胸有成竹　

◎ 胸有成竹 xiōngyǒu-chéngzhú

[to have a well-thought-out plan beforehand;have a card up one‘s sleeves;have a contrivance ready] 胸有成算。比喻作事之先已有成算在胸

岂知皮匠胸有成竹,早把火刀、火石摸在手中,一敲就着。——清· 李绿园《岐路灯》