/*
   * bvec iterator
   *
   * Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   *
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public Licens
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
   */
  #ifndef __LINUX_BVEC_ITER_H
  #define __LINUX_BVEC_ITER_H

  #include <linux/kernel.h>
  #include <linux/bug.h>
  
  /*
   * was unsigned short, but we might as well be ready for > 64kB I/O pages
   */
  struct bio_vec {
  	struct page	*bv_page;
  	unsigned int	bv_len;
  	unsigned int	bv_offset;
  };
  
  struct bvec_iter {
  	sector_t		bi_sector;	/* device address in 512 byte
  						   sectors */
  	unsigned int		bi_size;	/* residual I/O count */
  
  	unsigned int		bi_idx;		/* current index into bvl_vec */
  
  	unsigned int            bi_bvec_done;	/* number of bytes completed in
  						   current bvec */
  };

  
  /*
   * various member access, note that bio_data should of course not be used
   * on highmem page vectors
   */
  #define __bvec_iter_bvec(bvec, iter)	(&(bvec)[(iter).bi_idx])
  
  #define bvec_iter_page(bvec, iter)				\
  	(__bvec_iter_bvec((bvec), (iter))->bv_page)
  
  #define bvec_iter_len(bvec, iter)				\
  	min((iter).bi_size,					\
  	    __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
  
  #define bvec_iter_offset(bvec, iter)				\
  	(__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
  
  #define bvec_iter_bvec(bvec, iter)				\
  ((struct bio_vec) {						\
  	.bv_page	= bvec_iter_page((bvec), (iter)),	\
  	.bv_len		= bvec_iter_len((bvec), (iter)),	\
  	.bv_offset	= bvec_iter_offset((bvec), (iter)),	\
  })

  static inline void bvec_iter_advance(const struct bio_vec *bv,
  				     struct bvec_iter *iter,

  				     unsigned bytes)
  {
  	WARN_ONCE(bytes > iter->bi_size,
  		  "Attempted to advance past end of bvec iter
  ");
  
  	while (bytes) {

  		unsigned iter_len = bvec_iter_len(bv, *iter);
  		unsigned len = min(bytes, iter_len);

  
  		bytes -= len;
  		iter->bi_size -= len;
  		iter->bi_bvec_done += len;
  
  		if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
  			iter->bi_bvec_done = 0;
  			iter->bi_idx++;
  		}
  	}
  }
  
  #define for_each_bvec(bvl, bio_vec, iter, start)			\
  	for (iter = (start);						\
  	     (iter).bi_size &&						\
  		((bvl = bvec_iter_bvec((bio_vec), (iter))), 1);	\
  	     bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
  
  #endif /* __LINUX_BVEC_ITER_H */