A fu line provides information about a single function within a file. It is followed by information about lines within the function and eventually by a matching efu, indicating the end of function data. No new function can appear before the matching efu line.
The data fields of the function entry are:
fu
<name> <# unused blocks> <# blocks> <# unused lines>
\
<# lines> <# calls>
The <name> field contains the name of the function.
The <# calls> field contains the number of times the function was entered.
The other fields have the same interpretation as in a to line, except summed only within this specific function.