/*
- * lcpit_matchfinder.h
+ * lcpit_matchfinder.c
*
* A match-finder for Lempel-Ziv compression based on bottom-up construction and
* traversal of the Longest Common Prefix (LCP) interval tree.
*
- * Author: Eric Biggers
- * Year: 2014, 2015
+ * The following copying information applies to this specific source code file:
*
- * The author dedicates this file to the public domain.
- * You can do whatever you want with this file.
+ * Written in 2014-2015 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
+ * worldwide via the Creative Commons Zero 1.0 Universal Public Domain
+ * Dedication (the "CC0").
+ *
+ * This software is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the CC0 for more details.
+ *
+ * You should have received a copy of the CC0 along with this software; if not
+ * see <http://creativecommons.org/publicdomain/zero/1.0/>.
*/
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
#include <limits.h>
-#include <string.h>
#include "wimlib/divsufsort.h"
#include "wimlib/lcpit_matchfinder.h"
#include "wimlib/util.h"
#define LCP_BITS 6
-#define LCP_MASK ((1 << LCP_BITS) - 1)
-#define LCP_MAX LCP_MASK
-#define NORMAL_UNVISITED_TAG ((u32)1 << 31)
-#define MAX_NORMAL_BUFSIZE ((u32)1 << (31 - LCP_BITS))
-#define HUGE_UNVISITED_TAG ((u64)1 << 63)
-#define SA_and_LCP_LCP_SHIFT (32 - LCP_BITS)
-#define SA_and_LCP_POS_MASK (((u32)1 << SA_and_LCP_LCP_SHIFT) - 1)
+#define LCP_MAX (((u32)1 << LCP_BITS) - 1)
+#define LCP_SHIFT (32 - LCP_BITS)
+#define LCP_MASK (LCP_MAX << LCP_SHIFT)
+#define POS_MASK (((u32)1 << (32 - LCP_BITS)) - 1)
+#define MAX_NORMAL_BUFSIZE (POS_MASK + 1)
+
+#define HUGE_LCP_BITS 7
+#define HUGE_LCP_MAX (((u32)1 << HUGE_LCP_BITS) - 1)
+#define HUGE_LCP_SHIFT (64 - HUGE_LCP_BITS)
+#define HUGE_LCP_MASK ((u64)HUGE_LCP_MAX << HUGE_LCP_SHIFT)
+#define HUGE_POS_MASK 0xFFFFFFFF
+#define MAX_HUGE_BUFSIZE ((u64)HUGE_POS_MASK + 1)
+#define HUGE_UNVISITED_TAG 0x100000000
+
+#define PREFETCH_SAFETY 5
/*
- * Include the template header to define the functions build_LCP(),
- * build_LCPIT(), and lcpit_advance_one_byte(). There are "normal" and "huge"
- * versions of each function. The normal versions assume that a buffer position
- * and LCP value can be packed into a 32-bit integer, whereas the huge versions
- * assume that 64 bits is needed.
- *
- * Both versions cap LCP values to 6 bits. This limits the depth of the
- * lcp-interval tree without hurting the compression ratio too much. Matches of
- * length 63 are sufficiently long that the compression ratio doesn't change
- * significantly if we choose one such match over another.
+ * Build the LCP (Longest Common Prefix) array in linear time.
+ *
+ * LCP[r] will be the length of the longest common prefix between the suffixes
+ * with positions SA[r - 1] and SA[r]. LCP[0] will be undefined.
+ *
+ * Algorithm taken from Kasai et al. (2001), but modified slightly:
+ *
+ * - With bytes there is no realistic way to reserve a unique symbol for
+ * end-of-buffer, so use explicit checks for end-of-buffer.
+ *
+ * - For decreased memory usage and improved memory locality, pack the two
+ * logically distinct SA and LCP arrays into a single array SA_and_LCP.
+ *
+ * - Since SA_and_LCP is accessed randomly, improve the cache behavior by
+ * reading several entries ahead in ISA and prefetching the upcoming
+ * SA_and_LCP entry.
+ *
+ * - If an LCP value is less than the minimum match length, then store 0. This
+ * avoids having to do comparisons against the minimum match length later.
+ *
+ * - If an LCP value is greater than the "nice match length", then store the
+ * "nice match length". This caps the number of bits needed to store each
+ * LCP value, and this caps the depth of the LCP-interval tree, without
+ * usually hurting the compression ratio too much.
+ *
+ * References:
+ *
+ * Kasai et al. 2001. Linear-Time Longest-Common-Prefix Computation in
+ * Suffix Arrays and Its Applications. CPM '01 Proceedings of the 12th
+ * Annual Symposium on Combinatorial Pattern Matching pp. 181-192.
*/
-#define HUGE_MODE 1
-#include "lcpit_matchfinder_templates.h"
-#undef HUGE_MODE
+static void
+build_LCP(u32 SA_and_LCP[restrict], const u32 ISA[restrict],
+ const u8 T[restrict], const u32 n,
+ const u32 min_lcp, const u32 max_lcp)
+{
+ u32 h = 0;
+ for (u32 i = 0; i < n; i++) {
+ const u32 r = ISA[i];
+ prefetchw(&SA_and_LCP[ISA[i + PREFETCH_SAFETY]]);
+ if (r > 0) {
+ const u32 j = SA_and_LCP[r - 1] & POS_MASK;
+ const u32 lim = min(n - i, n - j);
+ while (h < lim && T[i + h] == T[j + h])
+ h++;
+ u32 stored_lcp = h;
+ if (stored_lcp < min_lcp)
+ stored_lcp = 0;
+ else if (stored_lcp > max_lcp)
+ stored_lcp = max_lcp;
+ SA_and_LCP[r] |= stored_lcp << LCP_SHIFT;
+ if (h > 0)
+ h--;
+ }
+ }
+}
-#define HUGE_MODE 0
-#include "lcpit_matchfinder_templates.h"
-#undef HUGE_MODE
+/*
+ * Use the suffix array accompanied with the longest-common-prefix array ---
+ * which in combination can be called the "enhanced suffix array" --- to
+ * simulate a bottom-up traversal of the corresponding suffix tree, or
+ * equivalently the lcp-interval tree. Do so in suffix rank order, but save the
+ * superinterval references needed for later bottom-up traversal of the tree in
+ * suffix position order.
+ *
+ * To enumerate the lcp-intervals, this algorithm scans the suffix array and its
+ * corresponding LCP array linearly. While doing so, it maintains a stack of
+ * lcp-intervals that are currently open, meaning that their left boundaries
+ * have been seen but their right boundaries have not. The bottom of the stack
+ * is the interval which covers the entire suffix array (this has lcp=0), and
+ * the top of the stack is the deepest interval that is currently open (this has
+ * the greatest lcp of any interval on the stack). When this algorithm opens an
+ * lcp-interval, it assigns it a unique index in intervals[] and pushes it onto
+ * the stack. When this algorithm closes an interval, it pops it from the stack
+ * and sets the intervals[] entry of that interval to the index and lcp of that
+ * interval's superinterval, which is the new top of the stack.
+ *
+ * This algorithm also set pos_data[pos] for each suffix position 'pos' to the
+ * index and lcp of the deepest lcp-interval containing it. Alternatively, we
+ * can interpret each suffix as being associated with a singleton lcp-interval,
+ * or leaf of the suffix tree. With this interpretation, an entry in pos_data[]
+ * is the superinterval reference for one of these singleton lcp-intervals and
+ * therefore is not fundamentally different from an entry in intervals[].
+ *
+ * To reduce memory usage, this algorithm re-uses the suffix array's memory to
+ * store the generated intervals[] array. This is possible because SA and LCP
+ * are accessed linearly, and no more than one interval is generated per suffix.
+ *
+ * The techniques used in this algorithm are described in various published
+ * papers. The generation of lcp-intervals from the suffix array (SA) and the
+ * longest-common-prefix array (LCP) is given as Algorithm BottomUpTraverse in
+ * Kasai et al. (2001) and Algorithm 4.1 ("Computation of lcp-intervals") in
+ * Abouelhoda et al. (2004). Both these papers note the equivalence between
+ * lcp-intervals (including the singleton lcp-interval for each suffix) and
+ * nodes of the suffix tree. Abouelhoda et al. (2004) furthermore applies
+ * bottom-up traversal of the lcp-interval tree to Lempel-Ziv factorization, as
+ * does Chen at al. (2008). Algorithm CPS1b of Chen et al. (2008) dynamically
+ * re-uses the suffix array during bottom-up traversal of the lcp-interval tree.
+ *
+ * References:
+ *
+ * Kasai et al. Linear-Time Longest-Common-Prefix Computation in Suffix
+ * Arrays and Its Applications. 2001. CPM '01 Proceedings of the 12th
+ * Annual Symposium on Combinatorial Pattern Matching pp. 181-192.
+ *
+ * M.I. Abouelhoda, S. Kurtz, E. Ohlebusch. 2004. Replacing Suffix Trees
+ * With Enhanced Suffix Arrays. Journal of Discrete Algorithms Volume 2
+ * Issue 1, March 2004, pp. 53-86.
+ *
+ * G. Chen, S.J. Puglisi, W.F. Smyth. 2008. Lempel-Ziv Factorization
+ * Using Less Time & Space. Mathematics in Computer Science June 2008,
+ * Volume 1, Issue 4, pp. 605-623.
+ */
+static void
+build_LCPIT(u32 intervals[restrict], u32 pos_data[restrict], const u32 n)
+{
+ u32 * const SA_and_LCP = intervals;
+ u32 next_interval_idx;
+ u32 open_intervals[LCP_MAX + 1];
+ u32 *top = open_intervals;
+ u32 prev_pos = SA_and_LCP[0] & POS_MASK;
+
+ *top = 0;
+ intervals[0] = 0;
+ next_interval_idx = 1;
+
+ for (u32 r = 1; r < n; r++) {
+ const u32 next_pos = SA_and_LCP[r] & POS_MASK;
+ const u32 next_lcp = SA_and_LCP[r] & LCP_MASK;
+ const u32 top_lcp = *top & LCP_MASK;
+
+ prefetchw(&pos_data[SA_and_LCP[r + PREFETCH_SAFETY] & POS_MASK]);
+
+ if (next_lcp == top_lcp) {
+ /* Continuing the deepest open interval */
+ pos_data[prev_pos] = *top;
+ } else if (next_lcp > top_lcp) {
+ /* Opening a new interval */
+ *++top = next_lcp | next_interval_idx++;
+ pos_data[prev_pos] = *top;
+ } else {
+ /* Closing the deepest open interval */
+ pos_data[prev_pos] = *top;
+ for (;;) {
+ const u32 closed_interval_idx = *top-- & POS_MASK;
+ const u32 superinterval_lcp = *top & LCP_MASK;
+
+ if (next_lcp == superinterval_lcp) {
+ /* Continuing the superinterval */
+ intervals[closed_interval_idx] = *top;
+ break;
+ } else if (next_lcp > superinterval_lcp) {
+ /* Creating a new interval that is a
+ * superinterval of the one being
+ * closed, but still a subinterval of
+ * its superinterval */
+ *++top = next_lcp | next_interval_idx++;
+ intervals[closed_interval_idx] = *top;
+ break;
+ } else {
+ /* Also closing the superinterval */
+ intervals[closed_interval_idx] = *top;
+ }
+ }
+ }
+ prev_pos = next_pos;
+ }
+
+ /* Close any still-open intervals. */
+ pos_data[prev_pos] = *top;
+ for (; top > open_intervals; top--)
+ intervals[*top & POS_MASK] = *(top - 1);
+}
+
+/*
+ * Advance the LCP-interval tree matchfinder by one byte.
+ *
+ * If @record_matches is true, then matches are written to the @matches array
+ * sorted by strictly decreasing length and strictly decreasing offset, and the
+ * return value is the number of matches found. Otherwise, @matches is ignored
+ * and the return value is always 0.
+ *
+ * How this algorithm works:
+ *
+ * 'cur_pos' is the position of the current suffix, which is the suffix being
+ * matched against. 'cur_pos' starts at 0 and is incremented each time this
+ * function is called. This function finds each suffix with position less than
+ * 'cur_pos' that shares a prefix with the current suffix, but for each distinct
+ * prefix length it finds only the suffix with the greatest position (i.e. the
+ * most recently seen in the linear traversal by position). This function
+ * accomplishes this using the lcp-interval tree data structure that was built
+ * by build_LCPIT() and is updated dynamically by this function.
+ *
+ * The first step is to read 'pos_data[cur_pos]', which gives the index and lcp
+ * value of the deepest lcp-interval containing the current suffix --- or,
+ * equivalently, the parent of the conceptual singleton lcp-interval that
+ * contains the current suffix.
+ *
+ * The second step is to ascend the lcp-interval tree until reaching an interval
+ * that has not yet been visited, and link the intervals to the current suffix
+ * along the way. An lcp-interval has been visited if and only if it has been
+ * linked to a suffix. Initially, no lcp-intervals are linked to suffixes.
+ *
+ * The third step is to continue ascending the lcp-interval tree, but indirectly
+ * through suffix links rather than through the original superinterval
+ * references, and continuing to form links with the current suffix along the
+ * way. Each suffix visited during this step, except in a special case to
+ * handle outdated suffixes, is a match which can be written to matches[]. Each
+ * intervals[] entry contains the position of the next suffix to visit, which we
+ * shall call 'match_pos'; this is the most recently seen suffix that belongs to
+ * that lcp-interval. 'pos_data[match_pos]' then contains the lcp and interval
+ * index of the next lcp-interval that should be visited.
+ *
+ * We can view these arrays as describing a new set of links that gets overlaid
+ * on top of the original superinterval references of the lcp-interval tree.
+ * Each such link can connect a node of the lcp-interval tree to an ancestor
+ * more than one generation removed.
+ *
+ * For each one-byte advance, the current position becomes the most recently
+ * seen suffix for a continuous sequence of lcp-intervals from a leaf interval
+ * to the root interval. Conceptually, this algorithm needs to update all these
+ * nodes to link to 'cur_pos', and then update 'pos_data[cur_pos]' to a "null"
+ * link. But actually, if some of these nodes have the same most recently seen
+ * suffix, then this algorithm just visits the pos_data[] entry for that suffix
+ * and skips over all these nodes in one step. Updating the extra nodes is
+ * accomplished by creating a redirection from the previous suffix to the
+ * current suffix.
+ *
+ * Using this shortcutting scheme, it's possible for a suffix to become out of
+ * date, which means that it is no longer the most recently seen suffix for the
+ * lcp-interval under consideration. This case is detected by noticing when the
+ * next lcp-interval link actually points deeper in the tree, and it is worked
+ * around by just continuing until we get to a link that actually takes us
+ * higher in the tree. This can be described as a lazy-update scheme.
+ */
+static forceinline u32
+lcpit_advance_one_byte(const u32 cur_pos,
+ u32 pos_data[restrict],
+ u32 intervals[restrict],
+ u32 next[restrict],
+ struct lz_match matches[restrict],
+ const bool record_matches)
+{
+ u32 ref;
+ u32 super_ref;
+ u32 match_pos;
+ struct lz_match *matchptr;
+
+ /* Get the deepest lcp-interval containing the current suffix. */
+ ref = pos_data[cur_pos];
+
+ /* Prefetch upcoming data, up to 3 positions ahead. Assume the
+ * intervals are already visited. */
+
+ /* Prefetch the superinterval via a suffix link for the deepest
+ * lcp-interval containing the suffix starting 1 position from now. */
+ prefetchw(&intervals[pos_data[next[0]] & POS_MASK]);
+
+ /* Prefetch suffix link for the deepest lcp-interval containing the
+ * suffix starting 2 positions from now. */
+ next[0] = intervals[next[1]] & POS_MASK;
+ prefetchw(&pos_data[next[0]]);
+
+ /* Prefetch the deepest lcp-interval containing the suffix starting 3
+ * positions from now. */
+ next[1] = pos_data[cur_pos + 3] & POS_MASK;
+ prefetchw(&intervals[next[1]]);
+
+ /* There is no "next suffix" after the current one. */
+ pos_data[cur_pos] = 0;
+
+ /* Ascend until we reach a visited interval, the root, or a child of the
+ * root. Link unvisited intervals to the current suffix as we go. */
+ while ((super_ref = intervals[ref & POS_MASK]) & LCP_MASK) {
+ intervals[ref & POS_MASK] = cur_pos;
+ ref = super_ref;
+ }
+
+ if (super_ref == 0) {
+ /* In this case, the current interval may be any of:
+ * (1) the root;
+ * (2) an unvisited child of the root;
+ * (3) an interval last visited by suffix 0
+ *
+ * We could avoid the ambiguity with (3) by using an lcp
+ * placeholder value other than 0 to represent "visited", but
+ * it's fastest to use 0. So we just don't allow matches with
+ * position 0. */
+
+ if (ref != 0) /* Not the root? */
+ intervals[ref & POS_MASK] = cur_pos;
+ return 0;
+ }
+
+ /* Ascend indirectly via pos_data[] links. */
+ match_pos = super_ref;
+ matchptr = matches;
+ for (;;) {
+ while ((super_ref = pos_data[match_pos]) > ref)
+ match_pos = intervals[super_ref & POS_MASK];
+ intervals[ref & POS_MASK] = cur_pos;
+ pos_data[match_pos] = ref;
+ if (record_matches) {
+ matchptr->length = ref >> LCP_SHIFT;
+ matchptr->offset = cur_pos - match_pos;
+ matchptr++;
+ }
+ if (super_ref == 0)
+ break;
+ ref = super_ref;
+ match_pos = intervals[ref & POS_MASK];
+ }
+ return matchptr - matches;
+}
+
+/* Expand SA from 32 bits to 64 bits. */
+static void
+expand_SA(void *p, u32 n)
+{
+ typedef u32 _may_alias_attribute aliased_u32_t;
+ typedef u64 _may_alias_attribute aliased_u64_t;
+
+ aliased_u32_t *SA = p;
+ aliased_u64_t *SA64 = p;
+
+ u32 r = n - 1;
+ do {
+ SA64[r] = SA[r];
+ } while (r--);
+}
+
+/* Like build_LCP(), but for buffers larger than MAX_NORMAL_BUFSIZE. */
+static void
+build_LCP_huge(u64 SA_and_LCP64[restrict], const u32 ISA[restrict],
+ const u8 T[restrict], const u32 n,
+ const u32 min_lcp, const u32 max_lcp)
+{
+ u32 h = 0;
+ for (u32 i = 0; i < n; i++) {
+ const u32 r = ISA[i];
+ prefetchw(&SA_and_LCP64[ISA[i + PREFETCH_SAFETY]]);
+ if (r > 0) {
+ const u32 j = SA_and_LCP64[r - 1] & HUGE_POS_MASK;
+ const u32 lim = min(n - i, n - j);
+ while (h < lim && T[i + h] == T[j + h])
+ h++;
+ u32 stored_lcp = h;
+ if (stored_lcp < min_lcp)
+ stored_lcp = 0;
+ else if (stored_lcp > max_lcp)
+ stored_lcp = max_lcp;
+ SA_and_LCP64[r] |= (u64)stored_lcp << HUGE_LCP_SHIFT;
+ if (h > 0)
+ h--;
+ }
+ }
+}
+
+/*
+ * Like build_LCPIT(), but for buffers larger than MAX_NORMAL_BUFSIZE.
+ *
+ * This "huge" version is also slightly different in that the lcp value stored
+ * in each intervals[] entry is the lcp value for that interval, not its
+ * superinterval. This lcp value stays put in intervals[] and doesn't get moved
+ * to pos_data[] during lcpit_advance_one_byte_huge(). One consequence of this
+ * is that we have to use a special flag to distinguish visited from unvisited
+ * intervals. But overall, this scheme keeps the memory usage at 12n instead of
+ * 16n. (The non-huge version is 8n.)
+ */
+static void
+build_LCPIT_huge(u64 intervals64[restrict], u32 pos_data[restrict], const u32 n)
+{
+ u64 * const SA_and_LCP64 = intervals64;
+ u32 next_interval_idx;
+ u32 open_intervals[HUGE_LCP_MAX + 1];
+ u32 *top = open_intervals;
+ u32 prev_pos = SA_and_LCP64[0] & HUGE_POS_MASK;
+
+ *top = 0;
+ intervals64[0] = 0;
+ next_interval_idx = 1;
+
+ for (u32 r = 1; r < n; r++) {
+ const u32 next_pos = SA_and_LCP64[r] & HUGE_POS_MASK;
+ const u64 next_lcp = SA_and_LCP64[r] & HUGE_LCP_MASK;
+ const u64 top_lcp = intervals64[*top];
+
+ prefetchw(&pos_data[SA_and_LCP64[r + PREFETCH_SAFETY] & HUGE_POS_MASK]);
+
+ if (next_lcp == top_lcp) {
+ /* Continuing the deepest open interval */
+ pos_data[prev_pos] = *top;
+ } else if (next_lcp > top_lcp) {
+ /* Opening a new interval */
+ intervals64[next_interval_idx] = next_lcp;
+ pos_data[prev_pos] = next_interval_idx;
+ *++top = next_interval_idx++;
+ } else {
+ /* Closing the deepest open interval */
+ pos_data[prev_pos] = *top;
+ for (;;) {
+ const u32 closed_interval_idx = *top--;
+ const u64 superinterval_lcp = intervals64[*top];
+
+ if (next_lcp == superinterval_lcp) {
+ /* Continuing the superinterval */
+ intervals64[closed_interval_idx] |=
+ HUGE_UNVISITED_TAG | *top;
+ break;
+ } else if (next_lcp > superinterval_lcp) {
+ /* Creating a new interval that is a
+ * superinterval of the one being
+ * closed, but still a subinterval of
+ * its superinterval */
+ intervals64[next_interval_idx] = next_lcp;
+ intervals64[closed_interval_idx] |=
+ HUGE_UNVISITED_TAG | next_interval_idx;
+ *++top = next_interval_idx++;
+ break;
+ } else {
+ /* Also closing the superinterval */
+ intervals64[closed_interval_idx] |=
+ HUGE_UNVISITED_TAG | *top;
+ }
+ }
+ }
+ prev_pos = next_pos;
+ }
+
+ /* Close any still-open intervals. */
+ pos_data[prev_pos] = *top;
+ for (; top > open_intervals; top--)
+ intervals64[*top] |= HUGE_UNVISITED_TAG | *(top - 1);
+}
+
+/* Like lcpit_advance_one_byte(), but for buffers larger than
+ * MAX_NORMAL_BUFSIZE. */
+static forceinline u32
+lcpit_advance_one_byte_huge(const u32 cur_pos,
+ u32 pos_data[restrict],
+ u64 intervals64[restrict],
+ u32 prefetch_next[restrict],
+ struct lz_match matches[restrict],
+ const bool record_matches)
+{
+ u32 interval_idx;
+ u32 next_interval_idx;
+ u64 cur;
+ u64 next;
+ u32 match_pos;
+ struct lz_match *matchptr;
+
+ interval_idx = pos_data[cur_pos];
+
+ prefetchw(&intervals64[pos_data[prefetch_next[0]] & HUGE_POS_MASK]);
+
+ prefetch_next[0] = intervals64[prefetch_next[1]] & HUGE_POS_MASK;
+ prefetchw(&pos_data[prefetch_next[0]]);
+
+ prefetch_next[1] = pos_data[cur_pos + 3] & HUGE_POS_MASK;
+ prefetchw(&intervals64[prefetch_next[1]]);
+
+ pos_data[cur_pos] = 0;
+
+ while ((next = intervals64[interval_idx]) & HUGE_UNVISITED_TAG) {
+ intervals64[interval_idx] = (next & HUGE_LCP_MASK) | cur_pos;
+ interval_idx = next & HUGE_POS_MASK;
+ }
+
+ matchptr = matches;
+ while (next & HUGE_LCP_MASK) {
+ cur = next;
+ do {
+ match_pos = next & HUGE_POS_MASK;
+ next_interval_idx = pos_data[match_pos];
+ next = intervals64[next_interval_idx];
+ } while (next > cur);
+ intervals64[interval_idx] = (cur & HUGE_LCP_MASK) | cur_pos;
+ pos_data[match_pos] = interval_idx;
+ if (record_matches) {
+ matchptr->length = cur >> HUGE_LCP_SHIFT;
+ matchptr->offset = cur_pos - match_pos;
+ matchptr++;
+ }
+ interval_idx = next_interval_idx;
+ }
+ return matchptr - matches;
+}
+
+static forceinline u64
+get_pos_data_size(size_t max_bufsize)
+{
+ return (u64)max((u64)max_bufsize + PREFETCH_SAFETY,
+ DIVSUFSORT_TMP_LEN) * sizeof(u32);
+}
+
+static forceinline u64
+get_intervals_size(size_t max_bufsize)
+{
+ return ((u64)max_bufsize + PREFETCH_SAFETY) *
+ (max_bufsize <= MAX_NORMAL_BUFSIZE ? sizeof(u32) : sizeof(u64));
+}
/*
* Calculate the number of bytes of memory needed for the LCP-interval tree
u64
lcpit_matchfinder_get_needed_memory(size_t max_bufsize)
{
- u64 size = 0;
-
- /* pos_data (+1 is for prefetch) */
- size += ((u64)max_bufsize + 1) * sizeof(u32);
-
- /* intervals or intervals64 */
- size += max((u64)max_bufsize, DIVSUFSORT_TMP_LEN) *
- (max_bufsize <= MAX_NORMAL_BUFSIZE ? sizeof(u32) : sizeof(u64));
-
- /* SA */
- size += (u64)max_bufsize * sizeof(u32);
-
- return size;
+ return get_pos_data_size(max_bufsize) + get_intervals_size(max_bufsize);
}
/*
{
if (lcpit_matchfinder_get_needed_memory(max_bufsize) > SIZE_MAX)
return false;
+ if (max_bufsize > MAX_HUGE_BUFSIZE - PREFETCH_SAFETY)
+ return false;
- mf->pos_data = MALLOC((max_bufsize + 1) * sizeof(u32));
- mf->intervals = MALLOC(max((u64)max_bufsize, DIVSUFSORT_TMP_LEN) *
- (max_bufsize <= MAX_NORMAL_BUFSIZE ?
- sizeof(u32) : sizeof(u64)));
- mf->SA = MALLOC(max_bufsize * sizeof(u32));
-
- if (!mf->pos_data || !mf->intervals || !mf->SA) {
+ mf->pos_data = MALLOC(get_pos_data_size(max_bufsize));
+ mf->intervals = MALLOC(get_intervals_size(max_bufsize));
+ if (!mf->pos_data || !mf->intervals) {
lcpit_matchfinder_destroy(mf);
return false;
}
mf->min_match_len = min_match_len;
- mf->nice_match_len = min(nice_match_len, LCP_MAX);
+ mf->nice_match_len = min(nice_match_len,
+ (max_bufsize <= MAX_NORMAL_BUFSIZE) ?
+ LCP_MAX : HUGE_LCP_MAX);
return true;
}
static void
build_SA(u32 SA[], const u8 T[], u32 n, u32 *tmp)
{
- /* Note: divsufsort() needs temporary space --- one array with 256
- * spaces and one array with 65536 spaces. The implementation of
- * divsufsort() has been modified from the original to use the provided
- * temporary space instead of allocating its own, since we don't want to
- * have to deal with malloc() failures here. */
+ /* Note: divsufsort() requires a fixed amount of temporary space. The
+ * implementation of divsufsort() has been modified from the original to
+ * use the provided temporary space instead of allocating its own, since
+ * we don't want to have to deal with malloc() failures here. */
divsufsort(T, SA, n, tmp);
}
*
* @mf - the initialized matchfinder structure
* @T - the input buffer
- * @n - size of the input buffer in bytes. This may be at most the max_bufsize
- * with which lcpit_matchfinder_init() was called.
+ * @n - size of the input buffer in bytes. This must be nonzero and can be at
+ * most the max_bufsize with which lcpit_matchfinder_init() was called.
*/
void
lcpit_matchfinder_load_buffer(struct lcpit_matchfinder *mf, const u8 *T, u32 n)
{
- if (n == 0)
- return;
+ /* intervals[] temporarily stores SA and LCP packed together.
+ * pos_data[] temporarily stores ISA.
+ * pos_data[] is also used as the temporary space for divsufsort(). */
- build_SA(mf->SA, T, n, mf->intervals);
- build_ISA(mf->pos_data, mf->SA, n);
+ build_SA(mf->intervals, T, n, mf->pos_data);
+ build_ISA(mf->pos_data, mf->intervals, n);
if (n <= MAX_NORMAL_BUFSIZE) {
- /* "Normal" sized buffer */
-
- /* Build LCP, packing it into ->SA */
- build_LCP_normal(mf->SA, mf->pos_data, T, n,
- mf->min_match_len, mf->nice_match_len);
- /* Prepare ->intervals and ->pos_data */
- build_LCPIT_normal(mf->SA, mf->intervals, mf->pos_data, n);
+ for (u32 i = 0; i < PREFETCH_SAFETY; i++) {
+ mf->intervals[n + i] = 0;
+ mf->pos_data[n + i] = 0;
+ }
+ build_LCP(mf->intervals, mf->pos_data, T, n,
+ mf->min_match_len, mf->nice_match_len);
+ build_LCPIT(mf->intervals, mf->pos_data, n);
mf->huge_mode = false;
} else {
- /* "Huge" sized buffer */
-
- /* Build LCP in the second half of ->intervals64. It may be
- * partially overwritten in build_LCPIT_huge(), but this is okay
- * since each LCP entry is guaranteed to be consumed before it
- * can possibly be overwritten. */
- build_LCP_huge(mf->intervals + n, mf->SA, mf->pos_data, T, n,
+ for (u32 i = 0; i < PREFETCH_SAFETY; i++) {
+ mf->intervals64[n + i] = 0;
+ mf->pos_data[n + i] = 0;
+ }
+ expand_SA(mf->intervals, n);
+ build_LCP_huge(mf->intervals64, mf->pos_data, T, n,
mf->min_match_len, mf->nice_match_len);
- /* Prepare ->intervals64 and ->pos_data */
- build_LCPIT_huge(mf->SA, mf->intervals + n, mf->intervals64,
- mf->pos_data, n);
+ build_LCPIT_huge(mf->intervals64, mf->pos_data, n);
mf->huge_mode = true;
}
mf->cur_pos = 0; /* starting at beginning of input buffer */
- mf->pos_data[n] = 0; /* safety entry for prefetch() overrun */
+ for (u32 i = 0; i < ARRAY_LEN(mf->next); i++)
+ mf->next[i] = 0;
}
/*
*
* The return value is the number of matches found and written to @matches.
* This can be any value in [0, nice_match_len - min_match_len + 1].
- *
- * If the caller attempts to advance beyond the end of the input buffer, the
- * behavior is undefined.
*/
u32
lcpit_matchfinder_get_matches(struct lcpit_matchfinder *mf,
struct lz_match *matches)
{
if (mf->huge_mode)
- return lcpit_advance_one_byte_huge(mf, matches, true);
+ return lcpit_advance_one_byte_huge(mf->cur_pos++, mf->pos_data,
+ mf->intervals64, mf->next,
+ matches, true);
else
- return lcpit_advance_one_byte_normal(mf, matches, true);
+ return lcpit_advance_one_byte(mf->cur_pos++, mf->pos_data,
+ mf->intervals, mf->next,
+ matches, true);
}
/*
* Skip the next @count bytes (don't search for matches at them). @count is
* assumed to be > 0.
- *
- * If the caller attempts to advance beyond the end of the input buffer, the
- * behavior is undefined.
*/
void
lcpit_matchfinder_skip_bytes(struct lcpit_matchfinder *mf, u32 count)
{
if (mf->huge_mode) {
do {
- lcpit_advance_one_byte_huge(mf, NULL, false);
+ lcpit_advance_one_byte_huge(mf->cur_pos++, mf->pos_data,
+ mf->intervals64, mf->next,
+ NULL, false);
} while (--count);
} else {
do {
- lcpit_advance_one_byte_normal(mf, NULL, false);
+ lcpit_advance_one_byte(mf->cur_pos++, mf->pos_data,
+ mf->intervals, mf->next,
+ NULL, false);
} while (--count);
}
}
/*
* Destroy an LCP-interval tree matchfinder that was previously initialized with
* lcpit_matchfinder_init().
- *
- * If the struct has been zeroed out, this has no effect.
*/
void
lcpit_matchfinder_destroy(struct lcpit_matchfinder *mf)
{
FREE(mf->pos_data);
FREE(mf->intervals);
- FREE(mf->SA);
- memset(mf, 0, sizeof(*mf));
}
git://wimlib.net / wimlib / blobdiff