Recognize pegout scripts

src/script/script.cpp

@@ -194,6 +194,49 @@ unsigned int CScript::GetSigOpCount(const CScript& scriptSig) const
     return subscript.GetSigOpCount(true);
 }
 
+//
+// ELEMENTS:
+
+bool CScript::IsPegoutScript(uint256& genesis_hash, CScript& pegout_scriptpubkey) const
+{
+    const_iterator pc = begin();
+    std::vector<unsigned char> data;
+    opcodetype opcode;
+
+    // OP_RETURN
+    if (!GetOp(pc, opcode, data) || opcode != OP_RETURN) {
+        return false;
+    }
+
+    if (!GetOp(pc, opcode, data) || data.size() != 32 ) {
+        return false;
+    }
+    genesis_hash = uint256(data);
+
+    // Read in parent chain destination scriptpubkey
+    if (!GetOp(pc, opcode, data) || data.size() == 0 ) {
+        return false;
+    }
+    pegout_scriptpubkey = CScript(data.begin(), data.end());
+
+    return true;
+}
+
+bool CScript::IsPegoutScript(const uint256& genesis_hash_check) const
+{
+    uint256 genesis_hash;
+    CScript pegout_scriptpubkey;
+    // Ensure hash matches parent chain genesis block
+    if (this->IsPegoutScript(genesis_hash, pegout_scriptpubkey) &&
+        genesis_hash_check == genesis_hash) {
+        return true;
+    }
+    return false;
+}
+
+// END ELEMENTS
+//
+
 bool CScript::IsPayToScriptHash() const
 {
     // Extra-fast test for pay-to-script-hash CScripts:

src/script/script.h

@@ -17,6 +17,7 @@
 #include <stdint.h>
 #include <string.h>
 #include <string>
+#include <uint256.h>
 #include <vector>
 
 // Maximum number of bytes pushable to the stack
@@ -540,6 +541,15 @@ public:
     bool IsPayToWitnessScriptHash() const;
     bool IsWitnessProgram(int& version, std::vector<unsigned char>& program) const;
 
+    // ELEMENTS:
+    // Returns true if script follows OP_RETURN <genesis_block_hash> <pegout_scriptpubkey>
+    // and if correct it returns both things in the output parameters.
+    bool IsPegoutScript(uint256& genesis_hash, CScript& pegout_scriptpubkey) const;
+    // Returns true if script follows OP_RETURN <genesis_block_hash> <destination_scriptpubkey>
+    // it may also have additional pushes at the end. It checks
+    // the genesis hash matches the specified one.
+    bool IsPegoutScript(const uint256& genesis_hash) const;
+
     /** Called by IsStandardTx and P2SH/BIP62 VerifyScript (which makes it consensus-critical). */
     bool IsPushOnly(const_iterator pc) const;
     bool IsPushOnly() const;