1 /*
2 * fileio.c --- Simple file I/O routines
3 *
4 * Copyright (C) 1997 Theodore Ts'o.
5 *
6 * %Begin-Header%
7 * This file may be redistributed under the terms of the GNU Library
8 * General Public License, version 2.
9 * %End-Header%
10 */
11
12 #include <stdio.h>
13 #include <string.h>
14 #if HAVE_UNISTD_H
15 #include <unistd.h>
16 #endif
17
18 #include "ext2_fs.h"
19 #include "ext2fs.h"
20
21 struct ext2_file {
22 errcode_t magic;
23 ext2_filsys fs;
24 ext2_ino_t ino;
25 struct ext2_inode inode;
26 int flags;
27 __u64 pos;
28 blk_t blockno;
29 blk_t physblock;
30 char *buf;
31 };
32
33 #define BMAP_BUFFER (file->buf + fs->blocksize)
34
ext2fs_file_open2(ext2_filsys fs,ext2_ino_t ino,struct ext2_inode * inode,int flags,ext2_file_t * ret)35 errcode_t ext2fs_file_open2(ext2_filsys fs, ext2_ino_t ino,
36 struct ext2_inode *inode,
37 int flags, ext2_file_t *ret)
38 {
39 ext2_file_t file;
40 errcode_t retval;
41
42 /*
43 * Don't let caller create or open a file for writing if the
44 * filesystem is read-only.
45 */
46 if ((flags & (EXT2_FILE_WRITE | EXT2_FILE_CREATE)) &&
47 !(fs->flags & EXT2_FLAG_RW))
48 return EXT2_ET_RO_FILSYS;
49
50 retval = ext2fs_get_mem(sizeof(struct ext2_file), &file);
51 if (retval)
52 return retval;
53
54 memset(file, 0, sizeof(struct ext2_file));
55 file->magic = EXT2_ET_MAGIC_EXT2_FILE;
56 file->fs = fs;
57 file->ino = ino;
58 file->flags = flags & EXT2_FILE_MASK;
59
60 if (inode) {
61 memcpy(&file->inode, inode, sizeof(struct ext2_inode));
62 } else {
63 retval = ext2fs_read_inode(fs, ino, &file->inode);
64 if (retval)
65 goto fail;
66 }
67
68 retval = ext2fs_get_array(3, fs->blocksize, &file->buf);
69 if (retval)
70 goto fail;
71
72 *ret = file;
73 return 0;
74
75 fail:
76 if (file->buf)
77 ext2fs_free_mem(&file->buf);
78 ext2fs_free_mem(&file);
79 return retval;
80 }
81
ext2fs_file_open(ext2_filsys fs,ext2_ino_t ino,int flags,ext2_file_t * ret)82 errcode_t ext2fs_file_open(ext2_filsys fs, ext2_ino_t ino,
83 int flags, ext2_file_t *ret)
84 {
85 return ext2fs_file_open2(fs, ino, NULL, flags, ret);
86 }
87
88 /*
89 * This function returns the filesystem handle of a file from the structure
90 */
ext2fs_file_get_fs(ext2_file_t file)91 ext2_filsys ext2fs_file_get_fs(ext2_file_t file)
92 {
93 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
94 return 0;
95 return file->fs;
96 }
97
98 /*
99 * This function flushes the dirty block buffer out to disk if
100 * necessary.
101 */
ext2fs_file_flush(ext2_file_t file)102 errcode_t ext2fs_file_flush(ext2_file_t file)
103 {
104 errcode_t retval;
105 ext2_filsys fs;
106
107 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
108 fs = file->fs;
109
110 if (!(file->flags & EXT2_FILE_BUF_VALID) ||
111 !(file->flags & EXT2_FILE_BUF_DIRTY))
112 return 0;
113
114 /*
115 * OK, the physical block hasn't been allocated yet.
116 * Allocate it.
117 */
118 if (!file->physblock) {
119 retval = ext2fs_bmap(fs, file->ino, &file->inode,
120 BMAP_BUFFER, file->ino ? BMAP_ALLOC : 0,
121 file->blockno, &file->physblock);
122 if (retval)
123 return retval;
124 }
125
126 retval = io_channel_write_blk(fs->io, file->physblock,
127 1, file->buf);
128 if (retval)
129 return retval;
130
131 file->flags &= ~EXT2_FILE_BUF_DIRTY;
132
133 return retval;
134 }
135
136 /*
137 * This function synchronizes the file's block buffer and the current
138 * file position, possibly invalidating block buffer if necessary
139 */
sync_buffer_position(ext2_file_t file)140 static errcode_t sync_buffer_position(ext2_file_t file)
141 {
142 blk_t b;
143 errcode_t retval;
144
145 b = file->pos / file->fs->blocksize;
146 if (b != file->blockno) {
147 retval = ext2fs_file_flush(file);
148 if (retval)
149 return retval;
150 file->flags &= ~EXT2_FILE_BUF_VALID;
151 }
152 file->blockno = b;
153 return 0;
154 }
155
156 /*
157 * This function loads the file's block buffer with valid data from
158 * the disk as necessary.
159 *
160 * If dontfill is true, then skip initializing the buffer since we're
161 * going to be replacing its entire contents anyway. If set, then the
162 * function basically only sets file->physblock and EXT2_FILE_BUF_VALID
163 */
164 #define DONTFILL 1
load_buffer(ext2_file_t file,int dontfill)165 static errcode_t load_buffer(ext2_file_t file, int dontfill)
166 {
167 ext2_filsys fs = file->fs;
168 errcode_t retval;
169
170 if (!(file->flags & EXT2_FILE_BUF_VALID)) {
171 retval = ext2fs_bmap(fs, file->ino, &file->inode,
172 BMAP_BUFFER, 0, file->blockno,
173 &file->physblock);
174 if (retval)
175 return retval;
176 if (!dontfill) {
177 if (file->physblock) {
178 retval = io_channel_read_blk(fs->io,
179 file->physblock,
180 1, file->buf);
181 if (retval)
182 return retval;
183 } else
184 memset(file->buf, 0, fs->blocksize);
185 }
186 file->flags |= EXT2_FILE_BUF_VALID;
187 }
188 return 0;
189 }
190
191
ext2fs_file_close(ext2_file_t file)192 errcode_t ext2fs_file_close(ext2_file_t file)
193 {
194 errcode_t retval;
195
196 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
197
198 retval = ext2fs_file_flush(file);
199
200 if (file->buf)
201 ext2fs_free_mem(&file->buf);
202 ext2fs_free_mem(&file);
203
204 return retval;
205 }
206
207
ext2fs_file_read(ext2_file_t file,void * buf,unsigned int wanted,unsigned int * got)208 errcode_t ext2fs_file_read(ext2_file_t file, void *buf,
209 unsigned int wanted, unsigned int *got)
210 {
211 ext2_filsys fs;
212 errcode_t retval = 0;
213 unsigned int start, c, count = 0;
214 __u64 left;
215 char *ptr = (char *) buf;
216
217 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
218 fs = file->fs;
219
220 while ((file->pos < EXT2_I_SIZE(&file->inode)) && (wanted > 0)) {
221 retval = sync_buffer_position(file);
222 if (retval)
223 goto fail;
224 retval = load_buffer(file, 0);
225 if (retval)
226 goto fail;
227
228 start = file->pos % fs->blocksize;
229 c = fs->blocksize - start;
230 if (c > wanted)
231 c = wanted;
232 left = EXT2_I_SIZE(&file->inode) - file->pos ;
233 if (c > left)
234 c = left;
235
236 memcpy(ptr, file->buf+start, c);
237 file->pos += c;
238 ptr += c;
239 count += c;
240 wanted -= c;
241 }
242
243 fail:
244 if (got)
245 *got = count;
246 return retval;
247 }
248
249
ext2fs_file_write(ext2_file_t file,const void * buf,unsigned int nbytes,unsigned int * written)250 errcode_t ext2fs_file_write(ext2_file_t file, const void *buf,
251 unsigned int nbytes, unsigned int *written)
252 {
253 ext2_filsys fs;
254 errcode_t retval = 0;
255 unsigned int start, c, count = 0;
256 const char *ptr = (const char *) buf;
257
258 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
259 fs = file->fs;
260
261 if (!(file->flags & EXT2_FILE_WRITE))
262 return EXT2_ET_FILE_RO;
263
264 while (nbytes > 0) {
265 retval = sync_buffer_position(file);
266 if (retval)
267 goto fail;
268
269 start = file->pos % fs->blocksize;
270 c = fs->blocksize - start;
271 if (c > nbytes)
272 c = nbytes;
273
274 /*
275 * We only need to do a read-modify-update cycle if
276 * we're doing a partial write.
277 */
278 retval = load_buffer(file, (c == fs->blocksize));
279 if (retval)
280 goto fail;
281
282 file->flags |= EXT2_FILE_BUF_DIRTY;
283 memcpy(file->buf+start, ptr, c);
284 file->pos += c;
285 ptr += c;
286 count += c;
287 nbytes -= c;
288 }
289
290 fail:
291 if (written)
292 *written = count;
293 return retval;
294 }
295
ext2fs_file_llseek(ext2_file_t file,__u64 offset,int whence,__u64 * ret_pos)296 errcode_t ext2fs_file_llseek(ext2_file_t file, __u64 offset,
297 int whence, __u64 *ret_pos)
298 {
299 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
300
301 if (whence == EXT2_SEEK_SET)
302 file->pos = offset;
303 else if (whence == EXT2_SEEK_CUR)
304 file->pos += offset;
305 else if (whence == EXT2_SEEK_END)
306 file->pos = EXT2_I_SIZE(&file->inode) + offset;
307 else
308 return EXT2_ET_INVALID_ARGUMENT;
309
310 if (ret_pos)
311 *ret_pos = file->pos;
312
313 return 0;
314 }
315
ext2fs_file_lseek(ext2_file_t file,ext2_off_t offset,int whence,ext2_off_t * ret_pos)316 errcode_t ext2fs_file_lseek(ext2_file_t file, ext2_off_t offset,
317 int whence, ext2_off_t *ret_pos)
318 {
319 __u64 loffset, ret_loffset;
320 errcode_t retval;
321
322 loffset = offset;
323 retval = ext2fs_file_llseek(file, loffset, whence, &ret_loffset);
324 if (ret_pos)
325 *ret_pos = (ext2_off_t) ret_loffset;
326 return retval;
327 }
328
329
330 /*
331 * This function returns the size of the file, according to the inode
332 */
ext2fs_file_get_lsize(ext2_file_t file,__u64 * ret_size)333 errcode_t ext2fs_file_get_lsize(ext2_file_t file, __u64 *ret_size)
334 {
335 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
336 return EXT2_ET_MAGIC_EXT2_FILE;
337 *ret_size = EXT2_I_SIZE(&file->inode);
338 return 0;
339 }
340
341 /*
342 * This function returns the size of the file, according to the inode
343 */
ext2fs_file_get_size(ext2_file_t file)344 ext2_off_t ext2fs_file_get_size(ext2_file_t file)
345 {
346 __u64 size;
347
348 if (ext2fs_file_get_lsize(file, &size))
349 return 0;
350 if ((size >> 32) != 0)
351 return 0;
352 return size;
353 }
354
355 /*
356 * This function sets the size of the file, truncating it if necessary
357 *
358 * XXX still need to call truncate
359 */
ext2fs_file_set_size(ext2_file_t file,ext2_off_t size)360 errcode_t ext2fs_file_set_size(ext2_file_t file, ext2_off_t size)
361 {
362 errcode_t retval;
363 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
364
365 file->inode.i_size = size;
366 file->inode.i_size_high = 0;
367 if (file->ino) {
368 retval = ext2fs_write_inode(file->fs, file->ino, &file->inode);
369 if (retval)
370 return retval;
371 }
372
373 /*
374 * XXX truncate inode if necessary
375 */
376
377 return 0;
378 }
379