/*      $NetBSD: rawfs.c,v 1.8 2009/10/21 23:12:10 snj Exp $    */

/*
* Copyright (c) 1995 Gordon W. Ross
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

/*
* Raw file system - for stream devices like tapes.
* No random access, only sequential read allowed.
* This exists only to allow upper level code to be
* shielded from the fact that the device must be
* read only with whole block position and size.
*/

#include <sys/param.h>
#include <stand.h>

#include "rawfs.h"

extern int debug;

/* Our devices are generally willing to do 8K transfers. */
#define RAWFS_BSIZE     0x2000

/*
* In-core open file.
*/
struct file {
       daddr_t         fs_nextblk;     /* block number to read next */
       off_t           fs_off;         /* seek offset in file */
       int             fs_len;         /* amount left in f_buf */
       char *          fs_ptr;         /* read pointer into f_buf */
       char            fs_buf[RAWFS_BSIZE];
};

static int rawfs_get_block(struct open_file *);

int
rawfs_open(const char *path, struct open_file *f)
{
       struct file *fs;

       /*
        * The actual PROM driver has already been opened.
        * Just allocate the I/O buffer, etc.
        */
       fs = alloc(sizeof(struct file));
       fs->fs_nextblk = 0;
       fs->fs_off = 0;
       fs->fs_len = 0;
       fs->fs_ptr = fs->fs_buf;

#ifdef  DEBUG_RAWFS
       printf("rawfs_open: fs=0x%x\n", fs);
#endif

       f->f_fsdata = fs;
       return (0);
}

int
rawfs_close(struct open_file *f)
{
       struct file *fs;

       fs = (struct file *) f->f_fsdata;
       f->f_fsdata = NULL;

#ifdef  DEBUG_RAWFS
       if (debug) {
               printf("rawfs_close: breakpoint...", fs->fs_buf);
               __asm ("        trap #0");
       }
#endif

       if (fs != NULL)
               dealloc(fs, sizeof(*fs));

       return (0);
}

int
rawfs_read(struct open_file *f, void *start, u_int size, u_int *resid)
{
       struct file *fs = (struct file *)f->f_fsdata;
       char *addr = start;
       int error = 0;
       size_t csize;

       while (size != 0) {
               if (fs->fs_len == 0)
                       if ((error = rawfs_get_block(f)) != 0)
                               break;

               if (fs->fs_len <= 0)
                       break;  /* EOF */

               csize = size;
               if (csize > fs->fs_len)
                       csize = fs->fs_len;

               memcpy(addr, fs->fs_ptr, csize);
               fs->fs_off += csize;
               fs->fs_ptr += csize;
               fs->fs_len -= csize;
               addr += csize;
               size -= csize;
       }
       if (resid)
               *resid = size;
       return (error);
}

int
rawfs_write(struct open_file *f, void *start, size_t size, size_t *resid)
{
#ifdef  DEBUG_RAWFS
       panic("rawfs_write");
#endif
       return (EROFS);
}

off_t
rawfs_seek(struct open_file *f, off_t offset, int where)
{
       struct file *fs = (struct file *)f->f_fsdata;
       off_t csize;

       switch (where) {
       case SEEK_SET:
               offset -= fs->fs_off;
               /* FALLTHROUGH */
       case SEEK_CUR:
               if (offset >= 0)
                       break;
               /* FALLTHROUGH */
       case SEEK_END:
       default:
               return (-1);
       }

       while (offset != 0) {

               if (fs->fs_len == 0)
                       if (rawfs_get_block(f) != 0)
                               return (-1);

               if (fs->fs_len <= 0)
                       break;  /* EOF */

               csize = offset;
               if (csize > fs->fs_len)
                       csize = fs->fs_len;

               fs->fs_off += csize;
               fs->fs_ptr += csize;
               fs->fs_len -= csize;
               offset -= csize;
       }
       return (fs->fs_off);
}

int
rawfs_stat(struct open_file *f, struct stat *sb)
{
#ifdef  DEBUG_RAWFS
       panic("rawfs_stat");
#endif
       return (EFTYPE);
}


/*
* Read a block from the underlying stream device
* (In our case, a tape drive.)
*/
static int
rawfs_get_block(struct open_file *f)
{
       struct file *fs;
       size_t len;
       int error;

       fs = (struct file *)f->f_fsdata;
       fs->fs_ptr = fs->fs_buf;

       twiddle();
       error = f->f_dev->dv_strategy(f->f_devdata, F_READ,
               fs->fs_nextblk, RAWFS_BSIZE,    fs->fs_buf, &len);

       if (!error) {
               fs->fs_len = len;
               fs->fs_nextblk += (RAWFS_BSIZE / DEV_BSIZE);
       }

       return (error);
}