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Regex: optimize parsing a bit

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This commit is contained in:
Maxime Coste 2017-11-30 14:32:29 +08:00
parent c1f0efa3f4
commit b91f43b031
1 changed files with 35 additions and 38 deletions
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73
src/regex_impl.cc
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@ -189,28 +189,16 @@ private:
return {};
}
bool accept(StringView expected)
{
auto it = m_pos.base();
for (auto expected_it = expected.begin(); expected_it != expected.end(); ++expected_it)
{
if (it == m_regex.end() or *it++ != *expected_it)
return false;
}
m_pos = Iterator{it, m_regex};
return true;
}
bool modifiers()
{
if (accept("(?i)"))
auto it = m_pos.base();
if (m_regex.end() - it >= 4 and *it++ == '(' and *it++ == '?')
{
m_ignore_case = true;
return true;
}
if (accept("(?I)"))
{
m_ignore_case = false;
auto m = *it++;
if ((m != 'i' and m != 'I') or *it++ != ')')
return false;
m_ignore_case = (m == 'i');
m_pos = Iterator{it, m_regex};
return true;
}
return false;
@ -239,25 +227,29 @@ private:
break;
case '(':
{
Optional<ParsedRegex::Op> lookaround_op;
constexpr struct { StringView prefix; ParsedRegex::Op op; } lookarounds[] = {
{ "(?=", ParsedRegex::LookAhead },
{ "(?!", ParsedRegex::NegativeLookAhead },
{ "(?<=", ParsedRegex::LookBehind },
{ "(?<!", ParsedRegex::NegativeLookBehind }
};
for (auto& lookaround : lookarounds)
auto it = m_pos.base()+1;
if (m_regex.end() - it <= 2 or *it++ != '?')
return {};
ParsedRegex::Op op;
switch (*it++)
{
if (accept(lookaround.prefix))
case '=': op = ParsedRegex::LookAhead; break;
case '!': op = ParsedRegex::NegativeLookAhead; break;
case '<':
{
lookaround_op = lookaround.op;
switch (*it++)
{
case '=': op = ParsedRegex::LookBehind; break;
case '!': op = ParsedRegex::NegativeLookBehind; break;
default: return {};
}
break;
}
default: return {};
}
if (not lookaround_op)
return {};
NodeIndex lookaround = alternative(*lookaround_op);
m_pos = Iterator{it, m_regex};
NodeIndex lookaround = alternative(op);
if (at_end() or *m_pos++ != ')')
parse_error("unclosed parenthesis");
@ -273,15 +265,20 @@ private:
if (at_end())
return {};
const Codepoint cp = *m_pos;
switch (cp)
switch (const Codepoint cp = *m_pos)
{
case '.': ++m_pos; return new_node(ParsedRegex::AnyChar);
case '(':
{
++m_pos;
const bool capture = not accept("?:");
NodeIndex content = disjunction(capture ? m_parsed_regex.capture_count++ : -1);
auto captures = [this, it = (++m_pos).base()]() mutable {
if (m_regex.end() - it >= 2 and *it++ == '?' and *it++ == ':')
{
m_pos = Iterator{it, m_regex};
return false;
}
return true;
};
NodeIndex content = disjunction(captures() ? m_parsed_regex.capture_count++ : -1);
if (at_end() or *m_pos++ != ')')
parse_error("unclosed parenthesis");
return content;