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diff --git a/indra/llcommon/resultset.h b/indra/llcommon/resultset.h
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+/**
+ * @file   resultset.h
+ * @author Nat Goodspeed
+ * @date   2024-09-03
+ * @brief  ResultSet is an abstract base class to allow scripted access to
+ *         potentially large collections representable as LLSD arrays.
+ *
+ * $LicenseInfo:firstyear=2024&license=viewerlgpl$
+ * Copyright (c) 2024, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+#if ! defined(LL_RESULTSET_H)
+#define LL_RESULTSET_H
+
+#include "llinttracker.h"
+#include "llsd.h"
+#include <iosfwd>                   // std::ostream
+#include <utility>                  // std::pair
+#include <vector>
+
+namespace LL
+{
+
+// This abstract base class defines an interface by which a large collection
+// of items representable as an LLSD array can be retrieved in slices. It isa
+// LLIntTracker so we can pass its unique int key to a consuming script via
+// LLSD.
+struct ResultSet: public LLIntTracker<ResultSet>
+{
+    // Get the length of the result set. Indexes are 0-relative.
+    virtual int getLength() const = 0;
+    // Get conventional LLSD { key, length } pair.
+    LLSD getKeyLength() const;
+    // Retrieve LLSD corresponding to a single entry from the result set,
+    // once we're sure the index is valid.
+    virtual LLSD getSingle(int index) const = 0;
+    // Retrieve LLSD corresponding to a "slice" of the result set: a
+    // contiguous sub-array starting at index. The returned LLSD array might
+    // be shorter than count entries if count > MAX_ITEM_LIMIT, or if the
+    // specified slice contains the end of the result set.
+    LLSD getSlice(int index, int count) const;
+    // Like getSlice(), but also return adjusted start position.
+    std::pair<LLSD, int> getSliceStart(int index, int count) const;
+
+    /*---------------- the rest is solely for debug logging ----------------*/
+    std::string mName;
+
+    ResultSet(const std::string& name);
+    virtual ~ResultSet();
+};
+
+// VectorResultSet is for the simple case of a ResultSet managing a single
+// std::vector<T>.
+template <typename T>
+struct VectorResultSet: public ResultSet
+{
+    using super = VectorResultSet<T>;
+
+    VectorResultSet(const std::string& name): ResultSet(name) {}
+    int getLength() const override { return narrow(mVector.size()); }
+    LLSD getSingle(int index) const override { return getSingleFrom(mVector[index]); }
+    virtual LLSD getSingleFrom(const T&) const = 0;
+
+    std::vector<T> mVector;
+};
+
+} // namespace LL
+
+std::ostream& operator<<(std::ostream& out, const LL::ResultSet& self);
+
+#endif /* ! defined(LL_RESULTSET_H) */