decompress_common: switch to subtables for Huffman decoding
[wimlib] / src / lzms_decompress.c
index 1ea0ac6..4791054 100644 (file)
@@ -5,7 +5,7 @@
  */
 
 /*
- * Copyright (C) 2013, 2014, 2015 Eric Biggers
+ * Copyright (C) 2013-2016 Eric Biggers
  *
  * This file is free software; you can redistribute it and/or modify it under
  * the terms of the GNU Lesser General Public License as published by the Free
 
 /* The TABLEBITS values can be changed; they only affect decoding speed.  */
 #define LZMS_LITERAL_TABLEBITS         10
-#define LZMS_LENGTH_TABLEBITS          10
-#define LZMS_LZ_OFFSET_TABLEBITS       10
-#define LZMS_DELTA_OFFSET_TABLEBITS    10
-#define LZMS_DELTA_POWER_TABLEBITS     8
+#define LZMS_LENGTH_TABLEBITS          9
+#define LZMS_LZ_OFFSET_TABLEBITS       11
+#define LZMS_DELTA_OFFSET_TABLEBITS    11
+#define LZMS_DELTA_POWER_TABLEBITS     7
 
 struct lzms_range_decoder {
 
@@ -323,33 +323,28 @@ struct lzms_decompressor {
 
        struct lzms_probabilites probs;
 
-       u16 literal_decode_table[(1 << LZMS_LITERAL_TABLEBITS) +
-                                (2 * LZMS_NUM_LITERAL_SYMS)]
-               _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+       DECODE_TABLE(literal_decode_table, LZMS_NUM_LITERAL_SYMS,
+                    LZMS_LITERAL_TABLEBITS, LZMS_MAX_CODEWORD_LENGTH);
        u32 literal_freqs[LZMS_NUM_LITERAL_SYMS];
        struct lzms_huffman_rebuild_info literal_rebuild_info;
 
-       u16 lz_offset_decode_table[(1 << LZMS_LZ_OFFSET_TABLEBITS) +
-                                  ( 2 * LZMS_MAX_NUM_OFFSET_SYMS)]
-               _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+       DECODE_TABLE(lz_offset_decode_table, LZMS_MAX_NUM_OFFSET_SYMS,
+                    LZMS_LZ_OFFSET_TABLEBITS, LZMS_MAX_CODEWORD_LENGTH);
        u32 lz_offset_freqs[LZMS_MAX_NUM_OFFSET_SYMS];
        struct lzms_huffman_rebuild_info lz_offset_rebuild_info;
 
-       u16 length_decode_table[(1 << LZMS_LENGTH_TABLEBITS) +
-                               (2 * LZMS_NUM_LENGTH_SYMS)]
-               _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+       DECODE_TABLE(length_decode_table, LZMS_NUM_LENGTH_SYMS,
+                    LZMS_LENGTH_TABLEBITS, LZMS_MAX_CODEWORD_LENGTH);
        u32 length_freqs[LZMS_NUM_LENGTH_SYMS];
        struct lzms_huffman_rebuild_info length_rebuild_info;
 
-       u16 delta_offset_decode_table[(1 << LZMS_DELTA_OFFSET_TABLEBITS) +
-                                     (2 * LZMS_MAX_NUM_OFFSET_SYMS)]
-               _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+       DECODE_TABLE(delta_offset_decode_table, LZMS_MAX_NUM_OFFSET_SYMS,
+                    LZMS_DELTA_OFFSET_TABLEBITS, LZMS_MAX_CODEWORD_LENGTH);
        u32 delta_offset_freqs[LZMS_MAX_NUM_OFFSET_SYMS];
        struct lzms_huffman_rebuild_info delta_offset_rebuild_info;
 
-       u16 delta_power_decode_table[(1 << LZMS_DELTA_POWER_TABLEBITS) +
-                                    (2 * LZMS_NUM_DELTA_POWER_SYMS)]
-               _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+       DECODE_TABLE(delta_power_decode_table, LZMS_NUM_DELTA_POWER_SYMS,
+                    LZMS_DELTA_POWER_TABLEBITS, LZMS_MAX_CODEWORD_LENGTH);
        u32 delta_power_freqs[LZMS_NUM_DELTA_POWER_SYMS];
        struct lzms_huffman_rebuild_info delta_power_rebuild_info;
 
@@ -594,43 +589,36 @@ lzms_rebuild_huffman_code(struct lzms_huffman_rebuild_info *rebuild_info)
        lzms_dilute_symbol_frequencies(rebuild_info->freqs, rebuild_info->num_syms);
 }
 
+/* XXX: mostly copied from read_huffsym() in decompress_common.h because LZMS
+ * needs its own bitstream */
 static inline unsigned
 lzms_decode_huffman_symbol(struct lzms_input_bitstream *is, u16 decode_table[],
                           unsigned table_bits, u32 freqs[],
                           struct lzms_huffman_rebuild_info *rebuild_info)
 {
-       unsigned key_bits;
        unsigned entry;
-       unsigned sym;
+       unsigned symbol;
+       unsigned length;
 
        lzms_ensure_bits(is, LZMS_MAX_CODEWORD_LENGTH);
 
-       /* Index the decode table by the next table_bits bits of the input.  */
-       key_bits = lzms_peek_bits(is, table_bits);
-       entry = decode_table[key_bits];
-       if (likely(entry < 0xC000)) {
-               /* Fast case: The decode table directly provided the symbol and
-                * codeword length.  The low 11 bits are the symbol, and the
-                * high 5 bits are the codeword length.  */
-               lzms_remove_bits(is, entry >> 11);
-               sym = entry & 0x7FF;
-       } else {
-               /* Slow case: The codeword for the symbol is longer than
-                * table_bits, so the symbol does not have an entry directly in
-                * the first (1 << table_bits) entries of the decode table.
-                * Traverse the appropriate binary tree bit-by-bit in order to
-                * decode the symbol.  */
+       entry = decode_table[lzms_peek_bits(is, table_bits)];
+       symbol = entry >> DECODE_TABLE_SYMBOL_SHIFT;
+       length = entry & DECODE_TABLE_LENGTH_MASK;
+
+       if (entry >= (1U << (table_bits + DECODE_TABLE_SYMBOL_SHIFT))) {
                lzms_remove_bits(is, table_bits);
-               do {
-                       key_bits = (entry & 0x3FFF) + lzms_pop_bits(is, 1);
-               } while ((entry = decode_table[key_bits]) >= 0xC000);
-               sym = entry;
+               entry = decode_table[symbol + lzms_peek_bits(is, length)];
+               symbol = entry >> DECODE_TABLE_SYMBOL_SHIFT;
+               length = entry & DECODE_TABLE_LENGTH_MASK;
        }
 
-       freqs[sym]++;
+       lzms_remove_bits(is, length);
+
+       freqs[symbol]++;
        if (--rebuild_info->num_syms_until_rebuild == 0)
                lzms_rebuild_huffman_code(rebuild_info);
-       return sym;
+       return symbol;
 }
 
 static inline unsigned