More complete handling of constant field length expressions.

[ocaml-bitstring.git] / bitmatch.ml

diff --git a/bitmatch.ml b/bitmatch.ml
index 1b98c57..39d7743 100644 (file)
--- a/bitmatch.ml
+++ b/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: bitmatch.ml,v 1.10 2008-04-26 20:35:02 rjones Exp $
+ * $Id: bitmatch.ml,v 1.14 2008-05-12 20:32:55 rjones Exp $
  *)
 
 open Printf
@@ -480,6 +480,9 @@ let _make_int64_be c0 c1 c2 c3 c4 c5 c6 c7 =
        (Int64.shift_left c6 8))
     c7
 
+let _make_int64_le c0 c1 c2 c3 c4 c5 c6 c7 =
+  _make_int64_be c7 c6 c5 c4 c3 c2 c1 c0
+
 (* Extract [1..64] bits.  We have to consider endianness and signedness. *)
 let extract_int64_be_unsigned data off len flen =
   let byteoff = off lsr 3 in
@@ -524,6 +527,49 @@ let extract_int64_be_unsigned data off len flen =
     ) in
   word, off+flen, len-flen
 
+let extract_int64_le_unsigned data off len flen =
+  let byteoff = off lsr 3 in
+
+  let strlen = String.length data in
+
+  let word =
+    (* Optimize the common (byte-aligned) case. *)
+    if off land 7 = 0 then (
+      let word =
+       let c0 = _get_byte64 data byteoff strlen in
+       let c1 = _get_byte64 data (byteoff+1) strlen in
+       let c2 = _get_byte64 data (byteoff+2) strlen in
+       let c3 = _get_byte64 data (byteoff+3) strlen in
+       let c4 = _get_byte64 data (byteoff+4) strlen in
+       let c5 = _get_byte64 data (byteoff+5) strlen in
+       let c6 = _get_byte64 data (byteoff+6) strlen in
+       let c7 = _get_byte64 data (byteoff+7) strlen in
+       _make_int64_le c0 c1 c2 c3 c4 c5 c6 c7 in
+      Int64.logand word (I64.mask flen)
+    ) else (
+      (* Extract the next 64 bits, slow method. *)
+      let word =
+       let c0, off, len = extract_char_unsigned data off len 8 in
+       let c1, off, len = extract_char_unsigned data off len 8 in
+       let c2, off, len = extract_char_unsigned data off len 8 in
+       let c3, off, len = extract_char_unsigned data off len 8 in
+       let c4, off, len = extract_char_unsigned data off len 8 in
+       let c5, off, len = extract_char_unsigned data off len 8 in
+       let c6, off, len = extract_char_unsigned data off len 8 in
+       let c7, _, _ = extract_char_unsigned data off len 8 in
+       let c0 = Int64.of_int c0 in
+       let c1 = Int64.of_int c1 in
+       let c2 = Int64.of_int c2 in
+       let c3 = Int64.of_int c3 in
+       let c4 = Int64.of_int c4 in
+       let c5 = Int64.of_int c5 in
+       let c6 = Int64.of_int c6 in
+       let c7 = Int64.of_int c7 in
+       _make_int64_le c0 c1 c2 c3 c4 c5 c6 c7 in
+      Int64.logand word (I64.mask flen)
+    ) in
+  word, off+flen, len-flen
+
 (*----------------------------------------------------------------------*)
 (* Constructor functions. *)
 
@@ -624,7 +670,7 @@ module Buffer = struct
 end
 
 (* Construct a single bit. *)
-let construct_bit buf b _ =
+let construct_bit buf b _ _ =
   Buffer.add_bit buf b
 
 (* Construct a field, flen = [2..8]. *)
@@ -643,6 +689,17 @@ let construct_int_be_unsigned buf v flen exn =
   (* Add the bytes. *)
   I.map_bytes_be (Buffer._add_bits buf) (Buffer.add_byte buf) v flen
 
+(* Construct a field of exactly 32 bits. *)
+let construct_int32_be_unsigned buf v flen _ =
+  Buffer.add_byte buf
+    (Int32.to_int (Int32.shift_right_logical v 24));
+  Buffer.add_byte buf
+    (Int32.to_int ((Int32.logand (Int32.shift_right_logical v 16) 0xff_l)));
+  Buffer.add_byte buf
+    (Int32.to_int ((Int32.logand (Int32.shift_right_logical v 8) 0xff_l)));
+  Buffer.add_byte buf
+    (Int32.to_int (Int32.logand v 0xff_l))
+
 (* Construct a field of up to 64 bits. *)
 let construct_int64_be_unsigned buf v flen exn =
   (* Check value is within range. *)
@@ -650,6 +707,13 @@ let construct_int64_be_unsigned buf v flen exn =
   (* Add the bytes. *)
   I64.map_bytes_be (Buffer._add_bits buf) (Buffer.add_byte buf) v flen
 
+(* Construct from a string of bytes, exact multiple of 8 bits
+ * in length of course.
+ *)
+let construct_string buf str =
+  let len = String.length str in
+  Buffer.add_bits buf str (len lsl 3)
+
 (*----------------------------------------------------------------------*)
 (* Extract a string from a bitstring. *)