Move `PodIdx` to `pos-idx.hh` and `PosTable` to `pos-table.hh`

(cherry picked from commit c62c21e29af20f1c14a59ab37d7a25dd0b70f69e)
Change-Id: Id4ea2fc33b0874b2f1f2a32cabcbeb0afa26808f

1 files changed, 48 insertions, 0 deletions

diff --git a/src/libexpr/pos-idx.hh b/src/libexpr/pos-idx.hh
new file mode 100644
index 000000000..9949f1dc5
--- /dev/null
+++ b/src/libexpr/pos-idx.hh
@@ -0,0 +1,48 @@
+#pragma once
+
+#include <cinttypes>
+
+namespace nix {
+
+class PosIdx
+{
+    friend class PosTable;
+
+private:
+    uint32_t id;
+
+    explicit PosIdx(uint32_t id)
+        : id(id)
+    {
+    }
+
+public:
+    PosIdx()
+        : id(0)
+    {
+    }
+
+    explicit operator bool() const
+    {
+        return id > 0;
+    }
+
+    bool operator<(const PosIdx other) const
+    {
+        return id < other.id;
+    }
+
+    bool operator==(const PosIdx other) const
+    {
+        return id == other.id;
+    }
+
+    bool operator!=(const PosIdx other) const
+    {
+        return id != other.id;
+    }
+};
+
+inline PosIdx noPos = {};
+
+}