package cstruct

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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 >= "1.3.0"
  2. angstrom >= "0.2.0" & < "0.6.0"
  3. arakoon >= "1.8.6" & < "1.8.12"
  4. arp >= "3.0.0"
  5. asn1-combinators = "0.2.6"
  6. async_unix >= "v0.17.0"
  7. awa != "0.0.3"
  8. awa-lwt
  9. awa-mirage
  10. bip32
  11. builder
  12. builder-web
  13. capnp-rpc-net >= "1.2.1"
  14. carton >= "0.4.3"
  15. carton-git
  16. carton-lwt
  17. certify >= "0.2" & < "0.3.3"
  18. chamelon
  19. channel
  20. charrua
  21. charrua-client
  22. charrua-client-lwt
  23. charrua-client-mirage < "0.12.0"
  24. charrua-server
  25. charrua-unix = "0.6"
  26. coap
  27. coap-core
  28. coap-server-lwt
  29. cohttp >= "0.9.7" & < "0.10.0"
  30. cohttp-mirage >= "6.0.0~alpha0"
  31. colombe < "0.2.0"
  32. conduit >= "0.6.0" & < "0.15.2"
  33. conduit-async = "3.0.0"
  34. conduit-lwt = "3.0.0"
  35. conduit-mirage != "3.0.0"
  36. conex < "0.10.0"
  37. conex-mirage-crypto
  38. conex-nocrypto >= "0.11.0"
  39. cowabloga >= "0.0.5"
  40. crc
  41. crunch >= "2.0.0" & < "3.0.0"
  42. cstruct-async >= "3.4.0" & < "4.0.0" | >= "6.2.0"
  43. cstruct-lwt >= "6.2.0"
  44. cstruct-sexp >= "6.2.0"
  45. cstruct-unix >= "3.1.0" & < "3.2.0" | >= "3.4.0" & < "4.0.0" | >= "6.2.0"
  46. current-albatross-deployer
  47. current_git >= "0.6"
  48. current_github >= "0.4"
  49. current_web >= "0.4"
  50. datakit
  51. datakit-ci >= "0.12.4"
  52. datakit-client
  53. datakit-client-9p
  54. datakit-server < "0.12.0"
  55. depyt >= "0.3.0"
  56. dirsp-proscript
  57. dns >= "6.0.0"
  58. dns-cli >= "6.0.0"
  59. dns-client < "7.0.0"
  60. dns-forward >= "0.9.0"
  61. dns-mirage >= "6.0.0"
  62. dns-server >= "6.0.0"
  63. dns-stub >= "6.0.0"
  64. dns-tsig >= "6.0.0"
  65. dnssd
  66. dnssec
  67. dream
  68. eio
  69. eqaf >= "0.8" & < "0.10"
  70. eqaf-cstruct
  71. ethernet >= "2.2.1"
  72. fat-filesystem = "0.13.0" | >= "0.15.0"
  73. frenetic < "2.0.0" | >= "3.2.0" & < "5.0.0" | >= "5.0.5"
  74. geojsone >= "0.2.0"
  75. git >= "2.0.0" & < "3.4.0" | >= "3.9.1"
  76. git-cohttp
  77. git-cohttp-mirage
  78. git-cohttp-unix
  79. git-mirage >= "3.0.0"
  80. git-unix >= "3.0.0"
  81. github-hooks >= "0.2.0"
  82. gluten-mirage
  83. gpt
  84. h2-mirage
  85. hacl-star >= "0.7.0"
  86. hex >= "1.4.0"
  87. hkdf < "2.0.0"
  88. http-multipart-formdata >= "3.1.0"
  89. httpun-mirage
  90. httpun-ws-mirage
  91. hvsock
  92. io-page
  93. io-page-unix
  94. io-page-xen
  95. ipaddr-cstruct >= "5.2.0"
  96. irmin >= "0.9.0" & < "1.0.0" | >= "1.1.0" & < "1.3.2"
  97. irmin-git >= "2.3.0"
  98. irmin-indexeddb >= "0.3"
  99. jose != "0.6.0"
  100. key-parsers >= "0.5.0" & < "0.9.2" | >= "1.2.1"
  101. launchd
  102. learn-ocaml-client
  103. ledgerwallet >= "0.2.1"
  104. letsencrypt >= "0.4.0"
  105. letsencrypt-app >= "0.4.0"
  106. lt-code
  107. macaddr-cstruct >= "5.2.0"
  108. mbr-format >= "1.0.0"
  109. memtrace_viewer < "v0.15.0"
  110. metrics-mirage
  111. mimic >= "0.0.4"
  112. mirage >= "0.7.2" & < "0.9.0" | >= "0.10.0" & < "2.4.0"
  113. mirage-block >= "2.0.0"
  114. mirage-block-ccm
  115. mirage-block-combinators >= "3.0.0"
  116. mirage-block-ramdisk >= "0.3" & < "0.5"
  117. mirage-block-solo5 >= "0.6.2"
  118. mirage-block-unix = "2.0.0" | = "2.7.0" | >= "2.11.1" & < "2.12.0" | >= "2.13.0"
  119. mirage-block-xen >= "1.4.0" & < "1.5.2" | >= "1.6.0" & < "2.0.0" | >= "2.1.1"
  120. mirage-btrees
  121. mirage-channel = "4.0.0" | >= "4.1.0"
  122. mirage-channel-lwt
  123. mirage-clock-unix < "1.0.0"
  124. mirage-clock-xen < "1.0.0"
  125. mirage-conduit < "2.0.0" | >= "2.3.1"
  126. mirage-console >= "3.0.0" & < "4.0.0"
  127. mirage-console-lwt
  128. mirage-console-solo5 >= "0.2.0"
  129. mirage-console-unix >= "2.2.1" & < "2.3.3" | >= "3.0.0" & < "3.0.2" | >= "5.0.0"
  130. mirage-console-xen >= "5.0.0"
  131. mirage-console-xen-backend >= "5.0.0"
  132. mirage-crypto >= "0.8.1" & < "0.8.5" | >= "0.10.4" & < "1.0.0"
  133. mirage-crypto-ec < "1.0.0"
  134. mirage-crypto-entropy
  135. mirage-crypto-pk < "1.0.0"
  136. mirage-crypto-rng < "1.0.0"
  137. mirage-crypto-rng-eio < "1.0.0"
  138. mirage-crypto-rng-mirage < "1.0.0"
  139. mirage-dns != "2.6.0" & < "2.7.0"
  140. mirage-entropy < "0.5.1"
  141. mirage-entropy-xen < "0.3.0"
  142. mirage-flow < "1.2.0" | >= "2.0.0"
  143. mirage-flow-combinators != "2.0.1"
  144. mirage-flow-rawlink
  145. mirage-flow-unix >= "1.4.0" & != "2.0.1"
  146. mirage-fs >= "0.4.0" & < "1.0.0" | >= "3.0.0"
  147. mirage-fs-lwt
  148. mirage-fs-unix < "1.1.0" | >= "1.4.0" & < "1.5.0"
  149. mirage-kv-lwt
  150. mirage-kv-unix
  151. mirage-nat
  152. mirage-net = "0.5.2" | >= "3.0.0"
  153. mirage-net-fd < "0.2.1"
  154. mirage-net-lwt
  155. mirage-net-macosx
  156. mirage-net-solo5
  157. mirage-net-unix < "2.1.0" | >= "2.2.1" & < "2.4.1" | >= "2.6.0"
  158. mirage-net-xen != "1.4.2" & != "1.7.0"
  159. mirage-profile >= "0.8.2"
  160. mirage-protocols >= "6.0.0" & < "8.0.0"
  161. mirage-protocols-lwt
  162. mirage-qubes != "0.2" & < "0.5" | >= "0.7.0" & < "0.9.0" | >= "0.9.2"
  163. mirage-qubes-ipv4 < "0.9.4"
  164. mirage-random < "4.0.0"
  165. mirage-random-stdlib
  166. mirage-random-test
  167. mirage-solo5
  168. mirage-stack-lwt
  169. mirage-tc
  170. mirage-tcpip-unix
  171. mirage-tcpip-xen
  172. mirage-types-lwt < "3.7.1"
  173. mirage-unix < "0.9.4" | >= "2.5.0" & < "3.0.8"
  174. mirage-vnetif >= "0.6.0"
  175. mirage-vnetif-stack
  176. mirage-www < "0.4.0" | >= "1.1.0"
  177. mirage-xen < "2.0.0" | >= "2.6.0"
  178. monorobot
  179. mrt-format >= "0.3.1"
  180. mstruct < "1.4.0"
  181. multihash
  182. nbd >= "4.0.3"
  183. netchannel != "2.0.0"
  184. nocrypto < "0.4.0"
  185. noise
  186. oneffs
  187. openflow < "0.2.0"
  188. otr = "0.3.1" | >= "0.3.5"
  189. ox < "1.1.1"
  190. paf >= "0.0.5"
  191. pbkdf = "1.2.0"
  192. pcap-format >= "0.5.2"
  193. pf-qubes
  194. plebeia
  195. plist-xml >= "0.4.0"
  196. ppx_cstruct >= "6.2.0"
  197. protocol-9p >= "2.0.2"
  198. protocol-9p-tool >= "2.0.2"
  199. protocol-9p-unix = "0.11.3" | >= "2.0.2"
  200. qcow >= "0.11.0"
  201. qcow-tool
  202. randomconv < "0.2.0"
  203. rawlink >= "0.6" & != "1.0"
  204. reparse >= "3.0.0"
  205. reparse-lwt
  206. reparse-lwt-unix
  207. rfc6287 >= "1.0.2" & < "1.0.4"
  208. rio
  209. riot = "0.0.7"
  210. salsa20 != "1.1.0"
  211. salsa20-core = "1.1.0"
  212. scrypt-kdf = "1.0.0" | >= "1.2.0"
  213. secp256k1-internal >= "0.3.1"
  214. sendmail >= "0.5.0"
  215. shared-block-ring
  216. shared-memory-ring = "3.0.1" | >= "3.1.1"
  217. shared-memory-ring-lwt
  218. sihl >= "3.0.0"
  219. slack
  220. solo5-elftool
  221. ssh-agent != "0.3.0"
  222. tar >= "2.0.0"
  223. tar-mirage
  224. tar-unix != "1.0.0"
  225. tcpip >= "3.3.0" & < "4.1.0" | >= "7.1.0"
  226. tezos-lmdb
  227. tls >= "0.12.5" & < "0.13.1" | >= "0.14.0"
  228. u2f >= "0.1.2"
  229. uecc
  230. uring
  231. vchan >= "3.0.0" & < "5.0.0" | >= "6.0.1"
  232. vchan-unix
  233. vchan-xen
  234. vhd-format >= "0.12.0" & < "0.12.2"
  235. vhd-format-lwt >= "0.12.1" & < "0.12.3"
  236. vhd-tool < "0.12.0"
  237. vmnet >= "1.1.0"
  238. wayland >= "1.0"
  239. webauthn
  240. x509 >= "0.14.1"
  241. xe
  242. xen-api-client >= "0.9.6" & < "0.9.14"
  243. xen-block-driver >= "0.2.5"
  244. xen-gnt
  245. xenstore >= "2.1.0" & < "2.3.0"

Conflicts (1)

  1. js_of_ocaml < "3.5.0"
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