* [Caml-list] HELP! In-place modification of caml globals...
@ 2005-12-22 4:03 Jonathan Roewen
2005-12-22 4:23 ` Jonathan Roewen
0 siblings, 1 reply; 2+ messages in thread
From: Jonathan Roewen @ 2005-12-22 4:03 UTC (permalink / raw)
To: caml-list
Hi,
I need some help, badly ;-) This is the one thing getting in my way at
present, and I don't know how to fix it.
I have two types:
type in_channel = {
mutable in_read : unit -> char;
mutable in_input : string -> int -> int -> int;
mutable in_seek : int -> unit;
mutable in_tell : unit -> int;
mutable in_close : unit -> unit;
mutable in_length : unit -> int;
}
type 'a out_channel = {
mutable out_write : char -> unit;
mutable out_output : string -> int -> int -> unit;
mutable out_seek : int -> unit;
mutable out_tell : unit -> int;
mutable out_close : unit -> 'a;
mutable out_flush : unit -> unit;
mutable out_length : unit -> int;
}
and three globals:
let stdin =
let read = (fun _ -> raise Input_closed)
and input = (fun _ _ _ -> raise Input_closed)
and seek = (fun _ -> raise Input_closed)
and tell = (fun _ -> raise Input_closed)
in create_in read input seek tell default_close default_length
let stdout =
let write = (fun _ -> raise Output_closed)
and output = (fun _ _ _ -> raise Output_closed)
and seek = (fun _ -> raise Output_closed)
and tell = (fun _ -> raise Output_closed)
in create_out write output seek tell default_close default_flush default_length
let stderr =
let write = (fun _ -> raise Output_closed)
and output = (fun _ _ _ -> raise Output_closed)
and seek = (fun _ -> raise Output_closed)
and tell = (fun _ -> raise Output_closed)
in create_out write output seek tell default_close default_flush default_length
By default, they're all closed. What I want to do is swap them with
other instances at kernel startup.
So I defined two external functions:
external swap_input : in_channel -> in_channel -> unit = "caml_ml_swap_input";;
external swap_output : unit out_channel -> unit out_channel -> unit =
"caml_ml_swap_output";;
Which are both defined as:
value caml_ml_swap_input(value to, value from) {
/* record has 6 fields */
Store_field(to, 0, Field(from, 0));
Store_field(to, 1, Field(from, 1));
Store_field(to, 2, Field(from, 2));
Store_field(to, 3, Field(from, 3));
Store_field(to, 4, Field(from, 4));
Store_field(to, 5, Field(from, 5));
return Val_unit;
}
value caml_ml_swap_output(value to, value from) {
/* record has 7 fields */
Store_field(to, 0, Field(from, 0));
Store_field(to, 1, Field(from, 1));
Store_field(to, 2, Field(from, 2));
Store_field(to, 3, Field(from, 3));
Store_field(to, 4, Field(from, 4));
Store_field(to, 5, Field(from, 5));
Store_field(to, 6, Field(from, 6));
return Val_unit;
}
Then initialise with:
(* init the standard IO descriptors *)
swap_input stdin kernel_stdin;;
swap_output stdout kernel_stdout;;
swap_output stderr kernel_stderr;;
However, as soon as I try to print, I get a fatal error that output
stream is closed =/
What's the correct way to do this?
Jonathan
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