2 * Copyright (C) 2008 Red Hat Inc., Richard W.M. Jones
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this library; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18 * $Id: bitmatch.ml,v 1.14 2008-05-12 20:32:55 rjones Exp $
23 include Bitmatch_types
24 include Bitmatch_config
26 (* Enable runtime debug messages. Must also have been enabled
32 exception Construct_failure of string * string * int * int
34 (* A bitstring is simply the data itself (as a string), and the
35 * bitoffset and the bitlength within the string. Note offset/length
36 * are counted in bits, not bytes.
38 type bitstring = string * int * int
40 (* Functions to create and load bitstrings. *)
41 let empty_bitstring = "", 0, 0
43 let make_bitstring len c = String.make ((len+7) lsr 3) c, 0, len
45 let create_bitstring len = make_bitstring len '\000'
47 let bitstring_of_string str = str, 0, String.length str lsl 3
49 let bitstring_of_chan chan =
50 let tmpsize = 16384 in
51 let buf = Buffer.create tmpsize in
52 let tmp = String.create tmpsize in
54 while n := input chan tmp 0 tmpsize; !n > 0 do
55 Buffer.add_substring buf tmp 0 !n;
57 Buffer.contents buf, 0, Buffer.length buf lsl 3
59 let bitstring_of_chan_max chan max =
60 let tmpsize = 16384 in
61 let buf = Buffer.create tmpsize in
62 let tmp = String.create tmpsize in
66 let r = min tmpsize (max - !len) in
67 let n = input chan tmp 0 r in
69 Buffer.add_substring buf tmp 0 n;
76 Buffer.contents buf, 0, !len lsl 3
78 let bitstring_of_file_descr fd =
79 let tmpsize = 16384 in
80 let buf = Buffer.create tmpsize in
81 let tmp = String.create tmpsize in
83 while n := Unix.read fd tmp 0 tmpsize; !n > 0 do
84 Buffer.add_substring buf tmp 0 !n;
86 Buffer.contents buf, 0, Buffer.length buf lsl 3
88 let bitstring_of_file_descr_max fd max =
89 let tmpsize = 16384 in
90 let buf = Buffer.create tmpsize in
91 let tmp = String.create tmpsize in
95 let r = min tmpsize (max - !len) in
96 let n = Unix.read fd tmp 0 r in
98 Buffer.add_substring buf tmp 0 n;
105 Buffer.contents buf, 0, !len lsl 3
107 let bitstring_of_file fname =
108 let chan = open_in_bin fname in
109 let bs = bitstring_of_chan chan in
113 let bitstring_length (_, _, len) = len
115 (*----------------------------------------------------------------------*)
116 (* Bitwise functions.
118 * We try to isolate all bitwise functions within these modules.
122 (* Bitwise operations on ints. Note that we assume int <= 31 bits. *)
125 external to_int : int -> int = "%identity"
131 (* Create a mask so many bits wide. *)
135 else if bits = 30 then
137 else if bits = 31 then
140 invalid_arg "Bitmatch.I.mask"
142 (* Byte swap an int of a given size. *)
143 let byteswap v bits =
145 else if bits <= 16 then (
146 let shift = bits-8 in
147 let v1 = v >> shift in
148 let v2 = (v land (mask shift)) << 8 in
150 ) else if bits <= 24 then (
151 let shift = bits - 16 in
152 let v1 = v >> (8+shift) in
153 let v2 = ((v >> shift) land ff) << 8 in
154 let v3 = (v land (mask shift)) << 16 in
157 let shift = bits - 24 in
158 let v1 = v >> (16+shift) in
159 let v2 = ((v >> (8+shift)) land ff) << 8 in
160 let v3 = ((v >> shift) land ff) << 16 in
161 let v4 = (v land (mask shift)) << 24 in
162 v4 lor v3 lor v2 lor v1
165 (* Check a value is in range 0 .. 2^bits-1. *)
166 let range_unsigned v bits =
167 let mask = lnot (mask bits) in
170 (* Call function g on the top bits, then f on each full byte
171 * (big endian - so start at top).
173 let rec map_bytes_be g f v bits =
175 map_bytes_be g f (v >> 8) (bits-8);
176 let lsb = v land ff in
178 ) else if bits > 0 then (
179 let lsb = v land (mask bits) in
185 (* Bitwise operations on int32s. Note we try to keep it as similar
186 * as possible to the I module above, to make it easier to track
189 let (<<) = Int32.shift_left
190 let (>>) = Int32.shift_right_logical
191 let (land) = Int32.logand
192 let (lor) = Int32.logor
193 let lnot = Int32.lognot
194 let pred = Int32.pred
195 let max_int = Int32.max_int
196 let to_int = Int32.to_int
197 let zero = Int32.zero
199 let minus_one = Int32.minus_one
202 (* Create a mask so many bits wide. *)
206 else if bits = 31 then
208 else if bits = 32 then
211 invalid_arg "Bitmatch.I32.mask"
213 (* Byte swap an int of a given size. *)
214 let byteswap v bits =
216 else if bits <= 16 then (
217 let shift = bits-8 in
218 let v1 = v >> shift in
219 let v2 = (v land (mask shift)) << 8 in
221 ) else if bits <= 24 then (
222 let shift = bits - 16 in
223 let v1 = v >> (8+shift) in
224 let v2 = ((v >> shift) land ff) << 8 in
225 let v3 = (v land (mask shift)) << 16 in
228 let shift = bits - 24 in
229 let v1 = v >> (16+shift) in
230 let v2 = ((v >> (8+shift)) land ff) << 8 in
231 let v3 = ((v >> shift) land ff) << 16 in
232 let v4 = (v land (mask shift)) << 24 in
233 v4 lor v3 lor v2 lor v1
236 (* Check a value is in range 0 .. 2^bits-1. *)
237 let range_unsigned v bits =
238 let mask = lnot (mask bits) in
241 (* Call function g on the top bits, then f on each full byte
242 * (big endian - so start at top).
244 let rec map_bytes_be g f v bits =
246 map_bytes_be g f (v >> 8) (bits-8);
247 let lsb = v land ff in
249 ) else if bits > 0 then (
250 let lsb = v land (mask bits) in
256 (* Bitwise operations on int64s. Note we try to keep it as similar
257 * as possible to the I/I32 modules above, to make it easier to track
260 let (<<) = Int64.shift_left
261 let (>>) = Int64.shift_right_logical
262 let (land) = Int64.logand
263 let (lor) = Int64.logor
264 let lnot = Int64.lognot
265 let pred = Int64.pred
266 let max_int = Int64.max_int
267 let to_int = Int64.to_int
268 let zero = Int64.zero
270 let minus_one = Int64.minus_one
273 (* Create a mask so many bits wide. *)
277 else if bits = 63 then
279 else if bits = 64 then
282 invalid_arg "Bitmatch.I64.mask"
284 (* Byte swap an int of a given size. *)
285 (* let byteswap v bits = *)
287 (* Check a value is in range 0 .. 2^bits-1. *)
288 let range_unsigned v bits =
289 let mask = lnot (mask bits) in
292 (* Call function g on the top bits, then f on each full byte
293 * (big endian - so start at top).
295 let rec map_bytes_be g f v bits =
297 map_bytes_be g f (v >> 8) (bits-8);
298 let lsb = v land ff in
300 ) else if bits > 0 then (
301 let lsb = v land (mask bits) in
306 (*----------------------------------------------------------------------*)
307 (* Extraction functions.
309 * NB: internal functions, called from the generated macros, and
310 * the parameters should have been checked for sanity already).
314 let extract_bitstring data off len flen =
315 (data, off, flen), off+flen, len-flen
317 let extract_remainder data off len =
318 (data, off, len), off+len, 0
320 (* Extract and convert to numeric. A single bit is returned as
321 * a boolean. There are no endianness or signedness considerations.
323 let extract_bit data off len _ = (* final param is always 1 *)
324 let byteoff = off lsr 3 in
325 let bitmask = 1 lsl (7 - (off land 7)) in
326 let b = Char.code data.[byteoff] land bitmask <> 0 in
329 (* Returns 8 bit unsigned aligned bytes from the string.
330 * If the string ends then this returns 0's.
332 let _get_byte data byteoff strlen =
333 if strlen > byteoff then Char.code data.[byteoff] else 0
334 let _get_byte32 data byteoff strlen =
335 if strlen > byteoff then Int32.of_int (Char.code data.[byteoff]) else 0l
336 let _get_byte64 data byteoff strlen =
337 if strlen > byteoff then Int64.of_int (Char.code data.[byteoff]) else 0L
339 (* Extract [2..8] bits. Because the result fits into a single
340 * byte we don't have to worry about endianness, only signedness.
342 let extract_char_unsigned data off len flen =
343 let byteoff = off lsr 3 in
345 (* Optimize the common (byte-aligned) case. *)
346 if off land 7 = 0 then (
347 let byte = Char.code data.[byteoff] in
348 byte lsr (8 - flen), off+flen, len-flen
350 (* Extract the 16 bits at byteoff and byteoff+1 (note that the
351 * second byte might not exist in the original string).
353 let strlen = String.length data in
356 (_get_byte data byteoff strlen lsl 8) +
357 _get_byte data (byteoff+1) strlen in
359 (* Mask off the top bits. *)
360 let bitmask = (1 lsl (16 - (off land 7))) - 1 in
361 let word = word land bitmask in
362 (* Shift right to get rid of the bottom bits. *)
363 let shift = 16 - ((off land 7) + flen) in
364 let word = word lsr shift in
366 word, off+flen, len-flen
369 (* Extract [9..31] bits. We have to consider endianness and signedness. *)
370 let extract_int_be_unsigned data off len flen =
371 let byteoff = off lsr 3 in
373 let strlen = String.length data in
376 (* Optimize the common (byte-aligned) case. *)
377 if off land 7 = 0 then (
379 (_get_byte data byteoff strlen lsl 23) +
380 (_get_byte data (byteoff+1) strlen lsl 15) +
381 (_get_byte data (byteoff+2) strlen lsl 7) +
382 (_get_byte data (byteoff+3) strlen lsr 1) in
384 ) else if flen <= 24 then (
385 (* Extract the 31 bits at byteoff .. byteoff+3. *)
387 (_get_byte data byteoff strlen lsl 23) +
388 (_get_byte data (byteoff+1) strlen lsl 15) +
389 (_get_byte data (byteoff+2) strlen lsl 7) +
390 (_get_byte data (byteoff+3) strlen lsr 1) in
391 (* Mask off the top bits. *)
392 let bitmask = (1 lsl (31 - (off land 7))) - 1 in
393 let word = word land bitmask in
394 (* Shift right to get rid of the bottom bits. *)
395 let shift = 31 - ((off land 7) + flen) in
398 (* Extract the next 31 bits, slow method. *)
400 let c0, off, len = extract_char_unsigned data off len 8 in
401 let c1, off, len = extract_char_unsigned data off len 8 in
402 let c2, off, len = extract_char_unsigned data off len 8 in
403 let c3, off, len = extract_char_unsigned data off len 7 in
404 (c0 lsl 23) + (c1 lsl 15) + (c2 lsl 7) + c3 in
407 word, off+flen, len-flen
409 let extract_int_le_unsigned data off len flen =
410 let v, off, len = extract_int_be_unsigned data off len flen in
411 let v = I.byteswap v flen in
414 let extract_int_ne_unsigned =
415 if nativeendian = BigEndian
416 then extract_int_be_unsigned
417 else extract_int_le_unsigned
419 let _make_int32_be c0 c1 c2 c3 =
423 (Int32.shift_left c0 24)
424 (Int32.shift_left c1 16))
425 (Int32.shift_left c2 8))
428 let _make_int32_le c0 c1 c2 c3 =
432 (Int32.shift_left c3 24)
433 (Int32.shift_left c2 16))
434 (Int32.shift_left c1 8))
437 (* Extract exactly 32 bits. We have to consider endianness and signedness. *)
438 let extract_int32_be_unsigned data off len flen =
439 let byteoff = off lsr 3 in
441 let strlen = String.length data in
444 (* Optimize the common (byte-aligned) case. *)
445 if off land 7 = 0 then (
447 let c0 = _get_byte32 data byteoff strlen in
448 let c1 = _get_byte32 data (byteoff+1) strlen in
449 let c2 = _get_byte32 data (byteoff+2) strlen in
450 let c3 = _get_byte32 data (byteoff+3) strlen in
451 _make_int32_be c0 c1 c2 c3 in
452 Int32.shift_right_logical word (32 - flen)
454 (* Extract the next 32 bits, slow method. *)
456 let c0, off, len = extract_char_unsigned data off len 8 in
457 let c1, off, len = extract_char_unsigned data off len 8 in
458 let c2, off, len = extract_char_unsigned data off len 8 in
459 let c3, _, _ = extract_char_unsigned data off len 8 in
460 let c0 = Int32.of_int c0 in
461 let c1 = Int32.of_int c1 in
462 let c2 = Int32.of_int c2 in
463 let c3 = Int32.of_int c3 in
464 _make_int32_be c0 c1 c2 c3 in
465 Int32.shift_right_logical word (32 - flen)
467 word, off+flen, len-flen
469 let extract_int32_le_unsigned data off len flen =
470 let v, off, len = extract_int32_be_unsigned data off len flen in
471 let v = I32.byteswap v flen in
474 let extract_int32_ne_unsigned =
475 if nativeendian = BigEndian
476 then extract_int32_be_unsigned
477 else extract_int32_le_unsigned
479 let _make_int64_be c0 c1 c2 c3 c4 c5 c6 c7 =
487 (Int64.shift_left c0 56)
488 (Int64.shift_left c1 48))
489 (Int64.shift_left c2 40))
490 (Int64.shift_left c3 32))
491 (Int64.shift_left c4 24))
492 (Int64.shift_left c5 16))
493 (Int64.shift_left c6 8))
496 let _make_int64_le c0 c1 c2 c3 c4 c5 c6 c7 =
497 _make_int64_be c7 c6 c5 c4 c3 c2 c1 c0
499 (* Extract [1..64] bits. We have to consider endianness and signedness. *)
500 let extract_int64_be_unsigned data off len flen =
501 let byteoff = off lsr 3 in
503 let strlen = String.length data in
506 (* Optimize the common (byte-aligned) case. *)
507 if off land 7 = 0 then (
509 let c0 = _get_byte64 data byteoff strlen in
510 let c1 = _get_byte64 data (byteoff+1) strlen in
511 let c2 = _get_byte64 data (byteoff+2) strlen in
512 let c3 = _get_byte64 data (byteoff+3) strlen in
513 let c4 = _get_byte64 data (byteoff+4) strlen in
514 let c5 = _get_byte64 data (byteoff+5) strlen in
515 let c6 = _get_byte64 data (byteoff+6) strlen in
516 let c7 = _get_byte64 data (byteoff+7) strlen in
517 _make_int64_be c0 c1 c2 c3 c4 c5 c6 c7 in
518 Int64.shift_right_logical word (64 - flen)
520 (* Extract the next 64 bits, slow method. *)
522 let c0, off, len = extract_char_unsigned data off len 8 in
523 let c1, off, len = extract_char_unsigned data off len 8 in
524 let c2, off, len = extract_char_unsigned data off len 8 in
525 let c3, off, len = extract_char_unsigned data off len 8 in
526 let c4, off, len = extract_char_unsigned data off len 8 in
527 let c5, off, len = extract_char_unsigned data off len 8 in
528 let c6, off, len = extract_char_unsigned data off len 8 in
529 let c7, _, _ = extract_char_unsigned data off len 8 in
530 let c0 = Int64.of_int c0 in
531 let c1 = Int64.of_int c1 in
532 let c2 = Int64.of_int c2 in
533 let c3 = Int64.of_int c3 in
534 let c4 = Int64.of_int c4 in
535 let c5 = Int64.of_int c5 in
536 let c6 = Int64.of_int c6 in
537 let c7 = Int64.of_int c7 in
538 _make_int64_be c0 c1 c2 c3 c4 c5 c6 c7 in
539 Int64.shift_right_logical word (64 - flen)
541 word, off+flen, len-flen
543 let extract_int64_le_unsigned data off len flen =
544 let byteoff = off lsr 3 in
546 let strlen = String.length data in
549 (* Optimize the common (byte-aligned) case. *)
550 if off land 7 = 0 then (
552 let c0 = _get_byte64 data byteoff strlen in
553 let c1 = _get_byte64 data (byteoff+1) strlen in
554 let c2 = _get_byte64 data (byteoff+2) strlen in
555 let c3 = _get_byte64 data (byteoff+3) strlen in
556 let c4 = _get_byte64 data (byteoff+4) strlen in
557 let c5 = _get_byte64 data (byteoff+5) strlen in
558 let c6 = _get_byte64 data (byteoff+6) strlen in
559 let c7 = _get_byte64 data (byteoff+7) strlen in
560 _make_int64_le c0 c1 c2 c3 c4 c5 c6 c7 in
561 Int64.logand word (I64.mask flen)
563 (* Extract the next 64 bits, slow method. *)
565 let c0, off, len = extract_char_unsigned data off len 8 in
566 let c1, off, len = extract_char_unsigned data off len 8 in
567 let c2, off, len = extract_char_unsigned data off len 8 in
568 let c3, off, len = extract_char_unsigned data off len 8 in
569 let c4, off, len = extract_char_unsigned data off len 8 in
570 let c5, off, len = extract_char_unsigned data off len 8 in
571 let c6, off, len = extract_char_unsigned data off len 8 in
572 let c7, _, _ = extract_char_unsigned data off len 8 in
573 let c0 = Int64.of_int c0 in
574 let c1 = Int64.of_int c1 in
575 let c2 = Int64.of_int c2 in
576 let c3 = Int64.of_int c3 in
577 let c4 = Int64.of_int c4 in
578 let c5 = Int64.of_int c5 in
579 let c6 = Int64.of_int c6 in
580 let c7 = Int64.of_int c7 in
581 _make_int64_le c0 c1 c2 c3 c4 c5 c6 c7 in
582 Int64.logand word (I64.mask flen)
584 word, off+flen, len-flen
586 let extract_int64_ne_unsigned =
587 if nativeendian = BigEndian
588 then extract_int64_be_unsigned
589 else extract_int64_le_unsigned
591 (*----------------------------------------------------------------------*)
592 (* Constructor functions. *)
594 module Buffer = struct
597 mutable len : int; (* Length in bits. *)
598 (* Last byte in the buffer (if len is not aligned). We store
599 * it outside the buffer because buffers aren't mutable.
605 (* XXX We have almost enough information in the generator to
606 * choose a good initial size.
608 { buf = Buffer.create 128; len = 0; last = 0 }
610 let contents { buf = buf; len = len; last = last } =
612 if len land 7 = 0 then
615 Buffer.contents buf ^ (String.make 1 (Char.chr last)) in
618 (* Add exactly 8 bits. *)
619 let add_byte ({ buf = buf; len = len; last = last } as t) byte =
620 if byte < 0 || byte > 255 then invalid_arg "Bitmatch.Buffer.add_byte";
621 let shift = len land 7 in
623 (* Target buffer is byte-aligned. *)
624 Buffer.add_char buf (Char.chr byte)
626 (* Target buffer is unaligned. 'last' is meaningful. *)
627 let first = byte lsr shift in
628 let second = (byte lsl (8 - shift)) land 0xff in
629 Buffer.add_char buf (Char.chr (last lor first));
634 (* Add exactly 1 bit. *)
635 let add_bit ({ buf = buf; len = len; last = last } as t) bit =
636 let shift = 7 - (len land 7) in
638 (* Somewhere in the middle of 'last'. *)
639 t.last <- last lor ((if bit then 1 else 0) lsl shift)
641 (* Just a single spare bit in 'last'. *)
642 let last = last lor if bit then 1 else 0 in
643 Buffer.add_char buf (Char.chr last);
648 (* Add a small number of bits (definitely < 8). This uses a loop
649 * to call add_bit so it's slow.
651 let _add_bits t c slen =
652 if slen < 1 || slen >= 8 then invalid_arg "Bitmatch.Buffer._add_bits";
653 for i = slen-1 downto 0 do
654 let bit = c land (1 lsl i) <> 0 in
658 let add_bits ({ buf = buf; len = len } as t) str slen =
660 if len land 7 = 0 then (
661 if slen land 7 = 0 then
662 (* Common case - everything is byte-aligned. *)
663 Buffer.add_substring buf str 0 (slen lsr 3)
665 (* Target buffer is aligned. Copy whole bytes then leave the
666 * remaining bits in last.
668 let slenbytes = slen lsr 3 in
669 if slenbytes > 0 then Buffer.add_substring buf str 0 slenbytes;
670 t.last <- Char.code str.[slenbytes] lsl (8 - (slen land 7))
674 (* Target buffer is unaligned. Copy whole bytes using
675 * add_byte which knows how to deal with an unaligned
676 * target buffer, then call _add_bits for the remaining < 8 bits.
678 * XXX This is going to be dog-slow.
680 let slenbytes = slen lsr 3 in
681 for i = 0 to slenbytes-1 do
682 let byte = Char.code str.[i] in
685 _add_bits t (Char.code str.[slenbytes]) (slen - (slenbytes lsl 3))
690 (* Construct a single bit. *)
691 let construct_bit buf b _ _ =
694 (* Construct a field, flen = [2..8]. *)
695 let construct_char_unsigned buf v flen exn =
696 let max_val = 1 lsl flen in
697 if v < 0 || v >= max_val then raise exn;
699 Buffer.add_byte buf v
701 Buffer._add_bits buf v flen
703 (* Construct a field of up to 31 bits. *)
704 let construct_int_be_unsigned buf v flen exn =
705 (* Check value is within range. *)
706 if not (I.range_unsigned v flen) then raise exn;
708 I.map_bytes_be (Buffer._add_bits buf) (Buffer.add_byte buf) v flen
710 let construct_int_ne_unsigned =
711 if nativeendian = BigEndian
712 then construct_int_be_unsigned
713 else (*construct_int_le_unsigned*)
714 fun _ _ _ _ -> failwith "construct_int_le_unsigned"
716 (* Construct a field of exactly 32 bits. *)
717 let construct_int32_be_unsigned buf v flen _ =
719 (Int32.to_int (Int32.shift_right_logical v 24));
721 (Int32.to_int ((Int32.logand (Int32.shift_right_logical v 16) 0xff_l)));
723 (Int32.to_int ((Int32.logand (Int32.shift_right_logical v 8) 0xff_l)));
725 (Int32.to_int (Int32.logand v 0xff_l))
727 let construct_int32_ne_unsigned =
728 if nativeendian = BigEndian
729 then construct_int32_be_unsigned
730 else (*construct_int32_le_unsigned*)
731 fun _ _ _ _ -> failwith "construct_int32_le_unsigned"
733 (* Construct a field of up to 64 bits. *)
734 let construct_int64_be_unsigned buf v flen exn =
735 (* Check value is within range. *)
736 if not (I64.range_unsigned v flen) then raise exn;
738 I64.map_bytes_be (Buffer._add_bits buf) (Buffer.add_byte buf) v flen
740 let construct_int64_ne_unsigned =
741 if nativeendian = BigEndian
742 then construct_int64_be_unsigned
743 else (*construct_int64_le_unsigned*)
744 fun _ _ _ _ -> failwith "construct_int64_le_unsigned"
746 (* Construct from a string of bytes, exact multiple of 8 bits
747 * in length of course.
749 let construct_string buf str =
750 let len = String.length str in
751 Buffer.add_bits buf str (len lsl 3)
753 (*----------------------------------------------------------------------*)
754 (* Extract a string from a bitstring. *)
756 let string_of_bitstring (data, off, len) =
757 if off land 7 = 0 && len land 7 = 0 then
758 (* Easy case: everything is byte-aligned. *)
759 String.sub data (off lsr 3) (len lsr 3)
761 (* Bit-twiddling case. *)
762 let strlen = (len + 7) lsr 3 in
763 let str = String.make strlen '\000' in
764 let rec loop data off len i =
766 let c, off, len = extract_char_unsigned data off len 8 in
767 str.[i] <- Char.chr c;
768 loop data off len (i+1)
769 ) else if len > 0 then (
770 let c, off, len = extract_char_unsigned data off len len in
771 str.[i] <- Char.chr c
778 (*----------------------------------------------------------------------*)
779 (* Display functions. *)
782 let c = Char.code c in
785 let hexdump_bitstring chan (data, off, len) =
789 let linelen = ref 0 in
790 let linechars = String.make 16 ' ' in
792 fprintf chan "00000000 ";
795 let bits = min !len 8 in
796 let byte, off', len' = extract_char_unsigned data !off !len bits in
797 off := off'; len := len';
799 let byte = byte lsl (8-bits) in
800 fprintf chan "%02x " byte;
803 linechars.[!linelen] <-
804 (let c = Char.chr byte in
805 if isprint c then c else '.');
807 if !linelen = 8 then fprintf chan " ";
808 if !linelen = 16 then (
809 fprintf chan " |%s|\n%08x " linechars !count;
811 for i = 0 to 15 do linechars.[i] <- ' ' done
815 if !linelen > 0 then (
816 let skip = (16 - !linelen) * 3 + if !linelen < 8 then 1 else 0 in
817 for i = 0 to skip-1 do fprintf chan " " done;
818 fprintf chan " |%s|\n%!" linechars