/*   
  tfm-reader.cc --  implement Tex_font_metric_reader
  
  source file of the GNU LilyPond music typesetter
  
  (c) 1999--2002 Jan Nieuwenhuizen <janneke@gnu.org>
  

  some code shamelessly copied from GNU fontutils-0.6/tfm/tfm_input.c
 */

#include "tfm-reader.hh"
#include "string-convert.hh"
#include "warn.hh"
#include "warn.hh"

#define format_string String_convert::form_string
#define FIX_UNITY \
 (1 << 20)
static const Real fix_to_real (Fix f);


Tex_font_metric_reader::Tex_font_metric_reader (String name)
  : input_ (name)
{
  
  for (int i=0; i < TFM_SIZE; i++)
    ascii_to_metric_idx_.push (-1);

  read_header ();
  read_params ();
  read_char_metrics ();

}

static const Real
fix_to_real (Fix f)
{
  Real r = f / FIX_UNITY + ((Real) (f % FIX_UNITY) / (Real) FIX_UNITY);
  return r;
}

/* Most quantities are fixed-point fractions.  */

Real
Tex_font_metric_reader::get_U32_fix ()
{
  return fix_to_real (input_.get_U32 ());
}

/* Dimensions are a `Fix' scaled by the design size.  */

Real
Tex_font_metric_reader::get_U32_fix_scaled ()
{
  return get_U32_fix () * info_.design_size;
}

String
Tex_font_metric_reader::get_bcpl_string ()
{
  U8 length_u8 = input_.get_U8 ();
  String str = input_.get_string (length_u8);
  return str;
}

/* Here we read the information at the beginning of the file.  We store
   the result into the static variables `global_info' and
   `tfm_header'.  */
void
Tex_font_metric_reader::read_header ()
{
  U16 file_length = input_.get_U16 ();
 (void) file_length;
  U16 header_length = input_.get_U16 ();

  info_.first_charcode = input_.get_U16 ();
  info_.last_charcode = input_.get_U16 ();
  U16 width_word_count = input_.get_U16 ();
  U16 height_word_count = input_.get_U16 ();
  U16 depth_word_count = input_.get_U16 ();
  U16 italic_correction_word_count = input_.get_U16 ();
  U16 lig_kern_word_count = input_.get_U16 ();
  U16 kern_word_count = input_.get_U16 ();
 (void)kern_word_count;
  U16 extensible_word_count = input_.get_U16 ();
 (void)extensible_word_count;
  
  header_.param_word_count = input_.get_U16 ();
  info_.parameter_count = header_.param_word_count;

  header_.char_info_pos = (6 + header_length) * 4;
  header_.width_pos = header_.char_info_pos
                         + (info_.last_charcode
                            - info_.first_charcode + 1) * 4;
  header_.height_pos = header_.width_pos + width_word_count * 4;
  header_.depth_pos = header_.height_pos + height_word_count * 4;
  header_.italic_correction_pos = header_.depth_pos
                                     + depth_word_count * 4;
  header_.lig_kern_pos = header_.italic_correction_pos
    + italic_correction_word_count * 4;
  header_.kern_pos = header_.lig_kern_pos + lig_kern_word_count * 4;
  /* We don't care about the extensible table.  */

  if (header_length < 2)
    /* Not using ngettext's plural feature here, as this message is
       more of a programming error.  */
    error (_f ("TFM header of `%s' has only %u word (s)",
	       input_.name_string ().to_str0 (), header_length));

  info_.checksum = input_.get_U32 ();
  info_.design_size = get_U32_fix ();

  /* Although the coding scheme might be interesting to the caller, the
     font family and face byte probably aren't.  So we don't read them.  */
  info_.coding_scheme = header_length > 2
    ? get_bcpl_string () : "unspecified";

}

/* Although TFM files are only usable by TeX if they have at least seven
   parameters, that is not a requirement of the file format itself, so
   we don't impose it.  And they can have many more than seven, of
   course.  We do impose a limit of TFM_MAX_FONT_PARAMETERS.  We assume
   that `tfm_header' has already been filled in.  */

void
Tex_font_metric_reader::read_params ()
{
  /* If we have no font parameters at all, we're done.  */
  if (header_.param_word_count == 0)
    return;

  //brrr
  /* Move to the beginning of the parameter table in the file.  */
  input_.seek_str0 (-4 * header_.param_word_count);

  /* It's unlikely but possible that this TFM file has more fontdimens
     than we can deal with.  */
  if (header_.param_word_count > TFM_MAX_FONTDIMENS)
    {
      warning (_f ("%s: TFM file has %u parameters, which is more than the %u I can handle",
		   input_.name_string ().to_str0 (),
		   header_.param_word_count,
		   TFM_MAX_FONTDIMENS));
      header_.param_word_count = TFM_MAX_FONTDIMENS;
    }

  /* The first parameter is different than all the rest, because it
     isn't scaled by the design size.  */
  info_.parameters[ (TFM_SLANT_PARAMETER) - 1] = get_U32_fix ();

  for (Char_code i = 2; i <= header_.param_word_count; i++)
    info_.parameters[i - 1] = get_U32_fix_scaled ();

}

/* Read every character in the TFM file, storing the result in the
   static `tfm_char_table'.  We return a copy of that variable.  */

void
Tex_font_metric_reader::read_char_metrics ()
{
  for (int i = info_.first_charcode; i <= info_.last_charcode; i++)
    {
      Tex_font_char_metric tfm_char = read_char_metric (i);
      if (tfm_char.exists_b_)
	ascii_to_metric_idx_[tfm_char.code_] = char_metrics_.size ();
      char_metrics_.push (tfm_char);
    }
}

/* Read the character CODE.  If the character doesn't exist, return
   NULL.  If it does, save the information in `tfm_char_table', as well
   as returning it.  */

Tex_font_char_metric
Tex_font_metric_reader::read_char_metric (Char_code code)
{
  Tex_font_char_metric tfm_char;

  /* If the character is outside the declared bounds in the file, don't
     try to read it. */
  if (code < info_.first_charcode || code > info_.last_charcode)
    return tfm_char;
  
  //brr
  /* Move to the appropriate place in the `char_info' array.  */
  input_.seek_str0 (header_.char_info_pos + (code - info_.first_charcode) * 4);

  /* Read the character.  */
  tfm_char = read_char ();

  if (tfm_char.exists_b_)
    tfm_char.code_ = code;

  return tfm_char;
}


/* We assume we are positioned at the beginning of a `char_info' word.
   We read that word to get the indexes into the dimension tables; then
   we go read the tables to get the values (if the character exists).  */

Tex_font_char_metric
Tex_font_metric_reader::read_char ()
{
  /* Read the char_info word.  */
  U8 width_index = input_.get_U8 ();

  U8 packed;
  packed = input_.get_U8 ();
  U8 height_index = (packed & 0xf0) >> 4;
  U8 depth_index = packed & 0x0f;

  packed = input_.get_U8 ();
  U8 italic_correction_index = (packed & 0xfc) >> 6;
  U8 tag = packed & 0x3;

  U8 remainder = input_.get_U8 ();

  Tex_font_char_metric tfm_char;

#define GET_CHAR_DIMEN(d) \
   if (d##_index != 0) \
     { \
       input_.seek_str0 (header_. d##_pos + d##_index*4); \
       tfm_char.d##_fix_ = input_.get_U32 (); \
       tfm_char.d##_ = fix_to_real (tfm_char.d##_fix_) \
                      * info_.design_size; \
     }

  GET_CHAR_DIMEN (width);
  GET_CHAR_DIMEN (height);
  GET_CHAR_DIMEN (depth);
  GET_CHAR_DIMEN (italic_correction);

  /* The other condition for a character existing is that it be between
     the first and last character codes given in the header.  We've
     already assumed that's true (or we couldn't be positioned at a
     `char_info_word').  */
  tfm_char.exists_b_ = width_index != 0;

  if (tag == 1)
    {
      input_.seek_str0 (header_.lig_kern_pos + remainder * 4);
      read_lig_kern_program (&tfm_char.ligatures_, &tfm_char.kerns_);
    }

  /* We don't handle the other tags.  */
  return tfm_char;
}

/* Read a ligature/kern program at the current position, storing the
   result into *LIGATURE and *KERN.  We don't distinguish all the kinds
   of ligatures that Metafont can output.  */

#define STOP_FLAG 128
#define KERN_FLAG 128

void
Tex_font_metric_reader::read_lig_kern_program (Array <Tfm_ligature>* ligatures, Array <Tfm_kern>* kerns)
{
  bool end_b;

  do
    {
      end_b = input_.get_U8 () >= STOP_FLAG;

      U8 next_char = input_.get_U8 ();
      bool kern_step_b = input_.get_U8 () >= KERN_FLAG;
      U8 remainder = input_.get_U8 ();


      if (kern_step_b)
	{
	  Tfm_kern kern_element;
	  kern_element.character = next_char;

	  char const* old_pos = input_.pos_str0 ();
	  input_.seek_str0 (header_.kern_pos + remainder * 4);
	  kern_element.kern = get_U32_fix_scaled ();
	  input_.set_pos (old_pos);

	  kerns->push (kern_element);

	}
      else
	{
	  Tfm_ligature ligature_element;
	  ligature_element.character = next_char;
	  ligature_element.ligature = remainder;
	  ligatures->push (ligature_element);

	}
  } while (!end_b);
}

