6 files changed, 98 insertions, 5 deletions
diff --git a/third_party/nix/src/libstore/store-api.cc b/third_party/nix/src/libstore/store-api.cc
index a6863cc04b52..ae403b0be65f 100644
--- a/third_party/nix/src/libstore/store-api.cc
+++ b/third_party/nix/src/libstore/store-api.cc
@@ -323,9 +323,8 @@ Path Store::makeStorePath(const std::string& type, const Hash& hash,
 
   checkStoreName(name);
 
-  return storeDir + "/" +
-         compressHash(hashString(htSHA256, s), 20).to_string(Base32, false) +
-         "-" + name;
+  return absl::StrCat(storeDir, "/", hashString(htSHA256, s).ToStorePathHash(),
+                      "-", name);
 }
 
 Path Store::makeOutputPath(const std::string& id, const Hash& hash,
diff --git a/third_party/nix/src/libutil/hash.cc b/third_party/nix/src/libutil/hash.cc
index 426096e73af8..9d14ad9dfe14 100644
--- a/third_party/nix/src/libutil/hash.cc
+++ b/third_party/nix/src/libutil/hash.cc
@@ -158,6 +158,10 @@ bool Hash::IsValidBase32(absl::string_view s) {
   return true;
 }
 
+std::string Hash::ToStorePathHash() const {
+  return compressHash(*this, kStorePathHashSize).to_string(Base32, false);
+}
+
 static std::string printHash32(const Hash& hash) {
   assert(hash.hashSize);
   size_t len = hash.base32Len();
diff --git a/third_party/nix/src/libutil/hash.hh b/third_party/nix/src/libutil/hash.hh
index 4d52702aee75..6fbeec5b47fb 100644
--- a/third_party/nix/src/libutil/hash.hh
+++ b/third_party/nix/src/libutil/hash.hh
@@ -8,6 +8,9 @@
 
 namespace nix {
 
+// Size of the hashes rendered in store paths, in bytes
+constexpr unsigned int kStorePathHashSize = 20;
+
 MakeError(BadHash, Error);
 
 // TODO(grfn): Replace this with the hash type enum from the daemon proto so we
@@ -90,6 +93,9 @@ struct Hash {
   /* Returns whether the passed string contains entirely valid base32
      characters. */
   static bool IsValidBase32(absl::string_view s);
+
+  // Convert this Hash to the format expected in store paths
+  [[nodiscard]] std::string ToStorePathHash() const;
 };
 
 /* Print a hash in base-16 if it's MD5, or base-32 otherwise. */
diff --git a/third_party/nix/src/nix/hash.cc b/third_party/nix/src/nix/hash.cc
index 24529c67ce8c..08ada7ccfb3a 100644
--- a/third_party/nix/src/nix/hash.cc
+++ b/third_party/nix/src/nix/hash.cc
@@ -36,8 +36,8 @@ struct CmdHash final : Command {
   void run() override {
     for (const auto& path : paths) {
       Hash h = mode == mFile ? hashFile(ht, path) : hashPath(ht, path).first;
-      if (truncate && h.hashSize > 20) {
-        h = compressHash(h, 20);
+      if (truncate && h.hashSize > nix::kStorePathHashSize) {
+        h = compressHash(h, nix::kStorePathHashSize);
       }
       std::cout << format("%1%\n") % h.to_string(base, base == SRI);
     }
diff --git a/third_party/nix/src/tests/CMakeLists.txt b/third_party/nix/src/tests/CMakeLists.txt
index 929acc5ea671..cda8f5da8483 100644
--- a/third_party/nix/src/tests/CMakeLists.txt
+++ b/third_party/nix/src/tests/CMakeLists.txt
@@ -30,6 +30,16 @@ target_link_libraries(hash_test
 
 gtest_discover_tests(hash_test)
 
+add_executable(references_test references_test.cc)
+target_link_libraries(references_test
+  nixstore
+  rapidcheck
+  rapidcheck_gtest
+  GTest::gtest_main
+)
+
+gtest_discover_tests(references_test)
+
 add_executable(store_test store_tests.cc)
 target_link_libraries(store_test
   nixstore
diff --git a/third_party/nix/src/tests/references_test.cc b/third_party/nix/src/tests/references_test.cc
new file mode 100644
index 000000000000..8dcb3ed37a8b
--- /dev/null
+++ b/third_party/nix/src/tests/references_test.cc
@@ -0,0 +1,74 @@
+#include "libstore/references.hh"
+
+#include <cstdio>
+#include <fstream>
+#include <ostream>
+#include <unordered_set>
+
+#include <absl/strings/str_format.h>
+#include <gtest/gtest.h>
+#include <rapidcheck.h>
+#include <rapidcheck/gtest.h>
+
+#include "libutil/hash.hh"
+
+class ReferencesTest : public ::testing::Test {};
+
+namespace nix {
+
+TEST(ReferencesTest, ScanForOneReferenceNotFound) {
+  char path[] = "store_XXXXXXX";
+  auto f = mkstemp(path);
+
+  auto hash = hashString(htSHA256, "foo");
+  auto ref = absl::StrFormat("/nix/store/%s-foo", hash.ToStorePathHash());
+
+  HashResult hr;
+  auto result = scanForReferences(path, {ref}, hr);
+
+  ASSERT_EQ(result.find(ref), result.end());
+
+  EXPECT_EQ(close(f), 0);
+}
+
+TEST(ReferencesTest, ScanForOneReferenceFound) {
+  char path[] = "store_XXXXXXX";
+  auto f = mkstemp(path);
+
+  auto hash = hashString(htSHA256, "foo");
+  auto ref = absl::StrFormat("/nix/store/%s-foo", hash.ToStorePathHash());
+
+  EXPECT_GT(write(f, ref.c_str(), sizeof(char) * ref.size()), 0);
+
+  HashResult hr;
+  auto result = scanForReferences(path, {ref}, hr);
+
+  ASSERT_NE(result.find(ref), result.end());
+
+  ASSERT_EQ(close(f), 0);
+}
+
+RC_GTEST_PROP(ReferencesTest, ScanForReferences,
+              (std::unordered_set<std::string> strs)) {
+  char path[] = "store_XXXXXXX";
+  auto f = mkstemp(path);
+
+  PathSet refs;
+  for (const auto& s : strs) {
+    auto hash = hashString(htSHA256, s);
+    auto ref = absl::StrFormat("/nix/store/%s-foo", hash.ToStorePathHash());
+    refs.insert(ref);
+    RC_ASSERT(write(f, ref.c_str(), sizeof(char) * ref.size()) > 0);
+  }
+
+  HashResult hr;
+  auto result = scanForReferences(path, refs, hr);
+
+  for (const auto& ref : refs) {
+    RC_ASSERT(result.find(ref) != result.end());
+  }
+
+  RC_ASSERT(close(f) == 0);
+}
+
+}  // namespace nix