/*
 * LZO decompressor for the Linux kernel. Code borrowed from the lzo
 * implementation by Markus Franz Xaver Johannes Oberhumer.
 *
 * Linux kernel adaptation:
 * Copyright (C) 2009
 * Albin Tonnerre, Free Electrons <albin.tonnerre@free-electrons.com>
 *
 * Original code:
 * Copyright (C) 1996-2005 Markus Franz Xaver Johannes Oberhumer
 * All Rights Reserved.
 *
 * lzop and the LZO library are free software; you can redistribute them
 * and/or modify them under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, 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; see the file COPYING.
 * If not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Markus F.X.J. Oberhumer
 * <markus@oberhumer.com>
 * http://www.oberhumer.com/opensource/lzop/
 */

#ifdef STATIC
#include "lzo/lzo1x_decompress.c"
#else
#include <linux/decompress/unlzo.h>
#endif

#include <linux/types.h>
#include <linux/lzo.h>
#include <linux/decompress/mm.h>

#include <linux/compiler.h>
#include <asm/unaligned.h>

static const unsigned char lzop_magic[] = {
        0x89, 0x4c, 0x5a, 0x4f, 0x00, 0x0d, 0x0a, 0x1a, 0x0a };

#define LZO_BLOCK_SIZE        (256*1024l)
#define HEADER_HAS_FILTER      0x00000800L
#define HEADER_SIZE_MIN       (9 + 7     + 4 + 8     + 1       + 4)
#define HEADER_SIZE_MAX       (9 + 7 + 1 + 8 + 8 + 4 + 1 + 255 + 4)

STATIC inline int INIT parse_header(u8 *input, int *skip, int in_len)
{
        int l;
        u8 *parse = input;
        u8 *end = input + in_len;
        u8 level = 0;
        u16 version;

        /*
         * Check that there's enough input to possibly have a valid header.
         * Then it is possible to parse several fields until the minimum
         * size may have been used.
         */
        if (in_len < HEADER_SIZE_MIN)
                return 0;

        /* read magic: 9 first bits */
        for (l = 0; l < 9; l++) {
                if (*parse++ != lzop_magic[l])
                        return 0;
        }
        /* get version (2bytes), skip library version (2),
         * 'need to be extracted' version (2) and
         * method (1) */
        version = get_unaligned_be16(parse);
        parse += 7;
        if (version >= 0x0940)
                level = *parse++;
        if (get_unaligned_be32(parse) & HEADER_HAS_FILTER)
                parse += 8; /* flags + filter info */
        else
                parse += 4; /* flags */

        /*
         * At least mode, mtime_low, filename length, and checksum must
         * be left to be parsed. If also mtime_high is present, it's OK
         * because the next input buffer check is after reading the
         * filename length.
         */
        if (end - parse < 8 + 1 + 4)
                return 0;

        /* skip mode and mtime_low */
        parse += 8;
        if (version >= 0x0940)
                parse += 4;     /* skip mtime_high */

        l = *parse++;
        /* don't care about the file name, and skip checksum */
        if (end - parse < l + 4)
                return 0;
        parse += l + 4;

        *skip = parse - input;
        return 1;
}

STATIC inline int INIT unlzo(u8 *input, int in_len,
                                int (*fill) (void *, unsigned int),
                                int (*flush) (void *, unsigned int),
                                u8 *output, int *posp,
                                void (*error) (char *x))
{
        u8 r = 0;
        int skip = 0;
        u32 src_len, dst_len;
        size_t tmp;
        u8 *in_buf, *in_buf_save, *out_buf;
        int ret = -1;

        if (output) {
                out_buf = output;
        } else if (!flush) {
                error("NULL output pointer and no flush function provided");
                goto exit;
        } else {
                out_buf = malloc(LZO_BLOCK_SIZE);
                if (!out_buf) {
                        error("Could not allocate output buffer");
                        goto exit;
                }
        }

        if (input && fill) {
                error("Both input pointer and fill function provided, don't know what to do");
                goto exit_1;
        } else if (input) {
                in_buf = input;
        } else if (!fill) {
                error("NULL input pointer and missing fill function");
                goto exit_1;
        } else {
                in_buf = malloc(lzo1x_worst_compress(LZO_BLOCK_SIZE));
                if (!in_buf) {
                        error("Could not allocate input buffer");
                        goto exit_1;
                }
        }
        in_buf_save = in_buf;

        if (posp)
                *posp = 0;

        if (fill) {
                /*
                 * Start from in_buf + HEADER_SIZE_MAX to make it possible
                 * to use memcpy() to copy the unused data to the beginning
                 * of the buffer. This way memmove() isn't needed which
                 * is missing from pre-boot environments of most archs.
                 */
                in_buf += HEADER_SIZE_MAX;
                in_len = fill(in_buf, HEADER_SIZE_MAX);
        }

        if (!parse_header(in_buf, &skip, in_len)) {
                error("invalid header");
                goto exit_2;
        }
        in_buf += skip;
        in_len -= skip;

        if (fill) {
                /* Move the unused data to the beginning of the buffer. */
                memcpy(in_buf_save, in_buf, in_len);
                in_buf = in_buf_save;
        }

        if (posp)
                *posp = skip;

        for (;;) {
                /* read uncompressed block size */
                if (fill && in_len < 4) {
                        skip = fill(in_buf + in_len, 4 - in_len);
                        if (skip > 0)
                                in_len += skip;
                }
                if (in_len < 4) {
                        error("file corrupted");
                        goto exit_2;
                }
                dst_len = get_unaligned_be32(in_buf);
                in_buf += 4;
                in_len -= 4;

                /* exit if last block */
                if (dst_len == 0) {
                        if (posp)
                                *posp += 4;
                        break;
                }

                if (dst_len > LZO_BLOCK_SIZE) {
                        error("dest len longer than block size");
                        goto exit_2;
                }

                /* read compressed block size, and skip block checksum info */
                if (fill && in_len < 8) {
                        skip = fill(in_buf + in_len, 8 - in_len);
                        if (skip > 0)
                                in_len += skip;
                }
                if (in_len < 8) {
                        error("file corrupted");
                        goto exit_2;
                }
                src_len = get_unaligned_be32(in_buf);
                in_buf += 8;
                in_len -= 8;

                if (src_len <= 0 || src_len > dst_len) {
                        error("file corrupted");
                        goto exit_2;
                }

                /* decompress */
                if (fill && in_len < src_len) {
                        skip = fill(in_buf + in_len, src_len - in_len);
                        if (skip > 0)
                                in_len += skip;
                }
                if (in_len < src_len) {
                        error("file corrupted");
                        goto exit_2;
                }
                tmp = dst_len;

                /* When the input data is not compressed at all,
                 * lzo1x_decompress_safe will fail, so call memcpy()
                 * instead */
                if (unlikely(dst_len == src_len))
                        memcpy(out_buf, in_buf, src_len);
                else {
                        r = lzo1x_decompress_safe((u8 *) in_buf, src_len,
                                                out_buf, &tmp);

                        if (r != LZO_E_OK || dst_len != tmp) {
                                error("Compressed data violation");
                                goto exit_2;
                        }
                }

                if (flush && flush(out_buf, dst_len) != dst_len)
                        goto exit_2;
                if (output)
                        out_buf += dst_len;
                if (posp)
                        *posp += src_len + 12;

                in_buf += src_len;
                in_len -= src_len;
                if (fill) {
                        /*
                         * If there happens to still be unused data left in
                         * in_buf, move it to the beginning of the buffer.
                         * Use a loop to avoid memmove() dependency.
                         */
                        if (in_len > 0)
                                for (skip = 0; skip < in_len; ++skip)
                                        in_buf_save[skip] = in_buf[skip];
                        in_buf = in_buf_save;
                }
        }

        ret = 0;
exit_2:
        if (!input)
                free(in_buf);
exit_1:
        if (!output)
                free(out_buf);
exit:
        return ret;
}

#define decompress unlzo