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[luatex.git] / source / texk / web2c / luatexdir / tex / textoken.w

% textoken.w
%
% Copyright 2006-2011 Taco Hoekwater <taco@@luatex.org>
%
% This file is part of LuaTeX.
%
% LuaTeX is free software; you can redistribute it and/or modify it under
% the terms of the GNU General Public License as published by the Free
% Software Foundation; either version 2 of the License, or (at your
% option) any later version.
%
% LuaTeX is distributed in the hope that it will be useful, but WITHOUT
% ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
% FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
% License for more details.
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% You should have received a copy of the GNU General Public License along
% with LuaTeX; if not, see <http://www.gnu.org/licenses/>.

@ @c
static const char _svn_version[] =
    "$Id$"
    "$URL$";

#include "ptexlib.h"

@ @c
#define pausing int_par(pausing_code)
#define cat_code_table int_par(cat_code_table_code)
#define tracing_nesting int_par(tracing_nesting_code)
#define suppress_outer_error int_par(suppress_outer_error_code)

#define every_eof equiv(every_eof_loc)
#define box(A) equiv(box_base+(A))

#define detokenized_line() (line_catcode_table==NO_CAT_TABLE)

#define do_get_cat_code(a,b) do {                                         \
    if (line_catcode_table!=DEFAULT_CAT_TABLE)                          \
      a=get_cat_code(line_catcode_table,b);                       \
    else                                                                \
      a=get_cat_code(cat_code_table,b);                           \
  } while (0)


@ The \TeX\ system does nearly all of its own memory allocation, so that it
can readily be transported into environments that do not have automatic
facilities for strings, garbage collection, etc., and so that it can be in
control of what error messages the user receives. The dynamic storage
requirements of \TeX\ are handled by providing two large arrays called
|fixmem| and |varmem| in which consecutive blocks of words are used as
nodes by the \TeX\ routines.

Pointer variables are indices into this array, or into another array
called |eqtb| that will be explained later. A pointer variable might
also be a special flag that lies outside the bounds of |mem|, so we
allow pointers to assume any |halfword| value. The minimum halfword
value represents a null pointer. \TeX\ does not assume that |mem[null]| exists.



@ Locations in |fixmem| are used for storing one-word records; a conventional
\.{AVAIL} stack is used for allocation in this array.

@c
smemory_word *fixmem;           /* the big dynamic storage area */
unsigned fix_mem_min;           /* the smallest location of one-word memory in use */
unsigned fix_mem_max;           /* the largest location of one-word memory in use */


@ In order to study the memory requirements of particular applications, it
is possible to prepare a version of \TeX\ that keeps track of current and
maximum memory usage. When code between the delimiters |@!stat| $\ldots$
|tats| is not ``commented out,'' \TeX\ will run a bit slower but it will
report these statistics when |tracing_stats| is sufficiently large.

@c
int var_used, dyn_used;         /* how much memory is in use */

halfword avail;                 /* head of the list of available one-word nodes */
unsigned fix_mem_end;           /* the last one-word node used in |mem| */

halfword garbage;               /* head of a junk list, write only */
halfword temp_token_head;       /* head of a temporary list of some kind */
halfword hold_token_head;       /* head of a temporary list of another kind */
halfword omit_template;         /* a constant token list */
halfword null_list;             /* permanently empty list */
halfword backup_head;           /* head of token list built by |scan_keyword| */

@ @c
void initialize_tokens(void)
{
    halfword p;
    avail = null;
    fix_mem_end = 0;
    p = get_avail();
    temp_token_head = p;
    set_token_info(temp_token_head, 0);
    p = get_avail();
    hold_token_head = p;
    set_token_info(hold_token_head, 0);
    p = get_avail();
    omit_template = p;
    set_token_info(omit_template, 0);
    p = get_avail();
    null_list = p;
    set_token_info(null_list, 0);
    p = get_avail();
    backup_head = p;
    set_token_info(backup_head, 0);
    p = get_avail();
    garbage = p;
    set_token_info(garbage, 0);
    dyn_used = 0;               /* initialize statistics */
}

@ The function |get_avail| returns a pointer to a new one-word node whose
|link| field is null. However, \TeX\ will halt if there is no more room left.
@^inner loop@>

If the available-space list is empty, i.e., if |avail=null|,
we try first to increase |fix_mem_end|. If that cannot be done, i.e., if
|fix_mem_end=fix_mem_max|, we try to reallocate array |fixmem|.
If, that doesn't work, we have to quit.

@c
halfword get_avail(void)
{                               /* single-word node allocation */
    unsigned p;                 /* the new node being got */
    unsigned t;
    p = (unsigned) avail;       /* get top location in the |avail| stack */
    if (p != null) {
        avail = token_link(avail);      /* and pop it off */
    } else if (fix_mem_end < fix_mem_max) {     /* or go into virgin territory */
        incr(fix_mem_end);
        p = fix_mem_end;
    } else {
        smemory_word *new_fixmem;       /* the big dynamic storage area */
        t = (fix_mem_max / 5);
        new_fixmem =
            fixmemcast(realloc
                       (fixmem, sizeof(smemory_word) * (fix_mem_max + t + 1)));
        if (new_fixmem == NULL) {
            runaway();          /* if memory is exhausted, display possible runaway text */
            overflow("token memory size", fix_mem_max);
        } else {
            fixmem = new_fixmem;
        }
        memset(voidcast(fixmem + fix_mem_max + 1), 0, t * sizeof(smemory_word));
        fix_mem_max += t;
        p = ++fix_mem_end;
    }
    token_link(p) = null;       /* provide an oft-desired initialization of the new node */
    incr(dyn_used);             /* maintain statistics */
    return (halfword) p;
}


@ The procedure |flush_list(p)| frees an entire linked list of
one-word nodes that starts at position |p|.
@^inner loop@>

@c
void flush_list(halfword p)
{                               /* makes list of single-word nodes available */
    halfword q, r;              /* list traversers */
    if (p != null) {
        r = p;
        do {
            q = r;
            r = token_link(r);
            decr(dyn_used);
        } while (r != null);    /* now |q| is the last node on the list */
        token_link(q) = avail;
        avail = p;
    }
}

@ A \TeX\ token is either a character or a control sequence, and it is
@^token@>
represented internally in one of two ways: (1)~A character whose ASCII
code number is |c| and whose command code is |m| is represented as the
number $2^{21}m+c$; the command code is in the range |1<=m<=14|. (2)~A control
sequence whose |eqtb| address is |p| is represented as the number
|cs_token_flag+p|. Here |cs_token_flag=@t$2^{25}-1$@>| is larger than
$2^{21}m+c$, yet it is small enough that |cs_token_flag+p< max_halfword|;
thus, a token fits comfortably in a halfword.

A token |t| represents a |left_brace| command if and only if
|t<left_brace_limit|; it represents a |right_brace| command if and only if
we have |left_brace_limit<=t<right_brace_limit|; and it represents a |match| or
|end_match| command if and only if |match_token<=t<=end_match_token|.
The following definitions take care of these token-oriented constants
and a few others.

@ A token list is a singly linked list of one-word nodes in |mem|, where
each word contains a token and a link. Macro definitions, output-routine
definitions, marks, \.{\\write} texts, and a few other things
are remembered by \TeX\ in the form
of token lists, usually preceded by a node with a reference count in its
|token_ref_count| field. The token stored in location |p| is called
|info(p)|.

Three special commands appear in the token lists of macro definitions.
When |m=match|, it means that \TeX\ should scan a parameter
for the current macro; when |m=end_match|, it means that parameter
matching should end and \TeX\ should start reading the macro text; and
when |m=out_param|, it means that \TeX\ should insert parameter
number |c| into the text at this point.

The enclosing \.{\char'173} and \.{\char'175} characters of a macro
definition are omitted, but the final right brace of an output routine
is included at the end of its token list.

Here is an example macro definition that illustrates these conventions.
After \TeX\ processes the text
$$\.{\\def\\mac a\#1\#2 \\b \{\#1\\-a \#\#1\#2 \#2\}}$$
the definition of \.{\\mac} is represented as a token list containing
$$\def\,{\hskip2pt}
\vbox{\halign{\hfil#\hfil\cr
(reference count), |letter|\,\.a, |match|\,\#, |match|\,\#, |spacer|\,\.\ ,
\.{\\b}, |end_match|,\cr
|out_param|\,1, \.{\\-}, |letter|\,\.a, |spacer|\,\.\ , |mac_param|\,\#,
|other_char|\,\.1,\cr
|out_param|\,2, |spacer|\,\.\ , |out_param|\,2.\cr}}$$
The procedure |scan_toks| builds such token lists, and |macro_call|
does the parameter matching.
@^reference counts@>

Examples such as
$$\.{\\def\\m\{\\def\\m\{a\}\ b\}}$$
explain why reference counts would be needed even if \TeX\ had no \.{\\let}
operation: When the token list for \.{\\m} is being read, the redefinition of
\.{\\m} changes the |eqtb| entry before the token list has been fully
consumed, so we dare not simply destroy a token list when its
control sequence is being redefined.

If the parameter-matching part of a definition ends with `\.{\#\{}',
the corresponding token list will have `\.\{' just before the `|end_match|'
and also at the very end. The first `\.\{' is used to delimit the parameter; the
second one keeps the first from disappearing.

The |print_meaning| subroutine displays |cur_cmd| and |cur_chr| in
symbolic form, including the expansion of a macro or mark.

@c
void print_meaning(void)
{
    print_cmd_chr((quarterword) cur_cmd, cur_chr);
    if (cur_cmd >= call_cmd) {
        print_char(':');
        print_ln();
        token_show(cur_chr);
    } else {
        /* Show the meaning of a mark node */
        if ((cur_cmd == top_bot_mark_cmd) && (cur_chr < marks_code)) {
            print_char(':');
            print_ln();
            switch (cur_chr) {
            case first_mark_code:
                token_show(first_mark(0));
                break;
            case bot_mark_code:
                token_show(bot_mark(0));
                break;
            case split_first_mark_code:
                token_show(split_first_mark(0));
                break;
            case split_bot_mark_code:
                token_show(split_bot_mark(0));
                break;
            default:
                token_show(top_mark(0));
                break;
            }
        }
    }
}


@ The procedure |show_token_list|, which prints a symbolic form of
the token list that starts at a given node |p|, illustrates these
conventions. The token list being displayed should not begin with a reference
count. However, the procedure is intended to be robust, so that if the
memory links are awry or if |p| is not really a pointer to a token list,
nothing catastrophic will happen.

An additional parameter |q| is also given; this parameter is either null
or it points to a node in the token list where a certain magic computation
takes place that will be explained later. (Basically, |q| is non-null when
we are printing the two-line context information at the time of an error
message; |q| marks the place corresponding to where the second line
should begin.)

For example, if |p| points to the node containing the first \.a in the
token list above, then |show_token_list| will print the string
$$\hbox{`\.{a\#1\#2\ \\b\ ->\#1\\-a\ \#\#1\#2\ \#2}';}$$
and if |q| points to the node containing the second \.a,
the magic computation will be performed just before the second \.a is printed.

The generation will stop, and `\.{\\ETC.}' will be printed, if the length
of printing exceeds a given limit~|l|. Anomalous entries are printed in the
form of control sequences that are not followed by a blank space, e.g.,
`\.{\\BAD.}'; this cannot be confused with actual control sequences because
a real control sequence named \.{BAD} would come out `\.{\\BAD\ }'.

@c
void show_token_list(int p, int q, int l)
{
    int m, c;                   /* pieces of a token */
    ASCII_code match_chr;       /* character used in a `|match|' */
    ASCII_code n;               /* the highest parameter number, as an ASCII digit */
    match_chr = '#';
    n = '0';
    tally = 0;
    if (l < 0)
        l = 0x3FFFFFFF;
    while ((p != null) && (tally < l)) {
        if (p == q) {
            /* Do magic computation */
            set_trick_count();
        }
        /* Display token |p|, and |return| if there are problems */
        if ((p < (int) fix_mem_min) || (p > (int) fix_mem_end)) {
            tprint_esc("CLOBBERED.");
            return;
        }
        if (token_info(p) >= cs_token_flag) {
            if (!((inhibit_par_tokens) && (token_info(p) == par_token)))
                print_cs(token_info(p) - cs_token_flag);
        } else {
            m = token_cmd(token_info(p));
            c = token_chr(token_info(p));
            if (token_info(p) < 0) {
                tprint_esc("BAD.");
            } else {
                /* Display the token $(|m|,|c|)$ */
                /* The procedure usually ``learns'' the character code used for macro
                   parameters by seeing one in a |match| command before it runs into any
                   |out_param| commands. */
                switch (m) {
                case left_brace_cmd:
                case right_brace_cmd:
                case math_shift_cmd:
                case tab_mark_cmd:
                case sup_mark_cmd:
                case sub_mark_cmd:
                case spacer_cmd:
                case letter_cmd:
                case other_char_cmd:
                    print(c);
                    break;
                case mac_param_cmd:
                    if (!in_lua_escape)
                        print(c);
                    print(c);
                    break;
                case out_param_cmd:
                    print(match_chr);
                    if (c <= 9) {
                        print_char(c + '0');
                    } else {
                        print_char('!');
                        return;
                    }
                    break;
                case match_cmd:
                    match_chr = c;
                    print(c);
                    incr(n);
                    print_char(n);
                    if (n > '9')
                        return;
                    break;
                case end_match_cmd:
                    if (c == 0)
                        tprint("->");
                    break;
                default:
                    tprint_esc("BAD.");
                    break;
                }
            }
        }
        p = token_link(p);
    }
    if (p != null)
        tprint_esc("ETC.");
}

@ @c
#define do_buffer_to_unichar(a,b)  do {                         \
        a = (halfword)str2uni(buffer+b);                        \
        b += utf8_size(a);                                      \
    } while (0)


@ Here's the way we sometimes want to display a token list, given a pointer
to its reference count; the pointer may be null.

@c
void token_show(halfword p)
{
    if (p != null)
        show_token_list(token_link(p), null, 10000000);
}



@ |delete_token_ref|, is called when
a pointer to a token list's reference count is being removed. This means
that the token list should disappear if the reference count was |null|,
otherwise the count should be decreased by one.
@^reference counts@>

@c
void delete_token_ref(halfword p)
{                               /* |p| points to the reference count
                                   of a token list that is losing one reference */
    assert(token_ref_count(p) >= 0);
    if (token_ref_count(p) == 0)
        flush_list(p);
    else
        decr(token_ref_count(p));
}

@ @c
int get_char_cat_code(int curchr)
{
    int a;
    do_get_cat_code(a,curchr);
    return a;
}

@ @c
static void invalid_character_error(void)
{
    const char *hlp[] =
        { "A funny symbol that I can't read has just been input.",
        "Continue, and I'll forget that it ever happened.",
        NULL
    };
    deletions_allowed = false;
    tex_error("Text line contains an invalid character", hlp);
    deletions_allowed = true;
}

@ @c
static boolean process_sup_mark(void);  /* below */

static int scan_control_sequence(void); /* below */

typedef enum { next_line_ok, next_line_return,
    next_line_restart
} next_line_retval;

static next_line_retval next_line(void);        /* below */


@  In case you are getting bored, here is a slightly less trivial routine:
   Given a string of lowercase letters, like `\.{pt}' or `\.{plus}' or
   `\.{width}', the |scan_keyword| routine checks to see whether the next
   tokens of input match this string. The match must be exact, except that
   uppercase letters will match their lowercase counterparts; uppercase
   equivalents are determined by subtracting |"a"-"A"|, rather than using the
   |uc_code| table, since \TeX\ uses this routine only for its own limited
   set of keywords.

   If a match is found, the characters are effectively removed from the input
   and |true| is returned. Otherwise |false| is returned, and the input
   is left essentially unchanged (except for the fact that some macros
   may have been expanded, etc.).
   @^inner loop@>

@c
boolean scan_keyword(const char *s)
{                               /* look for a given string */
    halfword p;                 /* tail of the backup list */
    halfword q;                 /* new node being added to the token list via |store_new_token| */
    const char *k;              /* index into |str_pool| */
    halfword save_cur_cs = cur_cs;
    int saved_align_state = align_state;
    assert (strlen(s) > 1);
    p = backup_head;
    token_link(p) = null;
    k = s;
    while (*k) {
        get_x_token();      /* recursion is possible here */
        if ((cur_cs == 0) &&
            ((cur_chr == *k) || (cur_chr == *k - 'a' + 'A'))) {
            store_new_token(cur_tok);
            k++;
        } else if ((cur_cmd != spacer_cmd) || (p != backup_head)) {
            if (p != backup_head) {
                q = get_avail();
                token_info(q) = cur_tok;
                token_link(q) = null;
                token_link(p) = q;
                begin_token_list(token_link(backup_head), backed_up);
                if (cur_cmd != endv_cmd)
                   align_state = saved_align_state;
            } else {
                back_input();
            }
            cur_cs = save_cur_cs;
            return false;
        }
    }
    flush_list(token_link(backup_head));
    cur_cs = save_cur_cs;
    if (cur_cmd != endv_cmd)
        align_state = saved_align_state;
    return true;
}

@ We can not return |undefined_control_sequence| under some conditions
 (inside |shift_case|, for example). This needs thinking.

@c
halfword active_to_cs(int curchr, int force)
{
    halfword curcs;
    char *a, *b;
    char *utfbytes = xmalloc(10);
    int nncs = no_new_control_sequence;
    a = (char *) uni2str(0xFFFF);
    utfbytes = strcpy(utfbytes, a);
    if (force)
        no_new_control_sequence = false;
    if (curchr > 0) {
        b = (char *) uni2str((unsigned) curchr);
        utfbytes = strcat(utfbytes, b);
        free(b);
        curcs = string_lookup(utfbytes, strlen(utfbytes));
    } else {
        utfbytes[3] = '\0';
        curcs = string_lookup(utfbytes, 4);
    }
    no_new_control_sequence = nncs;
    free(a);
    free(utfbytes);
    return curcs;
}

@ TODO this function should listen to \.{\\escapechar}

@c
static char *cs_to_string(halfword p)
{                               /* prints a control sequence */
    const char *s;
    char *sh;
    int k = 0;
    static char ret[256] = { 0 };
    if (p == 0 || p == null_cs) {
        ret[k++] = '\\';
        s = "csname";
        while (*s) {
            ret[k++] = *s++;
        }
        ret[k++] = '\\';
        s = "endcsname";
        while (*s) {
            ret[k++] = *s++;
        }
        ret[k] = 0;

    } else {
        str_number txt = cs_text(p);
        sh = makecstring(txt);
        s = sh;
        if (is_active_cs(txt)) {
            s = s + 3;
            while (*s) {
                ret[k++] = *s++;
            }
            ret[k] = 0;
        } else {
            ret[k++] = '\\';
            while (*s) {
                ret[k++] = *s++;
            }
            ret[k] = 0;
        }
        free(sh);
    }
    return (char *) ret;
}

@ TODO this is a quick hack, will be solved differently soon

@c
static char *cmd_chr_to_string(int cmd, int chr)
{
    char *s;
    str_number str;
    int sel = selector;
    selector = new_string;
    print_cmd_chr((quarterword) cmd, chr);
    str = make_string();
    s = makecstring(str);
    selector = sel;
    flush_str(str);
    return s;
}

@ The heart of \TeX's input mechanism is the |get_next| procedure, which
we shall develop in the next few sections of the program. Perhaps we
shouldn't actually call it the ``heart,'' however, because it really acts
as \TeX's eyes and mouth, reading the source files and gobbling them up.
And it also helps \TeX\ to regurgitate stored token lists that are to be
processed again.
@^eyes and mouth@>

The main duty of |get_next| is to input one token and to set |cur_cmd|
and |cur_chr| to that token's command code and modifier. Furthermore, if
the input token is a control sequence, the |eqtb| location of that control
sequence is stored in |cur_cs|; otherwise |cur_cs| is set to zero.

Underlying this simple description is a certain amount of complexity
because of all the cases that need to be handled.
However, the inner loop of |get_next| is reasonably short and fast.

When |get_next| is asked to get the next token of a \.{\\read} line,
it sets |cur_cmd=cur_chr=cur_cs=0| in the case that no more tokens
appear on that line. (There might not be any tokens at all, if the
|end_line_char| has |ignore| as its catcode.)


@ The value of |par_loc| is the |eqtb| address of `\.{\\par}'. This quantity
is needed because a blank line of input is supposed to be exactly equivalent
to the appearance of \.{\\par}; we must set |cur_cs:=par_loc|
when detecting a blank line.

@c
halfword par_loc;               /* location of `\.{\\par}' in |eqtb| */
halfword par_token;             /* token representing `\.{\\par}' */


@ Parts |get_next| are executed more often than any other instructions of \TeX.
@^mastication@>@^inner loop@>



@ The global variable |force_eof| is normally |false|; it is set |true|
by an \.{\\endinput} command. |luacstrings| is the number of lua print
statements waiting to be input, it is changed by |luatokencall|.

@c
boolean force_eof;              /* should the next \.{\\input} be aborted early? */
int luacstrings;                /* how many lua strings are waiting to be input? */


@ If the user has set the |pausing| parameter to some positive value,
and if nonstop mode has not been selected, each line of input is displayed
on the terminal and the transcript file, followed by `\.{=>}'.
\TeX\ waits for a response. If the response is simply |carriage_return|, the
line is accepted as it stands, otherwise the line typed is
used instead of the line in the file.

@c
void firm_up_the_line(void)
{
    int k;                      /* an index into |buffer| */
    ilimit = last;
    if (pausing > 0) {
        if (interaction > nonstop_mode) {
            wake_up_terminal();
            print_ln();
            if (istart < ilimit) {
                for (k = istart; k <= ilimit - 1; k++)
                    print_char(buffer[k]);
            }
            first = ilimit;
            prompt_input("=>"); /* wait for user response */
            if (last > first) {
                for (k = first; k < +last - 1; k++)     /* move line down in buffer */
                    buffer[k + istart - first] = buffer[k];
                ilimit = istart + last - first;
            }
        }
    }
}



@ Before getting into |get_next|, let's consider the subroutine that
   is called when an `\.{\\outer}' control sequence has been scanned or
   when the end of a file has been reached. These two cases are distinguished
   by |cur_cs|, which is zero at the end of a file.

@c
void check_outer_validity(void)
{
    halfword p;                 /* points to inserted token list */
    halfword q;                 /* auxiliary pointer */
    if (suppress_outer_error)
        return;
    if (scanner_status != normal) {
        deletions_allowed = false;
        /* Back up an outer control sequence so that it can be reread; */
        /* An outer control sequence that occurs in a \.{\\read} will not be reread,
           since the error recovery for \.{\\read} is not very powerful. */
        if (cur_cs != 0) {
            if ((istate == token_list) || (iname < 1) || (iname > 17)) {
                p = get_avail();
                token_info(p) = cs_token_flag + cur_cs;
                begin_token_list(p, backed_up); /* prepare to read the control sequence again */
            }
            cur_cmd = spacer_cmd;
            cur_chr = ' ';      /* replace it by a space */
        }
        if (scanner_status > skipping) {
            const char *errhlp[] =
                { "I suspect you have forgotten a `}', causing me",
                "to read past where you wanted me to stop.",
                "I'll try to recover; but if the error is serious,",
                "you'd better type `E' or `X' now and fix your file.",
                NULL
            };
            char errmsg[256];
            const char *startmsg;
            const char *scannermsg;
            /* Tell the user what has run away and try to recover */
            runaway();          /* print a definition, argument, or preamble */
            if (cur_cs == 0) {
                startmsg = "File ended";
            } else {
                cur_cs = 0;
                startmsg = "Forbidden control sequence found";
            }
            /* Print either `\.{definition}' or `\.{use}' or `\.{preamble}' or `\.{text}',
               and insert tokens that should lead to recovery; */
            /* The recovery procedure can't be fully understood without knowing more
               about the \TeX\ routines that should be aborted, but we can sketch the
               ideas here:  For a runaway definition we will insert a right brace; for a
               runaway preamble, we will insert a special \.{\\cr} token and a right
               brace; and for a runaway argument, we will set |long_state| to
               |outer_call| and insert \.{\\par}. */
            p = get_avail();
            switch (scanner_status) {
            case defining:
                scannermsg = "definition";
                token_info(p) = right_brace_token + '}';
                break;
            case matching:
                scannermsg = "use";
                token_info(p) = par_token;
                long_state = outer_call_cmd;
                break;
            case aligning:
                scannermsg = "preamble";
                token_info(p) = right_brace_token + '}';
                q = p;
                p = get_avail();
                token_link(p) = q;
                token_info(p) = cs_token_flag + frozen_cr;
                align_state = -1000000;
                break;
            case absorbing:
                scannermsg = "text";
                token_info(p) = right_brace_token + '}';
                break;
            default:           /* can't happen */
                scannermsg = "unknown";
                break;
            }                   /*there are no other cases */
            begin_token_list(p, inserted);
            snprintf(errmsg, 255, "%s while scanning %s of %s",
                     startmsg, scannermsg, cs_to_string(warning_index));
            tex_error(errmsg, errhlp);
        } else {
            char errmsg[256];
            const char *errhlp_no[] =
                { "The file ended while I was skipping conditional text.",
                "This kind of error happens when you say `\\if...' and forget",
                "the matching `\\fi'. I've inserted a `\\fi'; this might work.",
                NULL
            };
            const char *errhlp_cs[] =
                { "A forbidden control sequence occurred in skipped text.",
                "This kind of error happens when you say `\\if...' and forget",
                "the matching `\\fi'. I've inserted a `\\fi'; this might work.",
                NULL
            };
            const char **errhlp = (const char **) errhlp_no;
            char *ss;
            if (cur_cs != 0) {
                errhlp = errhlp_cs;
                cur_cs = 0;
            }
            ss = cmd_chr_to_string(if_test_cmd, cur_if);
            snprintf(errmsg, 255,
                     "Incomplete %s; all text was ignored after line %d",
                     ss, (int) skip_line);
            free(ss);
            /* Incomplete \\if... */
            cur_tok = cs_token_flag + frozen_fi;
            /* back up one inserted token and call |error| */
            {
                OK_to_interrupt = false;
                back_input();
                token_type = inserted;
                OK_to_interrupt = true;
                tex_error(errmsg, errhlp);
            }
        }
        deletions_allowed = true;
    }
}

@ @c
static boolean get_next_file(void)
{
  SWITCH:
    if (iloc <= ilimit) {       /* current line not yet finished */
        do_buffer_to_unichar(cur_chr, iloc);

      RESWITCH:
        if (detokenized_line()) {
            cur_cmd = (cur_chr == ' ' ? 10 : 12);
        } else {
            do_get_cat_code(cur_cmd, cur_chr);
        }
        /*
           Change state if necessary, and |goto switch| if the current
           character should be ignored, or |goto reswitch| if the current
           character changes to another;
         */
        /* The following 48-way switch accomplishes the scanning quickly, assuming
           that a decent C compiler has translated the code. Note that the numeric
           values for |mid_line|, |skip_blanks|, and |new_line| are spaced
           apart from each other by |max_char_code+1|, so we can add a character's
           command code to the state to get a single number that characterizes both.
         */
        switch (istate + cur_cmd) {
        case mid_line + ignore_cmd:
        case skip_blanks + ignore_cmd:
        case new_line + ignore_cmd:
        case skip_blanks + spacer_cmd:
        case new_line + spacer_cmd:    /* Cases where character is ignored */
            goto SWITCH;
            break;
        case mid_line + escape_cmd:
        case new_line + escape_cmd:
        case skip_blanks + escape_cmd: /* Scan a control sequence ...; */
            istate = (unsigned char) scan_control_sequence();
            if (cur_cmd >= outer_call_cmd)
                check_outer_validity();
            break;
        case mid_line + active_char_cmd:
        case new_line + active_char_cmd:
        case skip_blanks + active_char_cmd:    /* Process an active-character  */
            cur_cs = active_to_cs(cur_chr, false);
            cur_cmd = eq_type(cur_cs);
            cur_chr = equiv(cur_cs);
            istate = mid_line;
            if (cur_cmd >= outer_call_cmd)
                check_outer_validity();
            break;
        case mid_line + sup_mark_cmd:
        case new_line + sup_mark_cmd:
        case skip_blanks + sup_mark_cmd:       /* If this |sup_mark| starts */
            if (process_sup_mark())
                goto RESWITCH;
            else
                istate = mid_line;
            break;
        case mid_line + invalid_char_cmd:
        case new_line + invalid_char_cmd:
        case skip_blanks + invalid_char_cmd:   /* Decry the invalid character and |goto restart|; */
            invalid_character_error();
            return false;       /* because state may be |token_list| now */
            break;
        case mid_line + spacer_cmd:    /* Enter |skip_blanks| state, emit a space; */
            istate = skip_blanks;
            cur_chr = ' ';
            break;
        case mid_line + car_ret_cmd:   /* Finish line, emit a space; */
            /* When a character of type |spacer| gets through, its character code is
               changed to $\.{"\ "}=040$. This means that the ASCII codes for tab and space,
               and for the space inserted at the end of a line, will
               be treated alike when macro parameters are being matched. We do this
               since such characters are indistinguishable on most computer terminal displays.
             */
            iloc = ilimit + 1;
            cur_cmd = spacer_cmd;
            cur_chr = ' ';
            break;
        case skip_blanks + car_ret_cmd:
        case mid_line + comment_cmd:
        case new_line + comment_cmd:
        case skip_blanks + comment_cmd:        /* Finish line, |goto switch|; */
            iloc = ilimit + 1;
            goto SWITCH;
            break;
        case new_line + car_ret_cmd:   /* Finish line, emit a \.{\\par}; */
            iloc = ilimit + 1;
            cur_cs = par_loc;
            cur_cmd = eq_type(cur_cs);
            cur_chr = equiv(cur_cs);
            if (cur_cmd >= outer_call_cmd)
                check_outer_validity();
            break;
        case skip_blanks + left_brace_cmd:
        case new_line + left_brace_cmd:
            istate = mid_line;  /* fall through */
        case mid_line + left_brace_cmd:
            align_state++;
            break;
        case skip_blanks + right_brace_cmd:
        case new_line + right_brace_cmd:
            istate = mid_line;  /* fall through */
        case mid_line + right_brace_cmd:
            align_state--;
            break;
        case mid_line + math_shift_cmd:
        case mid_line + tab_mark_cmd:
        case mid_line + mac_param_cmd:
        case mid_line + sub_mark_cmd:
        case mid_line + letter_cmd:
        case mid_line + other_char_cmd:
            break;
#if 0
               case skip_blanks + math_shift:
               case skip_blanks + tab_mark:
               case skip_blanks + mac_param:
               case skip_blanks + sub_mark:
               case skip_blanks + letter:
               case skip_blanks + other_char:
               case new_line    + math_shift:
               case new_line    + tab_mark:
               case new_line    + mac_param:
               case new_line    + sub_mark:
               case new_line    + letter:
               case new_line    + other_char:
#else
        default:
#endif
            istate = mid_line;
            break;
        }
    } else {
        if (iname != 21)
            istate = new_line;

        /*
           Move to next line of file,
           or |goto restart| if there is no next line,
           or |return| if a \.{\\read} line has finished;
         */
        do {
            next_line_retval r = next_line();
            if (r == next_line_return) {
                return true;
            } else if (r == next_line_restart) {
                return false;
            }
        } while (0);
        check_interrupt();
        goto SWITCH;
    }
    return true;
}

@ @c
#define is_hex(a) ((a>='0'&&a<='9')||(a>='a'&&a<='f'))

#define add_nybble(a)   do {                                            \
    if (a<='9') cur_chr=(cur_chr<<4)+a-'0';                             \
    else        cur_chr=(cur_chr<<4)+a-'a'+10;                          \
  } while (0)

#define hex_to_cur_chr do {                                             \
    if (c<='9')  cur_chr=c-'0';                                         \
    else         cur_chr=c-'a'+10;                                      \
    add_nybble(cc);                                                     \
  } while (0)

#define four_hex_to_cur_chr do {                                        \
    hex_to_cur_chr;                                                     \
    add_nybble(ccc); add_nybble(cccc);                                  \
  } while (0)

#define five_hex_to_cur_chr  do {                                       \
    four_hex_to_cur_chr;                                                \
    add_nybble(ccccc);                                                  \
  } while (0)

#define six_hex_to_cur_chr do {                                         \
    five_hex_to_cur_chr;                                                \
    add_nybble(cccccc);                                                 \
  } while (0)


@ Notice that a code like \.{\^\^8} becomes \.x if not followed by a hex digit.

@c
static boolean process_sup_mark(void)
{
    if (cur_chr == buffer[iloc]) {
        int c, cc;
        if (iloc < ilimit) {
            if ((cur_chr == buffer[iloc + 1]) && (cur_chr == buffer[iloc + 2])
                && (cur_chr == buffer[iloc + 3])
                && (cur_chr == buffer[iloc + 4])
                && ((iloc + 10) <= ilimit)) {
                int ccc, cccc, ccccc, cccccc;   /* constituents of a possible expanded code */
                c = buffer[iloc + 5];
                cc = buffer[iloc + 6];
                ccc = buffer[iloc + 7];
                cccc = buffer[iloc + 8];
                ccccc = buffer[iloc + 9];
                cccccc = buffer[iloc + 10];
                if ((is_hex(c)) && (is_hex(cc)) && (is_hex(ccc))
                    && (is_hex(cccc))
                    && (is_hex(ccccc)) && (is_hex(cccccc))) {
                    iloc = iloc + 11;
                    six_hex_to_cur_chr;
                    return true;
                }
            }
            if ((cur_chr == buffer[iloc + 1]) && (cur_chr == buffer[iloc + 2])
                && (cur_chr == buffer[iloc + 3]) && ((iloc + 8) <= ilimit)) {
                int ccc, cccc, ccccc;   /* constituents of a possible expanded code */
                c = buffer[iloc + 4];
                cc = buffer[iloc + 5];
                ccc = buffer[iloc + 6];
                cccc = buffer[iloc + 7];
                ccccc = buffer[iloc + 8];
                if ((is_hex(c)) && (is_hex(cc)) && (is_hex(ccc))
                    && (is_hex(cccc)) && (is_hex(ccccc))) {
                    iloc = iloc + 9;
                    five_hex_to_cur_chr;
                    return true;
                }
            }
            if ((cur_chr == buffer[iloc + 1]) && (cur_chr == buffer[iloc + 2])
                && ((iloc + 6) <= ilimit)) {
                int ccc, cccc;  /* constituents of a possible expanded code */
                c = buffer[iloc + 3];
                cc = buffer[iloc + 4];
                ccc = buffer[iloc + 5];
                cccc = buffer[iloc + 6];
                if ((is_hex(c)) && (is_hex(cc)) && (is_hex(ccc))
                    && (is_hex(cccc))) {
                    iloc = iloc + 7;
                    four_hex_to_cur_chr;
                    return true;
                }
            }
            c = buffer[iloc + 1];
            if (c < 0200) {     /* yes we have an expanded char */
                iloc = iloc + 2;
                if (is_hex(c) && iloc <= ilimit) {
                    cc = buffer[iloc];
                    if (is_hex(cc)) {
                        incr(iloc);
                        hex_to_cur_chr;
                        return true;
                    }
                }
                cur_chr = (c < 0100 ? c + 0100 : c - 0100);
                return true;
            }
        }
    }
    return false;
}

@ Control sequence names are scanned only when they appear in some line of
   a file; once they have been scanned the first time, their |eqtb| location
   serves as a unique identification, so \TeX\ doesn't need to refer to the
   original name any more except when it prints the equivalent in symbolic form.

   The program that scans a control sequence has been written carefully
   in order to avoid the blowups that might otherwise occur if a malicious
   user tried something like `\.{\\catcode\'15=0}'. The algorithm might
   look at |buffer[ilimit+1]|, but it never looks at |buffer[ilimit+2]|.

   If expanded characters like `\.{\^\^A}' or `\.{\^\^df}'
   appear in or just following
   a control sequence name, they are converted to single characters in the
   buffer and the process is repeated, slowly but surely.

@c
static boolean check_expanded_code(int *kk);    /* below */

static int scan_control_sequence(void)
{
    int retval = mid_line;
    if (iloc > ilimit) {
        cur_cs = null_cs;       /* |state| is irrelevant in this case */
    } else {
        register int cat;       /* |cat_code(cur_chr)|, usually */
        while (1) {
            int k = iloc;
            do_buffer_to_unichar(cur_chr, k);
            do_get_cat_code(cat, cur_chr);
            if (cat != letter_cmd || k > ilimit) {
                retval = (cat == spacer_cmd ? skip_blanks : mid_line);
                if (cat == sup_mark_cmd && check_expanded_code(&k))     /* If an expanded...; */
                    continue;
            } else {
                retval = skip_blanks;
                do {
                    do_buffer_to_unichar(cur_chr, k);
                    do_get_cat_code(cat, cur_chr);
                } while (cat == letter_cmd && k <= ilimit);

                if (cat == sup_mark_cmd && check_expanded_code(&k))     /* If an expanded...; */
                    continue;
                if (cat != letter_cmd) {
                    decr(k);
                    if (cur_chr > 0xFFFF)
                        decr(k);
                    if (cur_chr > 0x7FF)
                        decr(k);
                    if (cur_chr > 0x7F)
                        decr(k);
                }               /* now |k| points to first nonletter */
            }
            cur_cs = id_lookup(iloc, k - iloc);
            iloc = k;
            break;
        }
    }
    cur_cmd = eq_type(cur_cs);
    cur_chr = equiv(cur_cs);
    return retval;
}

@ Whenever we reach the following piece of code, we will have
   |cur_chr=buffer[k-1]| and |k<=ilimit+1| and |cat=get_cat_code(cat_code_table,cur_chr)|. If an
   expanded code like \.{\^\^A} or \.{\^\^df} appears in |buffer[(k-1)..(k+1)]|
   or |buffer[(k-1)..(k+2)]|, we
   will store the corresponding code in |buffer[k-1]| and shift the rest of
   the buffer left two or three places.

@c
static boolean check_expanded_code(int *kk)
{
    int l;
    int k = *kk;
    int d = 1;                  /* number of excess characters in an expanded code */
    int c, cc, ccc, cccc, ccccc, cccccc;        /* constituents of a possible expanded code */
    if (buffer[k] == cur_chr && k < ilimit) {
        if ((cur_chr == buffer[k + 1]) && (cur_chr == buffer[k + 2])
            && ((k + 6) <= ilimit)) {
            d = 4;
            if ((cur_chr == buffer[k + 3]) && ((k + 8) <= ilimit))
                d = 5;
            if ((cur_chr == buffer[k + 4]) && ((k + 10) <= ilimit))
                d = 6;
            c = buffer[k + d - 1];
            cc = buffer[k + d];
            ccc = buffer[k + d + 1];
            cccc = buffer[k + d + 2];
            if (d == 6) {
                ccccc = buffer[k + d + 3];
                cccccc = buffer[k + d + 4];
                if (is_hex(c) && is_hex(cc) && is_hex(ccc) && is_hex(cccc)
                    && is_hex(ccccc) && is_hex(cccccc))
                    six_hex_to_cur_chr;
            } else if (d == 5) {
                ccccc = buffer[k + d + 3];
                if (is_hex(c) && is_hex(cc) && is_hex(ccc) && is_hex(cccc)
                    && is_hex(ccccc))
                    five_hex_to_cur_chr;
            } else {
                if (is_hex(c) && is_hex(cc) && is_hex(ccc) && is_hex(cccc))
                    four_hex_to_cur_chr;
            }
        } else {
            c = buffer[k + 1];
            if (c < 0200) {
                d = 1;
                if (is_hex(c) && (k + 2) <= ilimit) {
                    cc = buffer[k + 2];
                    if (is_hex(c) && is_hex(cc)) {
                        d = 2;
                        hex_to_cur_chr;
                    }
                } else if (c < 0100) {
                    cur_chr = c + 0100;
                } else {
                    cur_chr = c - 0100;
                }
            }
        }
        if (d > 2)
            d = 2 * d - 1;
        else
            d++;
        if (cur_chr <= 0x7F) {
            buffer[k - 1] = (packed_ASCII_code) cur_chr;
        } else if (cur_chr <= 0x7FF) {
            buffer[k - 1] = (packed_ASCII_code) (0xC0 + cur_chr / 0x40);
            k++;
            d--;
            buffer[k - 1] = (packed_ASCII_code) (0x80 + cur_chr % 0x40);
        } else if (cur_chr <= 0xFFFF) {
            buffer[k - 1] = (packed_ASCII_code) (0xE0 + cur_chr / 0x1000);
            k++;
            d--;
            buffer[k - 1] =
                (packed_ASCII_code) (0x80 + (cur_chr % 0x1000) / 0x40);
            k++;
            d--;
            buffer[k - 1] =
                (packed_ASCII_code) (0x80 + (cur_chr % 0x1000) % 0x40);
        } else {
            buffer[k - 1] = (packed_ASCII_code) (0xF0 + cur_chr / 0x40000);
            k++;
            d--;
            buffer[k - 1] =
                (packed_ASCII_code) (0x80 + (cur_chr % 0x40000) / 0x1000);
            k++;
            d--;
            buffer[k - 1] =
                (packed_ASCII_code) (0x80 +
                                     ((cur_chr % 0x40000) % 0x1000) / 0x40);
            k++;
            d--;
            buffer[k - 1] =
                (packed_ASCII_code) (0x80 +
                                     ((cur_chr % 0x40000) % 0x1000) % 0x40);
        }
        l = k;
        ilimit = ilimit - d;
        while (l <= ilimit) {
            buffer[l] = buffer[l + d];
            l++;
        }
        *kk = k;
        return true;
    }
    return false;
}


@ All of the easy branches of |get_next| have now been taken care of.
  There is one more branch.

@c
static next_line_retval next_line(void)
{
    boolean inhibit_eol = false;        /* a way to end a pseudo file without trailing space */
    if (iname > 17) {
        /* Read next line of file into |buffer|, or |goto restart| if the file has ended */
        incr(line);
        first = istart;
        if (!force_eof) {
            if (iname <= 20) {
                if (pseudo_input()) {   /* not end of file */
                    firm_up_the_line(); /* this sets |ilimit| */
                    line_catcode_table = DEFAULT_CAT_TABLE;
                    if ((iname == 19) && (pseudo_lines(pseudo_files) == null))
                        inhibit_eol = true;
                } else if ((every_eof != null) && !eof_seen[iindex]) {
                    ilimit = first - 1;
                    eof_seen[iindex] = true;    /* fake one empty line */
                    if (iname != 19)
                        begin_token_list(every_eof, every_eof_text);
                    return next_line_restart;
                } else {
                    force_eof = true;
                }
            } else {
                if (iname == 21) {
                    if (luacstring_input()) {   /* not end of strings  */
                        firm_up_the_line();
                        line_catcode_table = (short) luacstring_cattable();
                        line_partial = (signed char) luacstring_partial();
                        if (luacstring_final_line() || line_partial
                            || line_catcode_table == NO_CAT_TABLE)
                            inhibit_eol = true;
                        if (!line_partial)
                            istate = new_line;
                    } else {
                        force_eof = true;
                    }
                } else {
                    if (lua_input_ln(cur_file, 0, true)) {      /* not end of file */
                        firm_up_the_line();     /* this sets |ilimit| */
                        line_catcode_table = DEFAULT_CAT_TABLE;
                    } else if ((every_eof != null) && (!eof_seen[iindex])) {
                        ilimit = first - 1;
                        eof_seen[iindex] = true;        /* fake one empty line */
                        begin_token_list(every_eof, every_eof_text);
                        return next_line_restart;
                    } else {
                        force_eof = true;
                    }
                }
            }
        }
        if (force_eof) {
            if (tracing_nesting > 0)
                if ((grp_stack[in_open] != cur_boundary)
                    || (if_stack[in_open] != cond_ptr))
                    if (!((iname == 19) || (iname == 21)))
                        file_warning(); /* give warning for some unfinished groups and/or conditionals */
            if ((iname > 21) || (iname == 20)) {
                report_stop_file(filetype_tex);
                decr(open_parens);
#if 0
                update_terminal(); /* show user that file has been read */
#endif
            }
            force_eof = false;
            if (iname == 21 ||  /* lua input */
                iname == 19) {  /* \.{\\scantextokens} */
                end_file_reading();
            } else {
                end_file_reading();
                check_outer_validity();
            }
            return next_line_restart;
        }
        if (inhibit_eol || end_line_char_inactive)
            ilimit--;
        else
            buffer[ilimit] = (packed_ASCII_code) end_line_char;
        first = ilimit + 1;
        iloc = istart;          /* ready to read */
    } else {
        if (!terminal_input) {  /* \.{\\read} line has ended */
            cur_cmd = 0;
            cur_chr = 0;
            return next_line_return;    /* OUTER */
        }
        if (input_ptr > 0) {    /* text was inserted during error recovery */
            end_file_reading();
            return next_line_restart;   /* resume previous level */
        }
        if (selector < log_only)
            open_log_file();
        if (interaction > nonstop_mode) {
            if (end_line_char_inactive)
                ilimit++;
            if (ilimit == istart) {     /* previous line was empty */
                tprint_nl("(Please type a command or say `\\end')");
            }
            print_ln();
            first = istart;
            prompt_input("*");  /* input on-line into |buffer| */
            ilimit = last;
            if (end_line_char_inactive)
                ilimit--;
            else
                buffer[ilimit] = (packed_ASCII_code) end_line_char;
            first = ilimit + 1;
            iloc = istart;
        } else {
            fatal_error("*** (job aborted, no legal \\end found)");
            /* nonstop mode, which is intended for overnight batch processing,
               never waits for on-line input */
        }
    }
    return next_line_ok;
}

@ Let's consider now what happens when |get_next| is looking at a token list.

@c
static boolean get_next_tokenlist(void)
{
    register halfword t;        /* a token */
    t = token_info(iloc);
    iloc = token_link(iloc);    /* move to next */
    if (t >= cs_token_flag) {   /* a control sequence token */
        cur_cs = t - cs_token_flag;
        cur_cmd = eq_type(cur_cs);
        if (cur_cmd >= outer_call_cmd) {
            if (cur_cmd == dont_expand_cmd) {   /* Get the next token, suppressing expansion */
                /* The present point in the program is reached only when the |expand|
                   routine has inserted a special marker into the input. In this special
                   case, |token_info(iloc)| is known to be a control sequence token, and |token_link(iloc)=null|.
                 */
                cur_cs = token_info(iloc) - cs_token_flag;
                iloc = null;
                cur_cmd = eq_type(cur_cs);
                if (cur_cmd > max_command_cmd) {
                    cur_cmd = relax_cmd;
                    cur_chr = no_expand_flag;
                    return true;
                }
            } else {
                check_outer_validity();
            }
        }
        cur_chr = equiv(cur_cs);
    } else {
        cur_cmd = token_cmd(t);
        cur_chr = token_chr(t);
        switch (cur_cmd) {
        case left_brace_cmd:
            align_state++;
            break;
        case right_brace_cmd:
            align_state--;
            break;
        case out_param_cmd:    /* Insert macro parameter and |goto restart|; */
            begin_token_list(param_stack[param_start + cur_chr - 1], parameter);
            return false;
            break;
        }
    }
    return true;
}

@ Now we're ready to take the plunge into |get_next| itself. Parts of
   this routine are executed more often than any other instructions of \TeX.
   @^mastication@>@^inner loop@>

@ sets |cur_cmd|, |cur_chr|, |cur_cs| to next token

@c
void get_next(void)
{
  RESTART:
    cur_cs = 0;
    if (istate != token_list) {
        /* Input from external file, |goto restart| if no input found */
        if (!get_next_file())
            goto RESTART;
    } else {
        if (iloc == null) {
            end_token_list();
            goto RESTART;       /* list exhausted, resume previous level */
        } else if (!get_next_tokenlist()) {
            goto RESTART;       /* parameter needs to be expanded */
        }
    }
    /* If an alignment entry has just ended, take appropriate action */
    if ((cur_cmd == tab_mark_cmd || cur_cmd == car_ret_cmd) && align_state == 0) {
        insert_vj_template();
        goto RESTART;
    }
}


@ Since |get_next| is used so frequently in \TeX, it is convenient
to define three related procedures that do a little more:

\yskip\hang|get_token| not only sets |cur_cmd| and |cur_chr|, it
also sets |cur_tok|, a packed halfword version of the current token.

\yskip\hang|get_x_token|, meaning ``get an expanded token,'' is like
|get_token|, but if the current token turns out to be a user-defined
control sequence (i.e., a macro call), or a conditional,
or something like \.{\\topmark} or \.{\\expandafter} or \.{\\csname},
it is eliminated from the input by beginning the expansion of the macro
or the evaluation of the conditional.

\yskip\hang|x_token| is like |get_x_token| except that it assumes that
|get_next| has already been called.

\yskip\noindent
In fact, these three procedures account for almost every use of |get_next|.

No new control sequences will be defined except during a call of
|get_token|, or when \.{\\csname} compresses a token list, because
|no_new_control_sequence| is always |true| at other times.

@c
void get_token(void)
{                               /* sets |cur_cmd|, |cur_chr|, |cur_tok| */
    no_new_control_sequence = false;
    get_token_lua();
    no_new_control_sequence = true;
    if (cur_cs == 0)
        cur_tok = token_val(cur_cmd, cur_chr);
    else
        cur_tok = cs_token_flag + cur_cs;
}

@ @c
void get_token_lua(void)
{
    register int callback_id;
    callback_id = callback_defined(token_filter_callback);
    if (callback_id > 0) {
        while (istate == token_list && iloc == null && iindex != v_template)
            end_token_list();
        /* there is some stuff we don't want to see inside the callback */
        if (!(istate == token_list &&
              ((nofilter == true) || (iindex == backed_up && iloc != null)))) {
            do_get_token_lua(callback_id);
            return;
        }
    }
    get_next();
}


@ changes the string |s| to a token list
@c
halfword string_to_toks(char *ss)
{
    halfword p;                 /* tail of the token list */
    halfword q;                 /* new node being added to the token list via |store_new_token| */
    halfword t;                 /* token being appended */
    char *s = ss, *se = ss + strlen(s);
    p = temp_token_head;
    set_token_link(p, null);
    while (s < se) {
        t = (halfword) str2uni((unsigned char *) s);
        s += utf8_size(t);
        if (t == ' ')
            t = space_token;
        else
            t = other_token + t;
        fast_store_new_token(t);
    }
    return token_link(temp_token_head);
}

@ The token lists for macros and for other things like \.{\\mark} and \.{\\output}
and \.{\\write} are produced by a procedure called |scan_toks|.

Before we get into the details of |scan_toks|, let's consider a much
simpler task, that of converting the current string into a token list.
The |str_toks| function does this; it classifies spaces as type |spacer|
and everything else as type |other_char|.

The token list created by |str_toks| begins at |link(temp_token_head)| and ends
at the value |p| that is returned. (If |p=temp_token_head|, the list is empty.)

|lua_str_toks| is almost identical, but it also escapes the three
symbols that |lua| considers special while scanning a literal string

@c
static halfword lua_str_toks(lstring b)
{                               /* changes the string |str_pool[b..pool_ptr]| to a token list */
    halfword p;                 /* tail of the token list */
    halfword q;                 /* new node being added to the token list via |store_new_token| */
    halfword t;                 /* token being appended */
    unsigned char *k;           /* index into string */
    p = temp_token_head;
    set_token_link(p, null);
    k = (unsigned char *) b.s;
    while (k < (unsigned char *) b.s + b.l) {
        t = pool_to_unichar(k);
        k += utf8_size(t);
        if (t == ' ') {
            t = space_token;
        } else {
            if ((t == '\\') || (t == '"') || (t == '\'') || (t == 10)
                || (t == 13))
                fast_store_new_token(other_token + '\\');
            if (t == 10)
                t = 'n';
            if (t == 13)
                t = 'r';
            t = other_token + t;
        }
        fast_store_new_token(t);
    }
    return p;
}


@ Incidentally, the main reason for wanting |str_toks| is the function |the_toks|,
which has similar input/output characteristics.

@c
halfword str_toks(lstring s)
{                               /* changes the string |str_pool[b..pool_ptr]| to a token list */
    halfword p;                 /* tail of the token list */
    halfword q;                 /* new node being added to the token list via |store_new_token| */
    halfword t;                 /* token being appended */
    unsigned char *k, *l;       /* index into string */
    p = temp_token_head;
    set_token_link(p, null);
    k = s.s;
    l = k + s.l;
    while (k < l) {
        t = pool_to_unichar(k);
        k += utf8_size(t);
        if (t == ' ')
            t = space_token;
        else
            t = other_token + t;
        fast_store_new_token(t);
    }
    return p;
}

@ Here's part of the |expand| subroutine that we are now ready to complete:
@c
void ins_the_toks(void)
{
    (void) the_toks();
    ins_list(token_link(temp_token_head));
}

@ This routine, used in the next one, prints the job name, possibly
modified by the |process_jobname| callback.

@c
static void print_job_name(void)
{
   if (job_name) {
      char *s, *ss; /* C strings for jobname before and after processing */
      int callback_id, lua_retval;
      s = (char*)str_string(job_name);
      callback_id = callback_defined(process_jobname_callback);
      if (callback_id > 0) {
        lua_retval = run_callback(callback_id, "S->S", s, &ss);
        if ((lua_retval == true) && (ss != NULL))
            s = ss;
      }
      tprint(s);
   } else {
      print(job_name);
   }
}

@ Here is a routine that print the result of a convert command, using
   the argument |i|. It returns |false | if it does not know to print
   the code |c|. The function exists because lua code and tex code can
   both call it to convert something.

@c
static boolean print_convert_string(halfword c, int i)
{
    int ff;                     /* for use with |set_ff| */
    boolean ret = true;
    switch (c) {
    case number_code:
        print_int(i);
        break;
    case uchar_code:
        print(i);
        break;
    case roman_numeral_code:
        print_roman_int(i);
        break;
    case etex_code:
        tprint(eTeX_version_string);
        break;
    case pdftex_revision_code:
        tprint(pdftex_revision);
        break;
    case luatex_revision_code:
        print(get_luatexrevision());
        break;
    case luatex_date_code:
        print_int(get_luatex_date_info());
        break;
    case pdftex_banner_code:
        tprint(pdftex_banner);
        break;
    case uniform_deviate_code:
        print_int(unif_rand(i));
        break;
    case normal_deviate_code:
        print_int(norm_rand());
        break;
    case format_name_code:
        print(format_name);
        break;
    case job_name_code:
        print_job_name();
        break;
    case font_name_code:
        append_string((unsigned char *) font_name(i),
                      (unsigned) strlen(font_name(i)));
        if (font_size(i) != font_dsize(i)) {
            tprint(" at ");
            print_scaled(font_size(i));
            tprint("pt");
        }
        break;
    case font_id_code:
        print_int(i);
        break;
    case math_style_code:
        print_math_style();
        break;
    case pdf_font_name_code:
    case pdf_font_objnum_code:
        set_ff(i);
        if (c == pdf_font_name_code)
            print_int(obj_info(static_pdf, pdf_font_num(ff)));
        else
            print_int(pdf_font_num(ff));
        break;
    case pdf_font_size_code:
        print_scaled(font_size(i));
        tprint("pt");
        break;
    case pdf_page_ref_code:
        print_int(pdf_get_obj(static_pdf, obj_type_page, i, false));
        break;
    case pdf_xform_name_code:
        print_int(obj_info(static_pdf, i));
        break;
    case eTeX_revision_code:
        tprint(eTeX_revision);
        break;
    default:
        ret = false;
        break;
    }
    return ret;
}

@ @c
int scan_lua_state(void) /* hh-ls: optional name or number (not optional name optional number) */
{
    /* Parse optional lua state integer, or an instance name to be stored in |sn| */
    /* Get the next non-blank non-relax non-call token */
    int sn = 0;
    do {
        get_x_token();
    } while ((cur_cmd == spacer_cmd) || (cur_cmd == relax_cmd));
    back_input();               /* have to push it back, whatever it is  */
    if (cur_cmd != left_brace_cmd) {
        if (scan_keyword("name")) {
            (void) scan_toks(false, true);
            sn = def_ref;
        } else {
            scan_register_num();
            if (get_lua_name(cur_val))
                sn = (cur_val - 65536);
        }
    }
    return sn;
}



@ The procedure |conv_toks| uses |str_toks| to insert the token list
for |convert| functions into the scanner; `\.{\\outer}' control sequences
are allowed to follow `\.{\\string}' and `\.{\\meaning}'.

The extra temp string |u| is needed because |pdf_scan_ext_toks| incorporates
any pending string in its output. In order to save such a pending string,
we have to create a temporary string that is destroyed immediately after.

@c
void conv_toks(void)
{
    int old_setting;            /* holds |selector| setting */
    halfword p, q;
    int save_scanner_status;    /* |scanner_status| upon entry */
    halfword save_def_ref;      /* |def_ref| upon entry, important if inside `\.{\\message}' */
    halfword save_warning_index;
    boolean bool;               /* temp boolean */
    str_number s;               /* first temp string */
    int sn;                     /* lua chunk name */
    str_number u = 0;           /* third temp string, will become non-nil if a string is already being built */
    int i = 0;                  /* first temp integer */
    int j = 0;                  /* second temp integer */
    int c = cur_chr;            /* desired type of conversion */
    str_number str;
    /* Scan the argument for command |c| */
    switch (c) {
    case uchar_code:
        scan_char_num();
        break;
    case number_code:
    case roman_numeral_code:
        scan_int();
        break;
    case string_code:
    case meaning_code:
        save_scanner_status = scanner_status;
        scanner_status = normal;
        get_token();
        scanner_status = save_scanner_status;
        break;
    case etex_code:
        break;
    case font_name_code:
    case font_id_code:
        scan_font_ident();
        break;
    case pdftex_revision_code:
    case luatex_revision_code:
    case luatex_date_code:
    case pdftex_banner_code:
        break;
    case pdf_font_name_code:
    case pdf_font_objnum_code:
    case pdf_font_size_code:
        scan_font_ident();
        if (cur_val == null_font)
            pdf_error("font", "invalid font identifier");
        if (c != pdf_font_size_code) {
            pdf_check_vf(cur_val);
            if (!font_used(cur_val))
                pdf_init_font(static_pdf, cur_val);
        }
        break;
    case pdf_page_ref_code:
        scan_int();
        if (cur_val <= 0)
            pdf_error("pageref", "invalid page number");
        break;
    case left_margin_kern_code:
    case right_margin_kern_code:
        scan_int();
        if ((box(cur_val) == null) || (type(box(cur_val)) != hlist_node))
            pdf_error("marginkern", "a non-empty hbox expected");
        break;
    case pdf_xform_name_code:
        scan_int();
        check_obj_type(static_pdf, obj_type_xform, cur_val);
        break;
    case pdf_creation_date_code:
        ins_list(string_to_toks(getcreationdate(static_pdf)));
        return;
        break;
    case format_name_code:
    case job_name_code:
        if (job_name == 0)
            open_log_file();
        break;
    case pdf_colorstack_init_code:
        bool = scan_keyword("page");
        if (scan_keyword("direct"))
            cur_val = direct_always;
        else if (scan_keyword("page"))
            cur_val = direct_page;
        else
            cur_val = set_origin;
        save_scanner_status = scanner_status;
        save_warning_index = warning_index;
        save_def_ref = def_ref;
        u = save_cur_string();
        scan_toks(false, true); /*hh-ls was scan_pdf_ext_toks();*/
        s = tokens_to_string(def_ref);
        delete_token_ref(def_ref);
        def_ref = save_def_ref;
        warning_index = save_warning_index;
        scanner_status = save_scanner_status;
        cur_val = newcolorstack(s, cur_val, bool);
        flush_str(s);
        cur_val_level = int_val_level;
        if (cur_val < 0) {
            print_err("Too many color stacks");
            help2("The number of color stacks is limited to 32768.",
                  "I'll use the default color stack 0 here.");
            error();
            cur_val = 0;
            restore_cur_string(u);
        }
        break;
    case uniform_deviate_code:
        scan_int();
        break;
    case normal_deviate_code:
        break;
    case lua_escape_string_code:
        {
            lstring escstr;
            int l = 0;
            save_scanner_status = scanner_status;
            save_def_ref = def_ref;
            save_warning_index = warning_index;
            scan_toks(false, true); /*hh-ls was scan_pdf_ext_toks();*/
            bool = in_lua_escape;
            in_lua_escape = true;
            escstr.s = (unsigned char *) tokenlist_to_cstring(def_ref, false, &l);
            escstr.l = (unsigned) l;
            in_lua_escape = bool;
            delete_token_ref(def_ref);
            def_ref = save_def_ref;
            warning_index = save_warning_index;
            scanner_status = save_scanner_status;
            (void) lua_str_toks(escstr);
            ins_list(token_link(temp_token_head));
            free(escstr.s);
            return;
        }
        break;
    case math_style_code:
        break;
    case expanded_code:
        save_scanner_status = scanner_status;
        save_warning_index = warning_index;
        save_def_ref = def_ref;
        u = save_cur_string();
        scan_toks(false, true); /*hh-ls was scan_pdf_ext_toks();*/
        warning_index = save_warning_index;
        scanner_status = save_scanner_status;
        ins_list(token_link(def_ref));
        def_ref = save_def_ref;
        restore_cur_string(u);
        return;
        break;
    case lua_code:
        u = save_cur_string();
        save_scanner_status = scanner_status;
        save_def_ref = def_ref;
        save_warning_index = warning_index;
        sn = scan_lua_state();
        scan_toks(false, true); /*hh-ls was scan_pdf_ext_toks();*/
        s = def_ref;
        warning_index = save_warning_index;
        def_ref = save_def_ref;
        scanner_status = save_scanner_status;
        luacstrings = 0;
        luatokencall(s, sn);
        delete_token_ref(s);
        restore_cur_string(u);  /* TODO: check this, was different */
        if (luacstrings > 0)
            lua_string_start();
        return;
        break;
    case lua_function_code:
        scan_int();
        if (cur_val <= 0) {
            pdf_error("luafunction", "invalid number");
        } else {
            u = save_cur_string();
            luacstrings = 0;
            luafunctioncall(cur_val);
            restore_cur_string(u);
            if (luacstrings > 0)
                lua_string_start();
        }
        break;
    case pdf_insert_ht_code:
        scan_register_num();
        break;
    case pdf_ximage_bbox_code:
        scan_int();
        check_obj_type(static_pdf, obj_type_ximage, cur_val);
        i = obj_data_ptr(static_pdf, cur_val);
        scan_int();
        j = cur_val;
        if ((j < 1) || (j > 4))
            pdf_error("pdfximagebbox", "invalid parameter");
        break;
        /* Cases of 'Scan the argument for command |c|' */
    case eTeX_revision_code:
        break;
    default:
        confusion("convert");
        break;
    }

    old_setting = selector;
    selector = new_string;

    /* Print the result of command |c| */
    if (!print_convert_string(c, cur_val)) {
        switch (c) {
        case string_code:
            if (cur_cs != 0)
                sprint_cs(cur_cs);
            else
                print(cur_chr);
            break;
        case meaning_code:
            print_meaning();
            break;
        case left_margin_kern_code:
            p = list_ptr(box(cur_val));
            if ((p != null) && (!is_char_node(p)) &&
                (type(p) == glue_node) && (subtype(p) == left_skip_code + 1))
                p = vlink(p);
            if ((p != null) && (!is_char_node(p)) &&
                (type(p) == margin_kern_node) && (subtype(p) == left_side))
                print_scaled(width(p));
            else
                print_char('0');
            tprint("pt");
            break;
        case right_margin_kern_code:
            q = list_ptr(box(cur_val));
            p = null;
            if (q != null) {
                p = prev_rightmost(q, null);
                if ((p != null) && (!is_char_node(p)) && (type(p) == glue_node)
                    && (subtype(p) == right_skip_code + 1))
                    p = prev_rightmost(q, p);
            }
            if ((p != null) && (!is_char_node(p)) &&
                (type(p) == margin_kern_node) && (subtype(p) == right_side))
                print_scaled(width(p));
            else
                print_char('0');
            tprint("pt");
            break;
        case pdf_colorstack_init_code:
            print_int(cur_val);
            break;
        case pdf_insert_ht_code:
            i = cur_val;
            p = page_ins_head;
            while (i >= subtype(vlink(p)))
                p = vlink(p);
            if (subtype(p) == i)
                print_scaled(height(p));
            else
                print_char('0');
            tprint("pt");
            break;
        case pdf_ximage_bbox_code:
            if (is_pdf_image(i)) {
                switch (j) {
                case 1:
                    print_scaled(epdf_orig_x(i));
                    break;
                case 2:
                    print_scaled(epdf_orig_y(i));
                    break;
                case 3:
                    print_scaled(epdf_orig_x(i) + epdf_xsize(i));
                    break;
                case 4:
                    print_scaled(epdf_orig_y(i) + epdf_ysize(i));
                    break;
                }
            } else {
                print_scaled(0);
            }
            tprint("pt");
            break;
        case pdf_creation_date_code:
        case lua_escape_string_code:
        case lua_code:
        case lua_function_code:
        case expanded_code:
            break;
        default:
            confusion("convert");
            break;
        }
    }

    selector = old_setting;
    str = make_string();
    (void) str_toks(str_lstring(str));
    flush_str(str);
    ins_list(token_link(temp_token_head));
}

@ This boolean is keeping track of the lua string escape state
@c
boolean in_lua_escape;

@ probably not needed anymore
@c
boolean is_convert(halfword c)
{
    return (c == convert_cmd);
}

str_number the_convert_string(halfword c, int i)
{
    int old_setting;            /* saved |selector| setting */
    str_number ret = 0;
    old_setting = selector;
    selector = new_string;
    if (print_convert_string(c, i)) {
        ret = make_string();
    } else if (c == font_identifier_code) {
        print_font_identifier(i);
        ret = make_string();
    }
    selector = old_setting;
    return ret;
}

@ Another way to create a token list is via the \.{\\read} command. The
sixteen files potentially usable for reading appear in the following
global variables. The value of |read_open[n]| will be |closed| if
stream number |n| has not been opened or if it has been fully read;
|just_open| if an \.{\\openin} but not a \.{\\read} has been done;
and |normal| if it is open and ready to read the next line.

@c
FILE *read_file[16];            /* used for \.{\\read} */
int read_open[17];              /* state of |read_file[n]| */

void initialize_read(void)
{
    int k;
    for (k = 0; k <= 16; k++)
        read_open[k] = closed;
}

@ The |read_toks| procedure constructs a token list like that for any
macro definition, and makes |cur_val| point to it. Parameter |r| points
to the control sequence that will receive this token list.

@c
void read_toks(int n, halfword r, halfword j)
{
    halfword p;                 /* tail of the token list */
    halfword q;                 /* new node being added to the token list via |store_new_token| */
    int s;                      /* saved value of |align_state| */
    int m;                      /* stream number */
    scanner_status = defining;
    warning_index = r;
    p = get_avail();
    def_ref = p;
    set_token_ref_count(def_ref, 0);
    p = def_ref;                /* the reference count */
    store_new_token(end_match_token);
    if ((n < 0) || (n > 15))
        m = 16;
    else
        m = n;
    s = align_state;
    align_state = 1000000;      /* disable tab marks, etc. */
    do {
        /* Input and store tokens from the next line of the file */
        begin_file_reading();
        iname = m + 1;
        if (read_open[m] == closed) {
            /* Input for \.{\\read} from the terminal */
            /* Here we input on-line into the |buffer| array, prompting the user explicitly
               if |n>=0|.  The value of |n| is set negative so that additional prompts
               will not be given in the case of multi-line input. */
            if (interaction > nonstop_mode) {
                if (n < 0) {
                    prompt_input("");
                } else {
                    wake_up_terminal();
                    print_ln();
                    sprint_cs(r);
                    prompt_input(" =");
                    n = -1;
                }
            } else {
                fatal_error
                    ("*** (cannot \\read from terminal in nonstop modes)");
            }

        } else if (read_open[m] == just_open) {
            /* Input the first line of |read_file[m]| */
            /* The first line of a file must be treated specially, since |lua_input_ln|
               must be told not to start with |get|. */
            if (lua_input_ln(read_file[m], (m + 1), false)) {
                read_open[m] = normal;
            } else {
                lua_a_close_in(read_file[m], (m + 1));
                read_open[m] = closed;
            }

        } else {
            /* Input the next line of |read_file[m]| */
            /*  An empty line is appended at the end of a |read_file|. */
            if (!lua_input_ln(read_file[m], (m + 1), true)) {
                lua_a_close_in(read_file[m], (m + 1));
                read_open[m] = closed;
                if (align_state != 1000000) {
                    runaway();
                    print_err("File ended within \\read");
                    help1("This \\read has unbalanced braces.");
                    align_state = 1000000;
                    error();
                }
            }

        }
        ilimit = last;
        if (end_line_char_inactive)
            decr(ilimit);
        else
            buffer[ilimit] = (packed_ASCII_code) int_par(end_line_char_code);
        first = ilimit + 1;
        iloc = istart;
        istate = new_line;
        /* Handle \.{\\readline} and |goto done|; */
        if (j == 1) {
            while (iloc <= ilimit) {    /* current line not yet finished */
                do_buffer_to_unichar(cur_chr, iloc);
                if (cur_chr == ' ')
                    cur_tok = space_token;
                else
                    cur_tok = cur_chr + other_token;
                store_new_token(cur_tok);
            }
        } else {
            while (1) {
                get_token();
                if (cur_tok == 0)
                    break;      /* |cur_cmd=cur_chr=0| will occur at the end of the line */
                if (align_state < 1000000) {    /* unmatched `\.\}' aborts the line */
                    do {
                        get_token();
                    } while (cur_tok != 0);
                    align_state = 1000000;
                    break;
                }
                store_new_token(cur_tok);
            }
        }
        end_file_reading();

    } while (align_state != 1000000);
    cur_val = def_ref;
    scanner_status = normal;
    align_state = s;
}

@ @c
str_number tokens_to_string(halfword p)
{                               /* return a string from tokens list */
    int old_setting;
    if (selector == new_string)
        pdf_error("tokens",
                  "tokens_to_string() called while selector = new_string");
    old_setting = selector;
    selector = new_string;
    show_token_list(token_link(p), null, -1);
    selector = old_setting;
    return make_string();
}

@ @c
#define make_room(a)                                    \
    if ((unsigned)i+a+1>alloci) {                      \
        ret = xrealloc(ret,(alloci+64));                \
        alloci = alloci + 64;                           \
    }


#define append_i_byte(a) ret[i++] = (char)(a)

#define Print_char(a) make_room(1); append_i_byte(a)

#define Print_uchar(s) {                                           \
    make_room(4);                                                  \
    if (s<=0x7F) {                                                 \
      append_i_byte(s);                                            \
    } else if (s<=0x7FF) {                                         \
      append_i_byte(0xC0 + (s / 0x40));                            \
      append_i_byte(0x80 + (s % 0x40));                            \
    } else if (s<=0xFFFF) {                                        \
      append_i_byte(0xE0 + (s / 0x1000));                          \
      append_i_byte(0x80 + ((s % 0x1000) / 0x40));                 \
      append_i_byte(0x80 + ((s % 0x1000) % 0x40));                 \
    } else if (s>=0x110000) {                                      \
      append_i_byte(s-0x11000);                                    \
    } else {                                                       \
      append_i_byte(0xF0 + (s / 0x40000));                         \
      append_i_byte(0x80 + ((s % 0x40000) / 0x1000));              \
      append_i_byte(0x80 + (((s % 0x40000) % 0x1000) / 0x40));     \
      append_i_byte(0x80 + (((s % 0x40000) % 0x1000) % 0x40));     \
    } }


#define Print_esc(b) {                                          \
    const char *v = b;                                          \
    if (e>0 && e<STRING_OFFSET) {                               \
        Print_uchar (e);                                        \
    }                                                           \
    make_room(strlen(v));                                       \
    while (*v) { append_i_byte(*v); v++; }                      \
  }

#define is_cat_letter(a)                                                \
    (get_char_cat_code(pool_to_unichar(str_string((a)))) == 11)

@ the actual token conversion in this function is now functionally
   equivalent to |show_token_list|, except that it always prints the
   whole token list.
   TODO: check whether this causes problems in the lua library.

@c
char *tokenlist_to_cstring(int pp, int inhibit_par, int *siz)
{
    register int p, c, m;
    int q;
    int infop;
    char *s, *sh;
    int e = 0;
    char *ret;
    int match_chr = '#';
    int n = '0';
    unsigned alloci = 1024;
    int i = 0;
    p = pp;
    if (p == null) {
        if (siz != NULL)
            *siz = 0;
        return NULL;
    }
    ret = xmalloc(alloci);
    p = token_link(p);          /* skip refcount */
    if (p != null) {
        e = int_par(escape_char_code);
    }
    while (p != null) {
        if (p < (int) fix_mem_min || p > (int) fix_mem_end) {
            Print_esc("CLOBBERED.");
            break;
        }
        infop = token_info(p);
        if (infop >= cs_token_flag) {
            if (!(inhibit_par && infop == par_token)) {
                q = infop - cs_token_flag;
                if (q < hash_base) {
                    if (q == null_cs) {
                        Print_esc("csname");
                        Print_esc("endcsname");
                    } else {
                        Print_esc("IMPOSSIBLE.");
                    }
                } else if ((q >= undefined_control_sequence)
                           && ((q <= eqtb_size)
                               || (q > eqtb_size + hash_extra))) {
                    Print_esc("IMPOSSIBLE.");
                } else if ((cs_text(q) < 0) || (cs_text(q) >= str_ptr)) {
                    Print_esc("NONEXISTENT.");
                } else {
                    str_number txt = cs_text(q);
                    sh = makecstring(txt);
                    s = sh;
                    if (is_active_cs(txt)) {
                        s = s + 3;
                        while (*s) {
                            Print_char(*s);
                            s++;
                        }
                    } else {
                        Print_uchar(e);
                        while (*s) {
                            Print_char(*s);
                            s++;
                        }
                        if ((!single_letter(txt)) || is_cat_letter(txt)) {
                            Print_char(' ');
                        }
                    }
                    free(sh);
                }
            }
        } else {
            if (infop < 0) {
                Print_esc("BAD.");
            } else {
                m = token_cmd(infop);
                c = token_chr(infop);
                switch (m) {
                case left_brace_cmd:
                case right_brace_cmd:
                case math_shift_cmd:
                case tab_mark_cmd:
                case sup_mark_cmd:
                case sub_mark_cmd:
                case spacer_cmd:
                case letter_cmd:
                case other_char_cmd:
                    Print_uchar(c);
                    break;
                case mac_param_cmd:
                    if (!in_lua_escape)
                        Print_uchar(c);
                    Print_uchar(c);
                    break;
                case out_param_cmd:
                    Print_uchar(match_chr);
                    if (c <= 9) {
                        Print_char(c + '0');
                    } else {
                        Print_char('!');
                        goto EXIT;
                    }
                    break;
                case match_cmd:
                    match_chr = c;
                    Print_uchar(c);
                    n++;
                    Print_char(n);
                    if (n > '9')
                        goto EXIT;
                    break;
                case end_match_cmd:
                    if (c == 0) {
                        Print_char('-');
                        Print_char('>');
                    }
                    break;
                default:
                    Print_esc("BAD.");
                    break;
                }
            }
        }
        p = token_link(p);
    }
  EXIT:
    ret[i] = '\0';
    if (siz != NULL)
        *siz = i;
    return ret;
}

@ @c
lstring *tokenlist_to_lstring(int pp, int inhibit_par)
{
    int siz;
    lstring *ret = xmalloc(sizeof(lstring));
    ret->s = (unsigned char *) tokenlist_to_cstring(pp, inhibit_par, &siz);
    ret->l = (size_t) siz;
    return ret;
}

@ @c
void free_lstring(lstring * ls)
{
    if (ls == NULL)
        return;
    if (ls->s != NULL)
        free(ls->s);
    free(ls);
}