/*      $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);
}