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smallwrite: construct DFA states in BFS order

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This commit is contained in:
Justin Viiret 2017-04-11 14:21:02 +10:00 committed by Matthew Barr
parent 10f52346ca
commit 388c16c550
1 changed files with 32 additions and 16 deletions
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48
src/smallwrite/smallwrite_build.cpp
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@ -444,21 +444,14 @@ bool isSaneTrie(const LitTrie &trie) {
*/
static
void buildAutomaton(LitTrie &trie,
map<LitTrieVertex, LitTrieVertex> &failure_map) {
map<LitTrieVertex, LitTrieVertex> &failure_map,
vector<LitTrieVertex> &ordering) {
assert(isSaneTrie(trie));
// Find our failure transitions and reports.
vector<LitTrieVertex> ordering;
ACVisitor ac_vis(trie, failure_map, ordering);
boost::breadth_first_search(trie, trie.root, visitor(ac_vis));
// Renumber with BFS ordering, which is assumed by other DFA construction
// code (i.e. Sherman state computation).
size_t idx = 0;
for (auto v : ordering) {
trie[v].index = idx++;
}
// Compute missing edges from failure map.
for (auto v : ordering) {
DEBUG_PRINTF("vertex %zu\n", trie[v].index);
@ -537,13 +530,35 @@ u16 buildAlphabet(const LitTrie &trie, bool nocase,
return i;
}
/**
* \brief Calculate state mapping, from vertex in trie to state index in BFS
* ordering.
*/
static
unordered_map<LitTrieVertex, u32>
makeStateMap(const LitTrie &trie, const vector<LitTrieVertex> &ordering) {
unordered_map<LitTrieVertex, u32> state_ids;
state_ids.reserve(num_vertices(trie));
u32 idx = DEAD_STATE + 1;
state_ids.emplace(trie.root, idx++);
for (auto v : ordering) {
state_ids.emplace(v, idx++);
}
assert(state_ids.size() == num_vertices(trie));
return state_ids;
}
/** \brief Construct a raw_dfa from a literal trie. */
static
unique_ptr<raw_dfa> buildDfa(LitTrie &trie, bool nocase) {
DEBUG_PRINTF("trie has %zu states\n", num_vertices(trie));
vector<LitTrieVertex> ordering;
map<LitTrieVertex, LitTrieVertex> failure_map;
buildAutomaton(trie, failure_map);
buildAutomaton(trie, failure_map, ordering);
// Construct DFA states in BFS order.
const auto state_ids = makeStateMap(trie, ordering);
auto rdfa = make_unique<raw_dfa>(NFA_OUTFIX);
@ -553,7 +568,8 @@ unique_ptr<raw_dfa> buildDfa(LitTrie &trie, bool nocase) {
rdfa->alpha_size = buildAlphabet(trie, nocase, alpha, unalpha);
// Construct states and transitions.
const u16 root_state = DEAD_STATE + 1;
const u16 root_state = state_ids.at(trie.root);
assert(root_state == DEAD_STATE + 1);
rdfa->start_anchored = root_state;
rdfa->start_floating = root_state;
rdfa->states.resize(num_vertices(trie) + 1, dstate(rdfa->alpha_size));
@ -563,8 +579,8 @@ unique_ptr<raw_dfa> buildDfa(LitTrie &trie, bool nocase) {
rdfa->states[DEAD_STATE].next.end(), DEAD_STATE);
for (auto u : vertices_range(trie)) {
auto u_state = trie[u].index + 1;
DEBUG_PRINTF("state %zu\n", u_state);
auto u_state = state_ids.at(u);
DEBUG_PRINTF("state %u\n", u_state);
assert(u_state < rdfa->states.size());
auto &ds = rdfa->states[u_state];
ds.reports = trie[u].reports;
@ -577,7 +593,7 @@ unique_ptr<raw_dfa> buildDfa(LitTrie &trie, bool nocase) {
ds.daddy = DEAD_STATE;
} else {
assert(contains(failure_map, u));
ds.daddy = trie[failure_map.at(u)].index + 1;
ds.daddy = state_ids.at(failure_map.at(u));
}
// By default, transition back to the root.
@ -590,10 +606,10 @@ unique_ptr<raw_dfa> buildDfa(LitTrie &trie, bool nocase) {
if (v == trie.root) {
continue;
}
auto v_state = trie[v].index + 1;
auto v_state = state_ids.at(v);
assert((u16)trie[v].c < alpha.size());
u16 sym = alpha[trie[v].c];
DEBUG_PRINTF("edge to %zu on 0x%02x (sym %u)\n", v_state,
DEBUG_PRINTF("edge to %u on 0x%02x (sym %u)\n", v_state,
trie[v].c, sym);
assert(sym < ds.next.size());
assert(ds.next[sym] == root_state);