Function GenNode

src/test/fuzz/miniscript.cpp:854–1007

 */
template <typename F>
std::optional<Node> GenNode(MsCtx script_ctx, F ConsumeNode, Type root_type, bool strict_valid = false)
{
    /** A stack of miniscript Nodes being built up. */
    std::vector<Node> stack;
    /** The queue of instructions. */
    std::vector<std::pair<Type, std::optional<NodeInfo>>> todo{{root_type, {}}};
    /** Predict the number of (static) script ops. */
    uint32_t ops{0};
    /** Predict the total script size (every unexplored subnode is counted as one, as every leaf is
     *  at least one script byte). */
    uint32_t scriptsize{1};

    while (!todo.empty()) {
        // The expected type we have to construct.
        auto type_needed = todo.back().first;
        if (!todo.back().second) {
            // Fragment/children have not been decided yet. Decide them.
            auto node_info = ConsumeNode(type_needed);
            if (!node_info) return {};
            // Update predicted resource limits. Since every leaf Miniscript node is at least one
            // byte long, we move one byte from each child to their parent. A similar technique is
            // used in the miniscript::internal::Parse function to prevent runaway string parsing.
            scriptsize += miniscript::internal::ComputeScriptLen(node_info->fragment, ""_mst, node_info->subtypes.size(), node_info->k, node_info->subtypes.size(),
                                                                 node_info->keys.size(), script_ctx) - 1;
            if (scriptsize > MAX_STANDARD_P2WSH_SCRIPT_SIZE) return {};
            switch (node_info->fragment) {
            case Fragment::JUST_0:
            case Fragment::JUST_1:
                break;
            case Fragment::PK_K:
                break;
            case Fragment::PK_H:
                ops += 3;
                break;
            case Fragment::OLDER:
            case Fragment::AFTER:
                ops += 1;
                break;
            case Fragment::RIPEMD160:
            case Fragment::SHA256:
            case Fragment::HASH160:
            case Fragment::HASH256:
                ops += 4;
                break;
            case Fragment::ANDOR:
                ops += 3;
                break;
            case Fragment::AND_V:
                break;
            case Fragment::AND_B:
            case Fragment::OR_B:
                ops += 1;
                break;
            case Fragment::OR_C:
                ops += 2;
                break;
            case Fragment::OR_D:
                ops += 3;