+++ /dev/null
-/*
- * lz_mf.c
- *
- * Interface for Lempel-Ziv match-finders.
- *
- * Copyright (c) 2014 Eric Biggers. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE
- * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
- * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
- * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
- * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#ifdef HAVE_CONFIG_H
-# include "config.h"
-#endif
-
-#include "wimlib/lz_mf.h"
-#include "wimlib/lz_mf_ops.h"
-#include "wimlib/util.h"
-
-/* Available match-finding algorithms. */
-static const struct lz_mf_ops *mf_ops[] = {
- [LZ_MF_LCP_INTERVAL_TREE] = &lz_lcp_interval_tree_ops,
- [LZ_MF_LINKED_SUFFIX_ARRAY] = &lz_linked_suffix_array_ops,
-};
-
-static const struct lz_mf_ops *
-get_mf_ops(enum lz_mf_algo algorithm)
-{
- if ((unsigned int)algorithm >= ARRAY_LEN(mf_ops))
- return NULL;
- return mf_ops[(unsigned int)algorithm];
-}
-
-/*
- * Returns an upper bound on the number of bytes of memory that will be consumed
- * by a match-finder allocated with the specified algorithm and maximum window
- * size.
- *
- * The returned value does not include the size of the window itself. The
- * caller must account for this separately if needed.
- *
- * If @algorithm is invalid, returns 0.
- */
-u64
-lz_mf_get_needed_memory(enum lz_mf_algo algorithm, u32 max_window_size)
-{
- const struct lz_mf_ops *ops;
-
- ops = get_mf_ops(algorithm);
- if (!ops)
- return 0;
- return ops->struct_size + ops->get_needed_memory(max_window_size);
-}
-/*
- * Returns %true if and only if the specified parameters can be validly used to
- * create a match-finder using lz_mf_alloc().
- */
-bool
-lz_mf_params_valid(const struct lz_mf_params *params)
-{
- const struct lz_mf_ops *ops;
-
- /* Require that a valid algorithm be specified. */
- ops = get_mf_ops(params->algorithm);
- if (!ops)
- return false;
-
- /* Don't allow empty windows. Otherwise, some match-finding algorithms
- * might need special-case code to handle empty windows. */
- if (params->max_window_size == 0)
- return false;
-
- /* Don't allow length-1 matches, so that match-finding algorithms don't
- * need to worry about this case. Most LZ-based compression formats
- * don't allow length-1 matches, since they usually aren't helpful for
- * compression. Also, if a compressor really does need length-1
- * matches, it can easily maintain its own table of length 256
- * containing the most-recently-seen position for each byte value.
- *
- * min_match_len == 0 is valid, since that means the match-finding
- * algorithm will fill in a default value. */
- if (params->min_match_len == 1)
- return false;
-
- if (params->max_match_len != 0) {
-
- /* Don't allow length-1 matches (same reason as above). */
- if (params->max_match_len == 1)
- return false;
-
- /* Don't allow the maximum match length to be shorter than the
- * minimum match length. */
- if (params->max_match_len < params->min_match_len)
- return false;
- }
-
- /* Don't allow the needed memory size to overflow a 'size_t'. */
- if (sizeof(size_t) < sizeof(u64)) {
- u64 needed_mem = ops->get_needed_memory(params->max_window_size);
- if ((size_t)needed_mem != needed_mem)
- return false;
- }
-
- /* Call the algorithm-specific routine to finish the validation. */
- return ops->params_valid(params);
-}
-
-/*
- * Allocate a new match-finder.
- *
- * @params
- * The parameters for the match-finder. See the declaration of 'struct
- * lz_mf_params' for more information.
- *
- * Returns a pointer to the new match-finder, or NULL if out of memory or the
- * parameters are invalid. Call lz_mf_params_valid() beforehand to test the
- * parameter validity separately.
- */
-struct lz_mf *
-lz_mf_alloc(const struct lz_mf_params *params)
-{
- struct lz_mf *mf;
- const struct lz_mf_ops *ops;
-
- /* Validate the parameters. */
- if (!lz_mf_params_valid(params))
- return NULL;
-
- /* Get the match-finder operations structure. Since we just validated
- * the parameters, this is guaranteed to return a valid structure. */
- ops = get_mf_ops(params->algorithm);
- LZ_ASSERT(ops != NULL);
-
- /* Allocate memory for the match-finder structure. */
- LZ_ASSERT(ops->struct_size >= sizeof(struct lz_mf));
- mf = CALLOC(1, ops->struct_size);
- if (!mf)
- return NULL;
-
- /* Set the parameters and operations fields. */
- mf->params = *params;
- mf->ops = *ops;
-
- /* Perform algorithm-specific initialization. Normally this is where
- * most of the necessary memory is allocated. */
- if (!mf->ops.init(mf)) {
- FREE(mf);
- return NULL;
- }
-
- /* The algorithm must have set min_match_len and max_match_len if either
- * was 0. */
- LZ_ASSERT(mf->params.min_match_len >= 2);
- LZ_ASSERT(mf->params.max_match_len >= mf->params.min_match_len);
-
- return mf;
-}
-
-/*
- * Load a window into the match-finder.
- *
- * @mf
- * The match-finder into which to load the window.
- * @window
- * Pointer to the window to load. This memory must remain available,
- * unmodified, while the match-finder is being used.
- * @size
- * The size of the window, in bytes. This can't be larger than the
- * @max_window_size parameter. In addition, this can't be 0.
- *
- * Note: this interface does not support sliding windows!
- */
-void
-lz_mf_load_window(struct lz_mf *mf, const u8 *window, u32 size)
-{
- /* Can't be an empty window, and can't be larger than the maximum window
- * size with which the match-finder was allocated. */
- LZ_ASSERT(size > 0);
- LZ_ASSERT(size <= mf->params.max_window_size);
-
- /* Save the window and initialize the current position. */
- mf->cur_window = window;
- mf->cur_window_size = size;
- mf->cur_window_pos = 0;
-
- /* Call into the algorithm-specific window load code. */
- mf->ops.load_window(mf, window, size);
-}
-
-/*
- * Retrieve a list of matches at the next position in the window.
- *
- * @mf
- * The match-finder into which a window has been loaded using
- * lz_mf_load_window().
- * @matches
- * The array into which the matches will be returned. The returned match
- * count will not exceed the minimum of @max_search_depth and (@len_limit -
- * @min_match_len + 1), where @len_limit is itself defined as
- * min(@max_match_len, @nice_match_len).
- *
- * The return value is the number of matches that were found and stored in the
- * 'matches' array. The matches will be ordered by strictly increasing length
- * and strictly increasing offset. No match shall have length less than
- * @min_match_len, and no match shall have length greater than @max_match_len.
- * The return value may be 0, which indicates that no matches were found.
- *
- * On completion, the match-finder is advanced to the next position in the
- * window.
- *
- * Note: in-non-debug mode, the inline definition of this gets used instead.
- * They are the same, except that the non-inline version below validates the
- * results to help debug match-finding algorithms.
- */
-#ifdef ENABLE_LZ_DEBUG
-u32
-lz_mf_get_matches(struct lz_mf *mf, struct lz_match *matches)
-{
- LZ_ASSERT(mf->cur_window_pos < mf->cur_window_size);
-
- const u32 orig_pos = mf->cur_window_pos;
- const u32 len_limit = min(mf->params.max_match_len,
- lz_mf_get_bytes_remaining(mf));
- const u8 * const strptr = lz_mf_get_window_ptr(mf);
-
- const u32 num_matches = mf->ops.get_matches(mf, matches);
-
- LZ_ASSERT(mf->cur_window_pos == orig_pos + 1);
-
-#if 0
- fprintf(stderr, "Pos %"PRIu32"/%"PRIu32": %"PRIu32" matches\n",
- orig_pos, mf->cur_window_size, num_matches);
- for (u32 i = 0; i < num_matches; i++) {
- fprintf(stderr, "\tLen %"PRIu32" Offset %"PRIu32"\n",
- matches[i].len, matches[i].offset);
- }
-#endif
-
- /* Validate the matches. */
- for (u32 i = 0; i < num_matches; i++) {
- const u32 len = matches[i].len;
- const u32 offset = matches[i].offset;
- const u8 *matchptr;
-
- /* Length valid? */
- LZ_ASSERT(len >= mf->params.min_match_len);
- LZ_ASSERT(len <= len_limit);
-
- /* Offset valid? */
- LZ_ASSERT(offset >= 1);
- LZ_ASSERT(offset <= orig_pos);
-
- /* Lengths and offsets strictly increasing? */
- if (i > 0) {
- LZ_ASSERT(len > matches[i - 1].len);
- LZ_ASSERT(offset > matches[i - 1].offset);
- }
-
- /* Actually a match? */
- matchptr = strptr - offset;
- LZ_ASSERT(!memcmp(strptr, matchptr, len));
-
- /* Match can't be extended further? */
- LZ_ASSERT(len == len_limit || strptr[len] != matchptr[len]);
- }
-
- return num_matches;
-}
-#endif /* ENABLE_LZ_DEBUG */
-
-/*
- * Skip 'n' positions in the match-finder. This is a faster alternative to
- * calling lz_mf_get_matches() at each position to advance the match-finder.
- *
- * 'n' must be greater than 0.
- *
- * Note: in-non-debug mode, the inline definition of this gets used instead.
- * They are the same, except the non-inline version below does extra checks.
- */
-#ifdef ENABLE_LZ_DEBUG
-void
-lz_mf_skip_positions(struct lz_mf *mf, const u32 n)
-{
- LZ_ASSERT(n > 0);
- LZ_ASSERT(n <= lz_mf_get_bytes_remaining(mf));
-
- const u32 orig_pos = mf->cur_window_pos;
-
- mf->ops.skip_positions(mf, n);
-
- LZ_ASSERT(mf->cur_window_pos == orig_pos + n);
-}
-#endif
-
-/*
- * Free the match-finder.
- *
- * This frees all memory that was allocated by the call to lz_mf_alloc().
- */
-void
-lz_mf_free(struct lz_mf *mf)
-{
- if (mf) {
- mf->ops.destroy(mf);
- #ifdef ENABLE_LZ_DEBUG
- memset(mf, 0, mf->ops.struct_size);
- #endif
- FREE(mf);
- }
-}
git://wimlib.net / wimlib / blobdiff