state->bits = bits;
return;
}
+void Z_INTERNAL zng_inflate_fast_back(PREFIX3(stream) *strm, unsigned long start) {
+ /* start: inflate()'s starting value for strm->avail_out */
+ struct inflate_state *state;
+ z_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 */
+ unsigned char *safe; /* can use chunkcopy provided out < safe */
+#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 */
+
+ /* hold is a local copy of strm->hold. By default, hold satisfies the same
+ invariants that strm->hold does, namely that (hold >> bits) == 0. This
+ invariant is kept by loading bits into hold one byte at a time, like:
+ hold |= next_byte_of_input << bits; in++; bits += 8;
+ If we need to ensure that bits >= 15 then this code snippet is simply
+ repeated. Over one iteration of the outermost do/while loop, this
+ happens up to six times (48 bits of input), as described in the NOTES
+ above.
+ However, on some little endian architectures, it can be significantly
+ faster to load 64 bits once instead of 8 bits six times:
+ if (bits <= 16) {
+ hold |= next_8_bytes_of_input << bits; in += 6; bits += 48;
+ }
+ Unlike the simpler one byte load, shifting the next_8_bytes_of_input
+ by bits will overflow and lose those high bits, up to 2 bytes' worth.
+ The conservative estimate is therefore that we have read only 6 bytes
+ (48 bits). Again, as per the NOTES above, 48 bits is sufficient for the
+ rest of the iteration, and we will not need to load another 8 bytes.
+ Inside this function, we no longer satisfy (hold >> bits) == 0, but
+ this is not problematic, even if that overflow does not land on an 8 bit
+ byte boundary. Those excess bits will eventually shift down lower as the
+ Huffman decoder consumes input, and when new input bits need to be loaded
+ into the bits variable, the same input bits will be or'ed over those
+ existing bits. A bitwise or is idempotent: (a | b | b) equals (a | b).
+ Note that we therefore write that load operation as "hold |= etc" and not
+ "hold += etc".
+ Outside that loop, at the end of the function, hold is bitwise and'ed
+ with (1<<bits)-1 to drop those excess bits so that, on function exit, we
+ keep the invariant that (state->hold >> state->bits) == 0.
+ */
+ uint64_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 */
+ const 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 */
+ unsigned extra_safe; /* copy chunks safely in all cases */
+
+ /* copy state to local variables */
+ state = (struct inflate_state *)strm->state;
+ in = strm->next_in;
+ last = in + (strm->avail_in - (INFLATE_FAST_MIN_HAVE - 1));
+ out = strm->next_out;
+ beg = out - (start - strm->avail_out);
+ end = out + (strm->avail_out - (INFLATE_FAST_MIN_LEFT - 1));
+ safe = out + strm->avail_out;
+#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;
+
+ /* Detect if out and window point to the same memory allocation. In this instance it is
+ necessary to use safe chunk copy functions to prevent overwriting the window. If the
+ window is overwritten then future matches with far distances will fail to copy correctly. */
+ extra_safe = (wsize != 0 && out >= window && out + INFLATE_FAST_MIN_LEFT <= window + wsize);
+
+ /* decode literals and length/distances until end-of-block or not enough
+ input data or output space */
+ do {
+ if (bits < 15) {
+ hold |= load_64_bits(in, bits);
+ in += 6;
+ bits += 48;
+ }
+ 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));
+ *out++ = (unsigned char)(here->val);
+ } else if (op & 16) { /* length base */
+ len = here->val;
+ op &= 15; /* number of extra bits */
+ if (bits < op) {
+ hold |= load_64_bits(in, bits);
+ in += 6;
+ bits += 48;
+ }
+ len += BITS(op);
+ DROPBITS(op);
+ Tracevv((stderr, "inflate: length %u\n", len));
+ if (bits < 15) {
+ hold |= load_64_bits(in, bits);
+ in += 6;
+ bits += 48;
+ }
+ 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 |= load_64_bits(in, bits);
+ in += 6;
+ bits += 48;
+ }
+ dist += BITS(op);
+#ifdef INFLATE_STRICT
+ if (dist > dmax) {
+ SET_BAD("invalid distance too far back");
+ 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) {
+ SET_BAD("invalid distance too far back");
+ 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;
+ } else if (wnext >= op) { /* contiguous in window */
+ from += wnext - op;
+ } else { /* wrap around window */
+ op -= wnext;
+ from += wsize - op;
+ if (op < len) { /* some from end of window */
+ len -= op;
+ out = functable.chunkcopy_safe(out, from, op, safe);
+ from = window; /* more from start of window */
+ op = wnext;
+ /* This (rare) case can create a situation where
+ the first chunkcopy below must be checked.
+ */
+ }
+ }
+ if (op < len) { /* still need some from output */
+ len -= op;
+ out = functable.chunkcopy_safe(out, from, op, safe);
+ out = functable.chunkunroll(out, &dist, &len);
+ out = functable.chunkcopy_safe(out, out - dist, len, safe);
+ } else {
+ out = functable.chunkcopy_safe(out, from, len, safe);
+ }
+ } else if (extra_safe) {
+ /* Whole reference is in range of current output. */
+ if (dist >= len || dist >= state->chunksize)
+ out = functable.chunkcopy_safe(out, out - dist, len, safe);
+ else
+ out = functable.chunkmemset_safe(out, dist, len, (unsigned)((safe - out) + 1));
+ } else {
+ /* Whole reference is in range of current output. No range checks are
+ necessary because we start with room for at least 258 bytes of output,
+ so unroll and roundoff operations can write beyond `out+len` so long
+ as they stay within 258 bytes of `out`.
+ */
+ if (dist >= len || dist >= state->chunksize)
+ out = functable.chunkcopy(out, out - dist, len);
+ else
+ out = functable.chunkmemset(out, dist, len);
+ }
+ } else if ((op & 64) == 0) { /* 2nd level distance code */
+ here = dcode + here->val + BITS(op);
+ goto dodist;
+ } else {
+ SET_BAD("invalid distance code");
+ 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 {
+ SET_BAD("invalid literal/length code");
+ 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 &= (UINT64_C(1) << bits) - 1;
+
+ /* update state and return */
+ strm->next_in = in;
+ strm->next_out = out;
+ strm->avail_in = (unsigned)(in < last ? (INFLATE_FAST_MIN_HAVE - 1) + (last - in)
+ : (INFLATE_FAST_MIN_HAVE - 1) - (in - last));
+ strm->avail_out = (unsigned)(out < end ? (INFLATE_FAST_MIN_LEFT - 1) + (end - out)
+ : (INFLATE_FAST_MIN_LEFT - 1) - (out - end));
+
+ Assert(bits <= 32, "Remaining bits greater than 32");
+ state->hold = (uint32_t)hold;
+ state->bits = bits;
+ return;
+}
/*
inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
projects / thirdparty / zlib-ng.git / commitdiff
