decompress_common: switch to subtables for Huffman decoding

diff --git a/include/wimlib/compiler.h b/include/wimlib/compiler.h
index a43bb769fdce9c752e3a75920c6ce48744133579..9f53e192fc52796e2837c016a2f20b479e05d1cf 100644 (file)
--- a/include/wimlib/compiler.h
+++ b/include/wimlib/compiler.h
@@ -192,6 +192,10 @@
 #  define STATIC_ASSERT(expr)  ((void)sizeof(char[1 - 2 * !(expr)]))
 #endif
 
 #  define STATIC_ASSERT(expr)  ((void)sizeof(char[1 - 2 * !(expr)]))
 #endif
 

+/* STATIC_ASSERT_ZERO() - verify the truth of an expression at compilation time
+ * and also produce a result of value '0' to be used in constant expressions */
+#define STATIC_ASSERT_ZERO(expr) ((int)sizeof(char[-!(expr)]))
+

 #define CONCAT_IMPL(s1, s2)    s1##s2
 
 /* CONCAT() - concatenate two tokens at preprocessing time.  */
 #define CONCAT_IMPL(s1, s2)    s1##s2
 
 /* CONCAT() - concatenate two tokens at preprocessing time.  */

diff --git a/include/wimlib/decompress_common.h b/include/wimlib/decompress_common.h
index c3016475b2c07f812d6d2285443e51839545c83f..d396120763d917582ff29a30b9cd1ebd2e731a4c 100644 (file)
--- a/include/wimlib/decompress_common.h
+++ b/include/wimlib/decompress_common.h
@@ -29,6 +29,10 @@
 #include "wimlib/types.h"
 #include "wimlib/unaligned.h"
 
 #include "wimlib/types.h"
 #include "wimlib/unaligned.h"
 

+/******************************************************************************/
+/*                   Input bitstream for XPRESS and LZX                       */
+/*----------------------------------------------------------------------------*/
+

 /* Structure that encapsulates a block of in-memory data being interpreted as a
  * stream of bits, optionally with interwoven literal bytes.  Bits are assumed
  * to be stored in little endian 16-bit coding units, with the bits ordered high
 /* Structure that encapsulates a block of in-memory data being interpreted as a
  * stream of bits, optionally with interwoven literal bytes.  Bits are assumed
  * to be stored in little endian 16-bit coding units, with the bits ordered high


@@ -192,76 +196,217 @@ bitstream_align(struct input_bitstream *is)
        is->bitbuf = 0;
 }
 
        is->bitbuf = 0;
 }
 

-/* Needed alignment of decode_table parameter to make_huffman_decode_table().
- *
- * Reason: We may fill the entries with SSE instructions without worrying
- * about dealing with the unaligned case.  */
+/******************************************************************************/
+/*                             Huffman decoding                               */
+/*----------------------------------------------------------------------------*/
+
+/*
+ * Required alignment for the Huffman decode tables.  We require this alignment
+ * so that we can fill the entries with vector or word instructions and not have
+ * to deal with misaligned buffers.
+ */

 #define DECODE_TABLE_ALIGNMENT 16
 
 #define DECODE_TABLE_ALIGNMENT 16
 

-/* Maximum supported symbol count for make_huffman_decode_table().
+/*
+ * Each decode table entry is 16 bits divided into two fields: 'symbol' (high 12
+ * bits) and 'length' (low 4 bits).  The precise meaning of these fields depends
+ * on the type of entry:

  *
  *

- * Reason: In direct mapping entries, we store the symbol in 11 bits.  */
-#define DECODE_TABLE_MAX_SYMBOLS 2048
-
-/* Maximum supported table bits for make_huffman_decode_table().
+ * Root table entries which are *not* subtable pointers:
+ *     symbol: symbol to decode
+ *     length: codeword length in bits
+ *
+ * Root table entries which are subtable pointers:
+ *     symbol: index of start of subtable
+ *     length: number of bits with which the subtable is indexed

  *
  *

- * Reason: In internal binary tree nodes, offsets are encoded in 14 bits.
- * But the real limit is 13, because we allocate entries past the end of
- * the direct lookup part of the table for binary tree nodes.  (Note: if
- * needed this limit could be removed by encoding the offsets relative to
- * &decode_table[1 << table_bits].)  */
-#define DECODE_TABLE_MAX_TABLE_BITS 13
-
-/* Maximum supported codeword length for make_huffman_decode_table().
+ * Subtable entries:
+ *     symbol: symbol to decode
+ *     length: codeword length in bits, minus the number of bits with which the
+ *             root table is indexed
+ */
+#define DECODE_TABLE_SYMBOL_SHIFT  4
+#define DECODE_TABLE_MAX_SYMBOL           ((1 << (16 - DECODE_TABLE_SYMBOL_SHIFT)) - 1)
+#define DECODE_TABLE_MAX_LENGTH    ((1 << DECODE_TABLE_SYMBOL_SHIFT) - 1)
+#define DECODE_TABLE_LENGTH_MASK   DECODE_TABLE_MAX_LENGTH
+#define MAKE_DECODE_TABLE_ENTRY(symbol, length) \
+       (((symbol) << DECODE_TABLE_SYMBOL_SHIFT) | (length))
+
+/*
+ * Read and return the next Huffman-encoded symbol from the given bitstream
+ * using the given decode table.

  *
  *

- * Reason: In direct mapping entries, we encode the codeword length in 5
- * bits, and the top 2 bits can't both be set because that has special
- * meaning.  */
-#define DECODE_TABLE_MAX_CODEWORD_LEN 23
-
-/* Reads and returns the next Huffman-encoded symbol from a bitstream.  If the
- * input data is exhausted, the Huffman symbol is decoded as if the missing bits
- * are all zeroes.
+ * If the input data is exhausted, then the Huffman symbol will be decoded as if
+ * the missing bits were all zeroes.

  *
  * XXX: This is mostly duplicated in lzms_decode_huffman_symbol() in
  *
  * XXX: This is mostly duplicated in lzms_decode_huffman_symbol() in

- * lzms_decompress.c.  */
+ * lzms_decompress.c; keep them in sync!
+ */

 static inline unsigned
 static inline unsigned

-read_huffsym(struct input_bitstream *istream, const u16 decode_table[],
+read_huffsym(struct input_bitstream *is, const u16 decode_table[],

             unsigned table_bits, unsigned max_codeword_len)
 {
        unsigned entry;
             unsigned table_bits, unsigned max_codeword_len)
 {
        unsigned entry;

-       unsigned key_bits;
-
-       bitstream_ensure_bits(istream, max_codeword_len);
-
-       /* Index the decode table by the next table_bits bits of the input.  */
-       key_bits = bitstream_peek_bits(istream, 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.  */
-               bitstream_remove_bits(istream, entry >> 11);
-               return 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 to decode the symbol.  */
-               bitstream_remove_bits(istream, table_bits);
-               do {
-                       key_bits = (entry & 0x3FFF) + bitstream_pop_bits(istream, 1);
-               } while ((entry = decode_table[key_bits]) >= 0xC000);
-               return entry;
+       unsigned symbol;
+       unsigned length;
+
+       /* Preload the bitbuffer with 'max_codeword_len' bits so that we're
+        * guaranteed to be able to fully decode a codeword. */
+       bitstream_ensure_bits(is, max_codeword_len);
+
+       /* Index the root table by the next 'table_bits' bits of input. */
+       entry = decode_table[bitstream_peek_bits(is, table_bits)];
+
+       /* Extract the "symbol" and "length" from the entry. */
+       symbol = entry >> DECODE_TABLE_SYMBOL_SHIFT;
+       length = entry & DECODE_TABLE_LENGTH_MASK;
+
+       /* If the root table is indexed by the full 'max_codeword_len' bits,
+        * then there cannot be any subtables, and this will be known at compile
+        * time.  Otherwise, we must check whether the decoded symbol is really
+        * a subtable pointer.  If so, we must discard the bits with which the
+        * root table was indexed, then index the subtable by the next 'length'
+        * bits of input to get the real entry. */
+       if (max_codeword_len > table_bits &&
+           entry >= (1U << (table_bits + DECODE_TABLE_SYMBOL_SHIFT)))
+       {
+               /* Subtable required */
+               bitstream_remove_bits(is, table_bits);
+               entry = decode_table[symbol + bitstream_peek_bits(is, length)];
+               symbol = entry >> DECODE_TABLE_SYMBOL_SHIFT;
+               length = entry & DECODE_TABLE_LENGTH_MASK;

        }
        }

+
+       /* Discard the bits (or the remaining bits, if a subtable was required)
+        * of the codeword. */
+       bitstream_remove_bits(is, length);
+
+       /* Return the decoded symbol. */
+       return symbol;

 }
 
 }
 

+/*
+ * The DECODE_TABLE_ENOUGH() macro evaluates to the maximum number of decode
+ * table entries, including all subtable entries, that may be required for
+ * decoding a given Huffman code.  This depends on three parameters:
+ *
+ *     num_syms: the maximum number of symbols in the code
+ *     table_bits: the number of bits with which the root table will be indexed
+ *     max_codeword_len: the maximum allowed codeword length in the code
+ *
+ * Given these parameters, the utility program 'enough' from zlib, when passed
+ * the three arguments 'num_syms', 'table_bits', and 'max_codeword_len', will
+ * compute the maximum number of entries required.  This has already been done
+ * for the combinations we need and incorporated into the macro below so that
+ * the mapping can be done at compilation time.  If an unknown combination is
+ * used, then a compilation error will result.  To fix this, use 'enough' to
+ * find the missing value and add it below.  If that still doesn't fix the
+ * compilation error, then most likely a constraint would be violated by the
+ * requested parameters, so they cannot be used, at least without other changes
+ * to the decode table --- see DECODE_TABLE_SIZE().
+ */
+#define DECODE_TABLE_ENOUGH(num_syms, table_bits, max_codeword_len) ( \
+       ((num_syms) == 8 && (table_bits) == 7 && (max_codeword_len) == 15) ? 128 : \
+       ((num_syms) == 8 && (table_bits) == 5 && (max_codeword_len) == 7) ? 36 : \
+       ((num_syms) == 8 && (table_bits) == 6 && (max_codeword_len) == 7) ? 66 : \
+       ((num_syms) == 8 && (table_bits) == 7 && (max_codeword_len) == 7) ? 128 : \
+       ((num_syms) == 20 && (table_bits) == 5 && (max_codeword_len) == 15) ? 1062 : \
+       ((num_syms) == 20 && (table_bits) == 6 && (max_codeword_len) == 15) ? 582 : \
+       ((num_syms) == 20 && (table_bits) == 7 && (max_codeword_len) == 15) ? 390 : \
+       ((num_syms) == 54 && (table_bits) == 9 && (max_codeword_len) == 15) ? 618 : \
+       ((num_syms) == 54 && (table_bits) == 10 && (max_codeword_len) == 15) ? 1098 : \
+       ((num_syms) == 249 && (table_bits) == 9 && (max_codeword_len) == 16) ? 878 : \
+       ((num_syms) == 249 && (table_bits) == 10 && (max_codeword_len) == 16) ? 1326 : \
+       ((num_syms) == 249 && (table_bits) == 11 && (max_codeword_len) == 16) ? 2318 : \
+       ((num_syms) == 256 && (table_bits) == 9 && (max_codeword_len) == 15) ? 822 : \
+       ((num_syms) == 256 && (table_bits) == 10 && (max_codeword_len) == 15) ? 1302 : \
+       ((num_syms) == 256 && (table_bits) == 11 && (max_codeword_len) == 15) ? 2310 : \
+       ((num_syms) == 512 && (table_bits) == 10 && (max_codeword_len) == 15) ? 1558 : \
+       ((num_syms) == 512 && (table_bits) == 11 && (max_codeword_len) == 15) ? 2566 : \
+       ((num_syms) == 512 && (table_bits) == 12 && (max_codeword_len) == 15) ? 4606 : \
+       ((num_syms) == 656 && (table_bits) == 10 && (max_codeword_len) == 16) ? 1734 : \
+       ((num_syms) == 656 && (table_bits) == 11 && (max_codeword_len) == 16) ? 2726 : \
+       ((num_syms) == 656 && (table_bits) == 12 && (max_codeword_len) == 16) ? 4758 : \
+       ((num_syms) == 799 && (table_bits) == 9 && (max_codeword_len) == 15) ? 1366 : \
+       ((num_syms) == 799 && (table_bits) == 10 && (max_codeword_len) == 15) ? 1846 : \
+       ((num_syms) == 799 && (table_bits) == 11 && (max_codeword_len) == 15) ? 2854 : \
+       -1)
+
+/* Wrapper around DECODE_TABLE_ENOUGH() that does additional compile-time
+ * validation. */
+#define DECODE_TABLE_SIZE(num_syms, table_bits, max_codeword_len) (    \
+                                                                       \
+       /* All values must be positive. */                              \
+       STATIC_ASSERT_ZERO((num_syms) > 0) +                            \
+       STATIC_ASSERT_ZERO((table_bits) > 0) +                          \
+       STATIC_ASSERT_ZERO((max_codeword_len) > 0) +                    \
+                                                                       \
+       /* There cannot be more symbols than possible codewords. */     \
+       STATIC_ASSERT_ZERO((num_syms) <= 1U << (max_codeword_len)) +    \
+                                                                       \
+       /* There is no reason for the root table to be indexed with
+        * more bits than the maximum codeword length. */               \
+       STATIC_ASSERT_ZERO((table_bits) <= (max_codeword_len)) +        \
+                                                                       \
+       /* The maximum symbol value must fit in the 'symbol' field. */  \
+       STATIC_ASSERT_ZERO((num_syms) - 1 <= DECODE_TABLE_MAX_SYMBOL) + \
+                                                                       \
+       /* The maximum codeword length in the root table must fit in
+        * the 'length' field. */                                       \
+       STATIC_ASSERT_ZERO((table_bits) <= DECODE_TABLE_MAX_LENGTH) +   \
+                                                                       \
+       /* The maximum codeword length in a subtable must fit in the
+        * 'length' field. */                                           \
+       STATIC_ASSERT_ZERO((max_codeword_len) - (table_bits) <=         \
+                          DECODE_TABLE_MAX_LENGTH) +                   \
+                                                                       \
+       /* The minimum subtable index must be greater than the maximum
+        * symbol value.  If this were not the case, then there would
+        * be no way to tell whether a given root table entry is a
+        * "subtable pointer" or not.  (An alternate solution would be
+        * to reserve a flag bit specifically for this purpose.) */     \
+       STATIC_ASSERT_ZERO((1U << table_bits) > (num_syms) - 1) +       \
+                                                                       \
+       /* The needed 'enough' value must have been defined. */         \
+       STATIC_ASSERT_ZERO(DECODE_TABLE_ENOUGH(                         \
+                               (num_syms), (table_bits),               \
+                               (max_codeword_len)) > 0) +              \
+                                                                       \
+       /* The maximum subtable index must fit in the 'symbol' field. */\
+       STATIC_ASSERT_ZERO(DECODE_TABLE_ENOUGH(                         \
+                               (num_syms), (table_bits),               \
+                               (max_codeword_len)) - 1 <=              \
+                                       DECODE_TABLE_MAX_SYMBOL) +      \
+                                                                       \
+       /* Finally, make the macro evaluate to the needed maximum
+        * number of decode table entries. */                           \
+       DECODE_TABLE_ENOUGH((num_syms), (table_bits),                   \
+                           (max_codeword_len))                         \
+)
+
+/*
+ * Declare the decode table for a Huffman code, given several compile-time
+ * constants that describe the code.  See DECODE_TABLE_ENOUGH() for details.
+ *
+ * Decode tables must be aligned to a DECODE_TABLE_ALIGNMENT-byte boundary.
+ * This implies that if a decode table is nested inside a dynamically allocated
+ * structure, then the outer structure must be allocated on a
+ * DECODE_TABLE_ALIGNMENT-byte aligned boundary as well.
+ */
+#define DECODE_TABLE(name, num_syms, table_bits, max_codeword_len) \
+       u16 name[DECODE_TABLE_SIZE((num_syms), (table_bits), \
+                                  (max_codeword_len))] \
+               _aligned_attribute(DECODE_TABLE_ALIGNMENT)
+

 extern int
 make_huffman_decode_table(u16 decode_table[], unsigned num_syms,
 extern int
 make_huffman_decode_table(u16 decode_table[], unsigned num_syms,

-                         unsigned num_bits, const u8 lens[],
+                         unsigned table_bits, const u8 lens[],

                          unsigned max_codeword_len);
 
                          unsigned max_codeword_len);
 

+/******************************************************************************/
+/*                             LZ match copying                               */
+/*----------------------------------------------------------------------------*/
+

 static inline void
 copy_word_unaligned(const void *src, void *dst)
 {
 static inline void
 copy_word_unaligned(const void *src, void *dst)
 {


@@ -269,19 +414,22 @@ copy_word_unaligned(const void *src, void *dst)
 }
 
 static inline machine_word_t
 }
 
 static inline machine_word_t

-repeat_byte(u8 b)
+repeat_u16(u16 b)

 {
 {

-       machine_word_t v;
+       machine_word_t v = b;

 
        STATIC_ASSERT(WORDBITS == 32 || WORDBITS == 64);
 
        STATIC_ASSERT(WORDBITS == 32 || WORDBITS == 64);

-
-       v = b;
-       v |= v << 8;

        v |= v << 16;
        v |= v << ((WORDBITS == 64) ? 32 : 0);
        return v;
 }
 
        v |= v << 16;
        v |= v << ((WORDBITS == 64) ? 32 : 0);
        return v;
 }
 

+static inline machine_word_t
+repeat_byte(u8 b)
+{
+       return repeat_u16(((u16)b << 8) | b);
+}
+

 /*
  * Copy an LZ77 match at (dst - offset) to dst.
  *
 /*
  * Copy an LZ77 match at (dst - offset) to dst.
  *

diff --git a/src/decompress_common.c b/src/decompress_common.c
index 973f467cc6e0c7ffe3a8bb557988f29e2f8bf8f7..fa605f0cc08b21b301fc641a3e43088fd805b6a2 100644 (file)
--- a/src/decompress_common.c
+++ b/src/decompress_common.c
@@ -5,7 +5,7 @@
  *
  * The following copying information applies to this specific source code file:
  *
  *
  * The following copying information applies to this specific source code file:
  *

- * Written in 2012-2015 by Eric Biggers <ebiggers3@gmail.com>
+ * Written in 2012-2016 by Eric Biggers <ebiggers3@gmail.com>

  *
  * To the extent possible under law, the author(s) have dedicated all copyright
  * and related and neighboring rights to this software to the public domain
  *
  * To the extent possible under law, the author(s) have dedicated all copyright
  * and related and neighboring rights to this software to the public domain


@@ -24,259 +24,202 @@
 #  include "config.h"
 #endif
 
 #  include "config.h"
 #endif
 

-#include "wimlib/decompress_common.h"
-

 #include <string.h>
 
 #include <string.h>
 

-#define USE_WORD_FILL
-
-#ifdef __GNUC__
-#  ifdef __SSE2__
-#    undef USE_WORD_FILL
-#    define USE_SSE2_FILL
-#    include <emmintrin.h>
-#  endif
+#ifdef __SSE2__
+#  include <emmintrin.h>

 #endif
 
 #endif
 

-/* Construct a direct mapping entry in the lookup table.  */
-#define MAKE_DIRECT_ENTRY(symbol, length) ((symbol) | ((length) << 11))
+#include "wimlib/decompress_common.h"

 
 /*
  * make_huffman_decode_table() -
  *
 
 /*
  * make_huffman_decode_table() -
  *

- * Build a decoding table for a canonical prefix code, or "Huffman code".
+ * Given an alphabet of symbols and the length of each symbol's codeword in a
+ * canonical prefix code, build a table for quickly decoding symbols that were
+ * encoded with that code.

  *
  *

- * This takes as input the length of the codeword for each symbol in the
- * alphabet and produces as output a table that can be used for fast
- * decoding of prefix-encoded symbols using read_huffsym().
+ * A _prefix code_ is an assignment of bitstrings called _codewords_ to symbols
+ * such that no whole codeword is a prefix of any other.  A prefix code might be
+ * a _Huffman code_, which means that it is an optimum prefix code for a given
+ * list of symbol frequencies and was generated by the Huffman algorithm.
+ * Although the prefix codes processed here will ordinarily be "Huffman codes",
+ * strictly speaking the decoder cannot know whether a given code was actually
+ * generated by the Huffman algorithm or not.

  *
  *

- * Strictly speaking, a canonical prefix code might not be a Huffman
- * code.  But this algorithm will work either way; and in fact, since
- * Huffman codes are defined in terms of symbol frequencies, there is no
- * way for the decompressor to know whether the code is a true Huffman
- * code or not until all symbols have been decoded.
+ * A prefix code is _canonical_ if and only if a longer codeword never
+ * lexicographically precedes a shorter codeword, and the lexicographic ordering
+ * of codewords of equal length is the same as the lexicographic ordering of the
+ * corresponding symbols.  The advantage of using a canonical prefix code is
+ * that the codewords can be reconstructed from only the symbol => codeword
+ * length mapping.  This eliminates the need to transmit the codewords
+ * explicitly.  Instead, they can be enumerated in lexicographic order after
+ * sorting the symbols primarily by increasing codeword length and secondarily
+ * by increasing symbol value.

  *
  *

- * Because the prefix code is assumed to be "canonical", it can be
- * reconstructed directly from the codeword lengths.  A prefix code is
- * canonical if and only if a longer codeword never lexicographically
- * precedes a shorter codeword, and the lexicographic ordering of
- * codewords of the same length is the same as the lexicographic ordering
- * of the corresponding symbols.  Consequently, we can sort the symbols
- * primarily by codeword length and secondarily by symbol value, then
- * reconstruct the prefix code by generating codewords lexicographically
- * in that order.
+ * However, the decoder's real goal is to decode symbols with the code, not just
+ * generate the list of codewords.  Consequently, this function directly builds
+ * a table for efficiently decoding symbols using the code.  The basic idea is
+ * that given the next 'max_codeword_len' bits of input, the decoder can look up
+ * the next decoded symbol by indexing a table containing '2^max_codeword_len'
+ * entries.  A codeword with length 'max_codeword_len' will have exactly one
+ * entry in this table, whereas a codeword shorter than 'max_codeword_len' will
+ * have multiple entries in this table.  Precisely, a codeword of length 'n'
+ * will have '2^(max_codeword_len - n)' entries.  The index of each such entry,
+ * considered as a bitstring of length 'max_codeword_len', will contain the
+ * corresponding codeword as a prefix.

  *
  *

- * This function does not, however, generate the prefix code explicitly.
- * Instead, it directly builds a table for decoding symbols using the
- * code.  The basic idea is this: given the next 'max_codeword_len' bits
- * in the input, we can look up the decoded symbol by indexing a table
- * containing 2**max_codeword_len entries.  A codeword with length
- * 'max_codeword_len' will have exactly one entry in this table, whereas
- * a codeword shorter than 'max_codeword_len' will have multiple entries
- * in this table.  Precisely, a codeword of length n will be represented
- * by 2**(max_codeword_len - n) entries in this table.  The 0-based index
- * of each such entry will contain the corresponding codeword as a prefix
- * when zero-padded on the left to 'max_codeword_len' binary digits.
+ * That's the basic idea, but we extend it in two ways:

  *
  *

- * That's the basic idea, but we implement two optimizations regarding
- * the format of the decode table itself:
+ * - Often the maximum codeword length is too long for it to be efficient to
+ *   build the full decode table whenever a new code is used.  Instead, we build
+ *   a "root" table using only '2^table_bits' entries, where 'table_bits <=
+ *   max_codeword_len'.  Then, a lookup of 'table_bits' bits produces either a
+ *   symbol directly (for codewords not longer than 'table_bits'), or the index
+ *   of a subtable which must be indexed with additional bits of input to fully
+ *   decode the symbol (for codewords longer than 'table_bits').

  *
  *

- * - For many compression formats, the maximum codeword length is too
- *   long for it to be efficient to build the full decoding table
- *   whenever a new prefix code is used.  Instead, we can build the table
- *   using only 2**table_bits entries, where 'table_bits' is some number
- *   less than or equal to 'max_codeword_len'.  Then, only codewords of
- *   length 'table_bits' and shorter can be directly looked up.  For
- *   longer codewords, the direct lookup instead produces the root of a
- *   binary tree.  Using this tree, the decoder can do traditional
- *   bit-by-bit decoding of the remainder of the codeword.  Child nodes
- *   are allocated in extra entries at the end of the table; leaf nodes
- *   contain symbols.  Note that the long-codeword case is, in general,
- *   not performance critical, since in Huffman codes the most frequently
- *   used symbols are assigned the shortest codeword lengths.
+ * - Whenever the decoder decodes a symbol, it needs to know the codeword length
+ *   so that it can remove the appropriate number of input bits.  The obvious
+ *   solution would be to simply retain the codeword lengths array and use the
+ *   decoded symbol as an index into it.  However, that would require two array
+ *   accesses when decoding each symbol.  Our strategy is to instead store the
+ *   codeword length directly in the decode table entry along with the symbol.

  *
  *

- * - When we decode a symbol using a direct lookup of the table, we still
- *   need to know its length so that the bitstream can be advanced by the
- *   appropriate number of bits.  The simple solution is to simply retain
- *   the 'lens' array and use the decoded symbol as an index into it.
- *   However, this requires two separate array accesses in the fast path.
- *   The optimization is to store the length directly in the decode
- *   table.  We use the bottom 11 bits for the symbol and the top 5 bits
- *   for the length.  In addition, to combine this optimization with the
- *   previous one, we introduce a special case where the top 2 bits of
- *   the length are both set if the entry is actually the root of a
- *   binary tree.
+ * See MAKE_DECODE_TABLE_ENTRY() for full details on the format of decode table
+ * entries, and see read_huffsym() for full details on how symbols are decoded.

  *
  * @decode_table:
  *
  * @decode_table:

- *     The array in which to create the decoding table.  This must be
- *     16-byte aligned and must have a length of at least
- *     ((2**table_bits) + 2 * num_syms) entries.  This is permitted to
- *     alias @lens, since all information from @lens is consumed before
-*      anything is written to @decode_table.
+ *     The array in which to build the decode table.  This must have been
+ *     declared by the DECODE_TABLE() macro.  This may alias @lens, since all
+ *     @lens are consumed before the decode table is written to.

  *
  * @num_syms:
  *
  * @num_syms:

- *     The number of symbols in the alphabet; also, the length of the
- *     'lens' array.  Must be less than or equal to
- *     DECODE_TABLE_MAX_SYMBOLS.
+ *     The number of symbols in the alphabet.

  *
  * @table_bits:
  *
  * @table_bits:

- *     The order of the decode table size, as explained above.  Must be
- *     less than or equal to DECODE_TABLE_MAX_TABLE_BITS.
+ *     The log base 2 of the number of entries in the root table.

  *
  * @lens:
  *
  * @lens:

- *     An array of length @num_syms, indexable by symbol, that gives the
- *     length of the codeword, in bits, for that symbol.  The length can
- *     be 0, which means that the symbol does not have a codeword
- *     assigned.  This is permitted to alias @decode_table, since all
- *     information from @lens is consumed before anything is written to
- *     @decode_table.
+ *     An array of length @num_syms, indexed by symbol, that gives the length
+ *     of the codeword, in bits, for each symbol.  The length can be 0, which
+ *     means that the symbol does not have a codeword assigned.  In addition,
+ *     @lens may alias @decode_table, as noted above.

  *
  * @max_codeword_len:
  *
  * @max_codeword_len:

- *     The longest codeword length allowed in the compression format.
- *     All entries in 'lens' must be less than or equal to this value.
- *     This must be less than or equal to DECODE_TABLE_MAX_CODEWORD_LEN.
+ *     The maximum codeword length permitted for this code.  All entries in
+ *     'lens' must be less than or equal to this value.

  *
  *

- * Returns 0 on success, or -1 if the lengths do not form a valid prefix
- * code.
+ * Returns 0 on success, or -1 if the lengths do not form a valid prefix code.

  */
 int
  */
 int

-make_huffman_decode_table(u16 decode_table[const],
-                         const unsigned num_syms,
-                         const unsigned table_bits,
-                         const u8 lens[const],
-                         const unsigned max_codeword_len)
+make_huffman_decode_table(u16 decode_table[], unsigned num_syms,
+                         unsigned table_bits, const u8 lens[],
+                         unsigned max_codeword_len)

 {
 {

-       const unsigned table_num_entries = 1 << table_bits;
-       unsigned len_counts[max_codeword_len + 1];
+       u16 len_counts[max_codeword_len + 1];
+       u16 offsets[max_codeword_len + 1];

        u16 sorted_syms[num_syms];
        u16 sorted_syms[num_syms];

-       int left;
-       void *decode_table_ptr;
+       s32 remainder = 1;
+       void *entry_ptr = decode_table;
+       unsigned codeword_len = 1;

        unsigned sym_idx;
        unsigned sym_idx;

-       unsigned codeword_len;
-       unsigned stores_per_loop;
-       unsigned decode_table_pos;
-
-#ifdef USE_WORD_FILL
-       const unsigned entries_per_word = WORDBYTES / sizeof(decode_table[0]);
-#endif
-
-#ifdef USE_SSE2_FILL
-       const unsigned entries_per_xmm = sizeof(__m128i) / sizeof(decode_table[0]);
-#endif
+       unsigned codeword;
+       unsigned subtable_pos;
+       unsigned subtable_bits;
+       unsigned subtable_prefix;

 
 

-       /* Count how many symbols have each possible codeword length.
-        * Note that a length of 0 indicates the corresponding symbol is not
-        * used in the code and therefore does not have a codeword.  */
+       /* Count how many codewords have each length, including 0.  */

        for (unsigned len = 0; len <= max_codeword_len; len++)
                len_counts[len] = 0;
        for (unsigned sym = 0; sym < num_syms; sym++)
                len_counts[lens[sym]]++;
 
        for (unsigned len = 0; len <= max_codeword_len; len++)
                len_counts[len] = 0;
        for (unsigned sym = 0; sym < num_syms; sym++)
                len_counts[lens[sym]]++;
 

-       /* We can assume all lengths are <= max_codeword_len, but we
-        * cannot assume they form a valid prefix code.  A codeword of
-        * length n should require a proportion of the codespace equaling
-        * (1/2)^n.  The code is valid if and only if the codespace is
-        * exactly filled by the lengths, by this measure.  */
-       left = 1;
+       /* It is already guaranteed that all lengths are <= max_codeword_len,
+        * but it cannot be assumed they form a complete prefix code.  A
+        * codeword of length n should require a proportion of the codespace
+        * equaling (1/2)^n.  The code is complete if and only if, by this
+        * measure, the codespace is exactly filled by the lengths.  */

        for (unsigned len = 1; len <= max_codeword_len; len++) {
        for (unsigned len = 1; len <= max_codeword_len; len++) {

-               left <<= 1;
-               left -= len_counts[len];
-               if (unlikely(left < 0)) {
-                       /* The lengths overflow the codespace; that is, the code
-                        * is over-subscribed.  */
+               remainder = (remainder << 1) - len_counts[len];
+               /* Do the lengths overflow the codespace? */
+               if (unlikely(remainder < 0))

                        return -1;
                        return -1;

-               }

        }
 
        }
 

-       if (unlikely(left != 0)) {
+       if (remainder != 0) {

                /* The lengths do not fill the codespace; that is, they form an
                /* The lengths do not fill the codespace; that is, they form an

-                * incomplete set.  */
-               if (left == (1 << max_codeword_len)) {
-                       /* The code is completely empty.  This is arguably
-                        * invalid, but in fact it is valid in LZX and XPRESS,
-                        * so we must allow it.  By definition, no symbols can
-                        * be decoded with an empty code.  Consequently, we
-                        * technically don't even need to fill in the decode
-                        * table.  However, to avoid accessing uninitialized
-                        * memory if the algorithm nevertheless attempts to
-                        * decode symbols using such a code, we zero out the
-                        * decode table.  */
-                       memset(decode_table, 0,
-                              table_num_entries * sizeof(decode_table[0]));
-                       return 0;
-               }
-               return -1;
+                * incomplete code.  This is permitted only if the code is empty
+                * (contains no symbols). */
+
+               if (unlikely(remainder != 1U << max_codeword_len))
+                       return -1;
+
+               /* The code is empty.  When processing a well-formed stream, the
+                * decode table need not be initialized in this case.  However,
+                * we cannot assume the stream is well-formed, so we must
+                * initialize the decode table anyway.  Setting all entries to 0
+                * makes the decode table always produce symbol '0' without
+                * consuming any bits, which is good enough. */
+               memset(decode_table, 0, sizeof(decode_table[0]) << table_bits);
+               return 0;

        }
 
        }
 

-       /* Sort the symbols primarily by length and secondarily by symbol order.
-        */
-       {
-               unsigned offsets[max_codeword_len + 1];
+       /* Sort the symbols primarily by increasing codeword length and
+        * secondarily by increasing symbol value. */

 
 

-               /* Initialize 'offsets' so that offsets[len] for 1 <= len <=
-                * max_codeword_len is the number of codewords shorter than
-                * 'len' bits.  */
-               offsets[1] = 0;
-               for (unsigned len = 1; len < max_codeword_len; len++)
-                       offsets[len + 1] = offsets[len] + len_counts[len];
+       /* Initialize 'offsets' so that 'offsets[len]' is the number of
+        * codewords shorter than 'len' bits, including length 0. */
+       offsets[0] = 0;
+       for (unsigned len = 0; len < max_codeword_len; len++)
+               offsets[len + 1] = offsets[len] + len_counts[len];

 
 

-               /* Use the 'offsets' array to sort the symbols.
-                * Note that we do not include symbols that are not used in the
-                * code.  Consequently, fewer than 'num_syms' entries in
-                * 'sorted_syms' may be filled.  */
-               for (unsigned sym = 0; sym < num_syms; sym++)
-                       if (lens[sym] != 0)
-                               sorted_syms[offsets[lens[sym]]++] = sym;
-       }
+       /* Use the 'offsets' array to sort the symbols. */
+       for (unsigned sym = 0; sym < num_syms; sym++)
+               sorted_syms[offsets[lens[sym]]++] = sym;

 
 

-       /* Fill entries for codewords with length <= table_bits
-        * --- that is, those short enough for a direct mapping.
+       /*
+        * Fill the root table entries for codewords no longer than table_bits.

         *
         * The table will start with entries for the shortest codeword(s), which
         *
         * The table will start with entries for the shortest codeword(s), which

-        * have the most entries.  From there, the number of entries per
+        * will have the most entries.  From there, the number of entries per

         * codeword will decrease.  As an optimization, we may begin filling
         * entries with SSE2 vector accesses (8 entries/store), then change to
         * codeword will decrease.  As an optimization, we may begin filling
         * entries with SSE2 vector accesses (8 entries/store), then change to

-        * 'machine_word_t' accesses (2 or 4 entries/store), then change to
-        * 16-bit accesses (1 entry/store).  */
-       decode_table_ptr = decode_table;
-       sym_idx = 0;
-       codeword_len = 1;
-#ifdef USE_SSE2_FILL
-       /* Fill the entries one 128-bit vector at a time.
-        * This is 8 entries per store.  */
-       stores_per_loop = (1 << (table_bits - codeword_len)) / entries_per_xmm;
-       for (; stores_per_loop != 0; codeword_len++, stores_per_loop >>= 1) {
+        * word accesses (2 or 4 entries/store), then change to 16-bit accesses
+        * (1 entry/store).
+        */
+       sym_idx = offsets[0];
+
+#ifdef __SSE2__
+       /* Fill entries one 128-bit vector (8 entries) at a time. */
+       for (unsigned stores_per_loop = (1U << (table_bits - codeword_len)) /
+                                   (sizeof(__m128i) / sizeof(decode_table[0]));
+            stores_per_loop != 0; codeword_len++, stores_per_loop >>= 1)
+       {

                unsigned end_sym_idx = sym_idx + len_counts[codeword_len];
                for (; sym_idx < end_sym_idx; sym_idx++) {
                unsigned end_sym_idx = sym_idx + len_counts[codeword_len];
                for (; sym_idx < end_sym_idx; sym_idx++) {

-                       /* Note: unlike in the machine_word_t version below, the
-                        * __m128i type already has __attribute__((may_alias)),
-                        * so using it to access the decode table, which is an
-                        * array of unsigned shorts, will not violate strict
+                       /* Note: unlike in the "word" version below, the __m128i
+                        * type already has __attribute__((may_alias)), so using
+                        * it to access an array of u16 will not violate strict

                         * aliasing.  */
                         * aliasing.  */

-                       u16 entry;
-                       __m128i v;
-                       __m128i *p;
-                       unsigned n;
-
-                       entry = MAKE_DIRECT_ENTRY(sorted_syms[sym_idx], codeword_len);
-
-                       v = _mm_set1_epi16(entry);
-                       p = (__m128i*)decode_table_ptr;
-                       n = stores_per_loop;
+                       __m128i v = _mm_set1_epi16(
+                               MAKE_DECODE_TABLE_ENTRY(sorted_syms[sym_idx],
+                                                       codeword_len));
+                       unsigned n = stores_per_loop;

                        do {
                        do {

-                               *p++ = v;
+                               *(__m128i *)entry_ptr = v;
+                               entry_ptr += sizeof(v);

                        } while (--n);
                        } while (--n);

-                       decode_table_ptr = p;

                }
        }
                }
        }

-#endif /* USE_SSE2_FILL */
+#endif /* __SSE2__ */

 
 

-#ifdef USE_WORD_FILL
-       /* Fill the entries one machine word at a time.
-        * On 32-bit systems this is 2 entries per store, while on 64-bit
-        * systems this is 4 entries per store.  */
-       stores_per_loop = (1 << (table_bits - codeword_len)) / entries_per_word;
-       for (; stores_per_loop != 0; codeword_len++, stores_per_loop >>= 1) {
+#ifdef __GNUC__
+       /* Fill entries one word (2 or 4 entries) at a time. */
+       for (unsigned stores_per_loop = (1U << (table_bits - codeword_len)) /
+                                       (WORDBYTES / sizeof(decode_table[0]));
+            stores_per_loop != 0; codeword_len++, stores_per_loop >>= 1)
+       {

                unsigned end_sym_idx = sym_idx + len_counts[codeword_len];
                for (; sym_idx < end_sym_idx; sym_idx++) {
 
                unsigned end_sym_idx = sym_idx + len_counts[codeword_len];
                for (; sym_idx < end_sym_idx; sym_idx++) {
 


@@ -285,140 +228,105 @@ make_huffman_decode_table(u16 decode_table[const],
                         * the code with -fno-strict-aliasing to guarantee
                         * correctness.  To work around this problem, use the
                         * gcc 'may_alias' extension.  */
                         * the code with -fno-strict-aliasing to guarantee
                         * correctness.  To work around this problem, use the
                         * gcc 'may_alias' extension.  */

-                       typedef machine_word_t _may_alias_attribute aliased_word_t;
-
-                       machine_word_t v;
-                       aliased_word_t *p;
-                       unsigned n;
-
-                       STATIC_ASSERT(WORDBITS == 32 || WORDBITS == 64);
-
-                       v = MAKE_DIRECT_ENTRY(sorted_syms[sym_idx], codeword_len);
-                       v |= v << 16;
-                       v |= v << (WORDBITS == 64 ? 32 : 0);
-
-                       p = (aliased_word_t *)decode_table_ptr;
-                       n = stores_per_loop;
-
+                       typedef machine_word_t
+                               __attribute__((may_alias)) aliased_word_t;
+                       aliased_word_t v = repeat_u16(
+                               MAKE_DECODE_TABLE_ENTRY(sorted_syms[sym_idx],
+                                                       codeword_len));
+                       unsigned n = stores_per_loop;

                        do {
                        do {

-                               *p++ = v;
+                               *(aliased_word_t *)entry_ptr = v;
+                               entry_ptr += sizeof(v);

                        } while (--n);
                        } while (--n);

-                       decode_table_ptr = p;

                }
        }
                }
        }

-#endif /* USE_WORD_FILL */
+#endif /* __GNUC__ */

 
 

-       /* Fill the entries one 16-bit integer at a time.  */
-       stores_per_loop = (1 << (table_bits - codeword_len));
-       for (; stores_per_loop != 0; codeword_len++, stores_per_loop >>= 1) {
+       /* Fill entries one at a time. */
+       for (unsigned stores_per_loop = (1U << (table_bits - codeword_len));
+            stores_per_loop != 0; codeword_len++, stores_per_loop >>= 1)
+       {

                unsigned end_sym_idx = sym_idx + len_counts[codeword_len];
                for (; sym_idx < end_sym_idx; sym_idx++) {
                unsigned end_sym_idx = sym_idx + len_counts[codeword_len];
                for (; sym_idx < end_sym_idx; sym_idx++) {

-                       u16 entry;
-                       u16 *p;
-                       unsigned n;
-
-                       entry = MAKE_DIRECT_ENTRY(sorted_syms[sym_idx], codeword_len);
-
-                       p = (u16*)decode_table_ptr;
-                       n = stores_per_loop;
-
+                       u16 v = MAKE_DECODE_TABLE_ENTRY(sorted_syms[sym_idx],
+                                                       codeword_len);
+                       unsigned n = stores_per_loop;

                        do {
                        do {

-                               *p++ = entry;
+                               *(u16 *)entry_ptr = v;
+                               entry_ptr += sizeof(v);

                        } while (--n);
                        } while (--n);

-
-                       decode_table_ptr = p;

                }
        }
 
                }
        }
 

-       /* If we've filled in the entire table, we are done.  Otherwise,
-        * there are codewords longer than table_bits for which we must
-        * generate binary trees.  */
-
-       decode_table_pos = (u16*)decode_table_ptr - decode_table;
-       if (decode_table_pos != table_num_entries) {
-               unsigned j;
-               unsigned next_free_tree_slot;
-               unsigned cur_codeword;
-
-               /* First, zero out the remaining entries.  This is
-                * necessary so that these entries appear as
-                * "unallocated" in the next part.  Each of these entries
-                * will eventually be filled with the representation of
-                * the root node of a binary tree.  */
-               j = decode_table_pos;
-               do {
-                       decode_table[j] = 0;
-               } while (++j != table_num_entries);
-
-               /* We allocate child nodes starting at the end of the
-                * direct lookup table.  Note that there should be
-                * 2*num_syms extra entries for this purpose, although
-                * fewer than this may actually be needed.  */
-               next_free_tree_slot = table_num_entries;
-
-               /* Iterate through each codeword with length greater than
-                * 'table_bits', primarily in order of codeword length
-                * and secondarily in order of symbol.  */
-               for (cur_codeword = decode_table_pos << 1;
-                    codeword_len <= max_codeword_len;
-                    codeword_len++, cur_codeword <<= 1)
-               {
-                       unsigned end_sym_idx = sym_idx + len_counts[codeword_len];
-                       for (; sym_idx < end_sym_idx; sym_idx++, cur_codeword++)
-                       {
-                               /* 'sym' is the symbol represented by the
-                                * codeword.  */
-                               unsigned sym = sorted_syms[sym_idx];
-
-                               unsigned extra_bits = codeword_len - table_bits;
+       /* If all symbols were processed, then no subtables are required. */
+       if (sym_idx == num_syms)
+               return 0;
+
+       /* At least one subtable is required.  Process the remaining symbols. */
+       codeword = ((u16 *)entry_ptr - decode_table) << 1;
+       subtable_pos = 1U << table_bits;
+       subtable_bits = table_bits;
+       subtable_prefix = -1;
+       do {
+               while (len_counts[codeword_len] == 0) {
+                       codeword_len++;
+                       codeword <<= 1;
+               }

 
 

-                               unsigned node_idx = cur_codeword >> extra_bits;
+               unsigned prefix = codeword >> (codeword_len - table_bits);
+
+               /* Start a new subtable if the first 'table_bits' bits of the
+                * codeword don't match the prefix for the previous subtable, or
+                * if this will be the first subtable. */
+               if (prefix != subtable_prefix) {
+
+                       subtable_prefix = prefix;
+
+                       /*
+                        * Calculate the subtable length.  If the codeword
+                        * length exceeds 'table_bits' by n, then the subtable
+                        * needs at least 2^n entries.  But it may need more; if
+                        * there are fewer than 2^n codewords of length
+                        * 'table_bits + n' remaining, then n will need to be
+                        * incremented to bring in longer codewords until the
+                        * subtable can be filled completely.  Note that it
+                        * always will, eventually, be possible to fill the
+                        * subtable, since it was previously verified that the
+                        * code is complete.
+                        */
+                       subtable_bits = codeword_len - table_bits;
+                       remainder = (s32)1 << subtable_bits;
+                       for (;;) {
+                               remainder -= len_counts[table_bits +
+                                                       subtable_bits];
+                               if (remainder <= 0)
+                                       break;
+                               subtable_bits++;
+                               remainder <<= 1;
+                       }

 
 

-                               /* Go through each bit of the current codeword
-                                * beyond the prefix of length @table_bits and
-                                * walk the appropriate binary tree, allocating
-                                * any slots that have not yet been allocated.
-                                *
-                                * Note that the 'pointer' entry to the binary
-                                * tree, which is stored in the direct lookup
-                                * portion of the table, is represented
-                                * identically to other internal (non-leaf)
-                                * nodes of the binary tree; it can be thought
-                                * of as simply the root of the tree.  The
-                                * representation of these internal nodes is
-                                * simply the index of the left child combined
-                                * with the special bits 0xC000 to distinguish
-                                * the entry from direct mapping and leaf node
-                                * entries.  */
-                               do {
+                       /* Create the entry that points from the root table to
+                        * the subtable.  This entry contains the index of the
+                        * start of the subtable and the number of bits with
+                        * which the subtable is indexed (the log base 2 of the
+                        * number of entries it contains).  */
+                       decode_table[subtable_prefix] =
+                               MAKE_DECODE_TABLE_ENTRY(subtable_pos,
+                                                       subtable_bits);
+               }

 
 

-                                       /* At least one bit remains in the
-                                        * codeword, but the current node is an
-                                        * unallocated leaf.  Change it to an
-                                        * internal node.  */
-                                       if (decode_table[node_idx] == 0) {
-                                               decode_table[node_idx] =
-                                                       next_free_tree_slot | 0xC000;
-                                               decode_table[next_free_tree_slot++] = 0;
-                                               decode_table[next_free_tree_slot++] = 0;
-                                       }
+               /* Fill the subtable entries for this symbol. */
+               u16 entry = MAKE_DECODE_TABLE_ENTRY(sorted_syms[sym_idx],
+                                                   codeword_len - table_bits);
+               unsigned n = 1U << (subtable_bits - (codeword_len -
+                                                    table_bits));
+               do {
+                       decode_table[subtable_pos++] = entry;
+               } while (--n);

 
 

-                                       /* Go to the left child if the next bit
-                                        * in the codeword is 0; otherwise go to
-                                        * the right child.  */
-                                       node_idx = decode_table[node_idx] & 0x3FFF;
-                                       --extra_bits;
-                                       node_idx += (cur_codeword >> extra_bits) & 1;
-                               } while (extra_bits != 0);
+               len_counts[codeword_len]--;
+               codeword++;
+       } while (++sym_idx < num_syms);

 
 

-                               /* We've traversed the tree using the entire
-                                * codeword, and we're now at the entry where
-                                * the actual symbol will be stored.  This is
-                                * distinguished from internal nodes by not
-                                * having its high two bits set.  */
-                               decode_table[node_idx] = sym;
-                       }
-               }
-       }

        return 0;
 }
        return 0;
 }

diff --git a/src/lzms_decompress.c b/src/lzms_decompress.c
index 1ea0ac6da3d1e87141ba5252dd33fc14736e2aa1..4791054a7f468202d21e97d60fe830cc0667ee03 100644 (file)
--- a/src/lzms_decompress.c
+++ b/src/lzms_decompress.c
@@ -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
  *
  * 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


@@ -257,10 +257,10 @@
 
 /* The TABLEBITS values can be changed; they only affect decoding speed.  */
 #define LZMS_LITERAL_TABLEBITS         10
 
 /* 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 {
 
 
 struct lzms_range_decoder {
 


@@ -323,33 +323,28 @@ struct lzms_decompressor {
 
        struct lzms_probabilites probs;
 
 
        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;
 
        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;
 
        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;
 
        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;
 
        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;
 
        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);
 }
 
        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)
 {
 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 entry;

-       unsigned sym;
+       unsigned symbol;
+       unsigned length;

 
        lzms_ensure_bits(is, LZMS_MAX_CODEWORD_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);
                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);
        if (--rebuild_info->num_syms_until_rebuild == 0)
                lzms_rebuild_huffman_code(rebuild_info);

-       return sym;
+       return symbol;

 }
 
 static inline unsigned
 }
 
 static inline unsigned

diff --git a/src/lzx_decompress.c b/src/lzx_decompress.c
index 0907fd8718bf0696d8d4adb0ddfdda6517f38ce2..9f93fcf781441cc815e155dda41b6a339910c879 100644 (file)
--- a/src/lzx_decompress.c
+++ b/src/lzx_decompress.c
@@ -64,7 +64,7 @@
 
 /* These values are chosen for fast decompression.  */
 #define LZX_MAINCODE_TABLEBITS         11
 
 /* These values are chosen for fast decompression.  */
 #define LZX_MAINCODE_TABLEBITS         11

-#define LZX_LENCODE_TABLEBITS          10
+#define LZX_LENCODE_TABLEBITS          9

 #define LZX_PRECODE_TABLEBITS          6
 #define LZX_ALIGNEDCODE_TABLEBITS      7
 
 #define LZX_PRECODE_TABLEBITS          6
 #define LZX_ALIGNEDCODE_TABLEBITS      7
 


@@ -72,28 +72,23 @@
 
 struct lzx_decompressor {
 
 
 struct lzx_decompressor {
 

-       u16 maincode_decode_table[(1 << LZX_MAINCODE_TABLEBITS) +
-                                       (LZX_MAINCODE_MAX_NUM_SYMBOLS * 2)]
-                                       _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+       DECODE_TABLE(maincode_decode_table, LZX_MAINCODE_MAX_NUM_SYMBOLS,
+                    LZX_MAINCODE_TABLEBITS, LZX_MAX_MAIN_CODEWORD_LEN);

        u8 maincode_lens[LZX_MAINCODE_MAX_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
 
        u8 maincode_lens[LZX_MAINCODE_MAX_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
 

-
-       u16 lencode_decode_table[(1 << LZX_LENCODE_TABLEBITS) +
-                                       (LZX_LENCODE_NUM_SYMBOLS * 2)]
-                                       _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+       DECODE_TABLE(lencode_decode_table, LZX_LENCODE_NUM_SYMBOLS,
+                    LZX_LENCODE_TABLEBITS, LZX_MAX_LEN_CODEWORD_LEN);

        u8 lencode_lens[LZX_LENCODE_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
 
        union {
        u8 lencode_lens[LZX_LENCODE_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
 
        union {

-               u16 alignedcode_decode_table[(1 << LZX_ALIGNEDCODE_TABLEBITS) +
-                                               (LZX_ALIGNEDCODE_NUM_SYMBOLS * 2)]
-                                               _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+               DECODE_TABLE(alignedcode_decode_table, LZX_ALIGNEDCODE_NUM_SYMBOLS,
+                            LZX_ALIGNEDCODE_TABLEBITS, LZX_MAX_ALIGNED_CODEWORD_LEN);

                u8 alignedcode_lens[LZX_ALIGNEDCODE_NUM_SYMBOLS];
        };
 
        union {
                u8 alignedcode_lens[LZX_ALIGNEDCODE_NUM_SYMBOLS];
        };
 
        union {

-               u16 precode_decode_table[(1 << LZX_PRECODE_TABLEBITS) +
-                                        (LZX_PRECODE_NUM_SYMBOLS * 2)]
-                                               _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+               DECODE_TABLE(precode_decode_table, LZX_PRECODE_NUM_SYMBOLS,
+                            LZX_PRECODE_TABLEBITS, LZX_MAX_PRE_CODEWORD_LEN);

                u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS];
                u8 extra_offset_bits[LZX_MAX_OFFSET_SLOTS];
        };
                u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS];
                u8 extra_offset_bits[LZX_MAX_OFFSET_SLOTS];
        };

diff --git a/src/xpress_decompress.c b/src/xpress_decompress.c
index ec5b1831cd27f24c18bf32a6a329a96b9af4ca26..9fd5ac5eb045512b67c31831ae5499aa7ee3626e 100644 (file)
--- a/src/xpress_decompress.c
+++ b/src/xpress_decompress.c
@@ -6,7 +6,7 @@
 
 /*
  *
 
 /*
  *

- * Copyright (C) 2012, 2013, 2015 Eric Biggers
+ * Copyright (C) 2012-2016 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
  *
  * 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


@@ -73,7 +73,7 @@
 #include "wimlib/xpress_constants.h"
 
 /* This value is chosen for fast decompression.  */
 #include "wimlib/xpress_constants.h"
 
 /* This value is chosen for fast decompression.  */

-#define XPRESS_TABLEBITS 12
+#define XPRESS_TABLEBITS 11

 
 static int
 xpress_decompress(const void *restrict compressed_data, size_t compressed_size,
 
 static int
 xpress_decompress(const void *restrict compressed_data, size_t compressed_size,


@@ -85,8 +85,8 @@ xpress_decompress(const void *restrict compressed_data, size_t compressed_size,
        u8 *out_next = out_begin;
        u8 * const out_end = out_begin + uncompressed_size;
        union {
        u8 *out_next = out_begin;
        u8 * const out_end = out_begin + uncompressed_size;
        union {

-               u16 decode_table[(1 << XPRESS_TABLEBITS) + 2 * XPRESS_NUM_SYMBOLS]
-                               _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+               DECODE_TABLE(decode_table, XPRESS_NUM_SYMBOLS,
+                            XPRESS_TABLEBITS, XPRESS_MAX_CODEWORD_LEN);

                u8 lens[XPRESS_NUM_SYMBOLS];
        } u;
        struct input_bitstream is;
                u8 lens[XPRESS_NUM_SYMBOLS];
        } u;
        struct input_bitstream is;