/*

Copyright 2006-2012 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.

You should have received a copy of the GNU General Public License along
with LuaTeX; if not, see <http://www.gnu.org/licenses/>.

*/

#include "ptexlib.h"

/*tex Here are some macros that help process ligatures and kerns */

#define lig_kern_start(f,c)   char_remainder(f,c)

/*tex A value indicating |STOP| in a lig/kern program: */

#define stop_flag 128

/*tex The op code for a kern step: */

#define kern_flag 128

#define skip_byte(z)        lig_kerns[z].b0
#define next_char(z)        lig_kerns[z].b1
#define op_byte(z)          lig_kerns[z].b2
#define rem_byte(z)         lig_kerns[z].b3
#define lig_kern_restart(c) (256*op_byte(c)+rem_byte(c))


/*tex

    The information in a \TFM\file appears in a sequence of 8-bit bytes. Since
    the number of bytes is always a multiple of 4, we could also regard the file
    as a sequence of 32-bit words, but \TeX\ uses the byte interpretation. The
    format of \TFM\files was designed by Lyle Ramshaw in 1980. The intent is
    to convey a lot of different kinds of information in a compact but useful
    form.

    $\Omega$ is capable of reading not only \TFM\files, but also \.{OFM}
    files, which can describe fonts with up to 65536 characters and with huge
    lig/kern tables. These fonts will often be virtual fonts built up from real
    fonts with 256 characters, but $\Omega$ is not aware of this.

    The documentation below describes \TFM\files, with slight additions to
    show where \.{OFM} files differ.

    The first 24 bytes (6 words) of a \TFM\file contain twelve 16-bit integers
    that give the lengths of the various subsequent portions of the file. These
    twelve integers are, in order:

    \starttabulate
        \NC \type {lf| \NC length of the entire file, in words \NC \NR
        \NC \type {lh| \NC length of the header data, in words \NC \NR
        \NC \type {bc| \NC smallest character code in the font \NC \NR
        \NC \type {ec| \NC largest character code in the font \NC \NR
        \NC \type {nw| \NC number of words in the width table \NC \NR
        \NC \type {nh| \NC number of words in the height table \NC \NR
        \NC \type {nd| \NC number of words in the depth table \NC \NR
        \NC \type {ni| \NC number of words in the italic correction table \NC \NR
        \NC \type {nl| \NC number of words in the lig/kern table \NC \NR
        \NC \type {nk| \NC number of words in the kern table \NC \NR
        \NC \type {ne| \NC number of words in the extensible character table \NC \NR
        \NC \type {np| \NC number of font parameter words \NC \NR
    \stoptabulate

    They are all nonnegative and less than $2^{15}$. We must have
    |bc-1<=ec<=255|, and $|lf=6+lh+(ec-bc+1)+nw+nh+nd+ni+nl+nk+ne+np|$. Note that
    a \TFM\font may contain as many as 256 characters (if |bc=0| and
    |ec=255|), and as few as 0 characters (if |bc=ec+1|).

    Incidentally, when two or more 8-bit bytes are combined to form an integer of
    16 or more bits, the most significant bytes appear first in the file. This is
    called BigEndian order.

    The first 52 bytes (13 words) of an \.{OFM} file contains thirteen 32-bit
    integers that give the lengths of the various subsequent portions of the
    file. The first word is 0 (future versions of \.{OFM} files could have
    different values; what is important is that the first two bytes be 0 to
    differentiate \TFM\and \.{OFM} files). The next twelve integers are as
    above, all nonegative and less than~$2^{31}$. We must have |bc-1<=ec<=65535|,
    and $$\hbox{|lf=13+lh+2*(ec-bc+1)+nw+nh+nd+ni+nl+nk+ne+np|.}$$ Note that an
    \.{OFM} font may contain as many as 65536 characters (if |bc=0| and
    |ec=65535|), and as few as 0 characters (if |bc=ec+1|).

    The rest of the \TFM\file may be regarded as a sequence of ten data arrays
    having the informal specification

    \starttabulate
    \NC \type {header}     \NC \type {[0..lh-1]} \NC \type {stuff} \NC \NR
    \NC \type {char\_info} \NC \type {[bc..ec]}  \NC \type {char_info_word} \NC \NR
    \NC \type {width}      \NC \type {[0..nw-1]} \NC \type {fix_word} \NC \NR
    \NC \type {height}     \NC \type {[0..nh-1]} \NC \type {fix_word} \NC \NR
    \NC \type {depth}      \NC \type {[0..nd-1]} \NC \type {fix_word} \NC \NR
    \NC \type {italic}     \NC \type {[0..ni-1]} \NC \type {fix_word} \NC \NR
    \NC \type {lig\_kern}  \NC \type {[0..nl-1]} \NC \type {lig_kern_command} \NC \NR
    \NC \type {kern}       \NC \type {[0..nk-1]} \NC \type {fix_word} \NC \NR
    \NC \type {exten}      \NC \type {[0..ne-1]} \NC \type {extensible_recipe} \NC \NR
    \NC \type {param}      \NC \type {[1..np]}   \NC \type {fix_word} \NC \NR
    \stoptabulate

    The most important data type used here is a |@!fix_word|, which is a 32-bit
    representation of a binary fraction. A |fix_word| is a signed quantity, with
    the two's complement of the entire word used to represent negation. Of the 32
    bits in a |fix_word|, exactly 12 are to the left of the binary point; thus,
    the largest |fix_word| value is $2048-2^{-20}$, and the smallest is $-2048$.
    We will see below, however, that all but two of the |fix_word| values must
    lie between $-16$ and $+16$.

    The first data array is a block of header information, which contains general
    facts about the font. The header must contain at least two words, |header[0]|
    and |header[1]|, whose meaning is explained below. Additional header
    information of use to other software routines might also be included, but
    \TeX82 does not need to know about such details. For example, 16 more words
    of header information are in use at the Xerox Palo Alto Research Center; the
    first ten specify the character coding scheme used (e.g., `\.{XEROX text}' or
    `\.{TeX math symbols}'), the next five give the font identifier (e.g.,
    `\.{HELVETICA}' or `\.{CMSY}'), and the last gives the ``face byte.'' The
    program that converts \.{DVI} files to Xerox printing format gets this
    information by looking at the \TFM\file, which it needs to read anyway
    because of other information that is not explicitly repeated in
    \.{DVI}~format.

    \startitemize

        \startitem
            |header[0]| is a 32-bit check sum that \TeX\ will copy into the
            \.{DVI} output file. Later on when the \.{DVI} file is printed,
            possibly on another computer, the actual font that gets used is
            supposed to have a check sum that agrees with the one in the \TFM\
            file used by \TeX. In this way, users will be warned about potential
            incompatibilities. (However, if the check sum is zero in either the
            font file or the \TFM\file, no check is made.) The actual relation
            between this check sum and the rest of the \TFM\file is not
            important; the check sum is simply an identification number with the
            property that incompatible fonts almost always have distinct check
            sums.
        \stopitem

        \startitem
            |header[1]| is a |fix_word| containing the design size of the font,
            in units of \TeX\ points. This number must be at least 1.0; it is
            fairly arbitrary, but usually the design size is 10.0 for a ``10
            point'' font, i.e., a font that was designed to look best at a
            10-point size, whatever that really means. When a \TeX\ user asks for
            a font `\.{at} $\delta$ \.{pt}', the effect is to override the design
            size and replace it by $\delta$, and to multiply the $x$ and~$y$
            coordinates of the points in the font image by a factor of $\delta$
            divided by the design size. {\sl All other dimensions in the\/
            \TFM\file are |fix_word|\kern-1pt\ numbers in design-size units},
            with the exception of |param[1]| (which denotes the slant ratio).
            Thus, for example, the value of |param[6]|, which defines the \.{em}
            unit, is often the |fix_word| value $2^{20}=1.0$, since many fonts
            have a design size equal to one em. The other dimensions must be less
            than 16 design-size units in absolute value; thus, |header[1]| and
            |param[1]| are the only |fix_word| entries in the whole \TFM\file
            whose first byte might be something besides 0 or 255.
        \stopitem

    \stopitemize

    Next comes the |char_info| array, which contains one |@!char_info_word| per
    character. Each word in this part of a \TFM\file contains six fields
    packed into four bytes as follows.

    \startitemize
        \startitem
            first byte: |width_index| (8 bits)
        \stopitem
        \startitem
            second byte: |height_index| (4 bits) times 16, plus |depth_index|
            (4~bits)
        \stopitem
        \startitem
            third byte: |italic_index| (6 bits) times 4, plus |tag| (2~bits)
        \stopitem
        \startitem
            fourth byte: |remainder| (8 bits)
        \stopitem
    \stopitemize

    The actual width of a character is \\{width}|[width_index]|, in design-size
    units; this is a device for compressing information, since many characters
    have the same width. Since it is quite common for many characters to have the
    same height, depth, or italic correction, the \TFM\format imposes a limit
    of 16 different heights, 16 different depths, and 64 different italic
    corrections.

    For \.{OFM} files, two words (eight bytes) are used. The arrangement is as
    follows.

    \startitemize
        \startitem
            first and second bytes: |width_index| (16 bits)
        \stopitem
            \startitem third byte: |height_index| (8 bits)
        \stopitem
        \startitem
            fourth byte: |depth_index| (8~bits)
        \stopitem
        \startitem
            fifth and sixth bytes: |italic_index| (14 bits) times 4, plus |tag|
            (2~bits)
        \startitem
            seventh and eighth bytes: |remainder| (16 bits)
        \stopitem
    \stopitemize

    Therefore the \.{OFM} format imposes a limit of 256 different heights, 256
    different depths, and 16384 different italic corrections.

    The italic correction of a character has two different uses. (a)~In ordinary
    text, the italic correction is added to the width only if the \TeX\ user
    specifies `\.{\\/}' after the character. (b)~In math formulas, the italic
    correction is always added to the width, except with respect to the
    positioning of subscripts.

    Incidentally, the relation $\\{width}[0]=\\{height}[0]=\\{depth}[0]=
    \\{italic}[0]=0$ should always hold, so that an index of zero implies a value
    of zero. The |width_index| should never be zero unless the character does not
    exist in the font, since a character is valid if and only if it lies between
    |bc| and |ec| and has a nonzero |width_index|.

    \TeX\ checks the information of a \TFM\file for validity as the file is
    being read in, so that no further checks will be needed when typesetting is
    going on. The somewhat tedious subroutine that does this is called
    |read_font_info|. It has four parameters: the user font identifier~|u|, the
    file name and area strings |nom| and |aire|, and the ``at'' size~|s|. If
    |s|~is negative, it's the negative of a scale factor to be applied to the
    design size; |s=-1000| is the normal case. Otherwise |s| will be substituted
    for the design size; in this case, |s| must be positive and less than
    $2048\rm\,pt$ (i.e., it must be less than $2^{27}$ when considered as an
    integer).

    The subroutine opens and closes a global file variable called |tfm_file|. It
    returns the value of the internal font number that was just loaded. If an
    error is detected, an error message is issued and no font information is
    stored; |null_font| is returned in this case.

    The |tag| field in a |char_info_word| has four values that explain how to
    interpret the |remainder| field.

    \startitemize
        \startitem
            |tag=0| (|no_tag|) means that |remainder| is unused.
        \stopitem
        \startitem
            |tag=1| (|lig_tag|) means that this character has a ligature/kerning
            program starting at position |remainder| in the |lig_kern| array
        \stopitem
        \startitem
            |tag=2| (|list_tag|) means that this character is part of a chain of
            characters of ascending sizes, and not the largest in the chain. The
            |remainder| field gives the character code of the next larger
            character
        \stopitem
        \startitem
            |tag=3| (|ext_tag|) means that this character code represents an
            extensible character, i.e., a character that is built up of smaller
            pieces so that it can be made arbitrarily large. The pieces are
            specified in |exten[remainder]|
        \stopitem
    \stopitemize

    Characters with |tag=2| and |tag=3| are treated as characters with |tag=0|
    unless they are used in special circumstances in math formulas. For example,
    the \.{\\sum} operation looks for a |list_tag|, and the \.{\\left} operation
    looks for both |list_tag| and |ext_tag|.

    The |lig_kern| array contains instructions in a simple programming language
    that explains what to do for special letter pairs. Each word in this array,
    in a \TFM\file, is a |@!lig_kern_command| of four bytes.

    \startitemize
        \startitem
            first byte: |skip_byte|, indicates that this is the final program
            step if the byte is 128 or more, otherwise the next step is obtained
            by skipping this number of intervening steps
        \stopitem
        \startitem
            second byte: |next_char|, if |next_char| follows the current
            character, then perform the operation and stop, otherwise
            continue
        \stopitem
        \startitem
            third byte: |op_byte|, indicates a ligature step if less than~128, a
            kern step otherwise
        \stopitem
        \startitem
            fourth byte: |remainder|
        \stopitem
    \stopitemize

    In an \.{OFM} file, eight bytes are used, two bytes for each field.

    In a kern step, an additional space equal to |kern[256 * (op_byte-128) +
    remainder]| is inserted between the current character and |next_char|. This
    amount is often negative, so that the characters are brought closer together
    by kerning; but it might be positive.

    There are eight kinds of ligature steps, having |op_byte| codes $4a+2b+c$
    where $0\le a\le b+c$ and $0\le b,c\le1$. The character whose code is
    |remainder| is inserted between the current character and |next_char|; then
    the current character is deleted if $b=0$, and |next_char| is deleted if
    $c=0$; then we pass over $a$~characters to reach the next current character
    (which may have a ligature/kerning program of its own).

    If the very first instruction of the |lig_kern| array has |skip_byte=255|,
    the |next_char| byte is the so-called right boundary character of this font;
    the value of |next_char| need not lie between |bc| and~|ec|. If the very last
    instruction of the |lig_kern| array has |skip_byte=255|, there is a special
    ligature/kerning program for a left boundary character, beginning at location
    |256*op_byte+remainder|. The interpretation is that \TeX\ puts implicit
    boundary characters before and after each consecutive string of characters
    from the same font. These implicit characters do not appear in the output,
    but they can affect ligatures and kerning.

    If the very first instruction of a character's |lig_kern| program has
    |skip_byte>128|, the program actually begins in location
    |256*op_byte+remainder|. This feature allows access to large |lig_kern|
    arrays, because the first instruction must otherwise appear in a location
    |<=255| in a \TFM\file, |<=65535| in an \.{OFM} file.

    Any instruction with |skip_byte>128| in the |lig_kern| array must satisfy the
    condition $$\hbox{|256*op_byte+remainder<nl|.}$$ If such an instruction is
    encountered during normal program execution, it denotes an unconditional
    halt; no ligature or kerning command is performed.

    Extensible characters are specified by an |@!extensible_recipe|, which
    consists of four bytes in a \TFM\file, called |@!top|, |@!mid|, |@!bot|,
    and |@!rep| (in this order). In an \.{OFM} file, each field takes two bytes,
    for eight in total. These bytes are the character codes of individual pieces
    used to build up a large symbol. If |top|, |mid|, or |bot| are zero, they are
    not present in the built-up result. For example, an extensible vertical line
    is like an extensible bracket, except that the top and bottom pieces are
    missing.

    Let $T$, $M$, $B$, and $R$ denote the respective pieces, or an empty box if
    the piece isn't present. Then the extensible characters have the form
    $TR^kMR^kB$ from top to bottom, for some |k>=0|, unless $M$ is absent; in the
    latter case we can have $TR^kB$ for both even and odd values of~|k|. The
    width of the extensible character is the width of $R$; and the
    height-plus-depth is the sum of the individual height-plus-depths of the
    components used, since the pieces are butted together in a vertical list.

    The final portion of a \TFM\file is the |param| array, which is another
    sequence of |fix_word| values.

    \startitemize

    \startitem
        |param[1]=slant| is the amount of italic slant, which is used to help
        position accents. For example, |slant=.25| means that when you go up one
        unit, you also go .25 units to the right. The |slant| is a pure number;
        it's the only |fix_word| other than the design size itself that is not
        scaled by the design size.
    \stopitem

    \startitem
        |param[2]=space| is the normal spacing between words in text. Note that
        character |" "| in the font need not have anything to do with blank
        spaces.
    \stopitem

    \startitem
        |param[3]=space_stretch| is the amount of glue stretching between words.
    \stopitem

    \startitem
        |param[4]=space_shrink| is the amount of glue shrinking between words.
    \stopitem

    \startitem
        |param[5]=x_height| is the size of one ex in the font; it is also the
        height of letters for which accents don't have to be raised or lowered.
    \stopitem

    \startitem
        |param[6]=quad| is the size of one em in the font.
    \stopitem

    \startitem
        |param[7]=extra_space| is the amount added to |param[2]| at the ends of
        sentences.
    \stopitem


    If fewer than seven parameters are present, \TeX\ sets the missing parameters
    to zero. Fonts used for math symbols are required to have additional
    parameter information, which is explained later.


    There are programs called \.{TFtoPL} and \.{PLtoTF} that convert between the
    \TFM\format and a symbolic property-list format that can be easily edited.
    These programs contain extensive diagnostic information, so \TeX\ does not
    have to bother giving precise details about why it rejects a particular
    \TFM\file.

*/

#define tfm_abort {                    \
    font_tables[f]->_font_name = NULL; \
    font_tables[f]->_font_area = NULL; \
    xfree(tfm_buffer); xfree(kerns);   \
    xfree(widths);                     \
    xfree(heights);                    \
    xfree(depths);                     \
    xfree(italics);                    \
    xfree(extens);                     \
    xfree(lig_kerns);                  \
    xfree(xligs);                      \
    xfree(xkerns);                     \
    return 0;                          \
}

#define tfm_success {  \
    xfree(tfm_buffer); \
    xfree(kerns);      \
    xfree(widths);     \
    xfree(heights);    \
    xfree(depths);     \
    xfree(italics);    \
    xfree(extens);     \
    xfree(lig_kerns);  \
    xfree(xligs);      \
    xfree(xkerns);     \
    return 1;          \
}

static int open_tfm_file(const char *nom, unsigned char **tfm_buf, int *tfm_siz)
{
    /*tex Was the callback successful? */
    boolean res;
    /*tex Was |tfm_file| successfully opened? */
    boolean opened;
    int callback_id;
    FILE *tfm_file;
    char *fname = luatex_find_file(nom, find_font_file_callback);
    if (!fname)
        return -1;
    callback_id = callback_defined(read_font_file_callback);
    if (callback_id > 0) {
        res = run_callback(callback_id, "S->bSd", fname, &opened, tfm_buf, tfm_siz);
        if (res && opened && (*tfm_siz > 0)) {
            return 1;
        }
        if (!opened)
            return -1;
    } else {
        if (luatex_open_input(&(tfm_file), fname, kpse_ofm_format, FOPEN_RBIN_MODE, true)) {
            res = read_tfm_file(tfm_file, tfm_buf, tfm_siz);
            close_file(tfm_file);
            if (res) {
                return 1;
            }
        } else {
            return -1;
        }
    }
    return 0;
}

/*tex

  Note: A malformed \TFM\file might be shorter than it claims to be; thus
  |eof(tfm_file)| might be true when |read_font_info| refers to |tfm_file^| or
  when it says |get(tfm_file)|. If such circumstances cause system error
  messages, you will have to defeat them somehow, for example by defining |fget|
  to be `\ignorespaces|begin get(tfm_file);| |if eof(tfm_file) then abort;
  end|'.

*/

#define fget  tfm_byte++
#define fbyte tfm_buffer[tfm_byte]

#define read_sixteen(a) {           \
    a=tfm_buffer[tfm_byte++];       \
    if (a>127) { tfm_abort; }       \
    a=(a*256)+tfm_buffer[tfm_byte]; \
}

#define read_sixteen_unsigned(a) {  \
    a=tfm_buffer[tfm_byte++];       \
    a=(a*256)+tfm_buffer[tfm_byte]; \
}

#define read_thirtytwo(a) {           \
    a=tfm_buffer[++tfm_byte];         \
    if (a>127) { tfm_abort; }         \
    a=(a*256)+tfm_buffer[++tfm_byte]; \
    a=(a*256)+tfm_buffer[++tfm_byte]; \
    a=(a*256)+tfm_buffer[++tfm_byte]; \
}

#define store_four_bytes(z) {         \
    a=tfm_buffer[++tfm_byte];         \
    a=(a*256)+tfm_buffer[++tfm_byte]; \
    a=(a*256)+tfm_buffer[++tfm_byte]; \
    a=(a*256)+tfm_buffer[++tfm_byte]; \
    z = a;                            \
}

#define store_char_info(z) {            \
    if (font_level!=-1) {               \
        fget; read_sixteen_unsigned(a); \
        ci._width_index=a;              \
        fget; read_sixteen_unsigned(b); \
        ci._height_index=b>>8;          \
        ci._depth_index=b%256;          \
        fget; read_sixteen_unsigned(c); \
        ci._italic_index=c>>8;          \
        ci._tag=(unsigned char)(c%4);   \
        fget; read_sixteen_unsigned(d); \
        ci._remainder=d;                \
    } else {                            \
          a=tfm_buffer[++tfm_byte];     \
          ci._width_index=a;            \
          b=tfm_buffer[++tfm_byte];     \
          ci._height_index=b>>4;        \
          ci._depth_index=b%16;         \
          c=tfm_buffer[++tfm_byte];     \
          ci._italic_index=c>>2;        \
          ci._tag=(unsigned char)(c%4); \
          d=tfm_buffer[++tfm_byte];     \
          ci._remainder=d;              \
    }                                   \
}

#define read_four_quarters(q) {                              \
    if (font_level!=-1) {                                    \
        fget; read_sixteen_unsigned(a); q.b0=(quarterword)a; \
        fget; read_sixteen_unsigned(b); q.b1=(quarterword)b; \
        fget; read_sixteen_unsigned(c); q.b2=(quarterword)c; \
        fget; read_sixteen_unsigned(d); q.b3=(quarterword)d; \
    } else {                                                 \
          a=tfm_buffer[++tfm_byte]; q.b0=(quarterword)a;     \
          b=tfm_buffer[++tfm_byte]; q.b1=(quarterword)b;     \
          c=tfm_buffer[++tfm_byte]; q.b2=(quarterword)c;     \
          d=tfm_buffer[++tfm_byte]; q.b3=(quarterword)d;     \
    }                                                        \
}

#define check_byte_range(z) { if ((z<bc)||(z>ec)) tfm_abort ; }

/*

    A |fix_word| whose four bytes are $(a,b,c,d)$ from left to right represents
    the number $$x=\left\{\vcenter{\halign{$#$,\hfil\qquad&if $#$\hfil\cr
    b\cdot2^{-4}+c\cdot2^{-12}+d\cdot2^{-20}&a=0;\cr
    -16+b\cdot2^{-4}+c\cdot2^{-12}+d\cdot2^{-20}&a=255.\cr}}\right.$$ (No other
    choices of |a| are allowed, since the magnitude of a number in design-size
    units must be less than 16.) We want to multiply this quantity by the
    integer~|z|, which is known to be less than $2^{27}$. If $|z|<2^{23}$, the
    individual multiplications $b\cdot z$, $c\cdot z$, $d\cdot z$ cannot
    overflow; otherwise we will divide |z| by 2, 4, 8, or 16, to obtain a
    multiplier less than $2^{23}$, and we can compensate for this later. If |z|
    has thereby been replaced by $|z|^\prime=|z|/2^e$, let $\beta=2^{4-e}$; we
    shall compute $$\lfloor (b + c \cdot2^{-8} + d \cdot2^{-16}) \, z^\prime /
    \beta \rfloor$$ if $a=0$, or the same quantity minus $\alpha=2^{4+e}z^\prime$
    if $a=255$. This calculation must be done exactly, in order to guarantee
    portability of \TeX\ between computers.

*/

#define store_scaled(zz) {                       \
    fget;                                        \
    a = fbyte;                                   \
    fget;                                        \
    b = fbyte;                                   \
    fget;                                        \
    c = fbyte;                                   \
    fget;                                        \
    d = fbyte;                                   \
    sw = (((((d*z)>>8)+(c*z))>>8)+(b*z)) / beta; \
    if (a == 0) {                                \
        zz = sw;                                 \
    } else if (a == 255) {                       \
        zz = sw-alpha;                           \
    } else {                                     \
        tfm_abort;                               \
    }                                            \
}

scaled store_scaled_f(scaled sq, scaled z_in)
{
    eight_bits a, b, c, d;
    scaled sw;
    /*tex Here beta: runs from 1 upto 16 */
    static int alpha, beta;
    static scaled z, z_prev = 0;
    /*tex Replace |z| by $|z|^\prime$ and compute $\alpha,\beta$ */
    if (z_in != z_prev || z_prev == 0) {
        z = z_prev = z_in;
        alpha = 16;
        while (z >= 0x800000) {
            z /= 2;
            alpha += alpha;
        }
        beta = 256 / alpha;
        alpha *= z;
    };
    if (sq >= 0) {
        d = (eight_bits) (sq % 256);
        sq = sq / 256;
        c = (eight_bits) (sq % 256);
        sq = sq / 256;
        b = (eight_bits) (sq % 256);
        sq = sq / 256;
        a = (eight_bits) (sq % 256);
    } else {
        sq = (sq + 1073741824) + 1073741824;
        d = (eight_bits) (sq % 256);
        sq = sq / 256;
        c = (eight_bits) (sq % 256);
        sq = sq / 256;
        b = (eight_bits) (sq % 256);
        sq = sq / 256;
        a = (eight_bits) ((sq + 128) % 256);
    }
    if (beta==0)
        normal_error("vf", "vf scaling");
    sw = (((((d * z) >> 8) + (c * z)) >> 8) + (b * z)) / beta;
    if (a == 0)
        return sw;
    else if (a == 255)
        return (sw - alpha);
    else
        normal_error("vf", "vf scaling");
    return sw;
}

#define check_existence(z) { \
    check_byte_range(z);     \
    if (!char_exists(f,z)) { \
        tfm_abort;           \
    }                        \
}

typedef struct tfmcharacterinfo {
    int _kern_index;
    int _lig_index;
    int _width_index;
    int _height_index;
    int _depth_index;
    int _italic_index;
    int _remainder;
    unsigned char _tag;
} tfmcharacterinfo;

int read_tfm_info(internal_font_number f, const char *cnom, scaled s)
{
    /*tex index into |font_info| */
    int k;
    /*tex sizes of subfiles */
    halfword lf, lh, bc, ec, nw, nh, nd, ni, nl, nk, ne, np, slh;
    scaled *widths, *heights, *depths, *italics, *kerns;
    halfword font_dir;
    /*tex byte variables */
    int a, b, c=0, d=0;
    /*tex counter */
    int i;
    int font_level, header_length;
    int ncw, nlw, neew;
    tfmcharacterinfo ci;
    charinfo *co;
    four_quarters qw;
    four_quarters *lig_kerns, *extens;
    /*tex accumulators */
    scaled sw;
    /*tex left boundary start location, or infinity */
    int bch_label;
    /*tex 0..too_big_char; right boundary character, or |too_big_char| */
    int bchar;
    int first_two;
    /*tex the design size or the ``at'' size */
    scaled z;
    int alpha;
    /*tex 1..16 */
    char beta;
    /*tex aux. for ligkern processing */
    int *xligs, *xkerns;
    liginfo *cligs;
    kerninfo *ckerns;
    int fligs, fkerns;
    char *tmpnam;
    /*tex index into |tfm_buffer| */
    int tfm_byte = 0;
    /*tex saved index into |tfm_buffer| */
    int saved_tfm_byte = 0;
    /*tex byte buffer for tfm files */
    unsigned char *tfm_buffer = NULL;
    /*tex total size of the tfm file */
    int tfm_size = 0;
    int tmp;
    widths = NULL;
    heights = NULL;
    depths = NULL;
    italics = NULL;
    kerns = NULL;
    lig_kerns = NULL;
    extens = NULL;
    xkerns = NULL;
    ckerns = NULL;
    xligs = NULL;
    cligs = NULL;
    font_dir = 0;
    memset(&ci, 0, sizeof(tfmcharacterinfo));
    if (open_tfm_file(cnom, &tfm_buffer, &tfm_size) != 1)
        tfm_abort;
    /*tex When |cnom| is an absolute filename |xbasename| fixes that. */
    tmpnam = strdup(xbasename(cnom));
    if (strcmp(tmpnam + strlen(tmpnam) - 4, ".tfm") == 0 || strcmp(tmpnam + strlen(tmpnam) - 4, ".ofm") == 0) {
        *(tmpnam + strlen(tmpnam) - 4) = 0;
    }
    set_font_name(f, tmpnam);
    set_font_area(f, NULL);
    /*tex Read the \TFM\ size fields. */
    ncw = 0;
    read_sixteen(first_two);
    if (first_two != 0) {
        font_level = -1;
        lf = first_two;
        fget;
        read_sixteen(lh);
        fget;
        read_sixteen(bc);
        fget;
        read_sixteen(ec);
        if ((bc > ec + 1) || (ec > 255))
            tfm_abort;
        if (bc > 255) {
            /*tex |bc=256| and |ec=255| */
            bc = 1;
            ec = 0;
        };
        fget;
        read_sixteen(nw);
        fget;
        read_sixteen(nh);
        fget;
        read_sixteen(nd);
        fget;
        read_sixteen(ni);
        fget;
        read_sixteen(nl);
        fget;
        read_sixteen(nk);
        fget;
        read_sixteen(ne);
        fget;
        read_sixteen(np);
        header_length = 6;
        ncw = (ec - bc + 1);
        nlw = nl;
        neew = ne;
    } else {
        fget;
        read_sixteen(font_level);
        if (font_level != 0)
            tfm_abort;
        read_thirtytwo(lf);
        read_thirtytwo(lh);
        read_thirtytwo(bc);
        read_thirtytwo(ec);
        if ((bc > ec + 1) || (ec > 65535))
            tfm_abort;
        if (bc > 65535) {
            /*tex |bc=65536| and |ec=65535| */
            bc = 1;
            ec = 0;
        };
        read_thirtytwo(nw);
        read_thirtytwo(nh);
        read_thirtytwo(nd);
        read_thirtytwo(ni);
        read_thirtytwo(nl);
        read_thirtytwo(nk);
        read_thirtytwo(ne);
        read_thirtytwo(np);
        /*tex Some junk: */
        read_thirtytwo(font_dir);
        nlw = 2 * nl;
        neew = 2 * ne;
        header_length = 14;
        ncw = 2 * (ec - bc + 1);
    };
    if (lf !=
        (header_length + lh + ncw + nw + nh + nd + ni + nlw + nk + neew + np))
        tfm_abort;
    if ((nw == 0) || (nh == 0) || (nd == 0) || (ni == 0))
        tfm_abort;
    /*tex
        We check to see that the \TFM\ file doesn't end prematurely; but no
        error message is given for files having more than |lf| words.
     */
    if (lf * 4 > tfm_size)
        tfm_abort;
    /*tex Use size fields to allocate font information. */
    set_font_natural_dir(f, font_dir);
    set_font_bc(f, bc);
    set_font_ec(f, ec);
    /*tex Read the arrays first. */
    widths = xmalloc((unsigned) ((unsigned) nw * sizeof(scaled)));
    heights = xmalloc((unsigned) ((unsigned) nh * sizeof(scaled)));
    depths = xmalloc((unsigned) ((unsigned) nd * sizeof(scaled)));
    italics = xmalloc((unsigned) ((unsigned) ni * sizeof(scaled)));
    extens = xmalloc((unsigned) ((unsigned) ne * sizeof(four_quarters)));
    lig_kerns = xmalloc((unsigned) ((unsigned) nl * sizeof(four_quarters)));
    kerns = xmalloc((unsigned) ((unsigned) nk * sizeof(scaled)));
    /*
        Read the \TFM\ header. Only the first two words of the header are needed
        by \TeX82.
    */
    slh = lh;
    if (lh < 2)
        tfm_abort;
    store_four_bytes(tmp);
    font_checksum(f) = (unsigned) tmp;
    fget;
    /*tex This rejects a negative design size. */
    read_sixteen(z);
    fget;
    z = z * 256 + fbyte;
    fget;
    z = (z * 16) + (fbyte >> 4);
    if (z < unity)
        tfm_abort;
    while (lh > 2) {
        fget;
        fget;
        fget;
        fget;
        /*tex Ignore the rest of the header. */
        lh--;
    };
    /*tex Read the arrays before the character info. */
    set_font_dsize(f, z);
    if (s != -1000) {
        boolean saved_arith_error = arith_error;
	scaled sw = z;
	arith_error = false;
        z = (s >= 0 ? s : xn_over_d(z, -s, 1000));
	if ((arith_error) || (z>= 01000000000)) {
	  char err[256];
	  const char *errhelp[] = {
	    "I will ignore the scaling factor.",
	    NULL
	  };
	  snprintf(err, 255, "Font scaled to 2048pt or higher");
	  tex_error(err, errhelp);
	  z = sw ;
	}
	arith_error = saved_arith_error;
    }
    set_font_size(f, z);
    if (np > 7) {
        set_font_params(f, np);
    }
    saved_tfm_byte = tfm_byte;
    tfm_byte = (header_length + slh + ncw) * 4 - 1;
    /*tex Replace |z| by $|z|^\prime$ and compute $\alpha,\beta$ */
    alpha = 16;
    while (z >= 040000000) {
        z = z >> 1;
        alpha = alpha + alpha;
    };
    beta = (char) (256 / alpha);
    /*tex |beta| cannot be zero. */
    if (beta==0)
       normal_error("vf", "vf reading");
    alpha = alpha * z;
    /*tex Read box dimensions. */
    for (k = 0; k < nw; k++) {
        store_scaled(sw);
        widths[k] = sw;
    }
    /*tex |width[0]| must be zero */
    if (widths[0] != 0)
        tfm_abort;
    for (k = 0; k < nh; k++) {
        store_scaled(sw);
        heights[k] = sw;
    }
    /*tex |height[0]| must be zero */
    if (heights[0] != 0)
        tfm_abort;
    for (k = 0; k < nd; k++) {
        store_scaled(sw);
        depths[k] = sw;
    }
    /*tex |depth[0]| must be zero */
    if (depths[0] != 0)
        tfm_abort;
    for (k = 0; k < ni; k++) {
        store_scaled(sw);
        italics[k] = sw;
    }
    /*tex |italic[0]| must be zero */
    if (italics[0] != 0)
        tfm_abort;
    /*tex Read ligature and kern programs */
    bch_label = nl;
    bchar = 65536;
    if (nl > 0) {
        for (k = 0; k < nl; k++) {
            read_four_quarters(qw);
            lig_kerns[k] = qw;
            if (a > 128) {
                if (256 * c + d >= nl)
                    tfm_abort;
                if (a == 255 && k == 0)
                    bchar = b;
            } else {
                if (c < 128) {
                    /*tex Do nothing. */
                } else if (256 * (c - 128) + d >= nk) {
                    /*tex Check kern. */
                    tfm_abort;
                }
                if ((a < 128) && (k - 0 + a + 1 >= nl))
                    tfm_abort;
            };
        };
        if (a == 255)
            bch_label = 256 * c + d;
    };
    /*tex The actual kerns */
    for (k = 0; k < nk; k++) {
        store_scaled(sw);
        kerns[k] = sw;
    }
    /*tex Read extensible character recipes */
    for (k = 0; k < ne; k++) {
        read_four_quarters(qw);
        extens[k] = qw;
    }
    /*tex Read font parameters. */
    if (np > 7) {
        set_font_params(f, np);
    }
    for (k = 1; k <= np; k++) {
        if (k == 1) {
            /*tex The |slant| parameter is a pure number. */
            fget;
            sw = fbyte;
            if (sw > 127)
                sw = sw - 256;
            fget;
            sw = sw * 256 + fbyte;
            fget;
            sw = sw * 256 + fbyte;
            fget;
            sw = (sw * 16) + (fbyte >> 4);
            set_font_param(f, k, sw);
        } else {
            store_scaled(font_param(f, k));
        }
    }
    tfm_byte = saved_tfm_byte;
    /*tex Fix up the left boundary character. */
    fligs = 0;
    fkerns = 0;
    if (bch_label != nl) {
        k = bch_label;
        while (1) {
            if (skip_byte(k) <= stop_flag) {
                if (op_byte(k) >= kern_flag) {
                    fkerns++;
                } else {
                    fligs++;
                }
            }
            if (skip_byte(k) == 0) {
                k++;
            } else {
                if (skip_byte(k) >= stop_flag)
                    break;
                k += skip_byte(k) + 1;
            }
        }
    }
    if (fkerns > 0 || fligs > 0) {
        if (fligs > 0)
            cligs = xcalloc((unsigned) (fligs + 1), sizeof(liginfo));
        if (fkerns > 0)
            ckerns = xcalloc((unsigned) (fkerns + 1), sizeof(kerninfo));
        fligs = 0;
        fkerns = 0;
        k = bch_label;
        while (1) {
            if (skip_byte(k) <= stop_flag) {
                if (op_byte(k) >= kern_flag) {
                    set_kern_item(ckerns[fkerns], next_char(k), kerns[256 * (op_byte(k) - 128) + rem_byte(k)]);
                    fkerns++;
                } else {
                    set_ligature_item(cligs[fligs], (char) (op_byte(k) * 2 + 1), next_char(k), rem_byte(k));
                    fligs++;
                }
            }
            if (skip_byte(k) == 0) {
                k++;
            } else {
                if (skip_byte(k) >= stop_flag)
                    break;
                k += skip_byte(k) + 1;
            }
        }
        if (fkerns > 0 || fligs > 0) {
            co = get_charinfo(f, left_boundarychar);
            if (fkerns > 0) {
                set_kern_item(ckerns[fkerns], end_kern, 0);
                fkerns++;
                set_charinfo_kerns(co, ckerns);
            }
            if (fligs > 0) {
                set_ligature_item(cligs[fligs], 0, end_ligature, 0);
                fligs++;
                set_charinfo_ligatures(co, cligs);
            }
            set_charinfo_remainder(co, 0);
        }
    }
    /*tex Read character data. */
    for (k = bc; k <= ec; k++) {
        store_char_info(k);
        if (ci._width_index == 0)
            continue;
        if (ci._width_index >= nw || ci._height_index >= nh ||
            ci._depth_index >= nd || ci._italic_index >= ni)
            tfm_abort;
        d = ci._remainder;
        switch (ci._tag) {
        case lig_tag:
            if (d >= nl)
                tfm_abort;
            break;
        case ext_tag:
            if (d >= ne)
                tfm_abort;
            break;
        case list_tag:
            /*tex

                We want to make sure that there is no cycle of characters linked
                together by |list_tag| entries, since such a cycle would get
                \TEX\ into an endless loop. If such a cycle exists, the routine
                here detects it when processing the largest character code in the
                cycle.

             */
            check_byte_range(d);
            while (d < k) {
                /* |current_character == k| */
                if (char_tag(f, d) != list_tag) {
                    /*tex Not a cycle. */
                    goto NOT_FOUND;
                }
                /*tex Goto the next character on the list. */
                d = char_remainder(f, d);
            };
            if (d == k) {
                /*tex Yes, there's a cycle! */
                tfm_abort;
            }
          NOT_FOUND:
            break;
        }
        /*tex Put it in the actual font. */
        co = get_charinfo(f, k);
        set_charinfo_index(co, k);
        set_charinfo_tag(co, ci._tag);
        if (ci._tag == ext_tag) {
            /*tex top, bot, mid, rep */
            set_charinfo_extensible(co,
                extens[ci._remainder].b0,
                extens[ci._remainder].b2,
                extens[ci._remainder].b1,
                extens[ci._remainder].b3);
            set_charinfo_remainder(co, 0);
        } else {
            set_charinfo_remainder(co, ci._remainder);
        }
        set_charinfo_width(co, widths[ci._width_index]);
        set_charinfo_height(co, heights[ci._height_index]);
        set_charinfo_depth(co, depths[ci._depth_index]);
        set_charinfo_italic(co, italics[ci._italic_index]);
    };
    /*tex We now know the number of ligatures and kerns. */
    xligs = xcalloc((unsigned) (ec + 1), sizeof(int));
    xkerns = xcalloc((unsigned) (ec + 1), sizeof(int));
    for (i = bc; i <= ec; i++) {
        if (char_tag(f, i) == lig_tag) {
            k = lig_kern_start(f, i);
            if (skip_byte(k) > stop_flag)
                k = lig_kern_restart(k);
            /*tex Now k is the start index. */
            while (1) {
                if (skip_byte(k) <= stop_flag) {
                    if (op_byte(k) >= kern_flag) {
                        xkerns[i]++;
                        if (next_char(k) == bchar)
                            xkerns[i]++;
                    } else {
                        xligs[i]++;
                        if (next_char(k) == bchar)
                            xligs[i]++;
                    }
                }
                if (skip_byte(k) == 0) {
                    k++;
                } else {
                    if (skip_byte(k) >= stop_flag)
                        break;
                    k += skip_byte(k) + 1;
                }
            }
        }
    }
    cligs = NULL;
    ckerns = NULL;
    for (i = bc; i <= ec; i++) {
        fligs = 0;
        fkerns = 0;
        if (char_tag(f, i) == lig_tag) {
            k = lig_kern_start(f, i);
            if (skip_byte(k) > stop_flag)
                k = lig_kern_restart(k);
            /*tex Now k is the start index. */
            if (xligs[i] > 0)
                cligs = xcalloc((unsigned) (xligs[i] + 1), sizeof(liginfo));
            if (xkerns[i] > 0)
                ckerns = xcalloc((unsigned) (xkerns[i] + 1), sizeof(kerninfo));
            while (1) {
                if (skip_byte(k) <= stop_flag) {
                    if (op_byte(k) >= kern_flag) {
                        if (next_char(k) == bchar) {
                            set_kern_item(ckerns[fkerns], right_boundarychar, kerns[256 * (op_byte(k) - 128) + rem_byte(k)]);
                            fkerns++;
                        }
                        set_kern_item(ckerns[fkerns], next_char(k), kerns[256 * (op_byte(k) - 128) + rem_byte(k)]);
                        fkerns++;
                    } else {    /* lig */
                        if (next_char(k) == bchar) {
                            set_ligature_item(cligs[fligs], (char) (op_byte(k) * 2 + 1), right_boundarychar, rem_byte(k));
                            fligs++;
                        }
                        set_ligature_item(cligs[fligs], (char) (op_byte(k) * 2 + 1), next_char(k), rem_byte(k));
                        fligs++;
                    }
                }
                if (skip_byte(k) == 0) {
                    k++;
                } else {
                    if (skip_byte(k) >= stop_flag)
                        break;
                    k += skip_byte(k) + 1;
                }
            }
            if (fkerns > 0 || fligs > 0) {
                co = get_charinfo(f, i);
                if (fkerns > 0) {
                    set_kern_item(ckerns[fkerns], end_kern, 0);
                    fkerns++;
                    set_charinfo_kerns(co, ckerns);
                }
                if (fligs > 0) {
                    set_ligature_item(cligs[fligs], 0, end_ligature, 0);
                    fligs++;
                    set_charinfo_ligatures(co, cligs);
                }
                set_charinfo_remainder(co, 0);
            }
        }
    }
    /*tex

        Now it's time to wrap it up, we have checked all the necessary things
        about the \TFM\file, and all we need to do is put the finishing
        touches on the data for the new font.

    */
    if (bchar != 65536) {
        co = copy_charinfo(char_info(f, bchar));
        set_right_boundary(f, co);
    }
    tfm_success;
}
