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 Public 8 * License. 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 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 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 */ 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 */ 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 */ 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 1 165 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 } 190 191 192 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 } 206 207 208 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 } 248 249 250 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 } 295 296 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 } 315 316 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 */ 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 */ 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 */ 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
