87 lines
3.2 KiB
C
87 lines
3.2 KiB
C
/*
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* stdenc.h
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*
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* Defines for the standard encoder
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*/
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// Size of hash table for std encoder
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#define STD_ENCODER_HASH_TABLE_SIZE 8192
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#define STD_ENCODER_HASH_MASK (STD_ENCODER_HASH_TABLE_SIZE-1)
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#define STD_ENCODER_HASH_SHIFT 5
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#define STD_ENCODER_RECALCULATE_HASH(loc) \
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(((window[loc] << (2*STD_ENCODER_HASH_SHIFT)) ^ \
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(window[loc+1] << STD_ENCODER_HASH_SHIFT) ^ \
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(window[loc+2])) & STD_ENCODER_HASH_MASK)
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// Maximum number of item we allow; this must be <= 65534, since this doesn't include
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// freq[END_OF_BLOCK_CODE] = 1, which brings us to 65535; any more than this would make
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// the frequency counts overflow, since they are stored in ushort's
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// Note that this number does not affect the memory requirements in any way; that is
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// determined by LIT_DIST_BUFFER_SIZE
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// -8 for some slack (not really necessary)
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#define STD_ENCODER_MAX_ITEMS (65534-8)
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// Size of the literal/distance buffer
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#define STD_ENCODER_LIT_DIST_BUFFER_SIZE 32768
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// Don't take a match 3 further away than this
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// BUGBUG 4K seems a little close, but does do a marginally better job than 8K on
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// an 80K html file, so might as well leave it be
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#define STD_ENCODER_MATCH3_DIST_THRESHOLD 4096
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// Standard encoder context
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typedef struct std_encoder
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{
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// history window
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BYTE window[2*WINDOW_SIZE + MAX_MATCH + 4];
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// next most recent occurance of chars with same hash value
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t_search_node prev[WINDOW_SIZE + MAX_MATCH];
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// hash table to find most recent occurance of chars with same hash value
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t_search_node lookup[STD_ENCODER_HASH_TABLE_SIZE];
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// recording buffer for recording literals and distances
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BYTE lit_dist_buffer[STD_ENCODER_LIT_DIST_BUFFER_SIZE];
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unsigned long recording_bitbuf;
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unsigned long recording_bitcount;
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BYTE * recording_bufptr;
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short recording_dist_tree_table[REC_DISTANCES_DECODING_TABLE_SIZE];
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short recording_dist_tree_left[2*MAX_DIST_TREE_ELEMENTS];
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short recording_dist_tree_right[2*MAX_DIST_TREE_ELEMENTS];
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BYTE recording_dist_tree_len[MAX_DIST_TREE_ELEMENTS];
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USHORT recording_dist_tree_code[MAX_DIST_TREE_ELEMENTS];
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short recording_literal_tree_table[REC_LITERALS_DECODING_TABLE_SIZE];
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short recording_literal_tree_left[2*MAX_LITERAL_TREE_ELEMENTS];
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short recording_literal_tree_right[2*MAX_LITERAL_TREE_ELEMENTS];
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BYTE recording_literal_tree_len[MAX_LITERAL_TREE_ELEMENTS];
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USHORT recording_literal_tree_code[MAX_LITERAL_TREE_ELEMENTS];
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// literal trees
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USHORT literal_tree_freq[2*MAX_LITERAL_TREE_ELEMENTS];
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USHORT literal_tree_code[MAX_LITERAL_TREE_ELEMENTS];
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BYTE literal_tree_len[MAX_LITERAL_TREE_ELEMENTS];
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// dist trees
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USHORT dist_tree_freq[2*MAX_DIST_TREE_ELEMENTS];
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USHORT dist_tree_code[MAX_DIST_TREE_ELEMENTS];
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BYTE dist_tree_len[MAX_DIST_TREE_ELEMENTS];
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} t_std_encoder;
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