1 files changed, 124 insertions, 23 deletions

diff --git a/src/libstore/content-address.hh b/src/libstore/content-address.hh
index 634a51c38..d74d1ff4b 100644
--- a/src/libstore/content-address.hh
+++ b/src/libstore/content-address.hh
@@ -2,11 +2,30 @@
 
 #include <variant>
 #include "hash.hh"
+#include "path.hh"
+#include "comparator.hh"
 
 namespace nix {
 
+/*
+ * Content addressing method
+ */
+
+/* We only have one way to hash text with references, so this is a single-value
+   type, mainly useful with std::variant.
+*/
+
+/**
+ * The single way we can serialize "text" file system objects.
+ *
+ * Somewhat obscure, used by \ref Derivation derivations and
+ * `builtins.toFile` currently.
+ */
+struct TextHashMethod : std::monostate { };
+
 /**
- * An enumeration of the ways we can serialize file system objects.
+ * An enumeration of the main ways we can serialize file system
+ * objects.
  */
 enum struct FileIngestionMethod : uint8_t {
     /**
@@ -20,6 +39,39 @@ enum struct FileIngestionMethod : uint8_t {
     Recursive = true
 };
 
+struct FixedOutputHashMethod {
+  FileIngestionMethod fileIngestionMethod;
+  HashType hashType;
+};
+
+/**
+ * Compute the prefix to the hash algorithm which indicates how the
+ * files were ingested.
+ */
+std::string makeFileIngestionPrefix(FileIngestionMethod m);
+
+
+/**
+ * An enumeration of all the ways we can serialize file system objects.
+ *
+ * Just the type of a content address. Combine with the hash itself, and
+ * we have a `ContentAddress` as defined below. Combine that, in turn,
+ * with info on references, and we have `ContentAddressWithReferences`,
+ * as defined further below.
+ */
+typedef std::variant<
+    TextHashMethod,
+    FixedOutputHashMethod
+> ContentAddressMethod;
+
+ContentAddressMethod parseContentAddressMethod(std::string_view rawCaMethod);
+
+std::string renderContentAddressMethod(ContentAddressMethod caMethod);
+
+/*
+ * Mini content address
+ */
+
 /**
  * Somewhat obscure, used by \ref Derivation derivations and
  * `builtins.toFile` currently.
@@ -29,10 +81,12 @@ struct TextHash {
      * Hash of the contents of the text/file.
      */
     Hash hash;
+
+    GENERATE_CMP(TextHash, me->hash);
 };
 
 /**
- * For path computed by makeFixedOutputPath.
+ * Used by most store objects that are content-addressed.
  */
 struct FixedOutputHash {
     /**
@@ -45,6 +99,8 @@ struct FixedOutputHash {
     Hash hash;
 
     std::string printMethodAlgo() const;
+
+    GENERATE_CMP(FixedOutputHash, me->method, me->hash);
 };
 
 /**
@@ -65,17 +121,9 @@ typedef std::variant<
 > ContentAddress;
 
 /**
- * Compute the prefix to the hash algorithm which indicates how the
- * files were ingested.
- */
-std::string makeFileIngestionPrefix(const FileIngestionMethod m);
-
-/**
  * Compute the content-addressability assertion (ValidPathInfo::ca) for
  * paths created by Store::makeFixedOutputPath() / Store::addToStore().
  */
-std::string makeFixedOutputCA(FileIngestionMethod method, const Hash & hash);
-
 std::string renderContentAddress(ContentAddress ca);
 
 std::string renderContentAddress(std::optional<ContentAddress> ca);
@@ -86,14 +134,65 @@ std::optional<ContentAddress> parseContentAddressOpt(std::string_view rawCaOpt);
 
 Hash getContentAddressHash(const ContentAddress & ca);
 
+
+/**
+ * A set of references to other store objects.
+ *
+ * References to other store objects are tracked with store paths, self
+ * references however are tracked with a boolean.
+ */
+struct StoreReferences {
+    /**
+     * References to other store objects
+     */
+    StorePathSet others;
+
+    /**
+     * Reference to this store object
+     */
+    bool self = false;
+
+    /**
+     * @return true iff no references, i.e. others is empty and self is
+     * false.
+     */
+    bool empty() const;
+
+    /**
+     * Returns the numbers of references, i.e. the size of others + 1
+     * iff self is true.
+     */
+    size_t size() const;
+
+    GENERATE_CMP(StoreReferences, me->self, me->others);
+};
+
 /*
-  We only have one way to hash text with references, so this is single-value
-  type is only useful in std::variant.
-*/
-struct TextHashMethod { };
-struct FixedOutputHashMethod {
-  FileIngestionMethod fileIngestionMethod;
-  HashType hashType;
+ * Full content address
+ *
+ * See the schema for store paths in store-api.cc
+ */
+
+// This matches the additional info that we need for makeTextPath
+struct TextInfo {
+    TextHash hash;
+    /**
+     * References to other store objects only; self references
+     * disallowed
+     */
+    StorePathSet references;
+
+    GENERATE_CMP(TextInfo, me->hash, me->references);
+};
+
+struct FixedOutputInfo {
+    FixedOutputHash hash;
+    /**
+     * References to other store objects or this one.
+     */
+    StoreReferences references;
+
+    GENERATE_CMP(FixedOutputInfo, me->hash, me->references);
 };
 
 /**
@@ -102,12 +201,14 @@ struct FixedOutputHashMethod {
  * A ContentAddress without a Hash.
  */
 typedef std::variant<
-    TextHashMethod,
-    FixedOutputHashMethod
-  > ContentAddressMethod;
+    TextInfo,
+    FixedOutputInfo
+> ContentAddressWithReferences;
 
-ContentAddressMethod parseContentAddressMethod(std::string_view rawCaMethod);
-
-std::string renderContentAddressMethod(ContentAddressMethod caMethod);
+/**
+ * Create a ContentAddressWithReferences from a mere ContentAddress, by
+ * assuming no references in all cases.
+ */
+ContentAddressWithReferences caWithoutRefs(const ContentAddress &);
 
 }