fs/zfs/lz4.c

/*
 * 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/
 */

#include <sys/zfs_context.h>

static int real_LZ4_compress(const char *source, char *dest, int isize,
    int osize);
static int real_LZ4_uncompress(const char *source, char *dest, int osize);
static int LZ4_compressBound(int isize);
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);

/*ARGSUSED*/
size_t
lz4_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
{
    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.
     */
    *(uint32_t *)dest = BE_32(bufsiz);

    return (bufsiz + sizeof (bufsiz));
}

/*ARGSUSED*/
int
lz4_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
{
    const char *src = s_start;
    uint32_t bufsiz = BE_IN32(src);

    /* 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) worst case size
 *      evaluation is provided by function LZ4_compressBound().
 *
 * real_LZ4_uncompress() :
 *  osize  : is the output size, therefore the original size
 *  return : the number of bytes read in the source buffer.
 *      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 + osize, and is therefore protected
 *      against malicious data packets.
 *  note : destination buffer must be already allocated
 *
 * 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.
 *      This version is slightly slower than real_LZ4_uncompress()
 *
 * 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(__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

/*
 * 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

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

/* 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 *)(x))->v)
#define A32(x) (((U32_S *)(x))->v)
#define A16(x) (((U16_S *)(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

/* Public functions */

static int
LZ4_compressBound(int isize)
{
    return (isize + (isize / 255) + 16);
}

/* 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 = (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 > (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 = (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 > (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
    void *ctx = kmem_zalloc(sizeof (struct refTables), KM_NOSLEEP);
    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);

    kmem_free(ctx, sizeof (struct refTables));
    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 functions real_LZ4_uncompress() and
 *  LZ4_uncompress_unknownOutputSize() are safe against "buffer overflow"
 *  attack type. They 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
real_LZ4_uncompress(const char *source, char *dest, int osize)
{
    /* Local Variables */
    const BYTE *restrict ip = (const BYTE *) source;
    const BYTE *ref;

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

    unsigned token;

    size_t length;
    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 */
    for (;;) {
        /* get runlength */
        token = *ip++;
        if ((length = (token >> ML_BITS)) == RUN_MASK) {
            size_t len;
            for (; (len = *ip++) == 255; length += 255) {
            }
            length += len;
        }
        /* copy literals */
        cpy = op + length;
        /* CORNER-CASE: cpy might overflow. */
        if (cpy < op)
            goto _output_error; /* cpy was overflowed, bail! */
        if unlikely(cpy > oend - COPYLENGTH) {
            if (cpy != oend)
                /* Error: we must necessarily stand at EOF */
                goto _output_error;
            (void) memcpy(op, ip, length);
            ip += length;
            break;  /* EOF */
            }
        LZ4_WILDCOPY(ip, op, cpy);
        ip -= (op - cpy);
        op = cpy;

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

        /* get matchlength */
        if ((length = (token & ML_MASK)) == ML_MASK) {
            for (; *ip == 255; length += 255) {
                ip++;
            }
            length += *ip++;
        }
        /* 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 beyond 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 *)ip) - source);

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

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)(-(((char *)ip) - source));
}