From f7303f97933be33e34d482cf8348d180c8da2a26 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Tue, 17 Mar 2015 06:35:59 -0700
Subject: Use equivalent PoW for non-main-chain requests

---
 src/pow.cpp | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

(limited to 'src/pow.cpp')

diff --git a/src/pow.cpp b/src/pow.cpp
index fc6ed4f3d1..bb53ad204b 100644
--- a/src/pow.cpp
+++ b/src/pow.cpp
@@ -114,3 +114,20 @@ arith_uint256 GetBlockProof(const CBlockIndex& block)
     // or ~bnTarget / (nTarget+1) + 1.
     return (~bnTarget / (bnTarget + 1)) + 1;
 }
+
+int64_t GetBlockProofEquivalentTime(const CBlockIndex& to, const CBlockIndex& from, const CBlockIndex& tip, const Consensus::Params& params)
+{
+    arith_uint256 r;
+    int sign = 1;
+    if (to.nChainWork > from.nChainWork) {
+        r = to.nChainWork - from.nChainWork;
+    } else {
+        r = from.nChainWork - to.nChainWork;
+        sign = -1;
+    }
+    r = r * arith_uint256(params.nPowTargetSpacing) / GetBlockProof(tip);
+    if (r.bits() > 63) {
+        return sign * std::numeric_limits<int64_t>::max();
+    }
+    return sign * r.GetLow64();
+}
-- 
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