Function CodepointStart

deps/v8/test/mjsunit/wasm/stringrefs-exec.js:956–962

(wtf8, offset)

    return wtf8.length;
  }
  function CodepointStart(wtf8, offset) {
    if (offset >= wtf8.length) return wtf8.length;
    while (!Wtf8StartsCodepoint(wtf8, offset)) {
      offset--;
    }
    return offset;
  }

  let instance = builder.instantiate();
  let memory = new Uint8Array(instance.exports.memory.buffer);