```\nfor (uint i = 0; i < \_blockheaders.length; i++) {\n    (calcParent, calcBlockhash) = getParentAndBlockhash(\_blockheaders[i]);\n    if (calcBlockhash != currentBlockhash) {\n        return 0x0;\n    }\n    currentBlockhash = calcParent;\n}\n```\n