LXR uboot/lib/lz4.c

   1// SPDX-License-Identifier: BSD-2-Clause
   2/*
   3   LZ4 - Fast LZ compression algorithm
   4   Copyright (C) 2011-2015, Yann Collet.
   5
   6   You can contact the author at :
   7   - LZ4 source repository : https://github.com/Cyan4973/lz4
   8   - LZ4 public forum : https://groups.google.com/forum/#!forum/lz4c
   9*/
  10
  11
  12/**************************************
  13*  Reading and writing into memory
  14**************************************/
  15
  16/* customized version of memcpy, which may overwrite up to 7 bytes beyond dstEnd */
  17static void LZ4_wildCopy(void* dstPtr, const void* srcPtr, void* dstEnd)
  18{
  19    BYTE* d = (BYTE*)dstPtr;
  20    const BYTE* s = (const BYTE*)srcPtr;
  21    BYTE* e = (BYTE*)dstEnd;
  22    do { LZ4_copy8(d,s); d+=8; s+=8; } while (d<e);
  23}
  24
  25
  26/**************************************
  27*  Common Constants
  28**************************************/
  29#define MINMATCH 4
  30
  31#define COPYLENGTH 8
  32#define LASTLITERALS 5
  33#define MFLIMIT (COPYLENGTH+MINMATCH)
  34static const int LZ4_minLength = (MFLIMIT+1);
  35
  36#define KB *(1 <<10)
  37#define MB *(1 <<20)
  38#define GB *(1U<<30)
  39
  40#define MAXD_LOG 16
  41#define MAX_DISTANCE ((1 << MAXD_LOG) - 1)
  42
  43#define ML_BITS  4
  44#define ML_MASK  ((1U<<ML_BITS)-1)
  45#define RUN_BITS (8-ML_BITS)
  46#define RUN_MASK ((1U<<RUN_BITS)-1)
  47
  48
  49/**************************************
  50*  Local Structures and types
  51**************************************/
  52typedef enum { noDict = 0, withPrefix64k, usingExtDict } dict_directive;
  53typedef enum { endOnOutputSize = 0, endOnInputSize = 1 } endCondition_directive;
  54typedef enum { full = 0, partial = 1 } earlyEnd_directive;
  55
  56
  57
  58/*******************************
  59*  Decompression functions
  60*******************************/
  61/*
  62 * This generic decompression function cover all use cases.
  63 * It shall be instantiated several times, using different sets of directives
  64 * Note that it is essential this generic function is really inlined,
  65 * in order to remove useless branches during compilation optimization.
  66 */
  67FORCE_INLINE int LZ4_decompress_generic(
  68                 const char* const source,
  69                 char* const dest,
  70                 int inputSize,
  71                 int outputSize,         /* If endOnInput==endOnInputSize, this value is the max size of Output Buffer. */
  72
  73                 int endOnInput,         /* endOnOutputSize, endOnInputSize */
  74                 int partialDecoding,    /* full, partial */
  75                 int targetOutputSize,   /* only used if partialDecoding==partial */
  76                 int dict,               /* noDict, withPrefix64k, usingExtDict */
  77                 const BYTE* const lowPrefix,  /* == dest if dict == noDict */
  78                 const BYTE* const dictStart,  /* only if dict==usingExtDict */
  79                 const size_t dictSize         /* note : = 0 if noDict */
  80                 )
  81{
  82    /* Local Variables */
  83    const BYTE* ip = (const BYTE*) source;
  84    const BYTE* const iend = ip + inputSize;
  85
  86    BYTE* op = (BYTE*) dest;
  87    BYTE* const oend = op + outputSize;
  88    BYTE* cpy;
  89    BYTE* oexit = op + targetOutputSize;
  90    const BYTE* const lowLimit = lowPrefix - dictSize;
  91
  92    const BYTE* const dictEnd = (const BYTE*)dictStart + dictSize;
  93    const size_t dec32table[] = {4, 1, 2, 1, 4, 4, 4, 4};
  94    const size_t dec64table[] = {0, 0, 0, (size_t)-1, 0, 1, 2, 3};
  95
  96    const int safeDecode = (endOnInput==endOnInputSize);
  97    const int checkOffset = ((safeDecode) && (dictSize < (int)(64 KB)));
  98
  99
 100    /* Special cases */
 101    if ((partialDecoding) && (oexit> oend-MFLIMIT)) oexit = oend-MFLIMIT;                         /* targetOutputSize too high => decode everything */
 102    if ((endOnInput) && (unlikely(outputSize==0))) return ((inputSize==1) && (*ip==0)) ? 0 : -1;  /* Empty output buffer */
 103    if ((!endOnInput) && (unlikely(outputSize==0))) return (*ip==0?1:-1);
 104
 105
 106    /* Main Loop */
 107    while (1)
 108    {
 109        unsigned token;
 110        size_t length;
 111        const BYTE* match;
 112
 113        /* get literal length */
 114        token = *ip++;
 115        if ((length=(token>>ML_BITS)) == RUN_MASK)
 116        {
 117            unsigned s;
 118            do
 119            {
 120                s = *ip++;
 121                length += s;
 122            }
 123            while (likely((endOnInput)?ip<iend-RUN_MASK:1) && (s==255));
 124            if ((safeDecode) && unlikely((size_t)(op+length)<(size_t)(op))) goto _output_error;   /* overflow detection */
 125            if ((safeDecode) && unlikely((size_t)(ip+length)<(size_t)(ip))) goto _output_error;   /* overflow detection */
 126        }
 127
 128        /* copy literals */
 129        cpy = op+length;
 130        if (((endOnInput) && ((cpy>(partialDecoding?oexit:oend-MFLIMIT)) || (ip+length>iend-(2+1+LASTLITERALS))) )
 131            || ((!endOnInput) && (cpy>oend-COPYLENGTH)))
 132        {
 133            if (partialDecoding)
 134            {
 135                if (cpy > oend) goto _output_error;                           /* Error : write attempt beyond end of output buffer */
 136                if ((endOnInput) && (ip+length > iend)) goto _output_error;   /* Error : read attempt beyond end of input buffer */
 137            }
 138            else
 139            {
 140                if ((!endOnInput) && (cpy != oend)) goto _output_error;       /* Error : block decoding must stop exactly there */
 141                if ((endOnInput) && ((ip+length != iend) || (cpy > oend))) goto _output_error;   /* Error : input must be consumed */
 142            }
 143            memcpy(op, ip, length);
 144            ip += length;
 145            op += length;
 146            break;     /* Necessarily EOF, due to parsing restrictions */
 147        }
 148        LZ4_wildCopy(op, ip, cpy);
 149        ip += length; op = cpy;
 150
 151        /* get offset */
 152        match = cpy - LZ4_readLE16(ip); ip+=2;
 153        if ((checkOffset) && (unlikely(match < lowLimit))) goto _output_error;   /* Error : offset outside destination buffer */
 154
 155        /* get matchlength */
 156        length = token & ML_MASK;
 157        if (length == ML_MASK)
 158        {
 159            unsigned s;
 160            do
 161            {
 162                if ((endOnInput) && (ip > iend-LASTLITERALS)) goto _output_error;
 163                s = *ip++;
 164                length += s;
 165            } while (s==255);
 166            if ((safeDecode) && unlikely((size_t)(op+length)<(size_t)op)) goto _output_error;   /* overflow detection */
 167        }
 168        length += MINMATCH;
 169
 170        /* check external dictionary */
 171        if ((dict==usingExtDict) && (match < lowPrefix))
 172        {
 173            if (unlikely(op+length > oend-LASTLITERALS)) goto _output_error;   /* doesn't respect parsing restriction */
 174
 175            if (length <= (size_t)(lowPrefix-match))
 176            {
 177                /* match can be copied as a single segment from external dictionary */
 178                match = dictEnd - (lowPrefix-match);
 179                memmove(op, match, length); op += length;
 180            }
 181            else
 182            {
 183                /* match encompass external dictionary and current segment */
 184                size_t copySize = (size_t)(lowPrefix-match);
 185                memcpy(op, dictEnd - copySize, copySize);
 186                op += copySize;
 187                copySize = length - copySize;
 188                if (copySize > (size_t)(op-lowPrefix))   /* overlap within current segment */
 189                {
 190                    BYTE* const endOfMatch = op + copySize;
 191                    const BYTE* copyFrom = lowPrefix;
 192                    while (op < endOfMatch) *op++ = *copyFrom++;
 193                }
 194                else
 195                {
 196                    memcpy(op, lowPrefix, copySize);
 197                    op += copySize;
 198                }
 199            }
 200            continue;
 201        }
 202
 203        /* copy repeated sequence */
 204        cpy = op + length;
 205        if (unlikely((op-match)<8))
 206        {
 207            const size_t dec64 = dec64table[op-match];
 208            op[0] = match[0];
 209            op[1] = match[1];
 210            op[2] = match[2];
 211            op[3] = match[3];
 212            match += dec32table[op-match];
 213            LZ4_copy4(op+4, match);
 214            op += 8; match -= dec64;
 215        } else { LZ4_copy8(op, match); op+=8; match+=8; }
 216
 217        if (unlikely(cpy>oend-12))
 218        {
 219            if (cpy > oend-LASTLITERALS) goto _output_error;    /* Error : last LASTLITERALS bytes must be literals */
 220            if (op < oend-8)
 221            {
 222                LZ4_wildCopy(op, match, oend-8);
 223                match += (oend-8) - op;
 224                op = oend-8;
 225            }
 226            while (op<cpy) *op++ = *match++;
 227        }
 228        else
 229            LZ4_wildCopy(op, match, cpy);
 230        op=cpy;   /* correction */
 231    }
 232
 233    /* end of decoding */
 234    if (endOnInput)
 235       return (int) (((char*)op)-dest);     /* Nb of output bytes decoded */
 236    else
 237       return (int) (((const char*)ip)-source);   /* Nb of input bytes read */
 238
 239    /* Overflow error detected */
 240_output_error:
 241    return (int) (-(((const char*)ip)-source))-1;
 242}
 243