/**************************************************************************** * * 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 (C) 2005-2023 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 FTZOPEN_H_ #define FTZOPEN_H_ #include <freetype/freetype.h> FT_BEGIN_HEADER /* * 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 … #define FT_LZW_DEFAULT_STACK_SIZE … #define LZW_INIT_BITS … #define LZW_MAX_BITS … #define LZW_CLEAR … #define LZW_FIRST … #define LZW_BIT_MASK … #define LZW_BLOCK_MASK … #define LZW_MASK( n ) … 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'. */ 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 ); /* */ FT_END_HEADER #endif /* FTZOPEN_H_ */ /* END */
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