fileio.c revision 3ae682bb0a5e025963b25ff5ac5d53e2115483f2 
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 "config.h"
13#include <stdio.h>
14#include <string.h>
15#if HAVE_UNISTD_H
16#include <unistd.h>
17#endif
18
19#include "ext2_fs.h"
20#include "ext2fs.h"
21
22struct ext2_file {
23	errcode_t		magic;
24	ext2_filsys 		fs;
25	ext2_ino_t		ino;
26	struct ext2_inode	inode;
27	int 			flags;
28	__u64			pos;
29	blk64_t			blockno;
30	blk64_t			physblock;
31	char 			*buf;
32};
33
34#define BMAP_BUFFER (file->buf + fs->blocksize)
35
36errcode_t ext2fs_file_open2(ext2_filsys fs, ext2_ino_t ino,
37			    struct ext2_inode *inode,
38			    int flags, ext2_file_t *ret)
39{
40	ext2_file_t 	file;
41	errcode_t	retval;
42
43	/*
44	 * Don't let caller create or open a file for writing if the
45	 * filesystem is read-only.
46	 */
47	if ((flags & (EXT2_FILE_WRITE | EXT2_FILE_CREATE)) &&
48	    !(fs->flags & EXT2_FLAG_RW))
49		return EXT2_ET_RO_FILSYS;
50
51	retval = ext2fs_get_mem(sizeof(struct ext2_file), &file);
52	if (retval)
53		return retval;
54
55	memset(file, 0, sizeof(struct ext2_file));
56	file->magic = EXT2_ET_MAGIC_EXT2_FILE;
57	file->fs = fs;
58	file->ino = ino;
59	file->flags = flags & EXT2_FILE_MASK;
60
61	if (inode) {
62		memcpy(&file->inode, inode, sizeof(struct ext2_inode));
63	} else {
64		retval = ext2fs_read_inode(fs, ino, &file->inode);
65		if (retval)
66			goto fail;
67	}
68
69	retval = ext2fs_get_array(3, fs->blocksize, &file->buf);
70	if (retval)
71		goto fail;
72
73	*ret = file;
74	return 0;
75
76fail:
77	if (file->buf)
78		ext2fs_free_mem(&file->buf);
79	ext2fs_free_mem(&file);
80	return retval;
81}
82
83errcode_t ext2fs_file_open(ext2_filsys fs, ext2_ino_t ino,
84			   int flags, ext2_file_t *ret)
85{
86	return ext2fs_file_open2(fs, ino, NULL, flags, ret);
87}
88
89/*
90 * This function returns the filesystem handle of a file from the structure
91 */
92ext2_filsys ext2fs_file_get_fs(ext2_file_t file)
93{
94	if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
95		return 0;
96	return file->fs;
97}
98
99/*
100 * This function returns the pointer to the inode of a file from the structure
101 */
102struct ext2_inode *ext2fs_file_get_inode(ext2_file_t file)
103{
104	if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
105		return NULL;
106	return &file->inode;
107}
108
109/* This function returns the inode number from the structure */
110ext2_ino_t ext2fs_file_get_inode_num(ext2_file_t file)
111{
112	if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
113		return 0;
114	return file->ino;
115}
116
117/*
118 * This function flushes the dirty block buffer out to disk if
119 * necessary.
120 */
121errcode_t ext2fs_file_flush(ext2_file_t file)
122{
123	errcode_t	retval;
124	ext2_filsys fs;
125
126	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
127	fs = file->fs;
128
129	if (!(file->flags & EXT2_FILE_BUF_VALID) ||
130	    !(file->flags & EXT2_FILE_BUF_DIRTY))
131		return 0;
132
133	/*
134	 * OK, the physical block hasn't been allocated yet.
135	 * Allocate it.
136	 */
137	if (!file->physblock) {
138		retval = ext2fs_bmap2(fs, file->ino, &file->inode,
139				     BMAP_BUFFER, file->ino ? BMAP_ALLOC : 0,
140				     file->blockno, 0, &file->physblock);
141		if (retval)
142			return retval;
143	}
144
145	retval = io_channel_write_blk(fs->io, file->physblock,
146				      1, file->buf);
147	if (retval)
148		return retval;
149
150	file->flags &= ~EXT2_FILE_BUF_DIRTY;
151
152	return retval;
153}
154
155/*
156 * This function synchronizes the file's block buffer and the current
157 * file position, possibly invalidating block buffer if necessary
158 */
159static errcode_t sync_buffer_position(ext2_file_t file)
160{
161	blk_t	b;
162	errcode_t	retval;
163
164	b = file->pos / file->fs->blocksize;
165	if (b != file->blockno) {
166		retval = ext2fs_file_flush(file);
167		if (retval)
168			return retval;
169		file->flags &= ~EXT2_FILE_BUF_VALID;
170	}
171	file->blockno = b;
172	return 0;
173}
174
175/*
176 * This function loads the file's block buffer with valid data from
177 * the disk as necessary.
178 *
179 * If dontfill is true, then skip initializing the buffer since we're
180 * going to be replacing its entire contents anyway.  If set, then the
181 * function basically only sets file->physblock and EXT2_FILE_BUF_VALID
182 */
183#define DONTFILL 1
184static errcode_t load_buffer(ext2_file_t file, int dontfill)
185{
186	ext2_filsys	fs = file->fs;
187	errcode_t	retval;
188
189	if (!(file->flags & EXT2_FILE_BUF_VALID)) {
190		retval = ext2fs_bmap2(fs, file->ino, &file->inode,
191				     BMAP_BUFFER, 0, file->blockno, 0,
192				     &file->physblock);
193		if (retval)
194			return retval;
195		if (!dontfill) {
196			if (file->physblock) {
197				retval = io_channel_read_blk(fs->io,
198							     file->physblock,
199							     1, file->buf);
200				if (retval)
201					return retval;
202			} else
203				memset(file->buf, 0, fs->blocksize);
204		}
205		file->flags |= EXT2_FILE_BUF_VALID;
206	}
207	return 0;
208}
209
210
211errcode_t ext2fs_file_close(ext2_file_t file)
212{
213	errcode_t	retval;
214
215	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
216
217	retval = ext2fs_file_flush(file);
218
219	if (file->buf)
220		ext2fs_free_mem(&file->buf);
221	ext2fs_free_mem(&file);
222
223	return retval;
224}
225
226
227errcode_t ext2fs_file_read(ext2_file_t file, void *buf,
228			   unsigned int wanted, unsigned int *got)
229{
230	ext2_filsys	fs;
231	errcode_t	retval = 0;
232	unsigned int	start, c, count = 0;
233	__u64		left;
234	char		*ptr = (char *) buf;
235
236	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
237	fs = file->fs;
238
239	while ((file->pos < EXT2_I_SIZE(&file->inode)) && (wanted > 0)) {
240		retval = sync_buffer_position(file);
241		if (retval)
242			goto fail;
243		retval = load_buffer(file, 0);
244		if (retval)
245			goto fail;
246
247		start = file->pos % fs->blocksize;
248		c = fs->blocksize - start;
249		if (c > wanted)
250			c = wanted;
251		left = EXT2_I_SIZE(&file->inode) - file->pos ;
252		if (c > left)
253			c = left;
254
255		memcpy(ptr, file->buf+start, c);
256		file->pos += c;
257		ptr += c;
258		count += c;
259		wanted -= c;
260	}
261
262fail:
263	if (got)
264		*got = count;
265	return retval;
266}
267
268
269errcode_t ext2fs_file_write(ext2_file_t file, const void *buf,
270			    unsigned int nbytes, unsigned int *written)
271{
272	ext2_filsys	fs;
273	errcode_t	retval = 0;
274	unsigned int	start, c, count = 0;
275	const char	*ptr = (const char *) buf;
276
277	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
278	fs = file->fs;
279
280	if (!(file->flags & EXT2_FILE_WRITE))
281		return EXT2_ET_FILE_RO;
282
283	while (nbytes > 0) {
284		retval = sync_buffer_position(file);
285		if (retval)
286			goto fail;
287
288		start = file->pos % fs->blocksize;
289		c = fs->blocksize - start;
290		if (c > nbytes)
291			c = nbytes;
292
293		/*
294		 * We only need to do a read-modify-update cycle if
295		 * we're doing a partial write.
296		 */
297		retval = load_buffer(file, (c == fs->blocksize));
298		if (retval)
299			goto fail;
300
301		file->flags |= EXT2_FILE_BUF_DIRTY;
302		memcpy(file->buf+start, ptr, c);
303		file->pos += c;
304		ptr += c;
305		count += c;
306		nbytes -= c;
307	}
308
309fail:
310	if (written)
311		*written = count;
312	return retval;
313}
314
315errcode_t ext2fs_file_llseek(ext2_file_t file, __u64 offset,
316			    int whence, __u64 *ret_pos)
317{
318	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
319
320	if (whence == EXT2_SEEK_SET)
321		file->pos = offset;
322	else if (whence == EXT2_SEEK_CUR)
323		file->pos += offset;
324	else if (whence == EXT2_SEEK_END)
325		file->pos = EXT2_I_SIZE(&file->inode) + offset;
326	else
327		return EXT2_ET_INVALID_ARGUMENT;
328
329	if (ret_pos)
330		*ret_pos = file->pos;
331
332	return 0;
333}
334
335errcode_t ext2fs_file_lseek(ext2_file_t file, ext2_off_t offset,
336			    int whence, ext2_off_t *ret_pos)
337{
338	__u64		loffset, ret_loffset;
339	errcode_t	retval;
340
341	loffset = offset;
342	retval = ext2fs_file_llseek(file, loffset, whence, &ret_loffset);
343	if (ret_pos)
344		*ret_pos = (ext2_off_t) ret_loffset;
345	return retval;
346}
347
348
349/*
350 * This function returns the size of the file, according to the inode
351 */
352errcode_t ext2fs_file_get_lsize(ext2_file_t file, __u64 *ret_size)
353{
354	if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
355		return EXT2_ET_MAGIC_EXT2_FILE;
356	*ret_size = EXT2_I_SIZE(&file->inode);
357	return 0;
358}
359
360/*
361 * This function returns the size of the file, according to the inode
362 */
363ext2_off_t ext2fs_file_get_size(ext2_file_t file)
364{
365	__u64	size;
366
367	if (ext2fs_file_get_lsize(file, &size))
368		return 0;
369	if ((size >> 32) != 0)
370		return 0;
371	return size;
372}
373
374/*
375 * This function sets the size of the file, truncating it if necessary
376 *
377 */
378errcode_t ext2fs_file_set_size2(ext2_file_t file, ext2_off64_t size)
379{
380	ext2_off64_t	old_size;
381	errcode_t	retval;
382	blk64_t		old_truncate, truncate_block;
383
384	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
385
386	truncate_block = ((size + file->fs->blocksize - 1) >>
387			  EXT2_BLOCK_SIZE_BITS(file->fs->super)) + 1;
388	old_size = EXT2_I_SIZE(&file->inode);
389	old_truncate = ((old_size + file->fs->blocksize - 1) >>
390		      EXT2_BLOCK_SIZE_BITS(file->fs->super)) + 1;
391
392	file->inode.i_size = size & 0xffffffff;
393	file->inode.i_size_high = (size >> 32);
394	if (file->ino) {
395		retval = ext2fs_write_inode(file->fs, file->ino, &file->inode);
396		if (retval)
397			return retval;
398	}
399
400	if (truncate_block >= old_truncate)
401		return 0;
402
403	return ext2fs_punch(file->fs, file->ino, &file->inode, 0,
404			    truncate_block, ~0ULL);
405}
406
407errcode_t ext2fs_file_set_size(ext2_file_t file, ext2_off_t size)
408{
409	return ext2fs_file_set_size2(file, size);
410}
411