X-Git-Url: https://wimlib.net/git/?p=wimlib;a=blobdiff_plain;f=src%2Flz_sarray.c;h=33acd61237022b56699f5f1bc07e3ffa81af3c18;hp=5e0fa7faff227beb16301f80aac3c95232f0b9e4;hb=31274ba5cbf4de73c8a68e7d17f490c3b0df6cff;hpb=67e3a69b10498376108c15e5c48b8bb2fc8623e7 diff --git a/src/lz_sarray.c b/src/lz_sarray.c index 5e0fa7fa..33acd612 100644 --- a/src/lz_sarray.c +++ b/src/lz_sarray.c @@ -40,6 +40,9 @@ #include "divsufsort/divsufsort.h" #include +#define DIVSUFSORT_TMP1_SIZE (256 * sizeof(saidx_t)) +#define DIVSUFSORT_TMP2_SIZE (256 * 256 * sizeof(saidx_t)) + /* If ENABLE_LZ_DEBUG is defined, verify that the suffix array satisfies its * definition. * @@ -180,41 +183,112 @@ verify_lcp_array(lz_sarray_pos_t LCP[restrict], * * Note: We cap the lcpprev and lcpnext values to the maximum match length so * that the match-finder need not worry about it later, in the inner loop. + * + * Note: the LCP array is one of the inputs to this function, but it is used as + * temporary space and therefore will be invalidated. */ static void init_salink(struct salink link[restrict], - const lz_sarray_pos_t LCP[restrict], + lz_sarray_pos_t LCP[restrict], const lz_sarray_pos_t SA[restrict], const u8 T[restrict], lz_sarray_pos_t n, + lz_sarray_len_t min_match_len, lz_sarray_len_t max_match_len) { - /* Compute salink.next and salink.lcpnext. */ - link[n - 1].next = LZ_SARRAY_POS_MAX; - link[n - 1].lcpnext = 0; + /* Calculate salink.dist_to_next and salink.lcpnext. + * + * Pass 1 calculates, for each suffix rank, the corresponding + * "next_initial" value which is the smallest larger rank that + * corresponds to a suffix starting earlier in the string. It also + * calculates "lcpnext_initial", which is the number of bytes shared + * with that suffix, although to eliminate checks in + * lz_sarray_get_matches(), "lcpnext_initial" is set to 0 if it's less + * than the minimum match length or set to the maximum match length if + * it's greater than the maximum match length. + * + * Pass 2 translates each absolute "next_initial", a 4-byte value, into + * a relative "dist_to_next", a 1-byte value. This is done to save + * memory. In the case that the true relative distance cannot be + * encoded in 1 byte, it is capped to 255. This is valid as long as + * lz_sarray_get_matches() validates each position before using it. + * Note that "lcpnext" need not be updated in this case because it will + * not be used until the actual next rank has been found anyway. + */ + link[n - 1].next_initial = LZ_SARRAY_POS_MAX; + link[n - 1].lcpnext_initial = 0; for (lz_sarray_pos_t r = n - 2; r != LZ_SARRAY_POS_MAX; r--) { lz_sarray_pos_t t = r + 1; lz_sarray_pos_t l = LCP[t]; while (t != LZ_SARRAY_POS_MAX && SA[t] > SA[r]) { - l = min(l, link[t].lcpnext); - t = link[t].next; + l = min(l, link[t].lcpnext_initial); + t = link[t].next_initial; } - link[r].next = t; - link[r].lcpnext = min(l, max_match_len); + link[r].next_initial = t; + + if (l < min_match_len) + l = 0; + else if (l > max_match_len) + l = max_match_len; + link[r].lcpnext_initial = l; + } + for (lz_sarray_pos_t r = 0; r < n; r++) { + lz_sarray_pos_t next; + lz_sarray_len_t l; + lz_sarray_delta_t dist_to_next; + + next = link[r].next_initial; + l = link[r].lcpnext_initial; + + if (next == LZ_SARRAY_POS_MAX) + dist_to_next = 0; + else if (next - r <= LZ_SARRAY_DELTA_MAX) + dist_to_next = next - r; + else + dist_to_next = LZ_SARRAY_DELTA_MAX; + + link[r].lcpnext = l; + link[r].dist_to_next = dist_to_next; } - /* Compute salink.prev and salink.lcpprev. */ - link[0].prev = LZ_SARRAY_POS_MAX; + /* Calculate salink.dist_to_prev and salink.lcpprev. + * + * This is analgous to dist_to_next and lcpnext as described above, but + * in the other direction. That is, here we're interested in, for each + * rank, the largest smaller rank that corresponds to a suffix starting + * earlier in the string. + * + * To save memory we don't have a "prev_initial" field, but rather store + * those values in the LCP array. + */ + LCP[0] = LZ_SARRAY_POS_MAX; link[0].lcpprev = 0; for (lz_sarray_pos_t r = 1; r < n; r++) { lz_sarray_pos_t t = r - 1; lz_sarray_pos_t l = LCP[r]; while (t != LZ_SARRAY_POS_MAX && SA[t] > SA[r]) { l = min(l, link[t].lcpprev); - t = link[t].prev; + t = LCP[t]; } - link[r].prev = t; - link[r].lcpprev = min(l, max_match_len); + LCP[r] = t; + + if (l < min_match_len) + l = 0; + else if (l > max_match_len) + l = max_match_len; + + link[r].lcpprev = l; + } + for (lz_sarray_pos_t r = 0; r < n; r++) { + + lz_sarray_pos_t prev = LCP[r]; + + if (prev == LZ_SARRAY_POS_MAX) + link[r].dist_to_prev = 0; + else if (r - prev <= LZ_SARRAY_DELTA_MAX) + link[r].dist_to_prev = r - prev; + else + link[r].dist_to_prev = LZ_SARRAY_DELTA_MAX; } } @@ -227,13 +301,14 @@ verify_salink(const struct salink link[], const lz_sarray_pos_t SA[], const u8 T[], lz_sarray_pos_t n, + lz_sarray_len_t min_match_len, lz_sarray_len_t max_match_len) { #ifdef ENABLE_LZ_DEBUG for (lz_sarray_pos_t r = 0; r < n; r++) { for (lz_sarray_pos_t prev = r; ; ) { if (prev == 0) { - LZ_ASSERT(link[r].prev == LZ_SARRAY_POS_MAX); + LZ_ASSERT(link[r].dist_to_prev == 0); LZ_ASSERT(link[r].lcpprev == 0); break; } @@ -241,27 +316,27 @@ verify_salink(const struct salink link[], prev--; if (SA[prev] < SA[r]) { - LZ_ASSERT(link[r].prev == prev); - LZ_ASSERT(link[r].lcpprev <= n - SA[prev]); - LZ_ASSERT(link[r].lcpprev <= n - SA[r]); - LZ_ASSERT(link[r].lcpprev <= max_match_len); - LZ_ASSERT(0 == memcmp(&T[SA[prev]], - &T[SA[r]], - link[r].lcpprev)); - if (link[r].lcpprev < n - SA[prev] && - link[r].lcpprev < n - SA[r] && - link[r].lcpprev < max_match_len) - { - LZ_ASSERT(T[SA[prev] + link[r].lcpprev] != - T[SA[r] + link[r].lcpprev]); - } + LZ_ASSERT(link[r].dist_to_prev == min(r - prev, LZ_SARRAY_DELTA_MAX)); + + lz_sarray_pos_t lcpprev; + for (lcpprev = 0; + lcpprev < min(n - SA[prev], n - SA[r]) && + T[SA[prev] + lcpprev] == T[SA[r] + lcpprev]; + lcpprev++) + ; + if (lcpprev < min_match_len) + lcpprev = 0; + else if (lcpprev > max_match_len) + lcpprev = max_match_len; + + LZ_ASSERT(lcpprev == link[r].lcpprev); break; } } for (lz_sarray_pos_t next = r; ; ) { if (next == n - 1) { - LZ_ASSERT(link[r].next == LZ_SARRAY_POS_MAX); + LZ_ASSERT(link[r].dist_to_next == 0); LZ_ASSERT(link[r].lcpnext == 0); break; } @@ -269,21 +344,20 @@ verify_salink(const struct salink link[], next++; if (SA[next] < SA[r]) { - LZ_ASSERT(link[r].next == next); - LZ_ASSERT(link[r].lcpnext <= n - SA[next]); - LZ_ASSERT(link[r].lcpnext <= n - SA[r]); - LZ_ASSERT(link[r].lcpnext <= max_match_len); - LZ_ASSERT(0 == memcmp(&T[SA[next]], - &T[SA[r]], - link[r].lcpnext)); - if (link[r].lcpnext < n - SA[next] && - link[r].lcpnext < n - SA[r] && - link[r].lcpnext < max_match_len) - { - LZ_ASSERT(T[SA[next] + link[r].lcpnext] != - T[SA[r] + link[r].lcpnext]); - - } + LZ_ASSERT(link[r].dist_to_next == min(next - r, LZ_SARRAY_DELTA_MAX)); + + lz_sarray_pos_t lcpnext; + for (lcpnext = 0; + lcpnext < min(n - SA[next], n - SA[r]) && + T[SA[next] + lcpnext] == T[SA[r] + lcpnext]; + lcpnext++) + ; + if (lcpnext < min_match_len) + lcpnext = 0; + else if (lcpnext > max_match_len) + lcpnext = max_match_len; + + LZ_ASSERT(lcpnext == link[r].lcpnext); break; } } @@ -366,14 +440,17 @@ lz_sarray_init(struct lz_sarray *mf, if ((u64)2 * max_window_size * sizeof(mf->SA[0]) != 2 * max_window_size * sizeof(mf->SA[0])) return false; - mf->SA = MALLOC(2 * max_window_size * sizeof(mf->SA[0])); + mf->SA = MALLOC(max_window_size * sizeof(mf->SA[0]) + + max(DIVSUFSORT_TMP1_SIZE, + max_window_size * sizeof(mf->SA[0]))); if (mf->SA == NULL) return false; if ((u64)max_window_size * sizeof(mf->salink[0]) != max_window_size * sizeof(mf->salink[0])) return false; - mf->salink = MALLOC(max_window_size * sizeof(mf->salink[0])); + mf->salink = MALLOC(max(DIVSUFSORT_TMP2_SIZE, + max_window_size * sizeof(mf->salink[0]))); if (mf->salink == NULL) return false; @@ -384,7 +461,7 @@ lz_sarray_init(struct lz_sarray *mf, * Return the number of bytes of memory that lz_sarray_init() would allocate for * the specified maximum window size. * - * This should be (20 * @max_window_size) unless the type definitions have been + * This should be (14 * @max_window_size) unless the type definitions have been * changed. */ u64 @@ -393,10 +470,13 @@ lz_sarray_get_needed_memory(lz_sarray_pos_t max_window_size) u64 size = 0; /* SA and ISA: 8 bytes per position */ - size += (u64)max_window_size * 2 * sizeof(((struct lz_sarray*)0)->SA[0]); + size += (u64)max_window_size * sizeof(((struct lz_sarray*)0)->SA[0]) + + max(DIVSUFSORT_TMP1_SIZE, + (u64)max_window_size * sizeof(((struct lz_sarray*)0)->SA[0])); - /* salink: 12 bytes per position */ - size += (u64)max_window_size * sizeof(((struct lz_sarray*)0)->salink[0]); + /* salink: 6 bytes per position */ + size += max(DIVSUFSORT_TMP2_SIZE, + (u64)max_window_size * sizeof(((struct lz_sarray*)0)->salink[0])); return size; } @@ -424,18 +504,14 @@ lz_sarray_load_window(struct lz_sarray *mf, const u8 T[], lz_sarray_pos_t n) /* Compute SA (Suffix Array). * * divsufsort() needs temporary space --- one array with 256 spaces and - * one array with 65536 spaces. The implementation has been modified - * from the original to use the provided temporary space instead of - * allocating its own. + * 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. * * We also check at build-time that divsufsort() uses the same integer * size expected by this code. Unfortunately, divsufsort breaks if * 'sa_idx_t' is defined to be a 16-bit integer; however, that would * limit blocks to only 65536 bytes anyway. */ - LZ_ASSERT(mf->max_window_size * sizeof(mf->SA[0]) - >= 256 * sizeof(saidx_t)); - LZ_ASSERT(mf->max_window_size * sizeof(mf->salink[0]) - >= 256 * 256 * sizeof(saidx_t)); BUILD_BUG_ON(sizeof(lz_sarray_pos_t) != sizeof(saidx_t)); divsufsort(T, mf->SA, n, (saidx_t*)&mf->SA[n], (saidx_t*)mf->salink); @@ -452,6 +528,7 @@ lz_sarray_load_window(struct lz_sarray *mf, const u8 T[], lz_sarray_pos_t n) * end. This is probably worth it because computing the ISA from the SA * is very fast, and since this match-finder is memory-hungry we'd like * to save as much memory as possible. */ + BUILD_BUG_ON(sizeof(mf->salink[0]) < sizeof(mf->ISA[0])); ISA = (lz_sarray_pos_t*)mf->salink; compute_inverse_suffix_array(ISA, mf->SA, n); @@ -461,8 +538,10 @@ lz_sarray_load_window(struct lz_sarray *mf, const u8 T[], lz_sarray_pos_t n) verify_lcp_array(LCP, mf->SA, T, n); /* Initialize suffix array links. */ - init_salink(mf->salink, LCP, mf->SA, T, n, mf->max_match_len); - verify_salink(mf->salink, mf->SA, T, n, mf->max_match_len); + init_salink(mf->salink, LCP, mf->SA, T, n, + mf->min_match_len, mf->max_match_len); + verify_salink(mf->salink, mf->SA, T, n, + mf->min_match_len, mf->max_match_len); /* Compute ISA (Inverse Suffix Array) in its final position. */ ISA = mf->SA + n;