Organize content addressing, use SourceAccessor with Store::addToStore

Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>

src/libutil/file-content-address.hh

@@ -0,0 +1,56 @@
+#pragma once
+///@file
+
+#include "source-accessor.hh"
+#include "fs-sink.hh"
+#include "util.hh"
+
+namespace nix {
+
+/**
+ * An enumeration of the main ways we can serialize file system
+ * objects.
+ */
+enum struct FileIngestionMethod : uint8_t {
+    /**
+     * Flat-file hashing. Directly ingest the contents of a single file
+     */
+    Flat = 0,
+    /**
+     * Recursive (or NAR) hashing. Serializes the file-system object in
+     * Nix Archive format and ingest that.
+     */
+    Recursive = 1,
+};
+
+/**
+ * Dump a serialization of the given file system object.
+ */
+void dumpPath(
+    SourceAccessor & accessor, const CanonPath & path,
+    Sink & sink,
+    FileIngestionMethod method,
+    PathFilter & filter = defaultPathFilter);
+
+/**
+ * Restore a serialization of the given file system object.
+ *
+ * @TODO use an arbitrary `ParseSink`.
+ */
+void restorePath(
+    const Path & path,
+    Source & source,
+    FileIngestionMethod method);
+
+/**
+ * Compute the hash of the given file system object according to the
+ * given method.
+ *
+ * The hash is defined as (essentially) hashString(ht, dumpPath(path)).
+ */
+HashResult hashPath(
+    SourceAccessor & accessor, const CanonPath & path,
+    FileIngestionMethod method, HashAlgorithm ht,
+    PathFilter & filter = defaultPathFilter);
+
+}