1 | /* |
2 | * Copyright (c) 2015, Intel Corporation |
3 | * |
4 | * Redistribution and use in source and binary forms, with or without |
5 | * modification, are permitted provided that the following conditions are met: |
6 | * |
7 | * * Redistributions of source code must retain the above copyright notice, |
8 | * this list of conditions and the following disclaimer. |
9 | * * Redistributions in binary form must reproduce the above copyright |
10 | * notice, this list of conditions and the following disclaimer in the |
11 | * documentation and/or other materials provided with the distribution. |
12 | * * Neither the name of Intel Corporation nor the names of its contributors |
13 | * may be used to endorse or promote products derived from this software |
14 | * without specific prior written permission. |
15 | * |
16 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
17 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
18 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
19 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
20 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
21 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
22 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
23 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
24 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
25 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
26 | * POSSIBILITY OF SUCH DAMAGE. |
27 | */ |
28 | |
29 | #ifndef ROSE_MIRACLE_H |
30 | #define ROSE_MIRACLE_H |
31 | |
32 | #include "ue2common.h" |
33 | #include "runtime.h" |
34 | #include "rose_internal.h" |
35 | |
36 | /** \brief Maximum number of bytes to scan when looking for a "miracle" stop |
37 | * character. */ |
38 | #define MIRACLE_LEN_MAX 32 |
39 | |
40 | static really_inline |
41 | u64a roseMiracleScan(const u8 *stop, const u8 *d, const u8 *d_start) { |
42 | assert(d >= d_start); |
43 | |
44 | // Note: unrolling this loop manually does appear to reduce its |
45 | // performance. I'm sick of tilting at this particular windmill. |
46 | |
47 | u32 mshift = 0; |
48 | do { |
49 | u64a s = (u64a)stop[*d]; |
50 | if (s) { |
51 | s <<= mshift; |
52 | return s; |
53 | } |
54 | mshift++; |
55 | } while (--d >= d_start); |
56 | return 0; |
57 | } |
58 | |
59 | /** |
60 | * \brief "Miracle" scan: uses stop table to check if we can skip forward to a |
61 | * location where we know that the given rose engine will be in a known state. |
62 | * |
63 | * Scans the buffer/history between relative locations \a begin_loc and \a |
64 | * end_loc, and returns a miracle location (if any) that appears in the stream |
65 | * after \a begin_loc. |
66 | * |
67 | * Returns 1 if some bytes can be skipped and sets \a miracle_loc |
68 | * appropriately, 0 otherwise. |
69 | */ |
70 | static rose_inline |
71 | char roseMiracleOccurs(const struct RoseEngine *t, |
72 | const struct LeftNfaInfo *left, |
73 | const struct core_info *ci, const s64a begin_loc, |
74 | const s64a end_loc, s64a *miracle_loc) { |
75 | assert(!left->transient); |
76 | assert(left->stopTable); |
77 | |
78 | DEBUG_PRINTF("looking for miracle over [%lld,%lld], maxLag=%u\n" , |
79 | begin_loc, end_loc, left->maxLag); |
80 | DEBUG_PRINTF("ci->len=%zu, ci->hlen=%zu\n" , ci->len, ci->hlen); |
81 | |
82 | assert(begin_loc <= end_loc); |
83 | assert(begin_loc >= -(s64a)ci->hlen); |
84 | assert(end_loc <= (s64a)ci->len); |
85 | |
86 | const u8 *stop = getByOffset(t, left->stopTable); |
87 | |
88 | const s64a scan_end_loc = end_loc - left->maxLag; |
89 | if (scan_end_loc <= begin_loc) { |
90 | DEBUG_PRINTF("nothing to scan\n" ); |
91 | return 0; |
92 | } |
93 | |
94 | const s64a start = MAX(begin_loc, scan_end_loc - MIRACLE_LEN_MAX); |
95 | DEBUG_PRINTF("scan [%lld..%lld]\n" , start, scan_end_loc); |
96 | |
97 | u64a s = 0; // state, on bits are miracle locations |
98 | |
99 | // Scan buffer. |
100 | const s64a buf_scan_start = MAX(0, start); |
101 | if (scan_end_loc > buf_scan_start) { |
102 | const u8 *buf = ci->buf; |
103 | const u8 *d = buf + scan_end_loc - 1; |
104 | const u8 *d_start = buf + buf_scan_start; |
105 | s = roseMiracleScan(stop, d, d_start); |
106 | if (s) { |
107 | goto miracle_found; |
108 | } |
109 | } |
110 | |
111 | // Scan history. |
112 | if (start < 0) { |
113 | const u8 *hbuf_end = ci->hbuf + ci->hlen; |
114 | const u8 *d = hbuf_end + MIN(0, scan_end_loc) - 1; |
115 | const u8 *d_start = hbuf_end + start; |
116 | s = roseMiracleScan(stop, d, d_start); |
117 | if (scan_end_loc > 0) { |
118 | // Shift s over to account for the buffer scan above. |
119 | s <<= scan_end_loc; |
120 | } |
121 | } |
122 | |
123 | if (s) { |
124 | miracle_found: |
125 | DEBUG_PRINTF("s=0x%llx, ctz=%u\n" , s, ctz64(s)); |
126 | s64a loc = end_loc - left->maxLag - ctz64(s) - 1; |
127 | if (loc > begin_loc) { |
128 | DEBUG_PRINTF("miracle at %lld\n" , loc); |
129 | *miracle_loc = loc; |
130 | return 1; |
131 | } |
132 | } |
133 | |
134 | DEBUG_PRINTF("no viable miraculous stop characters found\n" ); |
135 | return 0; |
136 | } |
137 | |
138 | #endif // ROSE_MIRACLE_H |
139 | |