示例#1
0
void BitOutput::send_bits(unsigned int value, int length) /* Send a value on a given number of bits. */
{
#ifdef DEBUG
   Tracevv((stderr," l %2d v %4x ", length, value));
   Assert(length > 0 && length <= 15, "invalid length");
   Assert(boffset < 8, "bad offset");
   bits_sent += (ulg)length;
#endif
   bitbuff |= value << boffset;
   if ((boffset += length) >= 8) {
	  outQueue->Put(bitbuff);
	  value >>= length - (boffset -= 8);
	  if (boffset >= 8) {
		 boffset -= 8;
		 outQueue->Put(value);
		 value >>= 8;
	  }
示例#2
0
文件: trees.cpp 项目: Rhobota/librho
local void send_bits(
    deflate_state *s,
    sInt value,  /* value to send */
    sInt length) /* number of bits */
{
    Tracevv((stderr," l %2d v %4x ", length, value));
    Assert(length > 0 && length <= 15, "invalid length");
    s->bits_sent += (ulg)length;

    /* If not enough room in bi_buf, use (valid) bits from bi_buf and
     * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
     * unused bits in value.
     */
    if (s->bi_valid > (sInt)Buf_size - length) {
        s->bi_buf |= (ush)value << s->bi_valid;
        put_short(s, s->bi_buf);
        s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
        s->bi_valid += length - Buf_size;
    } else {
示例#3
0
/*
   Decode literal, length, and distance codes and write out the resulting
   literal and match bytes until either not enough input or output is
   available, an end-of-block is encountered, or a data error is encountered.
   When large enough input and output buffers are supplied to inflate(), for
   example, a 16K input buffer and a 64K output buffer, more than 95% of the
   inflate execution time is spent in this routine.

   Entry assumptions:

        state->mode == LEN
        strm->avail_in >= 6
        strm->avail_out >= 258
        start >= strm->avail_out
        state->bits < 8

   On return, state->mode is one of:

        LEN -- ran out of enough output space or enough available input
        TYPE -- reached end of block code, inflate() to interpret next block
        BAD -- error in block data

   Notes:

    - The maximum input bits used by a length/distance pair is 15 bits for the
      length code, 5 bits for the length extra, 15 bits for the distance code,
      and 13 bits for the distance extra.  This totals 48 bits, or six bytes.
      Therefore if strm->avail_in >= 6, then there is enough input to avoid
      checking for available input while decoding.

    - The maximum bytes that a single length/distance pair can output is 258
      bytes, which is the maximum length that can be coded.  inflate_fast()
      requires strm->avail_out >= 258 for each loop to avoid checking for
      output space.
 */
void inflate_fast(z_streamp strm, unsigned start)
{
    struct inflate_state FAR *state;
    unsigned char FAR *in;      /* local strm->next_in */
    unsigned char FAR *last;    /* while in < last, enough input available */
    unsigned char FAR *out;     /* local strm->next_out */
    unsigned char FAR *beg;     /* inflate()'s initial strm->next_out */
    unsigned char FAR *end;     /* while out < end, enough space available */
#ifdef INFLATE_STRICT
    unsigned dmax;              /* maximum distance from zlib header */
#endif
    unsigned wsize;             /* window size or zero if not using window */
    unsigned whave;             /* valid bytes in the window */
    unsigned write;             /* window write index */
    unsigned char FAR *window;  /* allocated sliding window, if wsize != 0 */
    unsigned long hold;         /* local strm->hold */
    unsigned bits;              /* local strm->bits */
    code const FAR *lcode;      /* local strm->lencode */
    code const FAR *dcode;      /* local strm->distcode */
    unsigned lmask;             /* mask for first level of length codes */
    unsigned dmask;             /* mask for first level of distance codes */
    code this;                  /* retrieved table entry */
    unsigned op;                /* code bits, operation, extra bits, or */
                                /*  window position, window bytes to copy */
    unsigned len;               /* match length, unused bytes */
    unsigned dist;              /* match distance */
    unsigned char FAR *from;    /* where to copy match from */

    /* copy state to local variables */
    state = (struct inflate_state FAR *)strm->state;
    in = strm->next_in - OFF;
    last = in + (strm->avail_in - 5);
    out = strm->next_out - OFF;
    beg = out - (start - strm->avail_out);
    end = out + (strm->avail_out - 257);
#ifdef INFLATE_STRICT
    dmax = state->dmax;
#endif
    wsize = state->wsize;
    whave = state->whave;
    write = state->write;
    window = state->window;
    hold = state->hold;
    bits = state->bits;
    lcode = state->lencode;
    dcode = state->distcode;
    lmask = (1U << state->lenbits) - 1;
    dmask = (1U << state->distbits) - 1;

    /* decode literals and length/distances until end-of-block or not enough
       input data or output space */
    do {
        if (bits < 15) {
            hold += (unsigned long)(PUP(in)) << bits;
            bits += 8;
            hold += (unsigned long)(PUP(in)) << bits;
            bits += 8;
        }
        this = lcode[hold & lmask];
      dolen:
        op = (unsigned)(this.bits);
        hold >>= op;
        bits -= op;
        op = (unsigned)(this.op);
        if (op == 0) {                          /* literal */
            Tracevv((stderr, this.val >= 0x20 && this.val < 0x7f ?
                    "inflate:         literal '%c'\n" :
                    "inflate:         literal 0x%02x\n", this.val));
            PUP(out) = (unsigned char)(this.val);
        }
        else if (op & 16) {                     /* length base */
            len = (unsigned)(this.val);
            op &= 15;                           /* number of extra bits */
            if (op) {
                if (bits < op) {
                    hold += (unsigned long)(PUP(in)) << bits;
                    bits += 8;
                }
                len += (unsigned)hold & ((1U << op) - 1);
                hold >>= op;
                bits -= op;
            }
            Tracevv((stderr, "inflate:         length %u\n", len));
            if (bits < 15) {
                hold += (unsigned long)(PUP(in)) << bits;
                bits += 8;
                hold += (unsigned long)(PUP(in)) << bits;
                bits += 8;
            }
            this = dcode[hold & dmask];
          dodist:
            op = (unsigned)(this.bits);
            hold >>= op;
            bits -= op;
            op = (unsigned)(this.op);
            if (op & 16) {                      /* distance base */
                dist = (unsigned)(this.val);
                op &= 15;                       /* number of extra bits */
                if (bits < op) {
                    hold += (unsigned long)(PUP(in)) << bits;
                    bits += 8;
                    if (bits < op) {
                        hold += (unsigned long)(PUP(in)) << bits;
                        bits += 8;
                    }
                }
                dist += (unsigned)hold & ((1U << op) - 1);
#ifdef INFLATE_STRICT
                if (dist > dmax) {
                    strm->msg = (char *)"invalid distance too far back";
                    state->mode = BAD;
                    break;
                }
#endif
                hold >>= op;
                bits -= op;
                Tracevv((stderr, "inflate:         distance %u\n", dist));
                op = (unsigned)(out - beg);     /* max distance in output */
                if (dist > op) {                /* see if copy from window */
                    op = dist - op;             /* distance back in window */
                    if (op > whave) {
                        strm->msg = (char *)"invalid distance too far back";
                        state->mode = BAD;
                        break;
                    }
                    from = window - OFF;
                    if (write == 0) {           /* very common case */
                        from += wsize - op;
                        if (op < len) {         /* some from window */
                            len -= op;
                            do {
                                PUP(out) = PUP(from);
                            } while (--op);
                            from = out - dist;  /* rest from output */
                        }
                    }
                    else if (write < op) {      /* wrap around window */
                        from += wsize + write - op;
                        op -= write;
                        if (op < len) {         /* some from end of window */
                            len -= op;
                            do {
                                PUP(out) = PUP(from);
                            } while (--op);
                            from = window - OFF;
                            if (write < len) {  /* some from start of window */
                                op = write;
                                len -= op;
                                do {
                                    PUP(out) = PUP(from);
                                } while (--op);
                                from = out - dist;      /* rest from output */
                            }
                        }
                    }
                    else {                      /* contiguous in window */
                        from += write - op;
                        if (op < len) {         /* some from window */
                            len -= op;
                            do {
                                PUP(out) = PUP(from);
                            } while (--op);
                            from = out - dist;  /* rest from output */
                        }
                    }
                    while (len > 2) {
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        len -= 3;
                    }
                    if (len) {
                        PUP(out) = PUP(from);
                        if (len > 1)
                            PUP(out) = PUP(from);
                    }
                }
                else {
                    from = out - dist;          /* copy direct from output */
                    do {                        /* minimum length is three */
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        len -= 3;
                    } while (len > 2);
                    if (len) {
                        PUP(out) = PUP(from);
                        if (len > 1)
                            PUP(out) = PUP(from);
                    }
                }
            }
            else if ((op & 64) == 0) {          /* 2nd level distance code */
                this = dcode[this.val + (hold & ((1U << op) - 1))];
                goto dodist;
            }
            else {
                strm->msg = (char *)"invalid distance code";
                state->mode = BAD;
                break;
            }
        }
示例#4
0
int inflate_codes(inflate_blocks_statef *s, z_streamp z, int r)
{
    uInt j;			/* temporary storage */
    inflate_huft *t;		/* temporary pointer */
    uInt e;			/* extra bits or operation */
    uLong b;			/* bit buffer */
    uInt k;			/* bits in bit buffer */
    Bytef *p;			/* input data pointer */
    uInt n;			/* bytes available there */
    Bytef *q;			/* output window write pointer */
    uInt m;			/* bytes to end of window or read pointer */
    Bytef *f;			/* pointer to copy strings from */
    inflate_codes_statef *c = s->sub.decode.codes;	/* codes state */

    /* copy input/output information to locals (UPDATE macro restores) */
    LOAD

    /* process input and output based on current state */
	while (1)
	switch (c->mode)
	{			/* waiting for "i:"=input, "o:"=output, "x:"=nothing */
	    case START:	/* x: set up for LEN */
#ifndef SLOW
		if (m >= 258 && n >= 10)
		{
		    UPDATE
			r = inflate_fast(c->lbits, c->dbits, c->ltree, c->dtree, s, z);
		    LOAD
			if (r != Z_OK)
		    {
			c->mode = r == Z_STREAM_END ? WASH : BADCODE;
			break;
		    }
		}
#endif /* !SLOW */
		c->sub.code.need = c->lbits;
		c->sub.code.tree = c->ltree;
		c->mode = LEN;
	    case LEN:		/* i: get length/literal/eob next */
		j = c->sub.code.need;
		NEEDBITS(j)
		    t = c->sub.code.tree + ((uInt) b & inflate_mask[j]);
		DUMPBITS(t->bits)
		    e = (uInt) (t->exop);
		if (e == 0)	/* literal */
		{
		    c->sub.lit = t->base;
		    Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
			     "inflate:         literal '%c'\n" :
			     "inflate:         literal 0x%02x\n", t->base));
		    c->mode = LIT;
		    break;
		}
		if (e & 16)	/* length */
		{
		    c->sub.copy.get = e & 15;
		    c->len = t->base;
		    c->mode = LENEXT;
		    break;
		}
		if ((e & 64) == 0)	/* next table */
		{
		    c->sub.code.need = e;
		    c->sub.code.tree = t + t->base;
		    break;
		}
		if (e & 32)	/* end of block */
		{
		    Tracevv((stderr, "inflate:         end of block\n"));
		    c->mode = WASH;
		    break;
		}
		c->mode = BADCODE;	/* invalid code */
		z->msg = (char *)"invalid literal/length code";
		r = Z_DATA_ERROR;
		LEAVE
	    case LENEXT:	/* i: getting length extra (have base) */
		j = c->sub.copy.get;
		NEEDBITS(j)
		    c->len += (uInt) b & inflate_mask[j];
		DUMPBITS(j)
		    c->sub.code.need = c->dbits;
		c->sub.code.tree = c->dtree;
		Tracevv((stderr, "inflate:         length %u\n", c->len));
		c->mode = DIST;
	    case DIST:		/* i: get distance next */
		j = c->sub.code.need;
		NEEDBITS(j)
		    t = c->sub.code.tree + ((uInt) b & inflate_mask[j]);
		DUMPBITS(t->bits)
		    e = (uInt) (t->exop);
		if (e & 16)	/* distance */
		{
		    c->sub.copy.get = e & 15;
		    c->sub.copy.dist = t->base;
		    c->mode = DISTEXT;
		    break;
		}
		if ((e & 64) == 0)	/* next table */
		{
		    c->sub.code.need = e;
		    c->sub.code.tree = t + t->base;
		    break;
		}
		c->mode = BADCODE;	/* invalid code */
		z->msg = (char *)"invalid distance code";
		r = Z_DATA_ERROR;
		LEAVE
	    case DISTEXT:	/* i: getting distance extra */
		j = c->sub.copy.get;
		NEEDBITS(j)
		    c->sub.copy.dist += (uInt) b & inflate_mask[j];
		DUMPBITS(j)
		    Tracevv((stderr, "inflate:         distance %u\n", c->sub.copy.dist));
		c->mode = COPY;
	    case COPY:		/* o: copying bytes in window, waiting for space */
#ifndef __TURBOC__		/* Turbo C bug for following expression */
		f = (uInt) (q - s->window) < c->sub.copy.dist ?
		    s->end - (c->sub.copy.dist - (q - s->window)) :
		    q - c->sub.copy.dist;
#else
		f = q - c->sub.copy.dist;
		if ((uInt) (q - s->window) < c->sub.copy.dist)
		    f = s->end - (c->sub.copy.dist - (uInt) (q - s->window));
#endif
		while (c->len)
		{
		    NEEDOUT
			OUTBYTE(*f++)
			if (f == s->end)
			f = s->window;
		    c->len--;
		}
		c->mode = START;
		break;
	    case LIT:		/* o: got literal, waiting for output space */
		NEEDOUT
		    OUTBYTE(c->sub.lit)
		    c->mode = START;
		break;
	    case WASH:		/* o: got eob, possibly more output */
		if (k > 7)	/* return unused byte, if any */
		{
		    Assert(k < 16, "inflate_codes grabbed too many bytes")
			k -= 8;
		    n++;
		    p--;	/* can always return one */
		}
		FLUSH
		    if (s->read != s->write)
		    LEAVE
			c->mode = END;
	    case END:
		r = Z_STREAM_END;
		LEAVE
	    case BADCODE:	/* x: got error */
		r = Z_DATA_ERROR;
		LEAVE
	    default:
		r = Z_STREAM_ERROR;
		LEAVE
	}
示例#5
0
/*
   Decode literal, length, and distance codes and write out the resulting
   literal and match bytes until either not enough input or output is
   available, an end-of-block is encountered, or a data error is encountered.
   When large enough input and output buffers are supplied to inflate(), for
   example, a 16K input buffer and a 64K output buffer, more than 95% of the
   inflate execution time is spent in this routine.

   Entry assumptions:

        state->mode == LEN
        strm->avail_in >= 6
        strm->avail_out >= 258
        start >= strm->avail_out
        state->bits < 8

   On return, state->mode is one of:

        LEN -- ran out of enough output space or enough available input
        TYPE -- reached end of block code, inflate() to interpret next block
        BAD -- error in block data

   Notes:

    - The maximum input bits used by a length/distance pair is 15 bits for the
      length code, 5 bits for the length extra, 15 bits for the distance code,
      and 13 bits for the distance extra.  This totals 48 bits, or six bytes.
      Therefore if strm->avail_in >= 6, then there is enough input to avoid
      checking for available input while decoding.

    - The maximum bytes that a single length/distance pair can output is 258
      bytes, which is the maximum length that can be coded.  inflate_fast()
      requires strm->avail_out >= 258 for each loop to avoid checking for
      output space.
 */
void ZLIB_INTERNAL inflate_fast(z_stream *strm, unsigned long start) {
    /* start: inflate()'s starting value for strm->avail_out */
    struct inflate_state *state;
    const unsigned char *in;    /* local strm->next_in */
    const unsigned char *last;  /* have enough input while in < last */
    unsigned char *out;         /* local strm->next_out */
    unsigned char *beg;         /* inflate()'s initial strm->next_out */
    unsigned char *end;         /* while out < end, enough space available */
#ifdef INFLATE_STRICT
    unsigned dmax;              /* maximum distance from zlib header */
#endif
    unsigned wsize;             /* window size or zero if not using window */
    unsigned whave;             /* valid bytes in the window */
    unsigned wnext;             /* window write index */
    unsigned char *window;      /* allocated sliding window, if wsize != 0 */
    uint32_t hold;              /* local strm->hold */
    unsigned bits;              /* local strm->bits */
    code const *lcode;          /* local strm->lencode */
    code const *dcode;          /* local strm->distcode */
    unsigned lmask;             /* mask for first level of length codes */
    unsigned dmask;             /* mask for first level of distance codes */
    code here;                  /* retrieved table entry */
    unsigned op;                /* code bits, operation, extra bits, or */
                                /*  window position, window bytes to copy */
    unsigned len;               /* match length, unused bytes */
    unsigned dist;              /* match distance */
    unsigned char *from;        /* where to copy match from */

    /* copy state to local variables */
    state = (struct inflate_state *)strm->state;
    in = strm->next_in - OFF;
    last = in + (strm->avail_in - 5);
    out = strm->next_out - OFF;
    beg = out - (start - strm->avail_out);
    end = out + (strm->avail_out - 257);
#ifdef INFLATE_STRICT
    dmax = state->dmax;
#endif
    wsize = state->wsize;
    whave = state->whave;
    wnext = state->wnext;
    window = state->window;
    hold = state->hold;
    bits = state->bits;
    lcode = state->lencode;
    dcode = state->distcode;
    lmask = (1U << state->lenbits) - 1;
    dmask = (1U << state->distbits) - 1;

    /* decode literals and length/distances until end-of-block or not enough
       input data or output space */
    do {
        if (bits < 15) {
            hold += (PUP(in) << bits);
            bits += 8;
            hold += (PUP(in) << bits);
            bits += 8;
        }
        here = lcode[hold & lmask];
      dolen:
        DROPBITS(here.bits);
        op = here.op;
        if (op == 0) {                          /* literal */
            Tracevv((stderr, here.val >= 0x20 && here.val < 0x7f ?
                    "inflate:         literal '%c'\n" :
                    "inflate:         literal 0x%02x\n", here.val));
            PUP(out) = (unsigned char)(here.val);
        } else if (op & 16) {                     /* length base */
            len = here.val;
            op &= 15;                           /* number of extra bits */
            if (op) {
                if (bits < op) {
                    hold += (PUP(in) << bits);
                    bits += 8;
                }
                len += BITS(op);
                DROPBITS(op);
            }
            Tracevv((stderr, "inflate:         length %u\n", len));
            if (bits < 15) {
                hold += (PUP(in) << bits);
                bits += 8;
                hold += (PUP(in) << bits);
                bits += 8;
            }
            here = dcode[hold & dmask];
          dodist:
            DROPBITS(here.bits);
            op = here.op;
            if (op & 16) {                      /* distance base */
                dist = here.val;
                op &= 15;                       /* number of extra bits */
                if (bits < op) {
                    hold += (PUP(in) << bits);
                    bits += 8;
                    if (bits < op) {
                        hold += (PUP(in) << bits);
                        bits += 8;
                    }
                }
                dist += BITS(op);
#ifdef INFLATE_STRICT
                if (dist > dmax) {
                    strm->msg = (char *)"invalid distance too far back";
                    state->mode = BAD;
                    break;
                }
#endif
                DROPBITS(op);
                Tracevv((stderr, "inflate:         distance %u\n", dist));
                op = (unsigned)(out - beg);     /* max distance in output */
                if (dist > op) {                /* see if copy from window */
                    op = dist - op;             /* distance back in window */
                    if (op > whave) {
                        if (state->sane) {
                            strm->msg = (char *)"invalid distance too far back";
                            state->mode = BAD;
                            break;
                        }
#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
                        if (len <= op - whave) {
                            do {
                                PUP(out) = 0;
                            } while (--len);
                            continue;
                        }
                        len -= op - whave;
                        do {
                            PUP(out) = 0;
                        } while (--op > whave);
                        if (op == 0) {
                            from = out - dist;
                            do {
                                PUP(out) = PUP(from);
                            } while (--len);
                            continue;
                        }
#endif
                    }
                    from = window - OFF;
                    if (wnext == 0) {           /* very common case */
                        from += wsize - op;
                        if (op < len) {         /* some from window */
                            len -= op;
                            do {
                                PUP(out) = PUP(from);
                            } while (--op);
                            from = out - dist;  /* rest from output */
                        }
                    } else if (wnext < op) {      /* wrap around window */
                        from += wsize + wnext - op;
                        op -= wnext;
                        if (op < len) {         /* some from end of window */
                            len -= op;
                            do {
                                PUP(out) = PUP(from);
                            } while (--op);
                            from = window - OFF;
                            if (wnext < len) {  /* some from start of window */
                                op = wnext;
                                len -= op;
                                do {
                                    PUP(out) = PUP(from);
                                } while (--op);
                                from = out - dist;      /* rest from output */
                            }
                        }
                    } else {                      /* contiguous in window */
                        from += wnext - op;
                        if (op < len) {         /* some from window */
                            len -= op;
                            do {
                                PUP(out) = PUP(from);
                            } while (--op);
                            from = out - dist;  /* rest from output */
                        }
                    }
                    while (len > 2) {
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        len -= 3;
                    }
                    if (len) {
                        PUP(out) = PUP(from);
                        if (len > 1)
                            PUP(out) = PUP(from);
                    }
                } else {
                    from = out - dist;          /* copy direct from output */
                    do {                        /* minimum length is three */
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        len -= 3;
                    } while (len > 2);
                    if (len) {
                        PUP(out) = PUP(from);
                        if (len > 1)
                            PUP(out) = PUP(from);
                    }
                }
            } else if ((op & 64) == 0) {          /* 2nd level distance code */
                here = dcode[here.val + BITS(op)];
                goto dodist;
            } else {
                strm->msg = (char *)"invalid distance code";
                state->mode = BAD;
                break;
            }
        } else if ((op & 64) == 0) {              /* 2nd level length code */
            here = lcode[here.val + BITS(op)];
            goto dolen;
        } else if (op & 32) {                     /* end-of-block */
            Tracevv((stderr, "inflate:         end of block\n"));
            state->mode = TYPE;
            break;
        } else {
            strm->msg = (char *)"invalid literal/length code";
            state->mode = BAD;
            break;
        }
    } while (in < last && out < end);

    /* return unused bytes (on entry, bits < 8, so in won't go too far back) */
    len = bits >> 3;
    in -= len;
    bits -= len << 3;
    hold &= (1U << bits) - 1;

    /* update state and return */
    strm->next_in = in + OFF;
    strm->next_out = out + OFF;
    strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
    strm->avail_out = (unsigned)(out < end ? 257 + (end - out) : 257 - (out - end));
    state->hold = hold;
    state->bits = bits;
    return;
}
示例#6
0
/* ===========================================================================
 * Same as deflate_medium, but achieves better compression. We use a lazy
 * evaluation for matches: a match is finally adopted only if there is
 * no better match at the next window position.
 */
block_state deflate_slow(deflate_state *s, int flush) {
    IPos hash_head;          /* head of hash chain */
    int bflush;              /* set if current block must be flushed */

    /* Process the input block. */
    for (;;) {
        /* Make sure that we always have enough lookahead, except
         * at the end of the input file. We need MAX_MATCH bytes
         * for the next match, plus MIN_MATCH bytes to insert the
         * string following the next match.
         */
        if (s->lookahead < MIN_LOOKAHEAD) {
            fill_window(s);
            if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
                return need_more;
            }
            if (s->lookahead == 0)
                break; /* flush the current block */
        }

        /* Insert the string window[strstart .. strstart+2] in the
         * dictionary, and set hash_head to the head of the hash chain:
         */
        hash_head = NIL;
        if (s->lookahead >= MIN_MATCH) {
            hash_head = insert_string(s, s->strstart);
        }

        /* Find the longest match, discarding those <= prev_length.
         */
        s->prev_length = s->match_length, s->prev_match = s->match_start;
        s->match_length = MIN_MATCH-1;

        if (hash_head != NIL && s->prev_length < s->max_lazy_match && s->strstart - hash_head <= MAX_DIST(s)) {
            /* To simplify the code, we prevent matches with the string
             * of window index 0 (in particular we have to avoid a match
             * of the string with itself at the start of the input file).
             */
            s->match_length = longest_match(s, hash_head);
            /* longest_match() sets match_start */

            if (s->match_length <= 5 && (s->strategy == Z_FILTERED
#if TOO_FAR <= 32767
                || (s->match_length == MIN_MATCH && s->strstart - s->match_start > TOO_FAR)
#endif
                )) {

                /* If prev_match is also MIN_MATCH, match_start is garbage
                 * but we will ignore the current match anyway.
                 */
                s->match_length = MIN_MATCH-1;
            }
        }
        /* If there was a match at the previous step and the current
         * match is not better, output the previous match:
         */
        if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
            uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
            /* Do not insert strings in hash table beyond this. */

            check_match(s, s->strstart-1, s->prev_match, s->prev_length);

            _tr_tally_dist(s, s->strstart -1 - s->prev_match, s->prev_length - MIN_MATCH, bflush);

            /* Insert in hash table all strings up to the end of the match.
             * strstart-1 and strstart are already inserted. If there is not
             * enough lookahead, the last two strings are not inserted in
             * the hash table.
             */
            s->lookahead -= s->prev_length-1;

#ifdef NOT_TWEAK_COMPILER
            s->prev_length -= 2;
            do {
                if (++s->strstart <= max_insert) {
                    insert_string(s, s->strstart);
                }
            } while (--s->prev_length != 0);
            s->match_available = 0;
            s->match_length = MIN_MATCH-1;
            s->strstart++;
#else
            {
                uInt mov_fwd = s->prev_length - 2;
                uInt insert_cnt = mov_fwd;
                if (unlikely(insert_cnt > max_insert - s->strstart))
                    insert_cnt = max_insert - s->strstart;

                bulk_insert_str(s, s->strstart + 1, insert_cnt);
                s->prev_length = 0;
                s->match_available = 0;
                s->match_length = MIN_MATCH-1;
                s->strstart += mov_fwd + 1;
            }
#endif /*NOT_TWEAK_COMPILER*/

            if (bflush) FLUSH_BLOCK(s, 0);

        } else if (s->match_available) {
            /* If there was no match at the previous position, output a
             * single literal. If there was a match but the current match
             * is longer, truncate the previous match to a single literal.
             */
            Tracevv((stderr, "%c", s->window[s->strstart-1]));
            _tr_tally_lit(s, s->window[s->strstart-1], bflush);
            if (bflush) {
                FLUSH_BLOCK_ONLY(s, 0);
            }
            s->strstart++;
            s->lookahead--;
            if (s->strm->avail_out == 0)
                return need_more;
        } else {
            /* There is no previous match to compare with, wait for
             * the next step to decide.
             */
            s->match_available = 1;
            s->strstart++;
            s->lookahead--;
        }
    }
    Assert(flush != Z_NO_FLUSH, "no flush?");
    if (s->match_available) {
        Tracevv((stderr, "%c", s->window[s->strstart-1]));
        _tr_tally_lit(s, s->window[s->strstart-1], bflush);
        s->match_available = 0;
    }
    s->insert = s->strstart < MIN_MATCH-1 ? s->strstart : MIN_MATCH-1;
    if (flush == Z_FINISH) {
        FLUSH_BLOCK(s, 1);
        return finish_done;
    }
    if (s->last_lit)
        FLUSH_BLOCK(s, 0);
    return block_done;
}