/***************************************************************************/

/*                                                                         */

/*  ftzopen.h                                                              */

/*                                                                         */

/*    FreeType support for .Z compressed files.                            */

/*                                                                         */

/*  This optional component relies on NetBSD's zopen().  It should mainly  */

/*  be used to parse compressed PCF fonts, as found with many X11 server   */

/*  distributions.                                                         */

/*                                                                         */

/*  Copyright 2005, 2006, 2007, 2008 by David Turner.                      */

/*                                                                         */

/*  This file is part of the FreeType project, and may only be used,       */

/*  modified, and distributed under the terms of the FreeType project      */

/*  license, LICENSE.TXT.  By continuing to use, modify, or distribute     */

/*  this file you indicate that you have read the license and              */

/*  understand and accept it fully.                                        */

/*                                                                         */

/***************************************************************************/

#ifndef __FT_ZOPEN_H__

#define __FT_ZOPEN_H__

#include <ft2build.h>

#include FT_FREETYPE_H

  /*

   *  This is a complete re-implementation of the LZW file reader,

   *  since the old one was incredibly badly written, using

   *  400 KByte of heap memory before decompressing anything.

   *

   */

#define FT_LZW_IN_BUFF_SIZE        64

#define FT_LZW_DEFAULT_STACK_SIZE  64

#define LZW_INIT_BITS     9

#define LZW_MAX_BITS      16

#define LZW_CLEAR         256

#define LZW_FIRST         257

#define LZW_BIT_MASK      0x1f

#define LZW_BLOCK_MASK    0x80

#define LZW_MASK( n )     ( ( 1U << (n) ) - 1U )

  typedef enum  FT_LzwPhase_

  {

    FT_LZW_PHASE_START = 0,

    FT_LZW_PHASE_CODE,

    FT_LZW_PHASE_STACK,

    FT_LZW_PHASE_EOF

  } FT_LzwPhase;

  /*

   *  state of LZW decompressor

   *

   *  small technical note

   *  --------------------

   *

   *  We use a few tricks in this implementation that are explained here to

   *  ease debugging and maintenance.

   *

   *  - First of all, the `prefix' and `suffix' arrays contain the suffix

   *    and prefix for codes over 256; this means that

   *

   *      prefix_of(code) == state->prefix[code-256]

   *      suffix_of(code) == state->suffix[code-256]

   *

   *    Each prefix is a 16-bit code, and each suffix an 8-bit byte.

   *

   *    Both arrays are stored in a single memory block, pointed to by

   *    `state->prefix'.  This means that the following equality is always

   *    true:

   *

   *      state->suffix == (FT_Byte*)(state->prefix + state->prefix_size)

   *

   *    Of course, state->prefix_size is the number of prefix/suffix slots

   *    in the arrays, corresponding to codes 256..255+prefix_size.

   *

   *  - `free_ent' is the index of the next free entry in the `prefix'

   *    and `suffix' arrays.  This means that the corresponding `next free

   *    code' is really `256+free_ent'.

   *

   *    Moreover, `max_free' is the maximum value that `free_ent' can reach.

   *

   *    `max_free' corresponds to `(1 << max_bits) - 256'.  Note that this

   *    value is always <= 0xFF00, which means that both `free_ent' and

   *    `max_free' can be stored in an FT_UInt variable, even on 16-bit

   *    machines.

   *

   *    If `free_ent == max_free', you cannot add new codes to the

   *    prefix/suffix table.

   *

   *  - `num_bits' is the current number of code bits, starting at 9 and

   *    growing each time `free_ent' reaches the value of `free_bits'.  The

   *    latter is computed as follows

   *

   *      if num_bits < max_bits:

   *         free_bits = (1 << num_bits)-256

   *      else:

   *         free_bits = max_free + 1

   *

   *    Since the value of `max_free + 1' can never be reached by

   *    `free_ent', `num_bits' cannot grow larger than `max_bits'.

   */

  typedef struct  FT_LzwStateRec_

  {

    FT_LzwPhase  phase;

    FT_Int       in_eof;

    FT_Byte      buf_tab[16];

    FT_Int       buf_offset;

    FT_Int       buf_size;

    FT_Bool      buf_clear;

    FT_Offset    buf_total;

    FT_UInt      max_bits;    /* max code bits, from file header   */

    FT_Int       block_mode;  /* block mode flag, from file header */

    FT_UInt      max_free;    /* (1 << max_bits) - 256             */

    FT_UInt      num_bits;    /* current code bit number */

    FT_UInt      free_ent;    /* index of next free entry */

    FT_UInt      free_bits;   /* if reached by free_ent, increment num_bits */

    FT_UInt      old_code;

    FT_UInt      old_char;

    FT_UInt      in_code;

    FT_UShort*   prefix;      /* always dynamically allocated / reallocated */

    FT_Byte*     suffix;      /* suffix = (FT_Byte*)(prefix + prefix_size)  */

    FT_UInt      prefix_size; /* number of slots in `prefix' or `suffix'    */

    FT_Byte*     stack;       /* character stack */

    FT_UInt      stack_top;

    FT_Offset    stack_size;

    FT_Byte      stack_0[FT_LZW_DEFAULT_STACK_SIZE]; /* minimize heap alloc */

    FT_Stream    source;      /* source stream */

    FT_Memory    memory;

  } FT_LzwStateRec, *FT_LzwState;

  FT_LOCAL( void )

  ft_lzwstate_init( FT_LzwState  state,

                    FT_Stream    source );

  FT_LOCAL( void )

  ft_lzwstate_done( FT_LzwState  state );

  FT_LOCAL( void )

  ft_lzwstate_reset( FT_LzwState  state );

  FT_LOCAL( FT_ULong )

  ft_lzwstate_io( FT_LzwState  state,

                  FT_Byte*     buffer,

                  FT_ULong     out_size );

/* */

#endif /* __FT_ZOPEN_H__ */

/* END */