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feat(3p/nix): Add vector-backed impl for Bindings

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Add an alternative impl of the now-abstract Bindings base class that is
backed by a std::vector, somewhat similar but stylistically a little
superior to the array-backed implementation in upstream nix. The
underlying iterator type in BindingsIterator is now backed by a
std::variant that we std::visit an overload over in order to implement
the various bits of the iterator interface.

Paired-With: Luke Granger-Brown <git@lukegb.com>
Paired-With: Vincent Ambo <mail@tazj.in>
Paired-With: Perry Lorier <isomer@tvl.fyi>
Change-Id: I7fbd1f4d5c449e2f9b82102a701b0bacd5e80672
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1123
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
This commit is contained in:
Griffin Smith 2020-07-12 16:51:00 -04:00 • committed by glittershark
parent 98148e6711
commit d5505fcff9
2 changed files with 150 additions and 16 deletions
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20
third_party/nix/src/libexpr/attr-set.hh vendored
View file

@ -26,14 +26,17 @@ struct Attr {
// 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<const Symbol, Attr>>>;
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(){};
@ -43,6 +46,7 @@ class BindingsIterator : public std::iterator<std::forward_iterator_tag,
bool operator!=(const BindingsIterator& other) const;
reference operator*() const;
pointer operator->() const { return &operator*(); }
BindingsIterator& operator=(const BindingsIterator& other) {
_iterator = other._iterator;
return *this;
@ -52,8 +56,11 @@ class BindingsIterator : public std::iterator<std::forward_iterator_tag,
explicit BindingsIterator(AttributeMap::iterator&& iterator)
: _iterator(iterator){};
explicit BindingsIterator(AttributeVector::iterator&& iterator)
: _iterator(iterator){};
private:
AttributeMap::iterator _iterator;
std::variant<AttributeMap::iterator, AttributeVector::iterator> _iterator;
};
class Bindings {
@ -78,7 +85,7 @@ class Bindings {
virtual void push_back(const Attr& attr) = 0;
// Insert a value, or replace an existing one.
virtual void insert_or_assign(const Attr& attr) = 0;
virtual void insert_or_assign(Attr& attr) = 0;
// Look up a specific element of the attribute set.
virtual iterator find(const Symbol& name) = 0;
@ -95,9 +102,6 @@ class Bindings {
// oh no
friend class EvalState;
private:
AttributeMap attributes_;
};
} // namespace nix