fileio.c revision 9f8046fc6dfc13eee2f5c363214e60b533872cac
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 21struct ext2_file { 22 errcode_t magic; 23 ext2_filsys fs; 24 ext2_ino_t ino; 25 struct ext2_inode inode; 26 int flags; 27 ext2_off_t pos; 28 blk_t blockno; 29 blk_t physblock; 30 char *buf; 31}; 32 33#define BMAP_BUFFER (file->buf + fs->blocksize) 34 35errcode_t ext2fs_file_open(ext2_filsys fs, ext2_ino_t ino, 36 int flags, ext2_file_t *ret) 37{ 38 ext2_file_t file; 39 errcode_t retval; 40 41 /* 42 * Don't let caller create or open a file for writing if the 43 * filesystem is read-only. 44 */ 45 if ((flags & (EXT2_FILE_WRITE | EXT2_FILE_CREATE)) && 46 !(fs->flags & EXT2_FLAG_RW)) 47 return EXT2_ET_RO_FILSYS; 48 49 retval = ext2fs_get_mem(sizeof(struct ext2_file), (void **) &file); 50 if (retval) 51 return retval; 52 53 memset(file, 0, sizeof(struct ext2_file)); 54 file->magic = EXT2_ET_MAGIC_EXT2_FILE; 55 file->fs = fs; 56 file->ino = ino; 57 file->flags = flags & EXT2_FILE_MASK; 58 59 retval = ext2fs_read_inode(fs, ino, &file->inode); 60 if (retval) 61 goto fail; 62 63 retval = ext2fs_get_mem(fs->blocksize * 3, (void **) &file->buf); 64 if (retval) 65 goto fail; 66 67 *ret = file; 68 return 0; 69 70fail: 71 if (file->buf) 72 ext2fs_free_mem((void **) &file->buf); 73 ext2fs_free_mem((void **) &file); 74 return retval; 75} 76 77/* 78 * This function returns the filesystem handle of a file from the structure 79 */ 80ext2_filsys ext2fs_file_get_fs(ext2_file_t file) 81{ 82 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE) 83 return 0; 84 return file->fs; 85} 86 87/* 88 * This function flushes the dirty block buffer out to disk if 89 * necessary. 90 */ 91static errcode_t ext2fs_file_flush(ext2_file_t file) 92{ 93 errcode_t retval; 94 ext2_filsys fs; 95 96 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 97 fs = file->fs; 98 99 if (!(file->flags & EXT2_FILE_BUF_VALID) || 100 !(file->flags & EXT2_FILE_BUF_DIRTY)) 101 return 0; 102 103 /* 104 * OK, the physical block hasn't been allocated yet. 105 * Allocate it. 106 */ 107 if (!file->physblock) { 108 retval = ext2fs_bmap(fs, file->ino, &file->inode, 109 BMAP_BUFFER, BMAP_ALLOC, 110 file->blockno, &file->physblock); 111 if (retval) 112 return retval; 113 } 114 115 retval = io_channel_write_blk(fs->io, file->physblock, 116 1, file->buf); 117 if (retval) 118 return retval; 119 120 file->flags &= ~EXT2_FILE_BUF_DIRTY; 121 122 return retval; 123} 124 125/* 126 * This function synchronizes the file's block buffer and the current 127 * file position, possibly invalidating block buffer if necessary 128 */ 129static errcode_t sync_buffer_position(ext2_file_t file) 130{ 131 blk_t b; 132 errcode_t retval; 133 134 b = file->pos / file->fs->blocksize; 135 if (b != file->blockno) { 136 retval = ext2fs_file_flush(file); 137 if (retval) 138 return retval; 139 file->flags &= ~EXT2_FILE_BUF_VALID; 140 } 141 file->blockno = b; 142 return 0; 143} 144 145/* 146 * This function loads the file's block buffer with valid data from 147 * the disk as necessary. 148 * 149 * If dontfill is true, then skip initializing the buffer since we're 150 * going to be replacing its entire contents anyway. If set, then the 151 * function basically only sets file->physblock and EXT2_FILE_BUF_VALID 152 */ 153#define DONTFILL 1 154static errcode_t load_buffer(ext2_file_t file, int dontfill) 155{ 156 ext2_filsys fs = file->fs; 157 errcode_t retval; 158 159 if (!(file->flags & EXT2_FILE_BUF_VALID)) { 160 retval = ext2fs_bmap(fs, file->ino, &file->inode, 161 BMAP_BUFFER, 0, file->blockno, 162 &file->physblock); 163 if (retval) 164 return retval; 165 if (!dontfill) { 166 if (file->physblock) { 167 retval = io_channel_read_blk(fs->io, 168 file->physblock, 169 1, file->buf); 170 if (retval) 171 return retval; 172 } else 173 memset(file->buf, 0, fs->blocksize); 174 } 175 file->flags |= EXT2_FILE_BUF_VALID; 176 } 177 return 0; 178} 179 180 181errcode_t ext2fs_file_close(ext2_file_t file) 182{ 183 errcode_t retval; 184 185 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 186 187 retval = ext2fs_file_flush(file); 188 189 if (file->buf) 190 ext2fs_free_mem((void **) &file->buf); 191 ext2fs_free_mem((void **) &file); 192 193 return retval; 194} 195 196 197errcode_t ext2fs_file_read(ext2_file_t file, void *buf, 198 unsigned int wanted, unsigned int *got) 199{ 200 ext2_filsys fs; 201 errcode_t retval = 0; 202 unsigned int start, left, c, count = 0; 203 char *ptr = (char *) buf; 204 205 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 206 fs = file->fs; 207 208 while ((file->pos < file->inode.i_size) && (wanted > 0)) { 209 retval = sync_buffer_position(file); 210 if (retval) 211 goto fail; 212 retval = load_buffer(file, 0); 213 if (retval) 214 goto fail; 215 216 start = file->pos % fs->blocksize; 217 c = fs->blocksize - start; 218 if (c > wanted) 219 c = wanted; 220 left = file->inode.i_size - file->pos ; 221 if (c > left) 222 c = left; 223 224 memcpy(ptr, file->buf+start, c); 225 file->pos += c; 226 ptr += c; 227 count += c; 228 wanted -= c; 229 } 230 231fail: 232 if (got) 233 *got = count; 234 return retval; 235} 236 237 238errcode_t ext2fs_file_write(ext2_file_t file, void *buf, 239 unsigned int nbytes, unsigned int *written) 240{ 241 ext2_filsys fs; 242 blk_t pb; 243 errcode_t retval = 0; 244 unsigned int start, c, count = 0; 245 char *ptr = (char *) buf; 246 int dontfill; 247 248 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 249 fs = file->fs; 250 251 if (!(file->flags & EXT2_FILE_WRITE)) 252 return EXT2_ET_FILE_RO; 253 254 while (nbytes > 0) { 255 retval = sync_buffer_position(file); 256 if (retval) 257 goto fail; 258 259 start = file->pos % fs->blocksize; 260 c = fs->blocksize - start; 261 if (c > nbytes) 262 c = nbytes; 263 264 /* 265 * We only need to do a read-modify-update cycle if 266 * we're doing a partial write. 267 */ 268 retval = load_buffer(file, (c == fs->blocksize)); 269 if (retval) 270 goto fail; 271 272 file->flags |= EXT2_FILE_BUF_DIRTY; 273 memcpy(file->buf+start, ptr, c); 274 file->pos += c; 275 ptr += c; 276 count += c; 277 nbytes -= c; 278 } 279 280fail: 281 if (written) 282 *written = count; 283 return retval; 284} 285 286errcode_t ext2fs_file_lseek(ext2_file_t file, ext2_off_t offset, 287 int whence, ext2_off_t *ret_pos) 288{ 289 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 290 291 if (whence == EXT2_SEEK_SET) 292 file->pos = offset; 293 else if (whence == EXT2_SEEK_CUR) 294 file->pos += offset; 295 else if (whence == EXT2_SEEK_END) 296 file->pos = file->inode.i_size + offset; 297 else 298 return EXT2_ET_INVALID_ARGUMENT; 299 300 if (ret_pos) 301 *ret_pos = file->pos; 302 303 return 0; 304} 305 306/* 307 * This function returns the size of the file, according to the inode 308 */ 309ext2_off_t ext2fs_file_get_size(ext2_file_t file) 310{ 311 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE) 312 return 0; 313 return file->inode.i_size; 314} 315 316/* 317 * This function sets the size of the file, truncating it if necessary 318 * 319 * XXX still need to call truncate 320 */ 321errcode_t ext2fs_file_set_size(ext2_file_t file, ext2_off_t size) 322{ 323 errcode_t retval; 324 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 325 326 file->inode.i_size = size; 327 retval = ext2fs_write_inode(file->fs, file->ino, &file->inode); 328 if (retval) 329 return retval; 330 331 /* 332 * XXX truncate inode if necessary 333 */ 334 335 return 0; 336} 337