3 files changed, 39 insertions, 21 deletions
diff --git a/third_party/nix/src/libstore/references.cc b/third_party/nix/src/libstore/references.cc
index 879f126f63ee..b70d282e8df8 100644
--- a/third_party/nix/src/libstore/references.cc
+++ b/third_party/nix/src/libstore/references.cc
@@ -13,21 +13,38 @@ namespace nix {
 
 static unsigned int refLength = 32; /* characters */
 
-static void search(const char* s, size_t len, StringSet& hashes,
+static void search(const unsigned char* s, size_t len, StringSet& hashes,
                    StringSet& seen) {
+  static bool initialised = false;
+  static bool isBase32[256];
+  if (!initialised) {
+    for (bool& i : isBase32) {
+      i = false;
+    }
+    for (char base32Char : base32Chars) {
+      isBase32[static_cast<unsigned char>(base32Char)] = true;
+    }
+    initialised = true;
+  }
+
   for (size_t i = 0; i + refLength <= len;) {
-    absl::string_view ref(s + i, refLength);
-    bool match = Hash::IsValidBase32(ref);
+    int j = 0;
+    bool match = true;
+    for (j = refLength - 1; j >= 0; --j) {
+      if (!isBase32[s[i + j]]) {
+        i += j + 1;
+        match = false;
+        break;
+      }
+    }
     if (!match) {
       continue;
     }
-    // TODO(kanepyork): convert StringSet to flat_hash_set, delay owned string
-    // conversion into the 'if'
-    std::string sref(ref);
-    if (hashes.find(sref) != hashes.end()) {
+    std::string ref(reinterpret_cast<const char*>(s) + i, refLength);
+    if (hashes.find(ref) != hashes.end()) {
       DLOG(INFO) << "found reference to '" << ref << "' at offset " << i;
-      seen.insert(sref);
-      hashes.erase(sref);
+      seen.insert(ref);
+      hashes.erase(ref);
     }
     ++i;
   }
@@ -48,21 +65,22 @@ struct RefScanSink : Sink {
 void RefScanSink::operator()(const unsigned char* data, size_t len) {
   hashSink(data, len);
 
-  const char* data_ = reinterpret_cast<const char*>(data);
-
   /* It's possible that a reference spans the previous and current
      fragment, so search in the concatenation of the tail of the
      previous fragment and the start of the current fragment. */
-  std::string s = tail + std::string(data_, len > refLength ? refLength : len);
-  search(s.data(), s.size(), hashes, seen);
+  std::string s = tail + std::string(reinterpret_cast<const char*>(data),
+                                     len > refLength ? refLength : len);
+  search(reinterpret_cast<const unsigned char*>(s.data()), s.size(), hashes,
+         seen);
 
-  search(data_, len, hashes, seen);
+  search(data, len, hashes, seen);
 
   size_t tailLen = len <= refLength ? len : refLength;
-  tail = std::string(tail, tail.size() < refLength - tailLen
-                               ? 0
-                               : tail.size() - (refLength - tailLen)) +
-         std::string(data_ + len - tailLen, tailLen);
+  tail =
+      std::string(tail, tail.size() < refLength - tailLen
+                            ? 0
+                            : tail.size() - (refLength - tailLen)) +
+      std::string(reinterpret_cast<const char*>(data) + len - tailLen, tailLen);
 }
 
 PathSet scanForReferences(const std::string& path, const PathSet& refs,
diff --git a/third_party/nix/src/libutil/hash.cc b/third_party/nix/src/libutil/hash.cc
index ac151201fd34..97cc137b11a7 100644
--- a/third_party/nix/src/libutil/hash.cc
+++ b/third_party/nix/src/libutil/hash.cc
@@ -104,9 +104,6 @@ bool Hash::IsValidBase16(absl::string_view s) {
   return true;
 }
 
-// omitted: E O U T
-constexpr char base32Chars[] = "0123456789abcdfghijklmnpqrsvwxyz";
-
 constexpr signed char kUnBase32[] = {
     -1, -1, -1, -1, -1, -1, -1, -1, /* unprintables */
     -1, -1, -1, -1, -1, -1, -1, -1, /* unprintables */
diff --git a/third_party/nix/src/libutil/hash.hh b/third_party/nix/src/libutil/hash.hh
index 56845e715491..bc32f9146373 100644
--- a/third_party/nix/src/libutil/hash.hh
+++ b/third_party/nix/src/libutil/hash.hh
@@ -21,6 +21,9 @@ const int sha1HashSize = 20;
 const int sha256HashSize = 32;
 const int sha512HashSize = 64;
 
+// omitted: E O U T
+constexpr char base32Chars[] = "0123456789abcdfghijklmnpqrsvwxyz";
+
 enum Base : int { Base64, Base32, Base16, SRI };
 
 struct Hash {