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5ca28f79 L |
1 | /* |
2 | * gzlog.c | |
de1ab01e | 3 | * Copyright (C) 2004, 2008, 2012, 2016 Mark Adler, all rights reserved |
5ca28f79 | 4 | * For conditions of distribution and use, see copyright notice in gzlog.h |
da09a436 | 5 | * version 2.2, 14 Aug 2012 |
5ca28f79 L |
6 | */ |
7 | ||
8 | /* | |
9 | gzlog provides a mechanism for frequently appending short strings to a gzip | |
10 | file that is efficient both in execution time and compression ratio. The | |
11 | strategy is to write the short strings in an uncompressed form to the end of | |
12 | the gzip file, only compressing when the amount of uncompressed data has | |
13 | reached a given threshold. | |
14 | ||
15 | gzlog also provides protection against interruptions in the process due to | |
16 | system crashes. The status of the operation is recorded in an extra field | |
17 | in the gzip file, and is only updated once the gzip file is brought to a | |
18 | valid state. The last data to be appended or compressed is saved in an | |
19 | auxiliary file, so that if the operation is interrupted, it can be completed | |
20 | the next time an append operation is attempted. | |
21 | ||
22 | gzlog maintains another auxiliary file with the last 32K of data from the | |
23 | compressed portion, which is preloaded for the compression of the subsequent | |
24 | data. This minimizes the impact to the compression ratio of appending. | |
25 | */ | |
26 | ||
27 | /* | |
28 | Operations Concept: | |
29 | ||
30 | Files (log name "foo"): | |
31 | foo.gz -- gzip file with the complete log | |
32 | foo.add -- last message to append or last data to compress | |
33 | foo.dict -- dictionary of the last 32K of data for next compression | |
34 | foo.temp -- temporary dictionary file for compression after this one | |
35 | foo.lock -- lock file for reading and writing the other files | |
36 | foo.repairs -- log file for log file recovery operations (not compressed) | |
37 | ||
38 | gzip file structure: | |
39 | - fixed-length (no file name) header with extra field (see below) | |
40 | - compressed data ending initially with empty stored block | |
41 | - uncompressed data filling out originally empty stored block and | |
42 | subsequent stored blocks as needed (16K max each) | |
43 | - gzip trailer | |
44 | - no junk at end (no other gzip streams) | |
45 | ||
46 | When appending data, the information in the first three items above plus the | |
47 | foo.add file are sufficient to recover an interrupted append operation. The | |
48 | extra field has the necessary information to restore the start of the last | |
49 | stored block and determine where to append the data in the foo.add file, as | |
50 | well as the crc and length of the gzip data before the append operation. | |
51 | ||
52 | The foo.add file is created before the gzip file is marked for append, and | |
53 | deleted after the gzip file is marked as complete. So if the append | |
54 | operation is interrupted, the data to add will still be there. If due to | |
55 | some external force, the foo.add file gets deleted between when the append | |
56 | operation was interrupted and when recovery is attempted, the gzip file will | |
57 | still be restored, but without the appended data. | |
58 | ||
59 | When compressing data, the information in the first two items above plus the | |
60 | foo.add file are sufficient to recover an interrupted compress operation. | |
61 | The extra field has the necessary information to find the end of the | |
62 | compressed data, and contains both the crc and length of just the compressed | |
63 | data and of the complete set of data including the contents of the foo.add | |
64 | file. | |
65 | ||
66 | Again, the foo.add file is maintained during the compress operation in case | |
67 | of an interruption. If in the unlikely event the foo.add file with the data | |
68 | to be compressed is missing due to some external force, a gzip file with | |
69 | just the previous compressed data will be reconstructed. In this case, all | |
70 | of the data that was to be compressed is lost (approximately one megabyte). | |
71 | This will not occur if all that happened was an interruption of the compress | |
72 | operation. | |
73 | ||
74 | The third state that is marked is the replacement of the old dictionary with | |
75 | the new dictionary after a compress operation. Once compression is | |
76 | complete, the gzip file is marked as being in the replace state. This | |
77 | completes the gzip file, so an interrupt after being so marked does not | |
78 | result in recompression. Then the dictionary file is replaced, and the gzip | |
79 | file is marked as completed. This state prevents the possibility of | |
80 | restarting compression with the wrong dictionary file. | |
81 | ||
82 | All three operations are wrapped by a lock/unlock procedure. In order to | |
83 | gain exclusive access to the log files, first a foo.lock file must be | |
84 | exclusively created. When all operations are complete, the lock is | |
85 | released by deleting the foo.lock file. If when attempting to create the | |
86 | lock file, it already exists and the modify time of the lock file is more | |
87 | than five minutes old (set by the PATIENCE define below), then the old | |
88 | lock file is considered stale and deleted, and the exclusive creation of | |
89 | the lock file is retried. To assure that there are no false assessments | |
90 | of the staleness of the lock file, the operations periodically touch the | |
91 | lock file to update the modified date. | |
92 | ||
93 | Following is the definition of the extra field with all of the information | |
94 | required to enable the above append and compress operations and their | |
95 | recovery if interrupted. Multi-byte values are stored little endian | |
96 | (consistent with the gzip format). File pointers are eight bytes long. | |
97 | The crc's and lengths for the gzip trailer are four bytes long. (Note that | |
98 | the length at the end of a gzip file is used for error checking only, and | |
99 | for large files is actually the length modulo 2^32.) The stored block | |
100 | length is two bytes long. The gzip extra field two-byte identification is | |
101 | "ap" for append. It is assumed that writing the extra field to the file is | |
102 | an "atomic" operation. That is, either all of the extra field is written | |
103 | to the file, or none of it is, if the operation is interrupted right at the | |
104 | point of updating the extra field. This is a reasonable assumption, since | |
105 | the extra field is within the first 52 bytes of the file, which is smaller | |
106 | than any expected block size for a mass storage device (usually 512 bytes or | |
107 | larger). | |
108 | ||
109 | Extra field (35 bytes): | |
110 | - Pointer to first stored block length -- this points to the two-byte length | |
111 | of the first stored block, which is followed by the two-byte, one's | |
112 | complement of that length. The stored block length is preceded by the | |
113 | three-bit header of the stored block, which is the actual start of the | |
114 | stored block in the deflate format. See the bit offset field below. | |
115 | - Pointer to the last stored block length. This is the same as above, but | |
116 | for the last stored block of the uncompressed data in the gzip file. | |
117 | Initially this is the same as the first stored block length pointer. | |
118 | When the stored block gets to 16K (see the MAX_STORE define), then a new | |
119 | stored block as added, at which point the last stored block length pointer | |
120 | is different from the first stored block length pointer. When they are | |
121 | different, the first bit of the last stored block header is eight bits, or | |
122 | one byte back from the block length. | |
123 | - Compressed data crc and length. This is the crc and length of the data | |
124 | that is in the compressed portion of the deflate stream. These are used | |
125 | only in the event that the foo.add file containing the data to compress is | |
126 | lost after a compress operation is interrupted. | |
127 | - Total data crc and length. This is the crc and length of all of the data | |
128 | stored in the gzip file, compressed and uncompressed. It is used to | |
129 | reconstruct the gzip trailer when compressing, as well as when recovering | |
130 | interrupted operations. | |
131 | - Final stored block length. This is used to quickly find where to append, | |
132 | and allows the restoration of the original final stored block state when | |
133 | an append operation is interrupted. | |
134 | - First stored block start as the number of bits back from the final stored | |
135 | block first length byte. This value is in the range of 3..10, and is | |
136 | stored as the low three bits of the final byte of the extra field after | |
137 | subtracting three (0..7). This allows the last-block bit of the stored | |
138 | block header to be updated when a new stored block is added, for the case | |
139 | when the first stored block and the last stored block are the same. (When | |
140 | they are different, the numbers of bits back is known to be eight.) This | |
141 | also allows for new compressed data to be appended to the old compressed | |
142 | data in the compress operation, overwriting the previous first stored | |
143 | block, or for the compressed data to be terminated and a valid gzip file | |
144 | reconstructed on the off chance that a compression operation was | |
145 | interrupted and the data to compress in the foo.add file was deleted. | |
146 | - The operation in process. This is the next two bits in the last byte (the | |
147 | bits under the mask 0x18). The are interpreted as 0: nothing in process, | |
148 | 1: append in process, 2: compress in process, 3: replace in process. | |
149 | - The top three bits of the last byte in the extra field are reserved and | |
150 | are currently set to zero. | |
151 | ||
152 | Main procedure: | |
153 | - Exclusively create the foo.lock file using the O_CREAT and O_EXCL modes of | |
154 | the system open() call. If the modify time of an existing lock file is | |
155 | more than PATIENCE seconds old, then the lock file is deleted and the | |
156 | exclusive create is retried. | |
157 | - Load the extra field from the foo.gz file, and see if an operation was in | |
158 | progress but not completed. If so, apply the recovery procedure below. | |
159 | - Perform the append procedure with the provided data. | |
160 | - If the uncompressed data in the foo.gz file is 1MB or more, apply the | |
161 | compress procedure. | |
162 | - Delete the foo.lock file. | |
163 | ||
164 | Append procedure: | |
165 | - Put what to append in the foo.add file so that the operation can be | |
166 | restarted if this procedure is interrupted. | |
167 | - Mark the foo.gz extra field with the append operation in progress. | |
168 | + Restore the original last-block bit and stored block length of the last | |
169 | stored block from the information in the extra field, in case a previous | |
170 | append operation was interrupted. | |
171 | - Append the provided data to the last stored block, creating new stored | |
172 | blocks as needed and updating the stored blocks last-block bits and | |
173 | lengths. | |
174 | - Update the crc and length with the new data, and write the gzip trailer. | |
175 | - Write over the extra field (with a single write operation) with the new | |
176 | pointers, lengths, and crc's, and mark the gzip file as not in process. | |
177 | Though there is still a foo.add file, it will be ignored since nothing | |
178 | is in process. If a foo.add file is leftover from a previously | |
179 | completed operation, it is truncated when writing new data to it. | |
180 | - Delete the foo.add file. | |
181 | ||
182 | Compress and replace procedures: | |
183 | - Read all of the uncompressed data in the stored blocks in foo.gz and write | |
184 | it to foo.add. Also write foo.temp with the last 32K of that data to | |
185 | provide a dictionary for the next invocation of this procedure. | |
186 | - Rewrite the extra field marking foo.gz with a compression in process. | |
187 | * If there is no data provided to compress (due to a missing foo.add file | |
188 | when recovering), reconstruct and truncate the foo.gz file to contain | |
189 | only the previous compressed data and proceed to the step after the next | |
190 | one. Otherwise ... | |
191 | - Compress the data with the dictionary in foo.dict, and write to the | |
192 | foo.gz file starting at the bit immediately following the last previously | |
193 | compressed block. If there is no foo.dict, proceed anyway with the | |
194 | compression at slightly reduced efficiency. (For the foo.dict file to be | |
195 | missing requires some external failure beyond simply the interruption of | |
196 | a compress operation.) During this process, the foo.lock file is | |
197 | periodically touched to assure that that file is not considered stale by | |
198 | another process before we're done. The deflation is terminated with a | |
199 | non-last empty static block (10 bits long), that is then located and | |
200 | written over by a last-bit-set empty stored block. | |
201 | - Append the crc and length of the data in the gzip file (previously | |
202 | calculated during the append operations). | |
203 | - Write over the extra field with the updated stored block offsets, bits | |
204 | back, crc's, and lengths, and mark foo.gz as in process for a replacement | |
205 | of the dictionary. | |
206 | @ Delete the foo.add file. | |
207 | - Replace foo.dict with foo.temp. | |
208 | - Write over the extra field, marking foo.gz as complete. | |
209 | ||
210 | Recovery procedure: | |
211 | - If not a replace recovery, read in the foo.add file, and provide that data | |
212 | to the appropriate recovery below. If there is no foo.add file, provide | |
213 | a zero data length to the recovery. In that case, the append recovery | |
214 | restores the foo.gz to the previous compressed + uncompressed data state. | |
215 | For the the compress recovery, a missing foo.add file results in foo.gz | |
216 | being restored to the previous compressed-only data state. | |
217 | - Append recovery: | |
218 | - Pick up append at + step above | |
219 | - Compress recovery: | |
220 | - Pick up compress at * step above | |
221 | - Replace recovery: | |
222 | - Pick up compress at @ step above | |
223 | - Log the repair with a date stamp in foo.repairs | |
224 | */ | |
225 | ||
226 | #include <sys/types.h> | |
227 | #include <stdio.h> /* rename, fopen, fprintf, fclose */ | |
228 | #include <stdlib.h> /* malloc, free */ | |
229 | #include <string.h> /* strlen, strrchr, strcpy, strncpy, strcmp */ | |
230 | #include <fcntl.h> /* open */ | |
231 | #include <unistd.h> /* lseek, read, write, close, unlink, sleep, */ | |
232 | /* ftruncate, fsync */ | |
233 | #include <errno.h> /* errno */ | |
234 | #include <time.h> /* time, ctime */ | |
235 | #include <sys/stat.h> /* stat */ | |
236 | #include <sys/time.h> /* utimes */ | |
237 | #include "zlib.h" /* crc32 */ | |
238 | ||
239 | #include "gzlog.h" /* header for external access */ | |
240 | ||
241 | #define local static | |
242 | typedef unsigned int uint; | |
243 | typedef unsigned long ulong; | |
244 | ||
245 | /* Macro for debugging to deterministically force recovery operations */ | |
de1ab01e | 246 | #ifdef GZLOG_DEBUG |
5ca28f79 L |
247 | #include <setjmp.h> /* longjmp */ |
248 | jmp_buf gzlog_jump; /* where to go back to */ | |
249 | int gzlog_bail = 0; /* which point to bail at (1..8) */ | |
250 | int gzlog_count = -1; /* number of times through to wait */ | |
251 | # define BAIL(n) do { if (n == gzlog_bail && gzlog_count-- == 0) \ | |
252 | longjmp(gzlog_jump, gzlog_bail); } while (0) | |
253 | #else | |
254 | # define BAIL(n) | |
255 | #endif | |
256 | ||
257 | /* how old the lock file can be in seconds before considering it stale */ | |
258 | #define PATIENCE 300 | |
259 | ||
260 | /* maximum stored block size in Kbytes -- must be in 1..63 */ | |
261 | #define MAX_STORE 16 | |
262 | ||
263 | /* number of stored Kbytes to trigger compression (must be >= 32 to allow | |
264 | dictionary construction, and <= 204 * MAX_STORE, in order for >> 10 to | |
265 | discard the stored block headers contribution of five bytes each) */ | |
266 | #define TRIGGER 1024 | |
267 | ||
268 | /* size of a deflate dictionary (this cannot be changed) */ | |
269 | #define DICT 32768U | |
270 | ||
271 | /* values for the operation (2 bits) */ | |
272 | #define NO_OP 0 | |
273 | #define APPEND_OP 1 | |
274 | #define COMPRESS_OP 2 | |
275 | #define REPLACE_OP 3 | |
276 | ||
277 | /* macros to extract little-endian integers from an unsigned byte buffer */ | |
278 | #define PULL2(p) ((p)[0]+((uint)((p)[1])<<8)) | |
279 | #define PULL4(p) (PULL2(p)+((ulong)PULL2(p+2)<<16)) | |
280 | #define PULL8(p) (PULL4(p)+((off_t)PULL4(p+4)<<32)) | |
281 | ||
282 | /* macros to store integers into a byte buffer in little-endian order */ | |
283 | #define PUT2(p,a) do {(p)[0]=a;(p)[1]=(a)>>8;} while(0) | |
284 | #define PUT4(p,a) do {PUT2(p,a);PUT2(p+2,a>>16);} while(0) | |
285 | #define PUT8(p,a) do {PUT4(p,a);PUT4(p+4,a>>32);} while(0) | |
286 | ||
287 | /* internal structure for log information */ | |
288 | #define LOGID "\106\035\172" /* should be three non-zero characters */ | |
289 | struct log { | |
290 | char id[4]; /* contains LOGID to detect inadvertent overwrites */ | |
291 | int fd; /* file descriptor for .gz file, opened read/write */ | |
292 | char *path; /* allocated path, e.g. "/var/log/foo" or "foo" */ | |
293 | char *end; /* end of path, for appending suffices such as ".gz" */ | |
294 | off_t first; /* offset of first stored block first length byte */ | |
295 | int back; /* location of first block id in bits back from first */ | |
296 | uint stored; /* bytes currently in last stored block */ | |
297 | off_t last; /* offset of last stored block first length byte */ | |
298 | ulong ccrc; /* crc of compressed data */ | |
299 | ulong clen; /* length (modulo 2^32) of compressed data */ | |
300 | ulong tcrc; /* crc of total data */ | |
301 | ulong tlen; /* length (modulo 2^32) of total data */ | |
302 | time_t lock; /* last modify time of our lock file */ | |
303 | }; | |
304 | ||
305 | /* gzip header for gzlog */ | |
306 | local unsigned char log_gzhead[] = { | |
307 | 0x1f, 0x8b, /* magic gzip id */ | |
308 | 8, /* compression method is deflate */ | |
309 | 4, /* there is an extra field (no file name) */ | |
310 | 0, 0, 0, 0, /* no modification time provided */ | |
311 | 0, 0xff, /* no extra flags, no OS specified */ | |
312 | 39, 0, 'a', 'p', 35, 0 /* extra field with "ap" subfield */ | |
313 | /* 35 is EXTRA, 39 is EXTRA + 4 */ | |
314 | }; | |
315 | ||
316 | #define HEAD sizeof(log_gzhead) /* should be 16 */ | |
317 | ||
318 | /* initial gzip extra field content (52 == HEAD + EXTRA + 1) */ | |
319 | local unsigned char log_gzext[] = { | |
320 | 52, 0, 0, 0, 0, 0, 0, 0, /* offset of first stored block length */ | |
321 | 52, 0, 0, 0, 0, 0, 0, 0, /* offset of last stored block length */ | |
322 | 0, 0, 0, 0, 0, 0, 0, 0, /* compressed data crc and length */ | |
323 | 0, 0, 0, 0, 0, 0, 0, 0, /* total data crc and length */ | |
324 | 0, 0, /* final stored block data length */ | |
325 | 5 /* op is NO_OP, last bit 8 bits back */ | |
326 | }; | |
327 | ||
328 | #define EXTRA sizeof(log_gzext) /* should be 35 */ | |
329 | ||
330 | /* initial gzip data and trailer */ | |
331 | local unsigned char log_gzbody[] = { | |
332 | 1, 0, 0, 0xff, 0xff, /* empty stored block (last) */ | |
333 | 0, 0, 0, 0, /* crc */ | |
334 | 0, 0, 0, 0 /* uncompressed length */ | |
335 | }; | |
336 | ||
337 | #define BODY sizeof(log_gzbody) | |
338 | ||
339 | /* Exclusively create foo.lock in order to negotiate exclusive access to the | |
340 | foo.* files. If the modify time of an existing lock file is greater than | |
341 | PATIENCE seconds in the past, then consider the lock file to have been | |
342 | abandoned, delete it, and try the exclusive create again. Save the lock | |
343 | file modify time for verification of ownership. Return 0 on success, or -1 | |
344 | on failure, usually due to an access restriction or invalid path. Note that | |
345 | if stat() or unlink() fails, it may be due to another process noticing the | |
346 | abandoned lock file a smidge sooner and deleting it, so those are not | |
347 | flagged as an error. */ | |
348 | local int log_lock(struct log *log) | |
349 | { | |
350 | int fd; | |
351 | struct stat st; | |
352 | ||
353 | strcpy(log->end, ".lock"); | |
354 | while ((fd = open(log->path, O_CREAT | O_EXCL, 0644)) < 0) { | |
355 | if (errno != EEXIST) | |
356 | return -1; | |
357 | if (stat(log->path, &st) == 0 && time(NULL) - st.st_mtime > PATIENCE) { | |
358 | unlink(log->path); | |
359 | continue; | |
360 | } | |
361 | sleep(2); /* relinquish the CPU for two seconds while waiting */ | |
362 | } | |
363 | close(fd); | |
364 | if (stat(log->path, &st) == 0) | |
365 | log->lock = st.st_mtime; | |
366 | return 0; | |
367 | } | |
368 | ||
369 | /* Update the modify time of the lock file to now, in order to prevent another | |
370 | task from thinking that the lock is stale. Save the lock file modify time | |
371 | for verification of ownership. */ | |
372 | local void log_touch(struct log *log) | |
373 | { | |
374 | struct stat st; | |
375 | ||
376 | strcpy(log->end, ".lock"); | |
377 | utimes(log->path, NULL); | |
378 | if (stat(log->path, &st) == 0) | |
379 | log->lock = st.st_mtime; | |
380 | } | |
381 | ||
382 | /* Check the log file modify time against what is expected. Return true if | |
383 | this is not our lock. If it is our lock, touch it to keep it. */ | |
384 | local int log_check(struct log *log) | |
385 | { | |
386 | struct stat st; | |
387 | ||
388 | strcpy(log->end, ".lock"); | |
389 | if (stat(log->path, &st) || st.st_mtime != log->lock) | |
390 | return 1; | |
391 | log_touch(log); | |
392 | return 0; | |
393 | } | |
394 | ||
395 | /* Unlock a previously acquired lock, but only if it's ours. */ | |
396 | local void log_unlock(struct log *log) | |
397 | { | |
398 | if (log_check(log)) | |
399 | return; | |
400 | strcpy(log->end, ".lock"); | |
401 | unlink(log->path); | |
402 | log->lock = 0; | |
403 | } | |
404 | ||
405 | /* Check the gzip header and read in the extra field, filling in the values in | |
406 | the log structure. Return op on success or -1 if the gzip header was not as | |
407 | expected. op is the current operation in progress last written to the extra | |
408 | field. This assumes that the gzip file has already been opened, with the | |
409 | file descriptor log->fd. */ | |
410 | local int log_head(struct log *log) | |
411 | { | |
412 | int op; | |
413 | unsigned char buf[HEAD + EXTRA]; | |
414 | ||
415 | if (lseek(log->fd, 0, SEEK_SET) < 0 || | |
416 | read(log->fd, buf, HEAD + EXTRA) != HEAD + EXTRA || | |
417 | memcmp(buf, log_gzhead, HEAD)) { | |
418 | return -1; | |
419 | } | |
420 | log->first = PULL8(buf + HEAD); | |
421 | log->last = PULL8(buf + HEAD + 8); | |
422 | log->ccrc = PULL4(buf + HEAD + 16); | |
423 | log->clen = PULL4(buf + HEAD + 20); | |
424 | log->tcrc = PULL4(buf + HEAD + 24); | |
425 | log->tlen = PULL4(buf + HEAD + 28); | |
426 | log->stored = PULL2(buf + HEAD + 32); | |
427 | log->back = 3 + (buf[HEAD + 34] & 7); | |
428 | op = (buf[HEAD + 34] >> 3) & 3; | |
429 | return op; | |
430 | } | |
431 | ||
432 | /* Write over the extra field contents, marking the operation as op. Use fsync | |
433 | to assure that the device is written to, and in the requested order. This | |
434 | operation, and only this operation, is assumed to be atomic in order to | |
435 | assure that the log is recoverable in the event of an interruption at any | |
436 | point in the process. Return -1 if the write to foo.gz failed. */ | |
437 | local int log_mark(struct log *log, int op) | |
438 | { | |
439 | int ret; | |
440 | unsigned char ext[EXTRA]; | |
441 | ||
442 | PUT8(ext, log->first); | |
443 | PUT8(ext + 8, log->last); | |
444 | PUT4(ext + 16, log->ccrc); | |
445 | PUT4(ext + 20, log->clen); | |
446 | PUT4(ext + 24, log->tcrc); | |
447 | PUT4(ext + 28, log->tlen); | |
448 | PUT2(ext + 32, log->stored); | |
449 | ext[34] = log->back - 3 + (op << 3); | |
450 | fsync(log->fd); | |
451 | ret = lseek(log->fd, HEAD, SEEK_SET) < 0 || | |
452 | write(log->fd, ext, EXTRA) != EXTRA ? -1 : 0; | |
453 | fsync(log->fd); | |
454 | return ret; | |
455 | } | |
456 | ||
457 | /* Rewrite the last block header bits and subsequent zero bits to get to a byte | |
458 | boundary, setting the last block bit if last is true, and then write the | |
459 | remainder of the stored block header (length and one's complement). Leave | |
460 | the file pointer after the end of the last stored block data. Return -1 if | |
461 | there is a read or write failure on the foo.gz file */ | |
462 | local int log_last(struct log *log, int last) | |
463 | { | |
464 | int back, len, mask; | |
465 | unsigned char buf[6]; | |
466 | ||
467 | /* determine the locations of the bytes and bits to modify */ | |
468 | back = log->last == log->first ? log->back : 8; | |
469 | len = back > 8 ? 2 : 1; /* bytes back from log->last */ | |
470 | mask = 0x80 >> ((back - 1) & 7); /* mask for block last-bit */ | |
471 | ||
472 | /* get the byte to modify (one or two back) into buf[0] -- don't need to | |
473 | read the byte if the last-bit is eight bits back, since in that case | |
474 | the entire byte will be modified */ | |
475 | buf[0] = 0; | |
476 | if (back != 8 && (lseek(log->fd, log->last - len, SEEK_SET) < 0 || | |
477 | read(log->fd, buf, 1) != 1)) | |
478 | return -1; | |
479 | ||
480 | /* change the last-bit of the last stored block as requested -- note | |
481 | that all bits above the last-bit are set to zero, per the type bits | |
482 | of a stored block being 00 and per the convention that the bits to | |
483 | bring the stream to a byte boundary are also zeros */ | |
484 | buf[1] = 0; | |
485 | buf[2 - len] = (*buf & (mask - 1)) + (last ? mask : 0); | |
486 | ||
487 | /* write the modified stored block header and lengths, move the file | |
488 | pointer to after the last stored block data */ | |
489 | PUT2(buf + 2, log->stored); | |
490 | PUT2(buf + 4, log->stored ^ 0xffff); | |
491 | return lseek(log->fd, log->last - len, SEEK_SET) < 0 || | |
492 | write(log->fd, buf + 2 - len, len + 4) != len + 4 || | |
493 | lseek(log->fd, log->stored, SEEK_CUR) < 0 ? -1 : 0; | |
494 | } | |
495 | ||
496 | /* Append len bytes from data to the locked and open log file. len may be zero | |
497 | if recovering and no .add file was found. In that case, the previous state | |
498 | of the foo.gz file is restored. The data is appended uncompressed in | |
499 | deflate stored blocks. Return -1 if there was an error reading or writing | |
500 | the foo.gz file. */ | |
501 | local int log_append(struct log *log, unsigned char *data, size_t len) | |
502 | { | |
503 | uint put; | |
504 | off_t end; | |
505 | unsigned char buf[8]; | |
506 | ||
507 | /* set the last block last-bit and length, in case recovering an | |
508 | interrupted append, then position the file pointer to append to the | |
509 | block */ | |
510 | if (log_last(log, 1)) | |
511 | return -1; | |
512 | ||
513 | /* append, adding stored blocks and updating the offset of the last stored | |
514 | block as needed, and update the total crc and length */ | |
515 | while (len) { | |
516 | /* append as much as we can to the last block */ | |
517 | put = (MAX_STORE << 10) - log->stored; | |
518 | if (put > len) | |
519 | put = (uint)len; | |
520 | if (put) { | |
521 | if (write(log->fd, data, put) != put) | |
522 | return -1; | |
523 | BAIL(1); | |
524 | log->tcrc = crc32(log->tcrc, data, put); | |
525 | log->tlen += put; | |
526 | log->stored += put; | |
527 | data += put; | |
528 | len -= put; | |
529 | } | |
530 | ||
531 | /* if we need to, add a new empty stored block */ | |
532 | if (len) { | |
533 | /* mark current block as not last */ | |
534 | if (log_last(log, 0)) | |
535 | return -1; | |
536 | ||
537 | /* point to new, empty stored block */ | |
538 | log->last += 4 + log->stored + 1; | |
539 | log->stored = 0; | |
540 | } | |
541 | ||
542 | /* mark last block as last, update its length */ | |
543 | if (log_last(log, 1)) | |
544 | return -1; | |
545 | BAIL(2); | |
546 | } | |
547 | ||
548 | /* write the new crc and length trailer, and truncate just in case (could | |
549 | be recovering from partial append with a missing foo.add file) */ | |
550 | PUT4(buf, log->tcrc); | |
551 | PUT4(buf + 4, log->tlen); | |
552 | if (write(log->fd, buf, 8) != 8 || | |
553 | (end = lseek(log->fd, 0, SEEK_CUR)) < 0 || ftruncate(log->fd, end)) | |
554 | return -1; | |
555 | ||
556 | /* write the extra field, marking the log file as done, delete .add file */ | |
557 | if (log_mark(log, NO_OP)) | |
558 | return -1; | |
559 | strcpy(log->end, ".add"); | |
560 | unlink(log->path); /* ignore error, since may not exist */ | |
561 | return 0; | |
562 | } | |
563 | ||
564 | /* Replace the foo.dict file with the foo.temp file. Also delete the foo.add | |
565 | file, since the compress operation may have been interrupted before that was | |
566 | done. Returns 1 if memory could not be allocated, or -1 if reading or | |
567 | writing foo.gz fails, or if the rename fails for some reason other than | |
568 | foo.temp not existing. foo.temp not existing is a permitted error, since | |
569 | the replace operation may have been interrupted after the rename is done, | |
570 | but before foo.gz is marked as complete. */ | |
571 | local int log_replace(struct log *log) | |
572 | { | |
573 | int ret; | |
574 | char *dest; | |
575 | ||
576 | /* delete foo.add file */ | |
577 | strcpy(log->end, ".add"); | |
578 | unlink(log->path); /* ignore error, since may not exist */ | |
579 | BAIL(3); | |
580 | ||
581 | /* rename foo.name to foo.dict, replacing foo.dict if it exists */ | |
582 | strcpy(log->end, ".dict"); | |
583 | dest = malloc(strlen(log->path) + 1); | |
584 | if (dest == NULL) | |
585 | return -2; | |
586 | strcpy(dest, log->path); | |
587 | strcpy(log->end, ".temp"); | |
588 | ret = rename(log->path, dest); | |
589 | free(dest); | |
590 | if (ret && errno != ENOENT) | |
591 | return -1; | |
592 | BAIL(4); | |
593 | ||
594 | /* mark the foo.gz file as done */ | |
595 | return log_mark(log, NO_OP); | |
596 | } | |
597 | ||
598 | /* Compress the len bytes at data and append the compressed data to the | |
599 | foo.gz deflate data immediately after the previous compressed data. This | |
600 | overwrites the previous uncompressed data, which was stored in foo.add | |
601 | and is the data provided in data[0..len-1]. If this operation is | |
602 | interrupted, it picks up at the start of this routine, with the foo.add | |
603 | file read in again. If there is no data to compress (len == 0), then we | |
604 | simply terminate the foo.gz file after the previously compressed data, | |
605 | appending a final empty stored block and the gzip trailer. Return -1 if | |
606 | reading or writing the log.gz file failed, or -2 if there was a memory | |
607 | allocation failure. */ | |
608 | local int log_compress(struct log *log, unsigned char *data, size_t len) | |
609 | { | |
610 | int fd; | |
611 | uint got, max; | |
612 | ssize_t dict; | |
613 | off_t end; | |
614 | z_stream strm; | |
615 | unsigned char buf[DICT]; | |
616 | ||
617 | /* compress and append compressed data */ | |
618 | if (len) { | |
619 | /* set up for deflate, allocating memory */ | |
620 | strm.zalloc = Z_NULL; | |
621 | strm.zfree = Z_NULL; | |
622 | strm.opaque = Z_NULL; | |
623 | if (deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, -15, 8, | |
624 | Z_DEFAULT_STRATEGY) != Z_OK) | |
625 | return -2; | |
626 | ||
627 | /* read in dictionary (last 32K of data that was compressed) */ | |
628 | strcpy(log->end, ".dict"); | |
629 | fd = open(log->path, O_RDONLY, 0); | |
630 | if (fd >= 0) { | |
631 | dict = read(fd, buf, DICT); | |
632 | close(fd); | |
633 | if (dict < 0) { | |
634 | deflateEnd(&strm); | |
635 | return -1; | |
636 | } | |
637 | if (dict) | |
638 | deflateSetDictionary(&strm, buf, (uint)dict); | |
639 | } | |
640 | log_touch(log); | |
641 | ||
642 | /* prime deflate with last bits of previous block, position write | |
643 | pointer to write those bits and overwrite what follows */ | |
644 | if (lseek(log->fd, log->first - (log->back > 8 ? 2 : 1), | |
645 | SEEK_SET) < 0 || | |
646 | read(log->fd, buf, 1) != 1 || lseek(log->fd, -1, SEEK_CUR) < 0) { | |
647 | deflateEnd(&strm); | |
648 | return -1; | |
649 | } | |
650 | deflatePrime(&strm, (8 - log->back) & 7, *buf); | |
651 | ||
652 | /* compress, finishing with a partial non-last empty static block */ | |
653 | strm.next_in = data; | |
654 | max = (((uint)0 - 1) >> 1) + 1; /* in case int smaller than size_t */ | |
655 | do { | |
656 | strm.avail_in = len > max ? max : (uint)len; | |
657 | len -= strm.avail_in; | |
658 | do { | |
659 | strm.avail_out = DICT; | |
660 | strm.next_out = buf; | |
661 | deflate(&strm, len ? Z_NO_FLUSH : Z_PARTIAL_FLUSH); | |
662 | got = DICT - strm.avail_out; | |
663 | if (got && write(log->fd, buf, got) != got) { | |
664 | deflateEnd(&strm); | |
665 | return -1; | |
666 | } | |
667 | log_touch(log); | |
668 | } while (strm.avail_out == 0); | |
669 | } while (len); | |
670 | deflateEnd(&strm); | |
671 | BAIL(5); | |
672 | ||
673 | /* find start of empty static block -- scanning backwards the first one | |
674 | bit is the second bit of the block, if the last byte is zero, then | |
675 | we know the byte before that has a one in the top bit, since an | |
676 | empty static block is ten bits long */ | |
677 | if ((log->first = lseek(log->fd, -1, SEEK_CUR)) < 0 || | |
678 | read(log->fd, buf, 1) != 1) | |
679 | return -1; | |
680 | log->first++; | |
681 | if (*buf) { | |
682 | log->back = 1; | |
683 | while ((*buf & ((uint)1 << (8 - log->back++))) == 0) | |
684 | ; /* guaranteed to terminate, since *buf != 0 */ | |
685 | } | |
686 | else | |
687 | log->back = 10; | |
688 | ||
689 | /* update compressed crc and length */ | |
690 | log->ccrc = log->tcrc; | |
691 | log->clen = log->tlen; | |
692 | } | |
693 | else { | |
694 | /* no data to compress -- fix up existing gzip stream */ | |
695 | log->tcrc = log->ccrc; | |
696 | log->tlen = log->clen; | |
697 | } | |
698 | ||
699 | /* complete and truncate gzip stream */ | |
700 | log->last = log->first; | |
701 | log->stored = 0; | |
702 | PUT4(buf, log->tcrc); | |
703 | PUT4(buf + 4, log->tlen); | |
704 | if (log_last(log, 1) || write(log->fd, buf, 8) != 8 || | |
705 | (end = lseek(log->fd, 0, SEEK_CUR)) < 0 || ftruncate(log->fd, end)) | |
706 | return -1; | |
707 | BAIL(6); | |
708 | ||
709 | /* mark as being in the replace operation */ | |
710 | if (log_mark(log, REPLACE_OP)) | |
711 | return -1; | |
712 | ||
713 | /* execute the replace operation and mark the file as done */ | |
714 | return log_replace(log); | |
715 | } | |
716 | ||
717 | /* log a repair record to the .repairs file */ | |
718 | local void log_log(struct log *log, int op, char *record) | |
719 | { | |
720 | time_t now; | |
721 | FILE *rec; | |
722 | ||
723 | now = time(NULL); | |
724 | strcpy(log->end, ".repairs"); | |
725 | rec = fopen(log->path, "a"); | |
726 | if (rec == NULL) | |
727 | return; | |
728 | fprintf(rec, "%.24s %s recovery: %s\n", ctime(&now), op == APPEND_OP ? | |
729 | "append" : (op == COMPRESS_OP ? "compress" : "replace"), record); | |
730 | fclose(rec); | |
731 | return; | |
732 | } | |
733 | ||
734 | /* Recover the interrupted operation op. First read foo.add for recovering an | |
735 | append or compress operation. Return -1 if there was an error reading or | |
736 | writing foo.gz or reading an existing foo.add, or -2 if there was a memory | |
737 | allocation failure. */ | |
738 | local int log_recover(struct log *log, int op) | |
739 | { | |
740 | int fd, ret = 0; | |
741 | unsigned char *data = NULL; | |
742 | size_t len = 0; | |
743 | struct stat st; | |
744 | ||
745 | /* log recovery */ | |
746 | log_log(log, op, "start"); | |
747 | ||
748 | /* load foo.add file if expected and present */ | |
749 | if (op == APPEND_OP || op == COMPRESS_OP) { | |
750 | strcpy(log->end, ".add"); | |
751 | if (stat(log->path, &st) == 0 && st.st_size) { | |
752 | len = (size_t)(st.st_size); | |
da09a436 JB |
753 | if ((off_t)len != st.st_size || |
754 | (data = malloc(st.st_size)) == NULL) { | |
5ca28f79 L |
755 | log_log(log, op, "allocation failure"); |
756 | return -2; | |
757 | } | |
758 | if ((fd = open(log->path, O_RDONLY, 0)) < 0) { | |
759 | log_log(log, op, ".add file read failure"); | |
760 | return -1; | |
761 | } | |
da09a436 | 762 | ret = (size_t)read(fd, data, len) != len; |
5ca28f79 L |
763 | close(fd); |
764 | if (ret) { | |
765 | log_log(log, op, ".add file read failure"); | |
766 | return -1; | |
767 | } | |
768 | log_log(log, op, "loaded .add file"); | |
769 | } | |
770 | else | |
771 | log_log(log, op, "missing .add file!"); | |
772 | } | |
773 | ||
774 | /* recover the interrupted operation */ | |
775 | switch (op) { | |
776 | case APPEND_OP: | |
777 | ret = log_append(log, data, len); | |
778 | break; | |
779 | case COMPRESS_OP: | |
780 | ret = log_compress(log, data, len); | |
781 | break; | |
782 | case REPLACE_OP: | |
783 | ret = log_replace(log); | |
784 | } | |
785 | ||
786 | /* log status */ | |
787 | log_log(log, op, ret ? "failure" : "complete"); | |
788 | ||
789 | /* clean up */ | |
790 | if (data != NULL) | |
791 | free(data); | |
792 | return ret; | |
793 | } | |
794 | ||
795 | /* Close the foo.gz file (if open) and release the lock. */ | |
796 | local void log_close(struct log *log) | |
797 | { | |
798 | if (log->fd >= 0) | |
799 | close(log->fd); | |
800 | log->fd = -1; | |
801 | log_unlock(log); | |
802 | } | |
803 | ||
804 | /* Open foo.gz, verify the header, and load the extra field contents, after | |
805 | first creating the foo.lock file to gain exclusive access to the foo.* | |
806 | files. If foo.gz does not exist or is empty, then write the initial header, | |
807 | extra, and body content of an empty foo.gz log file. If there is an error | |
808 | creating the lock file due to access restrictions, or an error reading or | |
809 | writing the foo.gz file, or if the foo.gz file is not a proper log file for | |
810 | this object (e.g. not a gzip file or does not contain the expected extra | |
811 | field), then return true. If there is an error, the lock is released. | |
812 | Otherwise, the lock is left in place. */ | |
813 | local int log_open(struct log *log) | |
814 | { | |
815 | int op; | |
816 | ||
817 | /* release open file resource if left over -- can occur if lock lost | |
818 | between gzlog_open() and gzlog_write() */ | |
819 | if (log->fd >= 0) | |
820 | close(log->fd); | |
821 | log->fd = -1; | |
822 | ||
823 | /* negotiate exclusive access */ | |
824 | if (log_lock(log) < 0) | |
825 | return -1; | |
826 | ||
827 | /* open the log file, foo.gz */ | |
828 | strcpy(log->end, ".gz"); | |
829 | log->fd = open(log->path, O_RDWR | O_CREAT, 0644); | |
830 | if (log->fd < 0) { | |
831 | log_close(log); | |
832 | return -1; | |
833 | } | |
834 | ||
835 | /* if new, initialize foo.gz with an empty log, delete old dictionary */ | |
836 | if (lseek(log->fd, 0, SEEK_END) == 0) { | |
837 | if (write(log->fd, log_gzhead, HEAD) != HEAD || | |
838 | write(log->fd, log_gzext, EXTRA) != EXTRA || | |
839 | write(log->fd, log_gzbody, BODY) != BODY) { | |
840 | log_close(log); | |
841 | return -1; | |
842 | } | |
843 | strcpy(log->end, ".dict"); | |
844 | unlink(log->path); | |
845 | } | |
846 | ||
847 | /* verify log file and load extra field information */ | |
848 | if ((op = log_head(log)) < 0) { | |
849 | log_close(log); | |
850 | return -1; | |
851 | } | |
852 | ||
853 | /* check for interrupted process and if so, recover */ | |
854 | if (op != NO_OP && log_recover(log, op)) { | |
855 | log_close(log); | |
856 | return -1; | |
857 | } | |
858 | ||
859 | /* touch the lock file to prevent another process from grabbing it */ | |
860 | log_touch(log); | |
861 | return 0; | |
862 | } | |
863 | ||
864 | /* See gzlog.h for the description of the external methods below */ | |
865 | gzlog *gzlog_open(char *path) | |
866 | { | |
867 | size_t n; | |
868 | struct log *log; | |
869 | ||
870 | /* check arguments */ | |
871 | if (path == NULL || *path == 0) | |
872 | return NULL; | |
873 | ||
874 | /* allocate and initialize log structure */ | |
875 | log = malloc(sizeof(struct log)); | |
876 | if (log == NULL) | |
877 | return NULL; | |
878 | strcpy(log->id, LOGID); | |
879 | log->fd = -1; | |
880 | ||
881 | /* save path and end of path for name construction */ | |
882 | n = strlen(path); | |
883 | log->path = malloc(n + 9); /* allow for ".repairs" */ | |
884 | if (log->path == NULL) { | |
885 | free(log); | |
886 | return NULL; | |
887 | } | |
888 | strcpy(log->path, path); | |
889 | log->end = log->path + n; | |
890 | ||
891 | /* gain exclusive access and verify log file -- may perform a | |
892 | recovery operation if needed */ | |
893 | if (log_open(log)) { | |
894 | free(log->path); | |
895 | free(log); | |
896 | return NULL; | |
897 | } | |
898 | ||
899 | /* return pointer to log structure */ | |
900 | return log; | |
901 | } | |
902 | ||
903 | /* gzlog_compress() return values: | |
904 | 0: all good | |
905 | -1: file i/o error (usually access issue) | |
906 | -2: memory allocation failure | |
907 | -3: invalid log pointer argument */ | |
908 | int gzlog_compress(gzlog *logd) | |
909 | { | |
910 | int fd, ret; | |
911 | uint block; | |
912 | size_t len, next; | |
913 | unsigned char *data, buf[5]; | |
914 | struct log *log = logd; | |
915 | ||
916 | /* check arguments */ | |
da09a436 | 917 | if (log == NULL || strcmp(log->id, LOGID)) |
5ca28f79 L |
918 | return -3; |
919 | ||
920 | /* see if we lost the lock -- if so get it again and reload the extra | |
921 | field information (it probably changed), recover last operation if | |
922 | necessary */ | |
923 | if (log_check(log) && log_open(log)) | |
924 | return -1; | |
925 | ||
926 | /* create space for uncompressed data */ | |
927 | len = ((size_t)(log->last - log->first) & ~(((size_t)1 << 10) - 1)) + | |
928 | log->stored; | |
929 | if ((data = malloc(len)) == NULL) | |
930 | return -2; | |
931 | ||
932 | /* do statement here is just a cheap trick for error handling */ | |
933 | do { | |
934 | /* read in the uncompressed data */ | |
935 | if (lseek(log->fd, log->first - 1, SEEK_SET) < 0) | |
936 | break; | |
937 | next = 0; | |
938 | while (next < len) { | |
939 | if (read(log->fd, buf, 5) != 5) | |
940 | break; | |
941 | block = PULL2(buf + 1); | |
942 | if (next + block > len || | |
943 | read(log->fd, (char *)data + next, block) != block) | |
944 | break; | |
945 | next += block; | |
946 | } | |
947 | if (lseek(log->fd, 0, SEEK_CUR) != log->last + 4 + log->stored) | |
948 | break; | |
949 | log_touch(log); | |
950 | ||
951 | /* write the uncompressed data to the .add file */ | |
952 | strcpy(log->end, ".add"); | |
953 | fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644); | |
954 | if (fd < 0) | |
955 | break; | |
da09a436 | 956 | ret = (size_t)write(fd, data, len) != len; |
5ca28f79 L |
957 | if (ret | close(fd)) |
958 | break; | |
959 | log_touch(log); | |
960 | ||
961 | /* write the dictionary for the next compress to the .temp file */ | |
962 | strcpy(log->end, ".temp"); | |
963 | fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644); | |
964 | if (fd < 0) | |
965 | break; | |
966 | next = DICT > len ? len : DICT; | |
da09a436 | 967 | ret = (size_t)write(fd, (char *)data + len - next, next) != next; |
5ca28f79 L |
968 | if (ret | close(fd)) |
969 | break; | |
970 | log_touch(log); | |
971 | ||
972 | /* roll back to compressed data, mark the compress in progress */ | |
973 | log->last = log->first; | |
974 | log->stored = 0; | |
975 | if (log_mark(log, COMPRESS_OP)) | |
976 | break; | |
977 | BAIL(7); | |
978 | ||
979 | /* compress and append the data (clears mark) */ | |
980 | ret = log_compress(log, data, len); | |
981 | free(data); | |
982 | return ret; | |
983 | } while (0); | |
984 | ||
985 | /* broke out of do above on i/o error */ | |
986 | free(data); | |
987 | return -1; | |
988 | } | |
989 | ||
990 | /* gzlog_write() return values: | |
991 | 0: all good | |
992 | -1: file i/o error (usually access issue) | |
993 | -2: memory allocation failure | |
994 | -3: invalid log pointer argument */ | |
995 | int gzlog_write(gzlog *logd, void *data, size_t len) | |
996 | { | |
997 | int fd, ret; | |
998 | struct log *log = logd; | |
999 | ||
1000 | /* check arguments */ | |
da09a436 | 1001 | if (log == NULL || strcmp(log->id, LOGID)) |
5ca28f79 | 1002 | return -3; |
da09a436 | 1003 | if (data == NULL || len <= 0) |
5ca28f79 L |
1004 | return 0; |
1005 | ||
1006 | /* see if we lost the lock -- if so get it again and reload the extra | |
1007 | field information (it probably changed), recover last operation if | |
1008 | necessary */ | |
1009 | if (log_check(log) && log_open(log)) | |
1010 | return -1; | |
1011 | ||
1012 | /* create and write .add file */ | |
1013 | strcpy(log->end, ".add"); | |
1014 | fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644); | |
1015 | if (fd < 0) | |
1016 | return -1; | |
da09a436 | 1017 | ret = (size_t)write(fd, data, len) != len; |
5ca28f79 L |
1018 | if (ret | close(fd)) |
1019 | return -1; | |
1020 | log_touch(log); | |
1021 | ||
1022 | /* mark log file with append in progress */ | |
1023 | if (log_mark(log, APPEND_OP)) | |
1024 | return -1; | |
1025 | BAIL(8); | |
1026 | ||
1027 | /* append data (clears mark) */ | |
1028 | if (log_append(log, data, len)) | |
1029 | return -1; | |
1030 | ||
1031 | /* check to see if it's time to compress -- if not, then done */ | |
1032 | if (((log->last - log->first) >> 10) + (log->stored >> 10) < TRIGGER) | |
1033 | return 0; | |
1034 | ||
1035 | /* time to compress */ | |
1036 | return gzlog_compress(log); | |
1037 | } | |
1038 | ||
1039 | /* gzlog_close() return values: | |
1040 | 0: ok | |
1041 | -3: invalid log pointer argument */ | |
1042 | int gzlog_close(gzlog *logd) | |
1043 | { | |
1044 | struct log *log = logd; | |
1045 | ||
1046 | /* check arguments */ | |
1047 | if (log == NULL || strcmp(log->id, LOGID)) | |
1048 | return -3; | |
1049 | ||
1050 | /* close the log file and release the lock */ | |
1051 | log_close(log); | |
1052 | ||
1053 | /* free structure and return */ | |
1054 | if (log->path != NULL) | |
1055 | free(log->path); | |
1056 | strcpy(log->id, "bad"); | |
1057 | free(log); | |
1058 | return 0; | |
1059 | } |