Variable: read-buffer-function
read-buffer-function is a customizable variable defined in minibuf.c.
Value
nil
Documentation
If this is non-nil, read-buffer does its work by calling this function.
The function is called with the arguments passed to read-buffer.
Probably introduced at or before Emacs version 20.3.
Source Code
// Defined in /usr/src/emacs/src/minibuf.c
DEFVAR_LISP ("read-buffer-function", Vread_buffer_function,
doc: /* If this is non-nil, `read-buffer' does its work by calling this function.
The function is called with the arguments passed to `read-buffer'. */);