diff options
Diffstat (limited to 'src/script/interpreter.cpp')
| -rw-r--r-- | src/script/interpreter.cpp | 30 |
1 files changed, 27 insertions, 3 deletions
diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp index 20fae2eebf..7a34c9c48d 100644 --- a/src/script/interpreter.cpp +++ b/src/script/interpreter.cpp @@ -278,6 +278,30 @@ int FindAndDelete(CScript& script, const CScript& b) return nFound; } +namespace { +/** A data type to abstract out the condition stack during script execution. + * + * Conceptually it acts like a vector of booleans, one for each level of nested + * IF/THEN/ELSE, indicating whether we're in the active or inactive branch of + * each. + * + * The elements on the stack cannot be observed individually; we only need to + * expose whether the stack is empty and whether or not any false values are + * present at all. To implement OP_ELSE, a toggle_top modifier is added, which + * flips the last value without returning it. + */ +class ConditionStack { +private: + std::vector<bool> m_flags; +public: + bool empty() { return m_flags.empty(); } + bool all_true() { return !std::count(m_flags.begin(), m_flags.end(), false); } + void push_back(bool f) { m_flags.push_back(f); } + void pop_back() { m_flags.pop_back(); } + void toggle_top() { m_flags.back() = !m_flags.back(); } +}; +} + bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptError* serror) { static const CScriptNum bnZero(0); @@ -293,7 +317,7 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& CScript::const_iterator pbegincodehash = script.begin(); opcodetype opcode; valtype vchPushValue; - std::vector<bool> vfExec; + ConditionStack vfExec; std::vector<valtype> altstack; set_error(serror, SCRIPT_ERR_UNKNOWN_ERROR); if (script.size() > MAX_SCRIPT_SIZE) @@ -305,7 +329,7 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& { while (pc < pend) { - bool fExec = !count(vfExec.begin(), vfExec.end(), false); + bool fExec = vfExec.all_true(); // // Read instruction @@ -494,7 +518,7 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& { if (vfExec.empty()) return set_error(serror, SCRIPT_ERR_UNBALANCED_CONDITIONAL); - vfExec.back() = !vfExec.back(); + vfExec.toggle_top(); } break; |