text: /*
   * ext_attr.c --- extended attribute blocks
   *
   * Copyright (C) 2001 Andreas Gruenbacher, <a.gruenbacher@computer.org>
   *
   * Copyright (C) 2002 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>
  #if HAVE_UNISTD_H
  #include <unistd.h>
  #endif
  #include <string.h>
  #include <time.h>
  
  #include "ext2_fs.h"
  #include "ext2_ext_attr.h"
  
  #include "ext2fs.h"
  
  #define NAME_HASH_SHIFT 5
  #define VALUE_HASH_SHIFT 16
  
  /*
   * ext2_xattr_hash_entry()
   *
   * Compute the hash of an extended attribute.
   */
  __u32 ext2fs_ext_attr_hash_entry(struct ext2_ext_attr_entry *entry, void *data)
  {
  	__u32 hash = 0;
  	char *name = ((char *) entry) + sizeof(struct ext2_ext_attr_entry);
  	int n;
  
  	for (n = 0; n < entry->e_name_len; n++) {
  		hash = (hash << NAME_HASH_SHIFT) ^
  		       (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
  		       *name++;
  	}
  
  	/* The hash needs to be calculated on the data in little-endian. */
  	if (entry->e_value_block == 0 && entry->e_value_size != 0) {
  		__u32 *value = (__u32 *)data;
  		for (n = (entry->e_value_size + EXT2_EXT_ATTR_ROUND) >>
  			 EXT2_EXT_ATTR_PAD_BITS; n; n--) {
  			hash = (hash << VALUE_HASH_SHIFT) ^
  			       (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
  			       ext2fs_le32_to_cpu(*value++);
  		}
  	}
  
  	return hash;
  }
  
  #undef NAME_HASH_SHIFT
  #undef VALUE_HASH_SHIFT
  
  errcode_t ext2fs_read_ext_attr(ext2_filsys fs, blk_t block, void *buf)
  {
  	errcode_t	retval;
  
   	retval = io_channel_read_blk(fs->io, block, 1, buf);
  	if (retval)
  		return retval;
  #ifdef WORDS_BIGENDIAN
  	ext2fs_swap_ext_attr(buf, buf, fs->blocksize, 1);
  #endif
  	return 0;
  }
  
  errcode_t ext2fs_write_ext_attr(ext2_filsys fs, blk_t block, void *inbuf)
  {
  	errcode_t	retval;
  	char		*write_buf;
  	char		*buf = NULL;
  
  #ifdef WORDS_BIGENDIAN
  	retval = ext2fs_get_mem(fs->blocksize, &buf);
  	if (retval)
  		return retval;
  	write_buf = buf;
  	ext2fs_swap_ext_attr(buf, inbuf, fs->blocksize, 1);
  #else
  	write_buf = (char *) inbuf;
  #endif
   	retval = io_channel_write_blk(fs->io, block, 1, write_buf);
  	if (buf)
  		ext2fs_free_mem(&buf);
  	if (!retval)
  		ext2fs_mark_changed(fs);
  	return retval;
  }
  
  /*
   * This function adjusts the reference count of the EA block.
   */
  errcode_t ext2fs_adjust_ea_refcount(ext2_filsys fs, blk_t blk,
  				    char *block_buf, int adjust,
  				    __u32 *newcount)
  {
  	errcode_t	retval;
  	struct ext2_ext_attr_header *header;
  	char	*buf = 0;
  
  	if ((blk >= fs->super->s_blocks_count) ||
  	    (blk < fs->super->s_first_data_block))
  		return EXT2_ET_BAD_EA_BLOCK_NUM;
  
  	if (!block_buf) {
  		retval = ext2fs_get_mem(fs->blocksize, &buf);
  		if (retval)
  			return retval;
  		block_buf = buf;
  	}
  
  	retval = ext2fs_read_ext_attr(fs, blk, block_buf);
  	if (retval)
  		goto errout;
  
  	header = (struct ext2_ext_attr_header *) block_buf;
  	header->h_refcount += adjust;
  	if (newcount)
  		*newcount = header->h_refcount;
  
  	retval = ext2fs_write_ext_attr(fs, blk, block_buf);
  	if (retval)
  		goto errout;
  
  errout:
  	if (buf)
  		ext2fs_free_mem(&buf);
  	return retval;
  }
  