/*
 * Squashfs - a compressed read only filesystem for Linux
 *
 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
 * Phillip Lougher <phillip@squashfs.org.uk>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2,
 * or (at your option) any later version.
 *
 * 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 License
 * along with this program; if not, write to the Free Software
 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * xz_wrapper.c
 */


#include <linux/mutex.h>
#include <linux/buffer_head.h>
#include <linux/slab.h>
#include <linux/xz.h>
#include <linux/bitops.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs.h"
#include "decompressor.h"
#include "page_actor.h"

struct squashfs_xz {
        struct xz_dec *state;
        struct xz_buf buf;
};

struct disk_comp_opts {
        __le32 dictionary_size;
        __le32 flags;
};

struct comp_opts {
        int dict_size;
};

static void *squashfs_xz_comp_opts(struct squashfs_sb_info *msblk,
        void *buff, int len)
{
        struct disk_comp_opts *comp_opts = buff;
        struct comp_opts *opts;
        int err = 0, n;

        opts = kmalloc(sizeof(*opts), GFP_KERNEL);
        if (opts == NULL) {
                err = -ENOMEM;
                goto out2;
        }

        if (comp_opts) {
                /* check compressor options are the expected length */
                if (len < sizeof(*comp_opts)) {
                        err = -EIO;
                        goto out;
                }

                opts->dict_size = le32_to_cpu(comp_opts->dictionary_size);

                /* the dictionary size should be 2^n or 2^n+2^(n+1) */
                n = ffs(opts->dict_size) - 1;
                if (opts->dict_size != (1 << n) && opts->dict_size != (1 << n) +
                                                (1 << (n + 1))) {
                        err = -EIO;
                        goto out;
                }
        } else
                /* use defaults */
                opts->dict_size = max_t(int, msblk->block_size,
                                                        SQUASHFS_METADATA_SIZE);

        return opts;

out:
        kfree(opts);
out2:
        return ERR_PTR(err);
}


static void *squashfs_xz_init(struct squashfs_sb_info *msblk, void *buff)
{
        struct comp_opts *comp_opts = buff;
        struct squashfs_xz *stream;
        int err;

        stream = kmalloc(sizeof(*stream), GFP_KERNEL);
        if (stream == NULL) {
                err = -ENOMEM;
                goto failed;
        }

        stream->state = xz_dec_init(XZ_PREALLOC, comp_opts->dict_size);
        if (stream->state == NULL) {
                kfree(stream);
                err = -ENOMEM;
                goto failed;
        }

        return stream;

failed:
        ERROR("Failed to initialise xz decompressor\n");
        return ERR_PTR(err);
}


static void squashfs_xz_free(void *strm)
{
        struct squashfs_xz *stream = strm;

        if (stream) {
                xz_dec_end(stream->state);
                kfree(stream);
        }
}


static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void *strm,
        struct buffer_head **bh, int b, int offset, int length,
        struct squashfs_page_actor *output)
{
        enum xz_ret xz_err;
        int avail, total = 0, k = 0;
        struct squashfs_xz *stream = strm;

        xz_dec_reset(stream->state);
        stream->buf.in_pos = 0;
        stream->buf.in_size = 0;
        stream->buf.out_pos = 0;
        stream->buf.out_size = PAGE_SIZE;
        stream->buf.out = squashfs_first_page(output);

        do {
                if (stream->buf.in_pos == stream->buf.in_size && k < b) {
                        avail = min(length, msblk->devblksize - offset);
                        length -= avail;
                        stream->buf.in = bh[k]->b_data + offset;
                        stream->buf.in_size = avail;
                        stream->buf.in_pos = 0;
                        offset = 0;
                }

                if (stream->buf.out_pos == stream->buf.out_size) {
                        stream->buf.out = squashfs_next_page(output);
                        if (stream->buf.out != NULL) {
                                stream->buf.out_pos = 0;
                                total += PAGE_SIZE;
                        }
                }

                xz_err = xz_dec_run(stream->state, &stream->buf);

                if (stream->buf.in_pos == stream->buf.in_size && k < b)
                        put_bh(bh[k++]);
        } while (xz_err == XZ_OK);

        squashfs_finish_page(output);

        if (xz_err != XZ_STREAM_END || k < b)
                goto out;

        return total + stream->buf.out_pos;

out:
        for (; k < b; k++)
                put_bh(bh[k]);

        return -EIO;
}

const struct squashfs_decompressor squashfs_xz_comp_ops = {
        .init = squashfs_xz_init,
        .comp_opts = squashfs_xz_comp_opts,
        .free = squashfs_xz_free,
        .decompress = squashfs_xz_uncompress,
        .id = XZ_COMPRESSION,
        .name = "xz",
        .supported = 1
};