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netchan: use gob DecodeValue to eliminate the need for a pointer value

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in Import and Export.

R=rsc
CC=golang-dev
https://golang.org/cl/1707047
This commit is contained in:
Rob Pike 2010-06-28 17:12:09 -07:00
parent 12a4d84371
commit d4384ff7f5
4 changed files with 28 additions and 40 deletions
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36
src/pkg/netchan/import.go
View file

@ -19,7 +19,6 @@ import (
type importChan struct {
ch *reflect.ChanValue
dir Dir
ptr *reflect.PtrValue // a pointer value we can point at each new received item
}
// An Importer allows a set of channels to be imported from a single
@ -67,9 +66,11 @@ func (imp *Importer) shutdown() {
func (imp *Importer) run() {
// Loop on responses; requests are sent by ImportNValues()
hdr := new(header)
hdrValue := reflect.NewValue(hdr)
err := new(error)
errValue := reflect.NewValue(err)
for {
if e := imp.decode(hdr); e != nil {
if e := imp.decode(hdrValue); e != nil {
log.Stderr("importer header:", e)
imp.shutdown()
return
@ -78,7 +79,7 @@ func (imp *Importer) run() {
case payData:
// done lower in loop
case payError:
if e := imp.decode(err); e != nil {
if e := imp.decode(errValue); e != nil {
log.Stderr("importer error:", e)
return
}
@ -103,20 +104,19 @@ func (imp *Importer) run() {
return
}
// Create a new value for each received item.
val := reflect.MakeZero(ich.ptr.Type().(*reflect.PtrType).Elem())
ich.ptr.PointTo(val)
if e := imp.decode(ich.ptr.Interface()); e != nil {
value := reflect.MakeZero(ich.ch.Type().(*reflect.ChanType).Elem())
if e := imp.decode(value); e != nil {
log.Stderr("importer value decode:", e)
return
}
ich.ch.Send(val)
ich.ch.Send(value)
}
}
// Import imports a channel of the given type and specified direction.
// It is equivalent to ImportNValues with a count of 0, meaning unbounded.
func (imp *Importer) Import(name string, chT interface{}, dir Dir, pT interface{}) os.Error {
return imp.ImportNValues(name, chT, dir, pT, 0)
func (imp *Importer) Import(name string, chT interface{}, dir Dir) os.Error {
return imp.ImportNValues(name, chT, dir, 0)
}
// ImportNValues imports a channel of the given type and specified direction
@ -125,36 +125,26 @@ func (imp *Importer) Import(name string, chT interface{}, dir Dir, pT interface{
// the remote site's channel is provided in the call and may be of arbitrary
// channel type.
// Despite the literal signature, the effective signature is
// ImportNValues(name string, chT chan T, dir Dir, pT T, n int) os.Error
// where T must be a struct, pointer to struct, etc. pT may be more indirect
// than the value type of the channel (e.g. chan T, pT *T) but it must be a
// pointer.
// ImportNValues(name string, chT chan T, dir Dir, n int) os.Error
// Example usage:
// imp, err := NewImporter("tcp", "netchanserver.mydomain.com:1234")
// if err != nil { log.Exit(err) }
// ch := make(chan myType)
// err := imp.ImportNValues("name", ch, Recv, new(myType), 1)
// err := imp.ImportNValues("name", ch, Recv, 1)
// if err != nil { log.Exit(err) }
// fmt.Printf("%+v\n", <-ch)
// TODO: fix reflection so we can eliminate the need for pT.
func (imp *Importer) ImportNValues(name string, chT interface{}, dir Dir, pT interface{}, n int) os.Error {
func (imp *Importer) ImportNValues(name string, chT interface{}, dir Dir, n int) os.Error {
ch, err := checkChan(chT, dir)
if err != nil {
return err
}
// Make sure pT is a pointer (to a pointer...) to a struct.
rt := reflect.Typeof(pT)
if _, ok := rt.(*reflect.PtrType); !ok {
return os.ErrorString("not a pointer:" + rt.String())
}
imp.chanLock.Lock()
defer imp.chanLock.Unlock()
_, present := imp.chans[name]
if present {
return os.ErrorString("channel name already being imported:" + name)
}
ptr := reflect.MakeZero(reflect.Typeof(pT)).(*reflect.PtrValue)
imp.chans[name] = &importChan{ch, dir, ptr}
imp.chans[name] = &importChan{ch, dir}
// Tell the other side about this channel.
hdr := new(header)
hdr.name = name