ClickHouse/src/Interpreters/InDepthNodeVisitor.h
2020-04-14 21:50:00 +03:00

83 lines
2.2 KiB
C++

#pragma once
#include <typeinfo>
#include <vector>
#include <Common/typeid_cast.h>
#include <Parsers/DumpASTNode.h>
namespace DB
{
/// Visits AST tree in depth, call functions for nodes according to Matcher type data.
/// You need to define Data, visit() and needChildVisit() in Matcher class.
template <typename Matcher, bool _top_to_bottom, typename T = ASTPtr>
class InDepthNodeVisitor
{
public:
using Data = typename Matcher::Data;
InDepthNodeVisitor(Data & data_, std::ostream * ostr_ = nullptr)
: data(data_),
visit_depth(0),
ostr(ostr_)
{}
void visit(T & ast)
{
DumpASTNode dump(*ast, ostr, visit_depth, typeid(Matcher).name());
if constexpr (!_top_to_bottom)
visitChildren(ast);
Matcher::visit(ast, data);
if constexpr (_top_to_bottom)
visitChildren(ast);
}
private:
Data & data;
size_t visit_depth;
std::ostream * ostr;
void visitChildren(T & ast)
{
for (auto & child : ast->children)
if (Matcher::needChildVisit(ast, child))
visit(child);
}
};
template <typename Matcher, bool top_to_bottom>
using ConstInDepthNodeVisitor = InDepthNodeVisitor<Matcher, top_to_bottom, const ASTPtr>;
struct NeedChild
{
using Condition = bool (*)(const ASTPtr & node, const ASTPtr & child);
static bool all(const ASTPtr &, const ASTPtr &) { return true; }
static bool none(const ASTPtr &, const ASTPtr &) { return false; }
};
/// Simple matcher for one node type. Use need_child function for complex traversal logic.
template <typename Data_, NeedChild::Condition need_child = NeedChild::all, typename T = ASTPtr>
class OneTypeMatcher
{
public:
using Data = Data_;
using TypeToVisit = typename Data::TypeToVisit;
static bool needChildVisit(const ASTPtr & node, const ASTPtr & child) { return need_child(node, child); }
static void visit(T & ast, Data & data)
{
if (auto * t = typeid_cast<TypeToVisit *>(ast.get()))
data.visit(*t, ast);
}
};
template <typename Data, NeedChild::Condition need_child = NeedChild::all>
using ConstOneTypeMatcher = OneTypeMatcher<Data, need_child, const ASTPtr>;
}