Martino Ferrari
140 lines
3.4 KiB
Go
140 lines
3.4 KiB
Go
//go:build epics
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package epics
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/*
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#cgo CFLAGS: -Wno-unused-function
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#include "ca_wrapper.h"
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*/
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import "C"
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import (
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"time"
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"unsafe"
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"github.com/uopi/uopi/internal/datasource"
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)
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// goCAMonitorCallback is called from the C shim caMonitorCallbackShim on every
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// CA monitor event. It runs on CA's internal callback thread, so it must be
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// short and must not block. In particular it must not allocate heap memory
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// that the Go GC would need to track across a CGo boundary.
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//
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//export goCAMonitorCallback
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func goCAMonitorCallback(handle C.uintptr_t, dbrType C.int, count C.long,
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dbr unsafe.Pointer, severity C.int, epicsTimeSecs C.double) {
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h := uintptr(handle)
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// Compute the Go timestamp. EPICS timestamps are seconds since the EPICS
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// epoch (1 Jan 1990 UTC).
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const epicsEpochOffset = 631152000 // Unix seconds of 1990-01-01 00:00:00 UTC
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secs := float64(epicsTimeSecs)
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fullSecs := int64(secs)
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nsec := int64((secs - float64(fullSecs)) * 1e9)
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ts := time.Unix(fullSecs+epicsEpochOffset, nsec)
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// Map CA alarm severity to datasource quality.
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var q datasource.Quality
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switch int(severity) {
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case 0: // NO_ALARM
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q = datasource.QualityGood
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case 1, 2: // MINOR_ALARM, MAJOR_ALARM
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q = datasource.QualityUncertain
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default: // INVALID_ALARM (3)
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q = datasource.QualityBad
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}
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// Extract the value from the DBR buffer.
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var data any
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switch int(dbrType) {
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case int(C.DBR_TIME_DOUBLE):
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p := (*C.struct_dbr_time_double)(dbr)
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data = float64(p.value)
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case int(C.DBR_TIME_FLOAT):
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p := (*C.struct_dbr_time_float)(dbr)
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data = float64(p.value)
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case int(C.DBR_TIME_LONG):
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p := (*C.struct_dbr_time_long)(dbr)
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data = int64(p.value)
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case int(C.DBR_TIME_SHORT):
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p := (*C.struct_dbr_time_short)(dbr)
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data = int64(p.value)
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case int(C.DBR_TIME_ENUM):
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p := (*C.struct_dbr_time_enum)(dbr)
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data = int64(p.value)
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case int(C.DBR_TIME_STRING):
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p := (*C.struct_dbr_time_string)(dbr)
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// dbr_string is a fixed [MAX_STRING_SIZE]byte array
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data = C.GoString((*C.char)(unsafe.Pointer(&p.value[0])))
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default:
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// Unknown type; mark as bad quality and return early.
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q = datasource.QualityBad
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data = float64(0)
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}
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v := datasource.Value{Timestamp: ts, Data: data, Quality: q}
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// Look up the subscription channel under the global handle table lock and
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// perform a non-blocking send so we never stall the CA callback thread.
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handleMu.Lock()
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ch, ok := handleTable[h]
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handleMu.Unlock()
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if ok {
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select {
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case ch <- v:
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default:
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// Subscriber is not reading fast enough; drop the update rather than
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// block the CA callback thread.
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}
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}
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}
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// goCAConnectionCallback is called from the C shim caConnectionCallbackShim
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// whenever a channel connects or disconnects.
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//
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//export goCAConnectionCallback
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func goCAConnectionCallback(handle C.uintptr_t, connected C.int) {
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h := uintptr(handle)
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handleMu.Lock()
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entry, ok := connTable[h]
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handleMu.Unlock()
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if !ok {
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return
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}
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if int(connected) == 1 {
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// Signal the one-shot "connected" channel if it has not been closed yet.
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select {
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case entry.connCh <- struct{}{}:
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default:
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}
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} else {
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// Channel disconnected; push a QualityBad sentinel to the subscriber.
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handleMu.Lock()
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ch, chOk := handleTable[h]
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handleMu.Unlock()
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if chOk {
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v := datasource.Value{
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Timestamp: time.Now(),
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Data: float64(0),
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Quality: datasource.QualityBad,
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}
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select {
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case ch <- v:
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default:
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}
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}
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}
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}
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