Chris@43: /* inffast.c -- fast decoding Chris@43: * Copyright (C) 1995-2008, 2010, 2013 Mark Adler Chris@43: * For conditions of distribution and use, see copyright notice in zlib.h Chris@43: */ Chris@43: Chris@43: #include "zutil.h" Chris@43: #include "inftrees.h" Chris@43: #include "inflate.h" Chris@43: #include "inffast.h" Chris@43: Chris@43: #ifndef ASMINF Chris@43: Chris@43: /* Allow machine dependent optimization for post-increment or pre-increment. Chris@43: Based on testing to date, Chris@43: Pre-increment preferred for: Chris@43: - PowerPC G3 (Adler) Chris@43: - MIPS R5000 (Randers-Pehrson) Chris@43: Post-increment preferred for: Chris@43: - none Chris@43: No measurable difference: Chris@43: - Pentium III (Anderson) Chris@43: - M68060 (Nikl) Chris@43: */ Chris@43: #ifdef POSTINC Chris@43: # define OFF 0 Chris@43: # define PUP(a) *(a)++ Chris@43: #else Chris@43: # define OFF 1 Chris@43: # define PUP(a) *++(a) Chris@43: #endif Chris@43: Chris@43: /* Chris@43: Decode literal, length, and distance codes and write out the resulting Chris@43: literal and match bytes until either not enough input or output is Chris@43: available, an end-of-block is encountered, or a data error is encountered. Chris@43: When large enough input and output buffers are supplied to inflate(), for Chris@43: example, a 16K input buffer and a 64K output buffer, more than 95% of the Chris@43: inflate execution time is spent in this routine. Chris@43: Chris@43: Entry assumptions: Chris@43: Chris@43: state->mode == LEN Chris@43: strm->avail_in >= 6 Chris@43: strm->avail_out >= 258 Chris@43: start >= strm->avail_out Chris@43: state->bits < 8 Chris@43: Chris@43: On return, state->mode is one of: Chris@43: Chris@43: LEN -- ran out of enough output space or enough available input Chris@43: TYPE -- reached end of block code, inflate() to interpret next block Chris@43: BAD -- error in block data Chris@43: Chris@43: Notes: Chris@43: Chris@43: - The maximum input bits used by a length/distance pair is 15 bits for the Chris@43: length code, 5 bits for the length extra, 15 bits for the distance code, Chris@43: and 13 bits for the distance extra. This totals 48 bits, or six bytes. Chris@43: Therefore if strm->avail_in >= 6, then there is enough input to avoid Chris@43: checking for available input while decoding. Chris@43: Chris@43: - The maximum bytes that a single length/distance pair can output is 258 Chris@43: bytes, which is the maximum length that can be coded. inflate_fast() Chris@43: requires strm->avail_out >= 258 for each loop to avoid checking for Chris@43: output space. Chris@43: */ Chris@43: void ZLIB_INTERNAL inflate_fast(strm, start) Chris@43: z_streamp strm; Chris@43: unsigned start; /* inflate()'s starting value for strm->avail_out */ Chris@43: { Chris@43: struct inflate_state FAR *state; Chris@43: z_const unsigned char FAR *in; /* local strm->next_in */ Chris@43: z_const unsigned char FAR *last; /* have enough input while in < last */ Chris@43: unsigned char FAR *out; /* local strm->next_out */ Chris@43: unsigned char FAR *beg; /* inflate()'s initial strm->next_out */ Chris@43: unsigned char FAR *end; /* while out < end, enough space available */ Chris@43: #ifdef INFLATE_STRICT Chris@43: unsigned dmax; /* maximum distance from zlib header */ Chris@43: #endif Chris@43: unsigned wsize; /* window size or zero if not using window */ Chris@43: unsigned whave; /* valid bytes in the window */ Chris@43: unsigned wnext; /* window write index */ Chris@43: unsigned char FAR *window; /* allocated sliding window, if wsize != 0 */ Chris@43: unsigned long hold; /* local strm->hold */ Chris@43: unsigned bits; /* local strm->bits */ Chris@43: code const FAR *lcode; /* local strm->lencode */ Chris@43: code const FAR *dcode; /* local strm->distcode */ Chris@43: unsigned lmask; /* mask for first level of length codes */ Chris@43: unsigned dmask; /* mask for first level of distance codes */ Chris@43: code here; /* retrieved table entry */ Chris@43: unsigned op; /* code bits, operation, extra bits, or */ Chris@43: /* window position, window bytes to copy */ Chris@43: unsigned len; /* match length, unused bytes */ Chris@43: unsigned dist; /* match distance */ Chris@43: unsigned char FAR *from; /* where to copy match from */ Chris@43: Chris@43: /* copy state to local variables */ Chris@43: state = (struct inflate_state FAR *)strm->state; Chris@43: in = strm->next_in - OFF; Chris@43: last = in + (strm->avail_in - 5); Chris@43: out = strm->next_out - OFF; Chris@43: beg = out - (start - strm->avail_out); Chris@43: end = out + (strm->avail_out - 257); Chris@43: #ifdef INFLATE_STRICT Chris@43: dmax = state->dmax; Chris@43: #endif Chris@43: wsize = state->wsize; Chris@43: whave = state->whave; Chris@43: wnext = state->wnext; Chris@43: window = state->window; Chris@43: hold = state->hold; Chris@43: bits = state->bits; Chris@43: lcode = state->lencode; Chris@43: dcode = state->distcode; Chris@43: lmask = (1U << state->lenbits) - 1; Chris@43: dmask = (1U << state->distbits) - 1; Chris@43: Chris@43: /* decode literals and length/distances until end-of-block or not enough Chris@43: input data or output space */ Chris@43: do { Chris@43: if (bits < 15) { Chris@43: hold += (unsigned long)(PUP(in)) << bits; Chris@43: bits += 8; Chris@43: hold += (unsigned long)(PUP(in)) << bits; Chris@43: bits += 8; Chris@43: } Chris@43: here = lcode[hold & lmask]; Chris@43: dolen: Chris@43: op = (unsigned)(here.bits); Chris@43: hold >>= op; Chris@43: bits -= op; Chris@43: op = (unsigned)(here.op); Chris@43: if (op == 0) { /* literal */ Chris@43: Tracevv((stderr, here.val >= 0x20 && here.val < 0x7f ? Chris@43: "inflate: literal '%c'\n" : Chris@43: "inflate: literal 0x%02x\n", here.val)); Chris@43: PUP(out) = (unsigned char)(here.val); Chris@43: } Chris@43: else if (op & 16) { /* length base */ Chris@43: len = (unsigned)(here.val); Chris@43: op &= 15; /* number of extra bits */ Chris@43: if (op) { Chris@43: if (bits < op) { Chris@43: hold += (unsigned long)(PUP(in)) << bits; Chris@43: bits += 8; Chris@43: } Chris@43: len += (unsigned)hold & ((1U << op) - 1); Chris@43: hold >>= op; Chris@43: bits -= op; Chris@43: } Chris@43: Tracevv((stderr, "inflate: length %u\n", len)); Chris@43: if (bits < 15) { Chris@43: hold += (unsigned long)(PUP(in)) << bits; Chris@43: bits += 8; Chris@43: hold += (unsigned long)(PUP(in)) << bits; Chris@43: bits += 8; Chris@43: } Chris@43: here = dcode[hold & dmask]; Chris@43: dodist: Chris@43: op = (unsigned)(here.bits); Chris@43: hold >>= op; Chris@43: bits -= op; Chris@43: op = (unsigned)(here.op); Chris@43: if (op & 16) { /* distance base */ Chris@43: dist = (unsigned)(here.val); Chris@43: op &= 15; /* number of extra bits */ Chris@43: if (bits < op) { Chris@43: hold += (unsigned long)(PUP(in)) << bits; Chris@43: bits += 8; Chris@43: if (bits < op) { Chris@43: hold += (unsigned long)(PUP(in)) << bits; Chris@43: bits += 8; Chris@43: } Chris@43: } Chris@43: dist += (unsigned)hold & ((1U << op) - 1); Chris@43: #ifdef INFLATE_STRICT Chris@43: if (dist > dmax) { Chris@43: strm->msg = (char *)"invalid distance too far back"; Chris@43: state->mode = BAD; Chris@43: break; Chris@43: } Chris@43: #endif Chris@43: hold >>= op; Chris@43: bits -= op; Chris@43: Tracevv((stderr, "inflate: distance %u\n", dist)); Chris@43: op = (unsigned)(out - beg); /* max distance in output */ Chris@43: if (dist > op) { /* see if copy from window */ Chris@43: op = dist - op; /* distance back in window */ Chris@43: if (op > whave) { Chris@43: if (state->sane) { Chris@43: strm->msg = Chris@43: (char *)"invalid distance too far back"; Chris@43: state->mode = BAD; Chris@43: break; Chris@43: } Chris@43: #ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR Chris@43: if (len <= op - whave) { Chris@43: do { Chris@43: PUP(out) = 0; Chris@43: } while (--len); Chris@43: continue; Chris@43: } Chris@43: len -= op - whave; Chris@43: do { Chris@43: PUP(out) = 0; Chris@43: } while (--op > whave); Chris@43: if (op == 0) { Chris@43: from = out - dist; Chris@43: do { Chris@43: PUP(out) = PUP(from); Chris@43: } while (--len); Chris@43: continue; Chris@43: } Chris@43: #endif Chris@43: } Chris@43: from = window - OFF; Chris@43: if (wnext == 0) { /* very common case */ Chris@43: from += wsize - op; Chris@43: if (op < len) { /* some from window */ Chris@43: len -= op; Chris@43: do { Chris@43: PUP(out) = PUP(from); Chris@43: } while (--op); Chris@43: from = out - dist; /* rest from output */ Chris@43: } Chris@43: } Chris@43: else if (wnext < op) { /* wrap around window */ Chris@43: from += wsize + wnext - op; Chris@43: op -= wnext; Chris@43: if (op < len) { /* some from end of window */ Chris@43: len -= op; Chris@43: do { Chris@43: PUP(out) = PUP(from); Chris@43: } while (--op); Chris@43: from = window - OFF; Chris@43: if (wnext < len) { /* some from start of window */ Chris@43: op = wnext; Chris@43: len -= op; Chris@43: do { Chris@43: PUP(out) = PUP(from); Chris@43: } while (--op); Chris@43: from = out - dist; /* rest from output */ Chris@43: } Chris@43: } Chris@43: } Chris@43: else { /* contiguous in window */ Chris@43: from += wnext - op; Chris@43: if (op < len) { /* some from window */ Chris@43: len -= op; Chris@43: do { Chris@43: PUP(out) = PUP(from); Chris@43: } while (--op); Chris@43: from = out - dist; /* rest from output */ Chris@43: } Chris@43: } Chris@43: while (len > 2) { Chris@43: PUP(out) = PUP(from); Chris@43: PUP(out) = PUP(from); Chris@43: PUP(out) = PUP(from); Chris@43: len -= 3; Chris@43: } Chris@43: if (len) { Chris@43: PUP(out) = PUP(from); Chris@43: if (len > 1) Chris@43: PUP(out) = PUP(from); Chris@43: } Chris@43: } Chris@43: else { Chris@43: from = out - dist; /* copy direct from output */ Chris@43: do { /* minimum length is three */ Chris@43: PUP(out) = PUP(from); Chris@43: PUP(out) = PUP(from); Chris@43: PUP(out) = PUP(from); Chris@43: len -= 3; Chris@43: } while (len > 2); Chris@43: if (len) { Chris@43: PUP(out) = PUP(from); Chris@43: if (len > 1) Chris@43: PUP(out) = PUP(from); Chris@43: } Chris@43: } Chris@43: } Chris@43: else if ((op & 64) == 0) { /* 2nd level distance code */ Chris@43: here = dcode[here.val + (hold & ((1U << op) - 1))]; Chris@43: goto dodist; Chris@43: } Chris@43: else { Chris@43: strm->msg = (char *)"invalid distance code"; Chris@43: state->mode = BAD; Chris@43: break; Chris@43: } Chris@43: } Chris@43: else if ((op & 64) == 0) { /* 2nd level length code */ Chris@43: here = lcode[here.val + (hold & ((1U << op) - 1))]; Chris@43: goto dolen; Chris@43: } Chris@43: else if (op & 32) { /* end-of-block */ Chris@43: Tracevv((stderr, "inflate: end of block\n")); Chris@43: state->mode = TYPE; Chris@43: break; Chris@43: } Chris@43: else { Chris@43: strm->msg = (char *)"invalid literal/length code"; Chris@43: state->mode = BAD; Chris@43: break; Chris@43: } Chris@43: } while (in < last && out < end); Chris@43: Chris@43: /* return unused bytes (on entry, bits < 8, so in won't go too far back) */ Chris@43: len = bits >> 3; Chris@43: in -= len; Chris@43: bits -= len << 3; Chris@43: hold &= (1U << bits) - 1; Chris@43: Chris@43: /* update state and return */ Chris@43: strm->next_in = in + OFF; Chris@43: strm->next_out = out + OFF; Chris@43: strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last)); Chris@43: strm->avail_out = (unsigned)(out < end ? Chris@43: 257 + (end - out) : 257 - (out - end)); Chris@43: state->hold = hold; Chris@43: state->bits = bits; Chris@43: return; Chris@43: } Chris@43: Chris@43: /* Chris@43: inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe): Chris@43: - Using bit fields for code structure Chris@43: - Different op definition to avoid & for extra bits (do & for table bits) Chris@43: - Three separate decoding do-loops for direct, window, and wnext == 0 Chris@43: - Special case for distance > 1 copies to do overlapped load and store copy Chris@43: - Explicit branch predictions (based on measured branch probabilities) Chris@43: - Deferring match copy and interspersed it with decoding subsequent codes Chris@43: - Swapping literal/length else Chris@43: - Swapping window/direct else Chris@43: - Larger unrolled copy loops (three is about right) Chris@43: - Moving len -= 3 statement into middle of loop Chris@43: */ Chris@43: Chris@43: #endif /* !ASMINF */