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ext/zstd/lib/common/zstd_internal.h  view on Meta::CPAN

#define WILDCOPY_OVERLENGTH 32
#define WILDCOPY_VECLEN 16

typedef enum {
    ZSTD_no_overlap,
    ZSTD_overlap_src_before_dst
    /*  ZSTD_overlap_dst_before_src, */
} ZSTD_overlap_e;

/*! ZSTD_wildcopy() :
 *  Custom version of ZSTD_memcpy(), can over read/write up to WILDCOPY_OVERLENGTH bytes (if length==0)
 *  @param ovtype controls the overlap detection
 *         - ZSTD_no_overlap: The source and destination are guaranteed to be at least WILDCOPY_VECLEN bytes apart.
 *         - ZSTD_overlap_src_before_dst: The src and dst may overlap, but they MUST be at least 8 bytes apart.
 *           The src buffer must be before the dst buffer.
 */
MEM_STATIC FORCE_INLINE_ATTR
void ZSTD_wildcopy(void* dst, const void* src, ptrdiff_t length, ZSTD_overlap_e const ovtype)
{
    ptrdiff_t diff = (BYTE*)dst - (const BYTE*)src;
    const BYTE* ip = (const BYTE*)src;
    BYTE* op = (BYTE*)dst;
    BYTE* const oend = op + length;

    if (ovtype == ZSTD_overlap_src_before_dst && diff < WILDCOPY_VECLEN) {
        /* Handle short offset copies. */
        do {
            COPY8(op, ip)
        } while (op < oend);
    } else {
        assert(diff >= WILDCOPY_VECLEN || diff <= -WILDCOPY_VECLEN);
        /* Separate out the first COPY16() call because the copy length is
         * almost certain to be short, so the branches have different
         * probabilities. Since it is almost certain to be short, only do
         * one COPY16() in the first call. Then, do two calls per loop since
         * at that point it is more likely to have a high trip count.
         */
        ZSTD_copy16(op, ip);
        if (16 >= length) return;
        op += 16;
        ip += 16;
        do {
            COPY16(op, ip);
            COPY16(op, ip);
        }
        while (op < oend);
    }
}

MEM_STATIC size_t ZSTD_limitCopy(void* dst, size_t dstCapacity, const void* src, size_t srcSize)
{
    size_t const length = MIN(dstCapacity, srcSize);
    if (length > 0) {
        ZSTD_memcpy(dst, src, length);
    }
    return length;
}

/* define "workspace is too large" as this number of times larger than needed */
#define ZSTD_WORKSPACETOOLARGE_FACTOR 3

/* when workspace is continuously too large
 * during at least this number of times,
 * context's memory usage is considered wasteful,
 * because it's sized to handle a worst case scenario which rarely happens.
 * In which case, resize it down to free some memory */
#define ZSTD_WORKSPACETOOLARGE_MAXDURATION 128

/* Controls whether the input/output buffer is buffered or stable. */
typedef enum {
    ZSTD_bm_buffered = 0,  /* Buffer the input/output */
    ZSTD_bm_stable = 1     /* ZSTD_inBuffer/ZSTD_outBuffer is stable */
} ZSTD_bufferMode_e;


/*-*******************************************
*  Private declarations
*********************************************/
typedef struct seqDef_s {
    U32 offBase;   /* offBase == Offset + ZSTD_REP_NUM, or repcode 1,2,3 */
    U16 litLength;
    U16 mlBase;    /* mlBase == matchLength - MINMATCH */
} seqDef;

/* Controls whether seqStore has a single "long" litLength or matchLength. See seqStore_t. */
typedef enum {
    ZSTD_llt_none = 0,             /* no longLengthType */
    ZSTD_llt_literalLength = 1,    /* represents a long literal */
    ZSTD_llt_matchLength = 2       /* represents a long match */
} ZSTD_longLengthType_e;

typedef struct {
    seqDef* sequencesStart;
    seqDef* sequences;      /* ptr to end of sequences */
    BYTE*  litStart;
    BYTE*  lit;             /* ptr to end of literals */
    BYTE*  llCode;
    BYTE*  mlCode;
    BYTE*  ofCode;
    size_t maxNbSeq;
    size_t maxNbLit;

    /* longLengthPos and longLengthType to allow us to represent either a single litLength or matchLength
     * in the seqStore that has a value larger than U16 (if it exists). To do so, we increment
     * the existing value of the litLength or matchLength by 0x10000.
     */
    ZSTD_longLengthType_e longLengthType;
    U32                   longLengthPos;  /* Index of the sequence to apply long length modification to */
} seqStore_t;

typedef struct {
    U32 litLength;
    U32 matchLength;
} ZSTD_sequenceLength;

/**
 * Returns the ZSTD_sequenceLength for the given sequences. It handles the decoding of long sequences
 * indicated by longLengthPos and longLengthType, and adds MINMATCH back to matchLength.
 */
MEM_STATIC ZSTD_sequenceLength ZSTD_getSequenceLength(seqStore_t const* seqStore, seqDef const* seq)
{
    ZSTD_sequenceLength seqLen;
    seqLen.litLength = seq->litLength;
    seqLen.matchLength = seq->mlBase + MINMATCH;
    if (seqStore->longLengthPos == (U32)(seq - seqStore->sequencesStart)) {
        if (seqStore->longLengthType == ZSTD_llt_literalLength) {
            seqLen.litLength += 0x10000;