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-rw-r--r--src/util/asmap.cpp103
1 files changed, 103 insertions, 0 deletions
diff --git a/src/util/asmap.cpp b/src/util/asmap.cpp
new file mode 100644
index 0000000000..60bd27bf90
--- /dev/null
+++ b/src/util/asmap.cpp
@@ -0,0 +1,103 @@
+// Copyright (c) 2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <vector>
+#include <assert.h>
+#include <crypto/common.h>
+
+namespace {
+
+uint32_t DecodeBits(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos, uint8_t minval, const std::vector<uint8_t> &bit_sizes)
+{
+ uint32_t val = minval;
+ bool bit;
+ for (std::vector<uint8_t>::const_iterator bit_sizes_it = bit_sizes.begin();
+ bit_sizes_it != bit_sizes.end(); ++bit_sizes_it) {
+ if (bit_sizes_it + 1 != bit_sizes.end()) {
+ if (bitpos == endpos) break;
+ bit = *bitpos;
+ bitpos++;
+ } else {
+ bit = 0;
+ }
+ if (bit) {
+ val += (1 << *bit_sizes_it);
+ } else {
+ for (int b = 0; b < *bit_sizes_it; b++) {
+ if (bitpos == endpos) break;
+ bit = *bitpos;
+ bitpos++;
+ val += bit << (*bit_sizes_it - 1 - b);
+ }
+ return val;
+ }
+ }
+ return -1;
+}
+
+const std::vector<uint8_t> TYPE_BIT_SIZES{0, 0, 1};
+uint32_t DecodeType(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
+{
+ return DecodeBits(bitpos, endpos, 0, TYPE_BIT_SIZES);
+}
+
+const std::vector<uint8_t> ASN_BIT_SIZES{15, 16, 17, 18, 19, 20, 21, 22, 23, 24};
+uint32_t DecodeASN(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
+{
+ return DecodeBits(bitpos, endpos, 1, ASN_BIT_SIZES);
+}
+
+
+const std::vector<uint8_t> MATCH_BIT_SIZES{1, 2, 3, 4, 5, 6, 7, 8};
+uint32_t DecodeMatch(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
+{
+ return DecodeBits(bitpos, endpos, 2, MATCH_BIT_SIZES);
+}
+
+
+const std::vector<uint8_t> JUMP_BIT_SIZES{5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30};
+uint32_t DecodeJump(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
+{
+ return DecodeBits(bitpos, endpos, 17, JUMP_BIT_SIZES);
+}
+
+}
+
+uint32_t Interpret(const std::vector<bool> &asmap, const std::vector<bool> &ip)
+{
+ std::vector<bool>::const_iterator pos = asmap.begin();
+ const std::vector<bool>::const_iterator endpos = asmap.end();
+ uint8_t bits = ip.size();
+ uint32_t default_asn = 0;
+ uint32_t opcode, jump, match, matchlen;
+ while (pos != endpos) {
+ opcode = DecodeType(pos, endpos);
+ if (opcode == 0) {
+ return DecodeASN(pos, endpos);
+ } else if (opcode == 1) {
+ jump = DecodeJump(pos, endpos);
+ if (bits == 0) break;
+ if (ip[ip.size() - bits]) {
+ if (jump >= endpos - pos) break;
+ pos += jump;
+ }
+ bits--;
+ } else if (opcode == 2) {
+ match = DecodeMatch(pos, endpos);
+ matchlen = CountBits(match) - 1;
+ for (uint32_t bit = 0; bit < matchlen; bit++) {
+ if (bits == 0) break;
+ if ((ip[ip.size() - bits]) != ((match >> (matchlen - 1 - bit)) & 1)) {
+ return default_asn;
+ }
+ bits--;
+ }
+ } else if (opcode == 3) {
+ default_asn = DecodeASN(pos, endpos);
+ } else {
+ break;
+ }
+ }
+ return 0; // 0 is not a valid ASN
+}