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
110 let bs = bitstring_of_chan chan in
117 let bitstring_length (_, _, len) = len
119 (*----------------------------------------------------------------------*)
120 (* Bitwise functions.
122 * We try to isolate all bitwise functions within these modules.
126 (* Bitwise operations on ints. Note that we assume int <= 31 bits. *)
129 external to_int : int -> int = "%identity"
135 (* Create a mask so many bits wide. *)
139 else if bits = 30 then
141 else if bits = 31 then
144 invalid_arg "Bitmatch.I.mask"
146 (* Byte swap an int of a given size. *)
147 let byteswap v bits =
149 else if bits <= 16 then (
150 let shift = bits-8 in
151 let v1 = v >> shift in
152 let v2 = (v land (mask shift)) << 8 in
154 ) else if bits <= 24 then (
155 let shift = bits - 16 in
156 let v1 = v >> (8+shift) in
157 let v2 = ((v >> shift) land ff) << 8 in
158 let v3 = (v land (mask shift)) << 16 in
161 let shift = bits - 24 in
162 let v1 = v >> (16+shift) in
163 let v2 = ((v >> (8+shift)) land ff) << 8 in
164 let v3 = ((v >> shift) land ff) << 16 in
165 let v4 = (v land (mask shift)) << 24 in
166 v4 lor v3 lor v2 lor v1
169 (* Check a value is in range 0 .. 2^bits-1. *)
170 let range_unsigned v bits =
171 let mask = lnot (mask bits) in
174 (* Call function g on the top bits, then f on each full byte
175 * (big endian - so start at top).
177 let rec map_bytes_be g f v bits =
179 map_bytes_be g f (v >> 8) (bits-8);
180 let lsb = v land ff in
182 ) else if bits > 0 then (
183 let lsb = v land (mask bits) in
189 (* Bitwise operations on int32s. Note we try to keep it as similar
190 * as possible to the I module above, to make it easier to track
193 let (<<) = Int32.shift_left
194 let (>>) = Int32.shift_right_logical
195 let (land) = Int32.logand
196 let (lor) = Int32.logor
197 let lnot = Int32.lognot
198 let pred = Int32.pred
199 let max_int = Int32.max_int
200 let to_int = Int32.to_int
201 let zero = Int32.zero
203 let minus_one = Int32.minus_one
206 (* Create a mask so many bits wide. *)
210 else if bits = 31 then
212 else if bits = 32 then
215 invalid_arg "Bitmatch.I32.mask"
217 (* Byte swap an int of a given size. *)
218 let byteswap v bits =
220 else if bits <= 16 then (
221 let shift = bits-8 in
222 let v1 = v >> shift in
223 let v2 = (v land (mask shift)) << 8 in
225 ) else if bits <= 24 then (
226 let shift = bits - 16 in
227 let v1 = v >> (8+shift) in
228 let v2 = ((v >> shift) land ff) << 8 in
229 let v3 = (v land (mask shift)) << 16 in
232 let shift = bits - 24 in
233 let v1 = v >> (16+shift) in
234 let v2 = ((v >> (8+shift)) land ff) << 8 in
235 let v3 = ((v >> shift) land ff) << 16 in
236 let v4 = (v land (mask shift)) << 24 in
237 v4 lor v3 lor v2 lor v1
240 (* Check a value is in range 0 .. 2^bits-1. *)
241 let range_unsigned v bits =
242 let mask = lnot (mask bits) in
245 (* Call function g on the top bits, then f on each full byte
246 * (big endian - so start at top).
248 let rec map_bytes_be g f v bits =
250 map_bytes_be g f (v >> 8) (bits-8);
251 let lsb = v land ff in
253 ) else if bits > 0 then (
254 let lsb = v land (mask bits) in
260 (* Bitwise operations on int64s. Note we try to keep it as similar
261 * as possible to the I/I32 modules above, to make it easier to track
264 let (<<) = Int64.shift_left
265 let (>>) = Int64.shift_right_logical
266 let (land) = Int64.logand
267 let (lor) = Int64.logor
268 let lnot = Int64.lognot
269 let pred = Int64.pred
270 let max_int = Int64.max_int
271 let to_int = Int64.to_int
272 let zero = Int64.zero
274 let minus_one = Int64.minus_one
277 (* Create a mask so many bits wide. *)
281 else if bits = 63 then
283 else if bits = 64 then
286 invalid_arg "Bitmatch.I64.mask"
288 (* Byte swap an int of a given size. *)
289 (* let byteswap v bits = *)
291 (* Check a value is in range 0 .. 2^bits-1. *)
292 let range_unsigned v bits =
293 let mask = lnot (mask bits) in
296 (* Call function g on the top bits, then f on each full byte
297 * (big endian - so start at top).
299 let rec map_bytes_be g f v bits =
301 map_bytes_be g f (v >> 8) (bits-8);
302 let lsb = v land ff in
304 ) else if bits > 0 then (
305 let lsb = v land (mask bits) in
310 (*----------------------------------------------------------------------*)
311 (* Extraction functions.
313 * NB: internal functions, called from the generated macros, and
314 * the parameters should have been checked for sanity already).
318 let extract_bitstring data off len flen =
319 (data, off, flen), off+flen, len-flen
321 let extract_remainder data off len =
322 (data, off, len), off+len, 0
324 (* Extract and convert to numeric. A single bit is returned as
325 * a boolean. There are no endianness or signedness considerations.
327 let extract_bit data off len _ = (* final param is always 1 *)
328 let byteoff = off lsr 3 in
329 let bitmask = 1 lsl (7 - (off land 7)) in
330 let b = Char.code data.[byteoff] land bitmask <> 0 in
333 (* Returns 8 bit unsigned aligned bytes from the string.
334 * If the string ends then this returns 0's.
336 let _get_byte data byteoff strlen =
337 if strlen > byteoff then Char.code data.[byteoff] else 0
338 let _get_byte32 data byteoff strlen =
339 if strlen > byteoff then Int32.of_int (Char.code data.[byteoff]) else 0l
340 let _get_byte64 data byteoff strlen =
341 if strlen > byteoff then Int64.of_int (Char.code data.[byteoff]) else 0L
343 (* Extract [2..8] bits. Because the result fits into a single
344 * byte we don't have to worry about endianness, only signedness.
346 let extract_char_unsigned data off len flen =
347 let byteoff = off lsr 3 in
349 (* Optimize the common (byte-aligned) case. *)
350 if off land 7 = 0 then (
351 let byte = Char.code data.[byteoff] in
352 byte lsr (8 - flen), off+flen, len-flen
354 (* Extract the 16 bits at byteoff and byteoff+1 (note that the
355 * second byte might not exist in the original string).
357 let strlen = String.length data in
360 (_get_byte data byteoff strlen lsl 8) +
361 _get_byte data (byteoff+1) strlen in
363 (* Mask off the top bits. *)
364 let bitmask = (1 lsl (16 - (off land 7))) - 1 in
365 let word = word land bitmask in
366 (* Shift right to get rid of the bottom bits. *)
367 let shift = 16 - ((off land 7) + flen) in
368 let word = word lsr shift in
370 word, off+flen, len-flen
373 (* Extract [9..31] bits. We have to consider endianness and signedness. *)
374 let extract_int_be_unsigned data off len flen =
375 let byteoff = off lsr 3 in
377 let strlen = String.length data in
380 (* Optimize the common (byte-aligned) case. *)
381 if off land 7 = 0 then (
383 (_get_byte data byteoff strlen lsl 23) +
384 (_get_byte data (byteoff+1) strlen lsl 15) +
385 (_get_byte data (byteoff+2) strlen lsl 7) +
386 (_get_byte data (byteoff+3) strlen lsr 1) in
388 ) else if flen <= 24 then (
389 (* Extract the 31 bits at byteoff .. byteoff+3. *)
391 (_get_byte data byteoff strlen lsl 23) +
392 (_get_byte data (byteoff+1) strlen lsl 15) +
393 (_get_byte data (byteoff+2) strlen lsl 7) +
394 (_get_byte data (byteoff+3) strlen lsr 1) in
395 (* Mask off the top bits. *)
396 let bitmask = (1 lsl (31 - (off land 7))) - 1 in
397 let word = word land bitmask in
398 (* Shift right to get rid of the bottom bits. *)
399 let shift = 31 - ((off land 7) + flen) in
402 (* Extract the next 31 bits, slow method. *)
404 let c0, off, len = extract_char_unsigned data off len 8 in
405 let c1, off, len = extract_char_unsigned data off len 8 in
406 let c2, off, len = extract_char_unsigned data off len 8 in
407 let c3, off, len = extract_char_unsigned data off len 7 in
408 (c0 lsl 23) + (c1 lsl 15) + (c2 lsl 7) + c3 in
411 word, off+flen, len-flen
413 let extract_int_le_unsigned data off len flen =
414 let v, off, len = extract_int_be_unsigned data off len flen in
415 let v = I.byteswap v flen in
418 let extract_int_ne_unsigned =
419 if nativeendian = BigEndian
420 then extract_int_be_unsigned
421 else extract_int_le_unsigned
423 let _make_int32_be c0 c1 c2 c3 =
427 (Int32.shift_left c0 24)
428 (Int32.shift_left c1 16))
429 (Int32.shift_left c2 8))
432 let _make_int32_le c0 c1 c2 c3 =
436 (Int32.shift_left c3 24)
437 (Int32.shift_left c2 16))
438 (Int32.shift_left c1 8))
441 (* Extract exactly 32 bits. We have to consider endianness and signedness. *)
442 let extract_int32_be_unsigned data off len flen =
443 let byteoff = off lsr 3 in
445 let strlen = String.length data in
448 (* Optimize the common (byte-aligned) case. *)
449 if off land 7 = 0 then (
451 let c0 = _get_byte32 data byteoff strlen in
452 let c1 = _get_byte32 data (byteoff+1) strlen in
453 let c2 = _get_byte32 data (byteoff+2) strlen in
454 let c3 = _get_byte32 data (byteoff+3) strlen in
455 _make_int32_be c0 c1 c2 c3 in
456 Int32.shift_right_logical word (32 - flen)
458 (* Extract the next 32 bits, slow method. *)
460 let c0, off, len = extract_char_unsigned data off len 8 in
461 let c1, off, len = extract_char_unsigned data off len 8 in
462 let c2, off, len = extract_char_unsigned data off len 8 in
463 let c3, _, _ = extract_char_unsigned data off len 8 in
464 let c0 = Int32.of_int c0 in
465 let c1 = Int32.of_int c1 in
466 let c2 = Int32.of_int c2 in
467 let c3 = Int32.of_int c3 in
468 _make_int32_be c0 c1 c2 c3 in
469 Int32.shift_right_logical word (32 - flen)
471 word, off+flen, len-flen
473 let extract_int32_le_unsigned data off len flen =
474 let v, off, len = extract_int32_be_unsigned data off len flen in
475 let v = I32.byteswap v flen in
478 let extract_int32_ne_unsigned =
479 if nativeendian = BigEndian
480 then extract_int32_be_unsigned
481 else extract_int32_le_unsigned
483 let _make_int64_be c0 c1 c2 c3 c4 c5 c6 c7 =
491 (Int64.shift_left c0 56)
492 (Int64.shift_left c1 48))
493 (Int64.shift_left c2 40))
494 (Int64.shift_left c3 32))
495 (Int64.shift_left c4 24))
496 (Int64.shift_left c5 16))
497 (Int64.shift_left c6 8))
500 let _make_int64_le c0 c1 c2 c3 c4 c5 c6 c7 =
501 _make_int64_be c7 c6 c5 c4 c3 c2 c1 c0
503 (* Extract [1..64] bits. We have to consider endianness and signedness. *)
504 let extract_int64_be_unsigned data off len flen =
505 let byteoff = off lsr 3 in
507 let strlen = String.length data in
510 (* Optimize the common (byte-aligned) case. *)
511 if off land 7 = 0 then (
513 let c0 = _get_byte64 data byteoff strlen in
514 let c1 = _get_byte64 data (byteoff+1) strlen in
515 let c2 = _get_byte64 data (byteoff+2) strlen in
516 let c3 = _get_byte64 data (byteoff+3) strlen in
517 let c4 = _get_byte64 data (byteoff+4) strlen in
518 let c5 = _get_byte64 data (byteoff+5) strlen in
519 let c6 = _get_byte64 data (byteoff+6) strlen in
520 let c7 = _get_byte64 data (byteoff+7) strlen in
521 _make_int64_be c0 c1 c2 c3 c4 c5 c6 c7 in
522 Int64.shift_right_logical word (64 - flen)
524 (* Extract the next 64 bits, slow method. *)
526 let c0, off, len = extract_char_unsigned data off len 8 in
527 let c1, off, len = extract_char_unsigned data off len 8 in
528 let c2, off, len = extract_char_unsigned data off len 8 in
529 let c3, off, len = extract_char_unsigned data off len 8 in
530 let c4, off, len = extract_char_unsigned data off len 8 in
531 let c5, off, len = extract_char_unsigned data off len 8 in
532 let c6, off, len = extract_char_unsigned data off len 8 in
533 let c7, _, _ = extract_char_unsigned data off len 8 in
534 let c0 = Int64.of_int c0 in
535 let c1 = Int64.of_int c1 in
536 let c2 = Int64.of_int c2 in
537 let c3 = Int64.of_int c3 in
538 let c4 = Int64.of_int c4 in
539 let c5 = Int64.of_int c5 in
540 let c6 = Int64.of_int c6 in
541 let c7 = Int64.of_int c7 in
542 _make_int64_be c0 c1 c2 c3 c4 c5 c6 c7 in
543 Int64.shift_right_logical word (64 - flen)
545 word, off+flen, len-flen
547 let extract_int64_le_unsigned data off len flen =
548 let byteoff = off lsr 3 in
550 let strlen = String.length data in
553 (* Optimize the common (byte-aligned) case. *)
554 if off land 7 = 0 then (
556 let c0 = _get_byte64 data byteoff strlen in
557 let c1 = _get_byte64 data (byteoff+1) strlen in
558 let c2 = _get_byte64 data (byteoff+2) strlen in
559 let c3 = _get_byte64 data (byteoff+3) strlen in
560 let c4 = _get_byte64 data (byteoff+4) strlen in
561 let c5 = _get_byte64 data (byteoff+5) strlen in
562 let c6 = _get_byte64 data (byteoff+6) strlen in
563 let c7 = _get_byte64 data (byteoff+7) strlen in
564 _make_int64_le c0 c1 c2 c3 c4 c5 c6 c7 in
565 Int64.logand word (I64.mask flen)
567 (* Extract the next 64 bits, slow method. *)
569 let c0, off, len = extract_char_unsigned data off len 8 in
570 let c1, off, len = extract_char_unsigned data off len 8 in
571 let c2, off, len = extract_char_unsigned data off len 8 in
572 let c3, off, len = extract_char_unsigned data off len 8 in
573 let c4, off, len = extract_char_unsigned data off len 8 in
574 let c5, off, len = extract_char_unsigned data off len 8 in
575 let c6, off, len = extract_char_unsigned data off len 8 in
576 let c7, _, _ = extract_char_unsigned data off len 8 in
577 let c0 = Int64.of_int c0 in
578 let c1 = Int64.of_int c1 in
579 let c2 = Int64.of_int c2 in
580 let c3 = Int64.of_int c3 in
581 let c4 = Int64.of_int c4 in
582 let c5 = Int64.of_int c5 in
583 let c6 = Int64.of_int c6 in
584 let c7 = Int64.of_int c7 in
585 _make_int64_le c0 c1 c2 c3 c4 c5 c6 c7 in
586 Int64.logand word (I64.mask flen)
588 word, off+flen, len-flen
590 let extract_int64_ne_unsigned =
591 if nativeendian = BigEndian
592 then extract_int64_be_unsigned
593 else extract_int64_le_unsigned
595 (*----------------------------------------------------------------------*)
596 (* Constructor functions. *)
598 module Buffer = struct
601 mutable len : int; (* Length in bits. *)
602 (* Last byte in the buffer (if len is not aligned). We store
603 * it outside the buffer because buffers aren't mutable.
609 (* XXX We have almost enough information in the generator to
610 * choose a good initial size.
612 { buf = Buffer.create 128; len = 0; last = 0 }
614 let contents { buf = buf; len = len; last = last } =
616 if len land 7 = 0 then
619 Buffer.contents buf ^ (String.make 1 (Char.chr last)) in
622 (* Add exactly 8 bits. *)
623 let add_byte ({ buf = buf; len = len; last = last } as t) byte =
624 if byte < 0 || byte > 255 then invalid_arg "Bitmatch.Buffer.add_byte";
625 let shift = len land 7 in
627 (* Target buffer is byte-aligned. *)
628 Buffer.add_char buf (Char.chr byte)
630 (* Target buffer is unaligned. 'last' is meaningful. *)
631 let first = byte lsr shift in
632 let second = (byte lsl (8 - shift)) land 0xff in
633 Buffer.add_char buf (Char.chr (last lor first));
638 (* Add exactly 1 bit. *)
639 let add_bit ({ buf = buf; len = len; last = last } as t) bit =
640 let shift = 7 - (len land 7) in
642 (* Somewhere in the middle of 'last'. *)
643 t.last <- last lor ((if bit then 1 else 0) lsl shift)
645 (* Just a single spare bit in 'last'. *)
646 let last = last lor if bit then 1 else 0 in
647 Buffer.add_char buf (Char.chr last);
652 (* Add a small number of bits (definitely < 8). This uses a loop
653 * to call add_bit so it's slow.
655 let _add_bits t c slen =
656 if slen < 1 || slen >= 8 then invalid_arg "Bitmatch.Buffer._add_bits";
657 for i = slen-1 downto 0 do
658 let bit = c land (1 lsl i) <> 0 in
662 let add_bits ({ buf = buf; len = len } as t) str slen =
664 if len land 7 = 0 then (
665 if slen land 7 = 0 then
666 (* Common case - everything is byte-aligned. *)
667 Buffer.add_substring buf str 0 (slen lsr 3)
669 (* Target buffer is aligned. Copy whole bytes then leave the
670 * remaining bits in last.
672 let slenbytes = slen lsr 3 in
673 if slenbytes > 0 then Buffer.add_substring buf str 0 slenbytes;
674 t.last <- Char.code str.[slenbytes] lsl (8 - (slen land 7))
678 (* Target buffer is unaligned. Copy whole bytes using
679 * add_byte which knows how to deal with an unaligned
680 * target buffer, then call _add_bits for the remaining < 8 bits.
682 * XXX This is going to be dog-slow.
684 let slenbytes = slen lsr 3 in
685 for i = 0 to slenbytes-1 do
686 let byte = Char.code str.[i] in
689 _add_bits t (Char.code str.[slenbytes]) (slen - (slenbytes lsl 3))
694 (* Construct a single bit. *)
695 let construct_bit buf b _ _ =
698 (* Construct a field, flen = [2..8]. *)
699 let construct_char_unsigned buf v flen exn =
700 let max_val = 1 lsl flen in
701 if v < 0 || v >= max_val then raise exn;
703 Buffer.add_byte buf v
705 Buffer._add_bits buf v flen
707 (* Construct a field of up to 31 bits. *)
708 let construct_int_be_unsigned buf v flen exn =
709 (* Check value is within range. *)
710 if not (I.range_unsigned v flen) then raise exn;
712 I.map_bytes_be (Buffer._add_bits buf) (Buffer.add_byte buf) v flen
714 let construct_int_ne_unsigned =
715 if nativeendian = BigEndian
716 then construct_int_be_unsigned
717 else (*construct_int_le_unsigned*)
718 fun _ _ _ _ -> failwith "construct_int_le_unsigned"
720 (* Construct a field of exactly 32 bits. *)
721 let construct_int32_be_unsigned buf v flen _ =
723 (Int32.to_int (Int32.shift_right_logical v 24));
725 (Int32.to_int ((Int32.logand (Int32.shift_right_logical v 16) 0xff_l)));
727 (Int32.to_int ((Int32.logand (Int32.shift_right_logical v 8) 0xff_l)));
729 (Int32.to_int (Int32.logand v 0xff_l))
731 let construct_int32_ne_unsigned =
732 if nativeendian = BigEndian
733 then construct_int32_be_unsigned
734 else (*construct_int32_le_unsigned*)
735 fun _ _ _ _ -> failwith "construct_int32_le_unsigned"
737 (* Construct a field of up to 64 bits. *)
738 let construct_int64_be_unsigned buf v flen exn =
739 (* Check value is within range. *)
740 if not (I64.range_unsigned v flen) then raise exn;
742 I64.map_bytes_be (Buffer._add_bits buf) (Buffer.add_byte buf) v flen
744 let construct_int64_ne_unsigned =
745 if nativeendian = BigEndian
746 then construct_int64_be_unsigned
747 else (*construct_int64_le_unsigned*)
748 fun _ _ _ _ -> failwith "construct_int64_le_unsigned"
750 (* Construct from a string of bytes, exact multiple of 8 bits
751 * in length of course.
753 let construct_string buf str =
754 let len = String.length str in
755 Buffer.add_bits buf str (len lsl 3)
757 (*----------------------------------------------------------------------*)
758 (* Extract a string from a bitstring. *)
760 let string_of_bitstring (data, off, len) =
761 if off land 7 = 0 && len land 7 = 0 then
762 (* Easy case: everything is byte-aligned. *)
763 String.sub data (off lsr 3) (len lsr 3)
765 (* Bit-twiddling case. *)
766 let strlen = (len + 7) lsr 3 in
767 let str = String.make strlen '\000' in
768 let rec loop data off len i =
770 let c, off, len = extract_char_unsigned data off len 8 in
771 str.[i] <- Char.chr c;
772 loop data off len (i+1)
773 ) else if len > 0 then (
774 (* XXX Is this correct? It should write into the high bits
777 let c, off, len = extract_char_unsigned data off len len in
778 str.[i] <- Char.chr c
787 let bitstring_to_chan ((data, off, len) as bits) chan =
788 (* Fail if the bitstring length isn't a multiple of 8. *)
789 if len land 7 <> 0 then invalid_arg "bitstring_to_chan";
791 if off land 7 = 0 then
792 (* Easy case: string is byte-aligned. *)
793 output chan data (off lsr 3) (len lsr 3)
795 (* Bit-twiddling case: reuse string_of_bitstring *)
796 let str = string_of_bitstring bits in
797 output_string chan str
800 let bitstring_to_file bits filename =
801 let chan = open_out_bin filename in
803 bitstring_to_chan bits chan;
809 (*----------------------------------------------------------------------*)
810 (* Display functions. *)
813 let c = Char.code c in
816 let hexdump_bitstring chan (data, off, len) =
820 let linelen = ref 0 in
821 let linechars = String.make 16 ' ' in
823 fprintf chan "00000000 ";
826 let bits = min !len 8 in
827 let byte, off', len' = extract_char_unsigned data !off !len bits in
828 off := off'; len := len';
830 let byte = byte lsl (8-bits) in
831 fprintf chan "%02x " byte;
834 linechars.[!linelen] <-
835 (let c = Char.chr byte in
836 if isprint c then c else '.');
838 if !linelen = 8 then fprintf chan " ";
839 if !linelen = 16 then (
840 fprintf chan " |%s|\n%08x " linechars !count;
842 for i = 0 to 15 do linechars.[i] <- ' ' done
846 if !linelen > 0 then (
847 let skip = (16 - !linelen) * 3 + if !linelen < 8 then 1 else 0 in
848 for i = 0 to skip-1 do fprintf chan " " done;
849 fprintf chan " |%s|\n%!" linechars