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1 | /* gzappend -- command to append to a gzip file |
2 | ||
3 | Copyright (C) 2003 Mark Adler, all rights reserved | |
4 | version 1.1, 4 Nov 2003 | |
5 | ||
6 | This software is provided 'as-is', without any express or implied | |
7 | warranty. In no event will the author be held liable for any damages | |
8 | arising from the use of this software. | |
9 | ||
10 | Permission is granted to anyone to use this software for any purpose, | |
11 | including commercial applications, and to alter it and redistribute it | |
12 | freely, subject to the following restrictions: | |
13 | ||
14 | 1. The origin of this software must not be misrepresented; you must not | |
15 | claim that you wrote the original software. If you use this software | |
16 | in a product, an acknowledgment in the product documentation would be | |
17 | appreciated but is not required. | |
18 | 2. Altered source versions must be plainly marked as such, and must not be | |
19 | misrepresented as being the original software. | |
20 | 3. This notice may not be removed or altered from any source distribution. | |
21 | ||
22 | Mark Adler madler@alumni.caltech.edu | |
23 | */ | |
24 | ||
25 | /* | |
26 | * Change history: | |
27 | * | |
28 | * 1.0 19 Oct 2003 - First version | |
29 | * 1.1 4 Nov 2003 - Expand and clarify some comments and notes | |
30 | * - Add version and copyright to help | |
31 | * - Send help to stdout instead of stderr | |
32 | * - Add some preemptive typecasts | |
33 | * - Add L to constants in lseek() calls | |
34 | * - Remove some debugging information in error messages | |
35 | * - Use new data_type definition for zlib 1.2.1 | |
36 | * - Simplfy and unify file operations | |
37 | * - Finish off gzip file in gztack() | |
38 | * - Use deflatePrime() instead of adding empty blocks | |
39 | * - Keep gzip file clean on appended file read errors | |
40 | * - Use in-place rotate instead of auxiliary buffer | |
41 | * (Why you ask? Because it was fun to write!) | |
42 | */ | |
43 | ||
44 | /* | |
45 | gzappend takes a gzip file and appends to it, compressing files from the | |
46 | command line or data from stdin. The gzip file is written to directly, to | |
47 | avoid copying that file, in case it's large. Note that this results in the | |
48 | unfriendly behavior that if gzappend fails, the gzip file is corrupted. | |
49 | ||
50 | This program was written to illustrate the use of the new Z_BLOCK option of | |
51 | zlib 1.2.x's inflate() function. This option returns from inflate() at each | |
52 | block boundary to facilitate locating and modifying the last block bit at | |
53 | the start of the final deflate block. Also whether using Z_BLOCK or not, | |
54 | another required feature of zlib 1.2.x is that inflate() now provides the | |
55 | number of unusued bits in the last input byte used. gzappend will not work | |
56 | with versions of zlib earlier than 1.2.1. | |
57 | ||
58 | gzappend first decompresses the gzip file internally, discarding all but | |
59 | the last 32K of uncompressed data, and noting the location of the last block | |
60 | bit and the number of unused bits in the last byte of the compressed data. | |
61 | The gzip trailer containing the CRC-32 and length of the uncompressed data | |
62 | is verified. This trailer will be later overwritten. | |
63 | ||
64 | Then the last block bit is cleared by seeking back in the file and rewriting | |
65 | the byte that contains it. Seeking forward, the last byte of the compressed | |
66 | data is saved along with the number of unused bits to initialize deflate. | |
67 | ||
68 | A deflate process is initialized, using the last 32K of the uncompressed | |
69 | data from the gzip file to initialize the dictionary. If the total | |
70 | uncompressed data was less than 32K, then all of it is used to initialize | |
71 | the dictionary. The deflate output bit buffer is also initialized with the | |
72 | last bits from the original deflate stream. From here on, the data to | |
73 | append is simply compressed using deflate, and written to the gzip file. | |
74 | When that is complete, the new CRC-32 and uncompressed length are written | |
75 | as the trailer of the gzip file. | |
76 | */ | |
77 | ||
78 | #include <stdio.h> | |
79 | #include <stdlib.h> | |
80 | #include <string.h> | |
81 | #include <fcntl.h> | |
82 | #include <unistd.h> | |
83 | #include "zlib.h" | |
84 | ||
85 | #define local static | |
86 | #define LGCHUNK 14 | |
87 | #define CHUNK (1U << LGCHUNK) | |
88 | #define DSIZE 32768U | |
89 | ||
90 | /* print an error message and terminate with extreme prejudice */ | |
91 | local void bye(char *msg1, char *msg2) | |
92 | { | |
93 | fprintf(stderr, "gzappend error: %s%s\n", msg1, msg2); | |
94 | exit(1); | |
95 | } | |
96 | ||
97 | /* return the greatest common divisor of a and b using Euclid's algorithm, | |
98 | modified to be fast when one argument much greater than the other, and | |
99 | coded to avoid unnecessary swapping */ | |
100 | local unsigned gcd(unsigned a, unsigned b) | |
101 | { | |
102 | unsigned c; | |
103 | ||
104 | while (a && b) | |
105 | if (a > b) { | |
106 | c = b; | |
107 | while (a - c >= c) | |
108 | c <<= 1; | |
109 | a -= c; | |
110 | } | |
111 | else { | |
112 | c = a; | |
113 | while (b - c >= c) | |
114 | c <<= 1; | |
115 | b -= c; | |
116 | } | |
117 | return a + b; | |
118 | } | |
119 | ||
120 | /* rotate list[0..len-1] left by rot positions, in place */ | |
121 | local void rotate(unsigned char *list, unsigned len, unsigned rot) | |
122 | { | |
123 | unsigned char tmp; | |
124 | unsigned cycles; | |
125 | unsigned char *start, *last, *to, *from; | |
126 | ||
127 | /* normalize rot and handle degenerate cases */ | |
128 | if (len < 2) return; | |
129 | if (rot >= len) rot %= len; | |
130 | if (rot == 0) return; | |
131 | ||
132 | /* pointer to last entry in list */ | |
133 | last = list + (len - 1); | |
134 | ||
135 | /* do simple left shift by one */ | |
136 | if (rot == 1) { | |
137 | tmp = *list; | |
138 | memcpy(list, list + 1, len - 1); | |
139 | *last = tmp; | |
140 | return; | |
141 | } | |
142 | ||
143 | /* do simple right shift by one */ | |
144 | if (rot == len - 1) { | |
145 | tmp = *last; | |
146 | memmove(list + 1, list, len - 1); | |
147 | *list = tmp; | |
148 | return; | |
149 | } | |
150 | ||
151 | /* otherwise do rotate as a set of cycles in place */ | |
152 | cycles = gcd(len, rot); /* number of cycles */ | |
153 | do { | |
154 | start = from = list + cycles; /* start index is arbitrary */ | |
155 | tmp = *from; /* save entry to be overwritten */ | |
156 | for (;;) { | |
157 | to = from; /* next step in cycle */ | |
158 | from += rot; /* go right rot positions */ | |
159 | if (from > last) from -= len; /* (pointer better not wrap) */ | |
160 | if (from == start) break; /* all but one shifted */ | |
161 | *to = *from; /* shift left */ | |
162 | } | |
163 | *to = tmp; /* complete the circle */ | |
164 | } while (--cycles); | |
165 | } | |
166 | ||
167 | /* structure for gzip file read operations */ | |
168 | typedef struct { | |
169 | int fd; /* file descriptor */ | |
170 | int size; /* 1 << size is bytes in buf */ | |
171 | unsigned left; /* bytes available at next */ | |
172 | unsigned char *buf; /* buffer */ | |
173 | unsigned char *next; /* next byte in buffer */ | |
174 | char *name; /* file name for error messages */ | |
175 | } file; | |
176 | ||
177 | /* reload buffer */ | |
178 | local int readin(file *in) | |
179 | { | |
180 | int len; | |
181 | ||
182 | len = read(in->fd, in->buf, 1 << in->size); | |
183 | if (len == -1) bye("error reading ", in->name); | |
184 | in->left = (unsigned)len; | |
185 | in->next = in->buf; | |
186 | return len; | |
187 | } | |
188 | ||
189 | /* read from file in, exit if end-of-file */ | |
190 | local int readmore(file *in) | |
191 | { | |
192 | if (readin(in) == 0) bye("unexpected end of ", in->name); | |
193 | return 0; | |
194 | } | |
195 | ||
196 | #define read1(in) (in->left == 0 ? readmore(in) : 0, \ | |
197 | in->left--, *(in->next)++) | |
198 | ||
199 | /* skip over n bytes of in */ | |
200 | local void skip(file *in, unsigned n) | |
201 | { | |
202 | unsigned bypass; | |
203 | ||
204 | if (n > in->left) { | |
205 | n -= in->left; | |
206 | bypass = n & ~((1U << in->size) - 1); | |
207 | if (bypass) { | |
208 | if (lseek(in->fd, (off_t)bypass, SEEK_CUR) == -1) | |
209 | bye("seeking ", in->name); | |
210 | n -= bypass; | |
211 | } | |
212 | readmore(in); | |
213 | if (n > in->left) | |
214 | bye("unexpected end of ", in->name); | |
215 | } | |
216 | in->left -= n; | |
217 | in->next += n; | |
218 | } | |
219 | ||
220 | /* read a four-byte unsigned integer, little-endian, from in */ | |
221 | unsigned long read4(file *in) | |
222 | { | |
223 | unsigned long val; | |
224 | ||
225 | val = read1(in); | |
226 | val += (unsigned)read1(in) << 8; | |
227 | val += (unsigned long)read1(in) << 16; | |
228 | val += (unsigned long)read1(in) << 24; | |
229 | return val; | |
230 | } | |
231 | ||
232 | /* skip over gzip header */ | |
233 | local void gzheader(file *in) | |
234 | { | |
235 | int flags; | |
236 | unsigned n; | |
237 | ||
238 | if (read1(in) != 31 || read1(in) != 139) bye(in->name, " not a gzip file"); | |
239 | if (read1(in) != 8) bye("unknown compression method in", in->name); | |
240 | flags = read1(in); | |
241 | if (flags & 0xe0) bye("unknown header flags set in", in->name); | |
242 | skip(in, 6); | |
243 | if (flags & 4) { | |
244 | n = read1(in); | |
245 | n += (unsigned)(read1(in)) << 8; | |
246 | skip(in, n); | |
247 | } | |
248 | if (flags & 8) while (read1(in) != 0) ; | |
249 | if (flags & 16) while (read1(in) != 0) ; | |
250 | if (flags & 2) skip(in, 2); | |
251 | } | |
252 | ||
253 | /* decompress gzip file "name", return strm with a deflate stream ready to | |
254 | continue compression of the data in the gzip file, and return a file | |
255 | descriptor pointing to where to write the compressed data -- the deflate | |
256 | stream is initialized to compress using level "level" */ | |
257 | local int gzscan(char *name, z_stream *strm, int level) | |
258 | { | |
259 | int ret, lastbit, left, full; | |
260 | unsigned have; | |
261 | unsigned long crc, tot; | |
262 | unsigned char *window; | |
263 | off_t lastoff, end; | |
264 | file gz; | |
265 | ||
266 | /* open gzip file */ | |
267 | gz.name = name; | |
268 | gz.fd = open(name, O_RDWR, 0); | |
269 | if (gz.fd == -1) bye("cannot open ", name); | |
270 | gz.buf = malloc(CHUNK); | |
271 | if (gz.buf == NULL) bye("out of memory", ""); | |
272 | gz.size = LGCHUNK; | |
273 | gz.left = 0; | |
274 | ||
275 | /* skip gzip header */ | |
276 | gzheader(&gz); | |
277 | ||
278 | /* prepare to decompress */ | |
279 | window = malloc(DSIZE); | |
280 | if (window == NULL) bye("out of memory", ""); | |
281 | strm->zalloc = Z_NULL; | |
282 | strm->zfree = Z_NULL; | |
283 | strm->opaque = Z_NULL; | |
284 | ret = inflateInit2(strm, -15); | |
285 | if (ret != Z_OK) bye("out of memory", " or library mismatch"); | |
286 | ||
287 | /* decompress the deflate stream, saving append information */ | |
288 | lastbit = 0; | |
289 | lastoff = lseek(gz.fd, 0L, SEEK_CUR) - gz.left; | |
290 | left = 0; | |
291 | strm->avail_in = gz.left; | |
292 | strm->next_in = gz.next; | |
293 | crc = crc32(0L, Z_NULL, 0); | |
294 | have = full = 0; | |
295 | do { | |
296 | /* if needed, get more input */ | |
297 | if (strm->avail_in == 0) { | |
298 | readmore(&gz); | |
299 | strm->avail_in = gz.left; | |
300 | strm->next_in = gz.next; | |
301 | } | |
302 | ||
303 | /* set up output to next available section of sliding window */ | |
304 | strm->avail_out = DSIZE - have; | |
305 | strm->next_out = window + have; | |
306 | ||
307 | /* inflate and check for errors */ | |
308 | ret = inflate(strm, Z_BLOCK); | |
309 | if (ret == Z_STREAM_ERROR) bye("internal stream error!", ""); | |
310 | if (ret == Z_MEM_ERROR) bye("out of memory", ""); | |
311 | if (ret == Z_DATA_ERROR) | |
312 | bye("invalid compressed data--format violated in", name); | |
313 | ||
314 | /* update crc and sliding window pointer */ | |
315 | crc = crc32(crc, window + have, DSIZE - have - strm->avail_out); | |
316 | if (strm->avail_out) | |
317 | have = DSIZE - strm->avail_out; | |
318 | else { | |
319 | have = 0; | |
320 | full = 1; | |
321 | } | |
322 | ||
323 | /* process end of block */ | |
324 | if (strm->data_type & 128) { | |
325 | if (strm->data_type & 64) | |
326 | left = strm->data_type & 0x1f; | |
327 | else { | |
328 | lastbit = strm->data_type & 0x1f; | |
329 | lastoff = lseek(gz.fd, 0L, SEEK_CUR) - strm->avail_in; | |
330 | } | |
331 | } | |
332 | } while (ret != Z_STREAM_END); | |
333 | inflateEnd(strm); | |
334 | gz.left = strm->avail_in; | |
335 | gz.next = strm->next_in; | |
336 | ||
337 | /* save the location of the end of the compressed data */ | |
338 | end = lseek(gz.fd, 0L, SEEK_CUR) - gz.left; | |
339 | ||
340 | /* check gzip trailer and save total for deflate */ | |
341 | if (crc != read4(&gz)) | |
342 | bye("invalid compressed data--crc mismatch in ", name); | |
343 | tot = strm->total_out; | |
344 | if ((tot & 0xffffffffUL) != read4(&gz)) | |
345 | bye("invalid compressed data--length mismatch in", name); | |
346 | ||
347 | /* if not at end of file, warn */ | |
348 | if (gz.left || readin(&gz)) | |
349 | fprintf(stderr, | |
350 | "gzappend warning: junk at end of gzip file overwritten\n"); | |
351 | ||
352 | /* clear last block bit */ | |
353 | lseek(gz.fd, lastoff - (lastbit != 0), SEEK_SET); | |
354 | if (read(gz.fd, gz.buf, 1) != 1) bye("reading after seek on ", name); | |
355 | *gz.buf = (unsigned char)(*gz.buf ^ (1 << ((8 - lastbit) & 7))); | |
356 | lseek(gz.fd, -1L, SEEK_CUR); | |
357 | if (write(gz.fd, gz.buf, 1) != 1) bye("writing after seek to ", name); | |
358 | ||
359 | /* if window wrapped, build dictionary from window by rotating */ | |
360 | if (full) { | |
361 | rotate(window, DSIZE, have); | |
362 | have = DSIZE; | |
363 | } | |
364 | ||
365 | /* set up deflate stream with window, crc, total_in, and leftover bits */ | |
366 | ret = deflateInit2(strm, level, Z_DEFLATED, -15, 8, Z_DEFAULT_STRATEGY); | |
367 | if (ret != Z_OK) bye("out of memory", ""); | |
368 | deflateSetDictionary(strm, window, have); | |
369 | strm->adler = crc; | |
370 | strm->total_in = tot; | |
371 | if (left) { | |
372 | lseek(gz.fd, --end, SEEK_SET); | |
373 | if (read(gz.fd, gz.buf, 1) != 1) bye("reading after seek on ", name); | |
374 | deflatePrime(strm, 8 - left, *gz.buf); | |
375 | } | |
376 | lseek(gz.fd, end, SEEK_SET); | |
377 | ||
378 | /* clean up and return */ | |
379 | free(window); | |
380 | free(gz.buf); | |
381 | return gz.fd; | |
382 | } | |
383 | ||
384 | /* append file "name" to gzip file gd using deflate stream strm -- if last | |
385 | is true, then finish off the deflate stream at the end */ | |
386 | local void gztack(char *name, int gd, z_stream *strm, int last) | |
387 | { | |
388 | int fd, len, ret; | |
389 | unsigned left; | |
390 | unsigned char *in, *out; | |
391 | ||
392 | /* open file to compress and append */ | |
393 | fd = 0; | |
394 | if (name != NULL) { | |
395 | fd = open(name, O_RDONLY, 0); | |
396 | if (fd == -1) | |
397 | fprintf(stderr, "gzappend warning: %s not found, skipping ...\n", | |
398 | name); | |
399 | } | |
400 | ||
401 | /* allocate buffers */ | |
402 | in = fd == -1 ? NULL : malloc(CHUNK); | |
403 | out = malloc(CHUNK); | |
404 | if (out == NULL) bye("out of memory", ""); | |
405 | ||
406 | /* compress input file and append to gzip file */ | |
407 | do { | |
408 | /* get more input */ | |
409 | len = fd == -1 ? 0 : read(fd, in, CHUNK); | |
410 | if (len == -1) { | |
411 | fprintf(stderr, | |
412 | "gzappend warning: error reading %s, skipping rest ...\n", | |
413 | name); | |
414 | len = 0; | |
415 | } | |
416 | strm->avail_in = (unsigned)len; | |
417 | strm->next_in = in; | |
418 | if (len) strm->adler = crc32(strm->adler, in, (unsigned)len); | |
419 | ||
420 | /* compress and write all available output */ | |
421 | do { | |
422 | strm->avail_out = CHUNK; | |
423 | strm->next_out = out; | |
424 | ret = deflate(strm, last && len == 0 ? Z_FINISH : Z_NO_FLUSH); | |
425 | left = CHUNK - strm->avail_out; | |
426 | while (left) { | |
427 | len = write(gd, out + CHUNK - strm->avail_out - left, left); | |
428 | if (len == -1) bye("writing gzip file", ""); | |
429 | left -= (unsigned)len; | |
430 | } | |
431 | } while (strm->avail_out == 0 && ret != Z_STREAM_END); | |
432 | } while (len != 0); | |
433 | ||
434 | /* write trailer after last entry */ | |
435 | if (last) { | |
436 | deflateEnd(strm); | |
437 | out[0] = (unsigned char)(strm->adler); | |
438 | out[1] = (unsigned char)(strm->adler >> 8); | |
439 | out[2] = (unsigned char)(strm->adler >> 16); | |
440 | out[3] = (unsigned char)(strm->adler >> 24); | |
441 | out[4] = (unsigned char)(strm->total_in); | |
442 | out[5] = (unsigned char)(strm->total_in >> 8); | |
443 | out[6] = (unsigned char)(strm->total_in >> 16); | |
444 | out[7] = (unsigned char)(strm->total_in >> 24); | |
445 | len = 8; | |
446 | do { | |
447 | ret = write(gd, out + 8 - len, len); | |
448 | if (ret == -1) bye("writing gzip file", ""); | |
449 | len -= ret; | |
450 | } while (len); | |
451 | close(gd); | |
452 | } | |
453 | ||
454 | /* clean up and return */ | |
455 | free(out); | |
456 | if (in != NULL) free(in); | |
457 | if (fd > 0) close(fd); | |
458 | } | |
459 | ||
460 | /* process the compression level option if present, scan the gzip file, and | |
461 | append the specified files, or append the data from stdin if no other file | |
462 | names are provided on the command line -- the gzip file must be writable | |
463 | and seekable */ | |
464 | int main(int argc, char **argv) | |
465 | { | |
466 | int gd, level; | |
467 | z_stream strm; | |
468 | ||
469 | /* ignore command name */ | |
470 | argv++; | |
471 | ||
472 | /* provide usage if no arguments */ | |
473 | if (*argv == NULL) { | |
474 | printf("gzappend 1.1 (4 Nov 2003) Copyright (C) 2003 Mark Adler\n"); | |
475 | printf( | |
476 | "usage: gzappend [-level] file.gz [ addthis [ andthis ... ]]\n"); | |
477 | return 0; | |
478 | } | |
479 | ||
480 | /* set compression level */ | |
481 | level = Z_DEFAULT_COMPRESSION; | |
482 | if (argv[0][0] == '-') { | |
483 | if (argv[0][1] < '0' || argv[0][1] > '9' || argv[0][2] != 0) | |
484 | bye("invalid compression level", ""); | |
485 | level = argv[0][1] - '0'; | |
486 | if (*++argv == NULL) bye("no gzip file name after options", ""); | |
487 | } | |
488 | ||
489 | /* prepare to append to gzip file */ | |
490 | gd = gzscan(*argv++, &strm, level); | |
491 | ||
492 | /* append files on command line, or from stdin if none */ | |
493 | if (*argv == NULL) | |
494 | gztack(NULL, gd, &strm, 1); | |
495 | else | |
496 | do { | |
497 | gztack(*argv, gd, &strm, argv[1] == NULL); | |
498 | } while (*++argv != NULL); | |
499 | return 0; | |
500 | } |