fileio.c revision d1154eb460efe588eaed3d439c1caaca149fa362 
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/*
110 * This function flushes the dirty block buffer out to disk if
111 * necessary.
112 */
113errcode_t ext2fs_file_flush(ext2_file_t file)
114{
115	errcode_t	retval;
116	ext2_filsys fs;
117
118	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
119	fs = file->fs;
120
121	if (!(file->flags & EXT2_FILE_BUF_VALID) ||
122	    !(file->flags & EXT2_FILE_BUF_DIRTY))
123		return 0;
124
125	/*
126	 * OK, the physical block hasn't been allocated yet.
127	 * Allocate it.
128	 */
129	if (!file->physblock) {
130		retval = ext2fs_bmap2(fs, file->ino, &file->inode,
131				     BMAP_BUFFER, file->ino ? BMAP_ALLOC : 0,
132				     file->blockno, 0, &file->physblock);
133		if (retval)
134			return retval;
135	}
136
137	retval = io_channel_write_blk(fs->io, file->physblock,
138				      1, file->buf);
139	if (retval)
140		return retval;
141
142	file->flags &= ~EXT2_FILE_BUF_DIRTY;
143
144	return retval;
145}
146
147/*
148 * This function synchronizes the file's block buffer and the current
149 * file position, possibly invalidating block buffer if necessary
150 */
151static errcode_t sync_buffer_position(ext2_file_t file)
152{
153	blk_t	b;
154	errcode_t	retval;
155
156	b = file->pos / file->fs->blocksize;
157	if (b != file->blockno) {
158		retval = ext2fs_file_flush(file);
159		if (retval)
160			return retval;
161		file->flags &= ~EXT2_FILE_BUF_VALID;
162	}
163	file->blockno = b;
164	return 0;
165}
166
167/*
168 * This function loads the file's block buffer with valid data from
169 * the disk as necessary.
170 *
171 * If dontfill is true, then skip initializing the buffer since we're
172 * going to be replacing its entire contents anyway.  If set, then the
173 * function basically only sets file->physblock and EXT2_FILE_BUF_VALID
174 */
175#define DONTFILL 1
176static errcode_t load_buffer(ext2_file_t file, int dontfill)
177{
178	ext2_filsys	fs = file->fs;
179	errcode_t	retval;
180
181	if (!(file->flags & EXT2_FILE_BUF_VALID)) {
182		retval = ext2fs_bmap2(fs, file->ino, &file->inode,
183				     BMAP_BUFFER, 0, file->blockno, 0,
184				     &file->physblock);
185		if (retval)
186			return retval;
187		if (!dontfill) {
188			if (file->physblock) {
189				retval = io_channel_read_blk(fs->io,
190							     file->physblock,
191							     1, file->buf);
192				if (retval)
193					return retval;
194			} else
195				memset(file->buf, 0, fs->blocksize);
196		}
197		file->flags |= EXT2_FILE_BUF_VALID;
198	}
199	return 0;
200}
201
202
203errcode_t ext2fs_file_close(ext2_file_t file)
204{
205	errcode_t	retval;
206
207	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
208
209	retval = ext2fs_file_flush(file);
210
211	if (file->buf)
212		ext2fs_free_mem(&file->buf);
213	ext2fs_free_mem(&file);
214
215	return retval;
216}
217
218
219errcode_t ext2fs_file_read(ext2_file_t file, void *buf,
220			   unsigned int wanted, unsigned int *got)
221{
222	ext2_filsys	fs;
223	errcode_t	retval = 0;
224	unsigned int	start, c, count = 0;
225	__u64		left;
226	char		*ptr = (char *) buf;
227
228	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
229	fs = file->fs;
230
231	while ((file->pos < EXT2_I_SIZE(&file->inode)) && (wanted > 0)) {
232		retval = sync_buffer_position(file);
233		if (retval)
234			goto fail;
235		retval = load_buffer(file, 0);
236		if (retval)
237			goto fail;
238
239		start = file->pos % fs->blocksize;
240		c = fs->blocksize - start;
241		if (c > wanted)
242			c = wanted;
243		left = EXT2_I_SIZE(&file->inode) - file->pos ;
244		if (c > left)
245			c = left;
246
247		memcpy(ptr, file->buf+start, c);
248		file->pos += c;
249		ptr += c;
250		count += c;
251		wanted -= c;
252	}
253
254fail:
255	if (got)
256		*got = count;
257	return retval;
258}
259
260
261errcode_t ext2fs_file_write(ext2_file_t file, const void *buf,
262			    unsigned int nbytes, unsigned int *written)
263{
264	ext2_filsys	fs;
265	errcode_t	retval = 0;
266	unsigned int	start, c, count = 0;
267	const char	*ptr = (const char *) buf;
268
269	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
270	fs = file->fs;
271
272	if (!(file->flags & EXT2_FILE_WRITE))
273		return EXT2_ET_FILE_RO;
274
275	while (nbytes > 0) {
276		retval = sync_buffer_position(file);
277		if (retval)
278			goto fail;
279
280		start = file->pos % fs->blocksize;
281		c = fs->blocksize - start;
282		if (c > nbytes)
283			c = nbytes;
284
285		/*
286		 * We only need to do a read-modify-update cycle if
287		 * we're doing a partial write.
288		 */
289		retval = load_buffer(file, (c == fs->blocksize));
290		if (retval)
291			goto fail;
292
293		file->flags |= EXT2_FILE_BUF_DIRTY;
294		memcpy(file->buf+start, ptr, c);
295		file->pos += c;
296		ptr += c;
297		count += c;
298		nbytes -= c;
299	}
300
301fail:
302	if (written)
303		*written = count;
304	return retval;
305}
306
307errcode_t ext2fs_file_llseek(ext2_file_t file, __u64 offset,
308			    int whence, __u64 *ret_pos)
309{
310	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
311
312	if (whence == EXT2_SEEK_SET)
313		file->pos = offset;
314	else if (whence == EXT2_SEEK_CUR)
315		file->pos += offset;
316	else if (whence == EXT2_SEEK_END)
317		file->pos = EXT2_I_SIZE(&file->inode) + offset;
318	else
319		return EXT2_ET_INVALID_ARGUMENT;
320
321	if (ret_pos)
322		*ret_pos = file->pos;
323
324	return 0;
325}
326
327errcode_t ext2fs_file_lseek(ext2_file_t file, ext2_off_t offset,
328			    int whence, ext2_off_t *ret_pos)
329{
330	__u64		loffset, ret_loffset;
331	errcode_t	retval;
332
333	loffset = offset;
334	retval = ext2fs_file_llseek(file, loffset, whence, &ret_loffset);
335	if (ret_pos)
336		*ret_pos = (ext2_off_t) ret_loffset;
337	return retval;
338}
339
340
341/*
342 * This function returns the size of the file, according to the inode
343 */
344errcode_t ext2fs_file_get_lsize(ext2_file_t file, __u64 *ret_size)
345{
346	if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
347		return EXT2_ET_MAGIC_EXT2_FILE;
348	*ret_size = EXT2_I_SIZE(&file->inode);
349	return 0;
350}
351
352/*
353 * This function returns the size of the file, according to the inode
354 */
355ext2_off_t ext2fs_file_get_size(ext2_file_t file)
356{
357	__u64	size;
358
359	if (ext2fs_file_get_lsize(file, &size))
360		return 0;
361	if ((size >> 32) != 0)
362		return 0;
363	return size;
364}
365
366/*
367 * This function sets the size of the file, truncating it if necessary
368 *
369 */
370errcode_t ext2fs_file_set_size2(ext2_file_t file, ext2_off64_t size)
371{
372	ext2_off64_t	old_size;
373	errcode_t	retval;
374	blk64_t		old_truncate, truncate_block;
375
376	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
377
378	truncate_block = ((size + file->fs->blocksize - 1) >>
379			  EXT2_BLOCK_SIZE_BITS(file->fs->super)) + 1;
380	old_size = EXT2_I_SIZE(&file->inode);
381	old_truncate = ((old_size + file->fs->blocksize - 1) >>
382		      EXT2_BLOCK_SIZE_BITS(file->fs->super)) + 1;
383
384	file->inode.i_size = size & 0xffffffff;
385	file->inode.i_size_high = (size >> 32);
386	if (file->ino) {
387		retval = ext2fs_write_inode(file->fs, file->ino, &file->inode);
388		if (retval)
389			return retval;
390	}
391
392	if (truncate_block <= old_truncate)
393		return 0;
394
395	return ext2fs_punch(file->fs, file->ino, &file->inode, 0,
396			    truncate_block, ~0ULL);
397}
398
399errcode_t ext2fs_file_set_size(ext2_file_t file, ext2_off_t size)
400{
401	return ext2fs_file_set_size2(file, size);
402}
403