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/* scan.c */
/* Copyright 1995 by Steve Kirkendall */
char id_scan[] = "$Id: scan.c,v 2.14 1996/08/28 23:45:16 steve Exp $";
#include "elvis.h"
/* This variable points to the top of the stack of scan contexts */
struct scan_s *scan__top;
/* This variable points to the head of a list of freed scan contexts.
* The scanalloc() function checks this variable, and recycles the first
* scan context instead of allocating a new one, to reduce the number of
* calls to safealloc().
*/
static struct scan_s *recycle;
/* This variable is used by the scanmark() macro */
MARKBUF scan__markbuf;
/* This function creates a new scan context, and starts the scanning at
* a given mark. The scan context must be freed by a later scanfree()
* call. The cp argument is used to distinguish one scan context from
* another, and the (CHAR *) that it points to will be set to point to the
* appropriate CHAR in the buffer. The value of that pointer is returned.
* If the seek is past either end of the buffer, *cp is set to NULL.
*/
#ifndef DEBUG_ALLOC
CHAR *scanalloc(cp, start)
#else
CHAR *_scanalloc(file, line, cp, start)
char *file; /* name of file where allocating */
int line; /* line number where allocating */
#endif
CHAR **cp; /* address of pointer which will be used for scanning */
MARK start; /* where the scanning should begin */
{
struct scan_s *newp;
assert(start != NULL && cp != NULL);
/* allocate a new scan context */
#ifndef DEBUG_ALLOC
if (recycle)
{
newp = recycle;
recycle = recycle->next;
memset((char *)newp, 0, sizeof(*newp));
}
else
{
newp = (struct scan_s *)safealloc(1, sizeof *newp);
}
#else
newp = (struct scan_s *)_safealloc(file, line, False, 1, sizeof *newp);
#endif
newp->next = scan__top;
scan__top = newp;
/* initialize it */
newp->ptr = cp;
#ifdef DEBUG_ALLOC
# ifdef DEBUG_SCAN
newp->file = file;
newp->line = line;
# endif
#endif
return scanseek(cp, start);
}
/* This function creates a new scan context for scanning a string. This makes
* it possible to write functions which can scan a string or the contents of a
* buffer with equal ease.
*/
CHAR *scanstring(cp, str)
CHAR **cp; /* address of pointer which will be used for scanning */
CHAR *str; /* NUL-terminated string to scan */
{
struct scan_s *newp;
assert(str != NULL && cp != NULL);
/* allocate a new scan context */
if (recycle)
{
newp = recycle;
recycle = recycle->next;
memset((char *)newp, 0, sizeof(*newp));
}
else
{
newp = (struct scan_s *)safealloc(1, sizeof *newp);
}
newp->next = scan__top;
scan__top = newp;
/* initialize it */
newp->buffer = (BUFFER)0;
newp->bufinfo = (BLKNO)0;
newp->blkno = (BLKNO)0;
newp->leftedge = str;
newp->rightedge = str + CHARlen(str);
newp->ptr = cp;
newp->leoffset = 0;
/* initialize *cp to point to the start of the string */
*cp = str;
return *cp;
}
/* This function allocates a new scan context that is identical to an
* existing scan context. I.e., it is like scanalloc(&new, scanmark(&old))
* However, this function is usually much faster.
*/
CHAR *scandup(cp, oldp)
CHAR **cp; /* address of pointer to use in new scan context */
CHAR **oldp; /* address of pointer used in existing scan context */
{
struct scan_s *newp;
assert(scan__top && scan__top->ptr == oldp);
/* allocate a new scan context */
if (recycle)
{
newp = recycle;
recycle = recycle->next;
memset((char *)newp, 0, sizeof(*newp));
}
else
{
newp = (struct scan_s *)safealloc(1, sizeof *newp);
}
newp->next = scan__top;
scan__top = newp;
/* initialize it to match the old scan context */
newp->buffer = newp->next->buffer;
newp->bufinfo = newp->next->bufinfo;
newp->blkno = newp->next->blkno;
newp->leftedge = newp->next->leftedge;
newp->rightedge = newp->next->rightedge;
newp->ptr = cp;
newp->leoffset = newp->next->leoffset;
/* initialize *cp to point to the correct character */
*cp = *oldp;
/* lock the block that *cp points to. */
if (newp->blkno)
{
seslock(newp->blkno, False, SES_CHARS);
}
return *cp;
}
/* This function frees a scan context which was created by scanalloc() */
void scanfree(cp)
CHAR **cp; /* address of pointer used for scanning */
{
struct scan_s *context;
assert(cp != NULL);
assert(scan__top != NULL);
assert(scan__top->ptr == cp);
/* delete it from the list */
context = scan__top;
scan__top = scan__top->next;
/* free its resources */
if (context->blkno)
{
sesunlock(context->blkno, False);
}
#ifndef DEBUG_ALLOC
context->next = recycle;
recycle = context;
#else
safefree(context);
#endif
}
/* This function uses an existing scan context created by scanalloc() or
* scanstring(), to start a new scan at a given mark. If the original scan
* context was created by scanalloc(), the mark can even refer to a totally
* different buffer than the original scan. If the original scan context
* was created by scanstring(), then the mark can only be moved within the
* original string buffer.
*/
CHAR *scanseek(cp, restart)
CHAR **cp; /* address of pointer used for scanning */
MARK restart;/* where scanning should resume */
{
COUNT left, right; /* number of chars in block */
BLKNO nextblkno;
assert(cp != NULL && restart != NULL);
assert(scan__top->ptr == cp);
/* Can't mix string scans with buffer seeks, or vice versa. Testing
* this is a bit tricky because scanalloc() calls scanseek() to fill in
* a bunch of fields, we have to allow that; hence the leftedge test.
*/
assert(!(markbuffer(restart) && !scan__top->buffer && scan__top->leftedge));
assert(!(!markbuffer(restart) && scan__top->buffer));
/* string scan or buffer scan? */
if (!markbuffer(restart))
{
/* STRING */
/* compute the new value of the pointer */
*cp = &scan__top->leftedge[markoffset(restart)];
/* if seeking to a non-existent offset, return NULL */
if (*cp < scan__top->leftedge
|| *cp >= scan__top->rightedge)
{
*cp = NULL;
return NULL;
}
}
else
{
/* BUFFER */
/* if seeking to a non-existent offset, return NULL */
if (markoffset(restart) < 0
|| markoffset(restart) >= o_bufchars(markbuffer(restart)))
{
*cp = NULL;
return NULL;
}
/* find the bufinfo block for the buffer that MARK refers to */
scan__top->buffer = markbuffer(restart);
scan__top->bufinfo = bufbufinfo(scan__top->buffer);
/* find the chars block. If this scan context happens to be
* nested inside another one and we're seeking into the same
* block, then we can optimize this a lot.
*/
if (scan__top->next
&& scan__top->next->buffer == scan__top->buffer
&& scan__top->next->leoffset <= markoffset(restart)
&& scan__top->next->leoffset +
(int)(scan__top->next->rightedge - scan__top->next->leftedge)
> markoffset(restart))
{
/* hooray! We can avoid calling lowoffset() */
nextblkno = scan__top->next->blkno;
left = (int)(markoffset(restart) - scan__top->next->leoffset);
right = (int)(scan__top->next->rightedge - scan__top->next->leftedge)
- left;
}
else
{
/* can't optimize; must call lowoffset to find block */
nextblkno = lowoffset(scan__top->bufinfo,
markoffset(restart), &left, &right, NULL, NULL);
}
assert(right > 0 && nextblkno > 0);
/* unlock the old block, and lock the new one */
if (scan__top->blkno != nextblkno)
{
if (scan__top->blkno)
{
sesunlock(scan__top->blkno, False);
}
seslock(nextblkno, False, SES_CHARS);
scan__top->blkno = nextblkno;
}
/* set the other variables */
scan__top->leftedge = sesblk(scan__top->blkno)->chars.chars;
scan__top->rightedge = scan__top->leftedge + left + right;
scan__top->leoffset = markoffset(restart) - left;
*cp = scan__top->leftedge + left;
}
return *cp;
}
#ifdef DEBUG_SCAN
/* This function is a helper function for the scanleft() macro. This function
* should not be called directly.
*
* It returns the number of buffered characters to the left of the current
* scan point.
*/
COUNT scan__left(cp)
CHAR **cp; /* address of pointer used for scanning */
{
assert(cp != NULL);
assert(scan__top->ptr == cp);
/* return the number of buffered CHARs */
return (COUNT)(*cp - scan__top->leftedge);
}
/* This function is a helper function for the scanright() macro. This function
* should not be called directly.
*
* It returns the number of buffered characters to the right of the current
* scan point.
*/
COUNT scan__right(cp)
CHAR **cp; /* address of pointer used for scanning */
{
assert(cp != NULL);
assert(scan__top->ptr == cp);
/* return the number of buffered CHARs */
return (COUNT)(scan__top->rightedge - *cp);
}
/* create a mark which refers to the current point of the scan */
MARK scanmark(cp)
CHAR **cp; /* address of pointer used for scanning */
{
assert(cp != NULL);
assert(scan__top->ptr == cp);
/* return a temporary mark at the proper position */
return marktmp(scan__markbuf, scan__top->buffer, scan__top->leoffset + (int)(*cp - scan__top->leftedge));
}
#endif /* DEBUG_SCAN */
/* This function is a helper function for the scannext() macro. This function
* should not be called directly.
*/
CHAR *scan__next(cp)
CHAR **cp; /* address of pointer used for scanning */
{
MARKBUF markbuf;
assert(cp != NULL && *cp != NULL);
assert(scan__top->ptr == cp);
/* if the next character is in the same block, its easy */
if (++*cp < scan__top->rightedge)
{
return *cp;
}
assert(*cp == scan__top->rightedge);
/* else seek to the first character of following block */
return scanseek(cp, marktmp(markbuf, scan__top->buffer,
scan__top->leoffset + (int)(scan__top->rightedge - scan__top->leftedge)));
}
/* This function is a helper function for the scanprev() macro. This function
* should not be called directly.
*/
CHAR *scan__prev(cp)
CHAR **cp; /* address of pointer used for scanning */
{
MARKBUF markbuf;
assert(cp != NULL);
assert(scan__top->ptr == cp);
/* if the previous character is in the same block, its easy */
if (--*cp >= scan__top->leftedge)
{
return *cp;
}
/* if this was the first block, we're at the end */
if (scan__top->leoffset == 0)
{
if (scan__top->blkno != 0)
{
sesunlock(scan__top->blkno, False);
scan__top->blkno = 0;
}
*cp = NULL;
return NULL;
}
/* else seek to the last character of preceding block */
return scanseek(cp, marktmp(markbuf, scan__top->buffer, scan__top->leoffset - 1));
}
/* This function returns the single character at a given location. It is
* similar to scanseek(), except that this function doesn't use a scan context,
* and it returns a CHAR instead of a pointer-to-CHAR.
*/
CHAR scanchar(mark)
MARK mark; /* buffer/offset of the character to fetch */
{
COUNT left, right; /* number of chars in block */
BLKNO bufinfo; /* block describing the buffer */
BLKNO blkno; /* block containing the character */
CHAR ch; /* the character */
/* if seeking to a non-existent offset, return '\0' */
if (markoffset(mark) < 0
|| markoffset(mark) >= o_bufchars(markbuffer(mark)))
{
return '\0';
}
/* find the bufinfo block for the buffer that MARK refers to */
bufinfo = bufbufinfo(markbuffer(mark));
/* find the chars block */
blkno = lowoffset(bufinfo, markoffset(mark), &left, &right, NULL, NULL);
assert(right != 0);
/* lock the block */
seslock(blkno, False, SES_CHARS);
/* fetch the character */
ch = sesblk(blkno)->chars.chars[left];
/* unlock the block */
sesunlock(blkno, False);
return ch;
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.