1/*
2 * Copyright (c) 2017 rxi
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a copy
5 * of this software and associated documentation files (the "Software"), to
6 * deal in the Software without restriction, including without limitation the
7 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
8 * sell copies of the Software, and to permit persons to whom the Software is
9 * furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice shall be included in
12 * all copies or substantial portions of the Software.
13 *
14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
17 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
19 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
20 * IN THE SOFTWARE.
21 */
22
23#include <stdio.h>
24#include <stdlib.h>
25#include <stddef.h>
26#include <string.h>
27
28#include "microtar.h"
29
30typedef struct {
31 char name[100];
32 char mode[8];
33 char owner[8];
34 char group[8];
35 char size[12];
36 char mtime[12];
37 char checksum[8];
38 char type;
39 char linkname[100];
40 char _padding[255];
41} mtar_raw_header_t;
42
43
44static unsigned round_up(unsigned n, unsigned incr) {
45 return n + (incr - n % incr) % incr;
46}
47
48
49static unsigned checksum(const mtar_raw_header_t* rh) {
50 unsigned i;
51 unsigned char *p = (unsigned char*) rh;
52 unsigned res = 256;
53 for (i = 0; i < offsetof(mtar_raw_header_t, checksum); i++) {
54 res += p[i];
55 }
56 for (i = offsetof(mtar_raw_header_t, type); i < sizeof(*rh); i++) {
57 res += p[i];
58 }
59 return res;
60}
61
62
63static int tread(mtar_t *tar, void *data, unsigned size) {
64 int err = tar->read(tar, data, size);
65 tar->pos += size;
66 return err;
67}
68
69
70static int twrite(mtar_t *tar, const void *data, unsigned size) {
71 int err = tar->write(tar, data, size);
72 tar->pos += size;
73 return err;
74}
75
76
77static int write_null_bytes(mtar_t *tar, int n) {
78 int i, err;
79 char nul = '\0';
80 for (i = 0; i < n; i++) {
81 err = twrite(tar, &nul, 1);
82 if (err) {
83 return err;
84 }
85 }
86 return MTAR_ESUCCESS;
87}
88
89
90static int raw_to_header(mtar_header_t *h, const mtar_raw_header_t *rh) {
91 unsigned chksum1, chksum2;
92
93 /* If the checksum starts with a null byte we assume the record is NULL */
94 if (*rh->checksum == '\0') {
95 return MTAR_ENULLRECORD;
96 }
97
98 /* Build and compare checksum */
99 chksum1 = checksum(rh);
100 sscanf(rh->checksum, "%o", &chksum2);
101 if (chksum1 != chksum2) {
102 return MTAR_EBADCHKSUM;
103 }
104
105 /* Load raw header into header */
106 sscanf(rh->mode, "%o", &h->mode);
107 sscanf(rh->owner, "%o", &h->owner);
108 sscanf(rh->size, "%o", &h->size);
109 sscanf(rh->mtime, "%o", &h->mtime);
110 h->type = rh->type;
111 strcpy(h->name, rh->name);
112 strcpy(h->linkname, rh->linkname);
113
114 return MTAR_ESUCCESS;
115}
116
117
118static int header_to_raw(mtar_raw_header_t *rh, const mtar_header_t *h) {
119 unsigned chksum;
120
121 /* Load header into raw header */
122 memset(rh, 0, sizeof(*rh));
123 sprintf(rh->mode, "%o", h->mode);
124 sprintf(rh->owner, "%o", h->owner);
125 sprintf(rh->size, "%o", h->size);
126 sprintf(rh->mtime, "%o", h->mtime);
127 rh->type = h->type ? h->type : MTAR_TREG;
128 strcpy(rh->name, h->name);
129 strcpy(rh->linkname, h->linkname);
130
131 /* Calculate and write checksum */
132 chksum = checksum(rh);
133 sprintf(rh->checksum, "%06o", chksum);
134 rh->checksum[7] = ' ';
135
136 return MTAR_ESUCCESS;
137}
138
139
140const char* mtar_strerror(int err) {
141 switch (err) {
142 case MTAR_ESUCCESS : return "success";
143 case MTAR_EFAILURE : return "failure";
144 case MTAR_EOPENFAIL : return "could not open";
145 case MTAR_EREADFAIL : return "could not read";
146 case MTAR_EWRITEFAIL : return "could not write";
147 case MTAR_ESEEKFAIL : return "could not seek";
148 case MTAR_EBADCHKSUM : return "bad checksum";
149 case MTAR_ENULLRECORD : return "null record";
150 case MTAR_ENOTFOUND : return "file not found";
151 }
152 return "unknown error";
153}
154
155
156static int file_write(mtar_t *tar, const void *data, unsigned size) {
157 unsigned res = fwrite(data, 1, size, tar->stream);
158 return (res == size) ? MTAR_ESUCCESS : MTAR_EWRITEFAIL;
159}
160
161static int file_read(mtar_t *tar, void *data, unsigned size) {
162 unsigned res = fread(data, 1, size, tar->stream);
163 return (res == size) ? MTAR_ESUCCESS : MTAR_EREADFAIL;
164}
165
166static int file_seek(mtar_t *tar, unsigned offset) {
167 int res = fseek(tar->stream, offset, SEEK_SET);
168 return (res == 0) ? MTAR_ESUCCESS : MTAR_ESEEKFAIL;
169}
170
171static int file_close(mtar_t *tar) {
172 fclose(tar->stream);
173 return MTAR_ESUCCESS;
174}
175
176
177int mtar_open(mtar_t *tar, const char *filename, const char *mode) {
178 int err;
179 mtar_header_t h;
180
181 /* Init tar struct and functions */
182 memset(tar, 0, sizeof(*tar));
183 tar->write = file_write;
184 tar->read = file_read;
185 tar->seek = file_seek;
186 tar->close = file_close;
187
188 /* Assure mode is always binary */
189 if ( strchr(mode, 'r') ) mode = "rb";
190 if ( strchr(mode, 'w') ) mode = "wb";
191 if ( strchr(mode, 'a') ) mode = "ab";
192 /* Open file */
193 tar->stream = fopen(filename, mode);
194 if (!tar->stream) {
195 return MTAR_EOPENFAIL;
196 }
197 /* Read first header to check it is valid if mode is `r` */
198 if (*mode == 'r') {
199 err = mtar_read_header(tar, &h);
200 if (err != MTAR_ESUCCESS) {
201 mtar_close(tar);
202 return err;
203 }
204 }
205
206 /* Return ok */
207 return MTAR_ESUCCESS;
208}
209
210
211int mtar_close(mtar_t *tar) {
212 return tar->close(tar);
213}
214
215
216int mtar_seek(mtar_t *tar, unsigned pos) {
217 int err = tar->seek(tar, pos);
218 tar->pos = pos;
219 return err;
220}
221
222
223int mtar_rewind(mtar_t *tar) {
224 tar->remaining_data = 0;
225 tar->last_header = 0;
226 return mtar_seek(tar, 0);
227}
228
229
230int mtar_next(mtar_t *tar) {
231 int err, n;
232 mtar_header_t h;
233 /* Load header */
234 err = mtar_read_header(tar, &h);
235 if (err) {
236 return err;
237 }
238 /* Seek to next record */
239 n = round_up(h.size, 512) + sizeof(mtar_raw_header_t);
240 return mtar_seek(tar, tar->pos + n);
241}
242
243
244int mtar_find(mtar_t *tar, const char *name, mtar_header_t *h) {
245 int err;
246 mtar_header_t header;
247 /* Start at beginning */
248 err = mtar_rewind(tar);
249 if (err) {
250 return err;
251 }
252 /* Iterate all files until we hit an error or find the file */
253 while ( (err = mtar_read_header(tar, &header)) == MTAR_ESUCCESS ) {
254 if ( !strcmp(header.name, name) ) {
255 if (h) {
256 *h = header;
257 }
258 return MTAR_ESUCCESS;
259 }
260 mtar_next(tar);
261 }
262 /* Return error */
263 if (err == MTAR_ENULLRECORD) {
264 err = MTAR_ENOTFOUND;
265 }
266 return err;
267}
268
269
270int mtar_read_header(mtar_t *tar, mtar_header_t *h) {
271 int err;
272 mtar_raw_header_t rh;
273 /* Save header position */
274 tar->last_header = tar->pos;
275 /* Read raw header */
276 err = tread(tar, &rh, sizeof(rh));
277 if (err) {
278 return err;
279 }
280 /* Seek back to start of header */
281 err = mtar_seek(tar, tar->last_header);
282 if (err) {
283 return err;
284 }
285 /* Load raw header into header struct and return */
286 return raw_to_header(h, &rh);
287}
288
289
290int mtar_read_data(mtar_t *tar, void *ptr, unsigned size) {
291 int err;
292 /* If we have no remaining data then this is the first read, we get the size,
293 * set the remaining data and seek to the beginning of the data */
294 if (tar->remaining_data == 0) {
295 mtar_header_t h;
296 /* Read header */
297 err = mtar_read_header(tar, &h);
298 if (err) {
299 return err;
300 }
301 /* Seek past header and init remaining data */
302 err = mtar_seek(tar, tar->pos + sizeof(mtar_raw_header_t));
303 if (err) {
304 return err;
305 }
306 tar->remaining_data = h.size;
307 }
308 /* Read data */
309 err = tread(tar, ptr, size);
310 if (err) {
311 return err;
312 }
313 tar->remaining_data -= size;
314 /* If there is no remaining data we've finished reading and seek back to the
315 * header */
316 if (tar->remaining_data == 0) {
317 return mtar_seek(tar, tar->last_header);
318 }
319 return MTAR_ESUCCESS;
320}
321
322
323int mtar_write_header(mtar_t *tar, const mtar_header_t *h) {
324 mtar_raw_header_t rh;
325 /* Build raw header and write */
326 header_to_raw(&rh, h);
327 tar->remaining_data = h->size;
328 return twrite(tar, &rh, sizeof(rh));
329}
330
331
332int mtar_write_file_header(mtar_t *tar, const char *name, unsigned size) {
333 mtar_header_t h;
334 /* Build header */
335 memset(&h, 0, sizeof(h));
336 strcpy(h.name, name);
337 h.size = size;
338 h.type = MTAR_TREG;
339 h.mode = 0664;
340 /* Write header */
341 return mtar_write_header(tar, &h);
342}
343
344
345int mtar_write_dir_header(mtar_t *tar, const char *name) {
346 mtar_header_t h;
347 /* Build header */
348 memset(&h, 0, sizeof(h));
349 strcpy(h.name, name);
350 h.type = MTAR_TDIR;
351 h.mode = 0775;
352 /* Write header */
353 return mtar_write_header(tar, &h);
354}
355
356
357int mtar_write_data(mtar_t *tar, const void *data, unsigned size) {
358 int err;
359 /* Write data */
360 err = twrite(tar, data, size);
361 if (err) {
362 return err;
363 }
364 tar->remaining_data -= size;
365 /* Write padding if we've written all the data for this file */
366 if (tar->remaining_data == 0) {
367 return write_null_bytes(tar, round_up(tar->pos, 512) - tar->pos);
368 }
369 return MTAR_ESUCCESS;
370}
371
372
373int mtar_finalize(mtar_t *tar) {
374 /* Write two NULL records */
375 return write_null_bytes(tar, sizeof(mtar_raw_header_t) * 2);
376}