presto-orc/src/main/java/io/prestosql/orc/reader/ReaderUtils.java/ReaderUtils/convertLengthVectorToOffsetVector
class ReaderUtils:    public static void convertLengthVectorToOffsetVector(int[] vector)
    {
        int currentLength = vector[0];
        vector[0] = 0;
        for (int i = 1; i < vector.length; i++) {
            int nextLength = vector[i];
            vector[i] = vector[i - 1] + currentLength;
            currentLength = nextLength;
        }
    }