package frama-c

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package frama-c
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Provides a function input_val, similar in functionality to the standard library function Marshal.from_channel. The main difference with Marshal.from_channel is that input_val is able to apply transformation functions on the values on the fly as they are read from the input channel.

Because it has an abstract representation of the type, input_val is able to catch some inconsistencies that Marshal.from_channel cannot. It is therefore "more" type-safe, but only if it is always used in conditions where the static type attributed to the result by the type-checker agrees with the representation of the type passed as second argument to input_val. No such verification is done by this module (this would require changes to the compiler).

The sanity checks are not the primary purpose of input_val, and it is possible for a bug where the representation of a value of the wrong type is passed to input_val to go undetected, just as this can happen with Marshal.from_channel.

type t =
  1. | Abstract
  2. | Structure of structure
  3. | Transform of t * Obj.t -> Obj.t
  4. | Return of t * unit -> Obj.t
  5. | Dynamic of unit -> t
and structure =
  1. | Sum of t array array
  2. | Dependent_pair of t * Obj.t -> t
  3. | Array of t

Type t is used to describe the type of the data to be read and the transformations to be applied to the data.

Abstract is used to input a value without any checking or transformation (as Marshal.from_channel does). In this case, you don't need to provide a precise description of the representation of the data.

Structure a is used to provide a description of the representation of the data, along with optional transformation functions for parts of the data.

a can be:

  • Array(t), indicating that the data is an array of values of the same type, each value being described by t.
  • Sum(c) for describing a non-array type where c is an array describing the non-constant constructors of the type being described (in the order of their declarations in that type). Each element of this latter array is an array of t that describes (in order) the fields of the corresponding constructor.
  • Dependent_pair(e,f) for instructing the unmarshaler to reconstruct the first component of a pair first, using e as its description, and to apply function f to this value in order to get the description of the pair's second component.

The shape of a must match the shape of the representation of the type of the data being imported, or input_val may report an error when the data doesn't match the description.

Transform (u, f) is used to specify a transformation function on the data described by u. input_val will read and rebuild the data as described by u, then call f on that data and return the result returned by f.

Return (u, f) is the same as Transform, except that the data is not rebuilt, and () is passed to f instead of the data. This is to be used when the transformation functions of u rebuild the data by side effects and the version rebuilt by input_val is irrelevant.

Dynamic f is used to build a new description on the fly when a new data of the current type is encountered.

val input_val : in_channel -> t -> 'a

input_val c t Read a value from the input channel c, applying the transformations described by t.

val null : Obj.t

recursive values cannot be completely formed at the time they are passed to their transformation function. When traversing a recursive value, the transformation function must check the fields for physical equality to null (with the function ==) and avoid using any field that is equal to null.

val id : Obj.t -> Obj.t

Use this function when you don't want to change the value unmarshaled by input_val. You can also use your own identity function, but using this one is more efficient.

Convenience functions for describing transformations.

val t_unit : t
val t_int : t
val t_string : t
val t_float : t
val t_bool : t
val t_int32 : t
val t_int64 : t
val t_nativeint : t
val t_record : t array -> t
val t_tuple : t array -> t
val t_list : t -> t
val t_ref : t -> t
val t_option : t -> t
val t_array : t -> t
val t_queue : t -> t
val t_hashtbl_unchangedhashs : t -> t -> t
val t_hashtbl_changedhashs : (int -> 'table) -> ('table -> 'key -> 'value -> unit) -> t -> t -> t
val t_set_unchangedcompares : t -> t
val t_map_unchangedcompares : t -> t -> t

Functions for writing deserializers.

val register_custom : string -> (in_channel -> Obj.t) -> unit
val arch_sixtyfour : bool
val arch_bigendian : bool
val getword : in_channel -> Int32.t
val read8s : in_channel -> int
val read16s : in_channel -> int
val read32s : in_channel -> int
val read64s : in_channel -> int
val read8u : in_channel -> int
val read16u : in_channel -> int
val read32u : in_channel -> int
val read64u : in_channel -> int
val readblock : in_channel -> Obj.t -> int -> int -> unit
val readblock_rev : in_channel -> Obj.t -> int -> int -> unit
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