;
}
else
{
blk->super2.buf[i] = next;
}
sesunlock(super, ElvTrue);
}
super = seslock(next, ElvTrue, SES_SUPER2);
assert(super == next);
blk = sesblk(super);
i = 0;
}
} while (((super==0) ? blk->super.buf[i] : blk->super2.buf[i]) != 0);
if (super == 0)
{
blk->super.buf[i] = bufinfo;
}
else
{
blk->super2.buf[i] = bufinfo;
}

/* Unlock the superblock (or its super2 block) */
sesunlock(super, ElvTrue);
safeinspect();
return bufinfo;
}

/* Create a copy of an existing buffer in the session file. This is used
* for creating "undo" versions of a buffer before changing it.
*/
BLKNO lowdup(originfo)
_BLKNO_ originfo; /* BUFINFO block of original lowbuf */
{
BLKNO dupinfo, dupblklist, prevdup = 0;
BLKNO scan, next;
BLK *blk, *dupblk = NULL, *dupbiblk;
int i;

#if LINECACHE
clobbercache(originfo);
#endif

/* Lock the originfo block */
(void)seslock(originfo, ElvFalse, SES_BUFINFO);
blk = sesblk(originfo);

/* Create a buffer */
dupinfo = lowalloc(blk->bufinfo.name);

/* Lock its bufinfo block for writing */
scan = seslock(dupinfo, ElvTrue, SES_BUFINFO);
assert(scan == dupinfo);

/* Copy the original bufinfo into the new bufinfo */
dupbiblk = sesblk(dupinfo);
memcpy(dupbiblk, blk, (size_t)o_blksize);

/* Unlock the original bufinfo block */
sesunlock(originfo, ElvFalse);

/* For each blklist block... */
scan = blk->bufinfo.first;
while (scan)
{
/* allocate a new blklist block, for the new buffer */
dupblklist = sesalloc(0, SES_BLKLIST);

/* link the new blklist block into the new buffer's list */
if (prevdup != 0)
{
dupblk->blklist.next = dupblklist;
sesunlock(prevdup, ElvTrue);
}
else
{
dupbiblk->bufinfo.first = dupblklist;
}

/* Lock the blklist blocks */
(void)seslock(scan, ElvFalse, SES_BLKLIST);
blk = sesblk(scan);
next = seslock(dupblklist, ElvTrue, SES_BLKLIST);
assert(next == dupblklist);
dupblk = sesblk(dupblklist);
prevdup = dupblklist;

/* copy the contents from one blklist to the other */
memcpy(dupblk, blk, (size_t)o_blksize);

/* For each chars block... */
for (i = 0; (unsigned)i < SES_MAXBLKLIST && blk->blklist.blk[i].blkno; i++)
{
/* Increment allocation count on the chars block */
(void)sesalloc(blk->blklist.blk[i].blkno, SES_CHARS);
}
assert((unsigned)i == SES_MAXBLKLIST || !blk->blklist.next);

/* unlock the blklist blocks, and procede to next blklist */
next = blk->blklist.next;
sesunlock(scan, ElvFalse);
scan = next;
}

/* unlock the final new blklist block (if any) */
if (dupblk)
{
sesunlock(prevdup, ElvTrue);
}

/* Unlock the new bufinfo block for writing */
dupbiblk->bufinfo.checksum = checksum(dupbiblk);
sesunlock(dupinfo, ElvTrue);
return dupinfo;
}

/* This function deletes a buffer from the session file. */
void lowfree(bufinfo)
_BLKNO_ bufinfo; /* BUFINFO block of lowbuf to destroy */
{
BLKNO scan, next;
BLK *blk;
int i;

#if LINECACHE
clobbercache(bufinfo);
#endif
/* Lock the superblock for writing */
scan = seslock(0, ElvTrue, SES_SUPER);
assert(scan == 0);
blk = sesblk(0);

/* Find this buffer in the bufs list, and replace it with 0 */
i = -1;
do
{
/* if we reached the end of this block, start next */
if ((unsigned)++i >= (scan==0 ? SES_MAXSUPER : SES_MAXSUPER2))
{
next = (scan==0 ? blk->super.next : blk->super2.next);
sesunlock(scan, ElvFalse);
assert(next != 0);
scan = seslock(next, ElvTrue, SES_BLKLIST);
assert(scan == next);
blk = sesblk(scan);
i = 0;
}
} while ((unsigned)((scan==0) ? blk->super.buf[i] : blk->super2.buf[i]) != bufinfo);
if (scan == 0)
{
blk->super.buf[i] = 0;
}
else
{
blk->super2.buf[i] = 0;
}

/* Unlock the superblock for writing, and then flush it to disk.
* Flushing it is important because we're about to free the blocks
* from this buffer, and those blocks are likely to be reallocated
* right away for some other purpose. If elvis crashed at that time
* and the super block had never been flushed, then the session file
* might be too scrambled for elvis to read it successfully.
*/
sesunlock(scan, ElvTrue);
sesflush(scan);

/* Lock the bufinfo block */
(void)seslock(bufinfo, ElvFalse, SES_BUFINFO);

/* For each blklist block... */
for (scan = sesblk(bufinfo)->bufinfo.first; scan; scan = next)
{
/* Lock the blklist block */
(void)seslock(scan, ElvFalse, SES_BLKLIST);

/* For each chars block... */
blk = sesblk(scan);
for (i = 0; (unsigned)i < SES_MAXBLKLIST && blk->blklist.blk[i].blkno; i++)
{
/* free the chars block */
sesfree(blk->blklist.blk[i].blkno);
}
assert((unsigned)i == SES_MAXBLKLIST || !blk->blklist.next);

/* Unlock the blklist block */
next = blk->blklist.next;
sesunlock(scan, ElvFalse);

/* Free the blklist block */
sesfree(scan);
}

/* Unlock the bufinfo block */
sesunlock(bufinfo, ElvFalse);

/* Free the bufinfo block */
sesfree(bufinfo);
}

/* Change the title of a buffer */
void lowtitle(bufinfo, title)
_BLKNO_ bufinfo; /* bufinfo block whose title is to be changed */
CHAR *title; /* the new title */
{
BLK *blk;
#ifdef DEBUG_SESSION
BLKNO blkno;

blkno = seslock(bufinfo, ElvTrue, SES_BUFINFO);
assert(blkno == bufinfo);
#else
(void)seslock(bufinfo, ElvTrue, SES_BUFINFO);
#endif

blk = sesblk(bufinfo);
assert(blk);
CHARncpy(blk->bufinfo.name, title, (size_t)SES_MAXBUFINFO);
sesunlock(bufinfo, ElvTrue);
}

/******************************************************************************/

#if LINECACHE
static struct
{
BLKNO bufinfo;/* bufinfo of a known line, or 0 for none */
long lineno; /* line number */
long offset; /* offset of the start of the line */
} linecache[LINECACHE];
static int lineidx; /* index into linecache[] of slot to recycle */
#endif /* LINECACHE */


#if LINECACHE
static void clobbercache(dst)
_BLKNO_ dst; /* bufinfo of a changed buffer */
{
register int i;

for (i = 0; i < LINECACHE; i++)
#if 0
if (linecache[i].bufinfo == dst)
#endif
linecache[i].bufinfo = 0;
}
#endif /* LINECACHE */

/* convert a line number to an offset, for a given buffer */
long lowline(bufinfo, lineno)
_BLKNO_ bufinfo; /* BUFINFO of the buffer */
long lineno; /* line number (starting with 1) */
{
BLK *blk; /* contents of a bufinfo block or blklist block */
BLKNO blklist;/* used for stepping from one blklist to next */
BLKNO next; /* the next blklist block, after this one */
long offset; /* total offset seen */
int i; /* used for scanning through blklist.blk[] */
int nlines; /* number of lines/chars in block */
#if LINECACHE
long origline;/* a copy of lineno */

/* check the cache first */
for (i = 0; i < LINECACHE; i++)
{
if (linecache[i].bufinfo == bufinfo && linecache[i].lineno == lineno)
{
return linecache[i].offset;
}
}
origline = lineno;
#endif /* LINECACHE */

/* outside this function, line numbers start with 1, but in here they start at 0 */
lineno--;

/* find the first blklist */
(void)seslock(bufinfo, ElvFalse, SES_BUFINFO);
blklist = sesblk(bufinfo)->bufinfo.first;
sesunlock(bufinfo, ElvFalse);

/* if empty buffer then return 0 */
if (!blklist)
{
return 0;
}

/* for each blklist... */
for (offset = 0; ; blklist = next)
{
assert(blklist != 0);

/* for each element of blklist->blk[]... */
seslock(blklist, ElvFalse, SES_BLKLIST);
blk = sesblk(blklist);
for (i = 0; (unsigned)i < SES_MAXBLKLIST && blk->blklist.blk[i].blkno; i++)
{
/* see if we've found the right chars block yet */
if ((nlines = blk->blklist.blk[i].nlines) >= lineno)
{
/* unlock the blklist, and lock the chars block */
next = blk->blklist.blk[i].blkno;
i = blk->blklist.blk[i].nchars;
sesunlock(blklist, ElvFalse);
(void)seslock(next, ElvFalse, SES_CHARS);
blk = sesblk(next);

/* AT THIS POINT...
* lineno = number of newlines to move past
* in this CHARS block.
* nlines = total number of newlines in this
* CHARS block
* i = total chars in this CHARS block
* offset = offset of start of this block
*/

/* locate the line within the chars block */
if (lineno + lineno <= nlines)
{
/* count newlines from front of block */
for (i = 0; lineno > 0; offset++, i++)
{
assert((unsigned)i < SES_MAXCHARS);
if (blk->chars.chars[i] == '\n')
{
lineno--;
}
}
}
else
{
/* count newlines from rear of block */
for (offset += i, lineno -= nlines; ; )
{
assert(i > 0);
if (blk->chars.chars[--i]=='\n')
{
if (lineno++ == 0)
break;
}
offset--;
}
}

#if LINECACHE
/* stuff information into the cache */
linecache[lineidx].bufinfo = bufinfo;
linecache[lineidx].offset = offset;
linecache[lineidx].lineno = origline;
lineidx = (lineidx + 1) % LINECACHE;
#endif /* LINECACHE */

/* return the offset */
sesunlock(next, ElvFalse);
return offset;
}
lineno -= blk->blklist.blk[i].nlines;
offset += blk->blklist.blk[i].nchars;
}

/* find the next blklist */
next = blk->blklist.next;
assert(!next || (unsigned)i == SES_MAXBLKLIST);
sesunlock(blklist, ElvFalse);
if (!next)
{
/* there is no next blklist block -- return final offset */
return offset;
}
}
/*NOTREACHED*/
}

/******************************************************************************/

/* Convert a byte offset into a BLKNO. This function scans a buffer's
* blklist blocks, and uses the character counts there to determine
* which block contains the character for a given offset.
*
* Optionally, it can also determine how many characters are to the left
* or right of the offset, in that block. If "left" and "right" aren't NULL,
* the variables they point to will be set. (The character at the offset
* is included * in the "right" count.) It can similarly set a variable
* indicating the logical block number of the block containing the offset.
*
* There are three special cases:
* * If a negative offset is given, it is treated as 0.
* * If an offset past the end of the buffer is given, it is treated as
* being a byte in the last block, after the last byte in that block;
* this is *usually* where the next byte would be appended; the "right"
* value is then set to 0 (under all other conditions, it would be at
* least 1).
* * If the buffer has no blocks, then all variables and the return
* value will be 0.
*/
BLKNO lowoffset(bufinfo, offset, left, right, lptr, linenum)
_BLKNO_ bufinfo; /* BUFINFO of the lowbuf */
long offset; /* offset into the buffer */
COUNT *left; /* output: number of preceding bytes in CHARS block */
COUNT *right; /* output: number of following bytes in CHARS block */
LBLKNO *lptr; /* output: logical block number of CHARS block */
long *linenum;/* output: line number */
{
BLKNO blklist;/* used for stepping from one blklist to next */
BLKNO next; /* the next blklist block, after this one */
LBLKNO lblkno; /* counts overall LBLKNO of the given offset */
long lnum; /* counts newlines */
BLK *blk; /* contents of a bufinfo or blklist block */
register int i; /* used for scanning through blklist.blk[] */
int nlines; /* lines in current CHARS block */
int nchars; /* chars in current CHARS block */
register struct blki_s *blki;
BLKNO maxblklist = SES_MAXBLKLIST;

/* treat negative offsets as 0 */
if (offset < 0)
{
offset = 0;
}

/* find the first blklist */
(void)seslock(bufinfo, ElvFalse, SES_BUFINFO);
blklist = sesblk(bufinfo)->bufinfo.first;
sesunlock(bufinfo, ElvFalse);

/* if the buffer has no blocks, then any offset is past the end of
* the buffer, so do the "*right = 0" thing.
*/
if (!blklist)
{
if (left) *left = 0;
if (right) *right = 0;
if (lptr) *lptr = 0;
if (linenum) *linenum = 0;
return 0;
}

/* for each blklist... */
for (lblkno = 0, lnum = 1; ; lblkno += maxblklist, blklist = next)
{
assert(blklist != 0);

/* for each element of blklist->blk[]... */
seslock(blklist, ElvFalse, SES_BLKLIST);
blk = sesblk(blklist);
for (i = 0, blki = blk->blklist.blk;
i < maxblklist && blki->blkno;
lnum += blki->nlines, i++, blki++)
{
/* see if we've found it yet */
offset -= blki->nchars;
if (offset < 0L)
{
/* Yes! Return the info */
next = blki->blkno;
nlines = blki->nlines;
nchars = blki->nchars;
sesunlock(blklist, ElvFalse);
if (lptr) *lptr = lblkno + i;
i = offset + nchars;
if (left) *left = i;
if (right) *right = (unsigned short)-offset;
if (linenum)
{
/* AT THIS POINT...
* lnum = line# of front of block
* i = index into block
* nlines = total \n's in CHARS block
* nchars = total chars in CHARS block
* next = BLKNO of the CHARS block
*/
if (i + i <= nchars)
{
/* count from front of block */
seslock(next, ElvFalse, SES_CHARS);
blk = sesblk(next);
while (--i >= 0)
{
if (blk->chars.chars[i] == '\n')
{
lnum++;
}
}
sesunlock(next, ElvFalse);
}
else
{
/* count from rear of block */
lnum += nlines;
seslock(next, ElvFalse, SES_CHARS);
blk = sesblk(next);
do
{
if (blk->chars.chars[--nchars] == '\n')
{
lnum--;
}
} while (i < nchars);
sesunlock(next, ElvFalse);
}
*linenum = lnum;
}
return next;
}
}

/* find the next blklist */
next = blk->blklist.next;
assert(!next || i == maxblklist);
if (!next)
{
/* there is no next blklist block -- do the "*right = 0" * thing. */
if (left) *left = blk->blklist.blk[i - 1].nchars;
if (right) *right = 0;
if (lptr) *lptr = lblkno + i - 1;
if (linenum) *linenum = lnum;
next = blk->blklist.blk[i - 1].blkno;
sesunlock(blklist, ElvFalse);
return next;
}
sesunlock(blklist, ElvFalse);
}
/*NOTREACHED*/
}




/* This function inserts a string into a buffer. It returns the change in
* the number of lines in the buffer (i.e., the number of newline characters
* in the "new" string.
*/
long lowinsert(dst, dsttop, newp, newlen)
_BLKNO_ dst; /* BUFINFO of lowbuf */
long dsttop; /* offset where insertion should begin */
register CHAR *newp; /* new text to be inserted */
long newlen; /* length of new text */
{
BLKNO blkno;
COUNT left;
COUNT right;
LBLKNO lblkno;
BLK *biblk;
BLK *cblk;
int nlines;
register BLKNO newblkno; /* a new block */
BLKNO blklist;
BLK *newblk;
long totlines = 0;
register int i;
int j;

safeinspect();

#if LINECACHE
clobbercache(dst);
#endif

/* figure out where insertion should begin */
blkno = lowoffset(dst, dsttop, &left, &right, &lblkno, (long *)0);

/* will the new text fit in the current block? */
if (blkno != 0 && (unsigned)(left + right + newlen) < SES_MAXCHARS)
{
/* yes! Do a single-block rewrite. */

/* lock the chars block for writing (trickier than it sounds!) */
blkno = lockchars(dst, lblkno, blkno);

/* twiddle the contents of that block */
cblk = sesblk(blkno);
for (i = left + right + newlen - 1; i >= left + newlen; i--)
{
cblk->chars.chars[i] = cblk->chars.chars[i - newlen];
}
nlines = 0;
for (i = 0; i < newlen; i++)
{
cblk->chars.chars[i + left] = newp[i];
if (newp[i] == '\n') nlines++;
}

/* unlock that block, and update its nchars and nlines */
unlockchars(dst, lblkno, blkno, (int)newlen, nlines);
totlines = (long)nlines;
}
else
{
/* if we're splitting an existing block... */
if (blkno != 0 && left != 0 && right != 0)
{
/* allocate a new block */
newblkno = seslock(sesalloc(0, SES_CHARS), ElvTrue, SES_CHARS);
newblk = sesblk(newblkno);

/* copy the second half of the characters into it */
blkno = lockchars(dst, lblkno, blkno);
cblk = sesblk(blkno);
nlines = 0;
for (i = 0, j = left; j < left + right; i++, j++)
{
newblk->chars.chars[i] = cblk->chars.chars[j];
if (newblk->chars.chars[i] == '\n')
{
nlines++;
}
}
sesunlock(newblkno, ElvTrue);

/* insert the new block after the first */
seslock(dst, ElvTrue, SES_BUFINFO);
biblk = sesblk(dst);
blklist = insblock(biblk->bufinfo.first, (LBLKNO)(lblkno + 1), newblkno, (COUNT)i, (COUNT)nlines);
biblk->bufinfo.first = blklist;
biblk->bufinfo.changes++;
biblk->bufinfo.prevloc = dsttop;
biblk->bufinfo.checksum = checksum(biblk);
sesunlock(dst, ElvTrue);

/* copy some new text into first half, filling it 90% */
nlines = -nlines;
for (i = left, j = -right;
i < o_blkfill && newlen > 0;
i++, j++, newlen--)
{
cblk->chars.chars[i] = *newp;
if (*newp++ == '\n')
{
nlines++;
totlines++;
}
}
unlockchars(dst, lblkno, blkno, j, nlines);
}

/* tweak the value of lblkno, if necessary, so we always insert
* before lblkno (never after)
*/
if (left > 0)
{
lblkno++;
}

/* while we have more text to insert */
seslock(dst, ElvTrue, SES_BUFINFO);
biblk = sesblk(dst);
blklist = biblk->bufinfo.first;
while (newlen > 0)
{
/* allocate a new block */
newblkno = seslock(sesalloc(0, SES_CHARS), ElvTrue, SES_CHARS);
newblk = sesblk(newblkno);

/* copy text into it */
nlines = 0;
for (i = 0; i < o_blkfill && newlen > 0; i++, newlen--)
{
newblk->chars.chars[i] = *newp;
if (*newp++ == '\n')
{
nlines++;
}
}
totlines += (long)nlines;
sesunlock(newblkno, ElvTrue);

/* insert the new block */
blklist = insblock(blklist, lblkno, newblkno, (COUNT)i, nlines);
lblkno++;
}
biblk->bufinfo.changes++;
biblk->bufinfo.first = blklist;
biblk->bufinfo.checksum = checksum(biblk);
sesunlock(dst, ElvTrue);
}

safeinspect();

return totlines;
}

/* This function deletes characters located between two points. It returns
* the change in the number of lines (i.e., the negative of the quantity of
* newlines deleted).
* dst: the bufinfo block
* dsttop: offset to start of region to delete
* dstbottom: offsert to end of region to delete
*/
long lowdelete(dst, dsttop, dstbottom)
_BLKNO_ dst; /* BUFINFO of lowbuf */
long dsttop; /* offset where deletion should begin */
long dstbottom; /* offset where deletion should end */
{
BLK *blk;
COUNT nlines; /* change in line count for a single block */
long totlines = 0; /* total change in line count */
BLKNO first;
LBLKNO firstlblk; /* block containing dsttop */
COUNT firstleft; /* chars in firstlblk to left of dsttop */
COUNT firstright; /* chars in firstlblk to right of dsttop */
BLKNO last;
LBLKNO lastlblk; /* block containing dstbottom */
COUNT lastleft; /* chars in firstlblk to left of dstbottom */
COUNT lastright; /* chars in firstlblk to right of dstbottom */
LBLKNO lblkno;
BLK *biblk;
int i, j;

safeinspect();

#if LINECACHE
clobbercache(dst);
#endif

/* lock the bufinfo block, and fetch it */
(void)seslock(dst, ElvTrue, SES_BUFINFO);
biblk = sesblk(dst);

/* If both ends are in the same block */
first = lowoffset(dst, dsttop, &firstleft, &firstright, &firstlblk, (long *)0);
last = lowoffset(dst, dstbottom, &lastleft, &lastright, &lastlblk, (long *)0);

if (first == last || (firstlblk + 1 == lastlblk && lastleft == 0))
{
safeinspect();

/* tweak the special case where lastleft==0 */
if (first != last)
{
lastleft = firstleft + firstright;
lastright = 0;
}

/* deleting one whole block? */
if (firstleft == 0 && lastleft == firstright)
{
/* yes, delete the whole block */
biblk->bufinfo.first = delblock(biblk->bufinfo.first, firstlblk, (LBLKNO *)0, &nlines);
safeinspect();
}
else
{
/* delete part of block by modifying CHARS block */

/* Lock the chars block for writing; update blklist block */
first = lockchars(dst, firstlblk, first);
safeinspect();

/* count the doomed lines */
nlines = 0;
blk = sesblk(first);
for (i = firstleft; i < lastleft; i++)
{
if (blk->chars.chars[i] == '\n')
{
nlines++;
}
}

/* Delete the chars from chars block */
for (i = firstleft, j = lastleft; j < lastleft + lastright; i++, j++)
{
blk->chars.chars[i] = blk->chars.chars[j];
}
safeinspect();

/* Unlock the chars block, updating chars & lines counts */
unlockchars(dst, firstlblk, first, firstleft - lastleft, -(int)nlines);
safeinspect();
}
totlines = -(long)nlines;
}
else
{
safeinspect();

/* Delete any whole blocks from the middle portion of the doomed text. */
lastlblk++;
for (lblkno = (firstleft == 0 ? firstlblk : firstlblk + 1);
lblkno + 1 < (lastright == 0 ? lastlblk + 1 : lastlblk);
lastlblk--)
{
biblk->bufinfo.first = delblock(biblk->bufinfo.first, lblkno, (LBLKNO *)0, &nlines);
totlines -= (long)nlines;
}
lastlblk--;
safeinspect();

/* If there is a first block */
if (firstleft > 0 && firstright > 0)
{
/* Lock the chars block for writing; update blklist block */
first = lockchars(dst, firstlblk, first);

/* count the doomed lines, and zero the doomed characters */
nlines = 0;
blk = sesblk(first);
for (i = firstleft; i < firstleft + firstright; i++)
{
if (blk->chars.chars[i] == '\n')
{
nlines++;
}
blk->chars.chars[i] = '\0';
}

/* Unlock the chars block, updating chars & lines counts */
unlockchars(dst, firstlblk, first, -firstright, -nlines);
totlines -= (long)nlines;
safeinspect();
}

/* If there is a last block */
if (lastleft > 0 && lastright > 0)
{
/* Lock the chars block for writing; update blklist block */
last = lockchars(dst, lastlblk, last);

/* count the doomed lines */
nlines = 0;
blk = sesblk(last);
for (i = 0; i < lastleft; i++)
{
if (blk->chars.chars[i] == '\n')
{
nlines++;
}
}

/* Delete old text from start of block */
for (i = 0, j = lastleft; j < lastleft + lastright; i++, j++)
{
blk->chars.chars[i] = blk->chars.chars[j];
}
while (i < lastleft + lastright)
{
blk->chars.chars[i++] = '\0';
}

/* Unlock the chars block, updating chars & lines counts */
unlockchars(dst, lastlblk, last, -lastleft, -nlines);
totlines -= (long)nlines;
safeinspect();
}
}

/* Update the bufinfo block's checksum */
biblk->bufinfo.changes++;
biblk->bufinfo.prevloc = dsttop;
biblk->bufinfo.checksum = checksum(biblk);

/* Unlock the bufinfo block for writing */
sesunlock(dst, ElvTrue);
safeinspect();
return totlines;
}

/* Replace one chunk of text with another, and return the change in the
* number of lines.
*/
long lowreplace(dst, dsttop, dstbottom, newp, newlen)
_BLKNO_ dst; /* BUFINFO of the lowbuf */
long dsttop; /* offset where replacement begins */
long dstbottom; /* offset of end of old text */
CHAR *newp; /* new text */
long newlen; /* length of new text */
{
long totlines = 0; /* total change in line count */

totlines += lowdelete(dst, dsttop, dstbottom);
totlines += lowinsert(dst, dsttop, newp, newlen);
return totlines;
}

/* Insert part of one buffer into another, and return the change in the number
* of lines.
*/
long lowpaste(dst, dsttop, src, srctop, srcbottom)
_BLKNO_ dst; /* BUFINFO of destination lowbuf */
long dsttop; /* offset where text should be copied to */
_BLKNO_ src; /* BUFINFO of source lowbuf */
long srctop; /* offset of start of source text */
long srcbottom; /* offset of end of source text */
{
COUNT left, right;
BLKNO blkno;
BLK *blk;
BLK *tmpblk = NULL;
long totlines = 0;

safeinspect();

/* destination can't be in the middle of the source */
assert(src != dst || dsttop <= srctop || dsttop >= srcbottom);

#if LINECACHE
clobbercache(dst);
#endif

/* Small problem: If the destination is in the same buffer as the
* source, and happens to be located before the source in the same
* block, then when inserting the new text we'll be altering the block
* cache which messes up our pointers.
*
* Solution: If source & dest are in the same buffer, and dest comes
* before source, then we need to use a private copy of each source
* block.
*/
if (dst == src && dsttop <= srctop)
{
tmpblk = (BLK *)safealloc((int)o_blksize, 1);
}

/* we'll do this in chunks -- transfering text from each block of the
* source into the destination, until all text has been transferred.
*/
while (srctop < srcbottom)
{
/* read the text block, and find the start of source text in it */
blkno = lowoffset(src, srctop, &left, &right, (LBLKNO *)0, (long *)0);

seslock(blkno, ElvFalse, SES_CHARS);
blk = sesblk(blkno);
if (tmpblk)
{
memcpy(tmpblk, blk, (size_t)o_blksize);
sesunlock(blkno, ElvFalse);
blk = tmpblk;
}

/* Usually we'll be transferring all text from here to the end
* of the block. If this is the last block, we may be
* transferring less.
*/
if (right > srcbottom - srctop)
{
right = (unsigned short)(srcbottom - srctop);
}

/* Copy the chunk of text into the destination. */
totlines += lowinsert(dst, dsttop, &blk->chars.chars[left], (long)right);
srctop += right;
dsttop += right;

/* if we inserted text before the source, then we must tweak the
* source offsets.
*/
if (tmpblk)
{
srctop += right; /* again */
srcbottom += right;
}
else /* different buffers -- the blk was used without copying */
{
sesunlock(blkno, ElvFalse);
}
}

/* free the temporary block copy, if we used one */
if (tmpblk)
{
safefree(tmpblk);
}

safeinspect();

return totlines;
}
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