rangeset.c

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    last = rangeset->last_index;

    /* try to profit from the last lookup by using its index */
    if (last >= len || last < 0) {
	last = (len > 0) ? len - 1 : 0;	/* make sure last is in range */
	rangeset->last_index = last;
    }

    len *= 2;
    last *= 2;

    if (pos >= ranges[last]) {		/* last even: this is a start */
	if (pos < ranges[last + 1])	/* checking an end here */
	    return last / 2;		/* no need to change rangeset->last_index */
	else
	    last += 2;			/* not in this range: move on */

	if (last == len)
	    return -1;			/* moved on too far */

	/* find the entry in the upper portion of ranges */
	index = weighted_at_or_before(ranges, last, len, pos); /* search end only */
    }
    else if (last > 0) {
	index = weighted_at_or_before(ranges, 0, last, pos); /* search front only */
    }
    else
	index = 0;

    rangeset->last_index = index / 2;

    if (index == len)
	return -1;			/* beyond end */

    if (index & 1) {			/* index odd: references an end marker */
	if (pos < ranges[index])
	    return index / 2;		/* return the range index */
    }
    else {				/* index even: references start marker */
	if (pos == ranges[index])
	    return index / 2;		/* return the range index */
    }
    return -1;				/* not in any range */
}

/* -------------------------------------------------------------------------- */

/*
** Merge the ranges in rangeset plusSet into rangeset origSet.
*/

int RangesetAdd(Rangeset *origSet, Rangeset *plusSet)
{
    Range *origRanges, *plusRanges, *newRanges, *oldRanges;
    int nOrigRanges, nPlusRanges;
    int isOld;

    origRanges = origSet->ranges;
    nOrigRanges = origSet->n_ranges;

    plusRanges = plusSet->ranges;
    nPlusRanges = plusSet->n_ranges;

    if (nPlusRanges == 0)
	return nOrigRanges;	/* no ranges in plusSet - nothing to do */

    newRanges = RangesNew(nOrigRanges + nPlusRanges);

    if (nOrigRanges == 0) {
	/* no ranges in destination: just copy the ranges from the other set */
	memcpy(newRanges, plusRanges, nPlusRanges * sizeof (Range));
	RangesFree(origSet->ranges);
	origSet->ranges = newRanges;
	origSet->n_ranges = nPlusRanges;
	for (nOrigRanges = 0; nOrigRanges < nPlusRanges; nOrigRanges++) {
	    RangesetRefreshRange(origSet, newRanges->start, newRanges->end);
	    newRanges++;
	}
	return nPlusRanges;
    }

    oldRanges = origRanges;
    origSet->ranges = newRanges;
    origSet->n_ranges = 0;

    /* in the following we merrily swap the pointers/counters of the two input
       ranges (from origSet and plusSet) - don't worry, they're both consulted 
       read-only - building the merged set in newRanges */

    isOld = 1;		/* true if origRanges points to a range in oldRanges[] */

    while (nOrigRanges > 0 || nPlusRanges > 0) {
	/* make the range with the lowest start value the origRanges range */
	if (nOrigRanges == 0 || 
              (nPlusRanges > 0 && origRanges->start > plusRanges->start)) {
	    SWAPval(Range *, &origRanges, &plusRanges);
	    SWAPval(int, &nOrigRanges, &nPlusRanges);
	    isOld = !isOld;
	}

	origSet->n_ranges++;		/* we're using a new result range */

	*newRanges = *origRanges++;
	nOrigRanges--;
	if (!isOld)
	    RangesetRefreshRange(origSet, newRanges->start, newRanges->end);

	/* now we must cycle over plusRanges, merging in the overlapped ranges */
	while (nPlusRanges > 0 && newRanges->end >= plusRanges->start) {
	    do {
		if (newRanges->end < plusRanges->end) {
		    if (isOld)
			RangesetRefreshRange(origSet, newRanges->end, plusRanges->end);
		    newRanges->end = plusRanges->end;
		}
		plusRanges++;
		nPlusRanges--;
	    } while (nPlusRanges > 0 && newRanges->end >= plusRanges->start);

	    /* by now, newRanges->end may have extended to overlap more ranges in origRanges,
	       so swap and start again */
	    SWAPval(Range *, &origRanges, &plusRanges);
	    SWAPval(int, &nOrigRanges, &nPlusRanges);
	    isOld = !isOld;
	}

	/* OK: now *newRanges holds the result of merging all the first ranges from
	   origRanges and plusRanges - now we have a break in contiguity, so move on to the
	   next newRanges in the result */
	newRanges++;
    }

    /* finally, forget the old rangeset values, and reallocate the new ones */
    RangesFree(oldRanges);
    origSet->ranges = RangesRealloc(origSet->ranges, origSet->n_ranges);

    return origSet->n_ranges;
}


/* -------------------------------------------------------------------------- */

/*
** Subtract the ranges of minusSet from rangeset origSet.
*/

int RangesetRemove(Rangeset *origSet, Rangeset *minusSet)
{
    Range *origRanges, *minusRanges, *newRanges, *oldRanges;
    int nOrigRanges, nMinusRanges;

    origRanges = origSet->ranges;
    nOrigRanges = origSet->n_ranges;

    minusRanges = minusSet->ranges;
    nMinusRanges = minusSet->n_ranges;

    if (nOrigRanges == 0 || nMinusRanges == 0)
	return 0;		/* no ranges in origSet or minusSet - nothing to do */

    /* we must provide more space: each range in minusSet might split a range in origSet */
    newRanges = RangesNew(origSet->n_ranges + minusSet->n_ranges);

    oldRanges = origRanges;
    origSet->ranges = newRanges;
    origSet->n_ranges = 0;

    /* consider each range in origRanges - we do not change any of minusRanges's data, but we
       may change origRanges's - it will be discarded at the end */

    while (nOrigRanges > 0) {
	do {
	    /* skip all minusRanges ranges strictly in front of *origRanges */
	    while (nMinusRanges > 0 && minusRanges->end <= origRanges->start) {
		minusRanges++;		/* *minusRanges in front of *origRanges: move onto next *minusRanges */
		nMinusRanges--;
	    }

	    if (nMinusRanges > 0) {
		/* keep all origRanges ranges strictly in front of *minusRanges */
		while (nOrigRanges > 0 && origRanges->end <= minusRanges->start) {
		    *newRanges++ = *origRanges++;   /* *minusRanges beyond *origRanges: save *origRanges in *newRanges */
		    nOrigRanges--;
		    origSet->n_ranges++;
		}
	    }
	    else {
		/* no more minusRanges ranges to remove - save the rest of origRanges */
		while (nOrigRanges > 0) {
		    *newRanges++ = *origRanges++;
		    nOrigRanges--;
		    origSet->n_ranges++;
	      }
	    }
	} while (nMinusRanges > 0 && minusRanges->end <= origRanges->start); /* any more non-overlaps */

	/* when we get here either we're done, or we have overlap */
	if (nOrigRanges > 0) {
	    if (minusRanges->start <= origRanges->start) {
		/* origRanges->start inside *minusRanges */
		if (minusRanges->end < origRanges->end) {
		    RangesetRefreshRange(origSet, origRanges->start, minusRanges->end);
		    origRanges->start = minusRanges->end;  /* cut off front of original *origRanges */
		    minusRanges++;		    /* dealt with this *minusRanges: move on */
		    nMinusRanges--;
		}
		else {
		    /* all *origRanges inside *minusRanges */
		    RangesetRefreshRange(origSet, origRanges->start, origRanges->end);
		    origRanges++;			/* all of *origRanges can be skipped */
		    nOrigRanges--;
		}
	    }
	    else {
		/* minusRanges->start inside *origRanges: save front, adjust or skip rest */
		newRanges->start = origRanges->start;	/* save front of *origRanges in *newRanges */
		newRanges->end = minusRanges->start;
		newRanges++;
		origSet->n_ranges++;

		if (minusRanges->end < origRanges->end) {
		    /* all *minusRanges inside *origRanges */
		    RangesetRefreshRange(origSet, minusRanges->start, minusRanges->end); 
		    origRanges->start = minusRanges->end; /* cut front of *origRanges upto end *minusRanges */
		    minusRanges++;		   /* dealt with this *minusRanges: move on */
		    nMinusRanges--;
		}
		else {
		    /* minusRanges->end beyond *origRanges */
		    RangesetRefreshRange(origSet, minusRanges->start, origRanges->end); 
		    origRanges++;			/* skip rest of *origRanges */
		    nOrigRanges--;
		}
	    }
	}
    }

    /* finally, forget the old rangeset values, and reallocate the new ones */
    RangesFree(oldRanges);
    origSet->ranges = RangesRealloc(origSet->ranges, origSet->n_ranges);

    return origSet->n_ranges;
}


/* -------------------------------------------------------------------------- */

/*
** Get number of ranges in rangeset.
*/

int RangesetGetNRanges(Rangeset *rangeset)
{
    return rangeset ? rangeset->n_ranges : 0;
}


/* 
** Get information about rangeset.
*/
void RangesetGetInfo(Rangeset *rangeset, int *defined, int *label, 
        int *count, char **color, char **name, char **mode)
{
    if (rangeset == NULL) {
        *defined = False;
        *label = 0;
        *count = 0;
        *color = "";
        *name = "";
        *mode = "";
    }
    else {
        *defined = True;
        *label = (int)rangeset->label;
        *count = rangeset->n_ranges;
        *color = rangeset->color_name ? rangeset->color_name : "";
        *name = rangeset->name ? rangeset->name : "";
        *mode = rangeset->update_name;
    }
}

/* -------------------------------------------------------------------------- */

/*
** Set maxpos for rangeset rangeset.
*/

void RangesetSetMaxpos(Rangeset *rangeset, int maxpos)
{
    if (rangeset)
	rangeset->maxpos = maxpos;
}

/* -------------------------------------------------------------------------- */

static Rangeset *rangesetFixMaxpos(Rangeset *rangeset, int ins, int del)
{
    rangeset->maxpos += ins - del;
    return rangeset;
}

/* -------------------------------------------------------------------------- */

/*
** Allocate and initialise, or empty and free a ranges set table.
*/

RangesetTable *RangesetTableAlloc(textBuffer *buffer)
{
    int i;
    RangesetTable *table = (RangesetTable *)XtMalloc(sizeof (RangesetTable));

    if (!table)
	return table;

    table->buf = buffer;

    for (i = 0; i < N_RANGESETS; i++) {
	RangesetInit(&table->set[i], rangeset_labels[i], buffer);
	table->order[i] = (unsigned char)i;
	table->active[i] = 0;
	table->depth[i] = (unsigned char)i;
    }

    table->n_set = 0;
    table->list[0] = '\0';
    /* Range sets must be updated before the text display callbacks are
       called to avoid highlighted ranges getting out of sync. */
    BufAddHighPriorityModifyCB(buffer, RangesetBufModifiedCB, table);
    return table;
}

RangesetTable *RangesetTableFree(RangesetTable *table)
{
    int i;

    if (table) {
	BufRemoveModifyCB(table->buf, RangesetBufModifiedCB, table);
	for (i = 0; i < N_RANGESETS; i++)
	    RangesetEmpty(&table->set[i]);
	XtFree((char *)table);
    }
    return (RangesetTable *)0;
}

/*
** Find a range set given its label in the table.
*/

int RangesetFindIndex(RangesetTable *table, int label, int must_be_active)
{
    int i;
    unsigned char *p_label;
    
    if(label == 0) {
       return -1;
    }

    if (table != NULL) {
	p_label = (unsigned char*)strchr((char*)rangeset_labels, label);
	if (p_label) {
	    i = p_label - rangeset_labels;
	    if (!must_be_active || table->active[i])
		return i;
	}
    }

    return -1;
}


/*
** Assign the range set table list.
*/

static void RangesetTableListSet(RangesetTable *table)
{
    int i;

    for (i = 0; i < table->n_set; i++)
	table->list[i] = rangeset_labels[(int)table->order[i]];
    table->list[table->n_set] = '\0';
}

/*
** Return true if label is a valid identifier for a range set.
*/

int RangesetLabelOK(int label)
{
    return strchr((char*)rangeset_labels, label) != NULL;
}

/*
** Helper routines for managing the order and depth tables.
*/

static int activateRangeset(RangesetTable *table, int active)
{
    int depth, i, j;

    if (table->active[active])
	return 0;			/* already active */

    depth = table->depth[active];

    /* we want to make the "active" set the most recent (lowest depth value):
       shuffle table->order[0..depth-1] to table->order[1..depth]
       readjust the entries in table->depth[] accordingly */
    for (i = depth; i > 0; i--) {
	j = table->order[i] = table->order[i - 1];
	table->depth[j] = i;
    }
    /* insert the new one: first in order, of depth 0 */
    table->order[0] = active;
    table->depth[active] = 0;

    /* and finally... */
    table->active[active] = 1;
    table->n_set++;

    RangesetTableListSet(table);

    return 1;
}

static int deactivateRangeset(RangesetTable *table, int active)
{
    int depth, n, i, j;

    if (!table->active[active])
	return 0;			/* already inactive */

    /* we want to start by swapping the deepest entry in order with active
       shuffle table->order[depth+1..n_set-1] to table->order[depth..n_set-2]
       readjust the entries in table->depth[] accordingly */
    depth = table->depth[active];