1NBDKit(3)                                                            NBDKit(3)
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NAME

6       NBDKit  -  Interface  between  plugins  written in OCaml and the nbdkit
7       server.
8

Module

10       Module   NBDKit
11

Documentation

13       Module NBDKit
14        : sig end
15
16
17       Interface between plugins written in OCaml and the nbdkit server.
18
19       Read nbdkit-ocaml-plugin(3) first.
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23
24
25       type flags = flag list
26
27
28       Flags passed from the server to various callbacks.
29
30
31       type flag =
32        | May_trim
33        | FUA
34        | Req_one
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36
37
38
39       type fua_flag =
40        | FuaNone
41        | FuaEmulate
42        | FuaNative
43
44
45
46
47       type cache_flag =
48        | CacheNone
49        | CacheEmulate
50        | CacheNop
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52
53
54
55       type extent = {
56        offset : int64 ;
57        length : int64 ;
58        is_hole : bool ;
59        is_zero : bool ;
60        }
61
62
63       The type of the extent list returned by NBDKit.plugin.extents
64
65
66
67       type export = {
68        name : string ;
69        description : string option ;
70        }
71
72
73       The type of the export list returned by NBDKit.plugin.list_exports
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75
76
77       type thread_model =
78        | THREAD_MODEL_SERIALIZE_CONNECTIONS
79        | THREAD_MODEL_SERIALIZE_ALL_REQUESTS
80        | THREAD_MODEL_SERIALIZE_REQUESTS
81        | THREAD_MODEL_PARALLEL
82
83
84       The type of the thread model returned by NBDKit.plugin.thread_model
85
86
87
88       type 'a plugin = {
89        name : string ;
90        longname : string ;
91        version : string ;
92        description : string ;
93        load : (unit -> unit) option ;
94        unload : (unit -> unit) option ;
95        dump_plugin : (unit -> unit) option ;
96        config : (string -> string -> unit) option ;
97        config_complete : (unit -> unit) option ;
98        config_help : string ;
99        thread_model : (unit -> thread_model) option ;
100        get_ready : (unit -> unit) option ;
101        after_fork : (unit -> unit) option ;
102        preconnect : (bool -> unit) option ;
103        list_exports : (bool -> bool -> export list) option ;
104        default_export : (bool -> bool -> string) option ;
105        open_connection : (bool -> 'a) option ;
106        close : ('a -> unit) option ;
107        get_size : ('a -> int64) option ;
108        export_description : ('a -> string) option ;
109        can_cache : ('a -> cache_flag) option ;
110        can_extents : ('a -> bool) option ;
111        can_fast_zero : ('a -> bool) option ;
112        can_flush : ('a -> bool) option ;
113        can_fua : ('a -> fua_flag) option ;
114        can_multi_conn : ('a -> bool) option ;
115        can_trim : ('a -> bool) option ;
116        can_write : ('a -> bool) option ;
117        can_zero : ('a -> bool) option ;
118        is_rotational : ('a -> bool) option ;
119        pread : ('a -> int32 -> int64 -> flags -> string) option ;
120        pwrite : ('a -> string -> int64 -> flags -> unit) option ;
121        flush : ('a -> flags -> unit) option ;
122        trim : ('a -> int32 -> int64 -> flags -> unit) option ;
123        zero : ('a -> int32 -> int64 -> flags -> unit) option ;
124        extents : ('a -> int32 -> int64 -> flags -> extent list) option ;
125        cache : ('a -> int32 -> int64 -> flags -> unit) option ;
126        }
127
128
129       The plugin fields and callbacks.
130
131       The 'a parameter is the handle type returned  by  your  open_connection
132       method and passed back to all connected calls.
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134
135
136       val default_callbacks : 'a plugin
137
138       The  plugin  with  all  fields  set  to  None  , so you can write { de‐
139       fault_callbacks with field1 = Some foo1; field2 = Some foo2 }
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141
142
143
144       val register_plugin : 'a plugin -> unit
145
146       Register the plugin with nbdkit.
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148
149
150       val set_error : Unix.error -> unit
151
152       Set the errno returned over the NBD protocol to the client.
153
154       Notice however that the NBD protocol only supports a small  handful  of
155       errno values.  Any other errno will be translated into EINVAL .
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158
159       val parse_size : string -> int64
160
161       Bindings   for   nbdkit_parse_size   ,   nbdkit_parse_bool   and   nbd‐
162       kit_read_password .  See nbdkit-plugin(3) for information  about  these
163       functions.
164
165       On error these functions all raise Invalid_argument .  The actual error
166       is sent to the nbdkit error log and is not  available  from  the  OCaml
167       code.  It is usually best to let the exception escape.
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171       val parse_bool : string -> bool
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175
176       val read_password : string -> string
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180
181       val realpath : string -> string
182
183       Binding  for  nbdkit_realpath .  Returns the canonical path from a path
184       parameter.
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187
188       val nanosleep : int -> int -> unit
189
190       Binding for nbdkit_nanosleep .  Sleeps for seconds and nanoseconds.
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194       val export_name : unit -> string
195
196       Binding for nbdkit_export_name .  Returns the name of the export as re‐
197       quested by the client.
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200
201       val shutdown : unit -> unit
202
203       Binding for nbdkit_shutdown .  Requests the server shut down.
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206
207       val debug : ('a, unit, string, unit) Stdlib.format4 -> 'a
208
209       Print a debug message when nbdkit is in verbose mode.
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212
213       val version : unit -> string
214
215       Return the version of nbdkit that the plugin was compiled with.
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219       val peer_pid : unit -> int64
220
221       Binding for nbdkit_peer_pid .
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225       val peer_uid : unit -> int64
226
227       Binding for nbdkit_peer_uid .
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231       val peer_gid : unit -> int64
232
233       Binding for nbdkit_peer_gid .
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239OCamldoc                          2021-05-25                         NBDKit(3)