1 files changed, 111 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..b1617c981f51
--- /dev/null
+++ b/third_party/nix/src/libexpr/attr-set.cc
@@ -0,0 +1,111 @@
+#include "libexpr/attr-set.hh"
+
+#include <new>
+
+#include <absl/container/btree_map.h>
+#include <glog/logging.h>
+
+#include "libexpr/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 << "'";
+  }
+}
+
+size_t Bindings::size() const { return attributes_.size(); }
+
+bool Bindings::empty() { return attributes_.empty(); }
+
+Bindings::iterator Bindings::find(const Symbol& name) {
+  return attributes_.find(name);
+}
+
+bool Bindings::Equal(const Bindings* other, EvalState& state) const {
+  if (this == other) {
+    return true;
+  }
+
+  if (this->attributes_.size() != other->attributes_.size()) {
+    return false;
+  }
+
+  Bindings::const_iterator i;
+  Bindings::const_iterator j;
+  for (i = this->cbegin(), j = other->cbegin(); i != this->cend(); ++i, ++j) {
+    if (i->second.name != j->second.name ||
+        !state.eqValues(*i->second.value, *j->second.value)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+Bindings::iterator Bindings::begin() { return attributes_.begin(); }
+Bindings::iterator Bindings::end() { return attributes_.end(); }
+
+Bindings::const_iterator Bindings::cbegin() const {
+  return attributes_.cbegin();
+}
+
+Bindings::const_iterator Bindings::cend() const { return attributes_.cend(); }
+
+std::unique_ptr<Bindings> Bindings::New(size_t capacity) {
+  if (capacity == 0) {
+    // TODO(tazjin): A lot of 0-capacity Bindings are allocated.
+    // It would be nice to optimize that.
+  }
+
+  return std::make_unique<Bindings>();
+}
+
+std::unique_ptr<Bindings> Bindings::Merge(const Bindings& lhs,
+                                          const Bindings& rhs) {
+  auto bindings = New(lhs.size() + rhs.size());
+
+  // Values are merged by inserting the entire iterator range of both
+  // input sets. The right-hand set (the values of which take
+  // precedence) is inserted *first* because the range insertion
+  // method does not override values.
+  bindings->attributes_.insert(rhs.attributes_.cbegin(),
+                               rhs.attributes_.cend());
+  bindings->attributes_.insert(lhs.attributes_.cbegin(),
+                               lhs.attributes_.cend());
+
+  return bindings;
+}
+
+void EvalState::mkAttrs(Value& v, size_t capacity) {
+  clearValue(v);
+  v.type = tAttrs;
+  v.attrs = Bindings::New(capacity);
+  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