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diff --git a/src/serialize.h b/src/serialize.h
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -703,6 +703,54 @@
return BigEndian<I>(n);
}
+/**
+ * Formatter to serialize/deserialize vector elements using another formatter
+ *
+ * Example:
+ * struct X {
+ * std::vector<uint64_t> v;
+ * SERIALIZE_METHODS(X, obj) {
+ * READWRITE(Using<VectorFormatter<VarInt>>(obj.v));
+ * }
+ * };
+ * will define a struct that contains a vector of uint64_t, which is serialized
+ * as a vector of VarInt-encoded integers.
+ *
+ * V is not required to be an std::vector type. It works for any class that
+ * exposes a value_type, size, reserve, push_back, and const iterators.
+ */
+template <class Formatter> struct VectorFormatter {
+ template <typename Stream, typename V> void Ser(Stream &s, const V &v) {
+ WriteCompactSize(s, v.size());
+ for (const typename V::value_type &elem : v) {
+ s << Using<Formatter>(elem);
+ }
+ }
+
+ template <typename Stream, typename V> void Unser(Stream &s, V &v) {
+ v.clear();
+ size_t size = ReadCompactSize(s);
+ size_t allocated = 0;
+ while (allocated < size) {
+ // For DoS prevention, do not blindly allocate as much as the stream
+ // claims to contain. Instead, allocate in 5MiB batches, so that an
+ // attacker actually needs to provide X MiB of data to make us
+ // allocate X+5 Mib.
+ static_assert(sizeof(typename V::value_type) <= MAX_VECTOR_ALLOCATE,
+ "Vector element size too large");
+ allocated =
+ std::min(size, allocated + MAX_VECTOR_ALLOCATE /
+ sizeof(typename V::value_type));
+ v.reserve(allocated);
+ while (v.size() < allocated) {
+ typename V::value_type val;
+ s >> Using<Formatter>(val);
+ v.push_back(std::move(val));
+ }
+ }
+ };
+};
+
/**
* Forward declarations
*/

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