src/zlib/inffast.c

/* inffast.c -- fast decoding
 * Copyright (C) 1995-2004 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 inflate_fast(strm, start)
z_streamp strm;
unsigned start;         /* inflate()'s starting value for strm->avail_out */
{
    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;
            }
        }
        else if ((op & 64) == 0) {              /* 2nd level length code */
            this = lcode[this.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 write == 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 */
Commit	Line	Data
	1	/* inffast.c -- fast decoding
	2	* Copyright (C) 1995-2004 Mark Adler
	3	* For conditions of distribution and use, see copyright notice in zlib.h
	4	*/
	5
	6	#include "zutil.h"
	7	#include "inftrees.h"
	8	#include "inflate.h"
	9	#include "inffast.h"
	10
	11	#ifndef ASMINF
	12
	13	/* Allow machine dependent optimization for post-increment or pre-increment.
	14	Based on testing to date,
	15	Pre-increment preferred for:
	16	- PowerPC G3 (Adler)
	17	- MIPS R5000 (Randers-Pehrson)
	18	Post-increment preferred for:
	19	- none
	20	No measurable difference:
	21	- Pentium III (Anderson)
	22	- M68060 (Nikl)
	23	*/
	24	#ifdef POSTINC
	25	# define OFF 0
	26	# define PUP(a) *(a)++
	27	#else
	28	# define OFF 1
	29	# define PUP(a) *++(a)
	30	#endif
	31
	32	/*
	33	Decode literal, length, and distance codes and write out the resulting
	34	literal and match bytes until either not enough input or output is
	35	available, an end-of-block is encountered, or a data error is encountered.
	36	When large enough input and output buffers are supplied to inflate(), for
	37	example, a 16K input buffer and a 64K output buffer, more than 95% of the
	38	inflate execution time is spent in this routine.
	39
	40	Entry assumptions:
	41
	42	state->mode == LEN
	43	strm->avail_in >= 6
	44	strm->avail_out >= 258
	45	start >= strm->avail_out
	46	state->bits < 8
	47
	48	On return, state->mode is one of:
	49
	50	LEN -- ran out of enough output space or enough available input
	51	TYPE -- reached end of block code, inflate() to interpret next block
	52	BAD -- error in block data
	53
	54	Notes:
	55
	56	- The maximum input bits used by a length/distance pair is 15 bits for the
	57	length code, 5 bits for the length extra, 15 bits for the distance code,
	58	and 13 bits for the distance extra. This totals 48 bits, or six bytes.
	59	Therefore if strm->avail_in >= 6, then there is enough input to avoid
	60	checking for available input while decoding.
	61
	62	- The maximum bytes that a single length/distance pair can output is 258
	63	bytes, which is the maximum length that can be coded. inflate_fast()
	64	requires strm->avail_out >= 258 for each loop to avoid checking for
	65	output space.
	66	*/
	67	void inflate_fast(strm, start)
	68	z_streamp strm;
	69	unsigned start; /* inflate()'s starting value for strm->avail_out */
	70	{
	71	struct inflate_state FAR *state;
	72	unsigned char FAR in; / local strm->next_in */
	73	unsigned char FAR last; / while in < last, enough input available */
	74	unsigned char FAR out; / local strm->next_out */
	75	unsigned char FAR beg; / inflate()'s initial strm->next_out */
	76	unsigned char FAR end; / while out < end, enough space available */
	77	#ifdef INFLATE_STRICT
	78	unsigned dmax; /* maximum distance from zlib header */
	79	#endif
	80	unsigned wsize; /* window size or zero if not using window */
	81	unsigned whave; /* valid bytes in the window */
	82	unsigned write; /* window write index */
	83	unsigned char FAR window; / allocated sliding window, if wsize != 0 */
	84	unsigned long hold; /* local strm->hold */
	85	unsigned bits; /* local strm->bits */
	86	code const FAR lcode; / local strm->lencode */
	87	code const FAR dcode; / local strm->distcode */
	88	unsigned lmask; /* mask for first level of length codes */
	89	unsigned dmask; /* mask for first level of distance codes */
	90	code this; /* retrieved table entry */
	91	unsigned op; /* code bits, operation, extra bits, or */
	92	/* window position, window bytes to copy */
	93	unsigned len; /* match length, unused bytes */
	94	unsigned dist; /* match distance */
	95	unsigned char FAR from; / where to copy match from */
	96
	97	/* copy state to local variables */
	98	state = (struct inflate_state FAR *)strm->state;
	99	in = strm->next_in - OFF;
	100	last = in + (strm->avail_in - 5);
	101	out = strm->next_out - OFF;
	102	beg = out - (start - strm->avail_out);
	103	end = out + (strm->avail_out - 257);
	104	#ifdef INFLATE_STRICT
	105	dmax = state->dmax;
	106	#endif
	107	wsize = state->wsize;
	108	whave = state->whave;
	109	write = state->write;
	110	window = state->window;
	111	hold = state->hold;
	112	bits = state->bits;
	113	lcode = state->lencode;
	114	dcode = state->distcode;
	115	lmask = (1U << state->lenbits) - 1;
	116	dmask = (1U << state->distbits) - 1;
	117
	118	/* decode literals and length/distances until end-of-block or not enough
	119	input data or output space */
	120	do {
	121	if (bits < 15) {
	122	hold += (unsigned long)(PUP(in)) << bits;
	123	bits += 8;
	124	hold += (unsigned long)(PUP(in)) << bits;
	125	bits += 8;
	126	}
	127	this = lcode[hold & lmask];
	128	dolen:
	129	op = (unsigned)(this.bits);
	130	hold >>= op;
	131	bits -= op;
	132	op = (unsigned)(this.op);
	133	if (op == 0) { /* literal */
	134	Tracevv((stderr, this.val >= 0x20 && this.val < 0x7f ?
	135	"inflate: literal '%c'\n" :
	136	"inflate: literal 0x%02x\n", this.val));
	137	PUP(out) = (unsigned char)(this.val);
	138	}
	139	else if (op & 16) { /* length base */
	140	len = (unsigned)(this.val);
	141	op &= 15; /* number of extra bits */
	142	if (op) {
	143	if (bits < op) {
	144	hold += (unsigned long)(PUP(in)) << bits;
	145	bits += 8;
	146	}
	147	len += (unsigned)hold & ((1U << op) - 1);
	148	hold >>= op;
	149	bits -= op;
	150	}
	151	Tracevv((stderr, "inflate: length %u\n", len));
	152	if (bits < 15) {
	153	hold += (unsigned long)(PUP(in)) << bits;
	154	bits += 8;
	155	hold += (unsigned long)(PUP(in)) << bits;
	156	bits += 8;
	157	}
	158	this = dcode[hold & dmask];
	159	dodist:
	160	op = (unsigned)(this.bits);
	161	hold >>= op;
	162	bits -= op;
	163	op = (unsigned)(this.op);
	164	if (op & 16) { /* distance base */
	165	dist = (unsigned)(this.val);
	166	op &= 15; /* number of extra bits */
	167	if (bits < op) {
	168	hold += (unsigned long)(PUP(in)) << bits;
	169	bits += 8;
	170	if (bits < op) {
	171	hold += (unsigned long)(PUP(in)) << bits;
	172	bits += 8;
	173	}
	174	}
	175	dist += (unsigned)hold & ((1U << op) - 1);
	176	#ifdef INFLATE_STRICT
	177	if (dist > dmax) {
	178	strm->msg = (char *)"invalid distance too far back";
	179	state->mode = BAD;
	180	break;
	181	}
	182	#endif
	183	hold >>= op;
	184	bits -= op;
	185	Tracevv((stderr, "inflate: distance %u\n", dist));
	186	op = (unsigned)(out - beg); /* max distance in output */
	187	if (dist > op) { /* see if copy from window */
	188	op = dist - op; /* distance back in window */
	189	if (op > whave) {
	190	strm->msg = (char *)"invalid distance too far back";
	191	state->mode = BAD;
	192	break;
	193	}
	194	from = window - OFF;
	195	if (write == 0) { /* very common case */
	196	from += wsize - op;
	197	if (op < len) { /* some from window */
	198	len -= op;
	199	do {
	200	PUP(out) = PUP(from);
	201	} while (--op);
	202	from = out - dist; /* rest from output */
	203	}
	204	}
	205	else if (write < op) { /* wrap around window */
	206	from += wsize + write - op;
	207	op -= write;
	208	if (op < len) { /* some from end of window */
	209	len -= op;
	210	do {
	211	PUP(out) = PUP(from);
	212	} while (--op);
	213	from = window - OFF;
	214	if (write < len) { /* some from start of window */
	215	op = write;
	216	len -= op;
	217	do {
	218	PUP(out) = PUP(from);
	219	} while (--op);
	220	from = out - dist; /* rest from output */
	221	}
	222	}
	223	}
	224	else { /* contiguous in window */
	225	from += write - op;
	226	if (op < len) { /* some from window */
	227	len -= op;
	228	do {
	229	PUP(out) = PUP(from);
	230	} while (--op);
	231	from = out - dist; /* rest from output */
	232	}
	233	}
	234	while (len > 2) {
	235	PUP(out) = PUP(from);
	236	PUP(out) = PUP(from);
	237	PUP(out) = PUP(from);
	238	len -= 3;
	239	}
	240	if (len) {
	241	PUP(out) = PUP(from);
	242	if (len > 1)
	243	PUP(out) = PUP(from);
	244	}
	245	}
	246	else {
	247	from = out - dist; /* copy direct from output */
	248	do { /* minimum length is three */
	249	PUP(out) = PUP(from);
	250	PUP(out) = PUP(from);
	251	PUP(out) = PUP(from);
	252	len -= 3;
	253	} while (len > 2);
	254	if (len) {
	255	PUP(out) = PUP(from);
	256	if (len > 1)
	257	PUP(out) = PUP(from);
	258	}
	259	}
	260	}
	261	else if ((op & 64) == 0) { /* 2nd level distance code */
	262	this = dcode[this.val + (hold & ((1U << op) - 1))];
	263	goto dodist;
	264	}
	265	else {
	266	strm->msg = (char *)"invalid distance code";
	267	state->mode = BAD;
	268	break;
	269	}
	270	}
	271	else if ((op & 64) == 0) { /* 2nd level length code */
	272	this = lcode[this.val + (hold & ((1U << op) - 1))];
	273	goto dolen;
	274	}
	275	else if (op & 32) { /* end-of-block */
	276	Tracevv((stderr, "inflate: end of block\n"));
	277	state->mode = TYPE;
	278	break;
	279	}
	280	else {
	281	strm->msg = (char *)"invalid literal/length code";
	282	state->mode = BAD;
	283	break;
	284	}
	285	} while (in < last && out < end);
	286
	287	/* return unused bytes (on entry, bits < 8, so in won't go too far back) */
	288	len = bits >> 3;
	289	in -= len;
	290	bits -= len << 3;
	291	hold &= (1U << bits) - 1;
	292
	293	/* update state and return */
	294	strm->next_in = in + OFF;
	295	strm->next_out = out + OFF;
	296	strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
	297	strm->avail_out = (unsigned)(out < end ?
	298	257 + (end - out) : 257 - (out - end));
	299	state->hold = hold;
	300	state->bits = bits;
	301	return;
	302	}
	303
	304	/*
	305	inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
	306	- Using bit fields for code structure
	307	- Different op definition to avoid & for extra bits (do & for table bits)
	308	- Three separate decoding do-loops for direct, window, and write == 0
	309	- Special case for distance > 1 copies to do overlapped load and store copy
	310	- Explicit branch predictions (based on measured branch probabilities)
	311	- Deferring match copy and interspersed it with decoding subsequent codes
	312	- Swapping literal/length else
	313	- Swapping window/direct else
	314	- Larger unrolled copy loops (three is about right)
	315	- Moving len -= 3 statement into middle of loop
	316	*/
	317
	318	#endif /* !ASMINF */