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zlib-src/inflate.c  view on Meta::CPAN

/*
   Update the window with the last wsize (normally 32K) bytes written before
   returning.  If window does not exist yet, create it.  This is only called
   when a window is already in use, or when output has been written during this
   inflate call, but the end of the deflate stream has not been reached yet.
   It is also called to create a window for dictionary data when a dictionary
   is loaded.

   Providing output buffers larger than 32K to inflate() should provide a speed
   advantage, since only the last 32K of output is copied to the sliding window
   upon return from inflate(), and since all distances after the first 32K of
   output will fall in the output data, making match copies simpler and faster.
   The advantage may be dependent on the size of the processor's data caches.
 */
local int updatewindow(z_streamp strm, const Bytef *end, unsigned copy) {
    struct inflate_state FAR *state;
    unsigned dist;

    state = (struct inflate_state FAR *)strm->state;

    /* if it hasn't been done already, allocate space for the window */
    if (state->window == Z_NULL) {
        state->window = (unsigned char FAR *)
                        ZALLOC(strm, 1U << state->wbits,
                               sizeof(unsigned char));
        if (state->window == Z_NULL) return 1;
    }

    /* if window not in use yet, initialize */
    if (state->wsize == 0) {
        state->wsize = 1U << state->wbits;
        state->wnext = 0;
        state->whave = 0;
    }

    /* copy state->wsize or less output bytes into the circular window */
    if (copy >= state->wsize) {
        zmemcpy(state->window, end - state->wsize, state->wsize);
        state->wnext = 0;
        state->whave = state->wsize;
    }
    else {
        dist = state->wsize - state->wnext;
        if (dist > copy) dist = copy;
        zmemcpy(state->window + state->wnext, end - copy, dist);
        copy -= dist;
        if (copy) {
            zmemcpy(state->window, end - copy, copy);
            state->wnext = copy;
            state->whave = state->wsize;
        }
        else {
            state->wnext += dist;
            if (state->wnext == state->wsize) state->wnext = 0;
            if (state->whave < state->wsize) state->whave += dist;
        }
    }
    return 0;
}

/* Macros for inflate(): */

/* check function to use adler32() for zlib or crc32() for gzip */
#ifdef GUNZIP
#  define UPDATE_CHECK(check, buf, len) \
    (state->flags ? crc32(check, buf, len) : adler32(check, buf, len))
#else
#  define UPDATE_CHECK(check, buf, len) adler32(check, buf, len)
#endif

/* check macros for header crc */
#ifdef GUNZIP
#  define CRC2(check, word) \
    do { \
        hbuf[0] = (unsigned char)(word); \
        hbuf[1] = (unsigned char)((word) >> 8); \
        check = crc32(check, hbuf, 2); \
    } while (0)

#  define CRC4(check, word) \
    do { \
        hbuf[0] = (unsigned char)(word); \
        hbuf[1] = (unsigned char)((word) >> 8); \
        hbuf[2] = (unsigned char)((word) >> 16); \
        hbuf[3] = (unsigned char)((word) >> 24); \
        check = crc32(check, hbuf, 4); \
    } while (0)
#endif

/* Load registers with state in inflate() for speed */
#define LOAD() \
    do { \
        put = strm->next_out; \
        left = strm->avail_out; \
        next = strm->next_in; \
        have = strm->avail_in; \
        hold = state->hold; \
        bits = state->bits; \
    } while (0)

/* Restore state from registers in inflate() */
#define RESTORE() \
    do { \
        strm->next_out = put; \
        strm->avail_out = left; \
        strm->next_in = next; \
        strm->avail_in = have; \
        state->hold = hold; \
        state->bits = bits; \
    } while (0)

/* Clear the input bit accumulator */
#define INITBITS() \
    do { \
        hold = 0; \
        bits = 0; \
    } while (0)

/* Get a byte of input into the bit accumulator, or return from inflate()
   if there is no input available. */
#define PULLBYTE() \