Martino Ferrari
141 lines
3.9 KiB
Go
141 lines
3.9 KiB
Go
// Package proto contains the low-level Channel Access wire-protocol constants,
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// header codec, and DBR type decode functions. All types are big-endian as
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// required by the CA specification.
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package proto
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// CA command opcodes (uint16, first field of every message header).
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const (
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CmdVersion = 0 // version negotiation (first message on every TCP connection)
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CmdEventAdd = 1 // subscribe to value updates / server event push
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CmdEventCancel = 2 // cancel subscription
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CmdWrite = 4 // put value (fire-and-forget, no server reply)
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CmdSearch = 6 // UDP: locate IOC hosting a PV
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CmdNotFound = 14 // UDP: IOC does not host the requested PV
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CmdReadNotify = 15 // get value with callback (async GET)
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CmdCreateChan = 18 // create channel on TCP circuit
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CmdWriteNotify = 19 // put value with acknowledgement
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CmdClientName = 20 // announce client username (sent after VERSION)
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CmdHostName = 21 // announce client hostname (sent after VERSION)
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CmdAccessRights = 22 // server → client: access rights bitmask
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CmdEcho = 23 // heartbeat ping/pong
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CmdCreateFail = 26 // server → client: CREATE_CHAN failed
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CmdServerDisc = 27 // server → client: server shutting down
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)
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// CA minor protocol revision announced during the VERSION handshake.
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// Corresponds to CA 4.13, supported by EPICS 3.14+ and all EPICS 7 servers.
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const MinorVersion = 13
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// Default CA port (TCP and UDP).
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const DefaultPort = 5064
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// Search reply data_type values.
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const (
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SearchReply = 10 // DO_REPLY: ask server to respond
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SearchNoReply = 5 // DONT_REPLY: suppress response (used by repeater)
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)
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// AccessRights bitmask values (parameter2 of CmdAccessRights message).
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const (
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AccessRead = 1 << 0
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AccessWrite = 1 << 1
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)
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// DBE event mask bits used in the 16-byte EVENT_ADD payload.
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const (
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DBEValue = 0x01 // trigger on any value change
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DBEAlarm = 0x04 // trigger on alarm state change
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DBEDefault = DBEValue | DBEAlarm
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)
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// ---- DBF field types (native IOC field type, reported in CREATE_CHAN reply) ----
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const (
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DBFString = 0
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DBFShort = 1 // also DBFInt
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DBFFloat = 2
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DBFEnum = 3
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DBFChar = 4
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DBFLong = 5
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DBFDouble = 6
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)
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// ---- DBR request types ----
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// Plain value types (used in WRITE).
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const (
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DBRString = 0
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DBRShort = 1
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DBRFloat = 2
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DBREnum = 3
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DBRChar = 4
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DBRLong = 5
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DBRDouble = 6
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)
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// DBR_TIME_* types (value + timestamp + alarm status; used in EVENT_ADD).
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// Numbers from db_access.h: STRING=14, SHORT/INT=15, FLOAT=16, ENUM=17, CHAR=18, LONG=19, DOUBLE=20.
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const (
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DBRTimeString = 14
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DBRTimeShort = 15
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DBRTimeFloat = 16
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DBRTimeEnum = 17
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DBRTimeChar = 18
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DBRTimeLong = 19
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DBRTimeDouble = 20
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)
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// DBR_CTRL_* types (full control info: units, limits, enum strings; used in READ_NOTIFY).
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const (
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DBRCtrlString = 28
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DBRCtrlShort = 29
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DBRCtrlFloat = 30
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DBRCtrlEnum = 31
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DBRCtrlChar = 32
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DBRCtrlLong = 33
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DBRCtrlDouble = 34
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)
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// NativeTimeType maps a DBF field type to the corresponding DBR_TIME_* type
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// that should be used for monitor subscriptions.
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func NativeTimeType(dbfType int, elementCount int) uint16 {
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switch dbfType {
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case DBFDouble:
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return DBRTimeDouble
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case DBFFloat:
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return DBRTimeFloat
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case DBFLong:
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return DBRTimeLong
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case DBFShort:
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return DBRTimeShort
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case DBFEnum:
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return DBRTimeEnum
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case DBFString:
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return DBRTimeString
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case DBFChar:
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if elementCount > 1 {
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return DBRTimeString // waveform of chars treated as string
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}
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return DBRTimeChar
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default:
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return DBRTimeDouble
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}
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}
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// NativeCtrlType maps a DBF field type to the corresponding DBR_CTRL_* type
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// that should be used for metadata gets.
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func NativeCtrlType(dbfType int) uint16 {
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switch dbfType {
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case DBFDouble, DBFFloat:
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return DBRCtrlDouble
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case DBFLong, DBFShort, DBFChar:
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return DBRCtrlLong
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case DBFEnum:
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return DBRCtrlEnum
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case DBFString:
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return DBRCtrlString
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default:
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return DBRCtrlDouble
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}
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}
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