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-rw-r--r--lib/zlib_inflate/inffast.c342
1 files changed, 342 insertions, 0 deletions
diff --git a/lib/zlib_inflate/inffast.c b/lib/zlib_inflate/inffast.c
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+++ b/lib/zlib_inflate/inffast.c
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+/* inffast.c -- fast decoding
+ * Copyright (C) 1995-2004 Mark Adler
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ */
+
+#include <linux/zutil.h>
+#include "inftrees.h"
+#include "inflate.h"
+#include "inffast.h"
+
+#ifndef ASMINF
+
+union uu {
+ unsigned short us;
+ unsigned char b[2];
+};
+
+/* Endian independed version */
+static inline unsigned short
+get_unaligned16(const unsigned short *p)
+{
+ union uu mm;
+ unsigned char *b = (unsigned char *)p;
+
+ mm.b[0] = b[0];
+ mm.b[1] = b[1];
+ return mm.us;
+}
+
+/*
+ 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.
+
+ - @start: inflate()'s starting value for strm->avail_out
+ */
+void inflate_fast(z_streamp strm, unsigned start)
+{
+ struct inflate_state *state;
+ const unsigned char *in; /* local strm->next_in */
+ const unsigned char *last; /* while in < last, enough input available */
+ 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 */
+#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 *window; /* allocated sliding window, if wsize != 0 */
+ unsigned long 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 */
+ 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 *from; /* where to copy match from */
+
+ /* copy state to local variables */
+ state = (struct inflate_state *)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;
+ 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)(*in++) << bits;
+ bits += 8;
+ hold += (unsigned long)(*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 */
+ *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)(*in++) << bits;
+ bits += 8;
+ }
+ len += (unsigned)hold & ((1U << op) - 1);
+ hold >>= op;
+ bits -= op;
+ }
+ if (bits < 15) {
+ hold += (unsigned long)(*in++) << bits;
+ bits += 8;
+ hold += (unsigned long)(*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)(*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;
+ 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;
+ if (write == 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 (write < op) { /* wrap around window */
+ from += wsize + write - op;
+ op -= write;
+ if (op < len) { /* some from end of window */
+ len -= op;
+ do {
+ *out++ = *from++;
+ } while (--op);
+ from = window;
+ if (write < len) { /* some from start of window */
+ op = write;
+ len -= op;
+ do {
+ *out++ = *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 {
+ *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 {
+ unsigned short *sout;
+ unsigned long loops;
+
+ from = out - dist; /* copy direct from output */
+ /* minimum length is three */
+ /* Align out addr */
+ if (!((long)(out - 1) & 1)) {
+ *out++ = *from++;
+ len--;
+ }
+ sout = (unsigned short *)(out);
+ if (dist > 2) {
+ unsigned short *sfrom;
+
+ sfrom = (unsigned short *)(from);
+ loops = len >> 1;
+ do
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+ *sout++ = *sfrom++;
+#else
+ *sout++ = get_unaligned16(sfrom++);
+#endif
+ while (--loops);
+ out = (unsigned char *)sout;
+ from = (unsigned char *)sfrom;
+ } else { /* dist == 1 or dist == 2 */
+ unsigned short pat16;
+
+ pat16 = *(sout-1);
+ if (dist == 1) {
+ union uu mm;
+ /* copy one char pattern to both bytes */
+ mm.us = pat16;
+ mm.b[0] = mm.b[1];
+ pat16 = mm.us;
+ }
+ loops = len >> 1;
+ do
+ *sout++ = pat16;
+ while (--loops);
+ out = (unsigned char *)sout;
+ }
+ if (len & 1)
+ *out++ = *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 */
+ 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;
+ 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 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 */
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