/*
 * LZ4 - Fast LZ compression algorithm
 * Copyright (C) 2011 - 2016, Yann Collet.
 * BSD 2 - Clause License (http://www.opensource.org/licenses/bsd - license.php)
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *      * Redistributions of source code must retain the above copyright
 *        notice, this list of conditions and the following disclaimer.
 *      * 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 COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "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 COPYRIGHT
 * OWNER OR CONTRIBUTORS 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.
 * You can contact the author at :
 *      - LZ4 homepage : http://www.lz4.org
 *      - LZ4 source repository : https://github.com/lz4/lz4
 *
 *      Changed for kernel usage by:
 *      Sven Schmidt <4sschmid@informatik.uni-hamburg.de>
 */

/*-************************************
 *      Dependencies
 **************************************/
#include <linux/lz4.h>
#include "lz4defs.h"
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <asm/unaligned.h>

/*-*****************************
 *      Decompression functions
 *******************************/

#define DEBUGLOG(l, ...) {}     /* disabled */

#ifndef assert
#define assert(condition) ((void)0)
#endif

/*
 * LZ4_decompress_generic() :
 * This generic decompression function covers all use cases.
 * It shall be instantiated several times, using different sets of directives.
 * Note that it is important for performance that this function really get inlined,
 * in order to remove useless branches during compilation optimization.
 */
static FORCE_INLINE int LZ4_decompress_generic(
         const char * const src,
         char * const dst,
         int srcSize,
                /*
                 * If endOnInput == endOnInputSize,
                 * this value is `dstCapacity`
                 */
         int outputSize,
         /* endOnOutputSize, endOnInputSize */
         endCondition_directive endOnInput,
         /* full, partial */
         earlyEnd_directive partialDecoding,
         /* noDict, withPrefix64k, usingExtDict */
         dict_directive dict,
         /* always <= dst, == dst when no prefix */
         const BYTE * const lowPrefix,
         /* only if dict == usingExtDict */
         const BYTE * const dictStart,
         /* note : = 0 if noDict */
         const size_t dictSize
         )
{
        const BYTE *ip = (const BYTE *) src;
        const BYTE * const iend = ip + srcSize;

        BYTE *op = (BYTE *) dst;
        BYTE * const oend = op + outputSize;
        BYTE *cpy;

        const BYTE * const dictEnd = (const BYTE *)dictStart + dictSize;
        static const unsigned int inc32table[8] = {0, 1, 2, 1, 0, 4, 4, 4};
        static const int dec64table[8] = {0, 0, 0, -1, -4, 1, 2, 3};

        const int safeDecode = (endOnInput == endOnInputSize);
        const int checkOffset = ((safeDecode) && (dictSize < (int)(64 * KB)));

        /* Set up the "end" pointers for the shortcut. */
        const BYTE *const shortiend = iend -
                (endOnInput ? 14 : 8) /*maxLL*/ - 2 /*offset*/;
        const BYTE *const shortoend = oend -
                (endOnInput ? 14 : 8) /*maxLL*/ - 18 /*maxML*/;

        DEBUGLOG(5, "%s (srcSize:%i, dstSize:%i)", __func__,
                 srcSize, outputSize);

        /* Special cases */
        assert(lowPrefix <= op);
        assert(src != NULL);

        /* Empty output buffer */
        if ((endOnInput) && (unlikely(outputSize == 0)))
                return ((srcSize == 1) && (*ip == 0)) ? 0 : -1;

        if ((!endOnInput) && (unlikely(outputSize == 0)))
                return (*ip == 0 ? 1 : -1);

        if ((endOnInput) && unlikely(srcSize == 0))
                return -1;

        /* Main Loop : decode sequences */
        while (1) {
                size_t length;
                const BYTE *match;
                size_t offset;

                /* get literal length */
                unsigned int const token = *ip++;
                length = token>>ML_BITS;

                /* ip < iend before the increment */
                assert(!endOnInput || ip <= iend);

                /*
                 * A two-stage shortcut for the most common case:
                 * 1) If the literal length is 0..14, and there is enough
                 * space, enter the shortcut and copy 16 bytes on behalf
                 * of the literals (in the fast mode, only 8 bytes can be
                 * safely copied this way).
                 * 2) Further if the match length is 4..18, copy 18 bytes
                 * in a similar manner; but we ensure that there's enough
                 * space in the output for those 18 bytes earlier, upon
                 * entering the shortcut (in other words, there is a
                 * combined check for both stages).
                 */
                if ((endOnInput ? length != RUN_MASK : length <= 8)
                   /*
                    * strictly "less than" on input, to re-enter
                    * the loop with at least one byte
                    */
                   && likely((endOnInput ? ip < shortiend : 1) &
                             (op <= shortoend))) {
                        /* Copy the literals */
                        memcpy(op, ip, endOnInput ? 16 : 8);
                        op += length; ip += length;

                        /*
                         * The second stage:
                         * prepare for match copying, decode full info.
                         * If it doesn't work out, the info won't be wasted.
                         */
                        length = token & ML_MASK; /* match length */
                        offset = LZ4_readLE16(ip);
                        ip += 2;
                        match = op - offset;
                        assert(match <= op); /* check overflow */

                        /* Do not deal with overlapping matches. */
                        if ((length != ML_MASK) &&
                            (offset >= 8) &&
                            (dict == withPrefix64k || match >= lowPrefix)) {
                                /* Copy the match. */
                                memcpy(op + 0, match + 0, 8);
                                memcpy(op + 8, match + 8, 8);
                                memcpy(op + 16, match + 16, 2);
                                op += length + MINMATCH;
                                /* Both stages worked, load the next token. */
                                continue;
                        }

                        /*
                         * The second stage didn't work out, but the info
                         * is ready. Propel it right to the point of match
                         * copying.
                         */
                        goto _copy_match;
                }

                /* decode literal length */
                if (length == RUN_MASK) {
                        unsigned int s;

                        if (unlikely(endOnInput ? ip >= iend - RUN_MASK : 0)) {
                                /* overflow detection */
                                goto _output_error;
                        }
                        do {
                                s = *ip++;
                                length += s;
                        } while (likely(endOnInput
                                ? ip < iend - RUN_MASK
                                : 1) & (s == 255));

                        if ((safeDecode)
                            && unlikely((uptrval)(op) +
                                        length < (uptrval)(op))) {
                                /* overflow detection */
                                goto _output_error;
                        }
                        if ((safeDecode)
                            && unlikely((uptrval)(ip) +
                                        length < (uptrval)(ip))) {
                                /* overflow detection */
                                goto _output_error;
                        }
                }

                /* copy literals */
                cpy = op + length;
                LZ4_STATIC_ASSERT(MFLIMIT >= WILDCOPYLENGTH);

                if (((endOnInput) && ((cpy > oend - MFLIMIT)
                        || (ip + length > iend - (2 + 1 + LASTLITERALS))))
                        || ((!endOnInput) && (cpy > oend - WILDCOPYLENGTH))) {
                        if (partialDecoding) {
                                if (cpy > oend) {
                                        /*
                                         * Partial decoding :
                                         * stop in the middle of literal segment
                                         */
                                        cpy = oend;
                                        length = oend - op;
                                }
                                if ((endOnInput)
                                        && (ip + length > iend)) {
                                        /*
                                         * Error :
                                         * read attempt beyond
                                         * end of input buffer
                                         */
                                        goto _output_error;
                                }
                        } else {
                                if ((!endOnInput)
                                        && (cpy != oend)) {
                                        /*
                                         * Error :
                                         * block decoding must
                                         * stop exactly there
                                         */
                                        goto _output_error;
                                }
                                if ((endOnInput)
                                        && ((ip + length != iend)
                                        || (cpy > oend))) {
                                        /*
                                         * Error :
                                         * input must be consumed
                                         */
                                        goto _output_error;
                                }
                        }

                        memcpy(op, ip, length);
                        ip += length;
                        op += length;

                        /* Necessarily EOF, due to parsing restrictions */
                        if (!partialDecoding || (cpy == oend))
                                break;
                } else {
                        /* may overwrite up to WILDCOPYLENGTH beyond cpy */
                        LZ4_wildCopy(op, ip, cpy);
                        ip += length;
                        op = cpy;
                }

                /* get offset */
                offset = LZ4_readLE16(ip);
                ip += 2;
                match = op - offset;

                /* get matchlength */
                length = token & ML_MASK;

_copy_match:
                if ((checkOffset) && (unlikely(match + dictSize < lowPrefix))) {
                        /* Error : offset outside buffers */
                        goto _output_error;
                }

                /* costs ~1%; silence an msan warning when offset == 0 */
                /*
                 * note : when partialDecoding, there is no guarantee that
                 * at least 4 bytes remain available in output buffer
                 */
                if (!partialDecoding) {
                        assert(oend > op);
                        assert(oend - op >= 4);

                        LZ4_write32(op, (U32)offset);
                }

                if (length == ML_MASK) {
                        unsigned int s;

                        do {
                                s = *ip++;

                                if ((endOnInput) && (ip > iend - LASTLITERALS))
                                        goto _output_error;

                                length += s;
                        } while (s == 255);

                        if ((safeDecode)
                                && unlikely(
                                        (uptrval)(op) + length < (uptrval)op)) {
                                /* overflow detection */
                                goto _output_error;
                        }
                }

                length += MINMATCH;

                /* match starting within external dictionary */
                if ((dict == usingExtDict) && (match < lowPrefix)) {
                        if (unlikely(op + length > oend - LASTLITERALS)) {
                                /* doesn't respect parsing restriction */
                                if (!partialDecoding)
                                        goto _output_error;
                                length = min(length, (size_t)(oend - op));
                        }

                        if (length <= (size_t)(lowPrefix - match)) {
                                /*
                                 * match fits entirely within external
                                 * dictionary : just copy
                                 */
                                memmove(op, dictEnd - (lowPrefix - match),
                                        length);
                                op += length;
                        } else {
                                /*
                                 * match stretches into both external
                                 * dictionary and current block
                                 */
                                size_t const copySize = (size_t)(lowPrefix - match);
                                size_t const restSize = length - copySize;

                                memcpy(op, dictEnd - copySize, copySize);
                                op += copySize;
                                if (restSize > (size_t)(op - lowPrefix)) {
                                        /* overlap copy */
                                        BYTE * const endOfMatch = op + restSize;
                                        const BYTE *copyFrom = lowPrefix;

                                        while (op < endOfMatch)
                                                *op++ = *copyFrom++;
                                } else {
                                        memcpy(op, lowPrefix, restSize);
                                        op += restSize;
                                }
                        }
                        continue;
                }

                /* copy match within block */
                cpy = op + length;

                /*
                 * partialDecoding :
                 * may not respect endBlock parsing restrictions
                 */
                assert(op <= oend);
                if (partialDecoding &&
                    (cpy > oend - MATCH_SAFEGUARD_DISTANCE)) {
                        size_t const mlen = min(length, (size_t)(oend - op));
                        const BYTE * const matchEnd = match + mlen;
                        BYTE * const copyEnd = op + mlen;

                        if (matchEnd > op) {
                                /* overlap copy */
                                while (op < copyEnd)
                                        *op++ = *match++;
                        } else {
                                memcpy(op, match, mlen);
                        }
                        op = copyEnd;
                        if (op == oend)
                                break;
                        continue;
                }

                if (unlikely(offset < 8)) {
                        op[0] = match[0];
                        op[1] = match[1];
                        op[2] = match[2];
                        op[3] = match[3];
                        match += inc32table[offset];
                        memcpy(op + 4, match, 4);
                        match -= dec64table[offset];
                } else {
                        LZ4_copy8(op, match);
                        match += 8;
                }

                op += 8;

                if (unlikely(cpy > oend - MATCH_SAFEGUARD_DISTANCE)) {
                        BYTE * const oCopyLimit = oend - (WILDCOPYLENGTH - 1);

                        if (cpy > oend - LASTLITERALS) {
                                /*
                                 * Error : last LASTLITERALS bytes
                                 * must be literals (uncompressed)
                                 */
                                goto _output_error;
                        }

                        if (op < oCopyLimit) {
                                LZ4_wildCopy(op, match, oCopyLimit);
                                match += oCopyLimit - op;
                                op = oCopyLimit;
                        }
                        while (op < cpy)
                                *op++ = *match++;
                } else {
                        LZ4_copy8(op, match);
                        if (length > 16)
                                LZ4_wildCopy(op + 8, match + 8, cpy);
                }
                op = cpy; /* wildcopy correction */
        }

        /* end of decoding */
        if (endOnInput) {
                /* Nb of output bytes decoded */
                return (int) (((char *)op) - dst);
        } else {
                /* Nb of input bytes read */
                return (int) (((const char *)ip) - src);
        }

        /* Overflow error detected */
_output_error:
        return (int) (-(((const char *)ip) - src)) - 1;
}

int LZ4_decompress_safe(const char *source, char *dest,
        int compressedSize, int maxDecompressedSize)
{
        return LZ4_decompress_generic(source, dest,
                                      compressedSize, maxDecompressedSize,
                                      endOnInputSize, decode_full_block,
                                      noDict, (BYTE *)dest, NULL, 0);
}

int LZ4_decompress_safe_partial(const char *src, char *dst,
        int compressedSize, int targetOutputSize, int dstCapacity)
{
        dstCapacity = min(targetOutputSize, dstCapacity);
        return LZ4_decompress_generic(src, dst, compressedSize, dstCapacity,
                                      endOnInputSize, partial_decode,
                                      noDict, (BYTE *)dst, NULL, 0);
}

int LZ4_decompress_fast(const char *source, char *dest, int originalSize)
{
        return LZ4_decompress_generic(source, dest, 0, originalSize,
                                      endOnOutputSize, decode_full_block,
                                      withPrefix64k,
                                      (BYTE *)dest - 64 * KB, NULL, 0);
}

/* ===== Instantiate a few more decoding cases, used more than once. ===== */

int LZ4_decompress_safe_withPrefix64k(const char *source, char *dest,
                                      int compressedSize, int maxOutputSize)
{
        return LZ4_decompress_generic(source, dest,
                                      compressedSize, maxOutputSize,
                                      endOnInputSize, decode_full_block,
                                      withPrefix64k,
                                      (BYTE *)dest - 64 * KB, NULL, 0);
}

static int LZ4_decompress_safe_withSmallPrefix(const char *source, char *dest,
                                               int compressedSize,
                                               int maxOutputSize,
                                               size_t prefixSize)
{
        return LZ4_decompress_generic(source, dest,
                                      compressedSize, maxOutputSize,
                                      endOnInputSize, decode_full_block,
                                      noDict,
                                      (BYTE *)dest - prefixSize, NULL, 0);
}

int LZ4_decompress_safe_forceExtDict(const char *source, char *dest,
                                     int compressedSize, int maxOutputSize,
                                     const void *dictStart, size_t dictSize)
{
        return LZ4_decompress_generic(source, dest,
                                      compressedSize, maxOutputSize,
                                      endOnInputSize, decode_full_block,
                                      usingExtDict, (BYTE *)dest,
                                      (const BYTE *)dictStart, dictSize);
}

static int LZ4_decompress_fast_extDict(const char *source, char *dest,
                                       int originalSize,
                                       const void *dictStart, size_t dictSize)
{
        return LZ4_decompress_generic(source, dest,
                                      0, originalSize,
                                      endOnOutputSize, decode_full_block,
                                      usingExtDict, (BYTE *)dest,
                                      (const BYTE *)dictStart, dictSize);
}

/*
 * The "double dictionary" mode, for use with e.g. ring buffers: the first part
 * of the dictionary is passed as prefix, and the second via dictStart + dictSize.
 * These routines are used only once, in LZ4_decompress_*_continue().
 */
static FORCE_INLINE
int LZ4_decompress_safe_doubleDict(const char *source, char *dest,
                                   int compressedSize, int maxOutputSize,
                                   size_t prefixSize,
                                   const void *dictStart, size_t dictSize)
{
        return LZ4_decompress_generic(source, dest,
                                      compressedSize, maxOutputSize,
                                      endOnInputSize, decode_full_block,
                                      usingExtDict, (BYTE *)dest - prefixSize,
                                      (const BYTE *)dictStart, dictSize);
}

static FORCE_INLINE
int LZ4_decompress_fast_doubleDict(const char *source, char *dest,
                                   int originalSize, size_t prefixSize,
                                   const void *dictStart, size_t dictSize)
{
        return LZ4_decompress_generic(source, dest,
                                      0, originalSize,
                                      endOnOutputSize, decode_full_block,
                                      usingExtDict, (BYTE *)dest - prefixSize,
                                      (const BYTE *)dictStart, dictSize);
}

/* ===== streaming decompression functions ===== */

int LZ4_setStreamDecode(LZ4_streamDecode_t *LZ4_streamDecode,
        const char *dictionary, int dictSize)
{
        LZ4_streamDecode_t_internal *lz4sd =
                &LZ4_streamDecode->internal_donotuse;

        lz4sd->prefixSize = (size_t) dictSize;
        lz4sd->prefixEnd = (const BYTE *) dictionary + dictSize;
        lz4sd->externalDict = NULL;
        lz4sd->extDictSize      = 0;
        return 1;
}

/*
 * *_continue() :
 * These decoding functions allow decompression of multiple blocks
 * in "streaming" mode.
 * Previously decoded blocks must still be available at the memory
 * position where they were decoded.
 * If it's not possible, save the relevant part of
 * decoded data into a safe buffer,
 * and indicate where it stands using LZ4_setStreamDecode()
 */
int LZ4_decompress_safe_continue(LZ4_streamDecode_t *LZ4_streamDecode,
        const char *source, char *dest, int compressedSize, int maxOutputSize)
{
        LZ4_streamDecode_t_internal *lz4sd =
                &LZ4_streamDecode->internal_donotuse;
        int result;

        if (lz4sd->prefixSize == 0) {
                /* The first call, no dictionary yet. */
                assert(lz4sd->extDictSize == 0);
                result = LZ4_decompress_safe(source, dest,
                        compressedSize, maxOutputSize);
                if (result <= 0)
                        return result;
                lz4sd->prefixSize = result;
                lz4sd->prefixEnd = (BYTE *)dest + result;
        } else if (lz4sd->prefixEnd == (BYTE *)dest) {
                /* They're rolling the current segment. */
                if (lz4sd->prefixSize >= 64 * KB - 1)
                        result = LZ4_decompress_safe_withPrefix64k(source, dest,
                                compressedSize, maxOutputSize);
                else if (lz4sd->extDictSize == 0)
                        result = LZ4_decompress_safe_withSmallPrefix(source,
                                dest, compressedSize, maxOutputSize,
                                lz4sd->prefixSize);
                else
                        result = LZ4_decompress_safe_doubleDict(source, dest,
                                compressedSize, maxOutputSize,
                                lz4sd->prefixSize,
                                lz4sd->externalDict, lz4sd->extDictSize);
                if (result <= 0)
                        return result;
                lz4sd->prefixSize += result;
                lz4sd->prefixEnd  += result;
        } else {
                /*
                 * The buffer wraps around, or they're
                 * switching to another buffer.
                 */
                lz4sd->extDictSize = lz4sd->prefixSize;
                lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
                result = LZ4_decompress_safe_forceExtDict(source, dest,
                        compressedSize, maxOutputSize,
                        lz4sd->externalDict, lz4sd->extDictSize);
                if (result <= 0)
                        return result;
                lz4sd->prefixSize = result;
                lz4sd->prefixEnd  = (BYTE *)dest + result;
        }

        return result;
}

int LZ4_decompress_fast_continue(LZ4_streamDecode_t *LZ4_streamDecode,
        const char *source, char *dest, int originalSize)
{
        LZ4_streamDecode_t_internal *lz4sd = &LZ4_streamDecode->internal_donotuse;
        int result;

        if (lz4sd->prefixSize == 0) {
                assert(lz4sd->extDictSize == 0);
                result = LZ4_decompress_fast(source, dest, originalSize);
                if (result <= 0)
                        return result;
                lz4sd->prefixSize = originalSize;
                lz4sd->prefixEnd = (BYTE *)dest + originalSize;
        } else if (lz4sd->prefixEnd == (BYTE *)dest) {
                if (lz4sd->prefixSize >= 64 * KB - 1 ||
                    lz4sd->extDictSize == 0)
                        result = LZ4_decompress_fast(source, dest,
                                                     originalSize);
                else
                        result = LZ4_decompress_fast_doubleDict(source, dest,
                                originalSize, lz4sd->prefixSize,
                                lz4sd->externalDict, lz4sd->extDictSize);
                if (result <= 0)
                        return result;
                lz4sd->prefixSize += originalSize;
                lz4sd->prefixEnd  += originalSize;
        } else {
                lz4sd->extDictSize = lz4sd->prefixSize;
                lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
                result = LZ4_decompress_fast_extDict(source, dest,
                        originalSize, lz4sd->externalDict, lz4sd->extDictSize);
                if (result <= 0)
                        return result;
                lz4sd->prefixSize = originalSize;
                lz4sd->prefixEnd = (BYTE *)dest + originalSize;
        }
        return result;
}

int LZ4_decompress_safe_usingDict(const char *source, char *dest,
                                  int compressedSize, int maxOutputSize,
                                  const char *dictStart, int dictSize)
{
        if (dictSize == 0)
                return LZ4_decompress_safe(source, dest,
                                           compressedSize, maxOutputSize);
        if (dictStart+dictSize == dest) {
                if (dictSize >= 64 * KB - 1)
                        return LZ4_decompress_safe_withPrefix64k(source, dest,
                                compressedSize, maxOutputSize);
                return LZ4_decompress_safe_withSmallPrefix(source, dest,
                        compressedSize, maxOutputSize, dictSize);
        }
        return LZ4_decompress_safe_forceExtDict(source, dest,
                compressedSize, maxOutputSize, dictStart, dictSize);
}

int LZ4_decompress_fast_usingDict(const char *source, char *dest,
                                  int originalSize,
                                  const char *dictStart, int dictSize)
{
        if (dictSize == 0 || dictStart + dictSize == dest)
                return LZ4_decompress_fast(source, dest, originalSize);

        return LZ4_decompress_fast_extDict(source, dest, originalSize,
                dictStart, dictSize);
}

#ifndef STATIC
EXPORT_SYMBOL(LZ4_decompress_safe);
EXPORT_SYMBOL(LZ4_decompress_safe_partial);
EXPORT_SYMBOL(LZ4_decompress_fast);
EXPORT_SYMBOL(LZ4_setStreamDecode);
EXPORT_SYMBOL(LZ4_decompress_safe_continue);
EXPORT_SYMBOL(LZ4_decompress_fast_continue);
EXPORT_SYMBOL(LZ4_decompress_safe_usingDict);
EXPORT_SYMBOL(LZ4_decompress_fast_usingDict);

MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("LZ4 decompressor");
#endif