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// This file implements the underlying structure of Nix attribute sets.
#pragma once
#include <cstddef>
#include <absl/container/btree_map.h>
#include <gc/gc_allocator.h>
#include "libexpr/nixexpr.hh"
#include "libexpr/symbol-table.hh"
#include "libutil/types.hh"
namespace nix { // TODO(tazjin): ::expr
class EvalState;
struct Value;
/* Map one attribute name to its value. */
struct Attr {
Symbol name;
Value* value; // TODO(tazjin): Who owns this?
Pos* pos; // TODO(tazjin): Who owns this?
Attr(Symbol name, Value* value, Pos* pos = &noPos)
: name(name), value(value), pos(pos){};
};
// Convenience alias for the backing map, with the garbage-collecting
// allocator explicitly specified.
using AttributeMap = absl::btree_map<Symbol, Attr, std::less<Symbol>,
gc_allocator<std::pair<Symbol, Attr>>>;
using AttributeVector =
std::vector<std::pair<Symbol, Attr>, gc_allocator<std::pair<Symbol, Attr>>>;
class BindingsIterator : public std::iterator<std::forward_iterator_tag,
std::pair<const Symbol, Attr>> {
friend class Bindings;
friend class BTreeBindings;
friend class VectorBindings;
public:
BindingsIterator() : _iterator(){};
BindingsIterator& operator++();
BindingsIterator operator++(int);
bool operator==(const BindingsIterator& other) const;
bool operator!=(const BindingsIterator& other) const;
reference operator*() const;
pointer operator->() const { return &operator*(); }
BindingsIterator& operator=(const BindingsIterator& other) {
_iterator = other._iterator;
return *this;
}
protected:
explicit BindingsIterator(AttributeMap::iterator&& iterator)
: _iterator(iterator){};
explicit BindingsIterator(AttributeVector::iterator&& iterator)
: _iterator(iterator){};
private:
std::variant<AttributeMap::iterator, AttributeVector::iterator> _iterator;
};
class Bindings {
public:
typedef BindingsIterator iterator;
// Allocate a new attribute set with a static capacity that is visible to the
// garbage collector.
static Bindings* NewGC(size_t capacity = 0);
// Return the number of contained elements.
virtual size_t size() = 0;
// Is this attribute set empty?
virtual bool empty() = 0;
// Insert, but do not replace, values in the attribute set.
virtual void push_back(const Attr& attr) = 0;
// Insert a value, or replace an existing one.
virtual void insert_or_assign(Attr& attr) = 0;
// Look up a specific element of the attribute set.
virtual iterator find(const Symbol& name) = 0;
// TODO
virtual iterator begin() = 0;
virtual iterator end() = 0;
// Merge values from other into this attribute set.
virtual void merge(Bindings& other) = 0;
// TODO: can callers just iterate?
[[deprecated]] virtual std::vector<const Attr*> lexicographicOrder() = 0;
// oh no
friend class EvalState;
};
} // namespace nix
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