    /* inffast.c -- fast decoding
     * Copyright (C) 1995-2008, 2010, 2013 Mark Adler
     * For conditions of distribution and use, see copyright notice in zlib.h
     */

    #include "zutil.h"
    #include "inftrees.h"
    #include "inflate.h"
    #include "inffast.h"

    #ifndef ASMINF

    /* Allow machine dependent optimization for post-increment or pre-increment.
       Based on testing to date,
       Pre-increment preferred for:
       - PowerPC G3 (Adler)
       - MIPS R5000 (Randers-Pehrson)
       Post-increment preferred for:
       - none
       No measurable difference:
       - Pentium III (Anderson)
       - M68060 (Nikl)
     */
    #ifdef POSTINC
    #  define OFF 0
    #  define PUP(a) *(a)++
    #else
    #  define OFF 1
    #  define PUP(a) *++(a)
    #endif

    /*
       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(strm, start)
    z_streamp strm;
    unsigned start;         /* inflate()'s starting value for strm->avail_out */
    {
        struct inflate_state FAR *state;
        z_const unsigned char FAR *in;      /* local strm->next_in */
        z_const unsigned char FAR *last;    /* have enough input while in < last */
        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 wnext;             /* 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 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 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;
        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 += (unsigned long)(PUP(in)) << bits;
                bits += 8;
                hold += (unsigned long)(PUP(in)) << bits;
                bits += 8;
            }
            here = lcode[hold & lmask];
          dolen:
            op = (unsigned)(here.bits);
            hold >>= op;
            bits -= op;
            op = (unsigned)(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 = (unsigned)(here.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;
                }
                here = dcode[hold & dmask];
              dodist:
                op = (unsigned)(here.bits);
                hold >>= op;
                bits -= op;
                op = (unsigned)(here.op);
                if (op & 16) {                      /* distance base */
                    dist = (unsigned)(here.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) {
                            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 + (hold & ((1U << op) - 1))];
                    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 + (hold & ((1U << op) - 1))];
                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;
    }

    /*
       inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
       - Using bit fields for code structure
       - Different op definition to avoid & for extra bits (do & for table bits)
       - Three separate decoding do-loops for direct, window, and wnext == 0
       - Special case for distance > 1 copies to do overlapped load and store copy
       - Explicit branch predictions (based on measured branch probabilities)
       - Deferring match copy and interspersed it with decoding subsequent codes
       - Swapping literal/length else
       - Swapping window/direct else
       - Larger unrolled copy loops (three is about right)
       - Moving len -= 3 statement into middle of loop
     */

    #endif /* !ASMINF */