// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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>
 *
 * xz_wrapper.c
 */


#include <linux/mutex.h>
#include <linux/bio.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_obj(*opts);
        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_obj(*stream);
        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 bio *bio, int offset, int length,
        struct squashfs_page_actor *output)
{
        struct bvec_iter_all iter_all = {};
        struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
        int total = 0, error = 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);
        if (IS_ERR(stream->buf.out)) {
                error = PTR_ERR(stream->buf.out);
                goto finish;
        }

        for (;;) {
                enum xz_ret xz_err;

                if (stream->buf.in_pos == stream->buf.in_size) {
                        const void *data;
                        int avail;

                        if (!bio_next_segment(bio, &iter_all)) {
                                /* XZ_STREAM_END must be reached. */
                                error = -EIO;
                                break;
                        }

                        avail = min(length, ((int)bvec->bv_len) - offset);
                        data = bvec_virt(bvec);
                        length -= avail;
                        stream->buf.in = 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 (IS_ERR(stream->buf.out)) {
                                error = PTR_ERR(stream->buf.out);
                                break;
                        } else if (stream->buf.out != NULL) {
                                stream->buf.out_pos = 0;
                                total += PAGE_SIZE;
                        }
                }

                xz_err = xz_dec_run(stream->state, &stream->buf);
                if (xz_err == XZ_STREAM_END)
                        break;
                if (xz_err != XZ_OK) {
                        error = -EIO;
                        break;
                }
        }

finish:
        squashfs_finish_page(output);

        return error ? error : total + stream->buf.out_pos;
}

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",
        .alloc_buffer = 1,
        .supported = 1
};