1 /** @file
2 * @brief Glass changesets
3 */
4 /* Copyright 2014,2016,2020 Olly Betts
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License as
8 * published by the Free Software Foundation; either version 2 of the
9 * License, or (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
19 * USA
20 */
21
22 #include <config.h>
23
24 #include "glass_changes.h"
25
26 #include "glass_replicate_internal.h"
27 #include "fd.h"
28 #include "io_utils.h"
29 #include "pack.h"
30 #include "posixy_wrapper.h"
31 #include "str.h"
32 #include "stringutils.h"
33 #include "wordaccess.h"
34 #include "xapian/constants.h"
35 #include "xapian/error.h"
36
37 #include <cerrno>
38 #include <cstdlib>
39 #include <string>
40
41 using namespace std;
42
~GlassChanges()43 GlassChanges::~GlassChanges()
44 {
45 if (changes_fd >= 0) {
46 ::close(changes_fd);
47 string changes_tmp = changes_stem;
48 changes_tmp += "tmp";
49 io_unlink(changes_tmp);
50 }
51 }
52
53 GlassChanges *
start(glass_revision_number_t old_rev,glass_revision_number_t rev,int flags)54 GlassChanges::start(glass_revision_number_t old_rev,
55 glass_revision_number_t rev,
56 int flags)
57 {
58 if (rev == 0) {
59 // Don't generate a changeset for the first revision.
60 return NULL;
61 }
62
63 // Always check max_changesets for modification since last revision.
64 const char *p = getenv("XAPIAN_MAX_CHANGESETS");
65 if (p) {
66 max_changesets = atoi(p);
67 } else {
68 max_changesets = 0;
69 }
70
71 if (max_changesets == 0)
72 return NULL;
73
74 string changes_tmp = changes_stem;
75 changes_tmp += "tmp";
76 changes_fd = posixy_open(changes_tmp.c_str(),
77 O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0666);
78 if (changes_fd < 0) {
79 string message = "Couldn't open changeset ";
80 message += changes_tmp;
81 message += " to write";
82 throw Xapian::DatabaseError(message, errno);
83 }
84
85 // Write header for changeset file.
86 string header = CHANGES_MAGIC_STRING;
87 header += char(CHANGES_VERSION);
88 pack_uint(header, old_rev);
89 pack_uint(header, rev);
90
91 if (flags & Xapian::DB_DANGEROUS) {
92 header += '\x01'; // Changes can't be applied to a live database.
93 } else {
94 header += '\x00'; // Changes can be applied to a live database.
95 }
96
97 io_write(changes_fd, header.data(), header.size());
98 // FIXME: save the block stream as a single zlib stream...
99
100 // bool compressed = CHANGES_VERSION != 1; FIXME: always true for glass, but make optional?
101 return this;
102 }
103
104 void
write_block(const char * p,size_t len)105 GlassChanges::write_block(const char * p, size_t len)
106 {
107 io_write(changes_fd, p, len);
108 }
109
110 void
commit(glass_revision_number_t new_rev,int flags)111 GlassChanges::commit(glass_revision_number_t new_rev, int flags)
112 {
113 if (changes_fd < 0)
114 return;
115
116 io_write(changes_fd, "\xff", 1);
117
118 string changes_tmp = changes_stem;
119 changes_tmp += "tmp";
120
121 if (!(flags & Xapian::DB_NO_SYNC) && !io_sync(changes_fd)) {
122 int saved_errno = errno;
123 (void)::close(changes_fd);
124 changes_fd = -1;
125 (void)unlink(changes_tmp.c_str());
126 string m = changes_tmp;
127 m += ": Failed to sync";
128 throw Xapian::DatabaseError(m, saved_errno);
129 }
130
131 (void)::close(changes_fd);
132 changes_fd = -1;
133
134 string changes_file = changes_stem;
135 changes_file += str(new_rev - 1); // FIXME: ?
136
137 if (!io_tmp_rename(changes_tmp, changes_file)) {
138 string m = changes_tmp;
139 m += ": Failed to rename to ";
140 m += changes_file;
141 throw Xapian::DatabaseError(m, errno);
142 }
143
144 if (new_rev <= max_changesets) {
145 // We can't yet have max_changesets old changesets.
146 return;
147 }
148
149 // Only remove old changesets if we successfully wrote a new changeset.
150 // Start at the oldest changeset we know about, and stop at max_changesets
151 // before new_rev. If max_changesets is unchanged from the previous
152 // commit and nothing went wrong, exactly one changeset file should be
153 // deleted.
154 glass_revision_number_t stop_changeset = new_rev - max_changesets;
155 while (oldest_changeset < stop_changeset) {
156 changes_file.resize(changes_stem.size());
157 changes_file += str(oldest_changeset);
158 (void)io_unlink(changes_file);
159 ++oldest_changeset;
160 }
161 }
162
163 void
check(const string & changes_file)164 GlassChanges::check(const string & changes_file)
165 {
166 FD fd(posixy_open(changes_file.c_str(), O_RDONLY | O_CLOEXEC, 0666));
167 if (fd < 0) {
168 string message = "Couldn't open changeset ";
169 message += changes_file;
170 throw Xapian::DatabaseError(message, errno);
171 }
172
173 char buf[10240];
174
175 size_t n = io_read(fd, buf, sizeof(buf), CONST_STRLEN(CHANGES_MAGIC_STRING) + 4);
176 if (memcmp(buf, CHANGES_MAGIC_STRING,
177 CONST_STRLEN(CHANGES_MAGIC_STRING)) != 0) {
178 throw Xapian::DatabaseError("Changes file has wrong magic");
179 }
180
181 const char * p = buf + CONST_STRLEN(CHANGES_MAGIC_STRING);
182 if (*p++ != CHANGES_VERSION) {
183 throw Xapian::DatabaseError("Changes file has unknown version");
184 }
185 const char * end = buf + n;
186
187 glass_revision_number_t old_rev, rev;
188 if (!unpack_uint(&p, end, &old_rev))
189 throw Xapian::DatabaseError("Changes file has bad old_rev");
190 if (!unpack_uint(&p, end, &rev))
191 throw Xapian::DatabaseError("Changes file has bad rev");
192 if (rev <= old_rev)
193 throw Xapian::DatabaseError("Changes file has rev <= old_rev");
194 if (p == end || (*p != 0 && *p != 1))
195 throw Xapian::DatabaseError("Changes file has bad dangerous flag");
196 ++p;
197
198 while (true) {
199 n -= (p - buf);
200 memmove(buf, p, n);
201 n += io_read(fd, buf + n, sizeof(buf) - n);
202
203 if (n == 0)
204 throw Xapian::DatabaseError("Changes file truncated");
205
206 p = buf;
207 end = buf + n;
208
209 unsigned char v = *p++;
210 if (v == 0xff) {
211 if (p != end)
212 throw Xapian::DatabaseError("Changes file - junk at end");
213 break;
214 }
215 if (v == 0xfe) {
216 // Version file.
217 glass_revision_number_t version_rev;
218 if (!unpack_uint(&p, end, &version_rev))
219 throw Xapian::DatabaseError("Changes file - bad version file revision");
220 if (rev != version_rev)
221 throw Xapian::DatabaseError("Version file revision != changes file new revision");
222 size_t len;
223 if (!unpack_uint(&p, end, &len))
224 throw Xapian::DatabaseError("Changes file - bad version file length");
225 if (len <= size_t(end - p)) {
226 p += len;
227 } else {
228 if (lseek(fd, len - (end - p), SEEK_CUR) < 0)
229 throw Xapian::DatabaseError("Changes file - version file data truncated");
230 p = end = buf;
231 n = 0;
232 }
233 continue;
234 }
235 unsigned table = (v & 0x7);
236 v >>= 3;
237 if (table > 5)
238 throw Xapian::DatabaseError("Changes file - bad table code");
239 // Changed block.
240 if (v > 5)
241 throw Xapian::DatabaseError("Changes file - bad block size");
242 unsigned block_size = 2048 << v;
243 uint4 block_number;
244 if (!unpack_uint(&p, end, &block_number))
245 throw Xapian::DatabaseError("Changes file - bad block number");
246
247 // Parse information from the start of the block.
248 //
249 // Although the revision number is aligned within the block, the block
250 // data may not be aligned to a word boundary here.
251 uint4 block_rev = unaligned_read4(reinterpret_cast<const uint8_t*>(p));
252 (void)block_rev; // FIXME: Sanity check value.
253 unsigned level = static_cast<unsigned char>(p[4]);
254 (void)level; // FIXME: Sanity check value.
255
256 // Skip over the block content.
257 if (block_size <= unsigned(end - p)) {
258 p += block_size;
259 } else {
260 if (lseek(fd, block_size - (end - p), SEEK_CUR) < 0)
261 throw Xapian::DatabaseError("Changes file - block data truncated");
262 p = end = buf;
263 n = 0;
264 }
265 }
266 }
267