Make combinetime() overflow safe (Vincent Lefevre)..

[s-mailx.git] / shexp.c

/*@ S-nail - a mail user agent derived from Berkeley Mail.
 *@ Shell "word", file- and other name expansions, incl. file globbing.
 *@ TODO v15: peek signal states while opendir/readdir/etc.
 *
 * Copyright (c) 2000-2004 Gunnar Ritter, Freiburg i. Br., Germany.
 * Copyright (c) 2012 - 2016 Steffen (Daode) Nurpmeso <steffen@sdaoden.eu>.
 */
/*
 * Copyright (c) 1980, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
#undef n_FILE
#define n_FILE shexp

#ifndef HAVE_AMALGAMATION
# include "nail.h"
#endif

#include <sys/wait.h>

#include <pwd.h>

#ifdef HAVE_FNMATCH
# include <dirent.h>
# include <fnmatch.h>
#endif

/* POSIX says
 *   Environment variable names used by the utilities in the Shell and
 *   Utilities volume of POSIX.1-2008 consist solely of uppercase
 *   letters, digits, and the <underscore> ('_') from the characters
 *   defined in Portable Character Set and do not begin with a digit.
 *   Other characters may be permitted by an implementation;
 *   applications shall tolerate the presence of such names.
 * We do support the hyphen "-" because it is common for mailx. */
#define a_SHEXP_ISVARC(C) (alnumchar(C) || (C) == '_' || (C) == '-')

enum a_shexp_quote_flags{
   a_SHEXP_QUOTE_NONE,
   a_SHEXP_QUOTE_ROUNDTRIP = 1u<<0, /* Result won't be consumed immediately */

   a_SHEXP_QUOTE_T_REVSOL = 1u<<8,  /* Type: by reverse solidus */
   a_SHEXP_QUOTE_T_SINGLE = 1u<<9,  /* Type: single-quotes */
   a_SHEXP_QUOTE_T_DOUBLE = 1u<<10, /* Type: double-quotes */
   a_SHEXP_QUOTE_T_DOLLAR = 1u<<11, /* Type: dollar-single-quotes */
   a_SHEXP_QUOTE_T_MASK = a_SHEXP_QUOTE_T_REVSOL | a_SHEXP_QUOTE_T_SINGLE |
         a_SHEXP_QUOTE_T_DOUBLE | a_SHEXP_QUOTE_T_DOLLAR,

   a_SHEXP_QUOTE__FREESHIFT = 16u
};

struct a_shexp_var_stack {
   struct a_shexp_var_stack *svs_next; /* Outer stack frame */
   char const *svs_value;  /* Remaining value to expand */
   size_t svs_len;         /* gth of .svs_dat this level */
   char const *svs_dat;    /* Result data of this level */
   bool_t svs_bsesc;       /* Shall backslash escaping be performed */
   ui8_t svs__dummy[7];
};

#ifdef HAVE_FNMATCH
struct a_shexp_glob_ctx{
   char const *sgc_patdat;       /* Remaining pattern (at and below level) */
   size_t sgc_patlen;
   struct n_string *sgc_outer;   /* Resolved path up to this level */
   ui32_t sgc_flags;
   ui8_t sgc__dummy[4];
};
#endif

struct a_shexp_quote_ctx{
   struct n_string *sqc_store;         /* Result storage */
   struct str sqc_input;               /* Input data, topmost level */
   ui32_t sqc_cnt_revso;
   ui32_t sqc_cnt_single;
   ui32_t sqc_cnt_double;
   ui32_t sqc_cnt_dollar;
   enum a_shexp_quote_flags sqc_flags;
   ui8_t sqc__dummy[4];
};

struct a_shexp_quote_lvl{
   struct a_shexp_quote_lvl *sql_link; /* Outer level */
   struct str sql_dat;                 /* This level (has to) handle(d) */
   enum a_shexp_quote_flags sql_flags;
   ui8_t sql__dummy[4];
};

/* Locate the user's mailbox file (where new, unread mail is queued) */
static char *a_shexp_findmail(char const *user, bool_t force);

/* Expand ^~/? and ^~USER/? constructs.
 * Returns the completely resolved (maybe empty or identical to input)
 * salloc()ed string */
static char *a_shexp_tilde(char const *s);

/* (Try to) Expand any shell variable in s.
 * Returns the completely resolved (maybe empty) salloc()ed string.
 * Logs on error */
static char *a_shexp_var(struct a_shexp_var_stack *svsp);

/* Perform fnmatch(3).  May return NULL on error */
static char *a_shexp_globname(char const *name, enum fexp_mode fexpm);
#ifdef HAVE_FNMATCH
static bool_t a_shexp__glob(struct a_shexp_glob_ctx *sgcp,
               struct n_strlist **slpp);
static int a_shexp__globsort(void const *cvpa, void const *cvpb);
#endif

/* Parse an input string and create a sh(1)ell-quoted result */
static void a_shexp__quote(struct a_shexp_quote_ctx *sqcp,
               struct a_shexp_quote_lvl *sqlp);

static char *
a_shexp_findmail(char const *user, bool_t force){
   char *rv;
   char const *cp;
   NYD2_ENTER;

   if(!force){
      if((cp = ok_vlook(inbox)) != NULL && *cp != '\0'){
         /* Folder extra introduced to avoid % recursion loops */
         if((rv = fexpand(cp, FEXP_NSPECIAL | FEXP_NFOLDER | FEXP_NSHELL)
               ) != NULL)
            goto jleave;
         n_err(_("*inbox* expansion failed, using $MAIL / builtin: %s\n"), cp);
      }

      if((cp = ok_vlook(MAIL)) != NULL){
         rv = savestr(cp);
         goto jleave;
      }
   }

   /* C99 */{
      size_t ul, i;

      ul = strlen(user) +1;
      i = sizeof(VAL_MAIL) -1 + 1 + ul;

      rv = salloc(i);
      memcpy(rv, VAL_MAIL, i = sizeof(VAL_MAIL));
      rv[i] = '/';
      memcpy(&rv[++i], user, ul);
   }
jleave:
   NYD2_LEAVE;
   return rv;
}

static char *
a_shexp_tilde(char const *s){
   struct passwd *pwp;
   size_t nl, rl;
   char const *rp, *np;
   char *rv;
   NYD2_ENTER;

   if(*(rp = &s[1]) == '/' || *rp == '\0'){
      np = ok_vlook(HOME);
      rl = strlen(rp);
   }else{
      if((rp = strchr(np = rp, '/')) != NULL){
         nl = PTR2SIZE(rp - np);
         np = savestrbuf(np, nl);
         rl = strlen(rp);
      }else
         rl = 0;

      if((pwp = getpwnam(np)) == NULL){
         rv = savestr(s);
         goto jleave;
      }
      np = pwp->pw_dir;
   }

   nl = strlen(np);
   rv = salloc(nl + 1 + rl +1);
   memcpy(rv, np, nl);
   if(rl > 0){
      memcpy(rv + nl, rp, rl);
      nl += rl;
   }
   rv[nl] = '\0';
jleave:
   NYD2_LEAVE;
   return rv;
}

static char *
a_shexp_var(struct a_shexp_var_stack *svsp)
{
   struct a_shexp_var_stack next, *np, *tmp;
   char const *vp;
   char lc, c, *cp, *rv;
   size_t i;
   NYD2_ENTER;

   if (*(vp = svsp->svs_value) != '$') {
      bool_t bsesc = svsp->svs_bsesc;
      union {bool_t hadbs; char c;} u = {FAL0};

      svsp->svs_dat = vp;
      for (lc = '\0', i = 0; ((c = *vp) != '\0'); ++i, ++vp) {
         if (c == '$' && lc != '\\')
            break;
         if (!bsesc)
            continue;
         lc = (lc == '\\') ? (u.hadbs = TRU1, '\0') : c;
      }
      svsp->svs_len = i;

      if (u.hadbs) {
         svsp->svs_dat = cp = savestrbuf(svsp->svs_dat, i);

         for (lc = '\0', rv = cp; (u.c = *cp++) != '\0';) {
            if (u.c != '\\' || lc == '\\')
               *rv++ = u.c;
            lc = (lc == '\\') ? '\0' : u.c;
         }
         *rv = '\0';

         svsp->svs_len = PTR2SIZE(rv - svsp->svs_dat);
      }
   } else {
      if ((lc = (*++vp == '{')))
         ++vp;

      svsp->svs_dat = vp;
      for (i = 0; (c = *vp) != '\0'; ++i, ++vp)
         if (!a_SHEXP_ISVARC(c))
            break;

      if (lc) {
         if (c != '}') {
            n_err(_("Variable name misses closing }: %s\n"),
               svsp->svs_value);
            svsp->svs_len = strlen(svsp->svs_value);
            svsp->svs_dat = svsp->svs_value;
            goto junroll;
         }
         c = *++vp;
      }

      svsp->svs_len = i;
      /* Check getenv(3) shall no internal variable exist! */
      if ((rv = vok_vlook(cp = savestrbuf(svsp->svs_dat, i))) != NULL ||
            (rv = getenv(cp)) != NULL)
         svsp->svs_len = strlen(svsp->svs_dat = rv);
      else
         svsp->svs_len = 0, svsp->svs_dat = UNCONST("");
   }
   if (c != '\0')
      goto jrecurse;

   /* That level made the great and completed encoding.  Build result */
junroll:
   for (i = 0, np = svsp, svsp = NULL; np != NULL;) {
      i += np->svs_len;
      tmp = np->svs_next;
      np->svs_next = svsp;
      svsp = np;
      np = tmp;
   }

   cp = rv = salloc(i +1);
   while (svsp != NULL) {
      np = svsp;
      svsp = svsp->svs_next;
      memcpy(cp, np->svs_dat, np->svs_len);
      cp += np->svs_len;
   }
   *cp = '\0';

jleave:
   NYD2_LEAVE;
   return rv;
jrecurse:
   memset(&next, 0, sizeof next);
   next.svs_next = svsp;
   next.svs_value = vp;
   next.svs_bsesc = svsp->svs_bsesc;
   rv = a_shexp_var(&next);
   goto jleave;
}

static char *
a_shexp_globname(char const *name, enum fexp_mode fexpm){
#ifdef HAVE_FNMATCH
   struct a_shexp_glob_ctx sgc;
   struct n_string outer;
   struct n_strlist *slp;
   char *cp;
   NYD_ENTER;

   memset(&sgc, 0, sizeof sgc);
   sgc.sgc_patlen = strlen(name);
   sgc.sgc_patdat = savestrbuf(name, sgc.sgc_patlen);
   sgc.sgc_outer = n_string_reserve(n_string_creat(&outer), sgc.sgc_patlen);
   sgc.sgc_flags = ((fexpm & FEXP_SILENT) != 0);
   slp = NULL;
   if(a_shexp__glob(&sgc, &slp))
      cp = (char*)1;
   else
      cp = NULL;
   n_string_gut(&outer);

   if(cp == NULL)
      goto jleave;

   if(slp == NULL){
      cp = UNCONST(N_("File pattern does not match"));
      goto jerr;
   }else if(slp->sl_next == NULL)
      cp = savestrbuf(slp->sl_dat, slp->sl_len);
   else if(fexpm & FEXP_MULTIOK){
      struct n_strlist **sorta, *xslp;
      size_t i, no, l;

      no = l = 0;
      for(xslp = slp; xslp != NULL; xslp = xslp->sl_next){
         ++no;
         l += xslp->sl_len + 1;
      }

      sorta = smalloc(sizeof(*sorta) * no);
      no = 0;
      for(xslp = slp; xslp != NULL; xslp = xslp->sl_next)
         sorta[no++] = xslp;
      qsort(sorta, no, sizeof *sorta, &a_shexp__globsort);

      cp = salloc(++l);
      l = 0;
      for(i = 0; i < no; ++i){
         xslp = sorta[i];
         memcpy(&cp[l], xslp->sl_dat, xslp->sl_len);
         l += xslp->sl_len;
         cp[l++] = '\0';
      }
      cp[l] = '\0';

      free(sorta);
      pstate |= PS_EXPAND_MULTIRESULT;
   }else{
      cp = UNCONST(N_("File pattern matches multiple results"));
      goto jerr;
   }

jleave:
   while(slp != NULL){
      struct n_strlist *tmp = slp;

      slp = slp->sl_next;
      free(tmp);
   }
   NYD_LEAVE;
   return cp;

jerr:
   if(!(fexpm & FEXP_SILENT)){
      name = n_shexp_quote_cp(name, FAL0);
      n_err("%s: %s\n", V_(cp), name);
   }
   cp = NULL;
   goto jleave;

#else /* HAVE_FNMATCH */
   UNUSED(fexpm);

   if(!(fexpm & FEXP_SILENT))
      n_err(_("No filename pattern (fnmatch(3)) support compiled in\n"));
   return savestr(name);
#endif
}

#ifdef HAVE_FNMATCH
static bool_t
a_shexp__glob(struct a_shexp_glob_ctx *sgcp, struct n_strlist **slpp){
   enum{a_SILENT = 1<<0, a_DEEP=1<<1, a_SALLOC=1<<2};

   struct a_shexp_glob_ctx nsgc;
   struct dirent *dep;
   DIR *dp;
   size_t old_outerlen;
   char const *ccp, *myp;
   NYD2_ENTER;

   /* We need some special treatment for the outermost level */
   if(!(sgcp->sgc_flags & a_DEEP)){
      if(sgcp->sgc_patlen > 0 && sgcp->sgc_patdat[0] == '/'){
         myp = n_string_cp(n_string_push_c(sgcp->sgc_outer, '/'));
         ++sgcp->sgc_patdat;
         --sgcp->sgc_patlen;
      }else
         myp = "./";
   }else
      myp = n_string_cp(sgcp->sgc_outer);
   old_outerlen = sgcp->sgc_outer->s_len;

   /* Separate current directory/pattern level from any possible remaining
    * pattern in order to be able to use it for fnmatch(3) */
   if((ccp = memchr(sgcp->sgc_patdat, '/', sgcp->sgc_patlen)) == NULL)
      nsgc.sgc_patlen = 0;
   else{
      nsgc = *sgcp;
      nsgc.sgc_flags |= a_DEEP;
      sgcp->sgc_patlen = PTR2SIZE((nsgc.sgc_patdat = &ccp[1]) -
            &sgcp->sgc_patdat[0]);
      nsgc.sgc_patlen -= sgcp->sgc_patlen;
      /* Trim solidus */
      if(sgcp->sgc_patlen > 0){
         assert(sgcp->sgc_patdat[sgcp->sgc_patlen -1] == '/');
         ((char*)UNCONST(sgcp->sgc_patdat))[--sgcp->sgc_patlen] = '\0';
      }
   }

   /* Our current directory level */
   /* xxx Plenty of room for optimizations, like quickshot lstat(2) which may
    * xxx be the (sole) result depending on pattern surroundings, etc. */
   if((dp = opendir(myp)) == NULL){
      int err;

      switch((err = errno)){
      case ENOTDIR:
         ccp = N_("cannot access paths under non-directory");
         goto jerr;
      case ENOENT:
         ccp = N_("path component of (sub)pattern non-existent");
         goto jerr;
      case EACCES:
         ccp = N_("file permission for file (sub)pattern denied");
         goto jerr;
      default:
         ccp = N_("cannot handle file (sub)pattern");
         goto jerr;
      }
   }

   /* As necessary, quote bytes in the current pattern */
   /* C99 */{
      char *ncp;
      size_t i;
      bool_t need;

      for(need = FAL0, i = 0, myp = sgcp->sgc_patdat; *myp != '\0'; ++myp)
         switch(*myp){
         case '\'': case '"': case '\\': case '$':
         case ' ': case '\t':
            need = TRU1;
            ++i;
            /* FALLTHRU */
         default:
            ++i;
            break;
         }

      if(need){
         ncp = salloc(i +1);
         for(i = 0, myp = sgcp->sgc_patdat; *myp != '\0'; ++myp)
            switch(*myp){
            case '\'': case '"': case '\\': case '$':
            case ' ': case '\t':
               ncp[i++] = '\\';
               /* FALLTHRU */
            default:
               ncp[i++] = *myp;
               break;
            }
         ncp[i] = '\0';
         myp = ncp;
      }else
         myp = sgcp->sgc_patdat;
   }

   while((dep = readdir(dp)) != NULL){
      switch(fnmatch(myp, dep->d_name, FNM_PATHNAME | FNM_PERIOD)){
      case 0:{
         /* A match expresses the desire to recurse if there is more pattern */
         if(nsgc.sgc_patlen > 0){
            bool_t isdir;

            n_string_push_cp((sgcp->sgc_outer->s_len > 1
                  ? n_string_push_c(sgcp->sgc_outer, '/') : sgcp->sgc_outer),
               dep->d_name);

            isdir = FAL0;
#ifdef HAVE_DIRENT_TYPE
            if(dep->d_type == DT_DIR)
               isdir = TRU1;
            else if(dep->d_type == DT_LNK || dep->d_type == DT_UNKNOWN)
#endif
            {
               struct stat sb;

               if(stat(n_string_cp(sgcp->sgc_outer), &sb)){
                  ccp = N_("I/O error when querying file status");
                  goto jerr;
               }else if(S_ISDIR(sb.st_mode))
                  isdir = TRU1;
            }

            /* TODO We recurse with current dir FD open, which could E[MN]FILE!
             * TODO Instead save away a list of such n_string's for later */
            if(isdir && !a_shexp__glob(&nsgc, slpp)){
               ccp = (char*)1;
               goto jleave;
            }

            n_string_trunc(sgcp->sgc_outer, old_outerlen);
         }else{
            struct n_strlist *slp;
            size_t i, j;

            i = strlen(dep->d_name);
            j = (old_outerlen > 0) ? old_outerlen + 1 + i : i;
            slp = n_STRLIST_MALLOC(j);
            *slpp = slp;
            slpp = &slp->sl_next;
            slp->sl_next = NULL;
            if((j = old_outerlen) > 0){
               memcpy(&slp->sl_dat[0], sgcp->sgc_outer->s_dat, j);
               if(slp->sl_dat[j -1] != '/')
                  slp->sl_dat[j++] = '/';
            }
            memcpy(&slp->sl_dat[j], dep->d_name, i);
            slp->sl_dat[j += i] = '\0';
            slp->sl_len = j;
         }
      }  break;
      case FNM_NOMATCH:
         break;
      default:
         ccp = N_("fnmatch(3) cannot handle file (sub)pattern");
         goto jerr;
      }
   }

   ccp = NULL;
jleave:
   if(dp != NULL)
      closedir(dp);
   NYD2_LEAVE;
   return (ccp == NULL);

jerr:
   if(!(sgcp->sgc_flags & a_SILENT)){
      char const *s2, *s3;

      if(sgcp->sgc_outer->s_len > 0){
         s2 = n_shexp_quote_cp(n_string_cp(sgcp->sgc_outer), FAL0);
         s3 = "/";
      }else
         s2 = s3 = "";

      n_err("%s: %s%s%s\n", V_(ccp), s2, s3,
         n_shexp_quote_cp(sgcp->sgc_patdat, FAL0));
   }
   goto jleave;
}

static int
a_shexp__globsort(void const *cvpa, void const *cvpb){
   int rv;
   struct n_strlist const * const *slpa, * const *slpb;
   NYD2_ENTER;

   slpa = cvpa;
   slpb = cvpb;
   rv = asccasecmp((*slpa)->sl_dat, (*slpb)->sl_dat);
   NYD2_LEAVE;
   return rv;
}
#endif /* HAVE_FNMATCH */

static void
a_shexp__quote(struct a_shexp_quote_ctx *sqcp, struct a_shexp_quote_lvl *sqlp){
   /* XXX Because of the problems caused by ISO C multibyte interface we cannot
    * XXX use the recursive implementation because of stateful encodings.
    * XXX I.e., if a quoted substring cannot be self-contained - the data after
    * XXX the quote relies on "the former state", then this doesn't make sense.
    * XXX Therefore this is not fully programmed out but instead only detects
    * XXX the "most fancy" quoting necessary, and directly does that.
    * XXX As a result of this, T_REVSOL and T_DOUBLE are not even considered.
    * XXX Otherwise we rather have to convert to wide first and act on that,
    * XXX e.g., call visual_info(n_VISUAL_INFO_WOUT_CREATE) on entire input */
#undef a_SHEXP_QUOTE_RECURSE /* XXX (Needs complete revisit, then) */
#ifdef a_SHEXP_QUOTE_RECURSE
# define jrecurse jrecurse
   struct a_shexp_quote_lvl sql;
#else
# define jrecurse jstep
#endif
   struct n_visual_info_ctx vic;
   union {struct a_shexp_quote_lvl *head; struct n_string *store;} u;
   ui32_t flags;
   size_t il;
   char const *ib;
   NYD2_ENTER;

   ib = sqlp->sql_dat.s;
   il = sqlp->sql_dat.l;
   flags = sqlp->sql_flags;

   /* Iterate over the entire input, classify characters and type of quotes
    * along the way.  Whenever a quote change has to be applied, adjust flags
    * for the new situation -, setup sql.* and recurse- */
   while(il > 0){
      char c;

      c = *ib;
      if(cntrlchar(c)){
         if(flags & a_SHEXP_QUOTE_T_DOLLAR)
            goto jstep;
         if(c == '\t' && (flags & (a_SHEXP_QUOTE_T_REVSOL |
               a_SHEXP_QUOTE_T_SINGLE | a_SHEXP_QUOTE_T_DOUBLE)))
            goto jstep;
#ifdef a_SHEXP_QUOTE_RECURSE
         ++sqcp->sqc_cnt_dollar;
#endif
         flags = (flags & ~a_SHEXP_QUOTE_T_MASK) | a_SHEXP_QUOTE_T_DOLLAR;
         goto jrecurse;
      }else if(blankspacechar(c) || c == '"' || c == '$'){
         if(flags & a_SHEXP_QUOTE_T_MASK)
            goto jstep;
#ifdef a_SHEXP_QUOTE_RECURSE
         ++sqcp->sqc_cnt_single;
#endif
         flags = (flags & ~a_SHEXP_QUOTE_T_MASK) | a_SHEXP_QUOTE_T_SINGLE;
         goto jrecurse;
      }else if(c == '\''){
         if(flags & (a_SHEXP_QUOTE_T_MASK & ~a_SHEXP_QUOTE_T_SINGLE))
            goto jstep;
#ifdef a_SHEXP_QUOTE_RECURSE
         ++sqcp->sqc_cnt_dollar;
#endif
         flags = (flags & ~a_SHEXP_QUOTE_T_MASK) | a_SHEXP_QUOTE_T_DOLLAR;
         goto jrecurse;
      }else if(c == '\\'){
         if(flags & a_SHEXP_QUOTE_T_MASK)
            goto jstep;
#ifdef a_SHEXP_QUOTE_RECURSE
         ++sqcp->sqc_cnt_single;
#endif
         flags = (flags & ~a_SHEXP_QUOTE_T_MASK) | a_SHEXP_QUOTE_T_SINGLE;
         goto jrecurse;
      }else if(!asciichar(c)){
         /* Need to keep together multibytes */
#ifdef a_SHEXP_QUOTE_RECURSE
         memset(&vic, 0, sizeof vic);
         vic.vic_indat = ib;
         vic.vic_inlen = il;
         n_visual_info(&vic,
            n_VISUAL_INFO_ONE_CHAR | n_VISUAL_INFO_SKIP_ERRORS);
#endif
         /* xxx check whether resulting \u would be ASCII */
         if(!(flags & a_SHEXP_QUOTE_ROUNDTRIP) ||
               (flags & a_SHEXP_QUOTE_T_DOLLAR)){
#ifdef a_SHEXP_QUOTE_RECURSE
            ib = vic.vic_oudat;
            il = vic.vic_oulen;
            continue;
#else
            goto jstep;
#endif
         }
#ifdef a_SHEXP_QUOTE_RECURSE
         ++sqcp->sqc_cnt_dollar;
#endif
         flags = (flags & ~a_SHEXP_QUOTE_T_MASK) | a_SHEXP_QUOTE_T_DOLLAR;
         goto jrecurse;
      }else
jstep:
         ++ib, --il;
   }
   sqlp->sql_flags = flags;

   /* Level made the great and completed processing input.  Reverse the list of
    * levels, detect the "most fancy" quote type needed along this way */
   /* XXX Due to restriction as above very crude */
   for(flags = 0, il = 0, u.head = NULL; sqlp != NULL;){
      struct a_shexp_quote_lvl *tmp;

      tmp = sqlp->sql_link;
      sqlp->sql_link = u.head;
      u.head = sqlp;
      il += sqlp->sql_dat.l;
      if(sqlp->sql_flags & a_SHEXP_QUOTE_T_MASK)
         il += (sqlp->sql_dat.l >> 1);
      flags |= sqlp->sql_flags;
      sqlp = tmp;
   }
   sqlp = u.head;

   /* Finally work the substrings in the correct order, adjusting quotes along
    * the way as necessary.  Start off with the "most fancy" quote, so that
    * the user sees an overall boundary she can orientate herself on.
    * We do it like that to be able to give the user some "encapsulation
    * experience", to address what strikes me is a problem of sh(1)ell quoting:
    * different to, e.g., perl(1), where you see at a glance where a string
    * starts and ends, sh(1) quoting occurs at the "top level", disrupting the
    * visual appearance of "a string" as such */
   u.store = n_string_reserve(sqcp->sqc_store, il);

   if(flags & a_SHEXP_QUOTE_T_DOLLAR){
      u.store = n_string_push_buf(u.store, "$'", sizeof("$'") -1);
      flags = (flags & ~a_SHEXP_QUOTE_T_MASK) | a_SHEXP_QUOTE_T_DOLLAR;
   }else if(flags & a_SHEXP_QUOTE_T_DOUBLE){
      u.store = n_string_push_c(u.store, '"');
      flags = (flags & ~a_SHEXP_QUOTE_T_MASK) | a_SHEXP_QUOTE_T_DOUBLE;
   }else if(flags & a_SHEXP_QUOTE_T_SINGLE){
      u.store = n_string_push_c(u.store, '\'');
      flags = (flags & ~a_SHEXP_QUOTE_T_MASK) | a_SHEXP_QUOTE_T_SINGLE;
   }else /*if(flags & a_SHEXP_QUOTE_T_REVSOL)*/
      flags &= ~a_SHEXP_QUOTE_T_MASK;

   /* Work all the levels */
   for(; sqlp != NULL; sqlp = sqlp->sql_link){
      /* As necessary update our mode of quoting */
#ifdef a_SHEXP_QUOTE_RECURSE
      il = 0;

      switch(sqlp->sql_flags & a_SHEXP_QUOTE_T_MASK){
      case a_SHEXP_QUOTE_T_DOLLAR:
         if(!(flags & a_SHEXP_QUOTE_T_DOLLAR))
            il = a_SHEXP_QUOTE_T_DOLLAR;
         break;
      case a_SHEXP_QUOTE_T_DOUBLE:
         if(!(flags & (a_SHEXP_QUOTE_T_DOUBLE | a_SHEXP_QUOTE_T_DOLLAR)))
            il = a_SHEXP_QUOTE_T_DOLLAR;
         break;
      case a_SHEXP_QUOTE_T_SINGLE:
         if(!(flags & (a_SHEXP_QUOTE_T_REVSOL | a_SHEXP_QUOTE_T_SINGLE |
               a_SHEXP_QUOTE_T_DOUBLE | a_SHEXP_QUOTE_T_DOLLAR)))
            il = a_SHEXP_QUOTE_T_SINGLE;
         break;
      default:
      case a_SHEXP_QUOTE_T_REVSOL:
         if(!(flags & (a_SHEXP_QUOTE_T_REVSOL | a_SHEXP_QUOTE_T_SINGLE |
               a_SHEXP_QUOTE_T_DOUBLE | a_SHEXP_QUOTE_T_DOLLAR)))
            il = a_SHEXP_QUOTE_T_REVSOL;
         break;
      }

      if(il != 0){
         if(flags & (a_SHEXP_QUOTE_T_SINGLE | a_SHEXP_QUOTE_T_DOLLAR))
            u.store = n_string_push_c(u.store, '\'');
         else if(flags & a_SHEXP_QUOTE_T_DOUBLE)
            u.store = n_string_push_c(u.store, '"');
         flags &= ~a_SHEXP_QUOTE_T_MASK;

         flags |= (ui32_t)il;
         if(flags & a_SHEXP_QUOTE_T_DOLLAR)
            u.store = n_string_push_buf(u.store, "$'", sizeof("$'") -1);
         else if(flags & a_SHEXP_QUOTE_T_DOUBLE)
            u.store = n_string_push_c(u.store, '"');
         else if(flags & a_SHEXP_QUOTE_T_SINGLE)
            u.store = n_string_push_c(u.store, '\'');
      }
#endif /* a_SHEXP_QUOTE_RECURSE */

      /* Work the level's substring */
      ib = sqlp->sql_dat.s;
      il = sqlp->sql_dat.l;

      while(il > 0){
         char c2, c;

         c = *ib;

         if(cntrlchar(c)){
            assert(c == '\t' || (flags & a_SHEXP_QUOTE_T_DOLLAR));
            assert((flags & (a_SHEXP_QUOTE_T_REVSOL | a_SHEXP_QUOTE_T_SINGLE |
               a_SHEXP_QUOTE_T_DOUBLE | a_SHEXP_QUOTE_T_DOLLAR)));
            switch((c2 = c)){
            case 0x07: c = 'a'; break;
            case 0x08: c = 'b'; break;
            case 0x0A: c = 'n'; break;
            case 0x0B: c = 'v'; break;
            case 0x0C: c = 'f'; break;
            case 0x0D: c = 'r'; break;
            case 0x1B: c = 'E'; break;
            default: break;
            case 0x09:
               if(flags & a_SHEXP_QUOTE_T_DOLLAR){
                  c = 't';
                  break;
               }
               if(flags & a_SHEXP_QUOTE_T_REVSOL)
                  u.store = n_string_push_c(u.store, '\\');
               goto jpush;
            }
            u.store = n_string_push_c(u.store, '\\');
            if(c == c2){
               u.store = n_string_push_c(u.store, 'c');
               c ^= 0x40;
            }
            goto jpush;
         }else if(blankspacechar(c) || c == '"' || c == '$'){
            if(flags & (a_SHEXP_QUOTE_T_SINGLE | a_SHEXP_QUOTE_T_DOLLAR))
               goto jpush;
            assert(flags & (a_SHEXP_QUOTE_T_REVSOL | a_SHEXP_QUOTE_T_DOUBLE));
            u.store = n_string_push_c(u.store, '\\');
            goto jpush;
         }else if(c == '\''){
            if(flags & a_SHEXP_QUOTE_T_DOUBLE)
               goto jpush;
            assert(!(flags & a_SHEXP_QUOTE_T_SINGLE));
            u.store = n_string_push_c(u.store, '\\');
            goto jpush;
         }else if(c == '\\'){
            if(flags & a_SHEXP_QUOTE_T_SINGLE)
               goto jpush;
            assert(flags & (a_SHEXP_QUOTE_T_REVSOL | a_SHEXP_QUOTE_T_DOUBLE |
               a_SHEXP_QUOTE_T_DOLLAR));
            u.store = n_string_push_c(u.store, '\\');
            goto jpush;
         }else if(asciichar(c)){
            /* Shorthand: we can simply push that thing out */
jpush:
            u.store = n_string_push_c(u.store, c);
            ++ib, --il;
         }else{
            /* Not an ASCII character, take care not to split up multibyte
             * sequences etc.  For the sake of compile testing, don't enwrap in
             * HAVE_ALWAYS_UNICODE_LOCALE || HAVE_NATCH_CHAR */
            if(options & OPT_UNICODE){
               ui32_t uc;
               char const *ib2;
               size_t il2, il3;

               ib2 = ib;
               il3 = il2 = il;
               if((uc = n_utf8_to_utf32(&ib2, &il2)) != UI32_MAX){
                  char itoa[32];
                  char const *cp;

                  il2 = PTR2SIZE(&ib2[0] - &ib[0]);
                  if((flags & a_SHEXP_QUOTE_ROUNDTRIP) || uc == 0xFFFDu){
                     /* Use padding to make ambiguities impossible */
                     il3 = snprintf(itoa, sizeof itoa, "\\%c%0*X",
                           (uc > 0xFFFFu ? 'U' : 'u'),
                           (int)(uc > 0xFFFFu ? 8 : 4), uc);
                     cp = itoa;
                  }else{
                     il3 = il2;
                     cp = &ib[0];
                  }
                  u.store = n_string_push_buf(u.store, cp, il3);
                  ib += il2, il -= il2;
                  continue;
               }
            }

            memset(&vic, 0, sizeof vic);
            vic.vic_indat = ib;
            vic.vic_inlen = il;
            n_visual_info(&vic,
               n_VISUAL_INFO_ONE_CHAR | n_VISUAL_INFO_SKIP_ERRORS);

            /* Work this substring as sensitive as possible */
            il -= vic.vic_oulen;
            if(!(flags & a_SHEXP_QUOTE_ROUNDTRIP))
               u.store = n_string_push_buf(u.store, ib, il);
#ifdef HAVE_ICONV
            else if((vic.vic_indat = n_iconv_onetime_cp(n_ICONV_NONE,
                  "utf-8", charset_get_lc(), savestrbuf(ib, il))) != NULL){
               ui32_t uc;
               char const *ib2;
               size_t il2, il3;

               il3 = il2 = strlen(ib2 = vic.vic_indat);
               if((uc = n_utf8_to_utf32(&ib2, &il2)) != UI32_MAX){
                  char itoa[32];

                  il2 = PTR2SIZE(&ib2[0] - &vic.vic_indat[0]);
                  /* Use padding to make ambiguities impossible */
                  il3 = snprintf(itoa, sizeof itoa, "\\%c%0*X",
                        (uc > 0xFFFFu ? 'U' : 'u'),
                        (int)(uc > 0xFFFFu ? 8 : 4), uc);
                  u.store = n_string_push_buf(u.store, itoa, il3);
               }else
                  goto Jxseq;
            }
#endif
            else
#ifdef HAVE_ICONV
                 Jxseq:
#endif
                        while(il-- > 0){
               u.store = n_string_push_buf(u.store, "\\xFF",
                     sizeof("\\xFF") -1);
               n_c_to_hex_base16(&u.store->s_dat[u.store->s_len - 2], *ib++);
            }

            ib = vic.vic_oudat;
            il = vic.vic_oulen;
         }
      }
   }

   /* Close an open quote */
   if(flags & (a_SHEXP_QUOTE_T_SINGLE | a_SHEXP_QUOTE_T_DOLLAR))
      u.store = n_string_push_c(u.store, '\'');
   else if(flags & a_SHEXP_QUOTE_T_DOUBLE)
      u.store = n_string_push_c(u.store, '"');
#ifdef a_SHEXP_QUOTE_RECURSE
jleave:
#endif
   NYD2_LEAVE;
   return;

#ifdef a_SHEXP_QUOTE_RECURSE
jrecurse:
   sqlp->sql_dat.l -= il;

   sql.sql_link = sqlp;
   sql.sql_dat.s = UNCONST(ib);
   sql.sql_dat.l = il;
   sql.sql_flags = flags;
   a_shexp__quote(sqcp, &sql);
   goto jleave;
#endif

#undef jrecurse
#undef a_SHEXP_QUOTE_RECURSE
}

FL char *
fexpand(char const *name, enum fexp_mode fexpm)
{
   struct str s;
   char const *cp, *res;
   bool_t dyn;
   NYD_ENTER;

   pstate &= ~PS_EXPAND_MULTIRESULT;

   /* The order of evaluation is "%" and "#" expand into constants.
    * "&" can expand into "+".  "+" can expand into shell meta characters.
    * Shell meta characters expand into constants.
    * This way, we make no recursive expansion */
   if ((fexpm & FEXP_NSHORTCUT) || (res = shortcut_expand(name)) == NULL)
      res = UNCONST(name);

   if(!(fexpm & FEXP_NSPECIAL)){
jnext:
      dyn = FAL0;
      switch (*res) {
      case '%':
         if(res[1] == ':' && res[2] != '\0')
            res = &res[2];
         else{
            bool_t force;

            force = (res[1] != '\0');
            res = a_shexp_findmail((force ? &res[1] : myname), force);
            if(force)
               goto jislocal;
         }
         goto jnext;
      case '#':
         if (res[1] != '\0')
            break;
         if (prevfile[0] == '\0') {
            n_err(_("No previous file\n"));
            res = NULL;
            goto jleave;
         }
         res = prevfile;
         goto jislocal;
      case '&':
         if (res[1] == '\0')
            res = ok_vlook(MBOX);
         break;
      }
   }

   /* POSIX: if *folder* unset or null, "+" shall be retained */
   if (!(fexpm & FEXP_NFOLDER) && *res == '+' &&
         *(cp = folder_query()) != '\0') {
      res = str_concat_csvl(&s, cp, &res[1], NULL)->s;
      dyn = TRU1;

      /* TODO *folder* can't start with %[:], can it!?! */
      if (res[0] == '%' && res[1] == ':') {
         res += 2;
         goto jnext;
      }
   }

   /* Do some meta expansions */
   if((fexpm & (FEXP_NSHELL | FEXP_NVAR)) != FEXP_NVAR &&
         ((fexpm & FEXP_NSHELL) ? (strchr(res, '$') != NULL)
          : anyof(res, "{}[]*?$"))){
      bool_t doexp;

      if(fexpm & FEXP_NOPROTO)
         doexp = TRU1;
      else switch(which_protocol(res)){
      case PROTO_FILE:
      case PROTO_MAILDIR:
         doexp = TRU1;
         break;
      default:
         doexp = FAL0;
         break;
      }

      if(doexp){
         struct a_shexp_var_stack top;

         memset(&top, 0, sizeof top);
         top.svs_value = res;
         top.svs_bsesc = TRU1;
         res = a_shexp_var(&top);

         if(res[0] == '~')
            res = a_shexp_tilde(res);

         if(!(fexpm & FEXP_NSHELL) &&
               (res = a_shexp_globname(res, fexpm)) == NULL)
            goto jleave;
         dyn = TRU1;
      }/* else no tilde */
   }else if(res[0] == '~'){
      res = a_shexp_tilde(res);
      dyn = TRU1;
   }

jislocal:
   if (fexpm & FEXP_LOCAL)
      switch (which_protocol(res)) {
      case PROTO_FILE:
      case PROTO_MAILDIR:
         break;
      default:
         n_err(_("Not a local file or directory: %s\n"),
            n_shexp_quote_cp(name, FAL0));
         res = NULL;
         break;
      }

jleave:
   if(res != NULL && !dyn)
      res = savestr(res);
   NYD_LEAVE;
   return UNCONST(res);
}

FL int
n_shexp_expand_escape(char const **s, bool_t use_nail_extensions)/* TODO DROP!*/
{
   char const *xs;
   int c, n;
   NYD2_ENTER;

   xs = *s;

   if ((c = *xs & 0xFF) == '\0')
      goto jleave;
   ++xs;
   if (c != '\\')
      goto jleave;

   switch ((c = *xs & 0xFF)) {
   case 'a':   c = '\a';         break;
   case 'b':   c = '\b';         break;
   case 'c':   c = PROMPT_STOP;  break;
   case 'f':   c = '\f';         break;
   case 'n':   c = '\n';         break;
   case 'r':   c = '\r';         break;
   case 't':   c = '\t';         break;
   case 'v':   c = '\v';         break;

   /* ESCape */
   case 'E':
   case 'e':
      c = '\033';
      break;

   /* Hexadecimal TODO uses ASCII */
   case 'X':
   case 'x': {
      static ui8_t const hexatoi[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
#undef a_HEX
#define a_HEX(n) \
   hexatoi[(ui8_t)((n) - ((n) <= '9' ? 48 : ((n) <= 'F' ? 55 : 87)))]

      c = 0;
      ++xs;
      if(hexchar(*xs))
         c = a_HEX(*xs);
      else{
         --xs;
         if(options & OPT_D_V)
            n_err(_("Invalid \\xNUMBER notation in: %s\n"), xs - 1);
         c = '\\';
         goto jleave;
      }
      ++xs;
      if(hexchar(*xs)){
         c <<= 4;
         c += a_HEX(*xs);
         ++xs;
      }
      goto jleave;
   }
#undef a_HEX

   /* octal, with optional 0 prefix */
   case '0':
      ++xs;
      if(0){
   default:
         if(*xs == '\0'){
            c = '\\';
            break;
         }
      }
      for (c = 0, n = 3; n-- > 0 && octalchar(*xs); ++xs) {
         c <<= 3;
         c |= *xs - '0';
      }
      goto jleave;

   /* S-nail extension for nice (get)prompt(()) support */
   case '&':
   case '?':
   case '$':
   case '@':
      if (use_nail_extensions) {
         switch (c) {
         case '&':   c = ok_blook(bsdcompat)       ? '&' : '?';   break;
         case '?':   c = (pstate & PS_EVAL_ERROR)  ? '1' : '0';   break;
         case '$':   c = PROMPT_DOLLAR;                           break;
         case '@':   c = PROMPT_AT;                               break;
         }
         break;
      }

      /* FALLTHRU */
   case '\0':
      /* A sole <backslash> at EOS is treated as-is! */
      c = '\\';
      /* FALLTHRU */
   case '\\':
      break;
   }

   ++xs;
jleave:
   *s = xs;
   NYD2_LEAVE;
   return c;
}

FL enum n_shexp_state
n_shexp_parse_token(struct n_string *store, struct str *input, /* TODO WCHAR */
      enum n_shexp_parse_flags flags){
   char utf[8];
   char c2, c, quotec;
   enum{
      a_NONE = 0,
      a_SKIPQ = 1<<0,   /* Skip rest of this quote (\c0 ..) */
      a_SURPLUS = 1<<1, /* Extended sequence interpretation */
      a_NTOKEN = 1<<2   /* "New token": e.g., comments are possible */
   } state;
   enum n_shexp_state rv;
   size_t i, il;
   char const *ib_save, *ib;
   NYD2_ENTER;
   UNINIT(c, '\0');

   assert((flags & n_SHEXP_PARSE_DRYRUN) || store != NULL);
   assert(input != NULL);
   assert(input->l == 0 || input->s != NULL);
   assert(!(flags & n_SHEXP_PARSE_LOG) || !(flags & n_SHEXP_PARSE_LOG_D_V));
   assert(!(flags & n_SHEXP_PARSE_IFS_ADD_COMMA) ||
      !(flags & n_SHEXP_PARSE_IFS_IS_COMMA));

   if((flags & n_SHEXP_PARSE_LOG_D_V) && (options & OPT_D_V))
      flags |= n_SHEXP_PARSE_LOG;

   if((flags & n_SHEXP_PARSE_TRUNC) && store != NULL)
      store = n_string_trunc(store, 0);

   ib = input->s;
   if((il = input->l) == UIZ_MAX)
      il = strlen(ib);

jrestart_empty:
   if(flags & n_SHEXP_PARSE_TRIMSPACE){
      for(; il > 0; ++ib, --il)
         if(!blankspacechar(*ib))
            break;
   }
   input->s = UNCONST(ib);
   input->l = il;

   if(il == 0){
      rv = n_SHEXP_STATE_STOP;
      goto jleave;
   }

   if(store != NULL)
      store = n_string_reserve(store, MIN(il, 32)); /* XXX */

   for(rv = n_SHEXP_STATE_NONE, state = a_NTOKEN, quotec = '\0'; il > 0;){
      --il, c = *ib++;

      /* If no quote-mode active.. */
      if(quotec == '\0'){
         if(c == '"' || c == '\''){
            quotec = c;
            if(c == '"')
               state |= a_SURPLUS;
            else
               state &= ~a_SURPLUS;
            state &= ~a_NTOKEN;
            continue;
         }else if(c == '$'){
            if(il > 0){
               state &= ~a_NTOKEN;
               if(*ib == '\''){
                  --il, ++ib;
                  quotec = '\'';
                  state |= a_SURPLUS;
                  continue;
               }else
                  goto J_var_expand;
            }
         }else if(c == '\\'){
            /* Outside of quotes this just escapes any next character, but a sole
             * <backslash> at EOS is left unchanged */
             if(il > 0)
               --il, c = *ib++;
            state &= ~a_NTOKEN;
         }else if(c == '#' && (state & a_NTOKEN)){
            rv |= n_SHEXP_STATE_STOP;
            goto jleave;
         }else if(c == ',' && (flags &
               (n_SHEXP_PARSE_IFS_ADD_COMMA | n_SHEXP_PARSE_IFS_IS_COMMA)))
            break;
         else if(blankchar(c)){
            if(!(flags & n_SHEXP_PARSE_IFS_IS_COMMA)){
               ++il, --ib;
               break;
            }
            state |= a_NTOKEN;
         }else
            state &= ~a_NTOKEN;
      }else{
         /* Quote-mode */
         assert(!(state & a_NTOKEN));
         if(c == quotec){
            state = a_NONE;
            quotec = '\0';
            /* Users may need to recognize the presence of empty quotes */
            rv |= n_SHEXP_STATE_OUTPUT;
            continue;
         }else if(c == '\\' && (state & a_SURPLUS)){
            ib_save = ib - 1;
            /* A sole <backslash> at EOS is treated as-is!  This is ok since
             * the "closing quote" error will occur next, anyway */
            if(il == 0)
               break;
            else if((c2 = *ib) == quotec){
               --il, ++ib;
               c = quotec;
            }else if(quotec == '"'){
               /* Double quotes:
                *    The <backslash> shall retain its special meaning as an
                *    escape character (see Section 2.2.1) only when followed
                *    by one of the following characters when considered
                *    special: $ ` " \ <newline> */
               switch(c2){
               case '$':
               case '`':
               /* case '"': already handled via c2 == quotec */
               case '\\':
                  --il, ++ib;
                  c = c2;
                  /* FALLTHRU */
               default:
                  break;
               }
            }else{
               /* Dollar-single-quote */
               --il, ++ib;
               switch(c2){
               case '"':
               /* case '\'': already handled via c2 == quotec */
               case '\\':
                  c = c2;
                  break;

               case 'b': c = '\b'; break;
               case 'f': c = '\f'; break;
               case 'n': c = '\n'; break;
               case 'r': c = '\r'; break;
               case 't': c = '\t'; break;
               case 'v': c = '\v'; break;

               case 'E':
               case 'e': c = '\033'; break;

               /* Control character */
               case 'c':
                  if(il == 0)
                     goto j_dollar_ungetc;
                  --il, c2 = *ib++;
                  if(state & a_SKIPQ)
                     continue;
                  c = upperconv(c2) ^ 0x40;
                  if((ui8_t)c > 0x1F && c != 0x7F){ /* ASCII C0: 0..1F, 7F */
                     if(flags & n_SHEXP_PARSE_LOG)
                        n_err(_("Invalid \\c notation: %.*s\n"),
                           (int)input->l, input->s);
                     rv |= n_SHEXP_STATE_ERR_CONTROL;
                  }
                  /* As an implementation-defined extension, support \c@
                   * EQ printf(1) alike \c */
                  if(c == '\0'){
                     rv |= n_SHEXP_STATE_STOP;
                     goto jleave;
                  }
                  break;

               /* Octal sequence: 1 to 3 octal bytes */
               case '0':
                  /* As an extension (dependent on where you look, echo(1), or
                   * awk(1)/tr(1) etc.), allow leading "0" octal indicator */
                  if(il > 0 && (c = *ib) >= '0' && c <= '7'){
                     c2 = c;
                     --il, ++ib;
                  }
                  /* FALLTHRU */
               case '1': case '2': case '3':
               case '4': case '5': case '6': case '7':
                  c2 -= '0';
                  if(il > 0 && (c = *ib) >= '0' && c <= '7'){
                     c2 = (c2 << 3) | (c - '0');
                     --il, ++ib;
                  }
                  if(il > 0 && (c = *ib) >= '0' && c <= '7'){
                     if((ui8_t)c2 > 0x1F){
                        if(flags & n_SHEXP_PARSE_LOG)
                           n_err(_("\\0 argument exceeds a byte: %.*s\n"),
                              (int)input->l, input->s);
                        rv |= n_SHEXP_STATE_ERR_NUMBER;
                        --il, ++ib;
                        /* Write unchanged */
je_ib_save:
                        rv |= n_SHEXP_STATE_OUTPUT;
                        if(!(flags & n_SHEXP_PARSE_DRYRUN))
                           store = n_string_push_buf(store, ib_save,
                                 PTR2SIZE(ib - ib_save));
                        continue;
                     }
                     c2 = (c2 << 3) | (c -= '0');
                     --il, ++ib;
                  }
                  if((c = c2) == '\0')
                     state |= a_SKIPQ;
                  if(state & a_SKIPQ)
                     continue;
                  break;

               /* ISO 10646 / Unicode sequence, 8 or 4 hexadecimal bytes */
               case 'U':
                  i = 8;
                  if(0){
                  /* FALLTHRU */
               case 'u':
                     i = 4;
                  }
                  if(il == 0)
                     goto j_dollar_ungetc;
                  if(0){
                     /* FALLTHRU */

               /* Hexadecimal sequence, 1 or 2 hexadecimal bytes */
               case 'X':
               case 'x':
                     if(il == 0)
                        goto j_dollar_ungetc;
                     i = 2;
                  }
                  /* C99 */{
                     static ui8_t const hexatoi[] = { /* XXX uses ASCII */
                        0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
                     };
                     size_t no, j;

                     i = MIN(il, i);
                     for(no = j = 0; i-- > 0; --il, ++ib, ++j){
                        c = *ib;
                        if(hexchar(c)){
                           no <<= 4;
                           no += hexatoi[(ui8_t)((c) - ((c) <= '9' ? 48
                                 : ((c) <= 'F' ? 55 : 87)))];
                        }else if(j == 0){
                           if(state & a_SKIPQ)
                              break;
                           c2 = (c2 == 'U' || c2 == 'u') ? 'u' : 'x';
                           if(flags & n_SHEXP_PARSE_LOG)
                              n_err(_("Invalid \\%c notation: %.*s\n"),
                                 c2, (int)input->l, input->s);
                           rv |= n_SHEXP_STATE_ERR_NUMBER;
                           goto je_ib_save;
                        }else
                           break;
                     }

                     /* Unicode massage */
                     if((c2 != 'U' && c2 != 'u') || n_uasciichar(no)){
                        if((c = (char)no) == '\0')
                           state |= a_SKIPQ;
                     }else if(no == 0)
                        state |= a_SKIPQ;
                     else if(!(state & a_SKIPQ)){
                        if(!(flags & n_SHEXP_PARSE_DRYRUN))
                           store = n_string_reserve(store, MAX(j, 4));

                        c2 = FAL0;
                        if(no > 0x10FFFF){ /* XXX magic; CText */
                           if(flags & n_SHEXP_PARSE_LOG)
                              n_err(_("\\U argument exceeds 0x10FFFF: %.*s\n"),
                                 (int)input->l, input->s);
                           rv |= n_SHEXP_STATE_ERR_NUMBER;
                           /* But normalize the output anyway */
                           goto Je_uni_norm;
                        }

                        j = n_utf32_to_utf8(no, utf);

                        if(options & OPT_UNICODE){
                           rv |= n_SHEXP_STATE_OUTPUT | n_SHEXP_STATE_UNICODE;
                           if(!(flags & n_SHEXP_PARSE_DRYRUN))
                              store = n_string_push_buf(store, utf, j);
                           continue;
                        }
#ifdef HAVE_ICONV
                        else{
                           char *icp;

                           icp = n_iconv_onetime_cp(n_ICONV_NONE,
                                 NULL, NULL, utf);
                           if(icp != NULL){
                              rv |= n_SHEXP_STATE_OUTPUT;
                              if(!(flags & n_SHEXP_PARSE_DRYRUN))
                                 store = n_string_push_cp(store, icp);
                              continue;
                           }
                        }
#endif
                        if(!(flags & n_SHEXP_PARSE_DRYRUN)) Je_uni_norm:{
                           char itoa[32];

                           rv |= n_SHEXP_STATE_OUTPUT |
                                 n_SHEXP_STATE_ERR_UNICODE;
                           i = snprintf(itoa, sizeof itoa, "\\%c%0*X",
                                 (no > 0xFFFFu ? 'U' : 'u'),
                                 (int)(no > 0xFFFFu ? 8 : 4), (ui32_t)no);
                           store = n_string_push_buf(store, itoa, i);
                        }
                        continue;
                     }
                     if(state & a_SKIPQ)
                        continue;
                  }
                  break;

               /* Extension: \$ can be used to expand a variable.
                * Bug|ad effect: if conversion fails, not written "as-is" */
               case '$':
                  if(il == 0)
                     goto j_dollar_ungetc;
                  goto J_var_expand;

               default:
j_dollar_ungetc:
                  /* Follow bash behaviour, print sequence unchanged */
                  ++il, --ib;
                  break;
               }
            }
         }else if(c == '$' && quotec == '"' && il > 0) J_var_expand:{
            bool_t brace;

            if(!(brace = (*ib == '{')) || il > 1){
               char const *cp, *vp;

               ib_save = ib - 1;
               il -= brace;
               vp = (ib += brace);

               for(i = 0; il > 0 && (c = *ib, a_SHEXP_ISVARC(c)); ++i)
                  --il, ++ib;

               if(brace){
                  if(il == 0 || *ib != '}'){
                     if(state & a_SKIPQ){
                        assert((state & a_SURPLUS) && quotec == '\'');
                        continue;
                     }
                     if(flags & n_SHEXP_PARSE_LOG)
                        n_err(_("Closing brace missing for ${VAR}: %.*s\n"),
                           (int)input->l, input->s);
                     rv |= n_SHEXP_STATE_ERR_QUOTEOPEN |
                           n_SHEXP_STATE_ERR_BRACE;
                     goto je_ib_save;
                  }
                  --il, ++ib;
               }

               if(state & a_SKIPQ)
                  continue;

               if(i == 0){
                  if(brace){
                     if(flags & n_SHEXP_PARSE_LOG)
                        n_err(_("Bad substitution (${}): %.*s\n"),
                           (int)input->l, input->s);
                     rv |= n_SHEXP_STATE_ERR_BADSUB;
                     goto je_ib_save;
                  }
                  c = '$';
               }else if(flags & n_SHEXP_PARSE_DRYRUN)
                  continue;
               else{
                  vp = savestrbuf(vp, i);
                  /* Check getenv(3) shall no internal variable exist! */
                  if((cp = vok_vlook(vp)) != NULL || (cp = getenv(vp)) != NULL){
                     rv |= n_SHEXP_STATE_OUTPUT;
                     store = n_string_push_cp(store, cp);
                     for(; (c = *cp) != '\0'; ++cp)
                        if(cntrlchar(c)){
                           rv |= n_SHEXP_STATE_CONTROL;
                           break;
                        }
                  }
                  continue;
               }
            }
         }else if(c == '`' && quotec == '"' && il > 0){ /* TODO shell command */
            continue;
         }
      }

      if(!(state & a_SKIPQ)){
         rv |= n_SHEXP_STATE_OUTPUT;
         if(cntrlchar(c))
            rv |= n_SHEXP_STATE_CONTROL;
         if(!(flags & n_SHEXP_PARSE_DRYRUN))
            store = n_string_push_c(store, c);
      }
   }

   if(quotec != '\0' && !(flags & n_SHEXP_PARSE_QUOTE_AUTOCLOSE)){
      if(flags & n_SHEXP_PARSE_LOG)
         n_err(_("no closing quote: %.*s\n"), (int)input->l, input->s);
      rv |= n_SHEXP_STATE_ERR_QUOTEOPEN;
   }

jleave:
   if((flags & n_SHEXP_PARSE_DRYRUN) && store != NULL){
      store = n_string_push_buf(store, input->s, PTR2SIZE(ib - input->s));
      rv |= n_SHEXP_STATE_OUTPUT;
   }

   if(flags & n_SHEXP_PARSE_TRIMSPACE){
      for(; il > 0; ++ib, --il)
         if(!blankchar(*ib))
            break;
   }
   input->l = il;
   input->s = UNCONST(ib);

   if(!(rv & n_SHEXP_STATE_STOP)){
      if(il > 0 && !(rv & n_SHEXP_STATE_OUTPUT) &&
            (flags & n_SHEXP_PARSE_IGNORE_EMPTY))
         goto jrestart_empty;
      if(!(rv & n_SHEXP_STATE_OUTPUT) && il == 0)
         rv |= n_SHEXP_STATE_STOP;
   }
   assert((rv & n_SHEXP_STATE_OUTPUT) || !(rv & n_SHEXP_STATE_UNICODE));
   assert((rv & n_SHEXP_STATE_OUTPUT) || !(rv & n_SHEXP_STATE_CONTROL));
   NYD2_LEAVE;
   return rv;
}

FL enum n_shexp_state
n_shexp_parse_token_buf(char **store, char const *indat, size_t inlen,
      enum n_shexp_parse_flags flags){
   struct n_string ss;
   struct str is;
   enum n_shexp_state shs;
   NYD2_ENTER;

   assert(store != NULL);
   assert(inlen == 0 || indat != NULL);

   n_string_creat_auto(&ss);
   is.s = UNCONST(indat);
   is.l = inlen;

   shs = n_shexp_parse_token(&ss, &is, flags);
   if(is.l > 0)
      shs &= ~n_SHEXP_STATE_STOP;
   else
      shs |= n_SHEXP_STATE_STOP;
   *store = n_string_cp(&ss);
   n_string_drop_ownership(&ss);

   n_string_gut(&ss);
   NYD2_LEAVE;
   return shs;
}

FL struct n_string *
n_shexp_quote(struct n_string *store, struct str const *input, bool_t rndtrip){
   struct a_shexp_quote_lvl sql;
   struct a_shexp_quote_ctx sqc;
   NYD2_ENTER;

   assert(store != NULL);
   assert(input != NULL);
   assert(input->l == 0 || input->s != NULL);

   memset(&sqc, 0, sizeof sqc);
   sqc.sqc_store = store;
   sqc.sqc_input.s = input->s;
   if((sqc.sqc_input.l = input->l) == UIZ_MAX)
      sqc.sqc_input.l = strlen(input->s);
   sqc.sqc_flags = rndtrip ? a_SHEXP_QUOTE_ROUNDTRIP : a_SHEXP_QUOTE_NONE;

   if(sqc.sqc_input.l == 0)
      store = n_string_push_buf(store, "''", sizeof("''") -1);
   else{
      memset(&sql, 0, sizeof sql);
      sql.sql_dat = sqc.sqc_input;
      sql.sql_flags = sqc.sqc_flags;
      a_shexp__quote(&sqc, &sql);
   }
   NYD2_LEAVE;
   return store;
}

FL char *
n_shexp_quote_cp(char const *cp, bool_t rndtrip){
   struct n_string store;
   struct str input;
   char *rv;
   NYD2_ENTER;

   assert(cp != NULL);

   input.s = UNCONST(cp);
   input.l = UIZ_MAX;
   rv = n_string_cp(n_shexp_quote(n_string_creat_auto(&store), &input,
         rndtrip));
   n_string_gut(n_string_drop_ownership(&store));
   NYD2_LEAVE;
   return rv;
}

/* s-it-mode */