// This file implements the underlying structure of Nix attribute sets.
#pragma once
#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 : public gc {
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>,
traceable_allocator<std::pair<const Symbol, Attr>>>;
class Bindings : public gc {
public:
typedef AttributeMap::iterator iterator;
// Allocate a new attribute set that is visible to the garbage
// collector.
static Bindings* NewGC(size_t capacity = 0);
// Create a new attribute set by merging two others. This is used to
// implement the `//` operator in Nix.
static Bindings* Merge(const Bindings& lhs, const Bindings& rhs);
// Return the number of contained elements.
size_t size() const;
// Is this attribute set empty?
bool empty();
// Insert, but do not replace, values in the attribute set.
void push_back(const Attr& attr);
// Look up a specific element of the attribute set.
iterator find(const Symbol& name);
iterator begin();
iterator end();
// Returns the elements of the attribute set as a vector, sorted
// lexicographically by keys.
//
// This is used primarily for builtins that have guaranteed
// ordering, such as `attrNames` or `attrValues`.
std::vector<const Attr*> SortedByKeys();
// oh no
friend class EvalState;
private:
AttributeMap attributes_;
};
} // namespace nix
