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runtime-linux/antlr4-runtime/atn/PredictionContext.cpp

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+/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
+ * Use of this file is governed by the BSD 3-clause license that
+ * can be found in the LICENSE.txt file in the project root.
+ */
+
+#include "atn/EmptyPredictionContext.h"
+#include "misc/MurmurHash.h"
+#include "atn/ArrayPredictionContext.h"
+#include "RuleContext.h"
+#include "ParserRuleContext.h"
+#include "atn/RuleTransition.h"
+#include "support/Arrays.h"
+#include "support/CPPUtils.h"
+
+#include "atn/PredictionContext.h"
+
+using namespace antlr4;
+using namespace antlr4::misc;
+using namespace antlr4::atn;
+
+using namespace antlrcpp;
+
+size_t PredictionContext::globalNodeCount = 0;
+const Ref<PredictionContext> PredictionContext::EMPTY = std::make_shared<EmptyPredictionContext>();
+
+//----------------- PredictionContext ----------------------------------------------------------------------------------
+
+PredictionContext::PredictionContext(size_t cachedHashCode) : id(globalNodeCount++), cachedHashCode(cachedHashCode)  {
+}
+
+PredictionContext::~PredictionContext() {
+}
+
+Ref<PredictionContext> PredictionContext::fromRuleContext(const ATN &atn, RuleContext *outerContext) {
+  if (outerContext == nullptr) {
+    return PredictionContext::EMPTY;
+  }
+
+  // if we are in RuleContext of start rule, s, then PredictionContext
+  // is EMPTY. Nobody called us. (if we are empty, return empty)
+  if (outerContext->parent == nullptr || outerContext == &ParserRuleContext::EMPTY) {
+    return PredictionContext::EMPTY;
+  }
+
+  // If we have a parent, convert it to a PredictionContext graph
+  Ref<PredictionContext> parent = PredictionContext::fromRuleContext(atn, dynamic_cast<RuleContext *>(outerContext->parent));
+
+  ATNState *state = atn.states.at(outerContext->invokingState);
+  RuleTransition *transition = (RuleTransition *)state->transitions[0];
+  return SingletonPredictionContext::create(parent, transition->followState->stateNumber);
+}
+
+bool PredictionContext::isEmpty() const {
+  return this == EMPTY.get();
+}
+
+bool PredictionContext::hasEmptyPath() const {
+  // since EMPTY_RETURN_STATE can only appear in the last position, we check last one
+  return getReturnState(size() - 1) == EMPTY_RETURN_STATE;
+}
+
+size_t PredictionContext::hashCode() const {
+  return cachedHashCode;
+}
+
+size_t PredictionContext::calculateEmptyHashCode() {
+  size_t hash = MurmurHash::initialize(INITIAL_HASH);
+  hash = MurmurHash::finish(hash, 0);
+  return hash;
+}
+
+size_t PredictionContext::calculateHashCode(Ref<PredictionContext> parent, size_t returnState) {
+  size_t hash = MurmurHash::initialize(INITIAL_HASH);
+  hash = MurmurHash::update(hash, parent);
+  hash = MurmurHash::update(hash, returnState);
+  hash = MurmurHash::finish(hash, 2);
+  return hash;
+}
+
+size_t PredictionContext::calculateHashCode(const std::vector<Ref<PredictionContext>> &parents,
+                                            const std::vector<size_t> &returnStates) {
+  size_t hash = MurmurHash::initialize(INITIAL_HASH);
+
+  for (auto parent : parents) {
+    hash = MurmurHash::update(hash, parent);
+  }
+
+  for (auto returnState : returnStates) {
+    hash = MurmurHash::update(hash, returnState);
+  }
+
+  return MurmurHash::finish(hash, parents.size() + returnStates.size());
+}
+
+Ref<PredictionContext> PredictionContext::merge(const Ref<PredictionContext> &a,
+  const Ref<PredictionContext> &b, bool rootIsWildcard, PredictionContextMergeCache *mergeCache) {
+  assert(a && b);
+
+  // share same graph if both same
+  if (a == b || *a == *b) {
+    return a;
+  }
+
+  if (is<SingletonPredictionContext>(a) && is<SingletonPredictionContext>(b)) {
+    return mergeSingletons(std::dynamic_pointer_cast<SingletonPredictionContext>(a),
+                           std::dynamic_pointer_cast<SingletonPredictionContext>(b), rootIsWildcard, mergeCache);
+  }
+
+  // At least one of a or b is array.
+  // If one is $ and rootIsWildcard, return $ as * wildcard.
+  if (rootIsWildcard) {
+    if (is<EmptyPredictionContext>(a)) {
+      return a;
+    }
+    if (is<EmptyPredictionContext>(b)) {
+      return b;
+    }
+  }
+
+  // convert singleton so both are arrays to normalize
+  Ref<ArrayPredictionContext> left;
+  if (is<SingletonPredictionContext>(a)) {
+    left = std::make_shared<ArrayPredictionContext>(std::dynamic_pointer_cast<SingletonPredictionContext>(a));
+  } else {
+    left = std::dynamic_pointer_cast<ArrayPredictionContext>(a);
+  }
+  Ref<ArrayPredictionContext> right;
+  if (is<SingletonPredictionContext>(b)) {
+    right = std::make_shared<ArrayPredictionContext>(std::dynamic_pointer_cast<SingletonPredictionContext>(b));
+  } else {
+    right = std::dynamic_pointer_cast<ArrayPredictionContext>(b);
+  }
+  return mergeArrays(left, right, rootIsWildcard, mergeCache);
+}
+
+Ref<PredictionContext> PredictionContext::mergeSingletons(const Ref<SingletonPredictionContext> &a,
+  const Ref<SingletonPredictionContext> &b, bool rootIsWildcard, PredictionContextMergeCache *mergeCache) {
+
+  if (mergeCache != nullptr) { // Can be null if not given to the ATNState from which this call originates.
+    auto existing = mergeCache->get(a, b);
+    if (existing) {
+      return existing;
+    }
+    existing = mergeCache->get(b, a);
+    if (existing) {
+      return existing;
+    }
+  }
+
+  Ref<PredictionContext> rootMerge = mergeRoot(a, b, rootIsWildcard);
+  if (rootMerge) {
+    if (mergeCache != nullptr) {
+      mergeCache->put(a, b, rootMerge);
+    }
+    return rootMerge;
+  }
+
+  Ref<PredictionContext> parentA = a->parent;
+  Ref<PredictionContext> parentB = b->parent;
+  if (a->returnState == b->returnState) { // a == b
+    Ref<PredictionContext> parent = merge(parentA, parentB, rootIsWildcard, mergeCache);
+
+    // If parent is same as existing a or b parent or reduced to a parent, return it.
+    if (parent == parentA) { // ax + bx = ax, if a=b
+      return a;
+    }
+    if (parent == parentB) { // ax + bx = bx, if a=b
+      return b;
+    }
+
+    // else: ax + ay = a'[x,y]
+    // merge parents x and y, giving array node with x,y then remainders
+    // of those graphs.  dup a, a' points at merged array
+    // new joined parent so create new singleton pointing to it, a'
+    Ref<PredictionContext> a_ = SingletonPredictionContext::create(parent, a->returnState);
+    if (mergeCache != nullptr) {
+      mergeCache->put(a, b, a_);
+    }
+    return a_;
+  } else {
+    // a != b payloads differ
+    // see if we can collapse parents due to $+x parents if local ctx
+    Ref<PredictionContext> singleParent;
+    if (a == b || (*parentA == *parentB)) { // ax + bx = [a,b]x
+      singleParent = parentA;
+    }
+    if (singleParent) { // parents are same, sort payloads and use same parent
+      std::vector<size_t> payloads = { a->returnState, b->returnState };
+      if (a->returnState > b->returnState) {
+        payloads[0] = b->returnState;
+        payloads[1] = a->returnState;
+      }
+      std::vector<Ref<PredictionContext>> parents = { singleParent, singleParent };
+      Ref<PredictionContext> a_ = std::make_shared<ArrayPredictionContext>(parents, payloads);
+      if (mergeCache != nullptr) {
+        mergeCache->put(a, b, a_);
+      }
+      return a_;
+    }
+
+    // parents differ and can't merge them. Just pack together
+    // into array; can't merge.
+    // ax + by = [ax,by]
+    Ref<PredictionContext> a_;
+    if (a->returnState > b->returnState) { // sort by payload
+      std::vector<size_t> payloads = { b->returnState, a->returnState };
+      std::vector<Ref<PredictionContext>> parents = { b->parent, a->parent };
+      a_ = std::make_shared<ArrayPredictionContext>(parents, payloads);
+    } else {
+      std::vector<size_t> payloads = {a->returnState, b->returnState};
+      std::vector<Ref<PredictionContext>> parents = { a->parent, b->parent };
+      a_ = std::make_shared<ArrayPredictionContext>(parents, payloads);
+    }
+
+    if (mergeCache != nullptr) {
+      mergeCache->put(a, b, a_);
+    }
+    return a_;
+  }
+}
+
+Ref<PredictionContext> PredictionContext::mergeRoot(const Ref<SingletonPredictionContext> &a,
+  const Ref<SingletonPredictionContext> &b, bool rootIsWildcard) {
+  if (rootIsWildcard) {
+    if (a == EMPTY) { // * + b = *
+      return EMPTY;
+    }
+    if (b == EMPTY) { // a + * = *
+      return EMPTY;
+    }
+  } else {
+    if (a == EMPTY && b == EMPTY) { // $ + $ = $
+      return EMPTY;
+    }
+    if (a == EMPTY) { // $ + x = [$,x]
+      std::vector<size_t> payloads = { b->returnState, EMPTY_RETURN_STATE };
+      std::vector<Ref<PredictionContext>> parents = { b->parent, nullptr };
+      Ref<PredictionContext> joined = std::make_shared<ArrayPredictionContext>(parents, payloads);
+      return joined;
+    }
+    if (b == EMPTY) { // x + $ = [$,x] ($ is always first if present)
+      std::vector<size_t> payloads = { a->returnState, EMPTY_RETURN_STATE };
+      std::vector<Ref<PredictionContext>> parents = { a->parent, nullptr };
+      Ref<PredictionContext> joined = std::make_shared<ArrayPredictionContext>(parents, payloads);
+      return joined;
+    }
+  }
+  return nullptr;
+}
+
+Ref<PredictionContext> PredictionContext::mergeArrays(const Ref<ArrayPredictionContext> &a,
+  const Ref<ArrayPredictionContext> &b, bool rootIsWildcard, PredictionContextMergeCache *mergeCache) {
+
+  if (mergeCache != nullptr) {
+    auto existing = mergeCache->get(a, b);
+    if (existing) {
+      return existing;
+    }
+    existing = mergeCache->get(b, a);
+    if (existing) {
+      return existing;
+    }
+  }
+
+  // merge sorted payloads a + b => M
+  size_t i = 0; // walks a
+  size_t j = 0; // walks b
+  size_t k = 0; // walks target M array
+
+  std::vector<size_t> mergedReturnStates(a->returnStates.size() + b->returnStates.size());
+  std::vector<Ref<PredictionContext>> mergedParents(a->returnStates.size() + b->returnStates.size());
+
+  // walk and merge to yield mergedParents, mergedReturnStates
+  while (i < a->returnStates.size() && j < b->returnStates.size()) {
+    Ref<PredictionContext> a_parent = a->parents[i];
+    Ref<PredictionContext> b_parent = b->parents[j];
+    if (a->returnStates[i] == b->returnStates[j]) {
+      // same payload (stack tops are equal), must yield merged singleton
+      size_t payload = a->returnStates[i];
+      // $+$ = $
+      bool both$ = payload == EMPTY_RETURN_STATE && a_parent && b_parent;
+      bool ax_ax = (a_parent && b_parent) && *a_parent == *b_parent; // ax+ax -> ax
+      if (both$ || ax_ax) {
+        mergedParents[k] = a_parent; // choose left
+        mergedReturnStates[k] = payload;
+      }
+      else { // ax+ay -> a'[x,y]
+        Ref<PredictionContext> mergedParent = merge(a_parent, b_parent, rootIsWildcard, mergeCache);
+        mergedParents[k] = mergedParent;
+        mergedReturnStates[k] = payload;
+      }
+      i++; // hop over left one as usual
+      j++; // but also skip one in right side since we merge
+    } else if (a->returnStates[i] < b->returnStates[j]) { // copy a[i] to M
+      mergedParents[k] = a_parent;
+      mergedReturnStates[k] = a->returnStates[i];
+      i++;
+    }
+    else { // b > a, copy b[j] to M
+      mergedParents[k] = b_parent;
+      mergedReturnStates[k] = b->returnStates[j];
+      j++;
+    }
+    k++;
+  }
+
+  // copy over any payloads remaining in either array
+  if (i < a->returnStates.size()) {
+    for (std::vector<int>::size_type p = i; p < a->returnStates.size(); p++) {
+      mergedParents[k] = a->parents[p];
+      mergedReturnStates[k] = a->returnStates[p];
+      k++;
+    }
+  } else {
+    for (std::vector<int>::size_type p = j; p < b->returnStates.size(); p++) {
+      mergedParents[k] = b->parents[p];
+      mergedReturnStates[k] = b->returnStates[p];
+      k++;
+    }
+  }
+
+  // trim merged if we combined a few that had same stack tops
+  if (k < mergedParents.size()) { // write index < last position; trim
+    if (k == 1) { // for just one merged element, return singleton top
+      Ref<PredictionContext> a_ = SingletonPredictionContext::create(mergedParents[0], mergedReturnStates[0]);
+      if (mergeCache != nullptr) {
+        mergeCache->put(a, b, a_);
+      }
+      return a_;
+    }
+    mergedParents.resize(k);
+    mergedReturnStates.resize(k);
+  }
+
+  Ref<ArrayPredictionContext> M = std::make_shared<ArrayPredictionContext>(mergedParents, mergedReturnStates);
+
+  // if we created same array as a or b, return that instead
+  // TO_DO: track whether this is possible above during merge sort for speed
+  if (*M == *a) {
+    if (mergeCache != nullptr) {
+      mergeCache->put(a, b, a);
+    }
+    return a;
+  }
+  if (*M == *b) {
+    if (mergeCache != nullptr) {
+      mergeCache->put(a, b, b);
+    }
+    return b;
+  }
+
+  // ml: this part differs from Java code. We have to recreate the context as the parents array is copied on creation.
+  if (combineCommonParents(mergedParents)) {
+    mergedReturnStates.resize(mergedParents.size());
+    M = std::make_shared<ArrayPredictionContext>(mergedParents, mergedReturnStates);
+  }
+
+  if (mergeCache != nullptr) {
+    mergeCache->put(a, b, M);
+  }
+  return M;
+}
+
+bool PredictionContext::combineCommonParents(std::vector<Ref<PredictionContext>> &parents) {
+
+  std::set<Ref<PredictionContext>> uniqueParents;
+  for (size_t p = 0; p < parents.size(); ++p) {
+    Ref<PredictionContext> parent = parents[p];
+    if (uniqueParents.find(parent) == uniqueParents.end()) { // don't replace
+      uniqueParents.insert(parent);
+    }
+  }
+
+  for (size_t p = 0; p < parents.size(); ++p) {
+    parents[p] = *uniqueParents.find(parents[p]);
+  }
+
+  return true;
+}
+
+std::string PredictionContext::toDOTString(const Ref<PredictionContext> &context) {
+  if (context == nullptr) {
+    return "";
+  }
+
+  std::stringstream ss;
+  ss << "digraph G {\n" << "rankdir=LR;\n";
+
+  std::vector<Ref<PredictionContext>> nodes = getAllContextNodes(context);
+  std::sort(nodes.begin(), nodes.end(), [](const Ref<PredictionContext> &o1, const Ref<PredictionContext> &o2) {
+    return o1->id - o2->id;
+  });
+
+  for (auto current : nodes) {
+    if (is<SingletonPredictionContext>(current)) {
+      std::string s = std::to_string(current->id);
+      ss << "  s" << s;
+      std::string returnState = std::to_string(current->getReturnState(0));
+      if (is<EmptyPredictionContext>(current)) {
+        returnState = "$";
+      }
+      ss << " [label=\"" << returnState << "\"];\n";
+      continue;
+    }
+    Ref<ArrayPredictionContext> arr = std::static_pointer_cast<ArrayPredictionContext>(current);
+    ss << "  s" << arr->id << " [shape=box, label=\"" << "[";
+    bool first = true;
+    for (auto inv : arr->returnStates) {
+      if (!first) {
+       ss << ", ";
+      }
+      if (inv == EMPTY_RETURN_STATE) {
+        ss << "$";
+      } else {
+        ss << inv;
+      }
+      first = false;
+    }
+    ss << "]";
+    ss << "\"];\n";
+  }
+
+  for (auto current : nodes) {
+    if (current == EMPTY) {
+      continue;
+    }
+    for (size_t i = 0; i < current->size(); i++) {
+      if (!current->getParent(i)) {
+        continue;
+      }
+      ss << "  s" << current->id << "->" << "s" << current->getParent(i)->id;
+      if (current->size() > 1) {
+        ss << " [label=\"parent[" << i << "]\"];\n";
+      } else {
+        ss << ";\n";
+      }
+    }
+  }
+
+  ss << "}\n";
+  return ss.str();
+}
+
+// The "visited" map is just a temporary structure to control the retrieval process (which is recursive).
+Ref<PredictionContext> PredictionContext::getCachedContext(const Ref<PredictionContext> &context,
+  PredictionContextCache &contextCache, std::map<Ref<PredictionContext>, Ref<PredictionContext>> &visited) {
+  if (context->isEmpty()) {
+    return context;
+  }
+
+  {
+    auto iterator = visited.find(context);
+    if (iterator != visited.end())
+      return iterator->second; // Not necessarly the same as context.
+  }
+
+  auto iterator = contextCache.find(context);
+  if (iterator != contextCache.end()) {
+    visited[context] = *iterator;
+
+    return *iterator;
+  }
+
+  bool changed = false;
+
+  std::vector<Ref<PredictionContext>> parents(context->size());
+  for (size_t i = 0; i < parents.size(); i++) {
+    Ref<PredictionContext> parent = getCachedContext(context->getParent(i), contextCache, visited);
+    if (changed || parent != context->getParent(i)) {
+      if (!changed) {
+        parents.clear();
+        for (size_t j = 0; j < context->size(); j++) {
+          parents.push_back(context->getParent(j));
+        }
+
+        changed = true;
+      }
+
+      parents[i] = parent;
+    }
+  }
+
+  if (!changed) {
+    contextCache.insert(context);
+    visited[context] = context;
+
+    return context;
+  }
+
+  Ref<PredictionContext> updated;
+  if (parents.empty()) {
+    updated = EMPTY;
+  } else if (parents.size() == 1) {
+    updated = SingletonPredictionContext::create(parents[0], context->getReturnState(0));
+    contextCache.insert(updated);
+  } else {
+    updated = std::make_shared<ArrayPredictionContext>(parents, std::dynamic_pointer_cast<ArrayPredictionContext>(context)->returnStates);
+    contextCache.insert(updated);
+  }
+
+  visited[updated] = updated;
+  visited[context] = updated;
+
+  return updated;
+}
+
+std::vector<Ref<PredictionContext>> PredictionContext::getAllContextNodes(const Ref<PredictionContext> &context) {
+  std::vector<Ref<PredictionContext>> nodes;
+  std::set<PredictionContext *> visited;
+  getAllContextNodes_(context, nodes, visited);
+  return nodes;
+}
+
+
+void PredictionContext::getAllContextNodes_(const Ref<PredictionContext> &context, std::vector<Ref<PredictionContext>> &nodes,
+  std::set<PredictionContext *> &visited) {
+
+  if (visited.find(context.get()) != visited.end()) {
+    return; // Already done.
+  }
+
+  visited.insert(context.get());
+  nodes.push_back(context);
+
+  for (size_t i = 0; i < context->size(); i++) {
+    getAllContextNodes_(context->getParent(i), nodes, visited);
+  }
+}
+
+std::string PredictionContext::toString() const {
+
+  return antlrcpp::toString(this);
+}
+
+std::string PredictionContext::toString(Recognizer * /*recog*/) const {
+  return toString();
+}
+
+std::vector<std::string> PredictionContext::toStrings(Recognizer *recognizer, int currentState) {
+  return toStrings(recognizer, EMPTY, currentState);
+}
+
+std::vector<std::string> PredictionContext::toStrings(Recognizer *recognizer, const Ref<PredictionContext> &stop, int currentState) {
+
+  std::vector<std::string> result;
+
+  for (size_t perm = 0; ; perm++) {
+    size_t offset = 0;
+    bool last = true;
+    PredictionContext *p = this;
+    size_t stateNumber = currentState;
+
+    std::stringstream ss;
+    ss << "[";
+    bool outerContinue = false;
+    while (!p->isEmpty() && p != stop.get()) {
+      size_t index = 0;
+      if (p->size() > 0) {
+        size_t bits = 1;
+        while ((1ULL << bits) < p->size()) {
+          bits++;
+        }
+
+        size_t mask = (1 << bits) - 1;
+        index = (perm >> offset) & mask;
+        last &= index >= p->size() - 1;
+        if (index >= p->size()) {
+          outerContinue = true;
+          break;
+        }
+        offset += bits;
+      }
+
+      if (recognizer != nullptr) {
+        if (ss.tellp() > 1) {
+          // first char is '[', if more than that this isn't the first rule
+          ss << ' ';
+        }
+
+        const ATN &atn = recognizer->getATN();
+        ATNState *s = atn.states[stateNumber];
+        std::string ruleName = recognizer->getRuleNames()[s->ruleIndex];
+        ss << ruleName;
+      } else if (p->getReturnState(index) != EMPTY_RETURN_STATE) {
+        if (!p->isEmpty()) {
+          if (ss.tellp() > 1) {
+            // first char is '[', if more than that this isn't the first rule
+            ss << ' ';
+          }
+
+          ss << p->getReturnState(index);
+        }
+      }
+      stateNumber = p->getReturnState(index);
+      p = p->getParent(index).get();
+    }
+
+    if (outerContinue)
+      continue;
+
+    ss << "]";
+    result.push_back(ss.str());
+
+    if (last) {
+      break;
+    }
+  }
+
+  return result;
+}
+
+//----------------- PredictionContextMergeCache ------------------------------------------------------------------------
+
+Ref<PredictionContext> PredictionContextMergeCache::put(Ref<PredictionContext> const& key1, Ref<PredictionContext> const& key2,
+                                                        Ref<PredictionContext> const& value) {
+  Ref<PredictionContext> previous;
+
+  auto iterator = _data.find(key1);
+  if (iterator == _data.end())
+    _data[key1][key2] = value;
+  else {
+    auto iterator2 = iterator->second.find(key2);
+    if (iterator2 != iterator->second.end())
+      previous = iterator2->second;
+    iterator->second[key2] = value;
+  }
+
+  return previous;
+}
+
+Ref<PredictionContext> PredictionContextMergeCache::get(Ref<PredictionContext> const& key1, Ref<PredictionContext> const& key2) {
+  auto iterator = _data.find(key1);
+  if (iterator == _data.end())
+    return nullptr;
+
+  auto iterator2 = iterator->second.find(key2);
+  if (iterator2 == iterator->second.end())
+    return nullptr;
+
+  return iterator2->second;
+}
+
+void PredictionContextMergeCache::clear() {
+  _data.clear();
+}
+
+std::string PredictionContextMergeCache::toString() const {
+  std::string result;
+  for (auto pair : _data)
+    for (auto pair2 : pair.second)
+      result += pair2.second->toString() + "\n";
+
+  return result;
+}
+
+size_t PredictionContextMergeCache::count() const {
+  size_t result = 0;
+  for (auto entry : _data)
+    result += entry.second.size();
+  return result;
+}
+