module Xdr:sig..end
XDR values must be formed according to an XDR type. Such types are usually written in a notation that is close to the C notation of structured types. There are some important details where XDR is better than C:
*t is allowed, but means something
   different, namely "t option" in O'Caml notation.     struct *list {
       int value;
       next list;
     }
        type intlist = intlist_el option
      and intlist_el = { value : int; next : intlist }
   This module defines:
A "type system" is a collection of several types that have names and that can refer to previously defined types (i.e. a sequence of "typedef"s). As with simple types, there is an extensive and an opaque representation.
 A typical way of using this module is to define an "XDR type term system"
 by simply writing an O'Caml expression. After that, this system is validated
 and you get the "type system". From now on, you can refer to the types
 defined in the system by name and get the corresponding "XDR types".
 Once you have an XDR type you can use it to pack or unpack an XDR value.
Terms that describe possible XDR types:
X_int:                      integer (32 bit)X_uint:                     unsigned integerX_hyper:                    hyper (64 bit signed integer)X_uhyper:                   unsigned hyperX_enum [x1,i1; ...]:        enum { x1 = i1, ... }X_float:                    float (32 bit fp number)X_double:                   double (64 bit fp number)X_opaque_fixed n:           opaque[n]X_opaque n:                 opaque<n>X_string n:                 string<n>X_mstring(name,n):          _managed string<n> (see below)X_array_fixed (t,n):        t[n]X_array (t,n):              t<n>X_struct [x1,t1;...]:       struct { t1 x1; ...}X_union_over_int
     ([n1,t1;...], None):       union switch(int) {case n1: t1; ...}X_union_over_int
     ([n1,t1;...], Some t):     union switch(int) {case n1: t1; ...; default t}X_union_over_uint
     ([n1,t1;...], None):       union switch(unsigned int) {case n1: t1; ...}X_union_over_uint
     ([n1,t1;...], Some t):     union switch(unsigned int)
                                 {case n1: t1; ...; default t}X_union_over_enum
     (e, [n1,t1;...], None):    union switch(e) {case n1:t1; ...}
                                 where e is an enumeration typeX_union_over_enum
     (e, [n1,t1;...], Some t):  union switch(e) {case n1:t1; ...; default t}
                                 where e is an enumeration typeX_void:                     voidX_type constructor is only useful for types interpreted relative to
 a type system. Then it refers to a named type in this system.
 The X_param constructor includes a reference to an arbitrary type
 which must first be given when packing or unpacking values.
 (A "lazy" type reference.) Additionally, the values for parameters
 may be encrypted or decrypted.
Example how to define a recursive type:
 X_rec ("a", X_array ( X_struct ["value", X_int; "next", X_refer "a"], 1))
 Managed strings are represented as X_mstring(name,n). The name refers
 to the preferred factory for managed strings (needs to be passed to the
 XDR unpacker). Values for managed strings are objects of type
 Xdr_mstring.mstring.
 The term X_direct(t,read,write,size) is generated by ocamlrpcgen at 
 positions
 suitable for direct mapping. In this case, the XDR byte representation is
 directly mapped to the final Ocaml value bypassing the intermediate
 representation defined in this module. t is the mapped type. The
 function read is called as read s cursor len in order to map the
 XDR bytes at !cursor in s. The cursor must be advanced to the
 end position. len is the number of valid bytes in s (i.e. s.(len-1)
 is the last one). The result of read is an arbitrary exception which
 needs to be postprocessed by ocamlrpcgen-generated code. The function
 write is called as write x s cursor: The value encapsulated in
 exception x is written to string s at position cursor. Like for
 read the cursor is advanced by the number of written bytes. There
 must be enough space in s. The function size can be used to determine
 the number of written bytes beforehand.
type | | | X_int | 
| | | X_uint | 
| | | X_hyper | 
| | | X_uhyper | 
| | | X_enum of  | 
| | | X_float | 
| | | X_double | 
| | | X_opaque_fixed of  | 
| | | X_opaque of  | 
| | | X_string of  | 
| | | X_mstring of  | 
| | | X_array_fixed of  | 
| | | X_array of  | 
| | | X_struct of  | 
| | | X_union_over_int of  | 
| | | X_union_over_uint of  | 
| | | X_union_over_enum of  | 
| | | X_void | 
| | | X_type of  | 
| | | X_param of  | 
| | | X_rec of  | 
| | | X_refer of  | 
| | | X_direct of  | 
type 
xdr_type_term. Note that it does not
 contain X_type constructors, i.e. is completely expanded.
 It is allowed that an xdr_type contains X_param constructors (parameters).
 The set of occurring parameters can be determined very quickly for an
 xdr_type.typexdr_type_term_system =(string * xdr_type_term) list
n must be defined
 in the list before it can be used via X_type n.
 It is possible to use this module without the means of type
 systems, but often code is more readable if types are defined
 in an environment allowing bindings to names.type 
val x_bool : xdr_type_termxv_true and xv_false.val x_optional : xdr_type_term -> xdr_type_termxv_none and
 xv_some v.val x_opaque_max : xdr_type_termval x_string_max : xdr_type_termval x_mstring_max : string -> xdr_type_termval x_array_max : xdr_type_term -> xdr_type_termtype | | | XV_int of  | |||
| | | XV_uint of  | |||
| | | XV_hyper of  | |||
| | | XV_uhyper of  | |||
| | | XV_enum of  | |||
| | | XV_float of  | |||
| | | XV_double of  | |||
| | | XV_opaque of  | |||
| | | XV_string of  | |||
| | | XV_array of  | |||
| | | XV_struct of  | |||
| | | XV_union_over_int of  | |||
| | | XV_union_over_uint of  | |||
| | | XV_union_over_enum of  | |||
| | | XV_void | |||
| | | XV_enum_fast of  | (* | The integer is the _position_ in the X_enumlist, sorted by
 enum values (ascending). For example, if we haveX_enum [ "A", 4; "B", 2; "C", 6 ]the element "B" has the position 0, because 2 is the lowest
 number | *) | 
| | | XV_struct_fast of  | (* | The array elements are in the same order as declared in X_struct | *) | 
| | | XV_union_over_enum_fast of  | (* | The integer is the _position_ in the X_enumlist. "position"
 means the same as forXV_enum_fast | *) | 
| | | XV_array_of_string_fast of  | (* | To be used with an X_arrayorX_array_fixedwith an inner
          type ofX_string | *) | 
| | | XV_mstring of  | |||
| | | XV_direct of  | 
val xv_true : xdr_valueval xv_false : xdr_valuex_boolval xv_none : xdr_valueval xv_some : xdr_value -> xdr_valuex_optionalexception Dest_failure
val dest_xv_int : xdr_value -> Rtypes.int4val dest_xv_uint : xdr_value -> Rtypes.uint4val dest_xv_hyper : xdr_value -> Rtypes.int8val dest_xv_uhyper : xdr_value -> Rtypes.uint8val dest_xv_enum : xdr_value -> stringval dest_xv_enum_fast : xdr_value -> intval dest_xv_float : xdr_value -> Rtypes.fp4val dest_xv_double : xdr_value -> Rtypes.fp8val dest_xv_opaque : xdr_value -> stringval dest_xv_string : xdr_value -> stringval dest_xv_mstring : xdr_value -> Xdr_mstring.mstringval dest_xv_array : xdr_value -> xdr_value arrayval dest_xv_array_of_string_fast : xdr_value -> string arrayval dest_xv_struct : xdr_value -> (string * xdr_value) listval dest_xv_struct_fast : xdr_value -> xdr_value arrayval dest_xv_union_over_int : xdr_value -> Rtypes.int4 * xdr_valueval dest_xv_union_over_uint : xdr_value -> Rtypes.uint4 * xdr_valueval dest_xv_union_over_enum : xdr_value -> string * xdr_valueval dest_xv_union_over_enum_fast : xdr_value -> int * xdr_valueval dest_xv_void : xdr_value -> unitval map_xv_enum_fast : xdr_type -> xdr_value -> int32XV_enum and XV_enum_fastval map_xv_struct_fast : xdr_type -> xdr_value -> xdr_value arrayXV_struct and XV_struct_fastval map_xv_union_over_enum_fast : xdr_type -> xdr_value -> int * int32 * xdr_valueXV_union_over_enum and XV_union_over_enum_fast.
 Returns the triple (k,i,x):k: Position of the selected value in the T_enum arrayi: value of the enumx: selected arm of the unionexception Xdr_format of string
exception Xdr_format_message_too_long of xdr_value
exception Xdr_failure of string
val validate_xdr_type : xdr_type_term -> xdr_typeval validate_xdr_type_system : xdr_type_term_system -> xdr_type_systemval params : xdr_type -> string listX_param parameters contained in the type
X_type constructions are always resolvedval xdr_type_term : xdr_type -> xdr_type_termval xdr_type_term_system : xdr_type_system -> xdr_type_term_systemexpanded_xdr_type sys1 (X_type "xy")
 extracts the type called "xy" defined in sys1.
 Expansion removes all X_type constructions in a type term.val expanded_xdr_type : xdr_type_system -> xdr_type_term -> xdr_typeval expanded_xdr_type_term : xdr_type_term_system -> xdr_type_term -> xdr_type_termval are_compatible : xdr_type -> xdr_type -> boolare_compatible: currently not implementedval value_matches_type : xdr_value -> xdr_type -> (string * xdr_type) list -> bool
 Encrypted parameters are not supported here.
pack_xdr_value v t p print: Serialize v into a string conforming to
   the XDR standard where v matches t. In p the parameter instances are
   given. All parameters must be given, and the parameters must not contain
   parameters themselves. The fourth argument, print, is a function
   which is evaluated for the pieces of the resultant string. You can use
   pack_xdr_value_as_string to get the whole string at once.
 unpack_xdr_value s t p: Unserialize a string to a value
   matching t. If this operation fails you get an Xdr_format
   exception explaining what the reason for the failure is.
   Mostly the cause for failures is that t isn't the type
   of the value.
   Note that there are some implementation restrictions limiting
   the number of elements in array, strings and opaque fields.
   If you get such an error this normally still means that
   the value is not of the expected type, because these limits
   have no practical meaning (they are still higher than the
   usable address space).
Encryption: The encode and decode functions can be used
 to encrypt/decrypt parameters (placeholders in the type marked with
 X_param pname for a parameter name pname). The encode argument
 may list for each parameter an encoding function:
 encode = [ pname1, encoder1; pname2, encoder2; ... ] 
 The functions encoder are called with the XDR-packed parameter value,
 and return the encrypted value.
 Likewise, the decode argument may list for each parameter a decoding
 function:
 decode = [ pname1, decoder1; pname2, decoder2; ... ] The call style of the decoder functions is a bit more complicated, though. They are called as
 let (xdr_s, n) = decoder s pos len 
 meaning that the decoder starts decoding at position pos of string s,
 and that at most len bytes can be decoded. It returns the decoded
 string xdr_s (which is then unpacked), and in n the number of
 consumed input bytes is returned.
 Exceptions raised in encoders or decoders fall through unmodified.
typeencoder =Xdr_mstring.mstring list -> Xdr_mstring.mstring list
typedecoder =string -> int -> int -> string * int
val pack_xdr_value : ?encode:(string * encoder) list ->
       xdr_value ->
       xdr_type -> (string * xdr_type) list -> (string -> unit) -> unitval pack_xdr_value_as_string : ?rm:bool ->
       ?encode:(string * encoder) list ->
       xdr_value -> xdr_type -> (string * xdr_type) list -> string
      Changed in Ocamlnet-3.3: these functions raise Xdr_failure in
      case of errors.
val pack_xdr_value_as_mstrings : ?encode:(string * encoder) list ->
       xdr_value ->
       xdr_type -> (string * xdr_type) list -> Xdr_mstring.mstring list
      Changed in Ocamlnet-3.3: this function raises Xdr_failure in
      case of errors.
typexdr_value_version =[ `Ocamlrpcgen | `V1 | `V2 | `V3 | `V4 ]
xdr_value is returned by unpack_xdr_value.
      During the development of Ocamlnet several incompatible changes were
      made, but by selecting a certain version these changes can be hidden
      from the caller.
`V1: This version refers to the original xdr_value definition,
        which only included XV_int, XV_uint, XV_hyper, XV_uhyper,
        XV_enum, XV_float, XV_double, XV_opaque, XV_string,
        XV_array, XV_struct, XV_union_over_int, XV_union_over_uint,
        XV_union_over_enum, and XV_void.`V2: This version is available since the rpc-0.4 distribution,
        and added the tags XV_enum_fast, XV_struct_fast, and
        XV_union_over_enum_fast.`V3: In Ocamlnet-3.0 the tag XV_array_of_string_fast was added.`V4: In Ocamlnet-3.5 the tag XV_direct was added.`Ocamlrpcgen: This refers to the version that must be used if the
        returned xdr_value is processed by code generated with ocamlrpcgen.`V1, for ultimate backward compatibility.
      The switch fast=true selects `Ocamlrpcgen (it was always used
      for this purpose, despite its name).val unpack_xdr_value : ?pos:int ->
       ?len:int ->
       ?fast:bool ->
       ?prefix:bool ->
       ?mstring_factories:Xdr_mstring.named_mstring_factories ->
       ?xv_version:xdr_value_version ->
       ?decode:(string * decoder) list ->
       string -> xdr_type -> (string * xdr_type) list -> xdr_valueval unpack_xdr_value_l : ?pos:int ->
       ?len:int ->
       ?fast:bool ->
       ?prefix:bool ->
       ?mstring_factories:Xdr_mstring.named_mstring_factories ->
       ?xv_version:xdr_value_version ->
       ?decode:(string * decoder) list ->
       string -> xdr_type -> (string * xdr_type) list -> xdr_value * intprefix: whether it is ok that the string is longer than the message
   (default: false)
 mstring_factories: when a T_mstring(name,_) type is found, the
 factory is looked up in this hash table under name, and if this
 fails under the name "*". If there is no such
 factory, unpacking fails! (Default: empty table.)
 xv_version: Selects a certain version of the returned xdr_value
 terms. See Xdr.xdr_value_version for details. Set this to
 `Ocamlrpcgen if you decode the xdr_value with ocamlrpcgen-generated
 decoders.
 fast: Setting this to true is a deprecated way to set
 xv_version=`Ocamlrpcgen.
 The variant unpack_xdr_value_l returns not only the decoded value,
 but also the actual length in bytes.
 The exceptions Xdr_format and Xdr_format_message_too_long may
 be raised.