git-apply: bad patch fragments are fatal
[git/git.git] / apply.c
CommitLineData
c1bb9350
LT
1/*
2 * apply.c
3 *
4 * Copyright (C) Linus Torvalds, 2005
5 *
6 * This applies patches on top of some (arbitrary) version of the SCM.
7 *
8 * NOTE! It does all its work in the index file, and only cares about
9 * the files in the working directory if you tell it to "merge" the
10 * patch apply.
11 *
12 * Even when merging it always takes the source from the index, and
13 * uses the working tree as a "branch" for a 3-way merge.
14 */
15#include <ctype.h>
16
17#include "cache.h"
18
19// We default to the merge behaviour, since that's what most people would
20// expect
21static int merge_patch = 1;
22static const char apply_usage[] = "git-apply <patch>";
23
24#define CHUNKSIZE (8192)
25
26static void *read_patch_file(int fd, unsigned long *sizep)
27{
28 unsigned long size = 0, alloc = CHUNKSIZE;
29 void *buffer = xmalloc(alloc);
30
31 for (;;) {
32 int nr = alloc - size;
33 if (nr < 1024) {
34 alloc += CHUNKSIZE;
35 buffer = xrealloc(buffer, alloc);
36 nr = alloc - size;
37 }
38 nr = read(fd, buffer + size, nr);
39 if (!nr)
40 break;
41 if (nr < 0) {
42 if (errno == EAGAIN)
43 continue;
44 die("git-apply: read returned %s", strerror(errno));
45 }
46 size += nr;
47 }
48 *sizep = size;
49 return buffer;
50}
51
52static unsigned long linelen(char *buffer, unsigned long size)
53{
54 unsigned long len = 0;
55 while (size--) {
56 len++;
57 if (*buffer++ == '\n')
58 break;
59 }
60 return len;
61}
62
63static int match_word(const char *line, const char *match)
64{
65 for (;;) {
66 char c = *match++;
67 if (!c)
68 break;
69 if (*line++ != c)
70 return 0;
71 }
72 return *line == ' ';
73}
74
75/* Verify that we recognize the lines following a git header */
76static int parse_git_header(char *line, unsigned int size)
77{
78 unsigned long offset, len;
79
80 for (offset = 0 ; size > 0 ; offset += len, size -= len, line += len) {
81 len = linelen(line, size);
82 if (!len)
83 break;
84 if (line[len-1] != '\n')
85 return -1;
86 if (len < 4)
87 break;
88 if (!memcmp(line, "@@ -", 4))
89 return offset;
90 if (match_word(line, "new file mode"))
91 continue;
92 if (match_word(line, "deleted file mode"))
93 continue;
94 if (match_word(line, "copy"))
95 continue;
96 if (match_word(line, "rename"))
97 continue;
98 if (match_word(line, "similarity index"))
99 continue;
100 break;
101 }
102
103 /* We want either a patch _or_ something real */
104 return offset ? :-1;
105}
106
107static int find_header(char *line, unsigned long size, int *hdrsize)
108{
109 unsigned long offset, len;
110
111 for (offset = 0; size > 0; offset += len, size -= len, line += len) {
112 unsigned long nextlen;
113
114 len = linelen(line, size);
115 if (!len)
116 break;
117
118 /* Testing this early allows us to take a few shortcuts.. */
119 if (len < 6)
120 continue;
121 if (size < len + 6)
122 break;
123
124 /*
125 * Git patch? It might not have a real patch, just a rename
126 * or mode change, so we handle that specially
127 */
128 if (!memcmp("diff --git ", line, 11)) {
129 int git_hdr_len = parse_git_header(line + len, size - len);
130 if (git_hdr_len < 0)
131 continue;
132
133 *hdrsize = len + git_hdr_len;
134 return offset;
135 }
136
137 /** --- followed by +++ ? */
138 if (memcmp("--- ", line, 4) || memcmp("+++ ", line + len, 4))
139 continue;
140
141 /*
142 * We only accept unified patches, so we want it to
143 * at least have "@@ -a,b +c,d @@\n", which is 14 chars
144 * minimum
145 */
146 nextlen = linelen(line + len, size - len);
147 if (size < nextlen + 14 || memcmp("@@ -", line + len + nextlen, 4))
148 continue;
149
150 /* Ok, we'll consider it a patch */
151 *hdrsize = len + nextlen;
152 return offset;
153 }
154 return -1;
155}
156
157static int parse_num(const char *line, int len, int offset, const char *expect, unsigned long *p)
158{
159 char *ptr;
160 int digits, ex;
161
162 if (offset < 0 || offset >= len)
163 return -1;
164 line += offset;
165 len -= offset;
166
167 if (!isdigit(*line))
168 return -1;
169 *p = strtoul(line, &ptr, 10);
170
171 digits = ptr - line;
172
173 offset += digits;
174 line += digits;
175 len -= digits;
176
177 ex = strlen(expect);
178 if (ex > len)
179 return -1;
180 if (memcmp(line, expect, ex))
181 return -1;
182
183 return offset + ex;
184}
185
186/*
187 * Parse a unified diff. Note that this really needs
188 * to parse each fragment separately, since the only
189 * way to know the difference between a "---" that is
190 * part of a patch, and a "---" that starts the next
191 * patch is to look at the line counts..
192 */
193static int apply_fragment(char *line, unsigned long size)
194{
195 int len = linelen(line, size), offset;
196 unsigned long oldpos, oldlines, newpos, newlines;
197
198 if (!len || line[len-1] != '\n')
199 return -1;
200
201 /* Figure out the number of lines in a fragment */
202 offset = parse_num(line, len, 4, ",", &oldpos);
203 offset = parse_num(line, len, offset, " +", &oldlines);
204 offset = parse_num(line, len, offset, ",", &newpos);
205 offset = parse_num(line, len, offset, " @@", &newlines);
206 if (offset < 0)
207 return -1;
208
209 /* Parse the thing.. */
210 line += len;
211 size -= len;
212 for (offset = len; size > 0; offset += len, size -= len, line += len) {
213 if (!oldlines && !newlines)
214 break;
215 len = linelen(line, size);
216 if (!len || line[len-1] != '\n')
217 return -1;
218 switch (*line) {
219 default:
220 return -1;
221 case ' ':
222 oldlines--;
223 newlines--;
224 break;
225 case '-':
226 oldlines--;
227 break;
228 case '+':
229 newlines--;
230 break;
231 }
232 }
233 return offset;
234}
235
236static int apply_single_patch(char *line, unsigned long size)
237{
238 unsigned long offset = 0;
239
240 while (size > 4 && !memcmp(line, "@@ -", 4)) {
241 int len = apply_fragment(line, size);
242 if (len <= 0)
5e224a2e 243 die("corrupt patch");
c1bb9350
LT
244
245printf("applying fragment:\n%.*s\n\n", len, line);
246
247 offset += len;
248 line += len;
249 size -= len;
250 }
251 return offset;
252}
253
254static int apply_chunk(char *buffer, unsigned long size)
255{
256 int hdrsize, patchsize;
257 int offset = find_header(buffer, size, &hdrsize);
258 char *header, *patch;
259
260 if (offset < 0)
261 return offset;
262 header = buffer + offset;
263
264printf("Found header:\n%.*s\n\n", hdrsize, header);
265
266 patch = header + hdrsize;
267 patchsize = apply_single_patch(patch, size - offset - hdrsize);
268
269 return offset + hdrsize + patchsize;
270}
271
272static int apply_patch(int fd)
273{
274 unsigned long offset, size;
275 char *buffer = read_patch_file(fd, &size);
276
277 if (!buffer)
278 return -1;
279 offset = 0;
280 while (size > 0) {
281 int nr = apply_chunk(buffer + offset, size);
282 if (nr < 0)
283 break;
284 offset += nr;
285 size -= nr;
286 }
287 free(buffer);
288 return 0;
289}
290
291int main(int argc, char **argv)
292{
293 int i;
294
295 if (read_cache() < 0)
296 die("unable to read index file");
297
298 for (i = 1; i < argc; i++) {
299 const char *arg = argv[i];
300 int fd;
301
302 if (!strcmp(arg, "-")) {
303 apply_patch(0);
304 continue;
305 }
306 if (!strcmp(arg, "--no-merge")) {
307 merge_patch = 0;
308 continue;
309 }
310 fd = open(arg, O_RDONLY);
311 if (fd < 0)
312 usage(apply_usage);
313 apply_patch(fd);
314 close(fd);
315 }
316 return 0;
317}