Initial go port of epics

pkg/ca/proto/opcodes.go

@@ -0,0 +1,139 @@
+// Package proto contains the low-level Channel Access wire-protocol constants,
+// header codec, and DBR type decode functions.  All types are big-endian as
+// required by the CA specification.
+package proto
+
+// CA command opcodes (uint16, first field of every message header).
+const (
+	CmdVersion      = 0  // version negotiation (first message on every TCP connection)
+	CmdEventAdd     = 1  // subscribe to value updates / server event push
+	CmdEventCancel  = 2  // cancel subscription
+	CmdWrite        = 4  // put value (fire-and-forget, no server reply)
+	CmdSearch       = 6  // UDP: locate IOC hosting a PV
+	CmdNotFound     = 14 // UDP: IOC does not host the requested PV
+	CmdReadNotify   = 15 // get value with callback (async GET)
+	CmdCreateChan   = 18 // create channel on TCP circuit
+	CmdWriteNotify  = 19 // put value with acknowledgement
+	CmdClientName   = 20 // announce client username (sent after VERSION)
+	CmdHostName     = 21 // announce client hostname  (sent after VERSION)
+	CmdAccessRights = 22 // server → client: access rights bitmask
+	CmdEcho         = 23 // heartbeat ping/pong
+	CmdCreateFail   = 26 // server → client: CREATE_CHAN failed
+	CmdServerDisc   = 27 // server → client: server shutting down
+)
+
+// CA minor protocol revision announced during the VERSION handshake.
+// Corresponds to CA 4.13, supported by EPICS 3.14+ and all EPICS 7 servers.
+const MinorVersion = 13
+
+// Default CA port (TCP and UDP).
+const DefaultPort = 5064
+
+// Search reply data_type values.
+const (
+	SearchReply    = 10 // DO_REPLY: ask server to respond
+	SearchNoReply  = 5  // DONT_REPLY: suppress response (used by repeater)
+)
+
+// AccessRights bitmask values (parameter2 of CmdAccessRights message).
+const (
+	AccessRead  = 1 << 0
+	AccessWrite = 1 << 1
+)
+
+// DBE event mask bits used in the 16-byte EVENT_ADD payload.
+const (
+	DBEValue   = 0x01 // trigger on any value change
+	DBEAlarm   = 0x04 // trigger on alarm state change
+	DBEDefault = DBEValue | DBEAlarm
+)
+
+// ---- DBF field types (native IOC field type, reported in CREATE_CHAN reply) ----
+
+const (
+	DBFString = 0
+	DBFShort  = 1 // also DBFInt
+	DBFFloat  = 2
+	DBFEnum   = 3
+	DBFChar   = 4
+	DBFLong   = 5
+	DBFDouble = 6
+)
+
+// ---- DBR request types ----
+
+// Plain value types (used in WRITE).
+const (
+	DBRString = 0
+	DBRShort  = 1
+	DBRFloat  = 2
+	DBREnum   = 3
+	DBRChar   = 4
+	DBRLong   = 5
+	DBRDouble = 6
+)
+
+// DBR_TIME_* types (value + timestamp + alarm status; used in EVENT_ADD).
+const (
+	DBRTimeString = 21
+	DBRTimeShort  = 19
+	DBRTimeFloat  = 20
+	DBRTimeEnum   = 23
+	DBRTimeChar   = 24
+	DBRTimeLong   = 22
+	DBRTimeDouble = 25
+)
+
+// DBR_CTRL_* types (full control info: units, limits, enum strings; used in READ_NOTIFY).
+const (
+	DBRCtrlString = 28
+	DBRCtrlShort  = 29
+	DBRCtrlFloat  = 30
+	DBRCtrlEnum   = 31
+	DBRCtrlChar   = 32
+	DBRCtrlLong   = 33
+	DBRCtrlDouble = 34
+)
+
+// NativeTimeType maps a DBF field type to the corresponding DBR_TIME_* type
+// that should be used for monitor subscriptions.
+func NativeTimeType(dbfType int, elementCount int) uint16 {
+	switch dbfType {
+	case DBFDouble:
+		return DBRTimeDouble
+	case DBFFloat:
+		return DBRTimeFloat
+	case DBFLong:
+		return DBRTimeLong
+	case DBFShort:
+		return DBRTimeShort
+	case DBFEnum:
+		return DBRTimeEnum
+	case DBFString:
+		return DBRTimeString
+	case DBFChar:
+		if elementCount > 1 {
+			return DBRTimeString // waveform of chars treated as string
+		}
+		return DBRTimeChar
+	default:
+		return DBRTimeDouble
+	}
+}
+
+// NativeCtrlType maps a DBF field type to the corresponding DBR_CTRL_* type
+// that should be used for metadata gets.
+func NativeCtrlType(dbfType int) uint16 {
+	switch dbfType {
+	case DBFDouble, DBFFloat:
+		return DBRCtrlDouble
+	case DBFLong, DBFShort, DBFChar:
+		return DBRCtrlLong
+	case DBFEnum:
+		return DBRCtrlEnum
+	case DBFString:
+		return DBRCtrlString
+	default:
+		return DBRCtrlDouble
+	}
+}