Miniscript: conversion from script

Co-Authored-By: Antoine Poinsot <darosior@protonmail.com>
Co-Authored-By: Samuel Dobson <dobsonsa68@gmail.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/src/script/miniscript.cpp b/src/script/miniscript.cpp
index 8074be6cde..d0bb937885 100644
--- a/src/script/miniscript.cpp
+++ b/src/script/miniscript.cpp
@@ -5,6 +5,7 @@
 #include <string>
 #include <vector>
 #include <script/script.h>
+#include <script/standard.h>
 #include <script/miniscript.h>
 
 #include <assert.h>
@@ -281,6 +282,58 @@ size_t ComputeScriptLen(Fragment nodetype, Type sub0typ, size_t subsize, uint32_
     return 0;
 }
 
+bool DecomposeScript(const CScript& script, std::vector<std::pair<opcodetype, std::vector<unsigned char>>>& out)
+{
+    out.clear();
+    CScript::const_iterator it = script.begin(), itend = script.end();
+    while (it != itend) {
+        std::vector<unsigned char> push_data;
+        opcodetype opcode;
+        if (!script.GetOp(it, opcode, push_data)) {
+            out.clear();
+            return false;
+        } else if (opcode >= OP_1 && opcode <= OP_16) {
+            // Deal with OP_n (GetOp does not turn them into pushes).
+            push_data.assign(1, CScript::DecodeOP_N(opcode));
+        } else if (opcode == OP_CHECKSIGVERIFY) {
+            // Decompose OP_CHECKSIGVERIFY into OP_CHECKSIG OP_VERIFY
+            out.emplace_back(OP_CHECKSIG, std::vector<unsigned char>());
+            opcode = OP_VERIFY;
+        } else if (opcode == OP_CHECKMULTISIGVERIFY) {
+            // Decompose OP_CHECKMULTISIGVERIFY into OP_CHECKMULTISIG OP_VERIFY
+            out.emplace_back(OP_CHECKMULTISIG, std::vector<unsigned char>());
+            opcode = OP_VERIFY;
+        } else if (opcode == OP_EQUALVERIFY) {
+            // Decompose OP_EQUALVERIFY into OP_EQUAL OP_VERIFY
+            out.emplace_back(OP_EQUAL, std::vector<unsigned char>());
+            opcode = OP_VERIFY;
+        } else if (IsPushdataOp(opcode)) {
+            if (!CheckMinimalPush(push_data, opcode)) return false;
+        } else if (it != itend && (opcode == OP_CHECKSIG || opcode == OP_CHECKMULTISIG || opcode == OP_EQUAL) && (*it == OP_VERIFY)) {
+            // Rule out non minimal VERIFY sequences
+            return false;
+        }
+        out.emplace_back(opcode, std::move(push_data));
+    }
+    std::reverse(out.begin(), out.end());
+    return true;
+}
+
+bool ParseScriptNumber(const std::pair<opcodetype, std::vector<unsigned char>>& in, int64_t& k) {
+    if (in.first == OP_0) {
+        k = 0;
+        return true;
+    }
+    if (!in.second.empty()) {
+        if (IsPushdataOp(in.first) && !CheckMinimalPush(in.second, in.first)) return false;
+        try {
+            k = CScriptNum(in.second, true).GetInt64();
+            return true;
+        } catch(const scriptnum_error&) {}
+    }
+    return false;
+}
+
 int FindNextChar(Span<const char> sp, const char m)
 {
     for (int i = 0; i < (int)sp.size(); ++i) {