*
* This is a Binary Trees (bt) based matchfinder.
*
- * The data structure is a hash table where each hash bucket contains a binary
- * tree of sequences whose first 3 bytes share the same hash code. Each
+ * The main data structure is a hash table where each hash bucket contains a
+ * binary tree of sequences whose first 3 bytes share the same hash code. Each
* sequence is identified by its starting position in the input buffer. Each
* binary tree is always sorted such that each left child represents a sequence
* lexicographically lesser than its parent and each right child represents a
#include "wimlib/lz_extend.h"
#include "wimlib/lz_hash.h"
-#define BT_MATCHFINDER_HASH_ORDER 16
+#define BT_MATCHFINDER_HASH3_ORDER 16
/* TEMPLATED functions and structures have MF_SUFFIX appended to their name. */
#undef TEMPLATED
u32 offset;
};
-static inline u32
-bt_matchfinder_hash_3_bytes(const u8 *in_next)
-{
- return lz_hash_3_bytes(in_next, BT_MATCHFINDER_HASH_ORDER);
-}
-
#endif /* _WIMLIB_BT_MATCHFINDER_H */
struct TEMPLATED(bt_matchfinder) {
- pos_t hash_tab[1UL << BT_MATCHFINDER_HASH_ORDER];
+
+ /* The hash table for finding length 2 matches, if enabled */
+#ifdef BT_MATCHFINDER_HASH2_ORDER
+ pos_t hash2_tab[1UL << BT_MATCHFINDER_HASH2_ORDER];
+#endif
+
+ /* The hash table which contains the roots of the binary trees for
+ * finding length 3 matches */
+ pos_t hash3_tab[1UL << BT_MATCHFINDER_HASH3_ORDER];
+
+ /* The child node references for the binary trees. The left and right
+ * children of the node for the sequence with position 'pos' are
+ * 'child_tab[pos * 2]' and 'child_tab[pos * 2 + 1]', respectively. */
pos_t child_tab[];
};
}
static inline pos_t *
-TEMPLATED(bt_child)(struct TEMPLATED(bt_matchfinder) *mf, pos_t node, int offset)
+TEMPLATED(bt_left_child)(struct TEMPLATED(bt_matchfinder) *mf, u32 node)
{
- return &mf->child_tab[(node << 1) + offset];
+ return &mf->child_tab[(node << 1) + 0];
}
static inline pos_t *
-TEMPLATED(bt_left_child)(struct TEMPLATED(bt_matchfinder) *mf, pos_t node)
+TEMPLATED(bt_right_child)(struct TEMPLATED(bt_matchfinder) *mf, u32 node)
{
- return TEMPLATED(bt_child)(mf, node, 0);
+ return &mf->child_tab[(node << 1) + 1];
}
-static inline pos_t *
-TEMPLATED(bt_right_child)(struct TEMPLATED(bt_matchfinder) *mf, pos_t node)
-{
- return TEMPLATED(bt_child)(mf, node, 1);
-}
-
-/*
- * Retrieve a list of matches with the current position.
- *
- * @mf
- * The matchfinder structure.
- * @in_begin
- * Pointer to the beginning of the input buffer.
- * @in_next
- * Pointer to the next byte in the input buffer to process. This is the
- * pointer to the sequence being matched against.
- * @min_len
- * Only record matches that are at least this long.
- * @max_len
- * The maximum permissible match length at this position.
- * @nice_len
- * Stop searching if a match of at least this length is found.
- * Must be <= @max_len.
- * @max_search_depth
- * Limit on the number of potential matches to consider. Must be >= 1.
- * @next_hash
- * Pointer to the hash code for the current sequence, which was computed
- * one position in advance so that the binary tree root could be
- * prefetched. This is an input/output parameter.
- * @best_len_ret
- * The length of the longest match found is written here. (This is
- * actually redundant with the 'struct lz_match' array, but this is easier
- * for the compiler to optimize when inlined and the caller immediately
- * does a check against 'best_len'.)
- * @lz_matchptr
- * An array in which this function will record the matches. The recorded
- * matches will be sorted by strictly increasing length and strictly
- * increasing offset. The maximum number of matches that may be found is
- * 'min(nice_len, max_len) - 3 + 1'.
- *
- * The return value is a pointer to the next available slot in the @lz_matchptr
- * array. (If no matches were found, this will be the same as @lz_matchptr.)
- */
+/* Advance the binary tree matchfinder by one byte, optionally recording
+ * matches. @record_matches should be a compile-time constant. */
static inline struct lz_match *
-TEMPLATED(bt_matchfinder_get_matches)(struct TEMPLATED(bt_matchfinder) * const restrict mf,
- const u8 * const in_begin,
- const u8 * const in_next,
- const unsigned min_len,
- const unsigned max_len,
- const unsigned nice_len,
- const unsigned max_search_depth,
- u32 * restrict next_hash,
- unsigned * restrict best_len_ret,
- struct lz_match * restrict lz_matchptr)
+TEMPLATED(bt_matchfinder_advance_one_byte)(struct TEMPLATED(bt_matchfinder) * const restrict mf,
+ const u8 * const restrict in_begin,
+ const ptrdiff_t cur_pos,
+ const u32 max_len,
+ const u32 nice_len,
+ const u32 max_search_depth,
+ u32 * const restrict next_hash,
+ u32 * const restrict best_len_ret,
+ struct lz_match * restrict lz_matchptr,
+ const bool record_matches)
{
- unsigned depth_remaining = max_search_depth;
- u32 hash;
- pos_t cur_node;
+ const u8 *in_next = in_begin + cur_pos;
+ u32 depth_remaining = max_search_depth;
+#ifdef BT_MATCHFINDER_HASH2_ORDER
+ u16 seq2;
+ u32 hash2;
+#endif
+ u32 hash3;
+ u32 cur_node;
const u8 *matchptr;
pos_t *pending_lt_ptr, *pending_gt_ptr;
- unsigned best_lt_len, best_gt_len;
- unsigned len;
- unsigned best_len = min_len - 1;
+ u32 best_lt_len, best_gt_len;
+ u32 len;
+ u32 best_len = 2;
if (unlikely(max_len < LZ_HASH3_REQUIRED_NBYTES + 1)) {
*best_len_ret = best_len;
return lz_matchptr;
}
- hash = *next_hash;
- *next_hash = bt_matchfinder_hash_3_bytes(in_next + 1);
- cur_node = mf->hash_tab[hash];
- mf->hash_tab[hash] = in_next - in_begin;
- prefetchw(&mf->hash_tab[*next_hash]);
+ hash3 = *next_hash;
+ *next_hash = lz_hash(load_u24_unaligned(in_next + 1), BT_MATCHFINDER_HASH3_ORDER);
+ prefetchw(&mf->hash3_tab[*next_hash]);
+
+#ifdef BT_MATCHFINDER_HASH2_ORDER
+ seq2 = load_u16_unaligned(in_next);
+ hash2 = lz_hash(seq2, BT_MATCHFINDER_HASH2_ORDER);
+ cur_node = mf->hash2_tab[hash2];
+ mf->hash2_tab[hash2] = cur_pos;
+ if (record_matches &&
+ seq2 == load_u16_unaligned(&in_begin[cur_node]) &&
+ likely(in_next != in_begin))
+ {
+ lz_matchptr->length = 2;
+ lz_matchptr->offset = in_next - &in_begin[cur_node];
+ lz_matchptr++;
+ }
+#endif
- pending_lt_ptr = TEMPLATED(bt_left_child)(mf, in_next - in_begin);
- pending_gt_ptr = TEMPLATED(bt_right_child)(mf, in_next - in_begin);
- best_lt_len = 0;
- best_gt_len = 0;
- len = 0;
+ cur_node = mf->hash3_tab[hash3];
+ mf->hash3_tab[hash3] = cur_pos;
+
+ pending_lt_ptr = TEMPLATED(bt_left_child)(mf, cur_pos);
+ pending_gt_ptr = TEMPLATED(bt_right_child)(mf, cur_pos);
if (!cur_node) {
*pending_lt_ptr = 0;
return lz_matchptr;
}
+ best_lt_len = 0;
+ best_gt_len = 0;
+ len = 0;
+
for (;;) {
matchptr = &in_begin[cur_node];
if (matchptr[len] == in_next[len]) {
- len = lz_extend(in_next, matchptr, len + 1, max_len);
- if (len > best_len) {
- best_len = len;
- lz_matchptr->length = len;
- lz_matchptr->offset = in_next - matchptr;
- lz_matchptr++;
+ len = lz_extend(in_next, matchptr, len + 1,
+ (record_matches ? max_len : nice_len));
+ if (!record_matches || len > best_len) {
+ if (record_matches) {
+ best_len = len;
+ lz_matchptr->length = len;
+ lz_matchptr->offset = in_next - matchptr;
+ lz_matchptr++;
+ }
if (len >= nice_len) {
*pending_lt_ptr = *TEMPLATED(bt_left_child)(mf, cur_node);
*pending_gt_ptr = *TEMPLATED(bt_right_child)(mf, cur_node);
}
}
+/*
+ * Retrieve a list of matches with the current position.
+ *
+ * @mf
+ * The matchfinder structure.
+ * @in_begin
+ * Pointer to the beginning of the input buffer.
+ * @cur_pos
+ * The current position in the input buffer (the position of the sequence
+ * being matched against).
+ * @max_len
+ * The maximum permissible match length at this position.
+ * @nice_len
+ * Stop searching if a match of at least this length is found.
+ * Must be <= @max_len.
+ * @max_search_depth
+ * Limit on the number of potential matches to consider. Must be >= 1.
+ * @next_hash
+ * Pointer to the hash code for the current sequence, which was computed
+ * one position in advance so that the binary tree root could be
+ * prefetched. This is an input/output parameter.
+ * @best_len_ret
+ * If a match of length >= 3 was found, then the length of the longest such
+ * match is written here; otherwise 2 is written here. (Note: this is
+ * redundant with the 'struct lz_match' array, but this is easier for the
+ * compiler to optimize when inlined and the caller immediately does a
+ * check against 'best_len'.)
+ * @lz_matchptr
+ * An array in which this function will record the matches. The recorded
+ * matches will be sorted by strictly increasing length and increasing
+ * offset. The maximum number of matches that may be found is
+ * 'min(nice_len, max_len) - 2 + 1', or one less if length 2 matches are
+ * disabled.
+ *
+ * The return value is a pointer to the next available slot in the @lz_matchptr
+ * array. (If no matches were found, this will be the same as @lz_matchptr.)
+ */
+static inline struct lz_match *
+TEMPLATED(bt_matchfinder_get_matches)(struct TEMPLATED(bt_matchfinder) *mf,
+ const u8 *in_begin,
+ ptrdiff_t cur_pos,
+ u32 max_len,
+ u32 nice_len,
+ u32 max_search_depth,
+ u32 *next_hash,
+ u32 *best_len_ret,
+ struct lz_match *lz_matchptr)
+{
+ return TEMPLATED(bt_matchfinder_advance_one_byte)(mf,
+ in_begin,
+ cur_pos,
+ max_len,
+ nice_len,
+ max_search_depth,
+ next_hash,
+ best_len_ret,
+ lz_matchptr,
+ true);
+}
+
/*
* Advance the matchfinder, but don't record any matches.
*
* The matchfinder structure.
* @in_begin
* Pointer to the beginning of the input buffer.
- * @in_next
- * Pointer to the next byte in the input buffer to process.
- * @in_end
- * Pointer to the end of the input buffer.
+ * @cur_pos
+ * The current position in the input buffer.
+ * @max_len
+ * The maximum permissible match length at this position.
* @nice_len
* Stop searching if a match of at least this length is found.
* @max_search_depth
* actually record any matches.
*/
static inline void
-TEMPLATED(bt_matchfinder_skip_position)(struct TEMPLATED(bt_matchfinder) * const restrict mf,
- const u8 * const in_begin,
- const u8 * const in_next,
- const u8 * const in_end,
- const unsigned nice_len,
- const unsigned max_search_depth,
- u32 * restrict next_hash)
+TEMPLATED(bt_matchfinder_skip_position)(struct TEMPLATED(bt_matchfinder) *mf,
+ const u8 *in_begin,
+ ptrdiff_t cur_pos,
+ u32 max_len,
+ u32 nice_len,
+ u32 max_search_depth,
+ u32 *next_hash)
{
- unsigned depth_remaining = max_search_depth;
- u32 hash;
- pos_t cur_node;
- const u8 *matchptr;
- pos_t *pending_lt_ptr, *pending_gt_ptr;
- unsigned best_lt_len, best_gt_len;
- unsigned len;
-
- if (unlikely(in_end - in_next < LZ_HASH3_REQUIRED_NBYTES + 1))
- return;
-
- hash = *next_hash;
- *next_hash = bt_matchfinder_hash_3_bytes(in_next + 1);
- cur_node = mf->hash_tab[hash];
- mf->hash_tab[hash] = in_next - in_begin;
- prefetchw(&mf->hash_tab[*next_hash]);
-
- depth_remaining = max_search_depth;
- pending_lt_ptr = TEMPLATED(bt_left_child)(mf, in_next - in_begin);
- pending_gt_ptr = TEMPLATED(bt_right_child)(mf, in_next - in_begin);
- best_lt_len = 0;
- best_gt_len = 0;
- len = 0;
-
- if (!cur_node) {
- *pending_lt_ptr = 0;
- *pending_gt_ptr = 0;
- return;
- }
-
- for (;;) {
- matchptr = &in_begin[cur_node];
-
- if (matchptr[len] == in_next[len]) {
- len = lz_extend(in_next, matchptr, len + 1, nice_len);
- if (len == nice_len) {
- *pending_lt_ptr = *TEMPLATED(bt_left_child)(mf, cur_node);
- *pending_gt_ptr = *TEMPLATED(bt_right_child)(mf, cur_node);
- return;
- }
- }
-
- if (matchptr[len] < in_next[len]) {
- *pending_lt_ptr = cur_node;
- pending_lt_ptr = TEMPLATED(bt_right_child)(mf, cur_node);
- cur_node = *pending_lt_ptr;
- best_lt_len = len;
- if (best_gt_len < len)
- len = best_gt_len;
- } else {
- *pending_gt_ptr = cur_node;
- pending_gt_ptr = TEMPLATED(bt_left_child)(mf, cur_node);
- cur_node = *pending_gt_ptr;
- best_gt_len = len;
- if (best_lt_len < len)
- len = best_lt_len;
- }
-
- if (!cur_node || !--depth_remaining) {
- *pending_lt_ptr = 0;
- *pending_gt_ptr = 0;
- return;
- }
- }
+ u32 best_len;
+ TEMPLATED(bt_matchfinder_advance_one_byte)(mf,
+ in_begin,
+ cur_pos,
+ max_len,
+ nice_len,
+ max_search_depth,
+ next_hash,
+ &best_len,
+ NULL,
+ false);
}
#define LZX_MAX_FAST_LEVEL 34
/*
- * LZX_HASH2_ORDER is the log base 2 of the number of entries in the hash table
- * for finding length 2 matches. This can be as high as 16 (in which case the
- * hash function is trivial), but using a smaller hash table speeds up
- * compression due to reduced cache pressure.
+ * BT_MATCHFINDER_HASH2_ORDER is the log base 2 of the number of entries in the
+ * hash table for finding length 2 matches. This could be as high as 16, but
+ * using a smaller hash table speeds up compression due to reduced cache
+ * pressure.
*/
-#define LZX_HASH2_ORDER 12
-#define LZX_HASH2_LENGTH (1UL << LZX_HASH2_ORDER)
+#define BT_MATCHFINDER_HASH2_ORDER 12
/*
* These are the compressor-side limits on the codeword lengths for each Huffman
LZX_MAX_MATCHES_PER_POS +
LZX_MAX_MATCH_LEN - 1];
- /* Hash table for finding length 2 matches */
- u32 hash2_tab[LZX_HASH2_LENGTH];
-
/* Binary trees matchfinder (MUST BE LAST!!!) */
union {
struct bt_matchfinder_16 bt_mf_16;
const u8 * const in_end = in_begin + c->in_nbytes;
unsigned max_len = LZX_MAX_MATCH_LEN;
unsigned nice_len = min(c->nice_match_length, max_len);
- u32 next_hash;
+ u32 next_hash = 0;
struct lzx_lru_queue queue;
CALL_BT_MF(is_16_bit, c, bt_matchfinder_init);
- memset(c->hash2_tab, 0, sizeof(c->hash2_tab));
- next_hash = bt_matchfinder_hash_3_bytes(in_next);
lzx_lru_queue_init(&queue);
do {
struct lz_match *cache_ptr = c->match_cache;
do {
struct lz_match *lz_matchptr;
- u32 hash2;
- pos_t cur_match;
unsigned best_len;
/* If approaching the end of the input buffer, adjust
}
}
- lz_matchptr = cache_ptr + 1;
-
- /* Check for a length 2 match. */
- hash2 = lz_hash_2_bytes(in_next, LZX_HASH2_ORDER);
- cur_match = c->hash2_tab[hash2];
- c->hash2_tab[hash2] = in_next - in_begin;
- if (cur_match != 0 &&
- (LZX_HASH2_ORDER == 16 ||
- load_u16_unaligned(&in_begin[cur_match]) ==
- load_u16_unaligned(in_next)))
- {
- lz_matchptr->length = 2;
- lz_matchptr->offset = in_next - &in_begin[cur_match];
- lz_matchptr++;
- }
-
- /* Check for matches of length >= 3. */
+ /* Check for matches. */
lz_matchptr = CALL_BT_MF(is_16_bit, c, bt_matchfinder_get_matches,
in_begin,
- in_next,
- 3,
+ in_next - in_begin,
max_len,
nice_len,
c->max_search_depth,
&next_hash,
&best_len,
- lz_matchptr);
+ cache_ptr + 1);
in_next++;
cache_ptr->length = lz_matchptr - (cache_ptr + 1);
cache_ptr = lz_matchptr;
continue;
}
}
- c->hash2_tab[lz_hash_2_bytes(in_next, LZX_HASH2_ORDER)] =
- in_next - in_begin;
CALL_BT_MF(is_16_bit, c, bt_matchfinder_skip_position,
in_begin,
- in_next,
- in_end,
+ in_next - in_begin,
+ max_len,
nice_len,
c->max_search_depth,
&next_hash);
git://wimlib.net / wimlib / commitdiff