(* Bitmatch syntax extension.
- * $Id: pa_bitmatch.ml,v 1.1 2008-03-31 22:52:17 rjones Exp $
+ * $Id: pa_bitmatch.ml,v 1.5 2008-04-01 19:10:45 rjones Exp $
*)
open Printf
open Syntax
open Ast
+(* If this is true then we emit some debugging code which can
+ * be useful to tell what is happening during matches. You
+ * also need to do 'Bitmatch.debug := true' in your main program.
+ *
+ * If this is false then no extra debugging code is emitted.
+ *)
+let debug = true
+
type m = Fields of f list (* field ; field -> ... *)
| Bind of string option (* _ -> ... *)
and f = {
- ident : string; (* field name *)
+ (* XXX fval should be a patt, not an expr *)
+ fval : expr; (* field binding or value *)
flen : expr; (* length in bits, may be non-const *)
endian : endian; (* endianness *)
signed : bool; (* true if signed, false if unsigned *)
t : t; (* type *)
+ _loc : Loc.t; (* location in source code *)
}
and endian = BigEndian | LittleEndian | NativeEndian
and t = Int | Bitstring
sprintf "__pabitmatch_%s_%d" name i
(* Deal with the qualifiers which appear for a field. *)
-let output_field _loc name flen qs =
+let parse_field _loc fval flen qs =
let endian, signed, t =
match qs with
| None -> (None, None, None)
let t = match t with None -> Int | Some t -> t in
{
- ident = name;
+ fval = fval;
flen = flen;
endian = endian;
signed = signed;
t = t;
+ _loc = _loc;
}
+let string_of_endian = function
+ | BigEndian -> "bigendian"
+ | LittleEndian -> "littleendian"
+ | NativeEndian -> "nativeendian"
+
+let string_of_t = function
+ | Int -> "int"
+ | Bitstring -> "bitstring"
+
+let string_of_field { fval = fval; flen = flen;
+ endian = endian; signed = signed; t = t;
+ _loc = _loc } =
+ let fval =
+ match fval with
+ | <:expr< $lid:id$ >> -> id
+ | _ -> "[expression]" in
+ let flen =
+ match flen with
+ | <:expr< $int:i$ >> -> i
+ | _ -> "[non-const-len]" in
+ let endian = string_of_endian endian in
+ let signed = if signed then "signed" else "unsigned" in
+ let t = string_of_t t in
+ let loc_fname = Loc.file_name _loc in
+ let loc_line = Loc.start_line _loc in
+ let loc_char = Loc.start_off _loc - Loc.start_bol _loc in
+
+ sprintf "%s : %s : %s, %s, %s @ (%S, %d, %d)"
+ fval flen t endian signed loc_fname loc_line loc_char
+
+(* Generate the code for a constructor, ie. 'BITSTRING ...'. *)
+let output_constructor _loc fields =
+ let loc_fname = Loc.file_name _loc in
+ let loc_line = string_of_int (Loc.start_line _loc) in
+ let loc_char = string_of_int (Loc.start_off _loc - Loc.start_bol _loc) in
+
+ (* Bitstrings are created like the 'Buffer' module (in fact, using
+ * the Buffer module), by appending snippets to a growing buffer.
+ * This is reasonable efficient and avoids a lot of garbage.
+ *)
+ let buffer = gensym "buffer" in
+
+ (* General exception which is raised inside the constructor functions
+ * when an int expression is out of range at runtime.
+ *)
+ let exn = gensym "exn" in
+ let exn_used = ref false in
+
+ (* Convert each field to a simple bitstring-generating expression. *)
+ let fields = List.map (
+ fun {fval=fval; flen=flen; endian=endian; signed=signed; t=t} ->
+ (* Is flen an integer constant? If so, what is it? This
+ * is very simple-minded and only detects simple constants.
+ *)
+ let flen_is_const =
+ match flen with
+ | <:expr< $int:i$ >> -> Some (int_of_string i)
+ | _ -> None in
+
+ let name_of_int_construct_const = function
+ (* XXX As an enhancement we should allow a 64-bit-only
+ * mode which lets us use 'int' up to 63 bits and won't
+ * compile on 32-bit platforms.
+ *)
+ (* XXX The meaning of signed/unsigned breaks down at
+ * 31, 32, 63 and 64 bits.
+ *)
+ | (1, _, _) -> "construct_bit"
+ | ((2|3|4|5|6|7|8), _, false) -> "construct_char_unsigned"
+ | ((2|3|4|5|6|7|8), _, true) -> "construct_char_signed"
+ | (i, BigEndian, false) when i <= 31 -> "construct_int_be_unsigned"
+ | (i, BigEndian, true) when i <= 31 -> "construct_int_be_signed"
+ | (i, LittleEndian, false) when i <= 31 -> "construct_int_le_unsigned"
+ | (i, LittleEndian, true) when i <= 31 -> "construct_int_le_signed"
+ | (i, NativeEndian, false) when i <= 31 -> "construct_int_ne_unsigned"
+ | (i, NativeEndian, true) when i <= 31 -> "construct_int_ne_signed"
+ | (32, BigEndian, false) -> "construct_int32_be_unsigned"
+ | (32, BigEndian, true) -> "construct_int32_be_signed"
+ | (32, LittleEndian, false) -> "construct_int32_le_unsigned"
+ | (32, LittleEndian, true) -> "construct_int32_le_signed"
+ | (32, NativeEndian, false) -> "construct_int32_ne_unsigned"
+ | (32, NativeEndian, true) -> "construct_int32_ne_signed"
+ | (_, BigEndian, false) -> "construct_int64_be_unsigned"
+ | (_, BigEndian, true) -> "construct_int64_be_signed"
+ | (_, LittleEndian, false) -> "construct_int64_le_unsigned"
+ | (_, LittleEndian, true) -> "construct_int64_le_signed"
+ | (_, NativeEndian, false) -> "construct_int64_ne_unsigned"
+ | (_, NativeEndian, true) -> "construct_int64_ne_signed"
+ in
+ let name_of_int_construct = function
+ (* XXX As an enhancement we should allow users to
+ * specify that a field length can fit into a char/int/int32
+ * (of course, this would have to be checked at runtime).
+ *)
+ | (BigEndian, false) -> "construct_int64_be_unsigned"
+ | (BigEndian, true) -> "construct_int64_be_signed"
+ | (LittleEndian, false) -> "construct_int64_le_unsigned"
+ | (LittleEndian, true) -> "construct_int64_le_signed"
+ | (NativeEndian, false) -> "construct_int64_ne_unsigned"
+ | (NativeEndian, true) -> "construct_int64_ne_signed"
+ in
+
+ let expr =
+ match t, flen_is_const with
+ (* Common case: int field, constant flen.
+ *
+ * Range checks are done inside the construction function
+ * because that's a lot simpler w.r.t. types. It might
+ * be better to move them here. XXX
+ *)
+ | Int, Some i when i > 0 && i <= 64 ->
+ let construct_func =
+ name_of_int_construct_const (i,endian,signed) in
+ exn_used := true;
+
+ <:expr<
+ Bitmatch.$lid:construct_func$ $lid:buffer$ $fval$ $flen$
+ $lid:exn$
+ >>
+
+ | Int, Some _ ->
+ Loc.raise _loc (Failure "length of int field must be [1..64]")
+
+ (* Int field, non-constant length. We need to perform a runtime
+ * test to ensure the length is [1..64].
+ *
+ * Range checks are done inside the construction function
+ * because that's a lot simpler w.r.t. types. It might
+ * be better to move them here. XXX
+ *)
+ | Int, None ->
+ let construct_func = name_of_int_construct (endian,signed) in
+ exn_used := true;
+
+ <:expr<
+ if $flen$ >= 1 && $flen$ <= 64 then
+ Bitmatch.$lid:construct_func$ $lid:buffer$ $fval$ $flen$
+ $lid:exn$
+ else
+ raise (Bitmatch.Construct_failure
+ ("length of int field must be [1..64]",
+ $str:loc_fname$,
+ $int:loc_line$, $int:loc_char$))
+ >>
+
+ (* Bitstring, constant length > 0. *)
+ | Bitstring, Some i when i > 0 ->
+ let bs = gensym "bs" in
+ <:expr<
+ let $lid:bs$ = $fval$ in
+ if Bitmatch.bitstring_length $lid:bs$ = $flen$ then
+ Bitmatch.construct_bitstring $lid:buffer$ $lid:bs$
+ else
+ raise (Bitmatch.Construct_failure
+ ("length of bitstring does not match declaration",
+ $str:loc_fname$,
+ $int:loc_line$, $int:loc_char$))
+ >>
+
+ (* Bitstring, constant length -1, means variable length bitstring
+ * with no checks.
+ *)
+ | Bitstring, Some (-1) ->
+ <:expr< Bitmatch.construct_bitstring $lid:buffer$ $fval$ >>
+
+ (* Bitstring, constant length = 0 is probably an error, and so it
+ * any other value.
+ *)
+ | Bitstring, Some _ ->
+ Loc.raise _loc
+ (Failure
+ "length of bitstring must be > 0 or the special value -1")
+
+ (* Bitstring, non-constant length.
+ * We check at runtime that the length is > 0 and matches
+ * the declared length.
+ *)
+ | Bitstring, None ->
+ let bslen = gensym "bslen" in
+ let bs = gensym "bs" in
+ <:expr<
+ let $lid:bslen$ = $flen$ in
+ if $lid:bslen$ > 0 then (
+ let $lid:bs$ = $fval$ in
+ if Bitmatch.bitstring_length $lid:bs$ = $lid:bslen$ then
+ Bitmatch.construct_bitstring $lid:buffer$ $lid:bs$
+ else
+ raise (Bitmatch.Construct_failure
+ ("length of bitstring does not match declaration",
+ $str:loc_fname$,
+ $int:loc_line$, $int:loc_char$))
+ ) else
+ raise (Bitmatch.Construct_failure
+ ("length of bitstring must be > 0",
+ $str:loc_fname$,
+ $int:loc_line$, $int:loc_char$))
+ >> in
+ expr
+ ) fields in
+
+ (* Create the final bitstring. Start by creating an empty buffer
+ * and then evaluate each expression above in turn which will
+ * append some more to the bitstring buffer. Finally extract
+ * the bitstring.
+ *
+ * XXX We almost have enough information to be able to guess
+ * a good initial size for the buffer.
+ *)
+ let fields =
+ match fields with
+ | [] -> <:expr< [] >>
+ | h::t -> List.fold_left (fun h t -> <:expr< $h$; $t$ >>) h t in
+
+ let expr =
+ <:expr<
+ let $lid:buffer$ = Bitmatch.Buffer.create () in
+ $fields$;
+ Bitmatch.Buffer.contents $lid:buffer$
+ >> in
+
+ if !exn_used then
+ <:expr<
+ let $lid:exn$ =
+ Bitmatch.Construct_failure ("value out of range",
+ $str:loc_fname$,
+ $int:loc_line$, $int:loc_char$) in
+ $expr$
+ >>
+ else
+ expr
+
(* Generate the code for a bitmatch statement. '_loc' is the
* location, 'bs' is the bitstring parameter, 'cases' are
* the list of cases to test against.
*)
let rec output_field_extraction inner = function
| [] -> inner
- | {ident=ident; flen=flen; endian=endian; signed=signed; t=t} :: fields ->
- (* If length an integer constant? If so, what is it? This
+ | field :: fields ->
+ let {fval=fval; flen=flen; endian=endian; signed=signed; t=t}
+ = field in
+
+ (* Is fval a binding (an ident) or an expression? If it's
+ * a binding then we will generate a binding for this field.
+ * If it's an expression then we will test the field against
+ * the expression.
+ *)
+ let fval_is_ident =
+ match fval with
+ | <:expr< $lid:id$ >> -> Some id
+ | _ -> None in
+
+ (* Is flen an integer constant? If so, what is it? This
* is very simple-minded and only detects simple constants.
*)
let flen_is_const =
| _ -> None in
let name_of_int_extract_const = function
+ (* XXX As an enhancement we should allow a 64-bit-only
+ * mode which lets us use 'int' up to 63 bits and won't
+ * compile on 32-bit platforms.
+ *)
+ (* XXX The meaning of signed/unsigned breaks down at
+ * 31, 32, 63 and 64 bits.
+ *)
| (1, _, _) -> "extract_bit"
- | ((2|3|4|5|6|7), _, false) -> "extract_char_unsigned"
- | ((2|3|4|5|6|7), _, true) -> "extract_char_signed"
+ | ((2|3|4|5|6|7|8), _, false) -> "extract_char_unsigned"
+ | ((2|3|4|5|6|7|8), _, true) -> "extract_char_signed"
| (i, BigEndian, false) when i <= 31 -> "extract_int_be_unsigned"
| (i, BigEndian, true) when i <= 31 -> "extract_int_be_signed"
| (i, LittleEndian, false) when i <= 31 -> "extract_int_le_unsigned"
in
let expr =
- match t, flen_is_const with
- (* Common case: int field, constant flen *)
- | Int, Some i when i > 0 && i <= 64 ->
+ match t, fval_is_ident, flen_is_const with
+ (* Common case: int field, binding, constant flen *)
+ | Int, Some ident, Some i when i > 0 && i <= 64 ->
let extract_func = name_of_int_extract_const (i,endian,signed) in
<:expr<
if $lid:len$ >= $flen$ then (
)
>>
- | Int, Some _ ->
+ (* Int field, not a binding, constant flen *)
+ | Int, None, Some i when i > 0 && i <= 64 ->
+ let extract_func = name_of_int_extract_const (i,endian,signed) in
+ let v = gensym "val" in
+ <:expr<
+ if $lid:len$ >= $flen$ then (
+ let $lid:v$, $lid:off$, $lid:len$ =
+ Bitmatch.$lid:extract_func$ $lid:data$ $lid:off$ $lid:len$
+ $flen$ in
+ if $lid:v$ = $fval$ then (
+ $inner$
+ )
+ )
+ >>
+
+ | Int, _, Some _ ->
Loc.raise _loc (Failure "length of int field must be [1..64]")
(* Int field, non-const flen. We have to test the range of
* the field at runtime. If outside the range it's a no-match
* (not an error).
*)
- | Int, None ->
+ | Int, Some ident, None ->
let extract_func = name_of_int_extract (endian,signed) in
<:expr<
- if $flen$ >= 1 && $flen$ <= 64 && $flen$ >= $lid:len$ then (
+ if $flen$ >= 1 && $flen$ <= 64 && $flen$ <= $lid:len$ then (
let $lid:ident$, $lid:off$, $lid:len$ =
Bitmatch.$lid:extract_func$ $lid:data$ $lid:off$ $lid:len$
$flen$ in
)
>>
+ | Int, None, None ->
+ let extract_func = name_of_int_extract (endian,signed) in
+ let v = gensym "val" in
+ <:expr<
+ if $flen$ >= 1 && $flen$ <= 64 && $flen$ <= $lid:len$ then (
+ let $lid:v$, $lid:off$, $lid:len$ =
+ Bitmatch.$lid:extract_func$ $lid:data$ $lid:off$ $lid:len$
+ $flen$ in
+ if $lid:v$ = $fval$ then (
+ $inner$
+ )
+ )
+ >>
+
+ (* Can't compare bitstrings at the moment. *)
+ | Bitstring, None, _ ->
+ Loc.raise _loc
+ (Failure "cannot compare a bitstring to a constant")
+
(* Bitstring, constant flen >= 0. *)
- | Bitstring, Some i when i >= 0 ->
+ | Bitstring, Some ident, Some i when i >= 0 ->
<:expr<
if $lid:len$ >= $flen$ then (
let $lid:ident$, $lid:off$, $lid:len$ =
(* Bitstring, constant flen = -1, means consume all the
* rest of the input.
*)
- | Bitstring, Some i when i = -1 ->
+ | Bitstring, Some ident, Some i when i = -1 ->
<:expr<
let $lid:ident$, $lid:off$, $lid:len$ =
Bitmatch.extract_remainder $lid:data$ $lid:off$ $lid:len$ in
$inner$
>>
- | Bitstring, Some _ ->
+ | Bitstring, _, Some _ ->
Loc.raise _loc (Failure "length of bitstring must be >= 0 or the special value -1")
(* Bitstring field, non-const flen. We check the flen is >= 0
* (-1 is not allowed here) at runtime.
*)
- | Bitstring, None ->
+ | Bitstring, Some ident, None ->
<:expr<
- if $flen$ >= 0 && $lid:len$ >= $flen$ then (
+ if $flen$ >= 0 && $flen$ <= $lid:len$ then (
let $lid:ident$, $lid:off$, $lid:len$ =
Bitmatch.extract_bitstring $lid:data$ $lid:off$ $lid:len$
$flen$ in
>>
in
+ (* Emit extra debugging code. *)
+ let expr =
+ if not debug then expr else (
+ let field = string_of_field field in
+
+ <:expr<
+ if !Bitmatch.debug then (
+ Printf.eprintf "PA_BITMATCH: TEST:\n";
+ Printf.eprintf " %s\n" $str:field$;
+ Printf.eprintf " off %d len %d\n%!" $lid:off$ $lid:len$;
+ (*Bitmatch.hexdump_bitstring stderr
+ ($lid:data$,$lid:off$,$lid:len$);*)
+ );
+ $expr$
+ >>
+ ) in
+
output_field_extraction expr fields
in
) cases in
+ (* Join them into a single expression.
+ *
+ * Don't do it with a normal fold_right because that leaves
+ * 'raise Exit; ()' at the end which causes a compiler warning.
+ * Hence a bit of complexity here.
+ *
+ * Note that the number of cases is always >= 1 so List.hd is safe.
+ *)
+ let cases = List.rev cases in
let cases =
- List.fold_right (fun case base -> <:expr< $case$ ; $base$ >>)
- cases <:expr< () >> in
+ List.fold_left (fun base case -> <:expr< $case$ ; $base$ >>)
+ (List.hd cases) (List.tl cases) in
(* The final code just wraps the list of cases in a
* try/with construct so that each case is tried in
];
field: [
- [ name = LIDENT; ":"; len = expr LEVEL "top";
+ [ fval = expr LEVEL "top"; ":"; len = expr LEVEL "top";
qs = OPT [ ":"; qs = qualifiers -> qs ] ->
- output_field _loc name len qs
+ parse_field _loc fval len qs
]
];
match_case: [
- [ fields = LIST0 field SEP ";";
+ [ "_";
+ bind = OPT [ "as"; name = LIDENT -> name ];
w = OPT [ "when"; e = expr -> e ]; "->";
code = expr ->
- (Fields fields, w, code)
+ (Bind bind, w, code)
]
- | [ "_";
- bind = OPT [ "as"; name = LIDENT -> name ];
+ | [ fields = LIST0 field SEP ";";
w = OPT [ "when"; e = expr -> e ]; "->";
code = expr ->
- (Bind bind, w, code)
+ (Fields fields, w, code)
]
];
+ (* 'bitmatch' expressions. *)
expr: LEVEL ";" [
[ "bitmatch"; bs = expr; "with"; OPT "|";
cases = LIST1 match_case SEP "|" ->
output_bitmatch _loc bs cases
]
+
+ (* Constructor. *)
+ | [ "BITSTRING";
+ fields = LIST0 field SEP ";" ->
+ output_constructor _loc fields
+ ]
];
END
git.annexia.org / ocaml-bitstring.git / blobdiff