#if 0
#
# This LD_PRELOAD-able module keeps buffers [passed to /dev/raw/...]
# aligned according to 'man raw'. Maintaining appropriate blocking
# factor is still up to the application this module will be
# LD_PRELOAD-ed to. Most common example would most likely be:
#
#  env LD_PRELOAD=`pwd`/aligned_io.so tar cBbf 64 /dev/raw/raw1 ...
#
/bin/sh << EOS
MODNAME=\`basename "$0" .c\`
(set -x; gcc -O -fomit-frame-pointer -fPIC -shared -o \$MODNAME.so "$0")
[ $# -gt 0 ] && (set -x; env LD_PRELOAD=`pwd`/\$MODNAME.so $*)
EOS
exit
#
#endif

#ifndef __linux
# error "Linux only, at least for the moment..."
#endif

#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <unistd.h>

#define ALIGN	2048
#define ASIZE	(32*1024)
#ifndef DEBUG
#define DEBUG	0
#endif

static void  *aligned_buffer;

typedef ssize_t (*io_op) (int fd,void *buf,size_t count);
extern ssize_t __write(int fd, void *buf, size_t count);
extern ssize_t __read(int fd, void *buf, size_t count);

static ssize_t do_io (io_op op,int fd,void *buf,size_t count)
{ int ret;
#if DEBUG
    fprintf (stderr,"-%d:%p\n",fd,buf);
#endif
    if ((size_t)buf&(ALIGN-1))
    {	if (aligned_buffer == NULL)
	   aligned_buffer = mmap (NULL,ASIZE,PROT_READ|PROT_WRITE,
					MAP_PRIVATE|MAP_ANON,-1,0);
#if DEBUG
	fprintf (stderr,"+%d:%p\n",fd,aligned_buffer);
#endif
	/* I count on caller to notice that the return value is smaller */
	if (count>ASIZE) count=ASIZE;
	if (op==__write) memcpy (aligned_buffer,buf,count);
	ret=(*op) (fd,aligned_buffer,count);
	if (op==__read && ret>0) memcpy (buf,aligned_buffer,ret);
	return ret;
    }
    return (*op) (fd,buf,count);
}

ssize_t write(int fd, const void *buf, size_t count)
{   return do_io (__write,fd,(void *)buf,count);   }

ssize_t read(int fd, void *buf, size_t count)
{   return do_io (__read,fd,buf,count);   }