overwrite_len

Description:

public unowned StringBuilder overwrite_len (size_t pos, string val, ssize_t len)

Overwrites part of a string, lengthening it if necessary.

This function will work with embedded nuls.

this	a StringBuilder
pos	the position at which to start overwriting
val	the string that will overwrite the this starting at `pos`
len	the number of bytes to write from `val`

this