Merge branch 'ical'

[alpine.git] / pith / thread.c

#if !defined(lint) && !defined(DOS)
static char rcsid[] = "$Id: thread.c 942 2008-03-04 18:21:33Z hubert@u.washington.edu $";
#endif

/*
 * ========================================================================
 * Copyright 2013-2017 Eduardo Chappa
 * Copyright 2006-2008 University of Washington
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * ========================================================================
 */

#include "../pith/headers.h"
#include "../pith/thread.h"
#include "../pith/flag.h"
#include "../pith/icache.h"
#include "../pith/mailindx.h"
#include "../pith/msgno.h"
#include "../pith/sort.h"
#include "../pith/pineelt.h"
#include "../pith/status.h"
#include "../pith/news.h"
#include "../pith/search.h"
#include "../pith/mailcmd.h"
#include "../pith/ablookup.h"


/*
 * Internal prototypes
 */
long *sort_thread_flatten(THREADNODE *, MAILSTREAM *, long *,
                          char *, long, PINETHRD_S *, unsigned);
void               make_thrdflags_consistent(MAILSTREAM *, MSGNO_S *, PINETHRD_S *, int);
THREADNODE        *collapse_threadnode_tree(THREADNODE *);
THREADNODE        *collapse_threadnode_tree_sorted(THREADNODE *);
THREADNODE        *sort_threads_and_collapse(THREADNODE *);
THREADNODE        *insert_tree_in_place(THREADNODE *, THREADNODE *);
unsigned long      branch_greatest_num(THREADNODE *, int);
long               calculate_visible_threads(MAILSTREAM *);


PINETHRD_S *
fetch_thread(MAILSTREAM *stream, long unsigned int rawno)
{
    MESSAGECACHE *mc;
    PINELT_S     *pelt;
    PINETHRD_S   *thrd = NULL;

    if(stream && rawno > 0L && rawno <= stream->nmsgs
       && !sp_need_to_rethread(stream)){
        mc = (rawno > 0L && stream && rawno <= stream->nmsgs)
                ? mail_elt(stream, rawno) : NULL;
        if(mc && (pelt = (PINELT_S *) mc->sparep))
          thrd = pelt->pthrd;
    }

    return(thrd);
}


PINETHRD_S *
fetch_head_thread(MAILSTREAM *stream)
{
    unsigned long rawno;
    PINETHRD_S   *thrd = NULL;

    if(stream){
        /* first find any thread */
        for(rawno = 1L; !thrd && rawno <= stream->nmsgs; rawno++)
          thrd = fetch_thread(stream, rawno);

        if(thrd && thrd->head)
          thrd = fetch_thread(stream, thrd->head);
    }

    return(thrd);
}


/*
 * Set flag f to v for all messages in thrd.
 *
 * Watch out when calling this. The thrd->branch is not part of thrd.
 * Branch is a sibling to thrd, not a child. Zero out branch before calling
 * or call on thrd->next and worry about thrd separately.
 * Ok to call it on top-level thread which has no branch already.
 */
void
set_flags_for_thread(MAILSTREAM *stream, MSGNO_S *msgmap, int f, PINETHRD_S *thrd, int v)
{
    PINETHRD_S *nthrd, *bthrd;

    if(!(stream && thrd && msgmap))
      return;

    set_lflag(stream, msgmap, mn_raw2m(msgmap, thrd->rawno), f, v);

    if(thrd->next){
        nthrd = fetch_thread(stream, thrd->next);
        if(nthrd)
          set_flags_for_thread(stream, msgmap, f, nthrd, v);
    }

    if(thrd->branch){
        bthrd = fetch_thread(stream, thrd->branch);
        if(bthrd)
          set_flags_for_thread(stream, msgmap, f, bthrd, v);
    }
}


void
erase_threading_info(MAILSTREAM *stream, MSGNO_S *msgmap)
{
    unsigned long n;
    MESSAGECACHE *mc;
    PINELT_S     *peltp;

    if(!(stream && stream->spare))
      return;
    
    ps_global->view_skipped_index = 0;
    sp_set_viewing_a_thread(stream, 0);
    
    if(THRD_INDX())
      setup_for_thread_index_screen();
    else
      setup_for_index_index_screen();

    stream->spare = 0;

    for(n = 1L; n <= stream->nmsgs; n++){
        set_lflag(stream, msgmap, mn_raw2m(msgmap, n),
                  MN_COLL | MN_CHID | MN_CHID2, 0);
        mc = mail_elt(stream, n);
        if(mc && mc->sparep){
            peltp = (PINELT_S *) mc->sparep;
            if(peltp->pthrd)
              fs_give((void **) &peltp->pthrd);
        }
    }
}


void
sort_thread_callback(MAILSTREAM *stream, THREADNODE *tree)
{
    THREADNODE *collapsed_tree = NULL;
    PINETHRD_S   *thrd = NULL;
    unsigned long msgno, rawno;
    int           un_view_thread = 0;
    long          raw_current;
    char         *dup_chk = NULL;


    dprint((2, "sort_thread_callback\n"));

    g_sort.msgmap->max_thrdno = 0L;

    /*
     * Eliminate dummy nodes from tree and collapse the tree in a logical
     * way. If the dummy node is at the top-level, then its children are
     * promoted to the top-level as separate threads.
     */
    if(F_ON(F_THREAD_SORTS_BY_ARRIVAL, ps_global))
      collapsed_tree = collapse_threadnode_tree_sorted(tree);
    else
      collapsed_tree = collapse_threadnode_tree(tree);

    /* dup_chk is like sort with an origin of 1 */
    dup_chk = (char *) fs_get((mn_get_nmsgs(g_sort.msgmap)+1) * sizeof(char));
    memset(dup_chk, 0, (mn_get_nmsgs(g_sort.msgmap)+1) * sizeof(char));

    memset(&g_sort.msgmap->sort[1], 0, mn_get_total(g_sort.msgmap) * sizeof(long));

    (void) sort_thread_flatten(collapsed_tree, stream,
                               &g_sort.msgmap->sort[1],
                               dup_chk, mn_get_nmsgs(g_sort.msgmap),
                               NULL, THD_TOP);

    /* reset the inverse array */
    msgno_reset_isort(g_sort.msgmap);

    if(dup_chk)
      fs_give((void **) &dup_chk);

    if(collapsed_tree)
      mail_free_threadnode(&collapsed_tree);

    if(any_lflagged(g_sort.msgmap, MN_HIDE))
      g_sort.msgmap->visible_threads = calculate_visible_threads(stream);
    else
      g_sort.msgmap->visible_threads = g_sort.msgmap->max_thrdno;

    raw_current = mn_m2raw(g_sort.msgmap, mn_get_cur(g_sort.msgmap));

    sp_set_need_to_rethread(stream, 0);

    /*
     * Set appropriate bits to start out collapsed if desired. We use the
     * stream spare bit to tell us if we've done this before for this
     * stream.
     */
    if(!stream->spare
       && (COLL_THRDS() || SEP_THRDINDX())
       && mn_get_total(g_sort.msgmap) > 1L){

        collapse_threads(stream, g_sort.msgmap, NULL);
    }
    else if(stream->spare){
        
        /*
         * If we're doing auto collapse then new threads need to have
         * their collapse bit set. This happens below if we're in the
         * thread index, but if we're in the regular index with auto
         * collapse we have to look for these.
         */
        if(any_lflagged(g_sort.msgmap, MN_USOR)){
            if(COLL_THRDS()){
                for(msgno = 1L; msgno <= mn_get_total(g_sort.msgmap); msgno++){
                    rawno = mn_m2raw(g_sort.msgmap, msgno);
                    if(get_lflag(stream, NULL, rawno, MN_USOR)){
                        thrd = fetch_thread(stream, rawno);

                        /*
                         * Node is new, unsorted, top-level thread,
                         * and we're using auto collapse.
                         */
                        if(thrd && !thrd->parent)
                          set_lflag(stream, g_sort.msgmap, msgno, MN_COLL, 1);
                        
                        /*
                         * If a parent is collapsed, clear that parent's
                         * index cache entry. This is only necessary if
                         * the parent's index display can depend on its
                         * children, of course.
                         */
                        if(thrd && thrd->parent){
                            thrd = fetch_thread(stream, thrd->parent);
                            while(thrd){
                                long t;

                                if(get_lflag(stream, NULL, thrd->rawno, MN_COLL)
                                   && (t = mn_raw2m(g_sort.msgmap,
                                                    (long) thrd->rawno)))
                                  clear_index_cache_ent(stream, t, 0);

                                if(thrd->parent)
                                  thrd = fetch_thread(stream, thrd->parent);
                                else
                                  thrd = NULL;
                            }
                        }

                    }
                }
            }

            set_lflags(stream, g_sort.msgmap, MN_USOR, 0);
        }

        if(sp_viewing_a_thread(stream)){
            if(any_lflagged(g_sort.msgmap, MN_CHID2)){
                /* current should be part of viewed thread */
                if(get_lflag(stream, NULL, raw_current, MN_CHID2)){
                    thrd = fetch_thread(stream, raw_current);
                    if(thrd && thrd->top && thrd->top != thrd->rawno)
                      thrd = fetch_thread(stream, thrd->top);
                    
                    if(thrd){
                        /*
                         * For messages that are part of thread set MN_CHID2
                         * and for messages that aren't part of the thread
                         * clear MN_CHID2. Easiest is to just do it instead
                         * of checking if it is true first.
                         */
                        set_lflags(stream, g_sort.msgmap, MN_CHID2, 0);
                        set_thread_lflags(stream, thrd, g_sort.msgmap,
                                          MN_CHID2, 1);
                        
                        /*
                         * Outside of the viewed thread everything else
                         * should be collapsed at the top-levels.
                         */
                        collapse_threads(stream, g_sort.msgmap, thrd);

                        /*
                         * Inside of the thread, the top of the thread
                         * can't be hidden, the rest are hidden if a
                         * parent somewhere above them is collapsed.
                         * There can be collapse points that are hidden
                         * inside of the tree. They remain collapsed even
                         * if the parent above them uncollapses.
                         */
                        msgno = mn_raw2m(g_sort.msgmap, (long) thrd->rawno);
                        if(msgno)
                          set_lflag(stream, g_sort.msgmap, msgno, MN_CHID, 0);

                        if(thrd->next){
                            PINETHRD_S *nthrd;

                            nthrd = fetch_thread(stream, thrd->next);
                            if(nthrd)
                              make_thrdflags_consistent(stream, g_sort.msgmap,
                                                        nthrd,
                                                        get_lflag(stream, NULL,
                                                                  thrd->rawno,
                                                                  MN_COLL));
                        }
                    }
                    else
                      un_view_thread++;
                }
                else
                  un_view_thread++;
            }
            else
              un_view_thread++;

            if(un_view_thread){
                set_lflags(stream, g_sort.msgmap, MN_CHID2, 0);
                unview_thread(ps_global, stream, g_sort.msgmap);
            }
            else{
                mn_reset_cur(g_sort.msgmap,
                             mn_raw2m(g_sort.msgmap, raw_current));
                view_thread(ps_global, stream, g_sort.msgmap, 0);
            }
        }
        else if(SEP_THRDINDX()){
            set_lflags(stream, g_sort.msgmap, MN_CHID2, 0);
            collapse_threads(stream, g_sort.msgmap, NULL);
        }
        else{
            thrd = fetch_head_thread(stream);
            while(thrd){
                /*
                 * The top-level threads aren't hidden by collapse.
                 */
                msgno = mn_raw2m(g_sort.msgmap, thrd->rawno);
                if(msgno)
                  set_lflag(stream, g_sort.msgmap, msgno, MN_CHID, 0);

                if(thrd->next){
                    PINETHRD_S *nthrd;

                    nthrd = fetch_thread(stream, thrd->next);
                    if(nthrd)
                      make_thrdflags_consistent(stream, g_sort.msgmap,
                                                nthrd,
                                                get_lflag(stream, NULL,
                                                          thrd->rawno,
                                                          MN_COLL));
                }

                if(thrd->nextthd)
                  thrd = fetch_thread(stream, thrd->nextthd);
                else
                  thrd = NULL;
            }
        }
    }

    stream->spare = 1;

    dprint((2, "sort_thread_callback done\n"));
}


void
collapse_threads(MAILSTREAM *stream, MSGNO_S *msgmap, PINETHRD_S *not_this_thread)
{
    PINETHRD_S   *thrd = NULL, *nthrd;
    unsigned long msgno;

    dprint((9, "collapse_threads\n"));

    thrd = fetch_head_thread(stream);
    while(thrd){
        if(thrd != not_this_thread){
            msgno = mn_raw2m(g_sort.msgmap, thrd->rawno);

            /* set collapsed bit */
            if(msgno){
                set_lflag(stream, g_sort.msgmap, msgno, MN_COLL, 1);
                set_lflag(stream, g_sort.msgmap, msgno, MN_CHID, 0);
            }

            /* hide its children */
            if(thrd->next && (nthrd = fetch_thread(stream, thrd->next)))
              set_thread_subtree(stream, nthrd, msgmap, 1, MN_CHID);
        }

        if(thrd->nextthd)
          thrd = fetch_thread(stream, thrd->nextthd);
        else
          thrd = NULL;
    }

    dprint((9, "collapse_threads done\n"));
}


void
make_thrdflags_consistent(MAILSTREAM *stream, MSGNO_S *msgmap, PINETHRD_S *thrd,
                          int a_parent_is_collapsed)
{
    PINETHRD_S *nthrd, *bthrd;
    unsigned long msgno;

    if(!thrd)
      return;

    msgno = mn_raw2m(msgmap, thrd->rawno);

    if(a_parent_is_collapsed){
        /* if some parent is collapsed, we should be hidden */
        if(msgno)
          set_lflag(stream, msgmap, msgno, MN_CHID, 1);
    }
    else{
        /* no parent is collapsed so we are not hidden */
        if(msgno)
          set_lflag(stream, msgmap, msgno, MN_CHID, 0);
    }

    if(thrd->next){
        nthrd = fetch_thread(stream, thrd->next);
        if(nthrd)
          make_thrdflags_consistent(stream, msgmap, nthrd,
                                    a_parent_is_collapsed
                                      ? a_parent_is_collapsed
                                      : get_lflag(stream, NULL, thrd->rawno,
                                                  MN_COLL));
    }

    if(thrd->branch){
        bthrd = fetch_thread(stream, thrd->branch);
        if(bthrd)
          make_thrdflags_consistent(stream, msgmap, bthrd,
                                    a_parent_is_collapsed);
    }
}


long
calculate_visible_threads(MAILSTREAM *stream)
{
    PINETHRD_S   *thrd = NULL;
    long          vis = 0L;

    thrd = fetch_head_thread(stream);
    while(thrd){
        vis += (thread_has_some_visible(stream, thrd) ? 1 : 0);

        if(thrd->nextthd)
          thrd = fetch_thread(stream, thrd->nextthd);
        else
          thrd = NULL;
    }

    return(vis);
}


/*
 * This routine does a couple things. The input is the THREADNODE node
 * that we get from c-client because of the THREAD command. The rest of
 * the arguments are used to help guide this function through its
 * recursive steps. One thing it does is to place the sort order in
 * the array initially pointed to by the entry argument. All it is doing
 * is walking the tree in the next then branch order you see below and
 * incrementing the entry number one for each node. The other thing it
 * is doing at the same time is to create a PINETHRD_S tree from the
 * THREADNODE tree. The two trees are completely equivalent but the
 * PINETHRD_S version has additional back pointers and parent pointers
 * and so on to make it easier for alpine to deal with it. Each node
 * of that tree is tied to the data associated with a particular message
 * by the msgno_thread_info() call, so that we can go from a message
 * number to the place in the thread tree that message sits.
 */
long *
sort_thread_flatten(THREADNODE *node, MAILSTREAM *stream,
                    long *entry, char *dup_chk, long maxno,
                    PINETHRD_S *thrd, unsigned int flags)
{
    PINETHRD_S *newthrd = NULL;

    if(node){
        if(node->num > 0L && node->num <= maxno){               /* holes happen */
            if(!dup_chk[node->num]){                            /* not a duplicate */
                *entry = node->num;
                dup_chk[node->num] = 1;

                /*
                 * Build a richer threading structure that will help us paint
                 * and operate on threads and subthreads.
                 */
                newthrd = msgno_thread_info(stream, node->num, thrd, flags);
                if(newthrd){
                  entry++;

                  if(node->next)
                    entry = sort_thread_flatten(node->next, stream,
                                                entry, dup_chk, maxno,
                                                newthrd, THD_NEXT);

                  if(node->branch)
                    entry = sort_thread_flatten(node->branch, stream,
                                                entry, dup_chk, maxno,
                                                newthrd,
                                                (flags == THD_TOP) ? THD_TOP
                                                                   : THD_BRANCH);
                }
            }
        }
    }

    return(entry);
}


/*
 * Make a copy of c-client's THREAD tree while eliminating dummy nodes.
 */
THREADNODE *
collapse_threadnode_tree(THREADNODE *tree)
{
    THREADNODE *newtree = NULL;

    if(tree){
        if(tree->num){
            newtree = mail_newthreadnode(NULL);
            newtree->num  = tree->num;
            if(tree->next)
              newtree->next = collapse_threadnode_tree(tree->next);

            if(tree->branch)
              newtree->branch = collapse_threadnode_tree(tree->branch);
        }
        else{
            if(tree->next)
              newtree = collapse_threadnode_tree(tree->next);
            
            if(tree->branch){
                if(newtree){
                    THREADNODE *last_branch = NULL;

                    /*
                     * Next moved up to replace "tree" in the tree.
                     * If next has no branches, then we want to branch off
                     * of next. If next has branches, we want to branch off
                     * of the last of those branches instead.
                     */
                    last_branch = newtree;
                    while(last_branch->branch)
                      last_branch = last_branch->branch;
                    
                    last_branch->branch = collapse_threadnode_tree(tree->branch);
                }
                else
                  newtree = collapse_threadnode_tree(tree->branch);
            }
        }
    }

    return(newtree);
}


/*
 * Like collapse_threadnode_tree, we collapse the dummy nodes.
 * In addition we rearrange the threads by order of arrival of
 * the last message in the thread, rather than the first message
 * in the thread.
 */
THREADNODE *
collapse_threadnode_tree_sorted(THREADNODE *tree)
{
    THREADNODE *sorted_tree = NULL;

    sorted_tree = sort_threads_and_collapse(tree);

    /* 
     * We used to eliminate top-level dummy nodes here so that
     * orphans would still get sorted together, but we changed
     * to sort the orphans themselves as top-level threads.
     *
     * It might be a matter of choice how they get sorted, but
     * we'll try doing it this way and not add another feature.
     */

    return(sorted_tree);
}

/*
 * Recurse through the tree, sorting each top-level branch by the
 * greatest num in the thread.
 */
THREADNODE *
sort_threads_and_collapse(THREADNODE *tree)
{
    THREADNODE *newtree = NULL, *newbranchtree = NULL, *newtreefree = NULL;

    if(tree){
        newtree = mail_newthreadnode(NULL);
        newtree->num  = tree->num;

        /* 
         * Only sort at the top level.  Individual threads can
         * rely on collapse_threadnode_tree 
         */
        if(tree->next)
          newtree->next = collapse_threadnode_tree(tree->next);

        if(tree->branch){
            /*
             * This recursive call returns an already re-sorted tree.
             * With that, we can loop through and inject ourselves
             * where we fit in with that sort, and pass back to the
             * caller to inject themselves.
             */
            newbranchtree = sort_threads_and_collapse(tree->branch);
        }

        if(newtree->num)
          newtree = insert_tree_in_place(newtree, newbranchtree);
        else{
            /*
             * If top node is a dummy, here is where we collapse it.
             */
            newtreefree = newtree;
            newtree = insert_tree_in_place(newtree->next, newbranchtree);
            newtreefree->next = NULL;
            mail_free_threadnode(&newtreefree);
        }
    }

    return(newtree);
}

/*
 * Recursively insert each of the top-level nodes in newtree in their place
 * in tree according to which tree has the most recent arrival
 */
THREADNODE *
insert_tree_in_place(THREADNODE *newtree, THREADNODE *tree)
{
    THREADNODE *node = NULL;
    unsigned long newtree_greatest_num = 0;
    if(newtree->branch){
        node = newtree->branch;
        newtree->branch = NULL;
        tree = insert_tree_in_place(node, tree);
    }

    newtree_greatest_num = branch_greatest_num(newtree, 0);

    if(tree){
        /*
         * Since tree is already sorted, we can insert when we find something
         * newtree is less than
         */
        if(newtree_greatest_num < branch_greatest_num(tree, 0))
          newtree->branch = tree;
        else {
            for(node = tree; node->branch; node = node->branch){
                if(newtree_greatest_num < branch_greatest_num(node->branch, 0)){
                    newtree->branch = node->branch;
                    node->branch = newtree;
                    break;
                }
            }
            if(!node->branch)
              node->branch = newtree;

            newtree = tree;
        }
    }

    return(newtree);
}

/*
 * Given a thread, return the greatest num in the tree.
 * is_subthread tells us not to recurse through branches, so
 * we can split the top level into threads.
 */
unsigned long
branch_greatest_num(THREADNODE *tree, int is_subthread)
{
    unsigned long ret, branch_ret;

    ret = tree->num;

    if(tree->next && (branch_ret = branch_greatest_num(tree->next, 1)) > ret)
      ret = branch_ret;
    if(is_subthread && tree->branch &&
       (branch_ret = branch_greatest_num(tree->branch, 1)) > ret)
      ret = branch_ret;

    return ret;
}


/*
 * Args      stream -- the usual
 *            rawno -- the raw msg num associated with this new node
 * attached_to_thrd -- the PINETHRD_S node that this is either a next or branch
 *                       off of
 *            flags --
 */
PINETHRD_S *
msgno_thread_info(MAILSTREAM *stream, long unsigned int rawno,
                  PINETHRD_S *attached_to_thrd, unsigned int flags)
{
    PINELT_S   **peltp;
    MESSAGECACHE *mc;

    if(!stream || rawno < 1L || rawno > stream->nmsgs)
      return NULL;

    /*
     * any private elt data yet?
     */
    if((mc = mail_elt(stream, rawno))
       && (*(peltp = (PINELT_S **) &mc->sparep) == NULL)){
        *peltp = (PINELT_S *) fs_get(sizeof(PINELT_S));
        memset(*peltp, 0, sizeof(PINELT_S));
    }

    if((*peltp)->pthrd == NULL)
      (*peltp)->pthrd = (PINETHRD_S *) fs_get(sizeof(PINETHRD_S));

    memset((*peltp)->pthrd, 0, sizeof(PINETHRD_S));

    (*peltp)->pthrd->rawno = rawno;

    if(attached_to_thrd)
      (*peltp)->pthrd->head = attached_to_thrd->head;
    else
      (*peltp)->pthrd->head = (*peltp)->pthrd->rawno;   /* it's me */

    if(flags == THD_TOP){
        /*
         * We can tell this thread is a top-level thread because it doesn't
         * have a parent.
         */
        (*peltp)->pthrd->top = (*peltp)->pthrd->rawno;  /* I am a top */
        if(attached_to_thrd){
            attached_to_thrd->nextthd = (*peltp)->pthrd->rawno;
            (*peltp)->pthrd->prevthd  = attached_to_thrd->rawno;
            (*peltp)->pthrd->thrdno   = attached_to_thrd->thrdno + 1L;
        }
        else
            (*peltp)->pthrd->thrdno   = 1L;             /* 1st thread */

        g_sort.msgmap->max_thrdno = (*peltp)->pthrd->thrdno;
    }
    else if(flags == THD_NEXT){
        if(attached_to_thrd){
            attached_to_thrd->next  = (*peltp)->pthrd->rawno;
            (*peltp)->pthrd->parent = attached_to_thrd->rawno;
            (*peltp)->pthrd->top    = attached_to_thrd->top;
        }
    }
    else if(flags == THD_BRANCH){
        if(attached_to_thrd){
            attached_to_thrd->branch = (*peltp)->pthrd->rawno;
            (*peltp)->pthrd->parent  = attached_to_thrd->parent;
            (*peltp)->pthrd->top     = attached_to_thrd->top;
        }
    }

    return((*peltp)->pthrd);
}


/*
 * Collapse or expand a threading subtree. Not called from separate thread
 * index.
 */
void
collapse_or_expand(struct pine *state, MAILSTREAM *stream, MSGNO_S *msgmap,
                   long unsigned int msgno)
{
    int           collapsed, adjust_current = 0;
    PINETHRD_S   *thrd = NULL, *nthrd;
    unsigned long rawno;

    if(!stream)
      return;

    /*
     * If msgno is a good msgno, then we collapse or expand the subthread
     * which begins at msgno. If msgno is 0, we collapse or expand the
     * entire current thread.
     */

    if(msgno > 0L && msgno <= mn_get_total(msgmap)){
        rawno = mn_m2raw(msgmap, msgno);
        if(rawno)
          thrd = fetch_thread(stream, rawno);
    }
    else if(msgno == 0L){
        rawno = mn_m2raw(msgmap, mn_get_cur(msgmap));
        if(rawno)
          thrd = fetch_thread(stream, rawno);
        
        if(thrd && thrd->top != thrd->rawno){
            adjust_current++;
            thrd = fetch_thread(stream, thrd->top);
            
            /*
             * Special case. If the user is collapsing the entire thread
             * (msgno == 0), and we are in a Zoomed view, and the top of
             * the entire thread is not part of the Zoomed view, then watch
             * out. If we were to collapse the entire thread it would just
             * disappear, because the top is not in the Zoom. Therefore,
             * don't allow it. Do what the user probably wants, which is to
             * collapse the thread at that point instead of the entire thread,
             * leaving behind the top of the subthread to expand if needed.
             * In other words, treat it as if they didn't have the
             * F_SLASH_COLL_ENTIRE feature set.
             */
            collapsed = get_lflag(stream, NULL, thrd->rawno, MN_COLL)
                        && thrd->next;

            if(!collapsed && get_lflag(stream, NULL, thrd->rawno, MN_HIDE))
              thrd = fetch_thread(stream, rawno);
        }
    }


    if(!thrd)
      return;

    collapsed = get_lflag(stream, NULL, thrd->rawno, MN_COLL) && thrd->next;

    if(collapsed){
        msgno = mn_raw2m(msgmap, thrd->rawno);
        if(msgno > 0L && msgno <= mn_get_total(msgmap)){
            set_lflag(stream, msgmap, msgno, MN_COLL, 0);
            if(thrd->next){
                if((nthrd = fetch_thread(stream, thrd->next)) != NULL)
                  set_thread_subtree(stream, nthrd, msgmap, 0, MN_CHID);

                clear_index_cache_ent(stream, msgno, 0);
            }
        }
    }
    else if(thrd && thrd->next){
        msgno = mn_raw2m(msgmap, thrd->rawno);
        if(msgno > 0L && msgno <= mn_get_total(msgmap)){
            set_lflag(stream, msgmap, msgno, MN_COLL, 1);
            if((nthrd = fetch_thread(stream, thrd->next)) != NULL)
              set_thread_subtree(stream, nthrd, msgmap, 1, MN_CHID);

            clear_index_cache_ent(stream, msgno, 0);
        }
    }
    else
      q_status_message(SM_ORDER, 0, 1,
                       _("No thread to collapse or expand on this line"));
    
    /* if current is hidden, adjust */
    if(adjust_current)
      adjust_cur_to_visible(stream, msgmap);
}


/*
 * Select the messages in a subthread. If all of the messages are already
 * selected, unselect them. This routine is a bit strange because it
 * doesn't set the MN_SLCT bit. Instead, it sets MN_STMP in apply_command
 * and then thread_command copies the MN_STMP messages back to MN_SLCT.
 */
void
select_thread_stmp(struct pine *state, MAILSTREAM *stream, MSGNO_S *msgmap)
{
    PINETHRD_S   *thrd = NULL;
    unsigned long rawno, in_thread, set_in_thread, save_branch;

    /* ugly bit means the same thing as return of 1 from individual_select */
    state->ugly_consider_advancing_bit = 0;

    if(!(stream && msgmap))
      return;

    rawno = mn_m2raw(msgmap, mn_get_cur(msgmap));
    if(rawno)
      thrd = fetch_thread(stream, rawno);
    
    if(!thrd)
      return;
    
    /* run through thrd to see if it is all selected */
    save_branch = thrd->branch;
    thrd->branch = 0L;
    if((set_in_thread = count_lflags_in_thread(stream, thrd, msgmap, MN_STMP))
       == (in_thread = count_lflags_in_thread(stream, thrd, msgmap, MN_NONE))){
        /*
         * If everything is selected, the first unselect should cause
         * an autozoom. In order to trigger the right code in
         *   thread_command()
         *     copy_lflags()
         * we set the MN_HIDE bit on the current message here.
         */
        if(F_ON(F_AUTO_ZOOM, state) && !any_lflagged(msgmap, MN_HIDE)
           && any_lflagged(msgmap, MN_STMP) == mn_get_total(msgmap))
          set_lflag(stream, msgmap, mn_get_cur(msgmap), MN_HIDE, 1);
        set_thread_lflags(stream, thrd, msgmap, MN_STMP, 0);
    }
    else{
        set_thread_lflags(stream, thrd, msgmap, MN_STMP, 1);
        state->ugly_consider_advancing_bit = 1;
    }

    thrd->branch = save_branch;
    
    if(set_in_thread == in_thread)
      q_status_message1(SM_ORDER, 0, 3, _("Unselected %s messages in thread"),
                        comatose((long) in_thread));
    else if(set_in_thread == 0)
      q_status_message1(SM_ORDER, 0, 3, _("Selected %s messages in thread"),
                        comatose((long) in_thread));
    else
      q_status_message1(SM_ORDER, 0, 3,
                        _("Selected %s more messages in thread"),
                        comatose((long) (in_thread-set_in_thread)));
}


/*
 * Count how many of this system flag in this thread subtree.
 * If flags == 0 count the messages in the thread.
 *
 * Watch out when calling this. The thrd->branch is not part of thrd.
 * Branch is a sibling to thrd, not a child. Zero out branch before calling
 * or call on thrd->next and worry about thrd separately.
 * Ok to call it on top-level thread which has no branch already.
 */
unsigned long
count_flags_in_thread(MAILSTREAM *stream, PINETHRD_S *thrd, long int flags)
{
    unsigned long count = 0;
    PINETHRD_S *nthrd, *bthrd;
    MESSAGECACHE *mc;

    if(!thrd || !stream || thrd->rawno < 1L || thrd->rawno > stream->nmsgs)
      return count;
    
    if(thrd->next){
        nthrd = fetch_thread(stream, thrd->next);
        if(nthrd)
          count += count_flags_in_thread(stream, nthrd, flags);
    }

    if(thrd->branch){
        bthrd = fetch_thread(stream, thrd->branch);
        if(bthrd)
          count += count_flags_in_thread(stream, bthrd, flags);
    }

    mc = (thrd && thrd->rawno > 0L && stream && thrd->rawno <= stream->nmsgs)
          ? mail_elt(stream, thrd->rawno) : NULL;
    if(mc && mc->valid && FLAG_MATCH(flags, mc, stream))
      count++;

    return count;
}


/*
 * Count how many of this local flag in this thread subtree.
 * If flags == MN_NONE then we just count the messages instead of whether
 * the messages have a flag set.
 *
 * Watch out when calling this. The thrd->branch is not part of thrd.
 * Branch is a sibling to thrd, not a child. Zero out branch before calling
 * or call on thrd->next and worry about thrd separately.
 * Ok to call it on top-level thread which has no branch already.
 */
unsigned long
count_lflags_in_thread(MAILSTREAM *stream, PINETHRD_S *thrd, MSGNO_S *msgmap, int flags)
{
    unsigned long count = 0;
    PINETHRD_S *nthrd, *bthrd;

    if(!thrd || !stream || thrd->rawno < 1L || thrd->rawno > stream->nmsgs)
      return count;

    if(thrd->next){
        nthrd = fetch_thread(stream, thrd->next);
        if(nthrd)
          count += count_lflags_in_thread(stream, nthrd, msgmap, flags);
    }

    if(thrd->branch){
        bthrd = fetch_thread(stream, thrd->branch);
        if(bthrd)
          count += count_lflags_in_thread(stream, bthrd, msgmap,flags);
    }

    if(flags == MN_NONE)
      count++;
    else
      count += get_lflag(stream, msgmap, mn_raw2m(msgmap, thrd->rawno), flags);

    return count;
}


/*
 * Special-purpose for performance improvement.
 */
int
thread_has_some_visible(MAILSTREAM *stream, PINETHRD_S *thrd)
{
    PINETHRD_S *nthrd, *bthrd;

    if(!thrd || !stream || thrd->rawno < 1L || thrd->rawno > stream->nmsgs)
      return 0;

    if(get_lflag(stream, NULL, thrd->rawno, MN_HIDE) == 0)
      return 1;

    if(thrd->next){
        nthrd = fetch_thread(stream, thrd->next);
        if(nthrd && thread_has_some_visible(stream, nthrd))
          return 1;
    }

    if(thrd->branch){
        bthrd = fetch_thread(stream, thrd->branch);
        if(bthrd && thread_has_some_visible(stream, bthrd))
          return 1;
    }

    return 0;
}


int
mark_msgs_in_thread(MAILSTREAM *stream, PINETHRD_S *thrd, MSGNO_S *msgmap)
{
    int           count = 0;
    PINETHRD_S   *nthrd, *bthrd;
    MESSAGECACHE *mc;

    if(!thrd || !stream || thrd->rawno < 1L || thrd->rawno > stream->nmsgs)
      return count;

    if(thrd->next){
        nthrd = fetch_thread(stream, thrd->next);
        if(nthrd)
          count += mark_msgs_in_thread(stream, nthrd, msgmap);
    }

    if(thrd->branch){
        bthrd = fetch_thread(stream, thrd->branch);
        if(bthrd)
          count += mark_msgs_in_thread(stream, bthrd, msgmap);
    }

    if(stream && thrd->rawno >= 1L && thrd->rawno <= stream->nmsgs &&
       (mc = mail_elt(stream,thrd->rawno))
       && !mc->sequence
       && !mc->private.msg.env){
        mc->sequence = 1;
        count++;
    }

    return count;
}


/*
 * This sets or clears flags for the messages at this node and below in
 * a tree.
 *
 * Watch out when calling this. The thrd->branch is not part of thrd.
 * Branch is a sibling to thrd, not a child. Zero out branch before calling
 * or call on thrd->next and worry about thrd separately.
 * Ok to call it on top-level thread which has no branch already.
 */
void
set_thread_lflags(MAILSTREAM *stream, PINETHRD_S *thrd, MSGNO_S *msgmap, int flags, int v)
                       
                     
                       
                                /* flags to set or clear */
                                /* set or clear? */
{
    unsigned long msgno;
    PINETHRD_S *nthrd, *bthrd;

    if(!thrd || !stream || thrd->rawno < 1L || thrd->rawno > stream->nmsgs)
      return;

    msgno = mn_raw2m(msgmap, thrd->rawno);

    set_lflag(stream, msgmap, msgno, flags, v);

    /*
     * Careful, performance hack. This should logically be a separate
     * operation on the thread but it is convenient to stick it in here.
     *
     * When we back out of viewing a thread to the separate-thread-index
     * we may leave behind some cached hlines that aren't quite right
     * because they were collapsed. In particular, the plus_col character
     * may be wrong. Instead of trying to figure out what it should be just
     * clear the cache entries for the this thread when we come back in
     * to view it again.
     */
    if(msgno > 0L && flags == MN_CHID2 && v == 1)
      clear_index_cache_ent(stream, msgno, 0);

    if(thrd->next){
        nthrd = fetch_thread(stream, thrd->next);
        if(nthrd)
          set_thread_lflags(stream, nthrd, msgmap, flags, v);
    }

    if(thrd->branch){
        bthrd = fetch_thread(stream, thrd->branch);
        if(bthrd)
          set_thread_lflags(stream, bthrd, msgmap, flags, v);
    }
}


char
status_symbol_for_thread(MAILSTREAM *stream, PINETHRD_S *thrd, IndexColType type)
{
    char        status = ' ';
    unsigned long save_branch, cnt, tot_in_thrd;

    if(!thrd || !stream || thrd->rawno < 1L || thrd->rawno > stream->nmsgs)
      return status;

    save_branch = thrd->branch;
    thrd->branch = 0L;          /* branch is a sibling, not part of thread */
    
    /*
     * This is D if all of thread is deleted,
     * else A if all of thread is answered,
     * else F if all of thread is forwarded,
     * else N if any unseen and not deleted,
     * else blank.
     */
    if(type == iStatus){
        tot_in_thrd = count_flags_in_thread(stream, thrd, F_NONE);
        /* all deleted */
        if(count_flags_in_thread(stream, thrd, F_DEL) == tot_in_thrd)
          status = 'D';
        /* all answered */
        else if(count_flags_in_thread(stream, thrd, F_ANS) == tot_in_thrd)
          status = 'A';
        /* all forwarded */
        else if(count_flags_in_thread(stream, thrd, F_FWD) == tot_in_thrd)
          status = 'F';
        /* or any new and not deleted */
        else if((!IS_NEWS(stream)
                 || F_ON(F_FAKE_NEW_IN_NEWS, ps_global))
                && count_flags_in_thread(stream, thrd, F_UNDEL|F_UNSEEN))
          status = 'N';
    }
    else if(type == iFStatus){
        if(!IS_NEWS(stream) || F_ON(F_FAKE_NEW_IN_NEWS, ps_global)){
            tot_in_thrd = count_flags_in_thread(stream, thrd, F_NONE);
            cnt = count_flags_in_thread(stream, thrd, F_UNSEEN);
            if(cnt)
              status = (cnt == tot_in_thrd) ? 'N' : 'n';
        }
    }
    else if(type == iIStatus || type == iSIStatus){
        tot_in_thrd = count_flags_in_thread(stream, thrd, F_NONE);

        /* unseen and recent */
        cnt = count_flags_in_thread(stream, thrd, F_RECENT|F_UNSEEN);
        if(cnt)
          status = (cnt == tot_in_thrd) ? 'N' : 'n';
        else{
            /* unseen and !recent */
            cnt = count_flags_in_thread(stream, thrd, F_UNSEEN);
            if(cnt)
              status = (cnt == tot_in_thrd) ? 'U' : 'u';
            else{
                /* seen and recent */
                cnt = count_flags_in_thread(stream, thrd, F_RECENT|F_SEEN);
                if(cnt)
                  status = (cnt == tot_in_thrd) ? 'R' : 'r';
            }
        }
    }

    thrd->branch = save_branch;

    return status;
}


/*
 * Symbol is * if some message in thread is important,
 * + if some message is to us,
 * - if mark-for-cc and some message is cc to us, else blank.
 */
char
to_us_symbol_for_thread(MAILSTREAM *stream, PINETHRD_S *thrd, int consider_flagged)
{
    char        to_us = ' ';
    char        branch_to_us = ' ';
    PINETHRD_S *nthrd, *bthrd;
    MESSAGECACHE *mc;

    if(!thrd || !stream || thrd->rawno < 1L || thrd->rawno > stream->nmsgs)
      return to_us;

    if(thrd->next){
        nthrd = fetch_thread(stream, thrd->next);
        if(nthrd)
          to_us = to_us_symbol_for_thread(stream, nthrd, consider_flagged);
    }

    if(((consider_flagged && to_us != '*') || (!consider_flagged && to_us != '+'))
       && thrd->branch){
        bthrd = fetch_thread(stream, thrd->branch);
        if(bthrd)
          branch_to_us = to_us_symbol_for_thread(stream, bthrd, consider_flagged);

        /* use branch to_us symbol if it has higher priority than what we have so far */
        if(to_us == ' '){
            if(branch_to_us == '-' || branch_to_us == '+' || branch_to_us == '*')
              to_us = branch_to_us;
        }
        else if(to_us == '-'){
            if(branch_to_us == '+' || branch_to_us == '*')
              to_us = branch_to_us;
        }
        else if(to_us == '+'){
            if(branch_to_us == '*')
              to_us = branch_to_us;
        }
    }

    if((consider_flagged && to_us != '*') || (!consider_flagged && to_us != '+')){
        if(consider_flagged && thrd && thrd->rawno > 0L
           && stream && thrd->rawno <= stream->nmsgs
           && (mc = mail_elt(stream, thrd->rawno))
           && FLAG_MATCH(F_FLAG, mc, stream))
          to_us = '*';
        else if(to_us != '+' && !IS_NEWS(stream)){
            INDEXDATA_S   idata;
            MESSAGECACHE *mc;
            ADDRESS      *addr;

            memset(&idata, 0, sizeof(INDEXDATA_S));
            idata.stream   = stream;
            idata.rawno    = thrd->rawno;
            idata.msgno    = mn_raw2m(sp_msgmap(stream), idata.rawno);
            if(idata.rawno > 0L && stream && idata.rawno <= stream->nmsgs
               && (mc = mail_elt(stream, idata.rawno))){
                idata.size = mc->rfc822_size;
                index_data_env(&idata,
                               pine_mail_fetchenvelope(stream, idata.rawno));
            }
            else
              idata.bogus = 2;

            for(addr = fetch_to(&idata); addr; addr = addr->next)
              if(address_is_us(addr, ps_global)){
                  to_us = '+';
                  break;
              }
            
            if(to_us != '+' && resent_to_us(&idata))
              to_us = '+';

            if(to_us == ' ' && F_ON(F_MARK_FOR_CC,ps_global))
              for(addr = fetch_cc(&idata); addr; addr = addr->next)
                if(address_is_us(addr, ps_global)){
                    to_us = '-';
                    break;
                }
        }
    }

    return to_us;
}


/*
 * This sets or clears flags for the messages at this node and below in
 * a tree. It doesn't just blindly do it, perhaps it should. Instead,
 * when un-hiding a subtree it leaves the sub-subtree hidden if a node
 * is collapsed.
 *
 * Watch out when calling this. The thrd->branch is not part of thrd.
 * Branch is a sibling to thrd, not a child. Zero out branch before calling
 * or call on thrd->next and worry about thrd separately.
 * Ok to call it on top-level thread which has no branch already.
 */
void
set_thread_subtree(MAILSTREAM *stream, PINETHRD_S *thrd, MSGNO_S *msgmap, int v, int flags)
                       
                     
                       
                                /* set or clear? */
                                /* flags to set or clear */
{
    int hiding;
    unsigned long msgno;
    PINETHRD_S *nthrd, *bthrd;

    hiding = (flags == MN_CHID) && v;

    if(!thrd || !stream || thrd->rawno < 1L || thrd->rawno > stream->nmsgs)
      return;

    msgno = mn_raw2m(msgmap, thrd->rawno);

    set_lflag(stream, msgmap, msgno, flags, v);

    if(thrd->next && (hiding || !get_lflag(stream,NULL,thrd->rawno,MN_COLL))){
        nthrd = fetch_thread(stream, thrd->next);
        if(nthrd)
          set_thread_subtree(stream, nthrd, msgmap, v, flags);
    }

    if(thrd->branch){
        bthrd = fetch_thread(stream, thrd->branch);
        if(bthrd)
          set_thread_subtree(stream, bthrd, msgmap, v, flags);
    }
}


/*
 * View a thread. Move from the thread index screen to a message index
 * screen for the current thread.
 *
 *      set_lflags - Set the local flags appropriately to start viewing
 *                   the thread. We would not want to set this if we are
 *                   already viewing the thread (and expunge or new mail
 *                   happened) and we want to preserve the collapsed state
 *                   of the subthreads.
 */
int
view_thread(struct pine *state, MAILSTREAM *stream, MSGNO_S *msgmap, int set_lflags)
{
    PINETHRD_S   *thrd = NULL;
    unsigned long rawno, cur;

    if(!any_messages(msgmap, NULL, "to View"))
      return 0;

    if(!(stream && msgmap))
      return 0;

    rawno = mn_m2raw(msgmap, mn_get_cur(msgmap));
    if(rawno)
      thrd = fetch_thread(stream, rawno);

    if(thrd && thrd->top && thrd->top != thrd->rawno)
      thrd = fetch_thread(stream, thrd->top);
    
    if(!thrd)
      return 0;
    
    /*
     * Clear hidden and collapsed flag for this thread.
     * And set CHID2.
     * Don't have to worry about there being a branch because
     * this is a toplevel thread.
     */
    if(set_lflags){
        set_thread_lflags(stream, thrd, msgmap, MN_COLL | MN_CHID, 0);
        set_thread_lflags(stream, thrd, msgmap, MN_CHID2, 1);
    }

    /*
     * If this is one of those wacky users who like to sort backwards
     * they would probably prefer that the current message be the last
     * one in the thread (the one highest up the screen).
     */
    if(mn_get_revsort(msgmap)){
        cur = mn_get_cur(msgmap);
        while(cur > 1L && get_lflag(stream, msgmap, cur-1L, MN_CHID2))
          cur--;

        if(cur != mn_get_cur(msgmap))
          mn_set_cur(msgmap, cur);
    }

    /* first message in thread might be hidden if zoomed */
    if(any_lflagged(msgmap, MN_HIDE)){
        cur = mn_get_cur(msgmap);
        while(get_lflag(stream, msgmap, cur, MN_HIDE))
          cur++;
        
        if(cur != mn_get_cur(msgmap))
          mn_set_cur(msgmap, cur);
    }

    msgmap->top = mn_get_cur(msgmap);
    sp_set_viewing_a_thread(stream, 1);

    state->mangled_screen = 1;
    setup_for_index_index_screen();

    return 1;
}


int
unview_thread(struct pine *state, MAILSTREAM *stream, MSGNO_S *msgmap)
{
    PINETHRD_S   *thrd = NULL, *topthrd = NULL;
    unsigned long rawno;

    if(!(stream && msgmap))
      return 0;

    rawno = mn_m2raw(msgmap, mn_get_cur(msgmap));
    if(rawno)
      thrd = fetch_thread(stream, rawno);
    
    if(thrd && thrd->top)
      topthrd = fetch_thread(stream, thrd->top);
    
    if(!topthrd)
      return 0;

    /* hide this thread */
    set_thread_lflags(stream, topthrd, msgmap, MN_CHID, 1);

    /* clear special CHID2 flags for this thread */
    set_thread_lflags(stream, topthrd, msgmap, MN_CHID2, 0);

    /* clear CHID for top-level message and set COLL */
    set_lflag(stream, msgmap, mn_raw2m(msgmap, topthrd->rawno), MN_CHID, 0);
    set_lflag(stream, msgmap, mn_raw2m(msgmap, topthrd->rawno), MN_COLL, 1);

    mn_set_cur(msgmap, mn_raw2m(msgmap, topthrd->rawno));
    sp_set_viewing_a_thread(stream, 0);
    setup_for_thread_index_screen();

    return 1;
}


PINETHRD_S *
find_thread_by_number(MAILSTREAM *stream, MSGNO_S *msgmap, long int target, PINETHRD_S *startthrd)
{
    PINETHRD_S *thrd = NULL;

    if(!(stream && msgmap))
      return(thrd);

    thrd = startthrd;
    
    if(!thrd || !(thrd->prevthd || thrd->nextthd))
      thrd = fetch_thread(stream, mn_m2raw(msgmap, mn_get_cur(msgmap)));

    if(thrd && !(thrd->prevthd || thrd->nextthd) && thrd->head)
      thrd = fetch_thread(stream, thrd->head);

    if(thrd){
        /* go forward from here */
        if(thrd->thrdno < target){
            while(thrd){
                if(thrd->thrdno == target)
                  break;

                if(mn_get_revsort(msgmap) && thrd->prevthd)
                  thrd = fetch_thread(stream, thrd->prevthd);
                else if(!mn_get_revsort(msgmap) && thrd->nextthd)
                  thrd = fetch_thread(stream, thrd->nextthd);
                else
                  thrd = NULL;
            }
        }
        /* back up from here */
        else if(thrd->thrdno > target
                && (mn_get_revsort(msgmap)
                    || (thrd->thrdno - target) < (target - 1L))){
            while(thrd){
                if(thrd->thrdno == target)
                  break;

                if(mn_get_revsort(msgmap) && thrd->nextthd)
                  thrd = fetch_thread(stream, thrd->nextthd);
                else if(!mn_get_revsort(msgmap) && thrd->prevthd)
                  thrd = fetch_thread(stream, thrd->prevthd);
                else
                  thrd = NULL;
            }
        }
        /* go forward from head */
        else if(thrd->thrdno > target){
            if(thrd->head){
                thrd = fetch_thread(stream, thrd->head);
                while(thrd){
                    if(thrd->thrdno == target)
                      break;

                    if(thrd->nextthd)
                      thrd = fetch_thread(stream, thrd->nextthd);
                    else
                      thrd = NULL;
                }
            }
        }
    }

    return(thrd);
}


/*
 * Set search bit for every message in a thread.
 *
 * Watch out when calling this. The thrd->branch is not part of thrd.
 * Branch is a sibling to thrd, not a child. Zero out branch before calling
 * or call on thrd->next and worry about thrd separately. Top-level threads
 * already have a branch equal to zero.
 *
 *  If msgset is non-NULL, then only set the search bit for a message if that
 *  message is included in the msgset.
 */
void
set_search_bit_for_thread(MAILSTREAM *stream, PINETHRD_S *thrd, SEARCHSET **msgset)
{
    PINETHRD_S *nthrd, *bthrd;

    if(!(stream && thrd))
      return;

    if(thrd->rawno > 0L && thrd->rawno <= stream->nmsgs
       && (!(msgset && *msgset) || in_searchset(*msgset, thrd->rawno)))
      mm_searched(stream, thrd->rawno);

    if(thrd->next){
        nthrd = fetch_thread(stream, thrd->next);
        if(nthrd)
          set_search_bit_for_thread(stream, nthrd, msgset);
    }

    if(thrd->branch){
        bthrd = fetch_thread(stream, thrd->branch);
        if(bthrd)
          set_search_bit_for_thread(stream, bthrd, msgset);
    }
}