xenia/kakoune
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Regex: Add initial, exploratory work on a custom regex engine

Browse Source
This commit is contained in:
Maxime Coste 2017-09-17 17:50:53 +09:00
parent 797a0cb062
commit 8c9976ea72
2 changed files with 395 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

391
src/regex_impl.cc Normal file
View File

@ -0,0 +1,391 @@
#include "regex_impl.hh"
#include "vector.hh"
#include "unit_tests.hh"
#include "string.hh"
#include "exception.hh"
namespace Kakoune
{
struct RegexProgram
{
enum Op : char
{
Match,
Literal,
AnyChar,
Jump,
Split,
LineStart,
LineEnd,
};
using Offset = size_t;
using Instructions = Vector<char>;
Instructions instructions;
};
namespace RegexCompiler
{
enum class Quantifier
{
One,
Optional,
RepeatZeroOrMore,
RepeatOneOrMore
};
enum class Op
{
Literal,
AnyChar,
Sequence,
Alternation,
LineStart,
LineEnd,
};
struct AstNode
{
Op op;
char value;
Quantifier quantifier;
Vector<std::unique_ptr<AstNode>> children;
};
using AstNodePtr = std::unique_ptr<AstNode>;
AstNodePtr make_ast_node(Op op, char value = 0,
Quantifier quantifier = Quantifier::One)
{
return AstNodePtr{new AstNode{op, value, quantifier, {}}};
}
template<typename Iterator>
struct Parser
{
static AstNodePtr parse(Iterator pos, Iterator end)
{
return disjunction(pos, end);
}
private:
static AstNodePtr disjunction(Iterator& pos, Iterator end)
{
AstNodePtr node = alternative(pos, end);
if (pos == end or *pos != '|')
return node;
AstNodePtr res = make_ast_node(Op::Alternation);
res->children.push_back(std::move(node));
while (pos != end and *pos == '|')
res->children.push_back(disjunction(++pos, end));
return res;
}
static AstNodePtr alternative(Iterator& pos, Iterator end)
{
AstNodePtr res = make_ast_node(Op::Sequence);
while (auto node = term(pos, end))
res->children.push_back(std::move(node));
return res;
}
static AstNodePtr term(Iterator& pos, Iterator end)
{
if (auto node = assertion(pos, end))
return node;
if (auto node = atom(pos, end))
{
node->quantifier = quantifier(pos, end);
return node;
}
return nullptr;
}
static AstNodePtr assertion(Iterator& pos, Iterator end)
{
switch (*pos)
{
case '^': ++pos; return make_ast_node(Op::LineStart);
case '$': ++pos; return make_ast_node(Op::LineEnd);
/* TODO: \`, \', \b, \B, look ahead, look behind */
}
return nullptr;
}
static AstNodePtr atom(Iterator& pos, Iterator end)
{
const auto c = *pos;
switch (c)
{
case '.': ++pos; return make_ast_node(Op::AnyChar);
case '(':
{
++pos;
auto content = disjunction(pos, end);
if (pos == end or *pos != ')')
throw runtime_error{"Unclosed parenthesis"};
++pos;
return content;
}
default:
if (contains("^$.*+?()[]{}|", c))
return nullptr;
++pos;
return make_ast_node(Op::Literal, c);
}
}
static Quantifier quantifier(Iterator& pos, Iterator end)
{
switch (*pos)
{
case '*': ++pos; return Quantifier::RepeatZeroOrMore;
case '+': ++pos; return Quantifier::RepeatOneOrMore;
case '?': ++pos; return Quantifier::Optional;
default: return Quantifier::One;
}
}
};
RegexProgram::Offset compile_node(RegexProgram& program, const AstNodePtr& node)
{
auto& insts = program.instructions;
RegexProgram::Offset pos = insts.size();
auto allow_none = [](Quantifier quantifier) {
return quantifier == Quantifier::Optional or
quantifier == Quantifier::RepeatZeroOrMore;
};
auto is_repeat = [](Quantifier quantifier) {
return quantifier == Quantifier::RepeatZeroOrMore or
quantifier == Quantifier::RepeatOneOrMore;
};
auto alloc_offsets = [](RegexProgram::Instructions& instructions, int count) {
auto pos = instructions.size();
instructions.resize(instructions.size() + count * sizeof(RegexProgram::Offset));
return pos;
};
auto get_offset = [](RegexProgram::Instructions& instructions, RegexProgram::Offset base, int index = 0) {
return reinterpret_cast<RegexProgram::Offset*>(&instructions[base]) + index;
};
RegexProgram::Offset optional_offset = -1;
if (allow_none(node->quantifier))
{
insts.push_back(RegexProgram::Split);
insts.push_back(2);
auto offsets = alloc_offsets(insts, 2);
*get_offset(insts, offsets) = insts.size();
optional_offset = offsets;
}
Vector<RegexProgram::Offset> goto_end_offsets;
auto content_pos = insts.size();
switch (node->op)
{
case Op::Literal:
insts.push_back(RegexProgram::Literal);
insts.push_back(node->value);
break;
case Op::AnyChar:
insts.push_back(RegexProgram::AnyChar);
break;
case Op::Sequence:
for (auto& child : node->children)
compile_node(program, child);
break;
case Op::Alternation:
{
const auto count = node->children.size();
if (count > 255)
throw runtime_error{"More than 255 elements in an alternation is not supported"};
insts.push_back(RegexProgram::Split);
insts.push_back(count);
auto offsets = alloc_offsets(insts, count);
auto& children = node->children;
for (int i = 0; i < children.size(); ++i)
{
auto child_pos = compile_node(program, children[i]);
*get_offset(insts, offsets, i) = child_pos;
// Jump to end after executing that children
insts.push_back(RegexProgram::Jump);
goto_end_offsets.push_back(alloc_offsets(insts, 1));
}
break;
}
case Op::LineStart:
insts.push_back(RegexProgram::LineStart);
break;
case Op::LineEnd:
insts.push_back(RegexProgram::LineEnd);
break;
}
for (auto& offset : goto_end_offsets)
*get_offset(insts, offset) = insts.size();
if (is_repeat(node->quantifier))
{
insts.push_back(RegexProgram::Split);
insts.push_back(2);
auto offsets = alloc_offsets(insts, 2);
*get_offset(insts, offsets, 0) = content_pos;
*get_offset(insts, offsets, 1) = insts.size();
}
if (optional_offset != -1)
*get_offset(insts, optional_offset, 1) = insts.size();
return pos;
}
RegexProgram compile(const AstNodePtr& node)
{
RegexProgram res;
compile_node(res, node);
res.instructions.push_back(RegexProgram::Match);
return res;
}
}
void dump_program(const RegexProgram& program)
{
auto& insts = program.instructions;
for (size_t pos = 0; pos < insts.size(); )
{
printf("%4zd ", pos);
switch ((RegexProgram::Op)insts[pos++])
{
case RegexProgram::Literal:
printf("literal %c\n", insts[pos++]);
break;
case RegexProgram::AnyChar:
printf("any char\n");
break;
case RegexProgram::Jump:
printf("jump %zd\n", *reinterpret_cast<const RegexProgram::Offset*>(&insts[pos]));
pos += sizeof(RegexProgram::Offset);
break;
case RegexProgram::Split:
{
int count = insts[pos++];
printf("split [");
for (int i = 0; i < count; ++i)
printf("%zd%s", reinterpret_cast<const RegexProgram::Offset*>(&insts[pos])[i],
(i == count - 1) ? "]\n" : ", ");
pos += count * sizeof(RegexProgram::Offset);
break;
}
case RegexProgram::LineStart:
printf("line start\n");
break;
case RegexProgram::LineEnd:
printf("line end\n");
break;
case RegexProgram::Match:
printf("match\n");
}
}
}
bool regex_match(const RegexProgram& program, StringView data)
{
const char* start = program.instructions.data();
Vector<const char*> threads = { start };
struct StepResult
{
enum Result { Consumed, Stepped, Matched, Failed } result;
const char* next = nullptr;
};
auto step_thread = [&](const char* inst, char c) -> StepResult
{
const RegexProgram::Op op = (RegexProgram::Op)*inst++;
switch (op)
{
case RegexProgram::Literal:
if (*inst++ == c)
return { StepResult::Consumed, inst };
return { StepResult::Failed };
case RegexProgram::AnyChar:
return { StepResult::Consumed, inst };
case RegexProgram::Jump:
return { StepResult::Stepped, start + *reinterpret_cast<const RegexProgram::Offset*>(inst) };
case RegexProgram::Split:
{
const int count = *inst++;
auto* offsets = reinterpret_cast<const RegexProgram::Offset*>(inst);
for (int o = 1; o < count; ++o)
threads.push_back(start + offsets[o]);
return { StepResult::Stepped, start + offsets[0] };
}
case RegexProgram::LineStart:
// TODO
return { StepResult::Stepped, inst };
case RegexProgram::LineEnd:
// TODO
return { StepResult::Stepped, inst };
case RegexProgram::Match:
return { StepResult::Matched };
}
return { StepResult::Failed };
};
for (auto c : data)
{
for (int i = 0; i < threads.size(); ++i)
{
while (threads[i])
{
auto res = step_thread(threads[i], c);
threads[i] = res.next;
if (res.result == StepResult::Consumed or
res.result == StepResult::Failed)
break;
else if (res.result == StepResult::Matched)
return true;
}
}
threads.erase(std::remove(threads.begin(), threads.end(), nullptr), threads.end());
if (threads.empty())
break;
}
// Step remaining threads to see if they match without consuming anything else
for (int i = 0; i < threads.size(); ++i)
{
while (threads[i])
{
auto res = step_thread(threads[i], 0);
threads[i] = res.next;
if (res.result == StepResult::Consumed)
break;
else if (res.result == StepResult::Matched)
return true;
}
}
return false;
}
auto test_regex = UnitTest{[]{
StringView re = "^(foo|qux)+(bar)?baz$";
auto node = RegexCompiler::Parser<const char*>::parse(re.begin(), re.end());
kak_assert(node);
auto program = RegexCompiler::compile(node);
dump_program(program);
kak_assert(regex_match(program, "fooquxbarbaz"));
kak_assert(not regex_match(program, "quxbar"));
kak_assert(not regex_match(program, "blahblah"));
kak_assert(regex_match(program, "foobaz"));
}};
}

4
src/regex_impl.hh Normal file
View File

@ -0,0 +1,4 @@
#ifndef regex_impl_hh_INCLUDED
#define regex_impl_hh_INCLUDED
#endif // regex_impl_hh_INCLUDED