1 /* Produce a unidiff output from a diff_result. */
2 /*
3  * Copyright (c) 2020 Neels Hofmeyr <neels@hofmeyr.de>
4  *
5  * Permission to use, copy, modify, and distribute this software for any
6  * purpose with or without fee is hereby granted, provided that the above
7  * copyright notice and this permission notice appear in all copies.
8  *
9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16  */
17 
18 #include <errno.h>
19 #include <inttypes.h>
20 #include <stdbool.h>
21 #include <stdio.h>
22 #include <stdlib.h>
23 
24 #include <diff/arraylist.h>
25 #include <diff/diff_main.h>
26 #include <diff/diff_output.h>
27 
28 #include "diff_debug.h"
29 #include "diff_internal.h"
30 
31 static bool
32 chunk_context_empty(const struct diff_chunk_context *cc)
33 {
34 	return diff_range_empty(&cc->chunk);
35 }
36 
37 void
38 diff_chunk_context_get(struct diff_chunk_context *cc, const struct diff_result *r,
39 		  int chunk_idx, int context_lines)
40 {
41 	const struct diff_chunk *c = &r->chunks.head[chunk_idx];
42 	int left_start = diff_atom_root_idx(&r->left, c->left_start);
43 	int left_end = MIN(r->left.atoms.len,
44 			   left_start + c->left_count + context_lines);
45 	int right_start = diff_atom_root_idx(&r->right, c->right_start);
46 	int right_end = MIN(r->right.atoms.len,
47 			    right_start + c->right_count + context_lines);
48 
49 	left_start = MAX(0, left_start - context_lines);
50 	right_start = MAX(0, right_start - context_lines);
51 
52 	*cc = (struct diff_chunk_context){
53 		.chunk = {
54 			.start = chunk_idx,
55 			.end = chunk_idx + 1,
56 		},
57 		.left = {
58 			.start = left_start,
59 			.end = left_end,
60 		},
61 		.right = {
62 			.start = right_start,
63 			.end = right_end,
64 		},
65 	};
66 }
67 
68 static bool
69 chunk_contexts_touch(const struct diff_chunk_context *cc,
70 		     const struct diff_chunk_context *other)
71 {
72 	return diff_ranges_touch(&cc->chunk, &other->chunk)
73 		|| diff_ranges_touch(&cc->left, &other->left)
74 		|| diff_ranges_touch(&cc->right, &other->right);
75 }
76 
77 static void
78 chunk_contexts_merge(struct diff_chunk_context *cc,
79 		     const struct diff_chunk_context *other)
80 {
81 	diff_ranges_merge(&cc->chunk, &other->chunk);
82 	diff_ranges_merge(&cc->left, &other->left);
83 	diff_ranges_merge(&cc->right, &other->right);
84 }
85 
86 struct diff_output_unidiff_state {
87 	bool header_printed;
88 };
89 
90 struct diff_output_unidiff_state *
91 diff_output_unidiff_state_alloc(void)
92 {
93 	struct diff_output_unidiff_state *state;
94 
95 	state = calloc(1, sizeof(struct diff_output_unidiff_state));
96 	if (state != NULL)
97 		diff_output_unidiff_state_reset(state);
98 	return state;
99 }
100 
101 void
102 diff_output_unidiff_state_reset(struct diff_output_unidiff_state *state)
103 {
104 	state->header_printed = false;
105 }
106 
107 void
108 diff_output_unidiff_state_free(struct diff_output_unidiff_state *state)
109 {
110 	free(state);
111 }
112 
113 static int
114 output_unidiff_chunk(struct diff_output_info *outinfo, FILE *dest,
115 		     struct diff_output_unidiff_state *state,
116 		     const struct diff_input_info *info,
117 		     const struct diff_result *result,
118 		     const struct diff_chunk_context *cc)
119 {
120 	int rc;
121 	off_t outoff = 0, outlen = 0, *offp;
122 
123 	if (diff_range_empty(&cc->left) && diff_range_empty(&cc->right))
124 		return DIFF_RC_OK;
125 
126 	if (outinfo && outinfo->line_offsets.len > 0) {
127 		unsigned int idx = outinfo->line_offsets.len - 1;
128 		outoff = outinfo->line_offsets.head[idx];
129 	}
130 
131 	if (!(state->header_printed)) {
132 		rc = fprintf(dest, "--- %s\n", info->left_path ? : "a");
133 		if (rc < 0)
134 			return errno;
135 		if (outinfo) {
136 			ARRAYLIST_ADD(offp, outinfo->line_offsets);
137 			outoff += rc;
138 			*offp = outoff;
139 
140 		}
141 		rc = fprintf(dest, "+++ %s\n", info->right_path ? : "b");
142 		if (rc < 0)
143 			return errno;
144 		if (outinfo) {
145 			ARRAYLIST_ADD(offp, outinfo->line_offsets);
146 			outoff += rc;
147 			*offp = outoff;
148 
149 		}
150 		state->header_printed = true;
151 	}
152 
153 	rc = fprintf(dest, "@@ -%d,%d +%d,%d @@\n",
154 		cc->left.start + 1, cc->left.end - cc->left.start,
155 		cc->right.start + 1, cc->right.end - cc->right.start);
156 	if (rc < 0)
157 		return errno;
158 	if (outinfo) {
159 		ARRAYLIST_ADD(offp, outinfo->line_offsets);
160 		outoff += rc;
161 		*offp = outoff;
162 
163 	}
164 
165 	/* Got the absolute line numbers where to start printing, and the index
166 	 * of the interesting (non-context) chunk.
167 	 * To print context lines above the interesting chunk, nipping on the
168 	 * previous chunk index may be necessary.
169 	 * It is guaranteed to be only context lines where left == right, so it
170 	 * suffices to look on the left. */
171 	const struct diff_chunk *first_chunk;
172 	int chunk_start_line;
173 	first_chunk = &result->chunks.head[cc->chunk.start];
174 	chunk_start_line = diff_atom_root_idx(&result->left,
175 					      first_chunk->left_start);
176 	if (cc->left.start < chunk_start_line) {
177 		rc = diff_output_lines(outinfo, dest, " ",
178 				  &result->left.atoms.head[cc->left.start],
179 				  chunk_start_line - cc->left.start);
180 		if (rc)
181 			return rc;
182 	}
183 
184 	/* Now write out all the joined chunks and contexts between them */
185 	int c_idx;
186 	for (c_idx = cc->chunk.start; c_idx < cc->chunk.end; c_idx++) {
187 		const struct diff_chunk *c = &result->chunks.head[c_idx];
188 
189 		if (c->left_count && c->right_count)
190 			rc = diff_output_lines(outinfo, dest,
191 					  c->solved ? " " : "?",
192 					  c->left_start, c->left_count);
193 		else if (c->left_count && !c->right_count)
194 			rc = diff_output_lines(outinfo, dest,
195 					  c->solved ? "-" : "?",
196 					  c->left_start, c->left_count);
197 		else if (c->right_count && !c->left_count)
198 			rc = diff_output_lines(outinfo, dest,
199 					  c->solved ? "+" : "?",
200 					  c->right_start, c->right_count);
201 		if (rc)
202 			return rc;
203 	}
204 
205 	/* Trailing context? */
206 	const struct diff_chunk *last_chunk;
207 	int chunk_end_line;
208 	last_chunk = &result->chunks.head[cc->chunk.end - 1];
209 	chunk_end_line = diff_atom_root_idx(&result->left,
210 					    last_chunk->left_start
211 					    + last_chunk->left_count);
212 	if (cc->left.end > chunk_end_line) {
213 		rc = diff_output_lines(outinfo, dest, " ",
214 				  &result->left.atoms.head[chunk_end_line],
215 				  cc->left.end - chunk_end_line);
216 		if (rc)
217 			return rc;
218 	}
219 
220 	return DIFF_RC_OK;
221 }
222 
223 int
224 diff_output_unidiff_chunk(struct diff_output_info **output_info, FILE *dest,
225 			  struct diff_output_unidiff_state *state,
226 			  const struct diff_input_info *info,
227 			  const struct diff_result *result,
228 			  const struct diff_chunk_context *cc)
229 {
230 	struct diff_output_info *outinfo = NULL;
231 
232 	if (output_info) {
233 		*output_info = diff_output_info_alloc();
234 		if (*output_info == NULL)
235 			return ENOMEM;
236 		outinfo = *output_info;
237 	}
238 
239 	return output_unidiff_chunk(outinfo, dest, state, info,
240 	    result, cc);
241 }
242 
243 int
244 diff_output_unidiff(struct diff_output_info **output_info,
245 		    FILE *dest, const struct diff_input_info *info,
246 		    const struct diff_result *result,
247 		    unsigned int context_lines)
248 {
249 	struct diff_output_unidiff_state *state;
250 	struct diff_chunk_context cc = {};
251 	struct diff_output_info *outinfo = NULL;
252 	int i;
253 
254 	if (!result)
255 		return EINVAL;
256 	if (result->rc != DIFF_RC_OK)
257 		return result->rc;
258 
259 	if (output_info) {
260 		*output_info = diff_output_info_alloc();
261 		if (*output_info == NULL)
262 			return ENOMEM;
263 		outinfo = *output_info;
264 	}
265 
266 	state = diff_output_unidiff_state_alloc();
267 	if (state == NULL) {
268 		if (output_info) {
269 			diff_output_info_free(*output_info);
270 			*output_info = NULL;
271 		}
272 		return ENOMEM;
273 	}
274 
275 
276 	for (i = 0; i < result->chunks.len; i++) {
277 		struct diff_chunk *c = &result->chunks.head[i];
278 		enum diff_chunk_type t = diff_chunk_type(c);
279 		struct diff_chunk_context next;
280 
281 		if (t != CHUNK_MINUS && t != CHUNK_PLUS)
282 			continue;
283 
284 		if (chunk_context_empty(&cc)) {
285 			/* These are the first lines being printed.
286 			 * Note down the start point, any number of subsequent
287 			 * chunks may be joined up to this unidiff chunk by
288 			 * context lines or by being directly adjacent. */
289 			diff_chunk_context_get(&cc, result, i, context_lines);
290 			debug("new chunk to be printed:"
291 			      " chunk %d-%d left %d-%d right %d-%d\n",
292 			      cc.chunk.start, cc.chunk.end,
293 			      cc.left.start, cc.left.end,
294 			      cc.right.start, cc.right.end);
295 			continue;
296 		}
297 
298 		/* There already is a previous chunk noted down for being
299 		 * printed. Does it join up with this one? */
300 		diff_chunk_context_get(&next, result, i, context_lines);
301 		debug("new chunk to be printed:"
302 		      " chunk %d-%d left %d-%d right %d-%d\n",
303 		      next.chunk.start, next.chunk.end,
304 		      next.left.start, next.left.end,
305 		      next.right.start, next.right.end);
306 
307 		if (chunk_contexts_touch(&cc, &next)) {
308 			/* This next context touches or overlaps the previous
309 			 * one, join. */
310 			chunk_contexts_merge(&cc, &next);
311 			debug("new chunk to be printed touches previous chunk,"
312 			      " now: left %d-%d right %d-%d\n",
313 			      cc.left.start, cc.left.end,
314 			      cc.right.start, cc.right.end);
315 			continue;
316 		}
317 
318 		/* No touching, so the previous context is complete with a gap
319 		 * between it and this next one. Print the previous one and
320 		 * start fresh here. */
321 		debug("new chunk to be printed does not touch previous chunk;"
322 		      " print left %d-%d right %d-%d\n",
323 		      cc.left.start, cc.left.end, cc.right.start, cc.right.end);
324 		output_unidiff_chunk(outinfo, dest, state, info, result, &cc);
325 		cc = next;
326 		debug("new unprinted chunk is left %d-%d right %d-%d\n",
327 		      cc.left.start, cc.left.end, cc.right.start, cc.right.end);
328 	}
329 
330 	if (!chunk_context_empty(&cc))
331 		output_unidiff_chunk(outinfo, dest, state, info, result, &cc);
332 	diff_output_unidiff_state_free(state);
333 	return DIFF_RC_OK;
334 }