From 6510d0ff4173a7b01d6728051303c7c38eb34533 Mon Sep 17 00:00:00 2001
From: Jeremy Rubin <j@rubin.io>
Date: Wed, 5 Feb 2020 11:57:32 -0800
Subject: [PATCH] Add SHA256Uint256 helper functions

---
 src/hash.cpp | 7 +++++++
 src/hash.h   | 4 ++++
 2 files changed, 11 insertions(+)

diff --git a/src/hash.cpp b/src/hash.cpp
index 4c09f5f6463..83b90ae063f 100644
--- a/src/hash.cpp
+++ b/src/hash.cpp
@@ -77,3 +77,10 @@ void BIP32Hash(const ChainCode &chainCode, unsigned int nChild, unsigned char he
     num[3] = (nChild >>  0) & 0xFF;
     CHMAC_SHA512(chainCode.begin(), chainCode.size()).Write(&header, 1).Write(data, 32).Write(num, 4).Finalize(output);
 }
+
+uint256 SHA256Uint256(const uint256& input)
+{
+    uint256 result;
+    CSHA256().Write(input.begin(), 32).Finalize(result.begin());
+    return result;
+}
diff --git a/src/hash.h b/src/hash.h
index 4f392fa0aa3..c16bbb48cea 100644
--- a/src/hash.h
+++ b/src/hash.h
@@ -6,6 +6,7 @@
 #ifndef BITCOIN_HASH_H
 #define BITCOIN_HASH_H
 
+#include <attributes.h>
 #include <crypto/common.h>
 #include <crypto/ripemd160.h>
 #include <crypto/sha256.h>
@@ -194,6 +195,9 @@ uint256 SerializeHash(const T& obj, int nType=SER_GETHASH, int nVersion=PROTOCOL
     return ss.GetHash();
 }
 
+/** Single-SHA256 a 32-byte input (represented as uint256). */
+NODISCARD uint256 SHA256Uint256(const uint256& input);
+
 unsigned int MurmurHash3(unsigned int nHashSeed, Span<const unsigned char> vDataToHash);
 
 void BIP32Hash(const ChainCode &chainCode, unsigned int nChild, unsigned char header, const unsigned char data[32], unsigned char output[64]);