* For mailing lists, Alpine adds a description of the type of link

[alpine.git] / pith / detach.c

/*
 * ========================================================================
 * Copyright 2013-2022 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/detach.h"
#include "../pith/state.h"
#include "../pith/conf.h"
#include "../pith/store.h"
#include "../pith/filter.h"
#include "../pith/mailview.h"
#include "../pith/status.h"
#include "../pith/addrstring.h"
#include "../pith/bldaddr.h"
#include "../pith/mimedesc.h"
#include "../pith/adjtime.h"
#include "../pith/pipe.h"
#include "../pith/busy.h"
#include "../pith/signal.h"
#include "../pico/osdep/filesys.h"


/*
 * We need to define simple functions here for the piping and 
 * temporary storage object below.  We can use the filter.c functions
 * because they're already in use for the "putchar" function passed to
 * detach.
 */
static STORE_S *detach_so = NULL;


/*
 * The display filter is locally global because it's set in df_trigger_cmp
 * which sniffs at lines of the unencoded segment...
 */
typedef struct _trigger {
    int            (*cmp)(char *, char *);
    char            *text;
    char            *cmd;
    struct _trigger *next;
} TRGR_S;

static char     *display_filter;
static TRGR_S   *df_trigger_list;

FETCH_READC_S *g_fr_desc;

#define INIT_FETCH_CHUNK        ((unsigned long)(8 * 1024L))
#define MIN_FETCH_CHUNK         ((unsigned long)(4 * 1024L))
#define MAX_FETCH_CHUNK         ((unsigned long)(256 * 1024L))
#define TARGET_INTR_TIME        ((unsigned long)2000000L) /* two seconds */
#define FETCH_READC     g_fr_desc->readc


/*
 * Internal Prototypes
 */
/*
 * This function is intentionally declared without an argument type so
 * that warnings will go away in Windows. We're using gf_io_t for both
 * input and output functions and the arguments aren't actually the
 * same in the two cases. We should really have a read version and
 * a write version of gf_io_t. That's why this is like this for now.
 */
int         detach_writec();
TRGR_S     *build_trigger_list(void);
void        blast_trigger_list(TRGR_S **);
int         df_trigger_cmp(long, char *, LT_INS_S **, void *);
int         df_trigger_cmp_text(char *, char *);
int         df_trigger_cmp_lwsp(char *, char *);
int         df_trigger_cmp_start(char *, char *);
int         fetch_readc_cleanup(int);
char       *fetch_gets(readfn_t, void *, unsigned long, GETS_DATA *);
int         fetch_readc(unsigned char *);



/*----------------------------------------------------------------------
  detach the given raw body part; don't do any decoding

  Args: a bunch

  Returns: NULL on success, error message otherwise
  ----*/
char *
detach_raw(MAILSTREAM *stream,  /* c-client stream to use         */
           long int msg_no,     /* message number to deal with    */
           char *part_no,       /* part number of message         */
           gf_io_t pc,          /* where to put it                */
           int flags)
{
    FETCH_READC_S  *frd = (FETCH_READC_S *)fs_get(sizeof(FETCH_READC_S));
    char *err = NULL;
    int column = (flags & FM_DISPLAY) ? ps_global->ttyo->screen_cols : 80;
    
    memset(g_fr_desc = frd, 0, sizeof(FETCH_READC_S));
    frd->stream  = stream;
    frd->msgno   = msg_no;
    frd->section = part_no;
    frd->size    = 0;                   /* wouldn't be here otherwise     */
    frd->readc   = fetch_readc;
    frd->chunk   = pine_mail_fetch_text(stream, msg_no, NULL, &frd->read, 0);
    frd->endp    = &frd->chunk[frd->read];
    frd->chunkp  = frd->chunk;

    gf_filter_init();
    if (!(flags & FM_NOWRAP))
      gf_link_filter(gf_wrap, gf_wrap_filter_opt(column, column, NULL, 0,
                                                 (flags & FM_DISPLAY)
                                                   ? GFW_HANDLES : 0));
    err = gf_pipe(FETCH_READC, pc);

    return(err);
}


/*----------------------------------------------------------------------
  detach the given body part using the given encoding

  Args: a bunch

  Returns: NULL on success, error message otherwise
  ----*/
char *
detach(MAILSTREAM *stream,              /* c-client stream to use         */
       long int msg_no,                 /* message number to deal with    */
       char *part_no,                   /* part number of message         */
       long int partial,                /* if >0, limit read to this many bytes */
       long int *len,                   /* returns bytes read in this arg */
       gf_io_t pc,                      /* where to put it                */
       FILTLIST_S *aux_filters,         /* null terminated array of filts */
       long flags)
{
    unsigned long  rv;
    unsigned long  size;
    long           fetch_flags;
    int            we_cancel = 0, is_text;
    char          *status, trigger[MAILTMPLEN];
    char          *charset = NULL;
    BODY          *body;
    static char    err_string[100];
    FETCH_READC_S  fetch_part;

    err_string[0] = '\0';

    if(!ps_global->print && !pc_is_picotext(pc))
      we_cancel = busy_cue(NULL, NULL, 1);

    gf_filter_init();                   /* prepare for filtering! */

    if(!(body = mail_body(stream, msg_no, (unsigned char *) part_no)))
      return(_("Can't find body for requested message"));

    is_text = body->type == TYPETEXT;

    size = body->size.bytes;
    if(partial > 0L && partial < size)
      size = partial;

    fetch_flags = (flags & ~DT_NODFILTER);
    fetch_readc_init(&fetch_part, stream, msg_no, part_no, body->size.bytes, partial,
                     fetch_flags);
    rv = size ? size : 1;

    switch(body->encoding) {            /* handle decoding */
      case ENC7BIT:
      case ENC8BIT:
      case ENCBINARY:
        break;

      case ENCBASE64:
        gf_link_filter(gf_b64_binary, NULL);
        break;

      case ENCQUOTEDPRINTABLE:
        gf_link_filter(gf_qp_8bit, NULL);
        break;

      case ENCOTHER:
      default:
        dprint((1, "detach: unknown CTE: \"%s\" (%d)\n",
                   (body->encoding <= ENCMAX
                    && body_encodings[body->encoding])
                       ? body_encodings[body->encoding]
                       : "BEYOND-KNOWN-TYPES",
                   body->encoding));
        break;
    }

    /* convert all text to UTF-8 */
    if(is_text & !(flags & (DT_BINARY | DT_EXTERNAL))){
        charset = parameter_val(body->parameter, "charset");

        /*
         * If the charset is unlabeled or unknown replace it
         * with the user's configured unknown charset.
         */
        if(!charset || !strucmp(charset, UNKNOWN_CHARSET) 
                || !strucmp(charset, "MISSING_PARAMETER_VALUE")
                || !strucmp(charset, "us-ascii")){
            if(charset)
              fs_give((void **) &charset);

            if(ps_global->VAR_UNK_CHAR_SET)
              charset = cpystr(ps_global->VAR_UNK_CHAR_SET);
        }

        /* some messages are mislabeled as iso-8859-1 when in reality
         * they are windows-1252, so we treat them as windows-1252
         * from the beginning. If we did not make this change, we might
         * see '?' characters in the message, without an apparent explanation
         * of this fact.
         */
        if(charset && !strucmp(charset, "iso-8859-1")){
            fs_give((void **) &charset);
            charset = cpystr("windows-1252");
        }

        /* convert to UTF-8 */
        if(!(charset && !strucmp(charset, "utf-8")))
          gf_link_filter(gf_utf8, gf_utf8_opt(charset));

        if(charset)
          fs_give((void **) &charset);
    }

    /*
     * If we're detaching a text segment and there are user-defined
     * filters and there are text triggers to look for, install filter
     * to let us look at each line...
     */
    display_filter = NULL;
    if(is_text
       && ps_global->tools.display_filter
       && ps_global->tools.display_filter_trigger
       && ps_global->VAR_DISPLAY_FILTERS
       && !(flags & DT_NODFILTER)){
        /* check for "static" triggers (i.e., none or CHARSET) */
        if(!(display_filter = (*ps_global->tools.display_filter_trigger)(body, trigger, sizeof(trigger)))
           && (df_trigger_list = build_trigger_list())){
            /* else look for matching text trigger */
            gf_link_filter(gf_line_test,
                           gf_line_test_opt(df_trigger_cmp, NULL));
        }
    }
    else
      /* add aux filters if we're not going to MIME decode into a temporary
       * storage object, otherwise we pass the aux_filters on to gf_filter
       * below so it can pass what comes out of the external filter command
       * thru the rest of the filters...
       */
      for( ; aux_filters && aux_filters->filter; aux_filters++)
        gf_link_filter(aux_filters->filter, aux_filters->data);

    /*
     * Following canonical model, after decoding convert newlines from
     * crlf to local convention.  ALSO, convert newlines if we're fetching
     * a multipart segment since an external handler's going to have to
     * make sense of it...
     */
    if((is_text & !(flags & DT_BINARY)) 
        || body->type == TYPEMESSAGE 
        || body->type == TYPEMULTIPART)
      gf_link_filter(gf_nvtnl_local, NULL);

    if(flags & DT_EXTERNAL){
        char i = flags & DT_ALLIMAGES ? 'i' : '\0';
        gf_link_filter(gf_html_cid2file, (void *) &i);
    }

    /*
     * If we're detaching a text segment and a user-defined filter may
     * need to be invoked later (see below), decode the segment into
     * a temporary storage object...
     */
    if(is_text
       && ps_global->tools.display_filter
       && ps_global->tools.display_filter_trigger
       && ps_global->VAR_DISPLAY_FILTERS
       && !(flags & DT_NODFILTER)
       && !(detach_so = so_get(CharStar, NULL, EDIT_ACCESS))){
      strncpy(err_string,
           _("Formatting error: no space to make copy, no display filters used"), sizeof(err_string));
      err_string[sizeof(err_string)-1] = '\0';
    }

    if((status = gf_pipe(FETCH_READC, detach_so ? detach_writec : pc)) != NULL) {
        snprintf(err_string, sizeof(err_string), "Formatting error: %s", status);
        rv = 0L;
    }

    /*
     * If we wrote to a temporary area, there MAY be a user-defined
     * filter to invoke.  Filter it it (or not if no trigger match)
     * *AND* send the output thru any auxiliary filters, destroy the
     * temporary object and be done with it...
     */
    if(detach_so){
        if(!err_string[0] && display_filter && *display_filter){
            FILTLIST_S *p, *aux = NULL;
            size_t      count;

            if(aux_filters && !(flags & DT_BINARY)){
                /* insert NL conversion filters around remaining aux_filters
                 * so they're not tripped up by local NL convention
                 */
                for(p = aux_filters; p->filter; p++)    /* count aux_filters */
                  ;

                count = (p - aux_filters) + 3;
                p = aux = (FILTLIST_S *) fs_get(count * sizeof(FILTLIST_S));
                memset(p, 0, count * sizeof(FILTLIST_S));
                p->filter = gf_local_nvtnl;
                p++;
                for(; aux_filters->filter; p++, aux_filters++)
                  *p = *aux_filters;

                p->filter = gf_nvtnl_local;
            }

            if((status = (*ps_global->tools.display_filter)(display_filter, detach_so, pc, aux)) != NULL){
                snprintf(err_string, sizeof(err_string), "Formatting error: %s", status);
                rv = 0L;
            }

            if(aux)
              fs_give((void **)&aux);
        }
        else{                                   /*  just copy it, then */
            gf_io_t        gc;

            gf_set_so_readc(&gc, detach_so);
            so_seek(detach_so, 0L, 0);
            gf_filter_init();
            if(aux_filters){
                /* if other filters are involved, correct for
                 * newlines on either side of the pipe...
                 */
                gf_link_filter(gf_local_nvtnl, NULL);
                for( ; aux_filters->filter ; aux_filters++)
                  gf_link_filter(aux_filters->filter, aux_filters->data);

                if(!(flags & DT_BINARY))
                  gf_link_filter(gf_nvtnl_local, NULL);
            }

            if((status = gf_pipe(gc, pc)) != NULL){     /* Second pass, sheesh */
                snprintf(err_string, sizeof(err_string), "Formatting error: %s", status);
                rv = 0L;
            }

            gf_clear_so_readc(detach_so);
        }

        so_give(&detach_so);                    /* blast temp copy */
    }

    if(!ps_global->print && we_cancel)
      cancel_busy_cue(0);

    if (len)
      *len = rv;

    if(df_trigger_list)
      blast_trigger_list(&df_trigger_list);

    return((err_string[0] == '\0') ? NULL : err_string);
}


int
detach_writec(int c)
{
    return(so_writec(c, detach_so));
}


/*
 * build_trigger_list - return possible triggers in a list of triggers 
 *                      structs
 */
TRGR_S *
build_trigger_list(void)
{
    TRGR_S  *tp = NULL, **trailp;
    char   **l, *test, *str, *ep, *cmd = NULL;
    int      i;

    trailp = &tp;
    for(l = ps_global->VAR_DISPLAY_FILTERS ; l && *l; l++){
        get_pair(*l, &test, &cmd, 1, 1);
        if(test && valid_filter_command(&cmd)){
            *trailp       = (TRGR_S *) fs_get(sizeof(TRGR_S));
            (*trailp)->cmp = df_trigger_cmp_text;
            str            = test;
            if(*test == '_' && (i = strlen(test)) > 10
               && *(ep = &test[i-1]) == '_' && *--ep == ')'){
                if(struncmp(test, "_CHARSET(", 9) == 0){
                    fs_give((void **)&test);
                    fs_give((void **)&cmd);
                    fs_give((void **)trailp);
                    continue;
                }

                if(strncmp(test+1, "LEADING(", 8) == 0){
                    (*trailp)->cmp = df_trigger_cmp_lwsp;
                    *ep            = '\0';
                    str            = cpystr(test+9);
                    fs_give((void **)&test);
                }
                else if(strncmp(test+1, "BEGINNING(", 10) == 0){
                    (*trailp)->cmp = df_trigger_cmp_start;
                    *ep            = '\0';
                    str            = cpystr(test+11);
                    fs_give((void **)&test);
                }
            }

            (*trailp)->text = str;
            (*trailp)->cmd = cmd;
            *(trailp = &(*trailp)->next) = NULL;
        }
        else{
            fs_give((void **)&test);
            fs_give((void **)&cmd);
        }
    }

    return(tp);
}


/*
 * blast_trigger_list - zot any list of triggers we've been using 
 */
void
blast_trigger_list(TRGR_S **tlist)
{
    if((*tlist)->next)
      blast_trigger_list(&(*tlist)->next);

    fs_give((void **)&(*tlist)->text);
    fs_give((void **)&(*tlist)->cmd);
    fs_give((void **)tlist);
}


/*
 * df_trigger_cmp - compare the line passed us with the list of defined
 *                  display filter triggers
 */
int
df_trigger_cmp(long int n, char *s, LT_INS_S **e, void *l)
{
    register TRGR_S *tp;
    int              result;

    if(!display_filter)                         /* already found? */
      for(tp = df_trigger_list; tp; tp = tp->next)
        if(tp->cmp){
            if((result = (*tp->cmp)(s, tp->text)) < 0)
              tp->cmp = NULL;
            else if(result > 0)
              return(((display_filter = tp->cmd) != NULL) ? 1 : 0);
        }

    return(0);
}


/*
 * df_trigger_cmp_text - return 1 if s1 is in s2
 */
int
df_trigger_cmp_text(char *s1, char *s2)
{
    return(strstr(s1, s2) != NULL);
}


/*
 * df_trigger_cmp_lwsp - compare the line passed us with the list of defined
 *                       display filter triggers. returns:
 *
 *                  0  if we don't know yet
 *                  1  if we match
 *                 -1  if we clearly don't match
 */
int
df_trigger_cmp_lwsp(char *s1, char *s2)
{
    while(*s1 && isspace((unsigned char)*s1))
      s1++;

    return((*s1) ? (!strncmp(s1, s2, strlen(s2)) ? 1 : -1) : 0);
}


/*
 * df_trigger_cmp_start - return 1 if first strlen(s2) chars start s1
 */
int
df_trigger_cmp_start(char *s1, char *s2)
{
    return(!strncmp(s1, s2, strlen(s2)));
}


/*
 * valid_filter_command - make sure argv[0] of command really exists.
 *                    "cmd" is required to be an alloc'd string since
 *                    it will get realloc'd if the command's path is
 *                    expanded.
 */
int
valid_filter_command(char **cmd)
{
    int  i;
    char cpath[MAXPATH+1], *p;

    if(!(cmd && *cmd))
      return(FALSE);

    /*
     * copy cmd to build expanded path if necessary.
     */
    for(i = 0; i < sizeof(cpath) && (cpath[i] = (*cmd)[i]); i++)
      if(isspace((unsigned char)(*cmd)[i])){
          cpath[i] = '\0';              /* tie off command's path*/
          break;
      }

#if     defined(DOS) || defined(OS2)
    if(is_absolute_path(cpath)){
        size_t l;

        fixpath(cpath, sizeof(cpath));
        l = strlen(cpath) + strlen(&(*cmd)[i]);
        p = (char *) fs_get((l+1) * sizeof(char));
        strncpy(p, cpath, l);           /* copy new path */
        p[l] = '\0';
        strncat(p, &(*cmd)[i], l+1-1-strlen(p));                /* and old args */
        p[l] = '\0';
        fs_give((void **) cmd);         /* free it */
        *cmd = p;                       /* and assign new buf */
    }
#else
    if(cpath[0] == '~'){
        if(fnexpand(cpath, sizeof(cpath))){
            size_t l;

            l = strlen(cpath) + strlen(&(*cmd)[i]);
            p = (char *) fs_get((l+1) * sizeof(char));
            strncpy(p, cpath, l);               /* copy new path */
            p[l] = '\0';
            strncat(p, &(*cmd)[i], l+1-1-strlen(p));            /* and old args */
            p[l] = '\0';
            fs_give((void **) cmd);     /* free it */
            *cmd = p;                   /* and assign new buf */
        }
        else
          return(FALSE);
    }
#endif

    return(is_absolute_path(cpath) && can_access(cpath, EXECUTE_ACCESS) == 0);
}


void
fetch_readc_init(FETCH_READC_S *frd, MAILSTREAM *stream, long int msgno,
                 char *section, unsigned long size, long partial, long int flags)
{
    int nointr = 0;

    nointr = flags & DT_NOINTR;
    flags &= ~DT_NOINTR;

    memset(g_fr_desc = frd, 0, sizeof(FETCH_READC_S));
    frd->stream  = stream;
    frd->msgno   = msgno;
    frd->section = section;
    frd->flags   = flags;
    frd->size    = size;
    frd->readc   = fetch_readc;

#ifdef SMIME
    /*
     * The call to imap_cache below will return true in the case where
     * we've already stashed fake data in the content of the part.
     * This happens when an S/MIME message is decrypted.
     */
#endif

    if(modern_imap_stream(stream)
       && !imap_cache(stream, msgno, section, NULL, NULL)
       && (size > INIT_FETCH_CHUNK || (partial > 0L && partial < size))
       && (F_OFF(F_QUELL_PARTIAL_FETCH, ps_global)
           ||
#ifdef  _WINDOWS
           F_ON(F_QUELL_SSL_LARGEBLOCKS, ps_global)
#else
           0
#endif
           )){

        if(partial > 0L && partial < size){
            /* partial fetch is being asked for */
            frd->size = partial;
        }

        frd->allocsize = MIN(INIT_FETCH_CHUNK,frd->size);
        frd->chunk = (char *) fs_get ((frd->allocsize + 1) * sizeof(char));
        frd->chunksize = frd->allocsize/2;  /* this gets doubled 1st time */
        frd->endp  = frd->chunk;
        frd->free_me = 1;

        if(!nointr)
          if(intr_handling_on())
            frd->we_turned_on = 1;

        if(!(partial > 0L && partial < size)){
            frd->cache = so_get(CharStar, NULL, EDIT_ACCESS);
            so_truncate(frd->cache, size);              /* pre-allocate */
        }
    }
    else{                               /* fetch the whole bloody thing here */
        frd->chunk = mail_fetch_body(stream, msgno, section, &frd->read, flags);

        /* This only happens if the server gave us a bogus size */
        if(partial > 0L && partial < size){
            /* partial fetch is being asked for */
            frd->size = partial;
            frd->endp  = &frd->chunk[frd->size];
        }
        else if(size != frd->read){
            dprint((1,
          "fetch_readc_init: size mismatch: size=%lu read=%lu, continue...\n",
                   frd->size, frd->read));
            q_status_message(SM_ORDER | SM_DING, 0, 3,
                 _("Message size does not match expected size, continuing..."));
            frd->size = MIN(size, frd->read);
            frd->endp  = &frd->chunk[frd->read];
        }
        else
          frd->endp  = &frd->chunk[frd->read];
    }

    frd->chunkp = frd->chunk;
}


int
fetch_readc_cleanup(int store)
{
    if(g_fr_desc){
        if(g_fr_desc->we_turned_on)
          intr_handling_off();

        if(g_fr_desc->chunk && g_fr_desc->free_me)
          fs_give((void **) &g_fr_desc->chunk);

        if(g_fr_desc->cache && store){
            SIZEDTEXT text;

            text.size = g_fr_desc->size;
            text.data = (unsigned char *) so_text(g_fr_desc->cache);
            imap_cache(g_fr_desc->stream, g_fr_desc->msgno,
                       g_fr_desc->section, NULL, &text);
            g_fr_desc->cache->txt = (void *) NULL;
            so_give(&g_fr_desc->cache);
        }
    }

    return(0);
}


char *
fetch_gets(readfn_t f, void *stream, long unsigned int size, GETS_DATA *md)
{
    unsigned long n;

    n                = MIN(g_fr_desc->chunksize, size);
    g_fr_desc->read += n;
    g_fr_desc->endp  = &g_fr_desc->chunk[n];

    (*f) (stream, n, g_fr_desc->chunkp = g_fr_desc->chunk);

    if(g_fr_desc->cache)
      so_nputs(g_fr_desc->cache, g_fr_desc->chunk, (long) n);

    /* BUG: need to read requested "size" in case it's larger than chunk? */

    return(NULL);
}


int
fetch_readc(unsigned char *c)
{
    extern void gf_error(char *);

    if(ps_global->intr_pending){
        (void) fetch_readc_cleanup(0);
        /* TRANSLATORS: data transfer was interrupted by something */
        gf_error(g_fr_desc->error ? g_fr_desc->error :_("Transfer interrupted!"));
        /* no return */
    }
    else if(g_fr_desc->chunkp == g_fr_desc->endp){

        /* Anything to read, do it */
        if(g_fr_desc->read < g_fr_desc->size){
            void *old_gets;
            int   rv;
            TIMEVAL_S before, after;
            long diff, wdiff;
            unsigned long save_read;

            old_gets = mail_parameters(g_fr_desc->stream, GET_GETS,
                                       (void *)NULL);
            mail_parameters(g_fr_desc->stream, SET_GETS, (void *) fetch_gets);

            /*
             * Adjust chunksize with the goal that it will be about
             * TARGET_INTR_TIME useconds +- 20%
             * to finish the partial fetch. We want that time
             * to be small so that interrupts will happen fast, but we want
             * the chunksize large so that the whole fetch will happen
             * fast. So it's a tradeoff between those two things.
             *
             * If the estimated fetchtime is getting too large, we
             * half the chunksize. If it is small, we double
             * the chunksize. If it is in between, we leave it. There is
             * some risk of oscillating between two values, but who cares?
             */
            if(g_fr_desc->fetchtime <
                                    TARGET_INTR_TIME - TARGET_INTR_TIME/5)
              g_fr_desc->chunksize *= 2;
            else if(g_fr_desc->fetchtime >
                                    TARGET_INTR_TIME + TARGET_INTR_TIME/5)
              g_fr_desc->chunksize /= 2;

            g_fr_desc->chunksize = MIN(MAX_FETCH_CHUNK,
                                       MAX(MIN_FETCH_CHUNK,
                                           g_fr_desc->chunksize));
            
#ifdef  _WINDOWS
            /*
             * If this feature is set, limit the max size to less than
             * 16K - 5, the magic number that avoids Microsoft's bug.
             * Let's just go with 12K instead of 16K - 5.
             */
            if(F_ON(F_QUELL_SSL_LARGEBLOCKS, ps_global))
              g_fr_desc->chunksize =
                  MIN(AVOID_MICROSOFT_SSL_CHUNKING_BUG, g_fr_desc->chunksize);
#endif

            /* don't ask for more than there should be left to ask for */
            g_fr_desc->chunksize =
                MIN(g_fr_desc->size - g_fr_desc->read, g_fr_desc->chunksize);

            /*
             * If chunksize grew, reallocate chunk.
             */
            if(g_fr_desc->chunksize > g_fr_desc->allocsize){
                g_fr_desc->allocsize = g_fr_desc->chunksize;
                fs_give((void **) &g_fr_desc->chunk);
                g_fr_desc->chunk = (char *) fs_get ((g_fr_desc->allocsize + 1)
                                                                * sizeof(char));
                g_fr_desc->endp   = g_fr_desc->chunk;
                g_fr_desc->chunkp = g_fr_desc->chunk;
            }

            save_read = g_fr_desc->read;
            (void)get_time(&before);

            rv = mail_partial_body(g_fr_desc->stream, g_fr_desc->msgno,
                                   g_fr_desc->section, g_fr_desc->read,
                                   g_fr_desc->chunksize, g_fr_desc->flags);

            /*
             * If the amount we actually read is less than the amount we
             * asked for we assume that is because the server gave us a
             * bogus size when we originally asked for it.
             */
            if(g_fr_desc->chunksize > (g_fr_desc->read - save_read)){
                dprint((1,
  "partial_body returned less than asked for: asked=%lu got=%lu, continue...\n",
                       g_fr_desc->chunksize, g_fr_desc->read - save_read));
                if(g_fr_desc->read - save_read > 0)
                  q_status_message(SM_ORDER | SM_DING, 0, 3,
                   _("Message size does not match expected size, continuing..."));
                else{
                    rv = 0;
                    q_status_message(SM_ORDER | SM_DING, 3, 3,
                     _("Server returns zero bytes, Quell-Partial-Fetch feature may help"));
                }

                g_fr_desc->size = g_fr_desc->read;
            }

            if(get_time(&after) == 0){
                diff = time_diff(&after, &before);
                wdiff = MIN(TARGET_INTR_TIME + TARGET_INTR_TIME/2,
                            MAX(TARGET_INTR_TIME - TARGET_INTR_TIME/2, diff));
                /*
                 * Fetchtime is an exponentially weighted average of the number
                 * of usecs it takes to do a single fetch of whatever the
                 * current chunksize is. Since the fetch time probably isn't
                 * simply proportional to the chunksize, we don't try to
                 * calculate a chunksize by keeping track of the bytes per
                 * second. Instead, we just double or half the chunksize if
                 * we are too fast or too slow. That happens the next time
                 * through the loop a few lines up.
                 * Too settle it down a bit, Windsorize the mean.
                 */
                g_fr_desc->fetchtime = (g_fr_desc->fetchtime == 0)
                                        ? wdiff
                                        : g_fr_desc->fetchtime/2 + wdiff/2;
                dprint((8,
                 "fetch: diff=%ld wdiff=%ld fetchave=%ld prev chunksize=%ld\n",
                 diff, wdiff, g_fr_desc->fetchtime, g_fr_desc->chunksize));
            }
            else  /* just set it so it won't affect anything */
              g_fr_desc->fetchtime = TARGET_INTR_TIME;

            /* UNinstall mailgets */
            mail_parameters(g_fr_desc->stream, SET_GETS, old_gets);

            if(!rv){
                (void) fetch_readc_cleanup(0);
                gf_error("Partial fetch failed!");
                /* no return */
            }
        }
        else                            /* clean up and return done. */
          return(fetch_readc_cleanup(1));
    }

    *c = *g_fr_desc->chunkp++;

    return(1);
}