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#pragma once
#include <list>
#include <map>
#include <unordered_map>
#include "types.hh"
#include "chunked-vector.hh"
namespace nix {
/* Symbol table used by the parser and evaluator to represent and look
up identifiers and attributes efficiently. SymbolTable::create()
converts a string into a symbol. Symbols have the property that
they can be compared efficiently (using a pointer equality test),
because the symbol table stores only one copy of each string. */
class Symbol
{
friend class SymbolTable;
private:
std::string s;
public:
Symbol(std::string_view s) : s(s) { }
// FIXME: remove
bool operator == (std::string_view s2) const
{
return s == s2;
}
operator const std::string & () const
{
return s;
}
operator const std::string_view () const
{
return s;
}
friend std::ostream & operator << (std::ostream & str, const Symbol & sym);
};
class SymbolIdx
{
friend class SymbolTable;
private:
uint32_t id;
explicit SymbolIdx(uint32_t id): id(id) {}
public:
SymbolIdx() : id(0) {}
explicit operator bool() const { return id > 0; }
bool operator<(const SymbolIdx other) const { return id < other.id; }
bool operator==(const SymbolIdx other) const { return id == other.id; }
bool operator!=(const SymbolIdx other) const { return id != other.id; }
};
class SymbolTable
{
private:
std::unordered_map<std::string_view, std::pair<const Symbol *, uint32_t>> symbols;
ChunkedVector<Symbol, 8192> store{16};
public:
SymbolIdx create(std::string_view s)
{
// Most symbols are looked up more than once, so we trade off insertion performance
// for lookup performance.
// TODO: could probably be done more efficiently with transparent Hash and Equals
// on the original implementation using unordered_set
auto it = symbols.find(s);
if (it != symbols.end()) return SymbolIdx(it->second.second + 1);
const auto & [rawSym, idx] = store.add(s);
symbols.emplace(rawSym, std::make_pair(&rawSym, idx));
return SymbolIdx(idx + 1);
}
const Symbol & operator[](SymbolIdx s) const
{
if (s.id == 0 || s.id > store.size())
abort();
return store[s.id - 1];
}
size_t size() const
{
return store.size();
}
size_t totalSize() const;
template<typename T>
void dump(T callback) const
{
store.forEach(callback);
}
};
}
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