* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
- * version 2 of the License, or (at your option) any later version.
+ * version 2 of the License, or (at your option) any later version,
+ * with the OCaml linking exception described in COPYING.LIB.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
a {!endian} type, ie. [LittleEndian], [BigEndian] or [NativeEndian].
The expression is an arbitrary OCaml expression and can use the
value of earlier fields in the bitmatch.
+ - [offset (expr)]: see {{:#computedoffsets}computed offsets} below.
- The default settings are [int], [unsigned], [bigendian].
+ The default settings are [int], [unsigned], [bigendian], no offset.
Note that many of these qualifiers cannot be used together,
eg. bitstrings do not have endianness. The syntax extension should
still need to be a runtime check to enforce the
size).
+ {2:computedoffsets Computed offsets}
+
+ You can add an [offset(..)] qualifier to bitmatch patterns in order
+ to move the current offset within the bitstring forwards.
+
+ For example:
+
+{[
+bitmatch bits with
+| { field1 : 8;
+ field2 : 8 : offset(160) } -> ...
+]}
+
+ matches [field1] at the start of the bitstring and [field2]
+ at 160 bits into the bitstring. The middle 152 bits go
+ unmatched (ie. can be anything).
+
+ The generated code is efficient. If field lengths and offsets
+ are known to be constant at compile time, then almost all
+ runtime checks are avoided. Non-constant field lengths and/or
+ non-constant offsets can result in more runtime checks being added.
+
+ Note that moving the offset backwards, and moving the offset in
+ [BITSTRING] constructors, are both not supported at present.
+
{2 Named patterns and persistent patterns}
Please see {!Bitmatch_persistent} for documentation on this subject.
{v
ocamlc -I +bitmatch \
- -pp "camlp4o bitmatch.cma bitmatch_persistent.cma \
+ -pp "camlp4of bitmatch.cma bitmatch_persistent.cma \
`ocamlc -where`/bitmatch/pa_bitmatch.cmo" \
- bitmatch.cma test.ml -o test
+ unix.cma bitmatch.cma test.ml -o test
v}
Simpler method using findlib:
{v
ocamlfind ocamlc \
- -package bitmatch.syntax -syntax bitmatch.syntax \
+ -package bitmatch,bitmatch.syntax -syntax bitmatch.syntax \
-linkpkg test.ml -o test
v}
location of the [BITSTRING] constructor that failed.
*)
-(** {3 Bitstrings} *)
+(** {3 Bitstring manipulation} *)
+
+val bitstring_length : bitstring -> int
+(** [bitstring_length bitstring] returns the length of
+ the bitstring in bits.
+
+ Note this just returns the third field in the {!bitstring} tuple. *)
+
+val subbitstring : bitstring -> int -> int -> bitstring
+(** [subbitstring bits off len] returns a sub-bitstring
+ of the bitstring, starting at offset [off] bits and
+ with length [len] bits.
+
+ If the original bitstring is not long enough to do this
+ then the function raises [Invalid_argument "subbitstring"].
+
+ Note that this function just changes the offset and length
+ fields of the {!bitstring} tuple, so is very efficient. *)
+
+val dropbits : int -> bitstring -> bitstring
+(** Drop the first n bits of the bitstring and return a new
+ bitstring which is shorter by n bits.
+
+ If the length of the original bitstring is less than n bits,
+ this raises [Invalid_argument "dropbits"].
+
+ Note that this function just changes the offset and length
+ fields of the {!bitstring} tuple, so is very efficient. *)
+
+val takebits : int -> bitstring -> bitstring
+(** Take the first n bits of the bitstring and return a new
+ bitstring which is exactly n bits long.
+
+ If the length of the original bitstring is less than n bits,
+ this raises [Invalid_argument "takebits"].
+
+ Note that this function just changes the offset and length
+ fields of the {!bitstring} tuple, so is very efficient. *)
+
+(** {3 Constructing bitstrings} *)
val empty_bitstring : bitstring
(** [empty_bitstring] is the empty, zero-length bitstring. *)
For example, [make_bitstring 16 '\x5a'] will create
the bitstring [0x5a5a] or in binary [0101 1010 0101 1010].
- Note that the length is in bits, not bytes. *)
+ Note that the length is in bits, not bytes. The length does NOT
+ need to be a multiple of 8. *)
+
+val zeroes_bitstring : int -> bitstring
+(** [zeroes_bitstring] creates an [n] bit bitstring of all 0's.
+
+ Actually this is the same as {!create_bitstring}. *)
+
+val ones_bitstring : int -> bitstring
+(** [ones_bitstring] creates an [n] bit bitstring of all 1's. *)
val bitstring_of_string : string -> bitstring
(** [bitstring_of_string str] creates a bitstring
[max] bytes from the channel (or fewer if the end of input
occurs before that). *)
-val bitstring_length : bitstring -> int
-(** [bitstring_length bitstring] returns the length of
- the bitstring in bits. *)
+(** {3 Converting bitstrings} *)
val string_of_bitstring : bitstring -> string
(** [string_of_bitstring bitstring] converts a bitstring to a string
val construct_int64_ee_unsigned : endian -> Buffer.t -> int64 -> int -> exn -> unit
val construct_string : Buffer.t -> string -> unit
+
+val construct_bitstring : Buffer.t -> bitstring -> unit
git.annexia.org / ocaml-bitstring.git / blobdiff