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/
stream.go
177 lines (164 loc) · 3.81 KB
/
stream.go
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package stream
import (
"encoding/json"
"flag"
"fmt"
"io"
"os"
"reflect"
"strings"
"golang.org/x/sync/errgroup"
)
var (
stdin io.Reader = os.Stdin
stdout io.Writer = os.Stdout
stderr interface {
io.Writer
io.StringWriter
} = os.Stderr
)
var (
inF, outF *string
strictF, verboseF *bool
)
func Flags(f *flag.FlagSet) {
inF = f.String("stream-in", "-", "Stream JSONL-encoded payloads from file")
verboseF = f.Bool("stream-verbose", false, "Print send/recv summaries (implied by verbose)")
strictF = f.Bool("stream-in-strict", false, "Reject unknown fields")
outF = f.String("stream-out", "-", "Stream JSONL-encoded results to file")
}
// JSONL converts streams of JSONL from stdin (or -stream-in) to Send calls, and
// streams of Recv results to JSONL on stdout (or -stream-out).
//
// This assumes that data implements a function like one of the following, for
// some types T and U:
//
// Send(*T) error AND Close() error
// OR SendAndClose(*T) error
// AND/OR Recv() (*U, error)
//
// Types T and U are identified via reflection, and use json marshaling.
func JSONL(data interface{}, verbose bool) error {
in, inclose := input()
out, outclose := output()
defer inclose()
defer outclose()
dec := json.NewDecoder(in)
if strictF != nil && *strictF {
dec.DisallowUnknownFields()
}
enc := json.NewEncoder(out)
enc.SetIndent("", " ")
err := reflectJSONL(dec, enc, data, verbose || (verboseF != nil && *verboseF))
if err != nil {
fmt.Fprintln(stderr, err.Error())
}
return nil
}
func nopClose() error { return nil }
func input() (r io.Reader, close func() error) {
if inF == nil || *inF == "-" {
return stdin, nopClose
}
if *inF != "" {
i, err := os.Open(*inF)
if err == nil {
return i, i.Close
}
fmt.Fprintln(stderr, err.Error())
}
return strings.NewReader(""), nopClose
}
func output() (w io.Writer, close func() error) {
if outF == nil || *outF == "-" {
return stdout, nopClose
}
if *outF != "" {
o, err := os.Create(*outF)
if err == nil {
return o, o.Close
}
fmt.Fprintln(stderr, err.Error())
}
return io.Discard, nopClose
}
func reflectJSONL(dec *json.Decoder, enc *json.Encoder, data interface{}, verbose bool) error {
p := func(string) (int, error) { return 0, nil }
if verbose {
p = stderr.WriteString
}
if data == nil {
return nil
}
stm := reflect.ValueOf(data)
sendandclose := false
send := stm.MethodByName("Send")
if !send.IsValid() {
send = stm.MethodByName("SendAndClose")
sendandclose = true
}
eg := errgroup.Group{}
if send.IsValid() {
payt := send.Type().In(0).Elem()
eg.Go(func() error {
for {
pay := reflect.New(payt)
err := dec.Decode(pay.Interface())
if err == io.EOF {
p("$") // end of input
break
}
if err != nil {
p("?") // bad input
return fmt.Errorf("input: %w", err)
}
p("^") // sent
out := send.Call([]reflect.Value{pay})
if out[0].IsValid() && !out[0].IsZero() {
err := out[0].Interface().(error)
if err == io.EOF {
p("#") // send EOF (closed)
break
}
p("!") // send error
return fmt.Errorf("send: %w", err)
}
}
if !sendandclose {
close := stm.MethodByName("Close")
if close.IsValid() {
out := close.Call(nil)
if out[0].IsValid() && !out[0].IsZero() {
return out[0].Interface().(error)
}
}
}
return nil
})
}
recv := stm.MethodByName("Recv")
if recv.IsValid() {
eg.Go(func() error {
for {
out := recv.Call(nil)
if out[1].IsValid() && !out[1].IsZero() {
err := out[1].Interface().(error)
if err == io.EOF {
p("#") // server closed
return nil
}
return err
}
p("v") // received
err := enc.Encode(out[0].Interface())
if err != nil {
return err
}
}
})
}
if send.IsValid() || recv.IsValid() {
defer p("\n")
}
return eg.Wait()
}