Inserts n_chars characters of chars into the contents of the
buffer, at position position.
If n_chars is negative, then characters from chars will be inserted
until a null-terminator is found. If position or n_chars are out of
bounds, or the maximum buffer text length is exceeded, then they are
coerced to sane values.
Note that the position and length are in characters, not in bytes.
Inserts n_chars characters of chars into the contents of the buffer, at position position.
If n_chars is negative, then characters from chars will be inserted until a null-terminator is found. If position or n_chars are out of bounds, or the maximum buffer text length is exceeded, then they are coerced to sane values.
Note that the position and length are in characters, not in bytes.