bug#122: 23.0.60; Slowdown in directory scanning over time.

[Richard M. Stallman]

    (1) A coding system can have pre-write-conversion function,
    and that function can call code-conversion function
    recursively.

I read in the doc string of define-coding-system
that the pre-write-conversion function is called
before doing the ordinary work of encoding.

Is it possible to call the pre-write-conversion function
before obtaining the work buffer?  That way, there would never
be recursive encoding.

    (2) If REPLACE arg is non-nil in insert-file-contents and a
    file need a decoding, we call decode_coding_c_string while a
    work buffer is in use.

I see why decoding is needed in this case, but why is a work
buffer already in use?  It seems to me that there is only one
act of decoding to be done in that call to insert-file-contents.