Module Bin_prot.BlobSource

'a Blob.t is type-equivalent to 'a, but has different bin-prot serializers that prefix the representation with the size of 'a.

To understand where this is useful, imagine we have an event type where many applications look at some parts of an event, but not all applications need to deal with all parts of an event. We might define:

  type 'a event =
    { time : Time.t
    ; source : string
    ; details : 'a
    } [@@deriving bin_io]

Applications that need to understand all the details of an event could use:

 type concrete_event = Details.t Blob.t event [@@deriving bin_io]

An application that filters events to downsteam consumers based on just source or time (but doesn't need to parse details) may use:

 type opaque_event = Blob.Opaque.Bigstring.t event [@@deriving bin_io]

This has two advantages:

An application that's happy to throw away details may use:

 type ignored_event = Blob.Ignored.t event [@@deriving bin_read]

Whereas opaque_events roundtrip, ignored_events actually drop the bytes representing details when deserializing, and therefore do not roundtrip.

Sourcetype 'a id = 'a
Sourcetype 'a t = 'a
include Ppx_compare_lib.Comparable.S1 with type 'a t := 'a t
Sourceval compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int
Sourceval sexp_of_t : ('a -> Sexplib0.Sexp.t) -> 'a t -> Sexplib0.Sexp.t
include Binable.S1 with type 'a t := 'a id
Sourceval bin_shape_t : Shape.t -> Shape.t
Sourceval bin_size_t : ('a, 'a id) Size.sizer1
Sourceval bin_write_t : ('a, 'a id) Write.writer1
Sourceval bin_read_t : ('a, 'a id) Read.reader1
Sourceval __bin_read_t__ : ('a, int -> 'a id) Read.reader1
Sourceval bin_writer_t : ('a, 'a id) Type_class.S1.writer
Sourceval bin_reader_t : ('a, 'a id) Type_class.S1.reader
Sourceval bin_t : ('a, 'a id) Type_class.S1.t
Sourcemodule Opaque : sig ... end

An Opaque.Bigstring.t or Opaque.String.t is an arbitrary piece of bin-prot. The bin-prot (de-)serializers simply read/write the data, prefixed with its size.

Sourcemodule Ignored : sig ... end

An Ignored.t is an unusable value with special bin-prot converters. The reader reads the size and drops that much data from the buffer. Writing is not supported, however the size of t is kept, so bin_size_t is available.