A buffer for incremental decoding of an input stream.

An Unpack_buffer.t is a buffer to which one can feed strings, and then unpack from the buffer to produce a queue of values.

module Unpack_one : sig .. end
If unpack_one : ('value, 'partial_unpack) unpack_one, then unpack_one buf ?pos ?len ?partial_unpack must unpack at most one value of type 'value from buf starting at pos, and not using more than len characters. unpack_one must returns one the following:
  • `Ok (value, n) -- unpacking succeeded and consumed n bytes, where 0 <= n <= len. It is possible to have n = 0, e.g. for sexp unpacking, which can only tell it has reached the end of an atom when it encounters the following punctuation character, which if it is left paren, is the start of the following sexp.
  • `Not_enough_data (p, n) -- unpacking encountered a valid proper prefix of a packed value, and consumed n bytes, where 0 <= n <= len. p is a "partial unpack" that can be supplied to a future call to unpack_one to continue unpacking.
  • `Invalid_data -- unpacking encountered an invalidly packed value.
A naive unpack_one that only succeeds on a fully packed value could lead to quadratic behavior if a packed value's bytes are input using a linear number of calls to feed.
type ('value, 'partial_unpack) t = ?partial_unpack:'partial_unpack ->
?pos:int ->
?len:int ->
Bigstring.t ->
[ `Invalid_data of Error.t
| `Not_enough_data of 'partial_unpack * int
| `Ok of 'value * int ]
val map : ('a, 'partial_unpack) t -> f:('a -> 'b) -> ('b, 'partial_unpack) t
val create_bin_prot : 'a Bin_prot.Type_class.reader -> ('a, unit) t
create_bin_prot reader returns an unpacker that reads the "size-prefixed" bin_prot encoding, in which a value is encoded by first writing the length of the bin_prot data as a 64-bit int, and then writing the data itself. This encoding makes it trivial to know if enough data is available in the buffer, so there is no need to represent partially unpacked values, and hence 'partial_unpack = unit.
type partial_sexp
Beware that when unpacking sexps, one cannot tell if one is at the end of an atom until one hits punctuation. So, one should always feed a space (" ") to a sexp unpack buffer after feeding a batch of complete sexps, to ensure that the final sexp is unpacked.
val sexp : (Std_internal.Sexp.t, partial_sexp) t
type ('value, 'partial_unpack) t
val invariant : ('a, 'b) t -> unit
val create : ?partial_unpack:'partial_unpack ->
('value, 'partial_unpack) Unpack_one.t -> ('value, 'partial_unpack) t
val create_bin_prot : 'a Bin_prot.Type_class.reader -> ('a, unit) t
create_bin_prot reader returns an unpack buffer that unpacks the "size-prefixed" bin_prot encoding, in which a value is encoded by first writing the length of the bin_prot data as a 64-bit int, and then writing the bin_prot data itself. This encoding makes it trivial to know if enough data is available in the buffer, so there is no need to represent partially unpacked values, and hence 'partial_unpack = unit.
val is_empty : ('a, 'b) t -> bool Or_error.t
is_empty t returns true if t has no unconsumed bytes, and false if it does. is_empty returns an error if t has encountered an unpacking error.
val feed : ?pos:int -> ?len:int -> ('a, 'b) t -> Bigstring.t -> unit Or_error.t
feed t buf ?pos ?len adds the specified substring of buf to t's buffer. It returns an error if t has encountered an unpacking error.
val feed_string : ?pos:int -> ?len:int -> ('a, 'b) t -> string -> unit Or_error.t
val unpack : ('value, 'a) t -> 'value Std_internal.Queue.t Or_error.t
unpack t unpacks all the values that it can from t. The resulting queue will be empty if nothing could be unpacked. If there is an unpacking error, unpack returns an error, and subsequent feed and unpack operations on t will return that same error. I.e. no more data can be fed to or unpacked from t.
val debug : bool ref
debug controls whether invariants are checked at each call. Setting this to true can make things very slow.
val sexp_of_t : ('value -> Sexplib.Sexp.t) ->
('partial_unpack -> Sexplib.Sexp.t) ->
('value, 'partial_unpack) t -> Sexplib.Sexp.t