function isSingleByte(v: number): boolean {
 return (v >> 7) === 0;
}
function isContinuationByte(v: number): boolean {
 return (v >> 6) === 0b10;
}
function getContinuationBytesCount(v: number): number {
 if ((v >> 5) === 0b110) return 1;
 if ((v >> 4) === 0b1110) return 2;
 if ((v >> 3) === 0b11110) return 3;
 return -1;
}
function validUtf8(data: number[]): boolean {
 let cnt = 0;
 for (const v of data) {
 if (cnt > 0) {
 if (!isContinuationByte(v)) {
 return false;
 }
 --cnt;
 } else if (isSingleByte(v)) {
 cnt = 0;
 } else {
 const newCnt = getContinuationBytesCount(v);
 if (newCnt === -1) {
 return false;
 }
 cnt = newCnt;
 }
 }
 return cnt === 0;
}