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+/* vi:set ts=8 sts=4 sw=4 noet:
+ *
+ * MNV - MNV is not Vim by Bram Moolenaar
+ *
+ * Do ":help uganda" in MNV to read copying and usage conditions.
+ * Do ":help credits" in MNV to see a list of people who contributed.
+ * See README.txt for an overview of the MNV source code.
+ */
+
+#include "mnv.h"
+
+#define LN_MAX_BUFS 8
+#define LN_DECISION_MAX 255 // pow(2, LN_MAX_BUFS(8)) - 1 = 255
+
+// struct for running the diff linematch algorithm
+typedef struct diffcmppath_S diffcmppath_T;
+struct diffcmppath_S
+{
+ // to keep track of the total score of this path
+ int df_lev_score;
+ size_t df_path_n; // current index of this path
+ int df_choice_mem[LN_DECISION_MAX + 1];
+ int df_choice[LN_DECISION_MAX];
+ // to keep track of this path traveled
+ diffcmppath_T *df_decision[LN_DECISION_MAX];
+ size_t df_optimal_choice;
+};
+
+static int matching_chars(const mmfile_t *m1, const mmfile_t *m2);
+static size_t unwrap_indexes(const int *values, const int *diff_len, const size_t ndiffs);
+static size_t test_charmatch_paths(diffcmppath_T *node, int lastdecision);
+
+ static size_t
+line_len(const mmfile_t *m)
+{
+ char *s = m->ptr;
+ char *end;
+
+ end = memchr(s, '\n', (size_t)m->size);
+ return end ? (size_t)(end - s) : (size_t)m->size;
+}
+
+#define MATCH_CHAR_MAX_LEN 800
+
+/// Same as matching_chars but ignore whitespace
+///
+/// @param s1
+/// @param s2
+ static int
+matching_chars_iwhite(const mmfile_t *s1, const mmfile_t *s2)
+{
+ // the newly processed strings that will be compared
+ // delete the white space characters
+ mmfile_t sp[2];
+ char p[2][MATCH_CHAR_MAX_LEN];
+
+ for (int k = 0; k < 2; k++)
+ {
+ const mmfile_t *s = k == 0 ? s1 : s2;
+ size_t pi = 0;
+ size_t slen = MIN(MATCH_CHAR_MAX_LEN - 1, line_len(s));
+
+ for (size_t i = 0; i <= slen; i++)
+ {
+ char e = s->ptr[i];
+
+ if (e != ' ' && e != '\t')
+ {
+ p[k][pi] = e;
+ pi++;
+ }
+ }
+
+ sp[k].ptr = p[k];
+ sp[k].size = (int)pi;
+ }
+
+ return matching_chars(&sp[0], &sp[1]);
+}
+
+/// Return matching characters between "s1" and "s2" whilst respecting sequence
+/// order.
+/// Consider the case of two strings 'AAACCC' and 'CCCAAA', the
+/// return value from this function will be 3, either to match
+/// the 3 C's, or the 3 A's.
+///
+/// Examples:
+/// matching_chars("aabc", "acba") -> 2 // 'a' and 'b' in common
+/// matching_chars("123hello567", "he123ll567o") -> 8 // '123', 'll' and '567' in common
+/// matching_chars("abcdefg", "gfedcba") -> 1 // all characters in common,
+/// // but only at most 1 in sequence
+///
+/// @param m1
+/// @param m2
+ static int
+matching_chars(const mmfile_t *m1, const mmfile_t *m2)
+{
+ size_t s1len = MIN(MATCH_CHAR_MAX_LEN - 1, line_len(m1));
+ size_t s2len = MIN(MATCH_CHAR_MAX_LEN - 1, line_len(m2));
+ char *s1 = m1->ptr;
+ char *s2 = m2->ptr;
+ int matrix[2][MATCH_CHAR_MAX_LEN] = { 0 };
+ int icur = 1; // save space by storing only two rows for i axis
+
+ for (size_t i = 0; i < s1len; i++)
+ {
+ icur = (icur == 1 ? 0 : 1);
+ int *e1 = matrix[icur];
+ int *e2 = matrix[!icur];
+
+ for (size_t j = 0; j < s2len; j++)
+ {
+ // skip char in s1
+ if (e2[j + 1] > e1[j + 1])
+ e1[j + 1] = e2[j + 1];
+ // skip char in s2
+ if (e1[j] > e1[j + 1])
+ e1[j + 1] = e1[j];
+ // compare char in s1 and s2
+ if ((s1[i] == s2[j]) && (e2[j] + 1) > e1[j + 1])
+ e1[j + 1] = e2[j] + 1;
+ }
+ }
+
+ return matrix[icur][s2len];
+}
+
+/// count the matching characters between a variable number of strings "sp"
+/// mark the strings that have already been compared to extract them later
+/// without re-running the character match counting.
+/// @param sp
+/// @param fomvals
+/// @param n
+ static int
+count_n_matched_chars(mmfile_t **sp, const size_t n, int iwhite)
+{
+ int matched_chars = 0;
+ int matched = 0;
+
+ for (size_t i = 0; i < n; i++)
+ {
+ for (size_t j = i + 1; j < n; j++)
+ {
+ if (sp[i]->ptr != NULL && sp[j]->ptr != NULL)
+ {
+ matched++;
+ // TODO(lewis6991): handle whitespace ignoring higher up in the
+ // stack
+ matched_chars += iwhite ? matching_chars_iwhite(sp[i], sp[j])
+ : matching_chars(sp[i], sp[j]);
+ }
+ }
+ }
+
+ // prioritize a match of 3 (or more lines) equally to a match of 2 lines
+ if (matched >= 2)
+ {
+ matched_chars *= 2;
+ matched_chars /= matched;
+ }
+
+ return matched_chars;
+}
+
+ static mmfile_t
+fastforward_buf_to_lnum(mmfile_t s, linenr_T lnum)
+{
+ for (int i = 0; i < lnum - 1; i++)
+ {
+ char *line_end;
+
+ line_end = memchr(s.ptr, '\n', (size_t)s.size);
+ s.size = line_end ? (int)(s.size - (line_end - s.ptr)) : 0;
+ s.ptr = line_end;
+ if (!s.ptr)
+ break;
+ s.ptr++;
+ s.size--;
+ }
+
+ return s;
+}
+
+/// try all the different ways to compare these lines and use the one that
+/// results in the most matching characters
+/// @param df_iters
+/// @param paths
+/// @param npaths
+/// @param path_idx
+/// @param choice
+/// @param diffcmppath
+/// @param diff_len
+/// @param ndiffs
+/// @param diff_blk
+ static void
+try_possible_paths(
+ const int *df_iters,
+ const size_t *paths,
+ const int npaths,
+ const int path_idx,
+ int *choice,
+ diffcmppath_T *diffcmppath,
+ const int *diff_len,
+ const size_t ndiffs,
+ const mmfile_t **diff_blk,
+ int iwhite)
+{
+ if (path_idx == npaths)
+ {
+ if ((*choice) > 0)
+ {
+ int from_vals[LN_MAX_BUFS] = { 0 };
+ const int *to_vals = df_iters;
+
+ mmfile_t mm[LN_MAX_BUFS]; // stack memory for current_lines
+ mmfile_t *current_lines[LN_MAX_BUFS];
+ for (size_t k = 0; k < ndiffs; k++)
+ {
+ from_vals[k] = df_iters[k];
+ // get the index at all of the places
+ if ((*choice) & (1 << k))
+ {
+ from_vals[k]--;
+ mm[k] = fastforward_buf_to_lnum(*diff_blk[k], df_iters[k]);
+ }
+ else
+ CLEAR_FIELD(mm[k]);
+ current_lines[k] = &mm[k];
+ }
+ size_t unwrapped_idx_from = unwrap_indexes(from_vals, diff_len, ndiffs);
+ size_t unwrapped_idx_to = unwrap_indexes(to_vals, diff_len, ndiffs);
+ int matched_chars = count_n_matched_chars(current_lines, ndiffs, iwhite);
+ int score = diffcmppath[unwrapped_idx_from].df_lev_score + matched_chars;
+
+ if (score > diffcmppath[unwrapped_idx_to].df_lev_score)
+ {
+ diffcmppath[unwrapped_idx_to].df_path_n = 1;
+ diffcmppath[unwrapped_idx_to].df_decision[0] =
+ &diffcmppath[unwrapped_idx_from];
+ diffcmppath[unwrapped_idx_to].df_choice[0] = *choice;
+ diffcmppath[unwrapped_idx_to].df_lev_score = score;
+ }
+ else if (score == diffcmppath[unwrapped_idx_to].df_lev_score)
+ {
+ size_t k = diffcmppath[unwrapped_idx_to].df_path_n++;
+ diffcmppath[unwrapped_idx_to].df_decision[k] =
+ &diffcmppath[unwrapped_idx_from];
+ diffcmppath[unwrapped_idx_to].df_choice[k] = *choice;
+ }
+ }
+ return;
+ }
+
+ size_t bit_place = paths[path_idx];
+ *(choice) |= (1 << bit_place); // set it to 1
+ try_possible_paths(df_iters, paths, npaths, path_idx + 1, choice,
+ diffcmppath, diff_len, ndiffs, diff_blk, iwhite);
+ *(choice) &= ~(1 << bit_place); // set it to 0
+ try_possible_paths(df_iters, paths, npaths, path_idx + 1, choice,
+ diffcmppath, diff_len, ndiffs, diff_blk, iwhite);
+}
+
+/// unwrap indexes to access n dimensional tensor
+/// @param values
+/// @param diff_len
+/// @param ndiffs
+ static size_t
+unwrap_indexes(const int *values, const int *diff_len, const size_t ndiffs)
+{
+ size_t num_unwrap_scalar = 1;
+
+ for (size_t k = 0; k < ndiffs; k++)
+ num_unwrap_scalar *= (size_t)diff_len[k] + 1;
+
+ size_t path_idx = 0;
+ for (size_t k = 0; k < ndiffs; k++)
+ {
+ num_unwrap_scalar /= (size_t)diff_len[k] + 1;
+
+ int n = values[k];
+ path_idx += num_unwrap_scalar * (size_t)n;
+ }
+
+ return path_idx;
+}
+
+/// populate the values of the linematch algorithm tensor, and find the best
+/// decision for how to compare the relevant lines from each of the buffers at
+/// each point in the tensor
+/// @param df_iters
+/// @param ch_dim
+/// @param diffcmppath
+/// @param diff_len
+/// @param ndiffs
+/// @param diff_blk
+ static void
+populate_tensor(
+ int *df_iters,
+ const size_t ch_dim,
+ diffcmppath_T *diffcmppath,
+ const int *diff_len,
+ const size_t ndiffs,
+ const mmfile_t **diff_blk,
+ int iwhite)
+{
+ if (ch_dim == ndiffs)
+ {
+ int npaths = 0;
+ size_t paths[LN_MAX_BUFS];
+
+ for (size_t j = 0; j < ndiffs; j++)
+ {
+ if (df_iters[j] > 0)
+ {
+ paths[npaths] = j;
+ npaths++;
+ }
+ }
+
+ int choice = 0;
+ size_t unwrapper_idx_to = unwrap_indexes(df_iters, diff_len, ndiffs);
+
+ diffcmppath[unwrapper_idx_to].df_lev_score = -1;
+ try_possible_paths(df_iters, paths, npaths, 0, &choice, diffcmppath,
+ diff_len, ndiffs, diff_blk, iwhite);
+ return;
+ }
+
+ for (int i = 0; i <= diff_len[ch_dim]; i++)
+ {
+ df_iters[ch_dim] = i;
+ populate_tensor(df_iters, ch_dim + 1, diffcmppath, diff_len,
+ ndiffs, diff_blk, iwhite);
+ }
+}
+
+/// algorithm to find an optimal alignment of lines of a diff block with 2 or
+/// more files. The algorithm is generalized to work for any number of files
+/// which corresponds to another dimension added to the tensor used in the
+/// algorithm
+///
+/// for questions and information about the linematch algorithm please contact
+/// Jonathon White (jonathonwhite@protonmail.com)
+///
+/// for explanation, a summary of the algorithm in 3 dimensions (3 files
+/// compared) follows
+///
+/// The 3d case (for 3 buffers) of the algorithm implemented when diffopt
+/// 'linematch' is enabled. The algorithm constructs a 3d tensor to
+/// compare a diff between 3 buffers. The dimensions of the tensor are
+/// the length of the diff in each buffer plus 1 A path is constructed by
+/// moving from one edge of the cube/3d tensor to the opposite edge.
+/// Motions from one cell of the cube to the next represent decisions. In
+/// a 3d cube, there are a total of 7 decisions that can be made,
+/// represented by the enum df_path3_choice which is defined in
+/// buffer_defs.h a comparison of buffer 0 and 1 represents a motion
+/// toward the opposite edge of the cube with components along the 0 and
+/// 1 axes. a comparison of buffer 0, 1, and 2 represents a motion
+/// toward the opposite edge of the cube with components along the 0, 1,
+/// and 2 axes. A skip of buffer 0 represents a motion along only the 0
+/// axis. For each action, a point value is awarded, and the path is
+/// saved for reference later, if it is found to have been the optimal
+/// path. The optimal path has the highest score. The score is
+/// calculated as the summation of the total characters matching between
+/// all of the lines which were compared. The structure of the algorithm
+/// is that of a dynamic programming problem. We can calculate a point
+/// i,j,k in the cube as a function of i-1, j-1, and k-1. To find the
+/// score and path at point i,j,k, we must determine which path we want
+/// to use, this is done by looking at the possibilities and choosing
+/// the one which results in the local highest score. The total highest
+/// scored path is, then in the end represented by the cell in the
+/// opposite corner from the start location. The entire algorithm
+/// consists of populating the 3d cube with the optimal paths from which
+/// it may have came.
+///
+/// Optimizations:
+/// As the function to calculate the cell of a tensor at point i,j,k is a
+/// function of the cells at i-1, j-1, k-1, the whole tensor doesn't need
+/// to be stored in memory at once. In the case of the 3d cube, only two
+/// slices (along k and j axis) are stored in memory. For the 2d matrix
+/// (for 2 files), only two rows are stored at a time. The next/previous
+/// slice (or row) is always calculated from the other, and they alternate
+/// at each iteration.
+/// In the 3d case, 3 arrays are populated to memorize the score (matched
+/// characters) of the 3 buffers, so a redundant calculation of the
+/// scores does not occur
+/// @param diff_blk
+/// @param diff_len
+/// @param ndiffs
+/// @param [out] [allocated] decisions
+/// @return the length of decisions
+ size_t
+linematch_nbuffers(
+ const mmfile_t **diff_blk,
+ const int *diff_len,
+ const size_t ndiffs,
+ int **decisions,
+ int iwhite)
+{
+ assert(ndiffs <= LN_MAX_BUFS);
+
+ size_t memsize = 1;
+ size_t memsize_decisions = 0;
+ for (size_t i = 0; i < ndiffs; i++)
+ {
+ assert(diff_len[i] >= 0);
+ memsize *= (size_t)(diff_len[i] + 1);
+ memsize_decisions += (size_t)diff_len[i];
+ }
+
+ // create the flattened path matrix
+ diffcmppath_T *diffcmppath = lalloc(sizeof(diffcmppath_T) * memsize, TRUE);
+ if (diffcmppath == NULL)
+ return 0;
+
+ // allocate memory here
+ size_t n = (size_t)pow(2.0, (double)ndiffs);
+ for (size_t i = 0; i < memsize; i++)
+ {
+ diffcmppath[i].df_lev_score = 0;
+ diffcmppath[i].df_path_n = 0;
+ for (size_t j = 0; j < n; j++)
+ diffcmppath[i].df_choice_mem[j] = -1;
+ }
+
+ // memory for avoiding repetitive calculations of score
+ int df_iters[LN_MAX_BUFS];
+ populate_tensor(df_iters, 0, diffcmppath, diff_len, ndiffs, diff_blk,
+ iwhite);
+
+ const size_t u = unwrap_indexes(diff_len, diff_len, ndiffs);
+ diffcmppath_T *startNode = &diffcmppath[u];
+
+ *decisions = lalloc(sizeof(int) * memsize_decisions, TRUE);
+ if (*decisions == NULL)
+ {
+ mnv_free(diffcmppath);
+ return 0;
+ }
+
+ size_t n_optimal = 0;
+ test_charmatch_paths(startNode, 0);
+ while (startNode->df_path_n > 0)
+ {
+ size_t j = startNode->df_optimal_choice;
+ (*decisions)[n_optimal++] = startNode->df_choice[j];
+ startNode = startNode->df_decision[j];
+ }
+ // reverse array
+ for (size_t i = 0; i < (n_optimal / 2); i++)
+ {
+ int tmp = (*decisions)[i];
+ (*decisions)[i] = (*decisions)[n_optimal - 1 - i];
+ (*decisions)[n_optimal - 1 - i] = tmp;
+ }
+
+ mnv_free(diffcmppath);
+
+ return n_optimal;
+}
+
+// returns the minimum amount of path changes from start to end
+ static size_t
+test_charmatch_paths(diffcmppath_T *node, int lastdecision)
+{
+ // memoization
+ if (node->df_choice_mem[lastdecision] == -1)
+ {
+ if (node->df_path_n == 0)
+ // we have reached the end of the tree
+ node->df_choice_mem[lastdecision] = 0;
+ else
+ {
+ // the minimum amount of turns required to reach the end
+ size_t minimum_turns = SIZE_MAX;
+ for (size_t i = 0; i < node->df_path_n; i++)
+ {
+ // recurse
+ size_t t = test_charmatch_paths(node->df_decision[i],
+ node->df_choice[i]) +
+ (lastdecision != node->df_choice[i] ? 1 : 0);
+ if (t < minimum_turns)
+ {
+ node->df_optimal_choice = i;
+ minimum_turns = t;
+ }
+ }
+ node->df_choice_mem[lastdecision] = (int)minimum_turns;
+ }
+ }
+
+ return (size_t)node->df_choice_mem[lastdecision];
+}
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