1 files changed, 113 insertions, 0 deletions
diff --git a/src/script/sigcache.cpp b/src/script/sigcache.cpp
new file mode 100644
index 000000000..bdc0bfdc1
--- /dev/null
+++ b/src/script/sigcache.cpp
@@ -0,0 +1,113 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2015 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "sigcache.h"
+
+#include "memusage.h"
+#include "pubkey.h"
+#include "random.h"
+#include "uint256.h"
+#include "util.h"
+
+#include <boost/thread.hpp>
+#include <boost/unordered_set.hpp>
+
+namespace {
+
+/**
+ * We're hashing a nonce into the entries themselves, so we don't need extra
+ * blinding in the set hash computation.
+ */
+class CSignatureCacheHasher
+{
+public:
+    size_t operator()(const uint256& key) const {
+        return key.GetCheapHash();
+    }
+};
+
+/**
+ * Valid signature cache, to avoid doing expensive ECDSA signature checking
+ * twice for every transaction (once when accepted into memory pool, and
+ * again when accepted into the block chain)
+ */
+class CSignatureCache
+{
+private:
+     //! Entries are SHA256(nonce || signature hash || public key || signature):
+    uint256 nonce;
+    typedef boost::unordered_set<uint256, CSignatureCacheHasher> map_type;
+    map_type setValid;
+    boost::shared_mutex cs_sigcache;
+
+
+public:
+    CSignatureCache()
+    {
+        GetRandBytes(nonce.begin(), 32);
+    }
+
+    void
+    ComputeEntry(uint256& entry, const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubkey)
+    {
+        CSHA256().Write(nonce.begin(), 32).Write(hash.begin(), 32).Write(&pubkey[0], pubkey.size()).Write(&vchSig[0], vchSig.size()).Finalize(entry.begin());
+    }
+
+    bool
+    Get(const uint256& entry)
+    {
+        boost::shared_lock<boost::shared_mutex> lock(cs_sigcache);
+        return setValid.count(entry);
+    }
+
+    void Erase(const uint256& entry)
+    {
+        boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);
+        setValid.erase(entry);
+    }
+
+    void Set(const uint256& entry)
+    {
+        size_t nMaxCacheSize = GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
+        if (nMaxCacheSize <= 0) return;
+
+        boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);
+        while (memusage::DynamicUsage(setValid) > nMaxCacheSize)
+        {
+            map_type::size_type s = GetRand(setValid.bucket_count());
+            map_type::local_iterator it = setValid.begin(s);
+            if (it != setValid.end(s)) {
+                setValid.erase(*it);
+            }
+        }
+
+        setValid.insert(entry);
+    }
+};
+
+}
+
+bool CachingTransactionSignatureChecker::VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash) const
+{
+    static CSignatureCache signatureCache;
+
+    uint256 entry;
+    signatureCache.ComputeEntry(entry, sighash, vchSig, pubkey);
+
+    if (signatureCache.Get(entry)) {
+        if (!store) {
+            signatureCache.Erase(entry);
+        }
+        return true;
+    }
+
+    if (!TransactionSignatureChecker::VerifySignature(vchSig, pubkey, sighash))
+        return false;
+
+    if (store) {
+        signatureCache.Set(entry);
+    }
+    return true;
+}