Function DecodeScript

src/script/miniscript.h:2298–2682

//! Parse a miniscript from a bitcoin script
template <typename Key, typename Ctx, typename I>
inline std::optional<Node<Key>> DecodeScript(I& in, I last, const Ctx& ctx)
{
    // The two integers are used to hold state for thresh()
    std::vector<std::tuple<DecodeContext, int64_t, int64_t>> to_parse;
    std::vector<Node<Key>> constructed;

    // This is the top level, so we assume the type is B
    // (in particular, disallowing top level W expressions)
    to_parse.emplace_back(DecodeContext::BKV_EXPR, -1, -1);

    while (!to_parse.empty()) {
        // Exit early if the Miniscript is not going to be valid.
        if (!constructed.empty() && !constructed.back().IsValid()) return {};

        // Get the current context we are decoding within
        auto [cur_context, n, k] = to_parse.back();
        to_parse.pop_back();

        switch(cur_context) {
        case DecodeContext::SINGLE_BKV_EXPR: {
            if (in >= last) return {};

            // Constants
            if (in[0].first == OP_1) {
                ++in;
                constructed.emplace_back(internal::NoDupCheck{}, ctx.MsContext(), Fragment::JUST_1);
                break;
            }
            if (in[0].first == OP_0) {
                ++in;
                constructed.emplace_back(internal::NoDupCheck{}, ctx.MsContext(), Fragment::JUST_0);
                break;
            }
            // Public keys
            if (in[0].second.size() == 33 || in[0].second.size() == 32) {
                auto key = ctx.FromPKBytes(in[0].second.begin(), in[0].second.end());
                if (!key) return {};
                ++in;
                constructed.emplace_back(internal::NoDupCheck{}, ctx.MsContext(), Fragment::PK_K, Vector(std::move(*key)));
                break;
            }
            if (last - in >= 5 && in[0].first == OP_VERIFY && in[1].first == OP_EQUAL && in[3].first == OP_HASH160 && in[4].first == OP_DUP && in[2].second.size() == 20) {
                auto key = ctx.FromPKHBytes(in[2].second.begin(), in[2].second.end());
                if (!key) return {};
                in += 5;
                constructed.emplace_back(internal::NoDupCheck{}, ctx.MsContext(), Fragment::PK_H, Vector(std::move(*key)));
                break;
            }
            // Time locks
            std::optional<int64_t> num;
            if (last - in >= 2 && in[0].first == OP_CHECKSEQUENCEVERIFY && (num = ParseScriptNumber(in[1]))) {
                in += 2;
                if (*num < 1 || *num > 0x7FFFFFFFL) return {};
                constructed.emplace_back(internal::NoDupCheck{}, ctx.MsContext(), Fragment::OLDER, *num);
                break;
            }
            if (last - in >= 2 && in[0].first == OP_CHECKLOCKTIMEVERIFY && (num = ParseScriptNumber(in[1]))) {
                in += 2;