1 files changed, 87 insertions, 0 deletions
diff --git a/third_party/nix/src/libexpr/attr-set.cc b/third_party/nix/src/libexpr/attr-set.cc
new file mode 100644
index 000000000000..6310cc66b726
--- /dev/null
+++ b/third_party/nix/src/libexpr/attr-set.cc
@@ -0,0 +1,87 @@
+#include "attr-set.hh"
+
+#include <new>
+
+#include <absl/container/btree_map.h>
+#include <gc/gc_cpp.h>
+#include <glog/logging.h>
+
+#include "eval-inline.hh"
+
+namespace nix {
+
+// This function inherits its name from previous implementations, in
+// which Bindings was backed by an array of elements which was scanned
+// linearly.
+//
+// In that setup, inserting duplicate elements would always yield the
+// first element (until the next sort, which wasn't stable, after
+// which things are more or less undefined).
+//
+// This behaviour is mimicked by using .insert(), which will *not*
+// override existing values.
+void Bindings::push_back(const Attr& attr) {
+  auto [_, inserted] = attributes_.insert({attr.name, attr});
+
+  if (!inserted) {
+    DLOG(WARNING) << "attempted to insert duplicate attribute for key '"
+                  << attr.name << "'";
+  }
+}
+
+// Insert or assign (i.e. replace) a value in the attribute set.
+void Bindings::insert_or_assign(const Attr& attr) {
+  attributes_.insert_or_assign(attr.name, attr);
+}
+
+size_t Bindings::size() { return attributes_.size(); }
+
+size_t Bindings::capacity() { return 0; }
+
+bool Bindings::empty() { return attributes_.empty(); }
+
+std::vector<const Attr*> Bindings::lexicographicOrder() {
+  std::vector<const Attr*> res;
+  res.reserve(attributes_.size());
+
+  for (const auto& [key, value] : attributes_) {
+    res.emplace_back(&value);
+  }
+
+  return res;
+}
+
+Bindings::iterator Bindings::find(const Symbol& name) {
+  return attributes_.find(name);
+}
+
+Bindings::iterator Bindings::begin() { return attributes_.begin(); }
+
+Bindings::iterator Bindings::end() { return attributes_.end(); }
+
+void Bindings::merge(const Bindings& other) {
+  for (auto& [key, value] : other.attributes_) {
+    this->attributes_[key] = value;
+  }
+}
+
+Bindings* Bindings::NewGC() { return new (GC) Bindings; }
+
+void EvalState::mkAttrs(Value& v, size_t capacity) {
+  clearValue(v);
+  v.type = tAttrs;
+  v.attrs = Bindings::NewGC();
+  nrAttrsets++;
+  nrAttrsInAttrsets += capacity;
+}
+
+/* Create a new attribute named 'name' on an existing attribute set stored
+   in 'vAttrs' and return the newly allocated Value which is associated with
+   this attribute. */
+Value* EvalState::allocAttr(Value& vAttrs, const Symbol& name) {
+  Value* v = allocValue();
+  vAttrs.attrs->push_back(Attr(name, v));
+  return v;
+}
+
+}  // namespace nix