for example,

{["15"] = 7,["16"] = 9,["17"] = 9,["18"] = 9,["19"] = 9,["21"] = 10,["24"] = 9,["25"] = 9,["26"] = 13,["27"] = 13,["28"] = 13,["29"] = 13,["30"] = 14,["31"] = 13,["32"] = 13})

can be written as

{0,0,0,0,0,0,0,0,0,0,0,0,0,0,7,9,9,9,9,9,10,10,10,9,9,13,13,13,13,14,13,13,13}

zero indexed, so just -1 when finding the line. if line is nil or 0, then it is not found.

EDIT: possibly it is a concern that the source starts very late (in the case of a bundle). could have an offset to remove the need for leading zeroes