Added computed offset field

diff --git a/bitmatch_persistent.ml b/bitmatch_persistent.ml
index 8a2cbdf..41ea0c9 100644 (file)
--- a/bitmatch_persistent.ml
+++ b/bitmatch_persistent.ml
@@ -38,6 +38,7 @@ type 'a field = {
   signed : bool;                       (* true if signed, false if unsigned *)
   t : field_type;                      (* type *)
   _loc : Loc.t;                                (* location in source code *)
+  offset : expr option;                        (* offset expression *)
 
   (* Turn the field into a string.  This used to be a function,
    * but that would prevent this structure from being marshalled.
@@ -158,6 +159,7 @@ let create_pattern_field _loc =
     t = Int;
     _loc = _loc;
     printer = PattPrinter;
+    offset = None;
   }
 
 let set_lident_patt field id =
@@ -184,6 +186,11 @@ let set_type_int field = { field with t = Int }
 let set_type_string field = { field with t = String }
 let set_type_bitstring field = { field with t = Bitstring }
 let set_location field loc = { field with _loc = loc }
+let set_offset_int field i =
+  let _loc = field._loc in
+  { field with offset = Some <:expr< $`int:i$ >> }
+let set_offset field expr = { field with offset = Some expr }
+let set_no_offset field = { field with offset = None }
 
 let create_constructor_field _loc =
   {
@@ -194,6 +201,7 @@ let create_constructor_field _loc =
     t = Int;
     _loc = _loc;
     printer = ExprPrinter;
+    offset = None;
   }
 
 let set_lident_expr field id =
@@ -216,3 +224,4 @@ let get_endian field = field.endian
 let get_signed field = field.signed
 let get_type field = field.t
 let get_location field = field._loc
+let get_offset field = field.offset

diff --git a/bitmatch_persistent.mli b/bitmatch_persistent.mli
index d2057c6..9da0f93 100644 (file)
--- a/bitmatch_persistent.mli
+++ b/bitmatch_persistent.mli
@@ -329,7 +329,7 @@ val create_pattern_field : loc_t -> patt field
 
     The pattern is unbound, the type is set to [int], bit length to [32],
     endianness to [BigEndian], signedness to unsigned ([false]),
-    and source code location to the [_loc] parameter.
+    source code location to the [_loc] parameter, and no offset expression.
 
     To create a complete field you need to call the [set_*]
     functions.  For example, to create [{ len : 8 : int }]
@@ -422,6 +422,23 @@ val set_location : 'a field -> loc_t -> 'a field
 (** Sets the source code location of a field.  This is used when
     pa_bitmatch displays error messages. *)
 
+val set_offset_int : 'a field -> int -> 'a field
+(** Set the offset expression for a field to the given number.
+
+    The effect is that the field [{ _ : 8 : offset(160) }] could
+    be created by calling [set_offset_int field 160]. *)
+
+val set_offset : 'a field -> expr -> 'a field
+(** Set the offset expression for a field to the given expression.
+
+    The effect is that the field [{ _ : 8 : offset(160) }] could
+    be created by calling [set_offset_int field <:expr< 160 >>]. *)
+
+val set_no_offset : 'a field -> 'a field
+(** Remove the offset expression from a field.  The field will
+    follow the previous field, or if it is the first field will
+    be at offset zero. *)
+
 (** {3 Create constructor fields}
 
     These fields are used in constructors ([BITSTRING]). *)
@@ -485,3 +502,6 @@ val get_type : 'a field -> field_type
 
 val get_location : 'a field -> loc_t
 (** Get the source code location of a field. *)
+
+val get_offset : 'a field -> expr option
+(** Get the offset expression of a field, or [None] if there is none. *)