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Regex: Improve comments and constify some variables

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Reword various comments to make some tricky parts of the regex
engine easier to understand.
This commit is contained in:
Maxime Coste 2018-02-24 17:21:15 +11:00
parent 1c4f3534e1
commit 933ac4d3d5
2 changed files with 8 additions and 9 deletions
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15
src/regex_impl.cc
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@ -796,8 +796,6 @@ private:
auto& quantifier = node.quantifier;
// TODO reverse, invert the way we write optional quantifiers ?
if (quantifier.allows_none())
{
auto split_pos = push_inst(quantifier.greedy ? CompiledRegex::Split_PrioritizeParent
@ -814,7 +812,6 @@ private:
push_inst(quantifier.greedy ? CompiledRegex::Split_PrioritizeChild
: CompiledRegex::Split_PrioritizeParent,
inner_pos);
// Write the node as an optional match for the min -> max counts
else for (int i = std::max((int16_t)1, quantifier.min); // STILL UGLY !
i < quantifier.max; ++i)
@ -831,7 +828,7 @@ private:
return start_pos;
}
// Add an set of instruction prefix used in the search use case
// Add a sequence of instructions that enable searching for a match instead of checking for it
void write_search_prefix()
{
const uint32_t first_inst = m_program.instructions.size();
@ -844,7 +841,7 @@ private:
uint32_t push_inst(CompiledRegex::Op op, uint32_t param = 0)
{
constexpr auto max_instructions = std::numeric_limits<uint16_t>::max();
uint32_t res = m_program.instructions.size();
const uint32_t res = m_program.instructions.size();
if (res > max_instructions)
throw regex_error(format("regex compiled to more than {} instructions", max_instructions));
m_program.instructions.push_back({ op, false, 0, param });
@ -854,7 +851,7 @@ private:
template<MatchDirection direction>
uint32_t push_lookaround(ParsedRegex::NodeIndex index, bool ignore_case)
{
uint32_t res = m_program.lookarounds.size();
const uint32_t res = m_program.lookarounds.size();
auto write_matcher = [this, ignore_case](ParsedRegex::NodeIndex child) {
auto& character = get_node(child);
if (character.op == ParsedRegex::Literal)
@ -877,9 +874,9 @@ private:
return res;
}
// Fills accepted and rejected according to which chars can start the given node,
// returns true if the node did not consume the char, hence a following node in
// sequence would be still relevant for the parent node start chars computation.
// Mutate start_desc with informations on which Codepoint could start a match.
// Returns true if the node can not consume the char, in which case the next node
// would still be relevant for the parent node start chars computation.
template<MatchDirection direction>
bool compute_start_desc(ParsedRegex::NodeIndex index,
CompiledRegex::StartDesc& start_desc) const

2
src/regex_impl.hh
View File

@ -294,6 +294,8 @@ private:
while (true)
{
auto& inst = *thread.inst++;
// if this instruction was already executed for this step in another thread,
// then this thread is redundant and can be dropped
if (inst.last_step == state.step)
return StepResult::Failed;
inst.last_step = state.step;