blob: ff12d4a449f887769bb36a5d61e264e29d3a851d [file] [log] [blame]
// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <algorithm>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include "src/torque/ast.h"
#include "src/torque/earley-parser.h"
#include "src/torque/utils.h"
namespace v8 {
namespace internal {
namespace torque {
namespace {
struct LineAndColumnTracker {
LineAndColumn previous{0, 0};
LineAndColumn current{0, 0};
void Advance(InputPosition from, InputPosition to) {
previous = current;
while (from != to) {
if (*from == '\n') {
current.line += 1;
current.column = 0;
} else {
current.column += 1;
}
++from;
}
}
SourcePosition ToSourcePosition() {
return {CurrentSourceFile::Get(), previous, current};
}
};
} // namespace
base::Optional<ParseResult> Rule::RunAction(const Item* completed_item,
const LexerResult& tokens) const {
std::vector<ParseResult> results;
for (const Item* child : completed_item->Children()) {
if (!child) continue;
base::Optional<ParseResult> child_result =
child->left()->RunAction(child, tokens);
if (child_result) results.push_back(std::move(*child_result));
}
MatchedInput matched_input = completed_item->GetMatchedInput(tokens);
CurrentSourcePosition::Scope pos_scope(matched_input.pos);
ParseResultIterator iterator(std::move(results), matched_input);
return action_(&iterator);
}
Symbol& Symbol::operator=(std::initializer_list<Rule> rules) {
rules_.clear();
for (const Rule& rule : rules) {
AddRule(rule);
}
return *this;
}
std::vector<const Item*> Item::Children() const {
std::vector<const Item*> children;
for (const Item* current = this; current->prev_; current = current->prev_) {
children.push_back(current->child_);
}
// The above loop collects the child nodes in reversed order.
std::reverse(children.begin(), children.end());
DCHECK_EQ(children.size(), right().size());
return children;
}
std::string Item::SplitByChildren(const LexerResult& tokens) const {
if (right().size() == 1) {
if (const Item* child = Children()[0])
return child->SplitByChildren(tokens);
}
std::stringstream s;
bool first = true;
for (const Item* item : Children()) {
if (!item) continue;
if (!first) s << " ";
s << item->GetMatchedInput(tokens).ToString();
first = false;
}
return s.str();
}
void Item::CheckAmbiguity(const Item& other, const LexerResult& tokens) const {
DCHECK(*this == other);
if (child_ != other.child_) {
std::stringstream s;
s << "Ambiguous grammer rules for \""
<< child_->GetMatchedInput(tokens).ToString() << "\":\n "
<< child_->SplitByChildren(tokens) << "\nvs\n "
<< other.child_->SplitByChildren(tokens);
ReportError(s.str());
}
if (prev_ != other.prev_) {
std::stringstream s;
s << "Ambiguous grammer rules for \"" << GetMatchedInput(tokens).ToString()
<< "\":\n " << SplitByChildren(tokens) << " ...\nvs\n "
<< other.SplitByChildren(tokens) << " ...";
ReportError(s.str());
}
}
LexerResult Lexer::RunLexer(const std::string& input) {
LexerResult result;
InputPosition const begin = input.c_str();
InputPosition const end = begin + input.size();
InputPosition pos = begin;
InputPosition token_start = pos;
LineAndColumnTracker line_column_tracker;
match_whitespace_(&pos);
line_column_tracker.Advance(token_start, pos);
while (pos != end) {
token_start = pos;
Symbol* symbol = MatchToken(&pos, end);
InputPosition token_end = pos;
line_column_tracker.Advance(token_start, token_end);
if (!symbol) {
CurrentSourcePosition::Scope pos_scope(
line_column_tracker.ToSourcePosition());
ReportError("Lexer Error: unknown token " +
StringLiteralQuote(std::string(
token_start, token_start + std::min<ptrdiff_t>(
end - token_start, 10))));
}
result.token_symbols.push_back(symbol);
result.token_contents.push_back(
{token_start, pos, line_column_tracker.ToSourcePosition()});
match_whitespace_(&pos);
line_column_tracker.Advance(token_end, pos);
}
// Add an additional token position to simplify corner cases.
line_column_tracker.Advance(token_start, pos);
result.token_contents.push_back(
{pos, pos, line_column_tracker.ToSourcePosition()});
return result;
}
Symbol* Lexer::MatchToken(InputPosition* pos, InputPosition end) {
InputPosition token_start = *pos;
Symbol* symbol = nullptr;
// Find longest matching pattern.
for (std::pair<const PatternFunction, Symbol>& pair : patterns_) {
InputPosition token_end = token_start;
PatternFunction matchPattern = pair.first;
if (matchPattern(&token_end) && token_end > *pos) {
*pos = token_end;
symbol = &pair.second;
}
}
// Check if matched pattern coincides with a keyword. Prefer the keyword in
// this case.
if (*pos != token_start) {
auto found_keyword = keywords_.find(std::string(token_start, *pos));
if (found_keyword != keywords_.end()) {
return &found_keyword->second;
}
return symbol;
}
// Now check for a keyword (that doesn't overlap with a pattern).
// Iterate from the end to ensure that if one keyword is a prefix of another,
// we first try to match the longer one.
for (auto it = keywords_.rbegin(); it != keywords_.rend(); ++it) {
const std::string& keyword = it->first;
if (static_cast<size_t>(end - *pos) < keyword.size()) continue;
if (keyword == std::string(*pos, *pos + keyword.size())) {
*pos += keyword.size();
return &it->second;
}
}
return nullptr;
}
// This is an implementation of Earley's parsing algorithm
// (https://en.wikipedia.org/wiki/Earley_parser).
const Item* RunEarleyAlgorithm(
Symbol* start, const LexerResult& tokens,
std::unordered_set<Item, base::hash<Item>>* processed) {
// Worklist for items at the current position.
std::vector<Item> worklist;
// Worklist for items at the next position.
std::vector<Item> future_items;
CurrentSourcePosition::Scope source_position(
SourcePosition{CurrentSourceFile::Get(), {0, 0}, {0, 0}});
std::vector<const Item*> completed_items;
std::unordered_map<std::pair<size_t, Symbol*>, std::set<const Item*>,
base::hash<std::pair<size_t, Symbol*>>>
waiting;
std::vector<const Item*> debug_trace;
// Start with one top_level symbol mapping to the start symbol of the grammar.
// This simplifies things because the start symbol might have several
// rules.
Symbol top_level;
top_level.AddRule(Rule({start}));
worklist.push_back(Item{top_level.rule(0), 0, 0, 0});
size_t input_length = tokens.token_symbols.size();
for (size_t pos = 0; pos <= input_length; ++pos) {
while (!worklist.empty()) {
auto insert_result = processed->insert(worklist.back());
const Item& item = *insert_result.first;
DCHECK_EQ(pos, item.pos());
MatchedInput last_token = tokens.token_contents[pos];
CurrentSourcePosition::Get() = last_token.pos;
bool is_new = insert_result.second;
if (!is_new) item.CheckAmbiguity(worklist.back(), tokens);
worklist.pop_back();
if (!is_new) continue;
debug_trace.push_back(&item);
if (item.IsComplete()) {
// 'Complete' phase: Advance all items that were waiting to match this
// symbol next.
for (const Item* parent : waiting[{item.start(), item.left()}]) {
worklist.push_back(parent->Advance(pos, &item));
}
} else {
Symbol* next = item.NextSymbol();
// 'Scan' phase: Check if {next} is the next symbol in the input (this
// is never the case if {next} is a non-terminal).
if (pos < tokens.token_symbols.size() &&
tokens.token_symbols[pos] == next) {
future_items.push_back(item.Advance(pos + 1, nullptr));
}
// 'Predict' phase: Add items for every rule of the non-terminal.
if (!next->IsTerminal()) {
// Remember that this item is waiting for completion with {next}.
waiting[{pos, next}].insert(&item);
}
for (size_t i = 0; i < next->rule_number(); ++i) {
Rule* rule = next->rule(i);
auto already_completed =
processed->find(Item{rule, rule->right().size(), pos, pos});
// As discussed in section 3 of
// Aycock, John, and R. Nigel Horspool. "Practical earley
// parsing." The Computer Journal 45.6 (2002): 620-630.
// Earley parsing has the following problem with epsilon rules:
// When we complete an item that started at the current position
// (that is, it matched zero tokens), we might not yet have
// predicted all items it can complete with. Thus we check for the
// existence of such items here and complete them immediately.
if (already_completed != processed->end()) {
worklist.push_back(item.Advance(pos, &*already_completed));
} else {
worklist.push_back(Item{rule, 0, pos, pos});
}
}
}
}
std::swap(worklist, future_items);
}
auto final_item =
processed->find(Item{top_level.rule(0), 1, 0, input_length});
if (final_item != processed->end()) {
// Success: The {top_level} rule matches the complete input.
return final_item->Children()[0];
}
std::string reason;
const Item& last_item = *debug_trace.back();
if (last_item.pos() < tokens.token_symbols.size()) {
std::string next_token = tokens.token_contents[last_item.pos()].ToString();
reason = "unexpected token \"" + next_token + "\"";
} else {
reason = "unexpected end of input";
}
ReportError("Parser Error: " + reason);
}
// static
bool Grammar::MatchChar(int (*char_class)(int), InputPosition* pos) {
if (**pos && char_class(static_cast<unsigned char>(**pos))) {
++*pos;
return true;
}
return false;
}
// static
bool Grammar::MatchChar(bool (*char_class)(char), InputPosition* pos) {
if (**pos && char_class(**pos)) {
++*pos;
return true;
}
return false;
}
// static
bool Grammar::MatchString(const char* s, InputPosition* pos) {
InputPosition current = *pos;
for (; *s != 0; ++s, ++current) {
if (*s != *current) return false;
}
*pos = current;
return true;
}
// static
bool Grammar::MatchAnyChar(InputPosition* pos) {
return MatchChar([](char c) { return true; }, pos);
}
} // namespace torque
} // namespace internal
} // namespace v8