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Regex: Implement lookarounds for fixed literal strings
We do not support anything else than a plain literal string for lookarounds.
This commit is contained in:
Maxime Coste
parent
e96cd29f0e
commit
0bdfdac5c5
@ -29,6 +29,10 @@ struct ParsedRegex
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SubjectBegin,
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SubjectEnd,
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ResetStart,
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LookAhead,
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LookBehind,
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NegativeLookAhead,
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NegativeLookBehind,
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};
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struct Quantifier
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@ -116,9 +120,9 @@ private:
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return res;
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}
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AstNodePtr alternative()
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AstNodePtr alternative(ParsedRegex::Op op = ParsedRegex::Sequence)
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{
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AstNodePtr res = new_node(ParsedRegex::Sequence);
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AstNodePtr res = new_node(op);
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while (auto node = term())
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res->children.push_back(std::move(node));
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if (res->children.empty())
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@ -175,8 +179,44 @@ private:
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case '.': ++m_pos; return new_node(ParsedRegex::AnyChar);
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case '(':
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{
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++m_pos;
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auto content = disjunction(m_parsed_regex.capture_count++);
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auto advance = [&]() {
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if (++m_pos == m_regex.end())
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parse_error("unclosed parenthesis");
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return *m_pos;
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};
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AstNodePtr content;
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if (advance() == '?')
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{
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auto c = advance();
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if (c == ':')
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content = disjunction(-1);
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else if (contains("=!<", c))
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{
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bool behind = false;
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if (c == '<')
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{
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advance();
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behind = true;
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}
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auto type = *m_pos++;
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if (type == '=')
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content = alternative(behind ? ParsedRegex::LookBehind
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: ParsedRegex::LookAhead);
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else if (type == '!')
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content = alternative(behind ? ParsedRegex::NegativeLookBehind
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: ParsedRegex::NegativeLookAhead);
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else
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parse_error("invalid disjunction");
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validate_lookaround(content);
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}
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else
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parse_error("invalid disjunction");
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}
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else
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content = disjunction(m_parsed_regex.capture_count++);
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if (at_end() or *m_pos != ')')
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parse_error("unclosed parenthesis");
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@ -245,7 +285,7 @@ private:
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if (contains("^$\\.*+?()[]{}|", cp)) // SyntaxCharacter
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return new_node(ParsedRegex::Literal, cp);
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parse_error("unknown atom escape");
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parse_error(format("unknown atom escape '{}'", cp));
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}
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AstNodePtr character_class()
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@ -395,6 +435,13 @@ private:
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StringView{m_pos.base(), m_regex.end()}));
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}
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void validate_lookaround(const AstNodePtr& node)
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{
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for (auto& child : node->children)
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if (child->op != ParsedRegex::Literal)
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parse_error("Lookaround can only contain literals");
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}
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ParsedRegex m_parsed_regex;
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StringView m_regex;
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Iterator m_pos;
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@ -406,6 +453,11 @@ private:
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bool neg;
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};
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StringView peek(ByteCount count)
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{
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return StringView{m_pos.base(), m_regex.end()}.substr(0, count);
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}
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static const CharacterClassEscape character_class_escapes[8];
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};
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@ -439,6 +491,10 @@ struct CompiledRegex
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NotWordBoundary,
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SubjectBegin,
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SubjectEnd,
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LookAhead,
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LookBehind,
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NegativeLookAhead,
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NegativeLookBehind,
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};
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using Offset = unsigned;
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@ -516,6 +572,22 @@ private:
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break;
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}
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case ParsedRegex::LookAhead:
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push_op(CompiledRegex::LookAhead);
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push_string(node->children);
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break;
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case ParsedRegex::LookBehind:
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push_op(CompiledRegex::LookBehind);
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push_string(node->children, true);
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break;
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case ParsedRegex::NegativeLookAhead:
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push_op(CompiledRegex::NegativeLookAhead);
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push_string(node->children);
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break;
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case ParsedRegex::NegativeLookBehind:
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push_op(CompiledRegex::NegativeLookBehind);
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push_string(node->children, true);
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break;
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case ParsedRegex::LineStart:
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push_op(CompiledRegex::LineStart);
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break;
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@ -631,6 +703,20 @@ private:
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utf8::dump(std::back_inserter(m_program.bytecode), cp);
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}
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void push_string(const Vector<ParsedRegex::AstNodePtr>& codepoints, bool reversed = false)
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{
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if (codepoints.size() > 127)
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throw runtime_error{"Too long literal string"};
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push_byte(codepoints.size());
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if (reversed)
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for (auto& cp : codepoints | reverse())
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push_codepoint(cp->value);
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else
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for (auto& cp : codepoints)
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push_codepoint(cp->value);
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}
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CompiledRegex m_program;
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const ParsedRegex& m_parsed_regex;
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};
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@ -687,6 +773,27 @@ void dump_regex(const CompiledRegex& program)
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case CompiledRegex::SubjectEnd:
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printf("subject end\n");
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break;
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case CompiledRegex::LookAhead:
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case CompiledRegex::NegativeLookAhead:
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case CompiledRegex::LookBehind:
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case CompiledRegex::NegativeLookBehind:
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{
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int count = *pos++;
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StringView str{pos, pos + count};
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const char* name = nullptr;
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if (op == CompiledRegex::LookAhead)
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name = "look ahead";
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if (op == CompiledRegex::NegativeLookAhead)
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name = "negative look ahead";
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if (op == CompiledRegex::LookBehind)
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name = "look behind";
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if (op == CompiledRegex::NegativeLookBehind)
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name = "negative look behind";
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printf("%s (%s)\n", name, (const char*)str.zstr());
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pos += count;
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break;
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}
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case CompiledRegex::Match:
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printf("match\n");
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}
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@ -783,6 +890,32 @@ struct ThreadedRegexVM
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if (m_pos != m_end)
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return StepResult::Failed;
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break;
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case CompiledRegex::LookAhead:
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case CompiledRegex::NegativeLookAhead:
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{
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int count = *thread.inst++;
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for (auto it = m_pos; count and it != m_end; ++it, --count)
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if (*it != utf8::read(thread.inst))
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break;
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if ((op == CompiledRegex::LookAhead and count != 0) or
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(op == CompiledRegex::NegativeLookAhead and count == 0))
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return StepResult::Failed;
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thread.inst = utf8::advance(thread.inst, prog_end, CharCount{count - 1});
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break;
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}
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case CompiledRegex::LookBehind:
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case CompiledRegex::NegativeLookBehind:
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{
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int count = *thread.inst++;
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for (auto it = m_pos-1; count and it >= m_begin; --it, --count)
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if (*it != utf8::read(thread.inst))
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break;
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if ((op == CompiledRegex::LookBehind and count != 0) or
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(op == CompiledRegex::NegativeLookBehind and count == 0))
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return StepResult::Failed;
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thread.inst = utf8::advance(thread.inst, prog_end, CharCount{count - 1});
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break;
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}
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case CompiledRegex::Match:
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thread.inst = nullptr;
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return StepResult::Matched;
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@ -823,7 +956,7 @@ struct ThreadedRegexVM
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m_threads.erase(std::remove_if(m_threads.begin(), m_threads.end(),
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[](const Thread& t) { return t.inst == nullptr; }), m_threads.end());
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if (m_threads.empty())
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return false;
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return found_match;
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}
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// Step remaining threads to see if they match without consuming anything else
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@ -1034,6 +1167,30 @@ auto test_regex = UnitTest{[]{
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kak_assert(vm.exec("foooo", true, true));
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kak_assert(StringView{vm.m_captures[2], vm.m_captures[3]} == "fo");
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}
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{
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TestVM vm{R"((?=foo).)"};
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kak_assert(vm.exec("barfoo", false, true));
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kak_assert(StringView{vm.m_captures[0], vm.m_captures[1]} == "f");
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}
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{
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TestVM vm{R"((?!foo)...)"};
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kak_assert(not vm.exec("foo"));
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kak_assert(vm.exec("qux"));
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}
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{
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TestVM vm{R"(...(?<=foo))"};
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kak_assert(vm.exec("foo"));
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kak_assert(not vm.exec("qux"));
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}
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{
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TestVM vm{R"(...(?<!foo))"};
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kak_assert(not vm.exec("foo"));
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kak_assert(vm.exec("qux"));
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}
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}};
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}
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