X-Git-Url: http://git.annexia.org/?a=blobdiff_plain;f=pa_bitmatch.ml;h=6ab1c9a482affdf51c46324b92656b95fecce418;hb=2f188daa74d22b8762e1319608155d6ea227d835;hp=83bb5d4988ab5ea539a4dcfa3b6b26825a829a4e;hpb=edd992287c4ee26b6a16d39927649c80ede7f860;p=ocaml-bitstring.git diff --git a/pa_bitmatch.ml b/pa_bitmatch.ml index 83bb5d4..6ab1c9a 100644 --- a/pa_bitmatch.ml +++ b/pa_bitmatch.ml @@ -15,7 +15,7 @@ * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA * - * $Id: pa_bitmatch.ml,v 1.11 2008-04-25 14:57:11 rjones Exp $ + * $Id$ *) open Printf @@ -24,6 +24,9 @@ open Camlp4.PreCast open Syntax open Ast +open Bitmatch +module P = Bitmatch_persistent + (* 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. @@ -32,26 +35,46 @@ open Ast *) let debug = false -(* A field when used in a bitmatch (a pattern). *) -type fpatt = { - fpatt : patt; (* field matching pattern *) - fpc : fcommon; -} -(* A field when used in a BITSTRING constructor (an expression). *) -and fexpr = { - fexpr : expr; (* field value *) - fec : fcommon; -} - -and fcommon = { - 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 | String | Bitstring +(* Hashtable storing named persistent patterns. *) +let pattern_hash : (string, P.pattern) Hashtbl.t = Hashtbl.create 13 + +let locfail _loc msg = Loc.raise _loc (Failure msg) + +(* Work out if an expression is an integer constant. + * + * Returns [Some i] if so (where i is the integer value), else [None]. + * + * Fairly simplistic algorithm: we can only detect simple constant + * expressions such as [k], [k+c], [k-c] etc. + *) +let rec expr_is_constant = function + | <:expr< $int:i$ >> -> (* Literal integer constant. *) + Some (int_of_string i) + | <:expr< $a$ + $b$ >> -> (* Addition of constants. *) + (match expr_is_constant a, expr_is_constant b with + | Some a, Some b -> Some (a+b) + | _ -> None) + | <:expr< $a$ - $b$ >> -> (* Subtraction. *) + (match expr_is_constant a, expr_is_constant b with + | Some a, Some b -> Some (a-b) + | _ -> None) + | <:expr< $a$ * $b$ >> -> (* Multiplication. *) + (match expr_is_constant a, expr_is_constant b with + | Some a, Some b -> Some (a*b) + | _ -> None) + | <:expr< $a$ / $b$ >> -> (* Division. *) + (match expr_is_constant a, expr_is_constant b with + | Some a, Some b -> Some (a/b) + | _ -> None) + | <:expr< $a$ lsl $b$ >> -> (* Shift left. *) + (match expr_is_constant a, expr_is_constant b with + | Some a, Some b -> Some (a lsl b) + | _ -> None) + | <:expr< $a$ lsr $b$ >> -> (* Shift right. *) + (match expr_is_constant a, expr_is_constant b with + | Some a, Some b -> Some (a lsr b) + | _ -> None) + | _ -> None (* Anything else is not constant. *) (* Generate a fresh, unique symbol each time called. *) let gensym = @@ -60,150 +83,112 @@ let gensym = incr i; let i = !i in sprintf "__pabitmatch_%s_%d" name i -let rec parse_patt_field _loc fpatt flen qs = - let fpc = parse_field_common _loc flen qs in - { fpatt = fpatt; fpc = fpc } - -and parse_constr_field _loc fexpr flen qs = - let fec = parse_field_common _loc flen qs in - { fexpr = fexpr; fec = fec } - (* Deal with the qualifiers which appear for a field of both types. *) -and parse_field_common _loc flen qs = - let endian, signed, t = +let parse_field _loc field qs = + let fail = locfail _loc in + + let endian_set, signed_set, type_set, offset_set, field = match qs with - | None -> (None, None, None) + | None -> (false, false, false, false, field) | Some qs -> List.fold_left ( - fun (endian, signed, t) q -> - match q with - | "bigendian" -> - if endian <> None then - Loc.raise _loc (Failure "an endian flag has been set already") + fun (endian_set, signed_set, type_set, offset_set, field) qual_expr -> + match qual_expr with + | "bigendian", None -> + if endian_set then + fail "an endian flag has been set already" else ( - let endian = Some BigEndian in - (endian, signed, t) + let field = P.set_endian field BigEndian in + (true, signed_set, type_set, offset_set, field) ) - | "littleendian" -> - if endian <> None then - Loc.raise _loc (Failure "an endian flag has been set already") + | "littleendian", None -> + if endian_set then + fail "an endian flag has been set already" else ( - let endian = Some LittleEndian in - (endian, signed, t) + let field = P.set_endian field LittleEndian in + (true, signed_set, type_set, offset_set, field) ) - | "nativeendian" -> - if endian <> None then - Loc.raise _loc (Failure "an endian flag has been set already") + | "nativeendian", None -> + if endian_set then + fail "an endian flag has been set already" else ( - let endian = Some NativeEndian in - (endian, signed, t) + let field = P.set_endian field NativeEndian in + (true, signed_set, type_set, offset_set, field) ) - | "signed" -> - if signed <> None then - Loc.raise _loc (Failure "a signed flag has been set already") + | "endian", Some expr -> + if endian_set then + fail "an endian flag has been set already" else ( - let signed = Some true in - (endian, signed, t) + let field = P.set_endian_expr field expr in + (true, signed_set, type_set, offset_set, field) ) - | "unsigned" -> - if signed <> None then - Loc.raise _loc (Failure "a signed flag has been set already") + | "signed", None -> + if signed_set then + fail "a signed flag has been set already" else ( - let signed = Some false in - (endian, signed, t) + let field = P.set_signed field true in + (endian_set, true, type_set, offset_set, field) ) - | "int" -> - if t <> None then - Loc.raise _loc (Failure "a type flag has been set already") + | "unsigned", None -> + if signed_set then + fail "a signed flag has been set already" else ( - let t = Some Int in - (endian, signed, t) + let field = P.set_signed field false in + (endian_set, true, type_set, offset_set, field) ) - | "string" -> - if t <> None then - Loc.raise _loc (Failure "a type flag has been set already") + | "int", None -> + if type_set then + fail "a type flag has been set already" else ( - let t = Some String in - (endian, signed, t) + let field = P.set_type_int field in + (endian_set, signed_set, true, offset_set, field) ) - | "bitstring" -> - if t <> None then - Loc.raise _loc (Failure "a type flag has been set already") + | "string", None -> + if type_set then + fail "a type flag has been set already" else ( - let t = Some Bitstring in - (endian, signed, t) + let field = P.set_type_string field in + (endian_set, signed_set, true, offset_set, field) ) - | s -> - Loc.raise _loc (Failure (s ^ ": unknown qualifier")) - ) (None, None, None) qs in + | "bitstring", None -> + if type_set then + fail "a type flag has been set already" + else ( + let field = P.set_type_bitstring field in + (endian_set, signed_set, true, offset_set, field) + ) + | "offset", Some expr -> + if offset_set then + fail "an offset has been set already" + else ( + let field = P.set_offset field expr in + (endian_set, signed_set, type_set, true, field) + ) + | s, Some _ -> + fail (s ^ ": unknown qualifier, or qualifier should not be followed by an expression") + | s, None -> + fail (s ^ ": unknown qualifier, or qualifier should be followed by an expression") + ) (false, false, false, false, field) qs in (* If type is set to string or bitstring then endianness and * signedness qualifiers are meaningless and must not be set. *) - if (t = Some Bitstring || t = Some String) - && (endian <> None || signed <> None) then - Loc.raise _loc ( - Failure "string types and endian or signed qualifiers cannot be mixed" - ); - - (* Default endianness, signedness, type. *) - let endian = match endian with None -> BigEndian | Some e -> e in - let signed = match signed with None -> false | Some s -> s in - let t = match t with None -> Int | Some t -> t in - - { - 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" - | String -> "string" - | Bitstring -> "bitstring" - -let rec string_of_patt_field { fpatt = fpatt; fpc = fpc } = - let fpc = string_of_field_common fpc in - let fpatt = - match fpatt with - | <:patt< $lid:id$ >> -> id - | _ -> "[pattern]" in - fpatt ^ " : " ^ fpc - -and string_of_constr_field { fexpr = fexpr; fec = fec } = - let fec = string_of_field_common fec in - let fexpr = - match fexpr with - | <:expr< $lid:id$ >> -> id - | _ -> "[expression]" in - fexpr ^ " : " ^ fec - -and string_of_field_common { flen = flen; - endian = endian; signed = signed; t = t; - _loc = _loc } = - 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 + let () = + let t = P.get_type field in + if (t = P.Bitstring || t = P.String) && (endian_set || signed_set) then + fail "string types and endian or signed qualifiers cannot be mixed" in + + (* Default endianness, signedness, type if not set already. *) + let field = if endian_set then field else P.set_endian field BigEndian in + let field = if signed_set then field else P.set_signed field false in + let field = if type_set then field else P.set_type_int field in - sprintf "%s : %s, %s, %s @ (%S, %d, %d)" - flen t endian signed loc_fname loc_line loc_char + field (* Generate the code for a constructor, ie. 'BITSTRING ...'. *) let output_constructor _loc fields = + let fail = locfail _loc in + 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 @@ -222,57 +207,107 @@ let output_constructor _loc fields = (* Convert each field to a simple bitstring-generating expression. *) let fields = List.map ( - fun {fexpr=fexpr; fec={flen=flen; endian=endian; signed=signed; - t=t; _loc=_loc}} -> + fun field -> + let fexpr = P.get_expr field in + let flen = P.get_length field in + let endian = P.get_endian field in + let signed = P.get_signed field in + let t = P.get_type field in + let _loc = P.get_location field in + let offset = P.get_offset field in + + (* offset() not supported in constructors. Implementation of + * forward-only offsets is fairly straightforward: we would + * need to just calculate the length of padding here and add + * it to what has been constructed. For general offsets, + * including going backwards, that would require a rethink in + * how we construct bitstrings. + *) + if offset <> None then + fail "offset expressions are not supported in BITSTRING constructors"; + (* 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. - *) + let flen_is_const = expr_is_constant flen in + + (* Choose the right constructor function. *) + let int_construct_const = function (* 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" + | (1, _, _) -> + <:expr> + | ((2|3|4|5|6|7|8), _, false) -> + <:expr> + | ((2|3|4|5|6|7|8), _, true) -> + <:expr> + | (i, P.ConstantEndian BigEndian, false) when i <= 31 -> + <:expr> + | (i, P.ConstantEndian BigEndian, true) when i <= 31 -> + <:expr> + | (i, P.ConstantEndian LittleEndian, false) when i <= 31 -> + <:expr> + | (i, P.ConstantEndian LittleEndian, true) when i <= 31 -> + <:expr> + | (i, P.ConstantEndian NativeEndian, false) when i <= 31 -> + <:expr> + | (i, P.ConstantEndian NativeEndian, true) when i <= 31 -> + <:expr> + | (i, P.EndianExpr expr, false) when i <= 31 -> + <:expr> + | (i, P.EndianExpr expr, true) when i <= 31 -> + <:expr> + | (32, P.ConstantEndian BigEndian, false) -> + <:expr> + | (32, P.ConstantEndian BigEndian, true) -> + <:expr> + | (32, P.ConstantEndian LittleEndian, false) -> + <:expr> + | (32, P.ConstantEndian LittleEndian, true) -> + <:expr> + | (32, P.ConstantEndian NativeEndian, false) -> + <:expr> + | (32, P.ConstantEndian NativeEndian, true) -> + <:expr> + | (32, P.EndianExpr expr, false) -> + <:expr> + | (32, P.EndianExpr expr, true) -> + <:expr> + | (_, P.ConstantEndian BigEndian, false) -> + <:expr> + | (_, P.ConstantEndian BigEndian, true) -> + <:expr> + | (_, P.ConstantEndian LittleEndian, false) -> + <:expr> + | (_, P.ConstantEndian LittleEndian, true) -> + <:expr> + | (_, P.ConstantEndian NativeEndian, false) -> + <:expr> + | (_, P.ConstantEndian NativeEndian, true) -> + <:expr> + | (_, P.EndianExpr expr, false) -> + <:expr> + | (_, P.EndianExpr expr, true) -> + <:expr> 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" + let int_construct = function + | (P.ConstantEndian BigEndian, false) -> + <:expr> + | (P.ConstantEndian BigEndian, true) -> + <:expr> + | (P.ConstantEndian LittleEndian, false) -> + <:expr> + | (P.ConstantEndian LittleEndian, true) -> + <:expr> + | (P.ConstantEndian NativeEndian, false) -> + <:expr> + | (P.ConstantEndian NativeEndian, true) -> + <:expr> + | (P.EndianExpr expr, false) -> + <:expr> + | (P.EndianExpr expr, true) -> + <:expr> in let expr = @@ -283,18 +318,16 @@ let output_constructor _loc fields = * 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 + | P.Int, Some i when i > 0 && i <= 64 -> + let construct_fn = int_construct_const (i,endian,signed) in exn_used := true; <:expr< - Bitmatch.$lid:construct_func$ $lid:buffer$ $fexpr$ $flen$ - $lid:exn$ + $construct_fn$ $lid:buffer$ $fexpr$ $`int:i$ $lid:exn$ >> - | Int, Some _ -> - Loc.raise _loc (Failure "length of int field must be [1..64]") + | P.Int, Some _ -> + fail "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]. @@ -303,14 +336,13 @@ let output_constructor _loc fields = * 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 + | P.Int, None -> + let construct_fn = int_construct (endian,signed) in exn_used := true; <:expr< if $flen$ >= 1 && $flen$ <= 64 then - Bitmatch.$lid:construct_func$ $lid:buffer$ $fexpr$ $flen$ - $lid:exn$ + $construct_fn$ $lid:buffer$ $fexpr$ $flen$ $lid:exn$ else raise (Bitmatch.Construct_failure ("length of int field must be [1..64]", @@ -319,11 +351,12 @@ let output_constructor _loc fields = >> (* String, constant length > 0, must be a multiple of 8. *) - | String, Some i when i > 0 && i land 7 = 0 -> + | P.String, Some i when i > 0 && i land 7 = 0 -> let bs = gensym "bs" in + let j = i lsr 3 in <:expr< let $lid:bs$ = $fexpr$ in - if String.length $lid:bs$ = ($flen$ lsr 3) then + if String.length $lid:bs$ = $`int:j$ then Bitmatch.construct_string $lid:buffer$ $lid:bs$ else raise (Bitmatch.Construct_failure @@ -335,20 +368,20 @@ let output_constructor _loc fields = (* String, constant length -1, means variable length string * with no checks. *) - | String, Some (-1) -> + | P.String, Some (-1) -> <:expr< Bitmatch.construct_string $lid:buffer$ $fexpr$ >> (* String, constant length = 0 is probably an error, and so is * any other value. *) - | String, Some _ -> - Loc.raise _loc (Failure "length of string must be > 0 and a multiple of 8, or the special value -1") + | P.String, Some _ -> + fail "length of string must be > 0 and a multiple of 8, or the special value -1" (* String, non-constant length. * We check at runtime that the length is > 0, a multiple of 8, * and matches the declared length. *) - | String, None -> + | P.String, None -> let bslen = gensym "bslen" in let bs = gensym "bs" in <:expr< @@ -375,12 +408,12 @@ let output_constructor _loc fields = $int:loc_line$, $int:loc_char$)) >> - (* Bitstring, constant length > 0. *) - | Bitstring, Some i when i > 0 -> + (* Bitstring, constant length >= 0. *) + | P.Bitstring, Some i when i >= 0 -> let bs = gensym "bs" in <:expr< let $lid:bs$ = $fexpr$ in - if Bitmatch.bitstring_length $lid:bs$ = $flen$ then + if Bitmatch.bitstring_length $lid:bs$ = $`int:i$ then Bitmatch.construct_bitstring $lid:buffer$ $lid:bs$ else raise (Bitmatch.Construct_failure @@ -392,27 +425,23 @@ let output_constructor _loc fields = (* Bitstring, constant length -1, means variable length bitstring * with no checks. *) - | Bitstring, Some (-1) -> + | P.Bitstring, Some (-1) -> <:expr< Bitmatch.construct_bitstring $lid:buffer$ $fexpr$ >> - (* Bitstring, constant length = 0 is probably an error, and so is - * any other value. - *) - | Bitstring, Some _ -> - Loc.raise _loc - (Failure - "length of bitstring must be > 0 or the special value -1") + (* Bitstring, constant length < -1 is an error. *) + | P.Bitstring, Some _ -> + fail "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 + * We check at runtime that the length is >= 0 and matches * the declared length. *) - | Bitstring, None -> + | P.Bitstring, None -> let bslen = gensym "bslen" in let bs = gensym "bs" in <:expr< let $lid:bslen$ = $flen$ in - if $lid:bslen$ > 0 then ( + if $lid:bslen$ >= 0 then ( let $lid:bs$ = $fexpr$ in if Bitmatch.bitstring_length $lid:bs$ = $lid:bslen$ then Bitmatch.construct_bitstring $lid:buffer$ $lid:bs$ @@ -466,13 +495,15 @@ let output_constructor _loc fields = * the list of cases to test against. *) let output_bitmatch _loc bs cases = + let fail = locfail _loc in + let data = gensym "data" and off = gensym "off" and len = gensym "len" in let result = gensym "result" in (* This generates the field extraction code for each - * field a single case. Each field must be wider than - * the minimum permitted for the type and there must be - * enough remaining data in the bitstring to satisfy it. + * field in a single case. There must be enough remaining data + * in the bitstring to satisfy the field. + * * As we go through the fields, symbols 'data', 'off' and 'len' * track our position and remaining length in the bitstring. * @@ -482,103 +513,138 @@ let output_bitmatch _loc bs cases = let rec output_field_extraction inner = function | [] -> inner | field :: fields -> - let {fpatt=fpatt; fpc={flen=flen; endian=endian; signed=signed; - t=t; _loc=_loc}} - = field in - - (* Is flen an integer constant? If so, what is it? This - * is very simple-minded and only detects simple constants. + let fpatt = P.get_patt field in + let flen = P.get_length field in + let endian = P.get_endian field in + let signed = P.get_signed field in + let t = P.get_type field in + let _loc = P.get_location field in + let offset = P.get_offset field in + + (* Is flen (field len) an integer constant? If so, what is it? + * This will be [Some i] if it's a constant or [None] if it's + * non-constant or we couldn't determine. *) - let flen_is_const = - match flen with - | <:expr< $int:i$ >> -> Some (int_of_string i) - | _ -> 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. - *) + let flen_is_const = expr_is_constant flen in + + let int_extract_const = function (* XXX The meaning of signed/unsigned breaks down at * 31, 32, 63 and 64 bits. *) - | (1, _, _) -> "extract_bit" - | ((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" - | (i, LittleEndian, true) when i <= 31 -> "extract_int_le_signed" - | (i, NativeEndian, false) when i <= 31 -> "extract_int_ne_unsigned" - | (i, NativeEndian, true) when i <= 31 -> "extract_int_ne_signed" - | (32, BigEndian, false) -> "extract_int32_be_unsigned" - | (32, BigEndian, true) -> "extract_int32_be_signed" - | (32, LittleEndian, false) -> "extract_int32_le_unsigned" - | (32, LittleEndian, true) -> "extract_int32_le_signed" - | (32, NativeEndian, false) -> "extract_int32_ne_unsigned" - | (32, NativeEndian, true) -> "extract_int32_ne_signed" - | (_, BigEndian, false) -> "extract_int64_be_unsigned" - | (_, BigEndian, true) -> "extract_int64_be_signed" - | (_, LittleEndian, false) -> "extract_int64_le_unsigned" - | (_, LittleEndian, true) -> "extract_int64_le_signed" - | (_, NativeEndian, false) -> "extract_int64_ne_unsigned" - | (_, NativeEndian, true) -> "extract_int64_ne_signed" + | (1, _, _) -> + <:expr> + | ((2|3|4|5|6|7|8), _, false) -> + <:expr> + | ((2|3|4|5|6|7|8), _, true) -> + <:expr> + | (i, P.ConstantEndian BigEndian, false) when i <= 31 -> + <:expr> + | (i, P.ConstantEndian BigEndian, true) when i <= 31 -> + <:expr> + | (i, P.ConstantEndian LittleEndian, false) when i <= 31 -> + <:expr> + | (i, P.ConstantEndian LittleEndian, true) when i <= 31 -> + <:expr> + | (i, P.ConstantEndian NativeEndian, false) when i <= 31 -> + <:expr> + | (i, P.ConstantEndian NativeEndian, true) when i <= 31 -> + <:expr> + | (i, P.EndianExpr expr, false) when i <= 31 -> + <:expr> + | (i, P.EndianExpr expr, true) when i <= 31 -> + <:expr> + | (32, P.ConstantEndian BigEndian, false) -> + <:expr> + | (32, P.ConstantEndian BigEndian, true) -> + <:expr> + | (32, P.ConstantEndian LittleEndian, false) -> + <:expr> + | (32, P.ConstantEndian LittleEndian, true) -> + <:expr> + | (32, P.ConstantEndian NativeEndian, false) -> + <:expr> + | (32, P.ConstantEndian NativeEndian, true) -> + <:expr> + | (32, P.EndianExpr expr, false) -> + <:expr> + | (32, P.EndianExpr expr, true) -> + <:expr> + | (_, P.ConstantEndian BigEndian, false) -> + <:expr> + | (_, P.ConstantEndian BigEndian, true) -> + <:expr> + | (_, P.ConstantEndian LittleEndian, false) -> + <:expr> + | (_, P.ConstantEndian LittleEndian, true) -> + <:expr> + | (_, P.ConstantEndian NativeEndian, false) -> + <:expr> + | (_, P.ConstantEndian NativeEndian, true) -> + <:expr> + | (_, P.EndianExpr expr, false) -> + <:expr> + | (_, P.EndianExpr expr, true) -> + <:expr> in - let name_of_int_extract = 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) -> "extract_int64_be_unsigned" - | (BigEndian, true) -> "extract_int64_be_signed" - | (LittleEndian, false) -> "extract_int64_le_unsigned" - | (LittleEndian, true) -> "extract_int64_le_signed" - | (NativeEndian, false) -> "extract_int64_ne_unsigned" - | (NativeEndian, true) -> "extract_int64_ne_signed" + let int_extract = function + | (P.ConstantEndian BigEndian, false) -> + <:expr> + | (P.ConstantEndian BigEndian, true) -> + <:expr> + | (P.ConstantEndian LittleEndian, false) -> + <:expr> + | (P.ConstantEndian LittleEndian, true) -> + <:expr> + | (P.ConstantEndian NativeEndian, false) -> + <:expr> + | (P.ConstantEndian NativeEndian, true) -> + <:expr> + | (P.EndianExpr expr, false) -> + <:expr> + | (P.EndianExpr expr, true) -> + <:expr> in let expr = match t, flen_is_const with (* Common case: int field, constant flen *) - | Int, Some i when i > 0 && i <= 64 -> - let extract_func = name_of_int_extract_const (i,endian,signed) in + | P.Int, Some i when i > 0 && i <= 64 -> + let extract_fn = int_extract_const (i,endian,signed) in let v = gensym "val" in <:expr< - if $lid:len$ >= $flen$ then ( + if $lid:len$ >= $`int:i$ then ( let $lid:v$, $lid:off$, $lid:len$ = - Bitmatch.$lid:extract_func$ $lid:data$ $lid:off$ $lid:len$ - $flen$ in + $extract_fn$ $lid:data$ $lid:off$ $lid:len$ $`int:i$ in match $lid:v$ with $fpatt$ when true -> $inner$ | _ -> () ) >> - | Int, Some _ -> - Loc.raise _loc (Failure "length of int field must be [1..64]") + | P.Int, Some _ -> + fail "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 -> - let extract_func = name_of_int_extract (endian,signed) in + | P.Int, None -> + let extract_fn = 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 + $extract_fn$ $lid:data$ $lid:off$ $lid:len$ $flen$ in match $lid:v$ with $fpatt$ when true -> $inner$ | _ -> () ) >> (* String, constant flen > 0. *) - | String, Some i when i > 0 && i land 7 = 0 -> + | P.String, Some i when i > 0 && i land 7 = 0 -> let bs = gensym "bs" in <:expr< - if $lid:len$ >= $flen$ then ( + if $lid:len$ >= $`int:i$ then ( let $lid:bs$, $lid:off$, $lid:len$ = Bitmatch.extract_bitstring $lid:data$ $lid:off$ $lid:len$ - $flen$ in + $`int:i$ in match Bitmatch.string_of_bitstring $lid:bs$ with | $fpatt$ when true -> $inner$ | _ -> () @@ -588,7 +654,7 @@ let output_bitmatch _loc bs cases = (* String, constant flen = -1, means consume all the * rest of the input. *) - | String, Some i when i = -1 -> + | P.String, Some i when i = -1 -> let bs = gensym "bs" in <:expr< let $lid:bs$, $lid:off$, $lid:len$ = @@ -598,13 +664,13 @@ let output_bitmatch _loc bs cases = | _ -> () >> - | String, Some _ -> - Loc.raise _loc (Failure "length of string must be > 0 and a multiple of 8, or the special value -1") + | P.String, Some _ -> + fail "length of string must be > 0 and a multiple of 8, or the special value -1" (* String field, non-const flen. We check the flen is > 0 * and a multiple of 8 (-1 is not allowed here), at runtime. *) - | String, None -> + | P.String, None -> let bs = gensym "bs" in <:expr< if $flen$ >= 0 && $flen$ <= $lid:len$ @@ -622,19 +688,18 @@ let output_bitmatch _loc bs cases = * At the moment all we can do is assign the bitstring to an * identifier. *) - | Bitstring, Some i when i >= 0 -> + | P.Bitstring, Some i when i >= 0 -> let ident = match fpatt with | <:patt< $lid:ident$ >> -> ident | <:patt< _ >> -> "_" | _ -> - Loc.raise _loc - (Failure "cannot compare a bitstring to a constant") in + fail "cannot compare a bitstring to a constant" in <:expr< - if $lid:len$ >= $flen$ then ( + if $lid:len$ >= $`int:i$ then ( let $lid:ident$, $lid:off$, $lid:len$ = Bitmatch.extract_bitstring $lid:data$ $lid:off$ $lid:len$ - $flen$ in + $`int:i$ in $inner$ ) >> @@ -642,32 +707,32 @@ let output_bitmatch _loc bs cases = (* Bitstring, constant flen = -1, means consume all the * rest of the input. *) - | Bitstring, Some i when i = -1 -> + | P.Bitstring, Some i when i = -1 -> let ident = match fpatt with | <:patt< $lid:ident$ >> -> ident + | <:patt< _ >> -> "_" | _ -> - Loc.raise _loc - (Failure "cannot compare a bitstring to a constant") in + fail "cannot compare a bitstring to a constant" in <:expr< let $lid:ident$, $lid:off$, $lid:len$ = Bitmatch.extract_remainder $lid:data$ $lid:off$ $lid:len$ in $inner$ >> - | Bitstring, Some _ -> - Loc.raise _loc (Failure "length of bitstring must be >= 0 or the special value -1") + | P.Bitstring, Some _ -> + fail "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 -> + | P.Bitstring, None -> let ident = match fpatt with | <:patt< $lid:ident$ >> -> ident + | <:patt< _ >> -> "_" | _ -> - Loc.raise _loc - (Failure "cannot compare a bitstring to a constant") in + fail "cannot compare a bitstring to a constant" in <:expr< if $flen$ >= 0 && $flen$ <= $lid:len$ then ( let $lid:ident$, $lid:off$, $lid:len$ = @@ -678,10 +743,124 @@ let output_bitmatch _loc bs cases = >> in + (* Computed offset: only offsets forward are supported. + * + * We try hard to optimize this based on what we know. Are + * we at a predictable offset now? (Look at the outer 'fields' + * list and see if they all have constant field length starting + * at some constant offset). Is this offset constant? + * + * Based on this we can do a lot of the computation at + * compile time, or defer it to runtime only if necessary. + * + * In all cases, the off and len fields get updated. + *) + let expr = + match offset with + | None -> expr (* common case: there was no offset expression *) + | Some offset_expr -> + (* This will be [Some i] if offset is a constant expression + * or [None] if it's a non-constant. + *) + let requested_offset = expr_is_constant offset_expr in + + (* This will be [Some i] if our current offset is known + * at compile time, or [None] if we can't determine it. + *) + let current_offset = + let has_constant_offset field = + match P.get_offset field with + | None -> false + | Some expr -> + match expr_is_constant expr with + | None -> false + | Some i -> true + in + let get_constant_offset field = + match P.get_offset field with + | None -> assert false + | Some expr -> + match expr_is_constant expr with + | None -> assert false + | Some i -> i + in + + let has_constant_len field = + match expr_is_constant (P.get_length field) with + | None -> false + | Some i when i > 0 -> true + | Some _ -> false + in + let get_constant_len field = + match expr_is_constant (P.get_length field) with + | None -> assert false + | Some i when i > 0 -> i + | Some _ -> assert false + in + + let rec loop = function + (* first field has constant offset 0 *) + | [] -> Some 0 + (* field with constant offset & length *) + | field :: _ + when has_constant_offset field && + has_constant_len field -> + Some (get_constant_offset field + get_constant_len field) + (* field with no offset & constant length *) + | field :: fields + when P.get_offset field = None && + has_constant_len field -> + (match loop fields with + | None -> None + | Some offset -> Some (offset + get_constant_len field)) + (* else, can't work out the offset *) + | _ -> None + in + loop fields in + + (* Look at the current offset and requested offset cases and + * determine what code to generate. + *) + match current_offset, requested_offset with + (* This is the good case: both the current offset and + * the requested offset are constant, so we can remove + * almost all the runtime checks. + *) + | Some current_offset, Some requested_offset -> + let move = requested_offset - current_offset in + if move < 0 then + fail (sprintf "requested offset is less than the current offset (%d < %d)" requested_offset current_offset); + (* Add some code to move the offset and length by a + * constant amount, and a runtime test that len >= 0 + * (XXX possibly the runtime test is unnecessary?) + *) + <:expr< + let $lid:off$ = $lid:off$ + $`int:move$ in + let $lid:len$ = $lid:len$ - $`int:move$ in + if $lid:len$ >= 0 then $expr$ + >> + (* In any other case, we need to use runtime checks. + * + * XXX It's not clear if a backwards move detected at runtime + * is merely a match failure, or a runtime error. At the + * moment it's just a match failure since bitmatch generally + * doesn't raise runtime errors. + *) + | _ -> + let move = gensym "move" in + <:expr< + let $lid:move$ = $offset_expr$ - $lid:off$ in + if $lid:move$ >= 0 then ( + let $lid:off$ = $lid:off$ + $lid:move$ in + let $lid:len$ = $lid:len$ - $lid:move$ in + if $lid:len$ >= 0 then $expr$ + ) + >> in (* end of computed offset code *) + (* Emit extra debugging code. *) let expr = if not debug then expr else ( - let field = string_of_patt_field field in + let field = P.string_of_pattern_field field in <:expr< if !Bitmatch.debug then ( @@ -755,26 +934,90 @@ let output_bitmatch _loc bs cases = $int:loc_line$, $int:loc_char$)) >> +(* Add a named pattern. *) +let add_named_pattern _loc name pattern = + Hashtbl.add pattern_hash name pattern + +(* Expand a named pattern from the pattern_hash. *) +let expand_named_pattern _loc name = + try Hashtbl.find pattern_hash name + with Not_found -> + locfail _loc (sprintf "named pattern not found: %s" name) + +(* Add named patterns from a file. See the documentation on the + * directory search path in bitmatch_persistent.mli + *) +let load_patterns_from_file _loc filename = + let chan = + if Filename.is_relative filename && Filename.is_implicit filename then ( + (* Try current directory. *) + try open_in filename + with _ -> + (* Try OCaml library directory. *) + try open_in (Filename.concat Bitmatch_config.ocamllibdir filename) + with exn -> Loc.raise _loc exn + ) else ( + try open_in filename + with exn -> Loc.raise _loc exn + ) in + let names = ref [] in + (try + let rec loop () = + let name = P.named_from_channel chan in + names := name :: !names + in + loop () + with End_of_file -> () + ); + close_in chan; + let names = List.rev !names in + List.iter ( + function + | name, P.Pattern patt -> add_named_pattern _loc name patt + | _, P.Constructor _ -> () (* just ignore these for now *) + ) names + EXTEND Gram - GLOBAL: expr; + GLOBAL: expr str_item; + (* Qualifiers are a list of identifiers ("string", "bigendian", etc.) + * followed by an optional expression (used in certain cases). Note + * that we are careful not to declare any explicit reserved words. + *) qualifiers: [ - [ LIST0 [ q = LIDENT -> q ] SEP "," ] + [ LIST0 + [ q = LIDENT; + e = OPT [ "("; e = expr; ")" -> e ] -> (q, e) ] + SEP "," ] ]; - (* Field used in the bitmatch operator (a pattern). *) + (* Field used in the bitmatch operator (a pattern). This can actually + * return multiple fields, in the case where the 'field' is a named + * persitent pattern. + *) patt_field: [ [ fpatt = patt; ":"; len = expr LEVEL "top"; qs = OPT [ ":"; qs = qualifiers -> qs ] -> - parse_patt_field _loc fpatt len qs + let field = P.create_pattern_field _loc in + let field = P.set_patt field fpatt in + let field = P.set_length field len in + [parse_field _loc field qs] (* Normal, single field. *) + | ":"; name = LIDENT -> + expand_named_pattern _loc name (* Named -> list of fields. *) ] ]; (* Case inside bitmatch operator. *) - match_case: [ + patt_fields: [ [ "{"; fields = LIST0 patt_field SEP ";"; - "}"; + "}" -> + List.concat fields + ] + ]; + + patt_case: [ + [ fields = patt_fields; bind = OPT [ "as"; name = LIDENT -> name ]; whenclause = OPT [ "when"; e = expr -> e ]; "->"; code = expr -> @@ -786,7 +1029,18 @@ EXTEND Gram constr_field: [ [ fexpr = expr LEVEL "top"; ":"; len = expr LEVEL "top"; qs = OPT [ ":"; qs = qualifiers -> qs ] -> - parse_constr_field _loc fexpr len qs + let field = P.create_constructor_field _loc in + let field = P.set_expr field fexpr in + let field = P.set_length field len in + parse_field _loc field qs + ] + ]; + + constr_fields: [ + [ "{"; + fields = LIST0 constr_field SEP ";"; + "}" -> + fields ] ]; @@ -794,16 +1048,34 @@ EXTEND Gram expr: LEVEL ";" [ [ "bitmatch"; bs = expr; "with"; OPT "|"; - cases = LIST1 match_case SEP "|" -> + cases = LIST1 patt_case SEP "|" -> output_bitmatch _loc bs cases ] (* Constructor. *) - | [ "BITSTRING"; "{"; - fields = LIST0 constr_field SEP ";"; - "}" -> + | [ "BITSTRING"; + fields = constr_fields -> output_constructor _loc fields ] ]; + (* Named persistent patterns. + * + * NB: Currently only allowed at the top level. We can probably lift + * this restriction later if necessary. We only deal with patterns + * at the moment, not constructors, but the infrastructure to do + * constructors is in place. + *) + str_item: LEVEL "top" [ + [ "let"; "bitmatch"; + name = LIDENT; "="; fields = patt_fields -> + add_named_pattern _loc name fields; + (* The statement disappears, but we still need a str_item so ... *) + <:str_item< >> + | "open"; "bitmatch"; filename = STRING -> + load_patterns_from_file _loc filename; + <:str_item< >> + ] + ]; + END