/*
 * LZ4 - Fast LZ compression algorithm
 * Header File
 * Copyright (C) 2011-2013, 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://fastcompression.blogspot.com/p/lz4.html
 * - LZ4 source repository : http://code.google.com/p/lz4/
 */
/*
 * Copyright (c) 2016 by Delphix. All rights reserved.
 * Copyright 2020 OmniOS Community Edition (OmniOSce) Association.
 */

#if defined(_KERNEL) || defined(_FAKE_KERNEL)
#include <sys/zfs_context.h>
#elif defined(_STANDALONE)
#include <sys/cdefs.h>
#include <stand.h>
#include <sys/types.h>
#include <sys/endian.h>
#include <assert.h>

#define ASSERT  assert
#else
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/sysmacros.h>
#include <netinet/in.h>
#include <assert.h>

#define ASSERT  assert
#endif
#include <lz4.h>

static int real_LZ4_compress(const char *source, char *dest, int isize,
    int osize);
static int LZ4_uncompress_unknownOutputSize(const char *source, char *dest,
    int isize, int maxOutputSize);
static int LZ4_compressCtx(void *ctx, const char *source, char *dest,
    int isize, int osize);
static int LZ4_compress64kCtx(void *ctx, const char *source, char *dest,
    int isize, int osize);

size_t
lz4_compress(void *s_start, void *d_start, size_t s_len, size_t d_len,
    int n __unused)
{
        uint32_t bufsiz;
        char *dest = d_start;

        ASSERT(d_len >= sizeof (bufsiz));

        bufsiz = real_LZ4_compress(s_start, &dest[sizeof (bufsiz)], s_len,
            d_len - sizeof (bufsiz));

        /* Signal an error if the compression routine returned zero. */
        if (bufsiz == 0)
                return (s_len);

        /*
         * Encode the compresed buffer size at the start. We'll need this in
         * decompression to counter the effects of padding which might be
         * added to the compressed buffer and which, if unhandled, would
         * confuse the hell out of our decompression function.
         */
#if defined(_KERNEL) || defined(_FAKE_KERNEL)
        *(uint32_t *)(void *)dest = BE_32(bufsiz);
#else
        *(uint32_t *)(void *)dest = htonl(bufsiz);
#endif

        return (bufsiz + sizeof (bufsiz));
}

int
lz4_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len,
    int n __unused)
{
        const char *src = s_start;
#if defined(_KERNEL) || defined(_FAKE_KERNEL)
        uint32_t bufsiz = BE_IN32(s_start);
#else
        uint32_t bufsiz = htonl(*(uint32_t *)s_start);
#endif

        /* invalid compressed buffer size encoded at start */
        if (bufsiz + sizeof (bufsiz) > s_len)
                return (1);

        /*
         * Returns 0 on success (decompression function returned non-negative)
         * and non-zero on failure (decompression function returned negative).
         */
        return (LZ4_uncompress_unknownOutputSize(&src[sizeof (bufsiz)],
            d_start, bufsiz, d_len) < 0);
}

/*
 * LZ4 API Description:
 *
 * Simple Functions:
 * real_LZ4_compress() :
 *      isize  : is the input size. Max supported value is ~1.9GB
 *      return : the number of bytes written in buffer dest
 *               or 0 if the compression fails (if LZ4_COMPRESSMIN is set).
 *      note : destination buffer must be already allocated.
 *              destination buffer must be sized to handle worst cases
 *              situations (input data not compressible).
 *
 * Advanced Functions
 *
 * LZ4_compressBound() :
 *      Provides the maximum size that LZ4 may output in a "worst case"
 *      scenario (input data not compressible) primarily useful for memory
 *      allocation of output buffer.
 *
 *      isize  : is the input size. Max supported value is ~1.9GB
 *      return : maximum output size in a "worst case" scenario
 *      note : this function is limited by "int" range (2^31-1)
 *
 * LZ4_uncompress_unknownOutputSize() :
 *      isize  : is the input size, therefore the compressed size
 *      maxOutputSize : is the size of the destination buffer (which must be
 *              already allocated)
 *      return : the number of bytes decoded in the destination buffer
 *              (necessarily <= maxOutputSize). If the source stream is
 *              malformed, the function will stop decoding and return a
 *              negative result, indicating the byte position of the faulty
 *              instruction. This function never writes beyond dest +
 *              maxOutputSize, and is therefore protected against malicious
 *              data packets.
 *      note   : Destination buffer must be already allocated.
 *
 * LZ4_compressCtx() :
 *      This function explicitly handles the CTX memory structure.
 *
 *      ILLUMOS CHANGES: the CTX memory structure must be explicitly allocated
 *      by the caller (either on the stack or using kmem_zalloc). Passing NULL
 *      isn't valid.
 *
 * LZ4_compress64kCtx() :
 *      Same as LZ4_compressCtx(), but specific to small inputs (<64KB).
 *      isize *Must* be <64KB, otherwise the output will be corrupted.
 *
 *      ILLUMOS CHANGES: the CTX memory structure must be explicitly allocated
 *      by the caller (either on the stack or using kmem_zalloc). Passing NULL
 *      isn't valid.
 */

/*
 * Tuning parameters
 */

/*
 * COMPRESSIONLEVEL: Increasing this value improves compression ratio
 *       Lowering this value reduces memory usage. Reduced memory usage
 *      typically improves speed, due to cache effect (ex: L1 32KB for Intel,
 *      L1 64KB for AMD). Memory usage formula : N->2^(N+2) Bytes
 *      (examples : 12 -> 16KB ; 17 -> 512KB)
 */
#define COMPRESSIONLEVEL 12

/*
 * NOTCOMPRESSIBLE_CONFIRMATION: Decreasing this value will make the
 *      algorithm skip faster data segments considered "incompressible".
 *      This may decrease compression ratio dramatically, but will be
 *      faster on incompressible data. Increasing this value will make
 *      the algorithm search more before declaring a segment "incompressible".
 *      This could improve compression a bit, but will be slower on
 *      incompressible data. The default value (6) is recommended.
 */
#define NOTCOMPRESSIBLE_CONFIRMATION 6

/*
 * BIG_ENDIAN_NATIVE_BUT_INCOMPATIBLE: This will provide a boost to
 * performance for big endian cpu, but the resulting compressed stream
 * will be incompatible with little-endian CPU. You can set this option
 * to 1 in situations where data will stay within closed environment.
 * This option is useless on Little_Endian CPU (such as x86).
 */
/* #define      BIG_ENDIAN_NATIVE_BUT_INCOMPATIBLE 1 */

/*
 * CPU Feature Detection
 */

/* 32 or 64 bits ? */
#if (defined(__x86_64__) || defined(__x86_64) || defined(__amd64__) || \
    defined(__amd64) || defined(__ppc64__) || defined(_WIN64) || \
    defined(__LP64__) || defined(_LP64))
#define LZ4_ARCH64 1
#else
#define LZ4_ARCH64 0
#endif

/*
 * Limits the amount of stack space that the algorithm may consume to hold
 * the compression lookup table. The value `9' here means we'll never use
 * more than 2k of stack (see above for a description of COMPRESSIONLEVEL).
 * If more memory is needed, it is allocated from the heap.
 */
#define STACKLIMIT 9

/*
 * Little Endian or Big Endian?
 * Note: overwrite the below #define if you know your architecture endianess.
 */
#if defined(BYTE_ORDER)
#if BYTE_ORDER == BIG_ENDIAN    /* This is sys/endian.h API */
#define LZ4_BIG_ENDIAN 1
#else
/*
 * Little Endian assumed. PDP Endian and other very rare endian format
 * are unsupported.
 */
#endif
#else /* !defined(BYTE_ORDER) */
#if (defined(__BIG_ENDIAN__) || defined(__BIG_ENDIAN) || \
        defined(_BIG_ENDIAN) || defined(_ARCH_PPC) || defined(__PPC__) || \
        defined(__PPC) || defined(PPC) || defined(__powerpc__) || \
        defined(__powerpc) || defined(powerpc) || \
        ((defined(__BYTE_ORDER__)&&(__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__))))
#define LZ4_BIG_ENDIAN 1
#else
/*
 * Little Endian assumed. PDP Endian and other very rare endian format
 * are unsupported.
 */
#endif
#endif /* defined(BYTE_ORDER) */

/*
 * Unaligned memory access is automatically enabled for "common" CPU,
 * such as x86. For others CPU, the compiler will be more cautious, and
 * insert extra code to ensure aligned access is respected. If you know
 * your target CPU supports unaligned memory access, you may want to
 * force this option manually to improve performance
 */
#if defined(__ARM_FEATURE_UNALIGNED)
#define LZ4_FORCE_UNALIGNED_ACCESS 1
#endif

#ifdef __sparc
#define LZ4_FORCE_SW_BITCOUNT
#endif

/*
 * Compiler Options
 */
#if __STDC_VERSION__ >= 199901L /* C99 */
/* "restrict" is a known keyword */
#else
/* Disable restrict */
#define restrict
#endif

#define GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)

#ifdef _MSC_VER
/* Visual Studio */
/* Visual is not C99, but supports some kind of inline */
#define inline __forceinline
#if LZ4_ARCH64
/* For Visual 2005 */
#pragma intrinsic(_BitScanForward64)
#pragma intrinsic(_BitScanReverse64)
#else /* !LZ4_ARCH64 */
/* For Visual 2005 */
#pragma intrinsic(_BitScanForward)
#pragma intrinsic(_BitScanReverse)
#endif /* !LZ4_ARCH64 */
#endif /* _MSC_VER */

#ifdef _MSC_VER
#define lz4_bswap16(x) _byteswap_ushort(x)
#else /* !_MSC_VER */
#define lz4_bswap16(x) ((unsigned short int) ((((x) >> 8) & 0xffu) | \
        (((x) & 0xffu) << 8)))
#endif /* !_MSC_VER */

#if (GCC_VERSION >= 302) || (__INTEL_COMPILER >= 800) || defined(__clang__)
#define expect(expr, value)    (__builtin_expect((expr), (value)))
#else
#define expect(expr, value)    (expr)
#endif

#ifndef likely
#define likely(expr)    expect((expr) != 0, 1)
#endif

#ifndef unlikely
#define unlikely(expr)  expect((expr) != 0, 0)
#endif

/* Basic types */
#if defined(_MSC_VER)
/* Visual Studio does not support 'stdint' natively */
#define BYTE    unsigned __int8
#define U16     unsigned __int16
#define U32     unsigned __int32
#define S32     __int32
#define U64     unsigned __int64
#else /* !defined(_MSC_VER) */
#define BYTE    uint8_t
#define U16     uint16_t
#define U32     uint32_t
#define S32     int32_t
#define U64     uint64_t
#endif /* !defined(_MSC_VER) */

#ifndef LZ4_FORCE_UNALIGNED_ACCESS
#pragma pack(1)
#endif

typedef struct _U16_S {
        U16 v;
} U16_S;
typedef struct _U32_S {
        U32 v;
} U32_S;
typedef struct _U64_S {
        U64 v;
} U64_S;

#ifndef LZ4_FORCE_UNALIGNED_ACCESS
#pragma pack()
#endif

#define A64(x) (((U64_S *)(__DECONST(void *, x)))->v)
#define A32(x) (((U32_S *)(__DECONST(void *, x)))->v)
#define A16(x) (((U16_S *)(__DECONST(void *, x)))->v)

/*
 * Constants
 */
#define MINMATCH 4

#define HASH_LOG COMPRESSIONLEVEL
#define HASHTABLESIZE (1 << HASH_LOG)
#define HASH_MASK (HASHTABLESIZE - 1)

#define SKIPSTRENGTH (NOTCOMPRESSIBLE_CONFIRMATION > 2 ? \
        NOTCOMPRESSIBLE_CONFIRMATION : 2)

/*
 * Defines if memory is allocated into the stack (local variable),
 * or into the heap (kmem_alloc()).
 */
#define HEAPMODE (HASH_LOG > STACKLIMIT)
#define COPYLENGTH 8
#define LASTLITERALS 5
#define MFLIMIT (COPYLENGTH + MINMATCH)
#define MINLENGTH (MFLIMIT + 1)

#define MAXD_LOG 16
#define MAX_DISTANCE ((1 << MAXD_LOG) - 1)

#define ML_BITS 4
#define ML_MASK ((1U<<ML_BITS)-1)
#define RUN_BITS (8-ML_BITS)
#define RUN_MASK ((1U<<RUN_BITS)-1)


/*
 * Architecture-specific macros
 */
#if LZ4_ARCH64
#define STEPSIZE 8
#define UARCH U64
#define AARCH A64
#define LZ4_COPYSTEP(s, d)      A64(d) = A64(s); d += 8; s += 8;
#define LZ4_COPYPACKET(s, d)    LZ4_COPYSTEP(s, d)
#define LZ4_SECURECOPY(s, d, e) if (d < e) LZ4_WILDCOPY(s, d, e)
#define HTYPE U32
#define INITBASE(base)          const BYTE* const base = ip
#else /* !LZ4_ARCH64 */
#define STEPSIZE 4
#define UARCH U32
#define AARCH A32
#define LZ4_COPYSTEP(s, d)      A32(d) = A32(s); d += 4; s += 4;
#define LZ4_COPYPACKET(s, d)    LZ4_COPYSTEP(s, d); LZ4_COPYSTEP(s, d);
#define LZ4_SECURECOPY          LZ4_WILDCOPY
#define HTYPE const BYTE *
#define INITBASE(base)          const int base = 0
#endif /* !LZ4_ARCH64 */

#if (defined(LZ4_BIG_ENDIAN) && !defined(BIG_ENDIAN_NATIVE_BUT_INCOMPATIBLE))
#define LZ4_READ_LITTLEENDIAN_16(d, s, p) \
        { U16 v = A16(p); v = lz4_bswap16(v); d = (s) - v; }
#define LZ4_WRITE_LITTLEENDIAN_16(p, i) \
        { U16 v = (U16)(i); v = lz4_bswap16(v); A16(p) = v; p += 2; }
#else
#define LZ4_READ_LITTLEENDIAN_16(d, s, p) { d = (s) - A16(p); }
#define LZ4_WRITE_LITTLEENDIAN_16(p, v)  { A16(p) = v; p += 2; }
#endif


/* Local structures */
struct refTables {
        HTYPE hashTable[HASHTABLESIZE];
};


/* Macros */
#define LZ4_HASH_FUNCTION(i) (((i) * 2654435761U) >> ((MINMATCH * 8) - \
        HASH_LOG))
#define LZ4_HASH_VALUE(p) LZ4_HASH_FUNCTION(A32(p))
#define LZ4_WILDCOPY(s, d, e) do { LZ4_COPYPACKET(s, d) } while (d < e);
#define LZ4_BLINDCOPY(s, d, l) { BYTE* e = (d) + l; LZ4_WILDCOPY(s, d, e); \
        d = e; }


/* Private functions */
#if LZ4_ARCH64

static inline int
LZ4_NbCommonBytes(register U64 val)
{
#if defined(LZ4_BIG_ENDIAN)
#if defined(_MSC_VER) && !defined(LZ4_FORCE_SW_BITCOUNT)
        unsigned long r = 0;
        _BitScanReverse64(&r, val);
        return (int)(r >> 3);
#elif defined(__GNUC__) && (GCC_VERSION >= 304) && \
        !defined(LZ4_FORCE_SW_BITCOUNT)
        return (__builtin_clzll(val) >> 3);
#else
        int r;
        if (!(val >> 32)) {
                r = 4;
        } else {
                r = 0;
                val >>= 32;
        }
        if (!(val >> 16)) {
                r += 2;
                val >>= 8;
        } else {
                val >>= 24;
        }
        r += (!val);
        return (r);
#endif
#else
#if defined(_MSC_VER) && !defined(LZ4_FORCE_SW_BITCOUNT)
        unsigned long r = 0;
        _BitScanForward64(&r, val);
        return (int)(r >> 3);
#elif defined(__GNUC__) && (GCC_VERSION >= 304) && \
        !defined(LZ4_FORCE_SW_BITCOUNT)
        return (__builtin_ctzll(val) >> 3);
#else
        static const int DeBruijnBytePos[64] =
            { 0, 0, 0, 0, 0, 1, 1, 2, 0, 3, 1, 3, 1, 4, 2, 7, 0, 2, 3, 6, 1, 5,
                3, 5, 1, 3, 4, 4, 2, 5, 6, 7, 7, 0, 1, 2, 3, 3, 4, 6, 2, 6, 5,
                5, 3, 4, 5, 6, 7, 1, 2, 4, 6, 4,
                4, 5, 7, 2, 6, 5, 7, 6, 7, 7
        };
        return DeBruijnBytePos[((U64) ((val & -val) * 0x0218A392CDABBD3F)) >>
            58];
#endif
#endif
}

#else

static inline int
LZ4_NbCommonBytes(register U32 val)
{
#if defined(LZ4_BIG_ENDIAN)
#if defined(_MSC_VER) && !defined(LZ4_FORCE_SW_BITCOUNT)
        unsigned long r = 0;
        _BitScanReverse(&r, val);
        return (int)(r >> 3);
#elif defined(__GNUC__) && (GCC_VERSION >= 304) && \
        !defined(LZ4_FORCE_SW_BITCOUNT)
        return (__builtin_clz(val) >> 3);
#else
        int r;
        if (!(val >> 16)) {
                r = 2;
                val >>= 8;
        } else {
                r = 0;
                val >>= 24;
        }
        r += (!val);
        return (r);
#endif
#else
#if defined(_MSC_VER) && !defined(LZ4_FORCE_SW_BITCOUNT)
        unsigned long r = 0;
        _BitScanForward(&r, val);
        return (int)(r >> 3);
#elif defined(__GNUC__) && (GCC_VERSION >= 304) && \
        !defined(LZ4_FORCE_SW_BITCOUNT)
        return (__builtin_ctz(val) >> 3);
#else
        static const int DeBruijnBytePos[32] = {
                0, 0, 3, 0, 3, 1, 3, 0,
                3, 2, 2, 1, 3, 2, 0, 1,
                3, 3, 1, 2, 2, 2, 2, 0,
                3, 1, 2, 0, 1, 0, 1, 1
        };
        return DeBruijnBytePos[((U32) ((val & -(S32) val) * 0x077CB531U)) >>
            27];
#endif
#endif
}

#endif

/* Compression functions */

/*ARGSUSED*/
static int
LZ4_compressCtx(void *ctx, const char *source, char *dest, int isize,
    int osize)
{
#if HEAPMODE
        struct refTables *srt = (struct refTables *)ctx;
        HTYPE *HashTable = (HTYPE *) (srt->hashTable);
#else
        HTYPE HashTable[HASHTABLESIZE] = { 0 };
#endif

        const BYTE *ip = (const BYTE *) source;
        INITBASE(base);
        const BYTE *anchor = ip;
        const BYTE *const iend = ip + isize;
        const BYTE *const oend = (BYTE *) dest + osize;
        const BYTE *const mflimit = iend - MFLIMIT;
#define matchlimit (iend - LASTLITERALS)

        BYTE *op = (BYTE *) dest;

        int len, length;
        const int skipStrength = SKIPSTRENGTH;
        U32 forwardH;


        /* Init */
        if (isize < MINLENGTH)
                goto _last_literals;

        /* First Byte */
        HashTable[LZ4_HASH_VALUE(ip)] = ip - base;
        ip++;
        forwardH = LZ4_HASH_VALUE(ip);

        /* Main Loop */
        for (;;) {
                int findMatchAttempts = (1U << skipStrength) + 3;
                const BYTE *forwardIp = ip;
                const BYTE *ref;
                BYTE *token;

                /* Find a match */
                do {
                        U32 h = forwardH;
                        int step = findMatchAttempts++ >> skipStrength;
                        ip = forwardIp;
                        forwardIp = ip + step;

                        if unlikely(forwardIp > mflimit) {
                                goto _last_literals;
                        }

                        forwardH = LZ4_HASH_VALUE(forwardIp);
                        ref = base + HashTable[h];
                        HashTable[h] = ip - base;

                } while ((ref < ip - MAX_DISTANCE) || (A32(ref) != A32(ip)));

                /* Catch up */
                while ((ip > anchor) && (ref > (const BYTE *) source) &&
                    unlikely(ip[-1] == ref[-1])) {
                        ip--;
                        ref--;
                }

                /* Encode Literal length */
                length = ip - anchor;
                token = op++;

                /* Check output limit */
                if unlikely(op + length + (2 + 1 + LASTLITERALS) +
                    (length >> 8) > oend)
                        return (0);

                if (length >= (int)RUN_MASK) {
                        *token = (RUN_MASK << ML_BITS);
                        len = length - RUN_MASK;
                        for (; len > 254; len -= 255)
                                *op++ = 255;
                        *op++ = (BYTE)len;
                } else
                        *token = (length << ML_BITS);

                /* Copy Literals */
                LZ4_BLINDCOPY(anchor, op, length);

                _next_match:
                /* Encode Offset */
                LZ4_WRITE_LITTLEENDIAN_16(op, ip - ref);

                /* Start Counting */
                ip += MINMATCH;
                ref += MINMATCH;        /* MinMatch verified */
                anchor = ip;
                while likely(ip < matchlimit - (STEPSIZE - 1)) {
                        UARCH diff = AARCH(ref) ^ AARCH(ip);
                        if (!diff) {
                                ip += STEPSIZE;
                                ref += STEPSIZE;
                                continue;
                        }
                        ip += LZ4_NbCommonBytes(diff);
                        goto _endCount;
                }
#if LZ4_ARCH64
                if ((ip < (matchlimit - 3)) && (A32(ref) == A32(ip))) {
                        ip += 4;
                        ref += 4;
                }
#endif
                if ((ip < (matchlimit - 1)) && (A16(ref) == A16(ip))) {
                        ip += 2;
                        ref += 2;
                }
                if ((ip < matchlimit) && (*ref == *ip))
                        ip++;
                _endCount:

                /* Encode MatchLength */
                len = (ip - anchor);
                /* Check output limit */
                if unlikely(op + (1 + LASTLITERALS) + (len >> 8) > oend)
                        return (0);
                if (len >= (int)ML_MASK) {
                        *token += ML_MASK;
                        len -= ML_MASK;
                        for (; len > 509; len -= 510) {
                                *op++ = 255;
                                *op++ = 255;
                        }
                        if (len > 254) {
                                len -= 255;
                                *op++ = 255;
                        }
                        *op++ = (BYTE)len;
                } else
                        *token += len;

                /* Test end of chunk */
                if (ip > mflimit) {
                        anchor = ip;
                        break;
                }
                /* Fill table */
                HashTable[LZ4_HASH_VALUE(ip - 2)] = ip - 2 - base;

                /* Test next position */
                ref = base + HashTable[LZ4_HASH_VALUE(ip)];
                HashTable[LZ4_HASH_VALUE(ip)] = ip - base;
                if ((ref > ip - (MAX_DISTANCE + 1)) && (A32(ref) == A32(ip))) {
                        token = op++;
                        *token = 0;
                        goto _next_match;
                }
                /* Prepare next loop */
                anchor = ip++;
                forwardH = LZ4_HASH_VALUE(ip);
        }

        _last_literals:
        /* Encode Last Literals */
        {
                int lastRun = iend - anchor;
                if (op + lastRun + 1 + ((lastRun + 255 - RUN_MASK) / 255) >
                    oend)
                        return (0);
                if (lastRun >= (int)RUN_MASK) {
                        *op++ = (RUN_MASK << ML_BITS);
                        lastRun -= RUN_MASK;
                        for (; lastRun > 254; lastRun -= 255) {
                                *op++ = 255;
                        }
                        *op++ = (BYTE)lastRun;
                } else
                        *op++ = (lastRun << ML_BITS);
                (void) memcpy(op, anchor, iend - anchor);
                op += iend - anchor;
        }

        /* End */
        return (int)(((char *)op) - dest);
}



/* Note : this function is valid only if isize < LZ4_64KLIMIT */
#define LZ4_64KLIMIT ((1 << 16) + (MFLIMIT - 1))
#define HASHLOG64K (HASH_LOG + 1)
#define HASH64KTABLESIZE (1U << HASHLOG64K)
#define LZ4_HASH64K_FUNCTION(i) (((i) * 2654435761U) >> ((MINMATCH*8) - \
        HASHLOG64K))
#define LZ4_HASH64K_VALUE(p)    LZ4_HASH64K_FUNCTION(A32(p))

/*ARGSUSED*/
static int
LZ4_compress64kCtx(void *ctx, const char *source, char *dest, int isize,
    int osize)
{
#if HEAPMODE
        struct refTables *srt = (struct refTables *)ctx;
        U16 *HashTable = (U16 *) (srt->hashTable);
#else
        U16 HashTable[HASH64KTABLESIZE] = { 0 };
#endif

        const BYTE *ip = (const BYTE *) source;
        const BYTE *anchor = ip;
        const BYTE *const base = ip;
        const BYTE *const iend = ip + isize;
        const BYTE *const oend = (BYTE *) dest + osize;
        const BYTE *const mflimit = iend - MFLIMIT;
#define matchlimit (iend - LASTLITERALS)

        BYTE *op = (BYTE *) dest;

        int len, length;
        const int skipStrength = SKIPSTRENGTH;
        U32 forwardH;

        /* Init */
        if (isize < MINLENGTH)
                goto _last_literals;

        /* First Byte */
        ip++;
        forwardH = LZ4_HASH64K_VALUE(ip);

        /* Main Loop */
        for (;;) {
                int findMatchAttempts = (1U << skipStrength) + 3;
                const BYTE *forwardIp = ip;
                const BYTE *ref;
                BYTE *token;

                /* Find a match */
                do {
                        U32 h = forwardH;
                        int step = findMatchAttempts++ >> skipStrength;
                        ip = forwardIp;
                        forwardIp = ip + step;

                        if (forwardIp > mflimit) {
                                goto _last_literals;
                        }

                        forwardH = LZ4_HASH64K_VALUE(forwardIp);
                        ref = base + HashTable[h];
                        HashTable[h] = ip - base;

                } while (A32(ref) != A32(ip));

                /* Catch up */
                while ((ip > anchor) && (ref > (const BYTE *) source) &&
                    (ip[-1] == ref[-1])) {
                        ip--;
                        ref--;
                }

                /* Encode Literal length */
                length = ip - anchor;
                token = op++;

                /* Check output limit */
                if unlikely(op + length + (2 + 1 + LASTLITERALS) +
                    (length >> 8) > oend)
                        return (0);

                if (length >= (int)RUN_MASK) {
                        *token = (RUN_MASK << ML_BITS);
                        len = length - RUN_MASK;
                        for (; len > 254; len -= 255)
                                *op++ = 255;
                        *op++ = (BYTE)len;
                } else
                        *token = (length << ML_BITS);

                /* Copy Literals */
                LZ4_BLINDCOPY(anchor, op, length);

                _next_match:
                /* Encode Offset */
                LZ4_WRITE_LITTLEENDIAN_16(op, ip - ref);

                /* Start Counting */
                ip += MINMATCH;
                ref += MINMATCH;        /* MinMatch verified */
                anchor = ip;
                while (ip < matchlimit - (STEPSIZE - 1)) {
                        UARCH diff = AARCH(ref) ^ AARCH(ip);
                        if (!diff) {
                                ip += STEPSIZE;
                                ref += STEPSIZE;
                                continue;
                        }
                        ip += LZ4_NbCommonBytes(diff);
                        goto _endCount;
                }
#if LZ4_ARCH64
                if ((ip < (matchlimit - 3)) && (A32(ref) == A32(ip))) {
                        ip += 4;
                        ref += 4;
                }
#endif
                if ((ip < (matchlimit - 1)) && (A16(ref) == A16(ip))) {
                        ip += 2;
                        ref += 2;
                }
                if ((ip < matchlimit) && (*ref == *ip))
                        ip++;
                _endCount:

                /* Encode MatchLength */
                len = (ip - anchor);
                /* Check output limit */
                if unlikely(op + (1 + LASTLITERALS) + (len >> 8) > oend)
                        return (0);
                if (len >= (int)ML_MASK) {
                        *token += ML_MASK;
                        len -= ML_MASK;
                        for (; len > 509; len -= 510) {
                                *op++ = 255;
                                *op++ = 255;
                        }
                        if (len > 254) {
                                len -= 255;
                                *op++ = 255;
                        }
                        *op++ = (BYTE)len;
                } else
                        *token += len;

                /* Test end of chunk */
                if (ip > mflimit) {
                        anchor = ip;
                        break;
                }
                /* Fill table */
                HashTable[LZ4_HASH64K_VALUE(ip - 2)] = ip - 2 - base;

                /* Test next position */
                ref = base + HashTable[LZ4_HASH64K_VALUE(ip)];
                HashTable[LZ4_HASH64K_VALUE(ip)] = ip - base;
                if (A32(ref) == A32(ip)) {
                        token = op++;
                        *token = 0;
                        goto _next_match;
                }
                /* Prepare next loop */
                anchor = ip++;
                forwardH = LZ4_HASH64K_VALUE(ip);
        }

        _last_literals:
        /* Encode Last Literals */
        {
                int lastRun = iend - anchor;
                if (op + lastRun + 1 + ((lastRun + 255 - RUN_MASK) / 255) >
                    oend)
                        return (0);
                if (lastRun >= (int)RUN_MASK) {
                        *op++ = (RUN_MASK << ML_BITS);
                        lastRun -= RUN_MASK;
                        for (; lastRun > 254; lastRun -= 255)
                                *op++ = 255;
                        *op++ = (BYTE)lastRun;
                } else
                        *op++ = (lastRun << ML_BITS);
                (void) memcpy(op, anchor, iend - anchor);
                op += iend - anchor;
        }

        /* End */
        return (int)(((char *)op) - dest);
}

static int
real_LZ4_compress(const char *source, char *dest, int isize, int osize)
{
#if HEAPMODE
#if defined(_KERNEL) || defined(_FAKE_KERNEL)
        void *ctx = kmem_zalloc(sizeof (struct refTables), KM_NOSLEEP);
#else
        void *ctx = calloc(1, sizeof (struct refTables));
#endif
        int result;

        /*
         * out of kernel memory, gently fall through - this will disable
         * compression in zio_compress_data
         */
        if (ctx == NULL)
                return (0);

        if (isize < LZ4_64KLIMIT)
                result = LZ4_compress64kCtx(ctx, source, dest, isize, osize);
        else
                result = LZ4_compressCtx(ctx, source, dest, isize, osize);

#if defined(_KERNEL) || defined(_FAKE_KERNEL)
        kmem_free(ctx, sizeof (struct refTables));
#else
        free(ctx);
#endif
        return (result);
#else
        if (isize < (int)LZ4_64KLIMIT)
                return (LZ4_compress64kCtx(NULL, source, dest, isize, osize));
        return (LZ4_compressCtx(NULL, source, dest, isize, osize));
#endif
}

/* Decompression functions */

/*
 * Note: The decoding function LZ4_uncompress_unknownOutputSize() is safe
 *      against "buffer overflow" attack type. It will never write nor
 *      read outside of the provided output buffers.
 *      LZ4_uncompress_unknownOutputSize() also insures that
 *      it will never read outside of the input buffer. A corrupted input
 *      will produce an error result, a negative int, indicating the position
 *      of the error within input stream.
 */

static int
LZ4_uncompress_unknownOutputSize(const char *source, char *dest, int isize,
    int maxOutputSize)
{
        /* Local Variables */
        const BYTE *restrict ip = (const BYTE *) source;
        const BYTE *const iend = ip + isize;
        const BYTE *ref;

        BYTE *op = (BYTE *) dest;
        BYTE *const oend = op + maxOutputSize;
        BYTE *cpy;

        size_t dec32table[] = {0, 3, 2, 3, 0, 0, 0, 0};
#if LZ4_ARCH64
        size_t dec64table[] = {0, 0, 0, (size_t)-1, 0, 1, 2, 3};
#endif

        /* Main Loop */
        while (ip < iend) {
                unsigned token;
                size_t length;

                /* get runlength */
                token = *ip++;
                if ((length = (token >> ML_BITS)) == RUN_MASK) {
                        int s = 255;
                        while ((ip < iend) && (s == 255)) {
                                s = *ip++;
                                length += s;
                        }
                }
                /* copy literals */
                cpy = op + length;
                /* CORNER-CASE: cpy might overflow. */
                if (cpy < op)
                        goto _output_error;     /* cpy was overflowed, bail! */
                if ((cpy > oend - COPYLENGTH) ||
                    (ip + length > iend - COPYLENGTH)) {
                        if (cpy > oend)
                                /* Error: writes beyond output buffer */
                                goto _output_error;
                        if (ip + length != iend)
                                /*
                                 * Error: LZ4 format requires to consume all
                                 * input at this stage
                                 */
                                goto _output_error;
                        (void) memcpy(op, ip, length);
                        op += length;
                        /* Necessarily EOF, due to parsing restrictions */
                        break;
                }
                LZ4_WILDCOPY(ip, op, cpy);
                ip -= (op - cpy);
                op = cpy;

                /* get offset */
                LZ4_READ_LITTLEENDIAN_16(ref, cpy, ip);
                ip += 2;
                if (ref < (BYTE * const) dest)
                        /*
                         * Error: offset creates reference outside of
                         * destination buffer
                         */
                        goto _output_error;

                /* get matchlength */
                if ((length = (token & ML_MASK)) == ML_MASK) {
                        while (ip < iend) {
                                int s = *ip++;
                                length += s;
                                if (s == 255)
                                        continue;
                                break;
                        }
                }
                /* copy repeated sequence */
                if unlikely(op - ref < STEPSIZE) {
#if LZ4_ARCH64
                        size_t dec64 = dec64table[op-ref];
#else
                        const int dec64 = 0;
#endif
                        op[0] = ref[0];
                        op[1] = ref[1];
                        op[2] = ref[2];
                        op[3] = ref[3];
                        op += 4;
                        ref += 4;
                        ref -= dec32table[op-ref];
                        A32(op) = A32(ref);
                        op += STEPSIZE - 4;
                        ref -= dec64;
                } else {
                        LZ4_COPYSTEP(ref, op);
                }
                cpy = op + length - (STEPSIZE - 4);
                if (cpy > oend - COPYLENGTH) {
                        if (cpy > oend)
                                /*
                                 * Error: request to write outside of
                                 * destination buffer
                                 */
                                goto _output_error;
                        LZ4_SECURECOPY(ref, op, (oend - COPYLENGTH));
                        while (op < cpy)
                                *op++ = *ref++;
                        op = cpy;
                        if (op == oend)
                                /*
                                 * Check EOF (should never happen, since
                                 * last 5 bytes are supposed to be literals)
                                 */
                                goto _output_error;
                        continue;
                }
                LZ4_SECURECOPY(ref, op, cpy);
                op = cpy;       /* correction */
        }

        /* end of decoding */
        return (int)(((char *)op) - dest);

        /* write overflow error detected */
        _output_error:
        return (int)(-(((const char *)ip) - source));
}