struct xpress_mc_pos_data;
struct xpress_compressor_params {
- struct lz_match (*choose_item_func)(struct xpress_compressor *);
+
+ /* Only used when choose_items_func == xpress_choose_items_near_optimal */
u32 num_optim_passes;
+
+ /* Given the data to compress (c->cur_window, c->cur_window_size),
+ * 'choose_items_func' fills in c->chosen_items with the intermediate
+ * representation of the match/literal sequence to output. Also fills
+ * in c->codewords and c->lens to provide the Huffman code with which
+ * these items should be output.
+ *
+ * Returns the number of items written to c->chosen_items. This can be
+ * at most c->cur_window_size. (The worst case is all literals, no
+ * matches.) */
+ u32 (*choose_items_func)(struct xpress_compressor *c);
+
+ /* Match-finding algorithm and parameters */
enum lz_mf_algo mf_algo;
- u32 nice_match_length;
u32 max_search_depth;
+ u32 nice_match_length;
};
/* XPRESS compressor state. */
/* Parameters determined based on the compression level. */
struct xpress_compressor_params params;
- unsigned (*get_matches_func)(struct xpress_compressor *,
- const struct lz_match **);
- void (*skip_bytes_func)(struct xpress_compressor *, u32 n);
- u32 len_3_too_far;
-
- /* Data currently being compressed */
- const u8 *cur_window;
- u32 cur_window_size;
-
/* Lempel-Ziv match-finder */
struct lz_mf *mf;
+ /* Optimal parsing data */
+ unsigned (*get_matches_func)(struct xpress_compressor *,
+ const struct lz_match **);
+ void (*skip_bytes_func)(struct xpress_compressor *, u32 n);
const u8 *cur_window_ptr;
-
- /* Match cache, used when doing multiple optimization passes. */
struct lz_match *cached_matches;
struct lz_match *cache_ptr;
struct lz_match *cache_limit;
-
- /* Optimal parsing data */
struct xpress_mc_pos_data *optimum;
unsigned optimum_cur_idx;
unsigned optimum_end_idx;
u8 costs[XPRESS_NUM_SYMBOLS];
- /* Lazy parsing data */
- struct lz_match prev_match;
-
/* The selected sequence of matches/literals */
struct xpress_item *chosen_items;
+ /* Data currently being compressed */
+ const u8 *cur_window;
+ u32 cur_window_size;
+
/* Symbol frequency counters */
u32 freqs[XPRESS_NUM_SYMBOLS];
return xpress_match_chooser_reverse_list(c, cur_pos);
}
-/* Lazy parsing. */
-static struct lz_match
-xpress_choose_lazy_item(struct xpress_compressor *c)
-{
- const struct lz_match *matches;
- struct lz_match cur_match;
- struct lz_match next_match;
- u32 num_matches;
-
- if (c->prev_match.len) {
- cur_match = c->prev_match;
- c->prev_match.len = 0;
- } else {
- num_matches = xpress_get_matches(c, &matches);
- if (num_matches == 0 ||
- (matches[num_matches - 1].len == 3 &&
- matches[num_matches - 1].offset >= c->len_3_too_far))
- {
- cur_match.len = 0;
- return cur_match;
- }
-
- /* With lazy parsing we only consider the longest match at each
- * position. */
- cur_match = matches[num_matches - 1];
- }
-
- if (cur_match.len >= c->params.nice_match_length) {
- xpress_skip_bytes(c, cur_match.len - 1);
- return cur_match;
- }
-
- num_matches = xpress_get_matches(c, &matches);
- if (num_matches == 0 ||
- (matches[num_matches - 1].len == 3 &&
- matches[num_matches - 1].offset >= c->len_3_too_far))
- {
- xpress_skip_bytes(c, cur_match.len - 2);
- return cur_match;
- }
-
- next_match = matches[num_matches - 1];
-
- if (next_match.len <= cur_match.len) {
- xpress_skip_bytes(c, cur_match.len - 2);
- return cur_match;
- } else {
- /* Longer match at next position. Choose a literal here so we
- * will get to use the longer match. */
- c->prev_match = next_match;
- cur_match.len = 0;
- return cur_match;
- }
-}
-
-/* Greedy parsing. */
-static struct lz_match
-xpress_choose_greedy_item(struct xpress_compressor *c)
-{
- const struct lz_match *matches;
- u32 num_matches;
-
- num_matches = xpress_get_matches(c, &matches);
- if (num_matches == 0 ||
- (matches[num_matches - 1].len == 3 &&
- matches[num_matches - 1].offset >= c->len_3_too_far))
- return (struct lz_match) {};
-
- xpress_skip_bytes(c, matches[num_matches - 1].len - 1);
- return matches[num_matches - 1];
-}
-
-/* Always choose a literal. */
-static struct lz_match
-xpress_choose_literal(struct xpress_compressor *c)
-{
- return (struct lz_match) {};
-}
-
-/*
- * Return the next match or literal to use, delegating to the currently selected
- * match-choosing algorithm.
- *
- * If the length of the returned 'struct lz_match' is less than
- * XPRESS_MIN_MATCH_LEN, then it is really a literal.
- */
-static inline struct lz_match
-xpress_choose_item(struct xpress_compressor *c)
-{
- return (*c->params.choose_item_func)(c);
-}
-
/* Set default XPRESS Huffman symbol costs to kick-start the iterative
* optimization algorithm. */
static void
costs[i] = lens[i] ? lens[i] : XPRESS_MAX_CODEWORD_LEN;
}
-/*
- * Given the data to compress (c->cur_window, c->cur_window_size), fills in
- * c->chosen_items with the intermediate representation of the match/literal
- * sequence to output. Also fills in c->codewords and c->lens to provide the
- * Huffman code with which these items should be output.
- *
- * Returns the number of items written to c->chosen_items. This can be at most
- * c->cur_window_size. (The worst case is all literals, no matches.)
- */
+/* Near-optimal parsing */
static u32
-xpress_choose_items(struct xpress_compressor *c)
+xpress_choose_items_near_optimal(struct xpress_compressor *c)
{
u32 num_passes_remaining = c->params.num_optim_passes;
const u8 *window_ptr;
struct lz_match raw_item;
struct xpress_item xpress_item;
- if (c->params.choose_item_func == xpress_choose_near_optimal_item) {
- xpress_set_default_costs(c->costs);
- c->optimum_cur_idx = 0;
- c->optimum_end_idx = 0;
- } else {
- c->prev_match.len = 0;
- if (c->cur_window_size <= 8192)
- c->len_3_too_far = 2048;
- else
- c->len_3_too_far = 4096;
- }
+ xpress_set_default_costs(c->costs);
+ c->optimum_cur_idx = 0;
+ c->optimum_end_idx = 0;
if (c->params.num_optim_passes > 1) {
c->get_matches_func = xpress_get_matches_fillcache;
lz_mf_load_window(c->mf, c->cur_window, c->cur_window_size);
while (--num_passes_remaining) {
- window_ptr = c->cur_window_ptr = c->cur_window;
+ c->cur_window_ptr = c->cur_window;
+ window_ptr = c->cur_window;
window_end = window_ptr + c->cur_window_size;
c->cache_ptr = c->cached_matches;
memset(c->freqs, 0, sizeof(c->freqs));
while (window_ptr != window_end) {
- raw_item = xpress_choose_item(c);
+ raw_item = xpress_choose_near_optimal_item(c);
if (raw_item.len >= XPRESS_MIN_MATCH_LEN) {
xpress_tally_match(raw_item.len,
raw_item.offset, c->freqs);
}
}
- window_ptr = c->cur_window_ptr = c->cur_window;
+ c->cur_window_ptr = c->cur_window;
+ window_ptr = c->cur_window;
window_end = window_ptr + c->cur_window_size;
c->cache_ptr = c->cached_matches;
memset(c->freqs, 0, sizeof(c->freqs));
u32 unseen_cost = 9;
while (window_ptr != window_end) {
- raw_item = xpress_choose_item(c);
+ raw_item = xpress_choose_near_optimal_item(c);
if (raw_item.len >= XPRESS_MIN_MATCH_LEN) {
xpress_item = xpress_tally_match(raw_item.len,
raw_item.offset,
/* When doing one-pass near-optimal parsing, rebuild the Huffman
* code occasionally. */
if (unlikely((next_chosen_item - c->chosen_items) % 2048 == 0) &&
- c->params.choose_item_func == xpress_choose_near_optimal_item &&
c->cur_window_size >= 16384 &&
c->params.num_optim_passes == 1)
{
return next_chosen_item - c->chosen_items;
}
+/* Lazy parsing */
+static u32
+xpress_choose_items_lazy(struct xpress_compressor *c)
+{
+ struct lz_mf *mf;
+ u32 len_3_too_far;
+ const u8 *window_ptr;
+ const u8 *window_end;
+ u32 num_matches;
+ struct lz_match matches[min(c->params.nice_match_length, c->params.max_search_depth)];
+ struct xpress_item *next_chosen_item;
+ struct lz_match prev_match;
+
+ mf = c->mf;
+
+ lz_mf_load_window(mf, c->cur_window, c->cur_window_size);
+
+ if (c->cur_window_size <= 8192)
+ len_3_too_far = 2048;
+ else
+ len_3_too_far = 4096;
+
+ memset(c->freqs, 0, sizeof(c->freqs));
+
+ window_ptr = c->cur_window;
+ window_end = c->cur_window + c->cur_window_size;
+ next_chosen_item = c->chosen_items;
+
+ for (;;) {
+
+ /* Don't have match at previous position */
+
+ num_matches = lz_mf_get_matches(mf, matches);
+ window_ptr++;
+
+ if (num_matches == 0 ||
+ (matches[num_matches - 1].len == 3 &&
+ matches[num_matches - 1].offset >= len_3_too_far))
+ {
+ /* No matches found => output literal */
+ *next_chosen_item++ = xpress_tally_literal(*(window_ptr - 1),
+ c->freqs);
+ if (window_ptr == window_end)
+ break;
+ continue;
+ }
+
+ prev_match = matches[num_matches - 1];
+
+ have_prev_match:
+ /* Have match at previous position */
+
+ if (prev_match.len >= c->params.nice_match_length) {
+ /* Very long match found => output immediately */
+ *next_chosen_item++ = xpress_tally_match(prev_match.len,
+ prev_match.offset,
+ c->freqs);
+ lz_mf_skip_positions(mf, prev_match.len - 1);
+ window_ptr += prev_match.len - 1;
+ if (window_ptr == window_end)
+ break;
+ continue;
+ }
+
+ num_matches = lz_mf_get_matches(mf, matches);
+ window_ptr++;
+
+ if (num_matches == 0 ||
+ (matches[num_matches - 1].len <= prev_match.len))
+ {
+ /* Next match is not longer => output previous match */
+ *next_chosen_item++ = xpress_tally_match(prev_match.len,
+ prev_match.offset,
+ c->freqs);
+ lz_mf_skip_positions(mf, prev_match.len - 2);
+ window_ptr += prev_match.len - 2;
+ if (window_ptr == window_end)
+ break;
+ continue;
+ }
+
+ /* Next match is longer => output literal */
+
+ *next_chosen_item++ = xpress_tally_literal(*(window_ptr - 2),
+ c->freqs);
+
+ prev_match = matches[num_matches - 1];
+
+ goto have_prev_match;
+ }
+
+ c->freqs[XPRESS_END_OF_DATA]++;
+ xpress_make_huffman_code(c);
+ return next_chosen_item - c->chosen_items;
+}
+
+/* Greedy parsing */
+static u32
+xpress_choose_items_greedy(struct xpress_compressor *c)
+{
+ struct lz_mf *mf;
+ u32 len_3_too_far;
+ const u8 *window_ptr;
+ const u8 *window_end;
+ struct lz_match matches[min(c->params.nice_match_length, c->params.max_search_depth)];
+ u32 num_matches;
+ struct xpress_item *next_chosen_item;
+
+ mf = c->mf;
+
+ lz_mf_load_window(mf, c->cur_window, c->cur_window_size);
+
+ if (c->cur_window_size <= 8192)
+ len_3_too_far = 2048;
+ else
+ len_3_too_far = 4096;
+
+ memset(c->freqs, 0, sizeof(c->freqs));
+
+ window_ptr = c->cur_window;
+ window_end = c->cur_window + c->cur_window_size;
+ next_chosen_item = c->chosen_items;
+
+ do {
+ /* Get longest match at the current position. */
+ num_matches = lz_mf_get_matches(mf, matches);
+
+ if (num_matches == 0 ||
+ (matches[num_matches - 1].len == 3 &&
+ matches[num_matches - 1].offset >= len_3_too_far))
+ {
+ *next_chosen_item++ = xpress_tally_literal(*window_ptr, c->freqs);
+ window_ptr += 1;
+ } else {
+ u32 len = matches[num_matches - 1].len;
+ u32 offset = matches[num_matches - 1].offset;
+
+ *next_chosen_item++ = xpress_tally_match(len, offset, c->freqs);
+ lz_mf_skip_positions(mf, len - 1);
+ window_ptr += len;
+ }
+ } while (window_ptr != window_end);
+
+ c->freqs[XPRESS_END_OF_DATA]++;
+ xpress_make_huffman_code(c);
+ return next_chosen_item - c->chosen_items;
+}
+
+/* Huffman-only parsing */
+static u32
+xpress_choose_items_huffonly(struct xpress_compressor *c)
+{
+ const u8 *window_ptr;
+ const u8 *window_end;
+ struct xpress_item *next_chosen_item;
+
+ memset(c->freqs, 0, sizeof(c->freqs));
+
+ window_ptr = c->cur_window;
+ window_end = c->cur_window + c->cur_window_size;
+ next_chosen_item = c->chosen_items;
+
+ do {
+ *next_chosen_item++ = xpress_tally_literal(*window_ptr++, c->freqs);
+ } while (window_ptr != window_end);
+
+ c->freqs[XPRESS_END_OF_DATA]++;
+ xpress_make_huffman_code(c);
+ return next_chosen_item - c->chosen_items;
+}
+
/* Given the specified compression level and maximum window size, build the
* parameters to use for XPRESS compression. */
static void
/* Huffman only (no Lempel-Ziv matches) */
xpress_params->mf_algo = LZ_MF_NULL;
- xpress_params->choose_item_func = xpress_choose_literal;
- xpress_params->num_optim_passes = 1;
+ xpress_params->choose_items_func = xpress_choose_items_huffonly;
} else if (compression_level < 30) {
/* Greedy parsing */
xpress_params->mf_algo = LZ_MF_HASH_CHAINS;
- xpress_params->choose_item_func = xpress_choose_greedy_item;
- xpress_params->num_optim_passes = 1;
+ xpress_params->choose_items_func = xpress_choose_items_greedy;
xpress_params->nice_match_length = compression_level;
xpress_params->max_search_depth = compression_level / 2;
/* Lazy parsing */
xpress_params->mf_algo = LZ_MF_HASH_CHAINS;
- xpress_params->choose_item_func = xpress_choose_lazy_item;
- xpress_params->num_optim_passes = 1;
+ xpress_params->choose_items_func = xpress_choose_items_lazy;
xpress_params->nice_match_length = compression_level;
xpress_params->max_search_depth = compression_level / 2;
} else {
/* Near-optimal parsing */
- xpress_params->choose_item_func = xpress_choose_near_optimal_item;
+ xpress_params->choose_items_func = xpress_choose_items_near_optimal;
if (max_window_size >= 32768)
xpress_params->mf_algo = LZ_MF_BINARY_TREES;
else
size += lz_mf_get_needed_memory(params.mf_algo, max_window_size);
- if (params.num_optim_passes > 1) {
- size_t cache_len = max(max_window_size * XPRESS_CACHE_PER_POS,
- params.max_search_depth + 1);
- size += cache_len * sizeof(struct lz_match);
- } else {
- size += params.max_search_depth * sizeof(struct lz_match);
- }
-
- if (params.choose_item_func == xpress_choose_near_optimal_item) {
+ if (params.choose_items_func == xpress_choose_items_near_optimal) {
size += (XPRESS_OPTIM_ARRAY_LENGTH + params.nice_match_length) *
sizeof(struct xpress_mc_pos_data);
+ if (params.num_optim_passes > 1) {
+ size_t cache_len = max(max_window_size * XPRESS_CACHE_PER_POS,
+ params.max_search_depth + 1);
+ size += cache_len * sizeof(struct lz_match);
+ } else {
+ size += params.max_search_depth * sizeof(struct lz_match);
+ }
}
size += max_window_size * sizeof(struct xpress_item);
if (!c->mf)
goto oom;
- if (params.num_optim_passes > 1) {
- size_t cache_len = max(max_window_size * XPRESS_CACHE_PER_POS,
- params.max_search_depth + 1);
- c->cached_matches = MALLOC(cache_len * sizeof(struct lz_match));
- if (!c->cached_matches)
- goto oom;
- c->cache_limit = c->cached_matches + cache_len -
- (params.max_search_depth + 1);
- } else {
- c->cached_matches = MALLOC(params.max_search_depth *
- sizeof(struct lz_match));
- if (!c->cached_matches)
- goto oom;
- }
-
- if (params.choose_item_func == xpress_choose_near_optimal_item) {
+ if (params.choose_items_func == xpress_choose_items_near_optimal) {
c->optimum = MALLOC((XPRESS_OPTIM_ARRAY_LENGTH +
params.nice_match_length) *
sizeof(struct xpress_mc_pos_data));
if (!c->optimum)
goto oom;
+ if (params.num_optim_passes > 1) {
+ size_t cache_len = max(max_window_size * XPRESS_CACHE_PER_POS,
+ params.max_search_depth + 1);
+ c->cached_matches = MALLOC(cache_len * sizeof(struct lz_match));
+ if (!c->cached_matches)
+ goto oom;
+ c->cache_limit = c->cached_matches + cache_len -
+ (params.max_search_depth + 1);
+ } else {
+ c->cached_matches = MALLOC(params.max_search_depth *
+ sizeof(struct lz_match));
+ if (!c->cached_matches)
+ goto oom;
+ }
}
c->chosen_items = MALLOC(max_window_size * sizeof(struct xpress_item));
/* Determine match/literal sequence to divide the data into. */
c->cur_window = uncompressed_data;
c->cur_window_size = uncompressed_size;
- num_chosen_items = xpress_choose_items(c);
+ num_chosen_items = (*c->params.choose_items_func)(c);
/* Output the Huffman code as a series of 512 4-bit lengths. */
cptr = compressed_data;
git://wimlib.net / wimlib / blobdiff