X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=inffast.c;h=0dbd1dbc09f2f69425405863bfe1080e3ca2b3f5;hb=e00a2bd392ca51351ecee55dbeee803f6ebda2f5;hp=209c0ee6384ba0627c07aedc67cb21fd15b911bc;hpb=56bcb184fac036a45cb8937238d51778d0a796aa;p=zlib.git diff --git a/inffast.c b/inffast.c index 209c0ee..0dbd1db 100644 --- a/inffast.c +++ b/inffast.c @@ -1,168 +1,323 @@ -/* inffast.c -- process literals and length/distance pairs fast - * Copyright (C) 1995-1996 Mark Adler - * For conditions of distribution and use, see copyright notice in zlib.h +/* inffast.c -- fast decoding + * Copyright (C) 1995-2017 Mark Adler + * For conditions of distribution and use, see copyright notice in zlib.h */ #include "zutil.h" #include "inftrees.h" -#include "infblock.h" -#include "infcodes.h" -#include "infutil.h" +#include "inflate.h" #include "inffast.h" -struct inflate_codes_state {int dummy;}; /* for buggy compilers */ - -/* simplify the use of the inflate_huft type with some defines */ -#define base more.Base -#define next more.Next -#define exop word.what.Exop -#define bits word.what.Bits - -/* macros for bit input with no checking and for returning unused bytes */ -#define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<>3);p-=c;k&=7;} - -/* Called with number of bytes left to write in window at least 258 - (the maximum string length) and number of input bytes available - at least ten. The ten bytes are six bytes for the longest length/ - distance pair plus four bytes for overloading the bit buffer. */ - -int inflate_fast(bl, bd, tl, td, s, z) -uInt bl, bd; -inflate_huft *tl; -inflate_huft *td; /* need separate declaration for Borland C++ */ -inflate_blocks_statef *s; -z_stream *z; +#ifdef ASMINF +# pragma message("Assembler code may have bugs -- use at your own risk") +#else + +/* + 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 */ { - 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 */ - uInt ml; /* mask for literal/length tree */ - uInt md; /* mask for distance tree */ - uInt c; /* bytes to copy */ - uInt d; /* distance back to copy from */ - Bytef *r; /* copy source pointer */ - - /* load input, output, bit values */ - LOAD - - /* initialize masks */ - ml = inflate_mask[bl]; - md = inflate_mask[bd]; - - /* do until not enough input or output space for fast loop */ - do { /* assume called with m >= 258 && n >= 10 */ - /* get literal/length code */ - GRABBITS(20) /* max bits for literal/length code */ - if ((e = (t = tl + ((uInt)b & ml))->exop) == 0) - { - DUMPBITS(t->bits) - Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ? - "inflate: * literal '%c'\n" : - "inflate: * literal 0x%02x\n", t->base)); - *q++ = (Byte)t->base; - m--; - continue; - } + 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; + last = in + (strm->avail_in - 5); + out = strm->next_out; + 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 { - DUMPBITS(t->bits) - if (e & 16) - { - /* get extra bits for length */ - e &= 15; - c = t->base + ((uInt)b & inflate_mask[e]); - DUMPBITS(e) - Tracevv((stderr, "inflate: * length %u\n", c)); - - /* decode distance base of block to copy */ - GRABBITS(15); /* max bits for distance code */ - e = (t = td + ((uInt)b & md))->exop; - do { - DUMPBITS(t->bits) - if (e & 16) - { - /* get extra bits to add to distance base */ - e &= 15; - GRABBITS(e) /* get extra bits (up to 13) */ - d = t->base + ((uInt)b & inflate_mask[e]); - DUMPBITS(e) - Tracevv((stderr, "inflate: * distance %u\n", d)); - - /* do the copy */ - m -= c; - if ((uInt)(q - s->window) >= d) /* offset before dest */ - { /* just copy */ - r = q - d; - *q++ = *r++; c--; /* minimum count is three, */ - *q++ = *r++; c--; /* so unroll loop a little */ + if (bits < 15) { + hold += (unsigned long)(*in++) << bits; + bits += 8; + hold += (unsigned long)(*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)); + *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)(*in++) << bits; + bits += 8; + } + len += (unsigned)hold & ((1U << op) - 1); + hold >>= op; + bits -= op; } - else /* else offset after destination */ - { - e = d - (uInt)(q - s->window); /* bytes from offset to end */ - r = s->end - e; /* pointer to offset */ - if (c > e) /* if source crosses, */ - { - c -= e; /* copy to end of window */ - do { - *q++ = *r++; - } while (--e); - r = s->window; /* copy rest from start of window */ - } + Tracevv((stderr, "inflate: length %u\n", len)); + if (bits < 15) { + hold += (unsigned long)(*in++) << bits; + bits += 8; + hold += (unsigned long)(*in++) << bits; + bits += 8; } - do { /* copy all or what's left */ - *q++ = *r++; - } while (--c); + 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)(*in++) << bits; + bits += 8; + if (bits < op) { + hold += (unsigned long)(*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 { + *out++ = 0; + } while (--len); + continue; + } + len -= op - whave; + do { + *out++ = 0; + } while (--op > whave); + if (op == 0) { + from = out - dist; + do { + *out++ = *from++; + } while (--len); + continue; + } +#endif + } + from = window; + if (wnext == 0) { /* very common case */ + from += wsize - op; + if (op < len) { /* some from window */ + len -= op; + do { + *out++ = *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 { + *out++ = *from++; + } while (--op); + from = window; + if (wnext < len) { /* some from start of window */ + op = wnext; + len -= op; + do { + *out++ = *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 { + *out++ = *from++; + } while (--op); + from = out - dist; /* rest from output */ + } + } + while (len > 2) { + *out++ = *from++; + *out++ = *from++; + *out++ = *from++; + len -= 3; + } + if (len) { + *out++ = *from++; + if (len > 1) + *out++ = *from++; + } + } + else { + from = out - dist; /* copy direct from output */ + do { /* minimum length is three */ + *out++ = *from++; + *out++ = *from++; + *out++ = *from++; + len -= 3; + } while (len > 2); + if (len) { + *out++ = *from++; + if (len > 1) + *out++ = *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; - } - else if ((e & 64) == 0) - e = (t = t->next + ((uInt)b & inflate_mask[e]))->exop; - else - { - z->msg = (char*)"invalid distance code"; - UNGRAB - UPDATE - return Z_DATA_ERROR; - } - } while (1); - break; - } - if ((e & 64) == 0) - { - if ((e = (t = t->next + ((uInt)b & inflate_mask[e]))->exop) == 0) - { - DUMPBITS(t->bits) - Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ? - "inflate: * literal '%c'\n" : - "inflate: * literal 0x%02x\n", t->base)); - *q++ = (Byte)t->base; - m--; - break; } - } - else if (e & 32) - { - Tracevv((stderr, "inflate: * end of block\n")); - UNGRAB - UPDATE - return Z_STREAM_END; - } - else - { - z->msg = (char*)"invalid literal/length code"; - UNGRAB - UPDATE - return Z_DATA_ERROR; - } - } while (1); - } while (m >= 258 && n >= 10); - - /* not enough input or output--restore pointers and return */ - UNGRAB - UPDATE - return Z_OK; + } 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; + strm->next_out = out; + 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 */