/src/freetype/src/lzw/ftzopen.h
https://bitbucket.org/cabalistic/ogredeps/ · C++ Header · 171 lines · 60 code · 32 blank · 79 comment · 0 complexity · 07a957315bd99dcc8a1fada6419f712b MD5 · raw file
- /***************************************************************************/
- /* */
- /* 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 */