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Regex: compute start chars from matchers, do not compute it from lookarounds

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Computing potential start characters from lookarounds is more complex
than expected, and not worth the complexity.
This commit is contained in:
Maxime Coste 2017-10-14 16:50:49 +08:00
parent 621b0d3ab8
commit 6e65589a34
1 changed files with 11 additions and 44 deletions
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55
src/regex_impl.cc
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@ -9,6 +9,8 @@
#include "string_utils.hh"
#include "vector.hh"
#include <cstring>
namespace Kakoune
{
@ -763,8 +765,7 @@ private:
// 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.
bool compute_start_chars(const ParsedRegex::AstNodePtr& node,
bool (&accepted)[start_chars_count],
bool (&rejected)[start_chars_count]) const
bool (&accepted)[start_chars_count]) const
{
switch (node->op)
{
@ -785,14 +786,15 @@ private:
b = true;
return node->quantifier.allows_none();
case ParsedRegex::Matcher:
for (auto& b : accepted) // treat matcher as everything can match for now
b = true;
for (Codepoint c = 0; c < start_chars_count; ++c)
if (m_program.matchers[node->value](c))
accepted[c] = true;
return node->quantifier.allows_none();
case ParsedRegex::Sequence:
{
bool consumed = false;
auto consumes = [&, this](auto& child) {
return not this->compute_start_chars(child, accepted, rejected);
return not this->compute_start_chars(child, accepted);
};
if (m_forward)
consumed = contains_that(node->children, consumes);
@ -806,7 +808,7 @@ private:
bool all_consumed = not node->quantifier.allows_none();
for (auto& child : node->children)
{
if (compute_start_chars(child, accepted, rejected))
if (compute_start_chars(child, accepted))
all_consumed = false;
}
return not all_consumed;
@ -818,42 +820,10 @@ private:
case ParsedRegex::SubjectBegin:
case ParsedRegex::SubjectEnd:
case ParsedRegex::ResetStart:
return true;
case ParsedRegex::LookAhead:
case ParsedRegex::LookBehind:
if (not node->children.empty() and
m_forward == (node->op == ParsedRegex::LookAhead))
{
auto& child = m_forward ? node->children.front() : node->children.back();
if (child->op == ParsedRegex::Literal and child->value < start_chars_count)
{
// Every other char is rejected
for (Codepoint c = 0; c < start_chars_count; ++c)
{
if ((not child->ignore_case and c != child->value) or
(c != to_lower(child->value) and c != to_upper(child->value)))
rejected[c] = true;
}
}
}
return true;
case ParsedRegex::NegativeLookAhead:
case ParsedRegex::NegativeLookBehind:
if (node->children.size() == 1 and
m_forward == (node->op == ParsedRegex::NegativeLookAhead))
{
auto& child = node->children.front();
if (child->op == ParsedRegex::Literal and child->value < start_chars_count)
{
if (child->ignore_case)
{
rejected[to_lower(child->value)] = true;
rejected[to_upper(child->value)] = true;
}
else
rejected[child->value] = true;
}
}
return true;
}
return false;
@ -863,17 +833,14 @@ private:
std::unique_ptr<CompiledRegex::StartChars> compute_start_chars() const
{
bool accepted[start_chars_count] = {};
bool rejected[start_chars_count] = {};
if (compute_start_chars(m_parsed_regex.ast, accepted, rejected))
if (compute_start_chars(m_parsed_regex.ast, accepted))
return nullptr;
if (not contains(accepted, false) and not contains(rejected, true))
if (not contains(accepted, false))
return nullptr;
auto start_chars = std::make_unique<CompiledRegex::StartChars>();
for (int i = 0; i < start_chars_count; ++i)
start_chars->map[i] = accepted[i] and not rejected[i];
memcpy(start_chars->map, accepted, sizeof(bool[start_chars_count]));
return start_chars;
}