#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
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
-/* 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
- * lzms_decompress.c. */
+ * lzms_decompress.c; keep them in sync!
+ */
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 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,
- unsigned num_bits, const u8 lens[],
+ unsigned table_bits, const u8 lens[],
unsigned max_codeword_len);
+/******************************************************************************/
+/* LZ match copying */
+/*----------------------------------------------------------------------------*/
+
static inline void
copy_word_unaligned(const void *src, void *dst)
{
}
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);
-
- v = b;
- v |= v << 8;
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.
*
git://wimlib.net / wimlib / blobdiff