vendor/got/diff/2023-09-15vendor/got/diff

1 files changed, 647 insertions, 0 deletions

diff --git a/lib/diff_patience.c b/lib/diff_patience.c
new file mode 100644
index 000000000000..a06df2c36c9d
--- /dev/null
+++ b/lib/diff_patience.c
@@ -0,0 +1,647 @@
+/* Implementation of the Patience Diff algorithm invented by Bram Cohen:
+ * Divide a diff problem into smaller chunks by an LCS (Longest Common Sequence)
+ * of common-unique lines. */
+/*
+ * Copyright (c) 2020 Neels Hofmeyr <neels@hofmeyr.de>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <arraylist.h>
+#include <diff_main.h>
+
+#include "diff_internal.h"
+#include "diff_debug.h"
+
+/* Algorithm to find unique lines:
+ * 0: stupidly iterate atoms
+ * 1: qsort
+ * 2: mergesort
+ */
+#define UNIQUE_STRATEGY 1
+
+/* Per-atom state for the Patience Diff algorithm */
+struct atom_patience {
+#if UNIQUE_STRATEGY == 0
+	bool unique_here;
+#endif
+	bool unique_in_both;
+	struct diff_atom *pos_in_other;
+	struct diff_atom *prev_stack;
+	struct diff_range identical_lines;
+};
+
+/* A diff_atom has a backpointer to the root diff_data. That points to the
+ * current diff_data, a possibly smaller section of the root. That current
+ * diff_data->algo_data is a pointer to an array of struct atom_patience. The
+ * atom's index in current diff_data gives the index in the atom_patience array.
+ */
+#define PATIENCE(ATOM) \
+	(((struct atom_patience*)((ATOM)->root->current->algo_data))\
+	 [diff_atom_idx((ATOM)->root->current, ATOM)])
+
+#if UNIQUE_STRATEGY == 0
+
+/* Stupid iteration and comparison of all atoms */
+static int
+diff_atoms_mark_unique(struct diff_data *d, unsigned int *unique_count)
+{
+	struct diff_atom *i;
+	unsigned int count = 0;
+	diff_data_foreach_atom(i, d) {
+		PATIENCE(i).unique_here = true;
+		PATIENCE(i).unique_in_both = true;
+		count++;
+	}
+	diff_data_foreach_atom(i, d) {
+		struct diff_atom *j;
+
+		if (!PATIENCE(i).unique_here)
+			continue;
+
+		diff_data_foreach_atom_from(i + 1, j, d) {
+			bool same;
+			int r = diff_atom_same(&same, i, j);
+			if (r)
+				return r;
+			if (!same)
+				continue;
+			if (PATIENCE(i).unique_here) {
+				PATIENCE(i).unique_here = false;
+				PATIENCE(i).unique_in_both = false;
+				count--;
+			}
+			PATIENCE(j).unique_here = false;
+			PATIENCE(j).unique_in_both = false;
+			count--;
+		}
+	}
+	if (unique_count)
+		*unique_count = count;
+	return 0;
+}
+
+/* Mark those lines as PATIENCE(atom).unique_in_both = true that appear exactly
+ * once in each side. */
+static int
+diff_atoms_mark_unique_in_both(struct diff_data *left, struct diff_data *right,
+			       unsigned int *unique_in_both_count)
+{
+	/* Derive the final unique_in_both count without needing an explicit
+	 * iteration. So this is just some optimiziation to save one iteration
+	 * in the end. */
+	unsigned int unique_in_both;
+	int r;
+
+	r = diff_atoms_mark_unique(left, &unique_in_both);
+	if (r)
+		return r;
+	r = diff_atoms_mark_unique(right, NULL);
+	if (r)
+		return r;
+
+	debug("unique_in_both %u\n", unique_in_both);
+
+	struct diff_atom *i;
+	diff_data_foreach_atom(i, left) {
+		if (!PATIENCE(i).unique_here)
+			continue;
+		struct diff_atom *j;
+		int found_in_b = 0;
+		diff_data_foreach_atom(j, right) {
+			bool same;
+			int r = diff_atom_same(&same, i, j);
+			if (r)
+				return r;
+			if (!same)
+				continue;
+			if (!PATIENCE(j).unique_here) {
+				found_in_b = 2; /* or more */
+				break;
+			} else {
+				found_in_b = 1;
+				PATIENCE(j).pos_in_other = i;
+				PATIENCE(i).pos_in_other = j;
+			}
+		}
+
+		if (found_in_b == 0 || found_in_b > 1) {
+			PATIENCE(i).unique_in_both = false;
+			unique_in_both--;
+			debug("unique_in_both %u  (%d) ", unique_in_both,
+			      found_in_b);
+			debug_dump_atom(left, NULL, i);
+		}
+	}
+
+	/* Still need to unmark right[*]->patience.unique_in_both for atoms that
+	 * don't exist in left */
+	diff_data_foreach_atom(i, right) {
+		if (!PATIENCE(i).unique_here
+		    || !PATIENCE(i).unique_in_both)
+			continue;
+		struct diff_atom *j;
+		bool found_in_a = false;
+		diff_data_foreach_atom(j, left) {
+			bool same;
+			int r;
+			if (!PATIENCE(j).unique_in_both)
+				continue;
+			r = diff_atom_same(&same, i, j);
+			if (r)
+				return r;
+			if (!same)
+				continue;
+			found_in_a = true;
+			break;
+		}
+
+		if (!found_in_a)
+			PATIENCE(i).unique_in_both = false;
+	}
+
+	if (unique_in_both_count)
+		*unique_in_both_count = unique_in_both;
+	return 0;
+}
+
+#else /* UNIQUE_STRATEGY != 0 */
+
+/* Use an optimized sorting algorithm (qsort, mergesort) to find unique lines */
+
+static int diff_atoms_compar(const void *_a, const void *_b)
+{
+	const struct diff_atom *a = *(struct diff_atom**)_a;
+	const struct diff_atom *b = *(struct diff_atom**)_b;
+	int cmp;
+	int rc = 0;
+
+	/* If there's been an error (e.g. I/O error) in a previous compar, we
+	 * have no way to abort the sort but just report the rc and stop
+	 * comparing. Make sure to catch errors on either side. If atoms are
+	 * from more than one diff_data, make sure the error, if any, spreads
+	 * to all of them, so we can cut short all future comparisons. */
+	if (a->root->err)
+		rc = a->root->err;
+	if (b->root->err)
+		rc = b->root->err;
+	if (rc) {
+		a->root->err = rc;
+		b->root->err = rc;
+		/* just return 'equal' to not swap more positions */
+		return 0;
+	}
+
+	/* Sort by the simplistic hash */
+	if (a->hash < b->hash)
+		return -1;
+	if (a->hash > b->hash)
+		return 1;
+
+	/* If hashes are the same, the lines may still differ. Do a full cmp. */
+	rc = diff_atom_cmp(&cmp, a, b);
+
+	if (rc) {
+		/* Mark the I/O error so that the caller can find out about it.
+		 * For the case atoms are from more than one diff_data, mark in
+		 * both. */
+		a->root->err = rc;
+		if (a->root != b->root)
+			b->root->err = rc;
+		return 0;
+	}
+
+	return cmp;
+}
+
+/* Sort an array of struct diff_atom* in-place. */
+static int diff_atoms_sort(struct diff_atom *atoms[],
+			   size_t atoms_count)
+{
+#if UNIQUE_STRATEGY == 1
+	qsort(atoms, atoms_count, sizeof(struct diff_atom*), diff_atoms_compar);
+#else
+	mergesort(atoms, atoms_count, sizeof(struct diff_atom*),
+		  diff_atoms_compar);
+#endif
+	return atoms[0]->root->err;
+}
+
+static int
+diff_atoms_mark_unique_in_both(struct diff_data *left, struct diff_data *right,
+			       unsigned int *unique_in_both_count_p)
+{
+	struct diff_atom *a;
+	struct diff_atom *b;
+	struct diff_atom **all_atoms;
+	unsigned int len = 0;
+	unsigned int i;
+	unsigned int unique_in_both_count = 0;
+	int rc;
+
+	all_atoms = calloc(left->atoms.len + right->atoms.len,
+	    sizeof(struct diff_atom *));
+	if (all_atoms == NULL)
+		return ENOMEM;
+
+	left->err = 0;
+	right->err = 0;
+	left->root->err = 0;
+	right->root->err = 0;
+	diff_data_foreach_atom(a, left) {
+		all_atoms[len++] = a;
+	}
+	diff_data_foreach_atom(b, right) {
+		all_atoms[len++] = b;
+	}
+
+	rc = diff_atoms_sort(all_atoms, len);
+	if (rc)
+		goto free_and_exit;
+
+	/* Now we have a sorted array of atom pointers. All similar lines are
+	 * adjacent. Walk through the array and mark those that are unique on
+	 * each side, but exist once in both sources. */
+	for (i = 0; i < len; i++) {
+		bool same;
+		unsigned int next_differing_i;
+		unsigned int last_identical_i;
+		unsigned int j;
+		unsigned int count_first_side = 1;
+		unsigned int count_other_side = 0;
+		a = all_atoms[i];
+		debug("a: ");
+		debug_dump_atom(a->root, NULL, a);
+
+		/* Do as few diff_atom_cmp() as possible: first walk forward
+		 * only using the cheap hash as indicator for differing atoms;
+		 * then walk backwards until hitting an identical atom. */
+		for (next_differing_i = i + 1; next_differing_i < len;
+		     next_differing_i++) {
+			b = all_atoms[next_differing_i];
+			if (a->hash != b->hash)
+				break;
+		}
+		for (last_identical_i = next_differing_i - 1;
+		     last_identical_i > i;
+		     last_identical_i--) {
+			b = all_atoms[last_identical_i];
+			rc = diff_atom_same(&same, a, b);
+			if (rc)
+				goto free_and_exit;
+			if (same)
+				break;
+		}
+		next_differing_i = last_identical_i + 1;
+
+		for (j = i+1; j < next_differing_i; j++) {
+			b = all_atoms[j];
+			/* A following atom is the same. See on which side the
+			 * repetition counts. */
+			if (a->root == b->root)
+				count_first_side ++;
+			else
+				count_other_side ++;
+			debug("b: ");
+			debug_dump_atom(b->root, NULL, b);
+			debug("   count_first_side=%d count_other_side=%d\n",
+			      count_first_side, count_other_side);
+		}
+
+		/* Counted a section of similar atoms, put the results back to
+		 * the atoms. */
+		if ((count_first_side == 1)
+		    && (count_other_side == 1)) {
+			b = all_atoms[i+1];
+			PATIENCE(a).unique_in_both = true;
+			PATIENCE(a).pos_in_other = b;
+			PATIENCE(b).unique_in_both = true;
+			PATIENCE(b).pos_in_other = a;
+			unique_in_both_count++;
+		}
+
+		/* j now points at the first atom after 'a' that is not
+		 * identical to 'a'. j is always > i. */
+		i = j - 1;
+	}
+	*unique_in_both_count_p = unique_in_both_count;
+	rc = 0;
+free_and_exit:
+	free(all_atoms);
+	return rc;
+}
+#endif /* UNIQUE_STRATEGY != 0 */
+
+/* binary search to find the stack to put this atom "card" on. */
+static int
+find_target_stack(struct diff_atom *atom,
+		  struct diff_atom **patience_stacks,
+		  unsigned int patience_stacks_count)
+{
+	unsigned int lo = 0;
+	unsigned int hi = patience_stacks_count;
+	while (lo < hi) {
+		unsigned int mid = (lo + hi) >> 1;
+
+		if (PATIENCE(patience_stacks[mid]).pos_in_other
+		    < PATIENCE(atom).pos_in_other)
+			lo = mid + 1;
+		else
+			hi = mid;
+	}
+	return lo;
+}
+
+/* Among the lines that appear exactly once in each side, find the longest
+ * streak that appear in both files in the same order (with other stuff allowed
+ * to interleave). Use patience sort for that, as in the Patience Diff
+ * algorithm.
+ * See https://bramcohen.livejournal.com/73318.html and, for a much more
+ * detailed explanation,
+ * https://blog.jcoglan.com/2017/09/19/the-patience-diff-algorithm/ */
+int
+diff_algo_patience(const struct diff_algo_config *algo_config,
+		   struct diff_state *state)
+{
+	int rc;
+	struct diff_data *left = &state->left;
+	struct diff_data *right = &state->right;
+	struct atom_patience *atom_patience_left =
+		calloc(left->atoms.len, sizeof(struct atom_patience));
+	struct atom_patience *atom_patience_right =
+		calloc(right->atoms.len, sizeof(struct atom_patience));
+	unsigned int unique_in_both_count;
+	struct diff_atom **lcs = NULL;
+
+	debug("\n** %s\n", __func__);
+
+	left->root->current = left;
+	right->root->current = right;
+	left->algo_data = atom_patience_left;
+	right->algo_data = atom_patience_right;
+
+	/* Find those lines that appear exactly once in 'left' and exactly once
+	 * in 'right'. */
+	rc = diff_atoms_mark_unique_in_both(left, right, &unique_in_both_count);
+	if (rc)
+		goto free_and_exit;
+
+	debug("unique_in_both_count %u\n", unique_in_both_count);
+	debug("left:\n");
+	debug_dump(left);
+	debug("right:\n");
+	debug_dump(right);
+
+	if (!unique_in_both_count) {
+		/* Cannot apply Patience, tell the caller to use fallback_algo
+		 * instead. */
+		rc = DIFF_RC_USE_DIFF_ALGO_FALLBACK;
+		goto free_and_exit;
+	}
+
+	rc = ENOMEM;
+
+	/* An array of Longest Common Sequence is the result of the below
+	 * subscope: */
+	unsigned int lcs_count = 0;
+	struct diff_atom *lcs_tail = NULL;
+
+	{
+		/* This subscope marks the lifetime of the atom_pointers
+		 * allocation */
+
+		/* One chunk of storage for atom pointers */
+		struct diff_atom **atom_pointers;
+		atom_pointers = recallocarray(NULL, 0, unique_in_both_count * 2,
+					      sizeof(struct diff_atom*));
+		if (atom_pointers == NULL)
+			return ENOMEM;
+		/* Half for the list of atoms that still need to be put on
+		 * stacks */
+		struct diff_atom **uniques = atom_pointers;
+
+		/* Half for the patience sort state's "card stacks" -- we
+		 * remember only each stack's topmost "card" */
+		struct diff_atom **patience_stacks;
+		patience_stacks = atom_pointers + unique_in_both_count;
+		unsigned int patience_stacks_count = 0;
+
+		/* Take all common, unique items from 'left' ... */
+
+		struct diff_atom *atom;
+		struct diff_atom **uniques_end = uniques;
+		diff_data_foreach_atom(atom, left) {
+			if (!PATIENCE(atom).unique_in_both)
+				continue;
+			*uniques_end = atom;
+			uniques_end++;
+		}
+
+		/* ...and sort them to the order found in 'right'.
+		 * The idea is to find the leftmost stack that has a higher line
+		 * number and add it to the stack's top.
+		 * If there is no such stack, open a new one on the right. The
+		 * line number is derived from the atom*, which are array items
+		 * and hence reflect the relative position in the source file.
+		 * So we got the common-uniques from 'left' and sort them
+		 * according to PATIENCE(atom).pos_in_other. */
+		unsigned int i;
+		for (i = 0; i < unique_in_both_count; i++) {
+			atom = uniques[i];
+			unsigned int target_stack;
+			target_stack = find_target_stack(atom, patience_stacks,
+							 patience_stacks_count);
+			assert(target_stack <= patience_stacks_count);
+			patience_stacks[target_stack] = atom;
+			if (target_stack == patience_stacks_count)
+				patience_stacks_count++;
+
+			/* Record a back reference to the next stack on the
+			 * left, which will form the final longest sequence
+			 * later. */
+			PATIENCE(atom).prev_stack = target_stack ?
+				patience_stacks[target_stack - 1] : NULL;
+
+			{
+				int xx;
+				for (xx = 0; xx < patience_stacks_count; xx++) {
+					debug(" %s%d",
+					      (xx == target_stack) ? ">" : "",
+					      diff_atom_idx(right,
+							    PATIENCE(patience_stacks[xx]).pos_in_other));
+				}
+				debug("\n");
+			}
+		}
+
+		/* backtrace through prev_stack references to form the final
+		 * longest common sequence */
+		lcs_tail = patience_stacks[patience_stacks_count - 1];
+		lcs_count = patience_stacks_count;
+
+		/* uniques and patience_stacks are no longer needed.
+		 * Backpointers are in PATIENCE(atom).prev_stack */
+		free(atom_pointers);
+	}
+
+	lcs = recallocarray(NULL, 0, lcs_count, sizeof(struct diff_atom*));
+	struct diff_atom **lcs_backtrace_pos = &lcs[lcs_count - 1];
+	struct diff_atom *atom;
+	for (atom = lcs_tail; atom; atom = PATIENCE(atom).prev_stack, lcs_backtrace_pos--) {
+		assert(lcs_backtrace_pos >= lcs);
+		*lcs_backtrace_pos = atom;
+	}
+
+	unsigned int i;
+	if (DEBUG) {
+		debug("\npatience LCS:\n");
+		for (i = 0; i < lcs_count; i++) {
+			debug("\n L "); debug_dump_atom(left, right, lcs[i]);
+			debug(" R "); debug_dump_atom(right, left,
+						      PATIENCE(lcs[i]).pos_in_other);
+		}
+	}
+
+
+	/* TODO: For each common-unique line found (now listed in lcs), swallow
+	 * lines upwards and downwards that are identical on each side. Requires
+	 * a way to represent atoms being glued to adjacent atoms. */
+
+	debug("\ntraverse LCS, possibly recursing:\n");
+
+	/* Now we have pinned positions in both files at which it makes sense to
+	 * divide the diff problem into smaller chunks. Go into the next round:
+	 * look at each section in turn, trying to again find common-unique
+	 * lines in those smaller sections. As soon as no more are found, the
+	 * remaining smaller sections are solved by Myers. */
+	/* left_pos and right_pos are indexes in left/right->atoms.head until
+	 * which the atoms are already handled (added to result chunks). */
+	unsigned int left_pos = 0;
+	unsigned int right_pos = 0;
+	for (i = 0; i <= lcs_count; i++) {
+		struct diff_atom *atom;
+		struct diff_atom *atom_r;
+		/* left_idx and right_idx are indexes of the start of this
+		 * section of identical lines on both sides.
+		 * left_pos marks the index of the first still unhandled line,
+		 * left_idx is the start of an identical section some way
+		 * further down, and this loop adds an unsolved chunk of
+		 * [left_pos..left_idx[ and a solved chunk of
+		 * [left_idx..identical_lines.end[. */
+		unsigned int left_idx;
+		unsigned int right_idx;
+
+		debug("iteration %u of %u  left_pos %u  right_pos %u\n",
+		      i, lcs_count, left_pos, right_pos);
+
+		if (i < lcs_count) {
+			atom = lcs[i];
+			atom_r = PATIENCE(atom).pos_in_other;
+			debug("lcs[%u] = left[%u] = right[%u]\n", i,
+			      diff_atom_idx(left, atom), diff_atom_idx(right, atom_r));
+			left_idx = diff_atom_idx(left, atom);
+			right_idx = diff_atom_idx(right, atom_r);
+		} else {
+			/* There are no more identical lines until the end of
+			 * left and right. */
+			atom = NULL;
+			atom_r = NULL;
+			left_idx = left->atoms.len;
+			right_idx = right->atoms.len;
+		}
+
+		/* 'atom' (if not NULL) now marks an atom that matches on both
+		 * sides according to patience-diff (a common-unique identical
+		 * atom in both files).
+		 * Handle the section before and the atom itself; the section
+		 * after will be handled by the next loop iteration -- note that
+		 * i loops to last element + 1 ("i <= lcs_count"), so that there
+		 * will be another final iteration to pick up the last remaining
+		 * items after the last LCS atom.
+		 */
+
+		debug("iteration %u  left_pos %u  left_idx %u"
+		      "  right_pos %u  right_idx %u\n",
+		      i, left_pos, left_idx, right_pos, right_idx);
+
+		/* Section before the matching atom */
+		struct diff_atom *left_atom = &left->atoms.head[left_pos];
+		unsigned int left_section_len = left_idx - left_pos;
+
+		struct diff_atom *right_atom = &(right->atoms.head[right_pos]);
+		unsigned int right_section_len = right_idx - right_pos;
+
+		if (left_section_len && right_section_len) {
+			/* Record an unsolved chunk, the caller will apply
+			 * inner_algo() on this chunk. */
+			if (!diff_state_add_chunk(state, false,
+						  left_atom, left_section_len,
+						  right_atom,
+						  right_section_len))
+				goto free_and_exit;
+		} else if (left_section_len && !right_section_len) {
+			/* Only left atoms and none on the right, they form a
+			 * "minus" chunk, then. */
+			if (!diff_state_add_chunk(state, true,
+						  left_atom, left_section_len,
+						  right_atom, 0))
+				goto free_and_exit;
+		} else if (!left_section_len && right_section_len) {
+			/* No left atoms, only atoms on the right, they form a
+			 * "plus" chunk, then. */
+			if (!diff_state_add_chunk(state, true,
+						  left_atom, 0,
+						  right_atom, right_section_len))
+				goto free_and_exit;
+		}
+		/* else: left_section_len == 0 and right_section_len == 0, i.e.
+		 * nothing here. */
+
+		/* The atom found to match on both sides forms a chunk of equals
+		 * on each side. In the very last iteration of this loop, there
+		 * is no matching atom, we were just cleaning out the remaining
+		 * lines. */
+		if (atom) {
+			void *ok;
+			ok = diff_state_add_chunk(state, true,
+						  atom, 1,
+						  PATIENCE(atom).pos_in_other, 1);
+			if (!ok)
+				goto free_and_exit;
+		}
+		left_pos = left_idx + 1;
+		right_pos = right_idx + 1;
+		debug("end of iteration %u  left_pos %u  left_idx %u"
+		      "  right_pos %u  right_idx %u\n",
+		      i, left_pos, left_idx, right_pos, right_idx);
+	}
+	debug("** END %s\n", __func__);
+
+	rc = DIFF_RC_OK;
+
+free_and_exit:
+	left->root->current = NULL;
+	right->root->current = NULL;
+	free(atom_patience_left);
+	free(atom_patience_right);
+	if (lcs)
+		free(lcs);
+	return rc;
+}