* and certain other details are quite similar, such as the method for storing
* Huffman codes. However, some of the main differences are:
*
- * - LZX preprocesses the data before attempting to compress it.
+ * - LZX preprocesses the data to attempt to make x86 machine code slightly more
+ * compressible before attempting to compress it further.
* - LZX uses a "main" alphabet which combines literals and matches, with the
* match symbols containing a "length header" (giving all or part of the match
* length) and a "position slot" (giving, roughly speaking, the order of
* dynamic Huffman blocks ("aligned offset" and "verbatim").
* - LZX has a minimum match length of 2 rather than 3.
* - In LZX, match offsets 0 through 2 actually represent entries in an LRU
- * queue of match offsets.
+ * queue of match offsets. This is very useful for certain types of files,
+ * such as binary files that have repeating records.
*
* Algorithms
* ==========
* 1. Preprocess the input data to translate the targets of x86 call instructions
* to absolute offsets.
*
- * 2. Build the suffix array and inverse suffix array for the input data.
+ * 2. Build the suffix array and inverse suffix array for the input data. The
+ * suffix array contains the indices of all suffixes of the input data,
+ * sorted lexcographically by the corresponding suffixes. The "position" of
+ * a suffix is the index of that suffix in the original string, whereas the
+ * "rank" of a suffix is the index at which that suffix's position is found
+ * in the suffix array.
*
* 3. Build the longest common prefix array corresponding to the suffix array.
*
- * 4. For each suffix rank, find the highest lower suffix rank that has a
- * lower position, the lowest higher suffix rank that has a lower position,
- * and the length of the common prefix shared between each. (Position =
- * index of suffix in original string, rank = index of suffix in suffix
- * array.) This information is later used to link suffix ranks into a
- * doubly-linked list for searching the suffix array.
+ * 4. For each suffix, find the highest lower ranked suffix that has a
+ * lower position, the lowest higher ranked suffix that has a lower position,
+ * and the length of the common prefix shared between each. This
+ * information is later used to link suffix ranks into a doubly-linked list
+ * for searching the suffix array.
*
* 5. Set a default cost model for matches/literals.
*
* and literal bytes to divide the input into. Raw match-finding is done by
* searching the suffix array using a linked list to avoid considering any
* suffixes that start after the current position. Each run of the
- * match-finder returns the lowest-cost longest match as well as any shorter
- * matches that have even lower costs. Each such run also adds the suffix
- * rank of the current position into the linked list being used to search the
- * suffix array. Parsing, or match-choosing, is solved as a minimum-cost
- * path problem using a forward "optimal parsing" algorithm based on the
- * Deflate encoder from 7-Zip. This algorithm moves forward calculating the
- * minimum cost to reach each byte until either a very long match is found or
- * until a position is found at which no matches start or overlap.
+ * match-finder returns the approximate lowest-cost longest match as well as
+ * any shorter matches that have even lower approximate costs. Each such run
+ * also adds the suffix rank of the current position into the linked list
+ * being used to search the suffix array. Parsing, or match-choosing, is
+ * solved as a minimum-cost path problem using a forward "optimal parsing"
+ * algorithm based on the Deflate encoder from 7-Zip. This algorithm moves
+ * forward calculating the minimum cost to reach each byte until either a
+ * very long match is found or until a position is found at which no matches
+ * start or overlap.
*
* 7. Build the Huffman codes needed to output the matches/literals.
*
* 9. Output the resulting block using the match/literal sequences and the
* Huffman codes that were computed for the block.
*
+ * Note: the algorithm does not yet attempt to split the input into multiple LZX
+ * blocks.
+ *
* Fast algorithm
* --------------
*
* The fast algorithm (and the only one available in wimlib v1.5.1 and earlier)
* spends much less time on the main bottlenecks of the compression process ---
- * that is the match finding, match choosing, and block splitting. Matches are
- * found and chosen with hash chains using a greedy parse with one position of
- * look-ahead. No block splitting is done; only compressing the full input into
- * an aligned offset block is considered.
+ * that is, the match finding and match choosing. Matches are found and chosen
+ * with hash chains using a greedy parse with one position of look-ahead. No
+ * block splitting is done; only compressing the full input into an aligned
+ * offset block is considered.
*
* API
* ===
* wimlib_lzx_alloc_context()
* wimlib_lzx_compress2()
* wimlib_lzx_free_context()
+ * wimlib_lzx_set_default_params()
*
* Both wimlib_lzx_compress() and wimlib_lzx_compress2() are designed to
* compress an in-memory buffer of up to 32768 bytes. There is no sliding
* Again, this is suitable for the WIM format, which stores such data chunks
* uncompressed.
*
- * The functions in this API are exported from the library, although this is
- * only in case other programs happen to have uses for it other than WIM
+ * The functions in this LZX compression API are exported from the library,
+ * although with the possible exception of wimlib_lzx_set_default_params(), this
+ * is only in case other programs happen to have uses for it other than WIM
* reading/writing as already handled through the rest of the library.
*
* Acknowledgments
* Acknowledgments to several open-source projects and research papers that made
* it possible to implement this code:
*
- * - divsufsort (author: Yuta Mori), for the suffix array construction code.
+ * - divsufsort (author: Yuta Mori), for the suffix array construction code,
+ * located in a separate directory (divsufsort/).
*
* - "Linear-Time Longest-Common-Prefix Computation in Suffix Arrays and Its
* Applications" (Kasai et al. 2001), for the LCP array computation.
* (match-choosing).
*
* - zlib (author: Jean-loup Gailly and Mark Adler), for the hash table
- * match-finding algorithm.
+ * match-finding algorithm (used in lz77.c).
*
* - lzx-compress (author: Matthew T. Russotto), on which some parts of this
* code were originally based.
#include "divsufsort/divsufsort.h"
typedef freq_t input_idx_t;
-typedef u32 sym_cost_t;
typedef u32 block_cost_t;
-#define INFINITE_SYM_COST ((sym_cost_t)~0U)
#define INFINITE_BLOCK_COST ((block_cost_t)~0U)
#define LZX_OPTIM_ARRAY_SIZE 4096
* --- generally a high cost, since even if it gets used in the next iteration,
* it probably will not be used very times. */
struct lzx_costs {
- sym_cost_t main[LZX_MAINCODE_NUM_SYMBOLS];
- sym_cost_t len[LZX_LENCODE_NUM_SYMBOLS];
- sym_cost_t aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS];
+ u8 main[LZX_MAINCODE_NUM_SYMBOLS];
+ u8 len[LZX_LENCODE_NUM_SYMBOLS];
+ u8 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS];
};
/* The LZX main, length, and aligned offset Huffman codes */
* block. */
struct lzx_match *chosen_matches;
- struct raw_match *cached_matches;
- unsigned cached_matches_pos;
- bool matches_cached;
-
/* Information about the LZX blocks the preprocessed input was divided
* into. */
struct lzx_block_spec *block_specs;
* codewords. */
struct lzx_codes zero_codes;
- /* Slow algorithm only: The current cost model. */
+ /* The current cost model. */
struct lzx_costs costs;
- /* Slow algorithm only: Suffix array for window.
- * This is a mapping from suffix rank to suffix position.
- *
- * Suffix rank means the index of the suffix in the sorted list of
- * suffixes, whereas suffix position means the index in the string at
- * which the suffix starts.
- */
+ /* Suffix array for window.
+ * This is a mapping from suffix rank to suffix position. */
input_idx_t *SA;
- /* Slow algorithm only: Inverse suffix array for window.
+ /* Inverse suffix array for window.
* This is a mapping from suffix position to suffix rank.
- * In other words, if 0 <= r < window_size, then ISA[SA[r]] == r. */
+ * If 0 <= r < window_size, then ISA[SA[r]] == r. */
input_idx_t *ISA;
- /* Slow algorithm only: Longest Common Prefix array. LCP[i] is the
- * number of initial bytes that the suffixes at positions SA[i - 1] and
- * SA[i] share. LCP[0] is undefined. */
- input_idx_t *LCP;
-
- /* Slow algorithm only: Suffix array links.
+ /* Suffix array links.
*
* During a linear scan of the input string to find matches, this array
* used to keep track of which rank suffixes in the suffix array appear
* list containing only suffixes that appear before that position. */
struct salink *salink;
- /* Slow algorithm only: Position in window of next match to return.
- * This cannot simply be modified, as the match-finder must still be
- * synchronized on the same position. To seek forwards or backwards,
+ /* Position in window of next match to return.
+ * Note: This cannot simply be modified, as the match-finder must still
+ * be synchronized on the same position. To seek forwards or backwards,
* use lzx_lz_skip_bytes() or lzx_lz_rewind_matchfinder(), respectively.
*/
input_idx_t match_window_pos;
- /* Slow algorithm only: The match-finder shall ensure the length of
- * matches does not exceed this position in the input. */
+ /* The match-finder shall ensure the length of matches does not exceed
+ * this position in the input. */
input_idx_t match_window_end;
+ /* Matches found by the match-finder are cached in the following array
+ * to achieve a slight speedup when the same matches are needed on
+ * subsequent passes. This is suboptimal because different matches may
+ * be preferred with different cost models, but seems to be a worthwhile
+ * speedup. */
+ struct raw_match *cached_matches;
+ unsigned cached_matches_pos;
+ bool matches_cached;
+
/* Slow algorithm only: Temporary space used for match-choosing
* algorithm.
*
* numbers in the lzx_position_base array to calculate the slot directly from
* the formatted offset without actually looking at the array.
*/
-static _always_inline_attribute unsigned
+static unsigned
lzx_get_position_slot_raw(unsigned formatted_offset)
{
#if 0
/* Returns the LZX position slot that corresponds to a given match offset,
- * taking into account the recent offset queue (and optionally updating it). */
-static _always_inline_attribute unsigned
+ * taking into account the recent offset queue and updating it if the offset is
+ * found in it. */
+static unsigned
lzx_get_position_slot(unsigned offset, struct lzx_lru_queue *queue)
{
unsigned position_slot;
* LRU queue because repeat matches are simply
* swapped to the front. */
swap(queue->R[0], queue->R[i]);
- /* For recent offsets, the position slot is simply the
- * index of the entry in the queue. */
+ /* The resulting position slot is simply the first index
+ * at which the offset was found in the queue. */
return i;
}
}
/* Returns the cost, in bits, to output a literal byte using the specified cost
* model. */
-static sym_cost_t
+static unsigned
lzx_literal_cost(u8 c, const struct lzx_costs * costs)
{
return costs->main[c];
* codes, return the approximate number of bits it will take to represent this
* match in the compressed output. Take into account the match offset LRU
* queue and optionally update it. */
-static sym_cost_t
+static unsigned
lzx_match_cost(unsigned length, unsigned offset, const struct lzx_costs *costs,
struct lzx_lru_queue *queue)
{
unsigned position_slot;
unsigned len_header, main_symbol;
- sym_cost_t cost = 0;
+ unsigned cost = 0;
position_slot = lzx_get_position_slot(offset, queue);
len_header = min(length - LZX_MIN_MATCH_LEN, LZX_NUM_PRIMARY_LENS);
- main_symbol = (position_slot << 3) | len_header | LZX_NUM_CHARS;
+ main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS;
/* Account for main symbol. */
cost += costs->main[main_symbol];
}
-/* Very fast heuristic cost evaluation to use in the inner loop of the
- * match-finder. */
-static sym_cost_t
+/* Fast heuristic cost evaluation to use in the inner loop of the match-finder.
+ * Unlike lzx_match_cost() which does a true cost evaluation, this simply
+ * prioritize matches based on their offset. */
+static block_cost_t
lzx_match_cost_fast(unsigned offset, const struct lzx_lru_queue *queue)
{
+ /* It seems well worth it to take the time to give priority to recently
+ * used offsets. */
for (unsigned i = 0; i < LZX_NUM_RECENT_OFFSETS; i++)
if (offset == queue->R[i])
return i;
- BUILD_BUG_ON(LZX_MAX_WINDOW_SIZE >= (sym_cost_t)~0U);
+ BUILD_BUG_ON(LZX_MAX_WINDOW_SIZE >= (block_cost_t)~0U);
return offset;
}
if (ctx->match_window_pos == orig_pos)
return;
+ /* NOTE: this has been optimized for the current algorithm where no
+ * block-splitting is done and matches are cached, so that the suffix
+ * array match-finder only runs through the input one time. Generalized
+ * rewinds of the suffix array match-finder are possible, but require
+ * incrementally saving fields being overwritten in
+ * lzx_lz_update_salink(), then restoring them here in reverse order.
+ */
+
LZX_ASSERT(ctx->match_window_pos > orig_pos);
LZX_ASSERT(orig_pos == 0);
ctx->matches_cached = true;
* We keep track of this so that we can ignore shorter matches that do
* not have lower costs than a longer matches already found.
*/
- sym_cost_t best_cost = INFINITE_SYM_COST;
+ block_cost_t best_cost = INFINITE_BLOCK_COST;
/* count_remaining = maximum number of possible matches remaining to be
* considered. */
/* pending = match currently being considered for a specific length. */
struct raw_match pending;
+ block_cost_t pending_cost;
while (lenL >= min_match_len || lenR >= min_match_len)
{
pending.len = lenL;
- pending.offset = (input_idx_t)~0U;
- sym_cost_t pending_cost = INFINITE_SYM_COST;
- sym_cost_t cost;
+ pending_cost = INFINITE_BLOCK_COST;
+ block_cost_t cost;
/* Extend left. */
if (lenL >= min_match_len && lenL >= lenR) {
return nmatches;
}
pending.len = lenL;
- pending.offset = (input_idx_t)~0U;
- pending_cost = INFINITE_SYM_COST;
+ pending_cost = INFINITE_BLOCK_COST;
}
if (lenL < min_match_len || lenL < lenR)
break;
break;
pending.len = lenR;
- pending.offset = (input_idx_t)~0U;
- pending_cost = INFINITE_SYM_COST;
+ pending_cost = INFINITE_BLOCK_COST;
}
R = link[R].next;
}
goto out;
out_save_pending:
- if (pending.offset != (input_idx_t)~0U)
+ if (pending_cost != INFINITE_BLOCK_COST)
matches[nmatches++] = pending;
out:
num_matches = matches[-1].len;
} else {
unsigned min_match_len = LZX_MIN_MATCH_LEN;
- if (min_match_len <= 2 && !ctx->params.alg_params.slow.use_len2_matches)
- min_match_len = 3;
+ if (!ctx->params.alg_params.slow.use_len2_matches)
+ min_match_len = max(min_match_len, 3);
const uint32_t max_search_depth = ctx->params.alg_params.slow.max_search_depth;
const uint32_t max_matches_per_pos = ctx->params.alg_params.slow.max_matches_per_pos;
* model rather than simply assuming that longer is better.
*
* Still, this is not truly an optimal parser because very long matches are
- * taken immediately. This is done to avoid considering many different
- * alternatives that are unlikely to significantly be better.
+ * taken immediately, and the raw match-finder takes some shortcuts. This is
+ * done to avoid considering many different alternatives that are unlikely to
+ * be significantly better.
*
* This algorithm is based on that used in 7-Zip's DEFLATE encoder.
*
* ctx->optimum (internal state; leave uninitialized)
* ctx->optimum_cur_idx (must set to 0 before first call)
* ctx->optimum_end_idx (must set to 0 before first call)
- * ctx->SA (must be built before first call)
- * ctx->ISA (must be built before first call)
- * ctx->salink (must be built before first call)
- * ctx->match_window_pos (must initialize to position of next match to
- * return; subsequent calls return subsequent
- * matches)
- * ctx->match_window_end (must initialize to limit of match-finding region;
- * subsequent calls use the same limit)
+ *
+ * Plus any state used by the raw match-finder.
*
* The return value is a (length, offset) pair specifying the match or literal
* chosen. For literals, the length is less than LZX_MIN_MATCH_LEN and the
}
/* Find a near-optimal sequence of matches/literals with which to output the
- * specified LZX block, and set its type to that which has the minimum cost to
+ * specified LZX block, then set its type to that which has the minimum cost to
* output. */
static void
lzx_optimize_block(struct lzx_compressor *ctx, struct lzx_block_spec *spec,
unsigned num_passes)
{
- struct lzx_lru_queue orig_queue = ctx->queue;
+ const struct lzx_lru_queue orig_queue = ctx->queue;
struct lzx_freqs freqs;
ctx->match_window_end = spec->window_pos + spec->block_size;
const input_idx_t n,
input_idx_t SA[const restrict],
input_idx_t ISA[const restrict],
- input_idx_t LCP[const restrict],
struct salink link[const restrict],
const unsigned max_match_len)
{
for (input_idx_t r = 0; r < n; r++)
ISA[SA[r]] = r;
- /* Compute LCP (longest common prefix) array.
- *
- * Algorithm adapted from Kasai et al. 2001: "Linear-Time
- * Longest-Common-Prefix Computation in Suffix Arrays and Its
- * Applications". */
{
- input_idx_t h = 0;
- for (input_idx_t i = 0; i < n; i++) {
- input_idx_t r = ISA[i];
- if (r > 0) {
- input_idx_t j = SA[r - 1];
-
- input_idx_t lim = min(n - i, n - j);
-
- while (h < lim && T[i + h] == T[j + h])
- h++;
- LCP[r] = h;
- if (h > 0)
- h--;
+ input_idx_t LCP[n];
+ /* Compute LCP (longest common prefix) array.
+ *
+ * Algorithm adapted from Kasai et al. 2001: "Linear-Time
+ * Longest-Common-Prefix Computation in Suffix Arrays and Its
+ * Applications". */
+ {
+ input_idx_t h = 0;
+ for (input_idx_t i = 0; i < n; i++) {
+ input_idx_t r = ISA[i];
+ if (r > 0) {
+ input_idx_t j = SA[r - 1];
+
+ input_idx_t lim = min(n - i, n - j);
+
+ while (h < lim && T[i + h] == T[j + h])
+ h++;
+ LCP[r] = h;
+ if (h > 0)
+ h--;
+ }
}
}
- }
-#ifdef ENABLE_LZX_DEBUG
- /* Verify LCP array. */
- for (input_idx_t r = 0; r < n - 1; r++) {
- LZX_ASSERT(ISA[SA[r]] == r);
- LZX_ASSERT(ISA[SA[r + 1]] == r + 1);
+ #ifdef ENABLE_LZX_DEBUG
+ /* Verify LCP array. */
+ for (input_idx_t r = 0; r < n - 1; r++) {
+ LZX_ASSERT(ISA[SA[r]] == r);
+ LZX_ASSERT(ISA[SA[r + 1]] == r + 1);
- input_idx_t i1 = SA[r];
- input_idx_t i2 = SA[r + 1];
- input_idx_t lcp = LCP[r + 1];
+ input_idx_t i1 = SA[r];
+ input_idx_t i2 = SA[r + 1];
+ input_idx_t lcp = LCP[r + 1];
- input_idx_t n1 = n - i1;
- input_idx_t n2 = n - i2;
+ input_idx_t n1 = n - i1;
+ input_idx_t n2 = n - i2;
- LZX_ASSERT(lcp <= min(n1, n2));
+ LZX_ASSERT(lcp <= min(n1, n2));
- LZX_ASSERT(memcmp(&T[i1], &T[i2], lcp) == 0);
- if (lcp < min(n1, n2))
- LZX_ASSERT(T[i1 + lcp] != T[i2 + lcp]);
- }
-#endif /* ENABLE_LZX_DEBUG */
+ LZX_ASSERT(memcmp(&T[i1], &T[i2], lcp) == 0);
+ if (lcp < min(n1, n2))
+ LZX_ASSERT(T[i1 + lcp] != T[i2 + lcp]);
+ }
+ #endif /* ENABLE_LZX_DEBUG */
- /* Compute salink.next and salink.lcpnext.
- *
- * Algorithm adapted from Crochemore et al. 2009:
- * "LPF computation revisited".
- *
- * Note: we cap lcpnext to the maximum match length so that the
- * match-finder need not worry about it later. */
- link[n - 1].next = (input_idx_t)~0U;
- link[n - 1].prev = (input_idx_t)~0U;
- link[n - 1].lcpnext = 0;
- link[n - 1].lcpprev = 0;
- for (input_idx_t r = n - 2; r != (input_idx_t)~0U; r--) {
- input_idx_t t = r + 1;
- input_idx_t l = LCP[t];
- while (t != (input_idx_t)~0 && SA[t] > SA[r]) {
- l = min(l, link[t].lcpnext);
- t = link[t].next;
+ /* Compute salink.next and salink.lcpnext.
+ *
+ * Algorithm adapted from Crochemore et al. 2009:
+ * "LPF computation revisited".
+ *
+ * Note: we cap lcpnext to the maximum match length so that the
+ * match-finder need not worry about it later. */
+ link[n - 1].next = (input_idx_t)~0U;
+ link[n - 1].prev = (input_idx_t)~0U;
+ link[n - 1].lcpnext = 0;
+ link[n - 1].lcpprev = 0;
+ for (input_idx_t r = n - 2; r != (input_idx_t)~0U; r--) {
+ input_idx_t t = r + 1;
+ input_idx_t l = LCP[t];
+ while (t != (input_idx_t)~0 && SA[t] > SA[r]) {
+ l = min(l, link[t].lcpnext);
+ t = link[t].next;
+ }
+ link[r].next = t;
+ link[r].lcpnext = min(l, max_match_len);
+ LZX_ASSERT(t == (input_idx_t)~0U || l <= n - SA[t]);
+ LZX_ASSERT(l <= n - SA[r]);
+ LZX_ASSERT(memcmp(&T[SA[r]], &T[SA[t]], l) == 0);
}
- link[r].next = t;
- link[r].lcpnext = min(l, max_match_len);
- LZX_ASSERT(t == (input_idx_t)~0 || l <= n - SA[t]);
- LZX_ASSERT(l <= n - SA[r]);
- LZX_ASSERT(memcmp(&T[SA[r]], &T[SA[t]], l) == 0);
- }
- /* Compute salink.prev and salink.lcpprev.
- *
- * Algorithm adapted from Crochemore et al. 2009:
- * "LPF computation revisited".
- *
- * Note: we cap lcpprev to the maximum match length so that the
- * match-finder need not worry about it later. */
- link[0].prev = (input_idx_t)~0;
- link[0].next = (input_idx_t)~0;
- link[0].lcpprev = 0;
- link[0].lcpnext = 0;
- for (input_idx_t r = 1; r < n; r++) {
- input_idx_t t = r - 1;
- input_idx_t l = LCP[r];
- while (t != (input_idx_t)~0 && SA[t] > SA[r]) {
- l = min(l, link[t].lcpprev);
- t = link[t].prev;
+ /* Compute salink.prev and salink.lcpprev.
+ *
+ * Algorithm adapted from Crochemore et al. 2009:
+ * "LPF computation revisited".
+ *
+ * Note: we cap lcpprev to the maximum match length so that the
+ * match-finder need not worry about it later. */
+ link[0].prev = (input_idx_t)~0;
+ link[0].next = (input_idx_t)~0;
+ link[0].lcpprev = 0;
+ link[0].lcpnext = 0;
+ for (input_idx_t r = 1; r < n; r++) {
+ input_idx_t t = r - 1;
+ input_idx_t l = LCP[r];
+ while (t != (input_idx_t)~0 && SA[t] > SA[r]) {
+ l = min(l, link[t].lcpprev);
+ t = link[t].prev;
+ }
+ link[r].prev = t;
+ link[r].lcpprev = min(l, max_match_len);
+ LZX_ASSERT(t == (input_idx_t)~0 || l <= n - SA[t]);
+ LZX_ASSERT(l <= n - SA[r]);
+ LZX_ASSERT(memcmp(&T[SA[r]], &T[SA[t]], l) == 0);
}
- link[r].prev = t;
- link[r].lcpprev = min(l, max_match_len);
- LZX_ASSERT(t == (input_idx_t)~0 || l <= n - SA[t]);
- LZX_ASSERT(l <= n - SA[r]);
- LZX_ASSERT(memcmp(&T[SA[r]], &T[SA[t]], l) == 0);
}
}
{
/* Initialize the match-finder. */
lzx_lz_init_matchfinder(ctx->window, ctx->window_size,
- ctx->SA, ctx->ISA, ctx->LCP, ctx->salink,
+ ctx->SA, ctx->ISA, ctx->salink,
LZX_MAX_MATCH_LEN);
ctx->cached_matches_pos = 0;
ctx->matches_cached = false;
/* Set up a default cost model. */
lzx_set_default_costs(&ctx->costs);
- /* Initially assume that the entire input will be one LZX block. */
- ctx->block_specs[0].block_type = LZX_BLOCKTYPE_ALIGNED;
+ /* Assume that the entire input will be one LZX block. */
ctx->block_specs[0].window_pos = 0;
ctx->block_specs[0].block_size = ctx->window_size;
ctx->num_blocks = 1;
- /* Perform near-optimal LZ parsing. */
+ /* Determine sequence of matches/literals to output for each block. */
lzx_optimize_blocks(ctx);
}
uncompressed_len, compressed_len);
/* Verify that we really get the same thing back when decompressing.
- * TODO: Disable this check by default on the slow algorithm. */
+ * Although this could be disabled by default in all cases, it only
+ * takes around 2-3% of the running time of the slow algorithm to do the
+ * verification. */
if (ctx->params.algorithm == WIMLIB_LZX_ALGORITHM_SLOW
#if defined(ENABLE_LZX_DEBUG) || defined(ENABLE_VERIFY_COMPRESSION)
|| 1
if (ctx->SA == NULL)
goto err_free_block_specs;
ctx->ISA = ctx->SA + LZX_MAX_WINDOW_SIZE;
- ctx->LCP = ctx->ISA + LZX_MAX_WINDOW_SIZE;
ctx->salink = MALLOC(LZX_MAX_WINDOW_SIZE * sizeof(ctx->salink[0]));
if (ctx->salink == NULL)
goto err_free_SA;
} else {
ctx->SA = NULL;
ctx->ISA = NULL;
- ctx->LCP = NULL;
ctx->salink = NULL;
}
struct lzx_compressor *ctx = (struct lzx_compressor*)_ctx;
if (ctx) {
- FREE(ctx->cached_matches);
FREE(ctx->chosen_matches);
+ FREE(ctx->cached_matches);
FREE(ctx->optimum);
- FREE(ctx->SA);
FREE(ctx->salink);
+ FREE(ctx->SA);
FREE(ctx->block_specs);
FREE(ctx);
}