lib/ext2fs/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 Library
 * General Public License, version 2.
 * %End-Header%
 */

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

#include "ext2_fs.h"
#include "ext2fs.h"
#include "ext2fsP.h"

struct ext2_file {
	errcode_t		magic;
	ext2_filsys 		fs;
	ext2_ino_t		ino;
	struct ext2_inode	inode;
	int 			flags;
	__u64			pos;
	blk64_t			blockno;
	blk64_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_array(3, fs->blocksize, &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 returns the pointer to the inode of a file from the structure
 */
struct ext2_inode *ext2fs_file_get_inode(ext2_file_t file)
{
	if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
		return NULL;
	return &file->inode;
}

/* This function returns the inode number from the structure */
ext2_ino_t ext2fs_file_get_inode_num(ext2_file_t file)
{
	if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
		return 0;
	return file->ino;
}

/*
 * 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_bmap2(fs, file->ino, &file->inode,
				     BMAP_BUFFER, file->ino ? BMAP_ALLOC : 0,
				     file->blockno, 0, &file->physblock);
		if (retval)
			return retval;
	}

	retval = io_channel_write_blk64(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)
{
	blk64_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_bmap2(fs, file->ino, &file->inode,
				     BMAP_BUFFER, 0, file->blockno, 0,
				     &file->physblock);
		if (retval)
			return retval;
		if (!dontfill) {
			if (file->physblock) {
				retval = io_channel_read_blk64(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;

		/*
		 * OK, the physical block hasn't been allocated yet.
		 * Allocate it.
		 */
		if (!file->physblock) {
			retval = ext2fs_bmap2(fs, file->ino, &file->inode,
					      BMAP_BUFFER,
					      file->ino ? BMAP_ALLOC : 0,
					      file->blockno, 0,
					      &file->physblock);
			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:
	/* Update inode size */
	if (count != 0 && EXT2_I_SIZE(&file->inode) < file->pos) {
		errcode_t	rc;

		rc = ext2fs_file_set_size2(file, file->pos);
		if (retval == 0)
			retval = rc;
	}

	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;
}

/* Zero the parts of the last block that are past EOF. */
static errcode_t ext2fs_file_zero_past_offset(ext2_file_t file,
					      ext2_off64_t offset)
{
	ext2_filsys fs = file->fs;
	char *b = NULL;
	ext2_off64_t off = offset % fs->blocksize;
	blk64_t blk;
	int ret_flags;
	errcode_t retval;

	if (off == 0)
		return 0;

	retval = sync_buffer_position(file);
	if (retval)
		return retval;

	/* Is there an initialized block at the end? */
	retval = ext2fs_bmap2(fs, file->ino, NULL, NULL, 0,
			      offset / fs->blocksize, &ret_flags, &blk);
	if (retval)
		return retval;
	if ((blk == 0) || (ret_flags & BMAP_RET_UNINIT))
		return 0;

	/* Zero to the end of the block */
	retval = ext2fs_get_mem(fs->blocksize, &b);
	if (retval)
		return retval;

	/* Read/zero/write block */
	retval = io_channel_read_blk64(fs->io, blk, 1, b);
	if (retval)
		goto out;

	memset(b + off, 0, fs->blocksize - off);

	retval = io_channel_write_blk64(fs->io, blk, 1, b);
	if (retval)
		goto out;

out:
	ext2fs_free_mem(&b);
	return retval;
}

/*
 * This function sets the size of the file, truncating it if necessary
 *
 */
errcode_t ext2fs_file_set_size2(ext2_file_t file, ext2_off64_t size)
{
	ext2_off64_t	old_size;
	errcode_t	retval;
	blk64_t		old_truncate, truncate_block;

	EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);

	if (size && ext2fs_file_block_offset_too_big(file->fs, &file->inode,
					(size - 1) / file->fs->blocksize))
		return EXT2_ET_FILE_TOO_BIG;
	truncate_block = ((size + file->fs->blocksize - 1) >>
			  EXT2_BLOCK_SIZE_BITS(file->fs->super));
	old_size = EXT2_I_SIZE(&file->inode);
	old_truncate = ((old_size + file->fs->blocksize - 1) >>
		      EXT2_BLOCK_SIZE_BITS(file->fs->super));

	/* If we're writing a large file, set the large_file flag */
	if (LINUX_S_ISREG(file->inode.i_mode) &&
	    ext2fs_needs_large_file_feature(EXT2_I_SIZE(&file->inode)) &&
	    (!EXT2_HAS_RO_COMPAT_FEATURE(file->fs->super,
					 EXT2_FEATURE_RO_COMPAT_LARGE_FILE) ||
	     file->fs->super->s_rev_level == EXT2_GOOD_OLD_REV)) {
		file->fs->super->s_feature_ro_compat |=
				EXT2_FEATURE_RO_COMPAT_LARGE_FILE;
		ext2fs_update_dynamic_rev(file->fs);
		ext2fs_mark_super_dirty(file->fs);
	}

	file->inode.i_size = size & 0xffffffff;
	file->inode.i_size_high = (size >> 32);
	if (file->ino) {
		retval = ext2fs_write_inode(file->fs, file->ino, &file->inode);
		if (retval)
			return retval;
	}

	retval = ext2fs_file_zero_past_offset(file, size);
	if (retval)
		return retval;

	if (truncate_block >= old_truncate)
		return 0;

	return ext2fs_punch(file->fs, file->ino, &file->inode, 0,
			    truncate_block, ~0ULL);
}

errcode_t ext2fs_file_set_size(ext2_file_t file, ext2_off_t size)
{
	return ext2fs_file_set_size2(file, size);
}