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Sourcecode: e2fsprogs version File versions

fileio.c

/*
 * fileio.c --- Simple file I/O routines
 * 
 * Copyright (C) 1997 Theodore Ts'o.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 */

#include <stdio.h>
#include <string.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "ext2_fs.h"
#include "ext2fs.h"

struct ext2_file {
      errcode_t         magic;
      ext2_filsys             fs;
      ext2_ino_t        ino;
      struct ext2_inode inode;
      int               flags;
      __u64             pos;
      blk_t             blockno;
      blk_t             physblock;
      char              *buf;
};

#define BMAP_BUFFER (file->buf + fs->blocksize)

errcode_t ext2fs_file_open2(ext2_filsys fs, ext2_ino_t ino,
                      struct ext2_inode *inode,
                      int flags, ext2_file_t *ret)
{
      ext2_file_t       file;
      errcode_t   retval;

      /*
       * Don't let caller create or open a file for writing if the
       * filesystem is read-only.
       */
      if ((flags & (EXT2_FILE_WRITE | EXT2_FILE_CREATE)) &&
          !(fs->flags & EXT2_FLAG_RW))
            return EXT2_ET_RO_FILSYS;

      retval = ext2fs_get_mem(sizeof(struct ext2_file), &file);
      if (retval)
            return retval;
      
      memset(file, 0, sizeof(struct ext2_file));
      file->magic = EXT2_ET_MAGIC_EXT2_FILE;
      file->fs = fs;
      file->ino = ino;
      file->flags = flags & EXT2_FILE_MASK;

      if (inode) {
            memcpy(&file->inode, inode, sizeof(struct ext2_inode));
      } else {
            retval = ext2fs_read_inode(fs, ino, &file->inode);
            if (retval)
                  goto fail;
      }
      
      retval = ext2fs_get_mem(fs->blocksize * 3, &file->buf);
      if (retval)
            goto fail;

      *ret = file;
      return 0;
      
fail:
      if (file->buf)
            ext2fs_free_mem(&file->buf);
      ext2fs_free_mem(&file);
      return retval;
}

errcode_t ext2fs_file_open(ext2_filsys fs, ext2_ino_t ino,
                     int flags, ext2_file_t *ret)
{
      return ext2fs_file_open2(fs, ino, NULL, flags, ret);
}

/*
 * This function returns the filesystem handle of a file from the structure
 */
ext2_filsys ext2fs_file_get_fs(ext2_file_t file)
{
      if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
            return 0;
      return file->fs;
}

/*
 * This function flushes the dirty block buffer out to disk if
 * necessary.
 */
errcode_t ext2fs_file_flush(ext2_file_t file)
{
      errcode_t   retval;
      ext2_filsys fs;
      
      EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
      fs = file->fs;

      if (!(file->flags & EXT2_FILE_BUF_VALID) ||
          !(file->flags & EXT2_FILE_BUF_DIRTY))
            return 0;

      /*
       * OK, the physical block hasn't been allocated yet.
       * Allocate it.
       */
      if (!file->physblock) {
            retval = ext2fs_bmap(fs, file->ino, &file->inode,
                             BMAP_BUFFER, file->ino ? BMAP_ALLOC : 0,
                             file->blockno, &file->physblock);
            if (retval)
                  return retval;
      }

      retval = io_channel_write_blk(fs->io, file->physblock,
                              1, file->buf);
      if (retval)
            return retval;

      file->flags &= ~EXT2_FILE_BUF_DIRTY;

      return retval;
}

/*
 * This function synchronizes the file's block buffer and the current
 * file position, possibly invalidating block buffer if necessary
 */
static errcode_t sync_buffer_position(ext2_file_t file)
{
      blk_t b;
      errcode_t   retval;

      b = file->pos / file->fs->blocksize;
      if (b != file->blockno) {
            retval = ext2fs_file_flush(file);
            if (retval)
                  return retval;
            file->flags &= ~EXT2_FILE_BUF_VALID;
      }
      file->blockno = b;
      return 0;
}

/*
 * This function loads the file's block buffer with valid data from
 * the disk as necessary.
 *
 * If dontfill is true, then skip initializing the buffer since we're
 * going to be replacing its entire contents anyway.  If set, then the
 * function basically only sets file->physblock and EXT2_FILE_BUF_VALID
 */
#define DONTFILL 1
static errcode_t load_buffer(ext2_file_t file, int dontfill)
{
      ext2_filsys fs = file->fs;
      errcode_t   retval;

      if (!(file->flags & EXT2_FILE_BUF_VALID)) {
            retval = ext2fs_bmap(fs, file->ino, &file->inode,
                             BMAP_BUFFER, 0, file->blockno,
                             &file->physblock);
            if (retval)
                  return retval;
            if (!dontfill) {
                  if (file->physblock) {
                        retval = io_channel_read_blk(fs->io,
                                               file->physblock, 
                                               1, file->buf);
                        if (retval)
                              return retval;
                  } else
                        memset(file->buf, 0, fs->blocksize);
            }
            file->flags |= EXT2_FILE_BUF_VALID;
      }
      return 0;
}
      

errcode_t ext2fs_file_close(ext2_file_t file)
{
      errcode_t   retval;
      
      EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);

      retval = ext2fs_file_flush(file);
      
      if (file->buf)
            ext2fs_free_mem(&file->buf);
      ext2fs_free_mem(&file);

      return retval;
}


errcode_t ext2fs_file_read(ext2_file_t file, void *buf,
                     unsigned int wanted, unsigned int *got)
{
      ext2_filsys fs;
      errcode_t   retval = 0;
      unsigned int      start, c, count = 0;
      __u64       left;
      char        *ptr = (char *) buf;

      EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
      fs = file->fs;

      while ((file->pos < EXT2_I_SIZE(&file->inode)) && (wanted > 0)) {
            retval = sync_buffer_position(file);
            if (retval)
                  goto fail;
            retval = load_buffer(file, 0);
            if (retval)
                  goto fail;

            start = file->pos % fs->blocksize;
            c = fs->blocksize - start;
            if (c > wanted)
                  c = wanted;
            left = EXT2_I_SIZE(&file->inode) - file->pos ;
            if (c > left)
                  c = left;
      
            memcpy(ptr, file->buf+start, c);
            file->pos += c;
            ptr += c;
            count += c;
            wanted -= c;
      }
      
fail:
      if (got)
            *got = count;
      return retval;
}


errcode_t ext2fs_file_write(ext2_file_t file, const void *buf,
                      unsigned int nbytes, unsigned int *written)
{
      ext2_filsys fs;
      errcode_t   retval = 0;
      unsigned int      start, c, count = 0;
      const char  *ptr = (const char *) buf;

      EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
      fs = file->fs;

      if (!(file->flags & EXT2_FILE_WRITE))
            return EXT2_ET_FILE_RO;

      while (nbytes > 0) {
            retval = sync_buffer_position(file);
            if (retval)
                  goto fail;
            
            start = file->pos % fs->blocksize;
            c = fs->blocksize - start;
            if (c > nbytes)
                  c = nbytes;

            /*
             * We only need to do a read-modify-update cycle if
             * we're doing a partial write.
             */
            retval = load_buffer(file, (c == fs->blocksize));
            if (retval)
                  goto fail;

            file->flags |= EXT2_FILE_BUF_DIRTY;
            memcpy(file->buf+start, ptr, c);
            file->pos += c;
            ptr += c;
            count += c;
            nbytes -= c;
      }
      
fail:
      if (written)
            *written = count;
      return retval;
}

errcode_t ext2fs_file_llseek(ext2_file_t file, __u64 offset,
                      int whence, __u64 *ret_pos)
{
      EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);

      if (whence == EXT2_SEEK_SET)
            file->pos = offset;
      else if (whence == EXT2_SEEK_CUR)
            file->pos += offset;
      else if (whence == EXT2_SEEK_END)
            file->pos = EXT2_I_SIZE(&file->inode) + offset;
      else
            return EXT2_ET_INVALID_ARGUMENT;

      if (ret_pos)
            *ret_pos = file->pos;

      return 0;
}

errcode_t ext2fs_file_lseek(ext2_file_t file, ext2_off_t offset,
                      int whence, ext2_off_t *ret_pos)
{
      __u64       loffset, ret_loffset;
      errcode_t   retval;
      
      loffset = offset;
      retval = ext2fs_file_llseek(file, loffset, whence, &ret_loffset);
      if (ret_pos)
            *ret_pos = (ext2_off_t) ret_loffset;
      return retval;
}


/*
 * This function returns the size of the file, according to the inode
 */
errcode_t ext2fs_file_get_lsize(ext2_file_t file, __u64 *ret_size)
{
      if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
            return EXT2_ET_MAGIC_EXT2_FILE;
      *ret_size = EXT2_I_SIZE(&file->inode);
      return 0;
}

/*
 * This function returns the size of the file, according to the inode
 */
ext2_off_t ext2fs_file_get_size(ext2_file_t file)
{
      __u64 size;

      if (ext2fs_file_get_lsize(file, &size))
            return 0;
      if ((size >> 32) != 0)
            return 0;
      return size;
}

/*
 * This function sets the size of the file, truncating it if necessary
 * 
 * XXX still need to call truncate
 */
errcode_t ext2fs_file_set_size(ext2_file_t file, ext2_off_t size)
{
      errcode_t   retval;
      EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
      
      file->inode.i_size = size;
      file->inode.i_size_high = 0;
      if (file->ino) {
            retval = ext2fs_write_inode(file->fs, file->ino, &file->inode);
            if (retval)
                  return retval;
      }

      /* 
       * XXX truncate inode if necessary
       */

      return 0;
}

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