package cstruct

  1. Overview
  2. Docs
Access C-like structures directly from OCaml

Install

Dune Dependency

Authors

Maintainers

Sources

cstruct-6.2.0.tbz
sha256=9a78073392580e8349148fa3ab4b1b2e989dc9d30d07401b04c96b7c60f03e62
sha512=8d33fe6b3707a3994d0225cd33cadde0bb2ca834ef01096e3df33a08e4a8c6d02ebccddf558a73988b8a5595b65fdc10de61efbf872c6c9e55c719c7e19c463d

Description

Cstruct is a library and syntax extension to make it easier to access C-like structures directly from OCaml. It supports both reading and writing to these structures, and they are accessed via the Bigarray module.

Tags

org:mirage org:ocamllabs

Published: 14 Mar 2023

README

Cstruct - access C-like structures directly from OCaml

Cstruct is a library and syntax extension to make it easier to access C-like structures directly from OCaml. It supports both reading and writing to these structures, and they are accessed via the Bigarray module.

Installation

This repository provides several packages that can be installed via the opam package manager:

  • cstruct: the core Cstruct library

  • cstruct-sexp: serialisers into s-expression format of Cstructs

  • cstruct-unix: provide Unix variations of the read/write functions using file descriptors

  • cstruct-async: provide Async Pipe and Bigstring support

  • cstruct-lwt: provide Lwt variants of read/write functions

  • ppx_cstruct: a PPX syntax extension (see below)

The libraries depend on OCaml version 4.08.0 and later, since it provides a ppx extension point. The old camlp4 syntax extension is nolonger available; the last cstruct release which contained it was v1.9.0.

Local development

You can build the library via dune, using make or dune build directly. Since everything is built via dune, you can also place this repository within a wider dune workspace in order to make local modifications across repositories.

Documentation

A documentation of the last version of cstruct is available here.

Usage

PPX

The PPX processor is used by passing the OCaml source code through the ppx_cstruct binary. An example pcap description is:

[%%cstruct
type pcap_header = {
  magic_number: uint32_t;   (* magic number *)
  version_major: uint16_t;  (* major version number *)
  version_minor: uint16_t;  (* minor version number *)
  thiszone: uint32_t;       (* GMT to local correction *)
  sigfigs: uint32_t;        (* accuracy of timestamps *)
  snaplen: uint32_t;        (* max length of captured packets, in octets *)
  network: uint32_t;        (* data link type *)
} [@@little_endian]]

[%%cstruct
type pcap_packet = {
  ts_sec: uint32_t;         (* timestamp seconds *)
  ts_usec: uint32_t;        (* timestamp microseconds *)
  incl_len: uint32_t;       (* number of octets of packet saved in file *)
  orig_len: uint32_t;       (* actual length of packet *)
} [@@little_endian]]

[%%cstruct
type ethernet = {
  dst: uint8_t [@len 6];
  src: uint8_t [@len 6];
  ethertype: uint16_t;
} [@@big_endian]]

[%%cstruct
type ipv4 = {
  hlen_version: uint8_t;
  tos: uint8_t;
  len: uint16_t;
  id: uint16_t;
  off: uint16_t;
  ttl: uint8_t;
  proto: uint8_t;
  csum: uint16_t;
  src: uint8_t [@len 4];
  dst: uint8_t [@len 4];
} [@@big_endian]]

This auto-generates generates functions of the form below in the ml file:

let sizeof_pcap_packet = 16
let get_pcap_packet_ts_sec v = Cstruct.LE.get_uint32 v 0
let set_pcap_packet_ts_sec v x = Cstruct.LE.set_uint32 v 0 x
let get_pcap_packet_ts_usec v = Cstruct.LE.get_uint32 v 4
let set_pcap_packet_ts_usec v x = Cstruct.LE.set_uint32 v 4 x
let get_pcap_packet_incl_len v = Cstruct.LE.get_uint32 v 8
let set_pcap_packet_incl_len v x = Cstruct.LE.set_uint32 v 8 x
let get_pcap_packet_orig_len v = Cstruct.LE.get_uint32 v 12
let set_pcap_packet_orig_len v x = Cstruct.LE.set_uint32 v 12 x

let sizeof_ethernet = 14
let get_ethernet_dst src = Cstruct.sub src 0 6
let copy_ethernet_dst src = Cstruct.copy src 0 6
let set_ethernet_dst src srcoff dst =
  Cstruct.blit_from_string src srcoff dst 0 6
let blit_ethernet_dst src srcoff dst = Cstruct.blit src srcoff dst 0 6
let get_ethernet_src src = Cstruct.sub src 6 6
let copy_ethernet_src src = Cstruct.copy src 6 6
let set_ethernet_src src srcoff dst =
  Cstruct.blit_from_string src srcoff dst 6 6
let blit_ethernet_src src srcoff dst = Cstruct.blit src srcoff dst 6 6
let get_ethernet_ethertype v = Cstruct.BE.get_uint16 v 12
let set_ethernet_ethertype v x = Cstruct.BE.set_uint16 v 12 x

The mli file will have signatures of this form:

val sizeof_pcap_packet : int
val get_pcap_packet_ts_sec : Cstruct.t -> Cstruct.uint32
val set_pcap_packet_ts_sec : Cstruct.t -> Cstruct.uint32 -> unit
val get_pcap_packet_ts_usec : Cstruct.t -> Cstruct.uint32
val set_pcap_packet_ts_usec : Cstruct.t -> Cstruct.uint32 -> unit
val get_pcap_packet_incl_len : Cstruct.t -> Cstruct.uint32
val set_pcap_packet_incl_len : Cstruct.t -> Cstruct.uint32 -> unit
val get_pcap_packet_orig_len : Cstruct.t -> Cstruct.uint32
val set_pcap_packet_orig_len : Cstruct.t -> Cstruct.uint32 -> unit
val hexdump_pcap_packet_to_buffer : Buffer.t -> pcap_packet -> unit
val hexdump_pcap_packet : Cstruct.t -> unit

val sizeof_ethernet : int
val get_ethernet_dst : Cstruct.t -> Cstruct.t
val copy_ethernet_dst : Cstruct.t -> string
val set_ethernet_dst : string -> int -> Cstruct.t -> unit
val blit_ethernet_dst : Cstruct.t -> int -> Cstruct.t -> unit
val get_ethernet_src : Cstruct.t -> Cstruct.t
val copy_ethernet_src : Cstruct.t -> string
val set_ethernet_src : string -> int -> Cstruct.t -> unit
val blit_ethernet_src : Cstruct.t -> int -> Cstruct.t -> unit
val get_ethernet_ethertype : Cstruct.t -> Cstruct.uint16
val set_ethernet_ethertype : Cstruct.t -> Cstruct.uint16 -> unit
val hexdump_ethernet_to_buffer : Buffer.t -> Cstruct.t -> unit
val hexdump_ethernet : Cstruct.t -> unit

The hexdump functions above are convenient pretty-printing functions to help you debug, and aren't intended to be high performance.

You can also declare C-like enums:

[%%cenum
type foo32 =
  | ONE32
  | TWO32 [@id 0xfffffffel]
  | THREE32
  [@@uint32_t]
]

[%%cenum
type bar16 =
  | ONE [@id 1]
  | TWO
  | FOUR [@id 4]
  | FIVE
  [@@uint16_t]
]

This generates signatures of the form:

type foo32 = | ONE32 | TWO32 | THREE32
val int_to_foo32 : int32 -> foo32 option
val foo32_to_int : foo32 -> int32
val foo32_to_string : foo32 -> string
val string_to_foo32 : string -> foo32 option
val compare_foo32 : foo32 -> foo32 -> int
type bar16 = | ONE | TWO | FOUR | FIVE
val int_to_bar16 : int -> bar16 option
val bar16_to_int : bar16 -> int
val bar16_to_string : bar16 -> string
val string_to_bar16 : string -> bar16 option
val compare_bar16 : bar16 -> bar16 -> int

Comparisons will be done relatively to the constructor ids.

You can also add a (sexp) decorator to output s-expression convertors for use with the sexplib library.

[%%cenum
type foo64 =
  | ONE64
  | TWO64
  | THREE64
  [@@uint64_t] [@@sexp]
]

And sexp_of_foo64 and foo64_of_sexp functions will also be available. The representation of the Sexp is the string representation of the enum.

If you do use the sexp decorator, then you will also need to add sexplib to the dependency list for your package (both in the dune file and the opam file).

Please see the ppx_test/ directory for more in-depth examples.

Dependencies (3)

  1. fmt >= "0.8.9"
  2. dune >= "2.0.0"
  3. ocaml >= "4.08.0"

Dev Dependencies (2)

  1. crowbar with-test
  2. alcotest with-test

  1. albatross >= "1.4.3" & < "2.3.0"
  2. arp
  3. asn1-combinators = "0.2.6"
  4. async_unix >= "v0.17.0"
  5. awa
  6. awa-mirage
  7. bip32
  8. builder < "0.4.0"
  9. builder-web < "0.2.0"
  10. capnp-rpc-net
  11. capnp-rpc-unix >= "2.1"
  12. carton >= "0.4.3" & < "1.0.0"
  13. carton-git
  14. carton-lwt < "1.0.0"
  15. certify < "0.3.3"
  16. chamelon
  17. charrua
  18. charrua-client
  19. charrua-server
  20. coap
  21. coap-core
  22. coap-server-lwt
  23. cohttp-mirage
  24. colombe < "0.2.0"
  25. conduit-mirage
  26. conex < "0.10.0"
  27. conex-mirage-crypto
  28. cowabloga
  29. crc
  30. cstruct-async
  31. cstruct-lwt >= "6.2.0"
  32. cstruct-sexp >= "6.2.0"
  33. cstruct-unix >= "6.2.0"
  34. current-albatross-deployer
  35. current_git >= "0.6.2"
  36. current_github
  37. current_web
  38. dbase4
  39. depyt
  40. dirsp-proscript
  41. dns >= "6.3.0" & < "9.1.0"
  42. dns-cli < "9.1.0"
  43. dns-client < "7.0.3"
  44. dns-forward
  45. dns-mirage
  46. dns-server
  47. dns-stub
  48. dns-tsig < "9.1.0"
  49. dnssd
  50. dnssec < "9.1.0"
  51. dream
  52. eio
  53. eqaf >= "0.8" & < "0.10"
  54. eqaf-cstruct
  55. ethernet
  56. fat-filesystem = "0.13.0" | >= "0.15.0"
  57. frenetic
  58. geojsone >= "0.2.0"
  59. git < "3.6.0" | >= "3.15.0"
  60. git-cohttp
  61. git-cohttp-unix
  62. git-mirage
  63. git-unix >= "3.2.0"
  64. github-hooks
  65. gluten-mirage < "0.5.2"
  66. gpt
  67. h2-mirage
  68. hacl-star >= "0.7.0"
  69. hex >= "1.4.0"
  70. hkdf
  71. http-multipart-formdata >= "3.1.0"
  72. httpun-mirage
  73. httpun-ws-mirage
  74. hvsock
  75. io-page
  76. io-page-unix
  77. ipaddr-cstruct
  78. irmin-git
  79. irmin-indexeddb
  80. jose < "0.10.0"
  81. key-parsers >= "1.2.1"
  82. launchd
  83. learn-ocaml-client
  84. ledgerwallet >= "0.2.1"
  85. letsencrypt < "1.0.0"
  86. letsencrypt-app < "1.0.0"
  87. lt-code
  88. macaddr-cstruct
  89. mbr-format
  90. memtrace_viewer < "v0.15.0"
  91. mimic >= "0.0.4"
  92. mirage-block >= "2.0.1"
  93. mirage-block-ccm
  94. mirage-block-combinators >= "3.0.2"
  95. mirage-block-ramdisk
  96. mirage-block-solo5
  97. mirage-block-unix != "2.12.1"
  98. mirage-block-xen
  99. mirage-btrees
  100. mirage-channel >= "4.1.0"
  101. mirage-channel-lwt
  102. mirage-conduit
  103. mirage-console-lwt
  104. mirage-crypto >= "0.10.7" & < "1.1.0"
  105. mirage-crypto-ec < "1.1.0"
  106. mirage-crypto-pk < "1.1.0"
  107. mirage-crypto-rng < "1.1.0"
  108. mirage-crypto-rng-eio
  109. mirage-crypto-rng-mirage < "1.1.0"
  110. mirage-flow >= "3.0.0"
  111. mirage-flow-combinators
  112. mirage-flow-unix
  113. mirage-fs >= "4.0.0"
  114. mirage-fs-lwt
  115. mirage-kv-lwt
  116. mirage-kv-unix
  117. mirage-nat
  118. mirage-net >= "4.0.0"
  119. mirage-net-lwt
  120. mirage-net-macosx
  121. mirage-net-solo5
  122. mirage-net-unix
  123. mirage-net-xen
  124. mirage-profile
  125. mirage-protocols >= "7.0.0"
  126. mirage-protocols-lwt
  127. mirage-qubes
  128. mirage-random
  129. mirage-solo5 < "0.10.0"
  130. mirage-stack-lwt
  131. mirage-tc
  132. mirage-types-lwt
  133. mirage-vnetif
  134. mirage-xen
  135. monorobot
  136. multihash
  137. nbd >= "4.0.3"
  138. noise
  139. oneffs
  140. otr < "1.0.0"
  141. paf
  142. pbkdf
  143. pcap-format >= "0.5.2"
  144. pf-qubes
  145. plebeia
  146. plist-xml >= "0.4.0" & < "0.5.1"
  147. ppx_cstruct >= "6.2.0"
  148. protocol-9p >= "2.0.2"
  149. protocol-9p-tool >= "2.0.2"
  150. protocol-9p-unix = "0.11.3" | >= "2.0.2"
  151. qcow >= "0.11.0"
  152. qcow-tool
  153. qcow-types
  154. randomconv < "0.2.0"
  155. rawlink >= "1.2"
  156. reparse >= "3.0.0"
  157. reparse-lwt
  158. reparse-lwt-unix
  159. rfc6287 < "1.0.4"
  160. rio
  161. riot = "0.0.7"
  162. salsa20 != "1.1.0"
  163. salsa20-core = "1.1.0"
  164. scrypt-kdf
  165. secp256k1-internal >= "0.3.1"
  166. sendmail >= "0.5.0"
  167. shared-block-ring
  168. shared-memory-ring
  169. shared-memory-ring-lwt
  170. sihl >= "3.0.0"
  171. slack
  172. solo5-elftool < "0.4.0"
  173. ssh-agent != "0.3.0"
  174. swapfs
  175. tar < "3.3.0"
  176. tar-mirage
  177. tar-unix < "3.3.0"
  178. tcpip >= "7.1.2"
  179. tls >= "0.12.8" & < "1.0.4"
  180. tls-liquidsoap
  181. uecc
  182. uring
  183. vchan
  184. vchan-unix
  185. vchan-xen
  186. vhd-format >= "0.12.0" & < "0.12.2" | >= "0.13.0"
  187. vhd-format-lwt >= "0.13.0"
  188. vmnet
  189. wayland >= "1.0"
  190. webauthn < "0.2.0"
  191. x509 >= "0.14.1" & < "1.0.6"
  192. xen-gnt
  193. yocaml_git >= "2.0.0"

Conflicts (1)

  1. js_of_ocaml < "3.5.0"
OCaml

Innovation. Community. Security.