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SpaceOS wire protocol codecs for host-guest communication
1(** Shared memory page accessors (4096 bytes).
2
3 {v
4 Offset Size Field
5 0x000 8 bytes Guest heartbeat counter (uint64)
6 0x008 8 bytes Host heartbeat ack (uint64)
7 0x010 4 bytes Time version (uint32, seqlock)
8 0x014 8 bytes Mission time seconds (uint64)
9 0x01C 4 bytes Mission time nanoseconds (uint32)
10 0x020 4 bytes Guest status word (uint32)
11 0x024 4 bytes Host command word (uint32)
12 0x028 4 bytes Guest command ack (uint32)
13 0x100 256 bytes Guest health string (UTF-8, null-terminated)
14 v} *)
15
16val page_size : int
17(** Shared memory page size: 4096 bytes. *)
18
19(** {1 Field offsets} *)
20
21val off_heartbeat : int
22(** Offset of the guest heartbeat counter (8 bytes). *)
23
24val off_heartbeat_ack : int
25(** Offset of the host heartbeat acknowledgement (8 bytes). *)
26
27val off_time_version : int
28(** Offset of the time version seqlock (4 bytes). *)
29
30val off_time_seconds : int
31(** Offset of mission time seconds (8 bytes). *)
32
33val off_time_nanos : int
34(** Offset of mission time nanoseconds (4 bytes). *)
35
36val off_guest_status : int
37(** Offset of the guest status word (4 bytes). *)
38
39val off_host_cmd : int
40(** Offset of the host command word (4 bytes). *)
41
42val off_guest_cmd_ack : int
43(** Offset of the guest command acknowledgement (4 bytes). *)
44
45val off_health_string : int
46(** Offset of the guest health string (256 bytes). *)
47
48val health_string_len : int
49(** Maximum health string length: 256 bytes. *)
50
51(** {1 Accessors}
52
53 All accessors work on a [bytes] buffer of at least [page_size] bytes, using
54 big-endian byte order. *)
55
56val heartbeat : bytes -> int64
57(** Read the guest heartbeat counter. *)
58
59val set_heartbeat : bytes -> int64 -> unit
60(** Write the guest heartbeat counter. *)
61
62val heartbeat_ack : bytes -> int64
63(** Read the host heartbeat acknowledgement. *)
64
65val set_heartbeat_ack : bytes -> int64 -> unit
66(** Write the host heartbeat acknowledgement. *)
67
68val time_version : bytes -> int
69(** Read the time version seqlock. *)
70
71val set_time_version : bytes -> int -> unit
72(** Write the time version seqlock. *)
73
74val time_seconds : bytes -> int64
75(** Read the mission time seconds. *)
76
77val set_time_seconds : bytes -> int64 -> unit
78(** Write the mission time seconds. *)
79
80val time_nanos : bytes -> int
81(** Read the mission time nanoseconds. *)
82
83val set_time_nanos : bytes -> int -> unit
84(** Write the mission time nanoseconds. *)
85
86val guest_status : bytes -> int
87(** Read the guest status word. *)
88
89val set_guest_status : bytes -> int -> unit
90(** Write the guest status word. *)
91
92val host_cmd : bytes -> int
93(** Read the host command word. *)
94
95val set_host_cmd : bytes -> int -> unit
96(** Write the host command word. *)
97
98val guest_cmd_ack : bytes -> int
99(** Read the guest command acknowledgement. *)
100
101val set_guest_cmd_ack : bytes -> int -> unit
102(** Write the guest command acknowledgement. *)
103
104val health_string : bytes -> string
105(** Read the guest health string. *)
106
107val set_health_string : bytes -> string -> unit
108(** Write the guest health string. *)
109
110(** {1 Mission time with seqlock} *)
111
112type mission_time = { seconds : int64; nanos : int }
113
114val write_mission_time : bytes -> mission_time -> unit
115(** Host: write mission time with seqlock protocol. *)
116
117val read_mission_time : bytes -> mission_time
118(** Guest: read mission time with seqlock retry. *)
119
120(** {1 Command word bits} *)
121
122val cmd_shutdown : int
123(** Shutdown command bit. *)
124
125val cmd_param_reload : int
126(** Parameter reload command bit. *)
127
128val cmd_dp_ack : int
129(** Data product acknowledgement command bit. *)