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streammanager.go
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streammanager.go
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// Package streammanager keeps track of open streams and allows for reading/writing to them.
package streammanager
import (
"io"
"os"
"sort"
"github.com/corywalker/expreduce/expreduce/atoms"
"github.com/corywalker/expreduce/pkg/expreduceapi"
)
type streamKey struct {
id int64
name string
}
type streamMap map[streamKey]io.Writer
type streamManagerImpl struct {
openStreams streamMap
}
// NewStreamManager returns an object that can keep track of open streams.
func NewStreamManager() expreduceapi.StreamManager {
sm := streamManagerImpl{}
sm.openStreams = make(streamMap)
sm.openStreams[streamKey{id: 1, name: "stdout"}] = os.Stdout
sm.openStreams[streamKey{id: 2, name: "stderr"}] = os.Stderr
return &sm
}
func (sm streamManagerImpl) fillMissingIndex(key *streamKey) {
if key.id == -1 {
if key.name == "stdout" {
key.id = 1
} else if key.name == "stdin" {
key.id = 2
}
}
}
// WriteString writes the toWrite string into the stream defined by streamName and streamIndex.
func (sm streamManagerImpl) WriteString(
streamName string,
streamIndex int64,
toWrite string,
) bool {
key := streamKey{id: streamIndex, name: streamName}
sm.fillMissingIndex(&key)
writer, hasWriter := sm.openStreams[key]
if !hasWriter {
return false
}
_, err := writer.Write([]byte(toWrite))
return err == nil
}
func (sm streamManagerImpl) AsExpr() expreduceapi.Ex {
res := atoms.E(atoms.S("List"))
keys := make([]streamKey, 0)
for k := range sm.openStreams {
keys = append(keys, k)
}
sort.Slice(keys, func(i, j int) bool {
return keys[i].id < keys[j].id
})
for _, k := range keys {
res.AppendEx(atoms.E(
atoms.S("OutputStream"),
atoms.NewString(k.name),
atoms.NewInt(k.id),
))
}
return res
}