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// Copyright 2021 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package eventchannel
import (
"encoding/binary"
"fmt"
"io"
"os"
"time"
"google.golang.org/protobuf/proto"
pb "gvisor.dev/gvisor/pkg/eventchannel/eventchannel_go_proto"
)
// eventProcessor carries display state across multiple events.
type eventProcessor struct {
filtering bool
// filtered is the number of events omitted since printing the last matching
// event. Only meaningful when filtering == true.
filtered uint64
// allowlist is the set of event names to display. If empty, all events are
// displayed.
allowlist map[string]bool
}
// newEventProcessor creates a new EventProcessor with filters.
func newEventProcessor(filters []string) *eventProcessor {
e := &eventProcessor{
filtering: len(filters) > 0,
allowlist: make(map[string]bool),
}
for _, f := range filters {
e.allowlist[f] = true
}
return e
}
// processOne reads, parses and displays a single event from the event channel.
//
// The event channel is a stream of (msglen, payload) packets; this function
// processes a single such packet. The msglen is a uvarint-encoded length for
// the associated payload. The payload is a binary-encoded 'Any' protobuf, which
// in turn encodes an arbitrary event protobuf.
func (e *eventProcessor) processOne(src io.Reader, out *os.File) error {
// Read and parse the msglen.
lenbuf := make([]byte, binary.MaxVarintLen64)
if _, err := io.ReadFull(src, lenbuf); err != nil {
return err
}
msglen, consumed := binary.Uvarint(lenbuf)
if consumed <= 0 {
return fmt.Errorf("couldn't parse the message length")
}
// Read the payload.
buf := make([]byte, msglen)
// Copy any unused bytes from the len buffer into the payload buffer. These
// bytes are actually part of the payload.
extraBytes := copy(buf, lenbuf[consumed:])
if _, err := io.ReadFull(src, buf[extraBytes:]); err != nil {
return err
}
// Unmarshal the payload into an "Any" protobuf, which encodes the actual
// event.
encodedEv := emptyAny()
if err := proto.Unmarshal(buf, encodedEv); err != nil {
return fmt.Errorf("failed to unmarshal 'any' protobuf message: %v", err)
}
var ev pb.DebugEvent
if err := (encodedEv).UnmarshalTo(&ev); err != nil {
return fmt.Errorf("failed to decode 'any' protobuf message: %v", err)
}
if e.filtering && e.allowlist[ev.Name] {
e.filtered++
return nil
}
if e.filtering && e.filtered > 0 {
if e.filtered == 1 {
fmt.Fprintf(out, "... filtered %d event ...\n\n", e.filtered)
} else {
fmt.Fprintf(out, "... filtered %d events ...\n\n", e.filtered)
}
e.filtered = 0
}
// Extract the inner event and display it. Example:
//
// 2017-10-04 14:35:05.316180374 -0700 PDT m=+1.132485846
// cloud_gvisor.MemoryUsage {
// total: 23822336
// }
fmt.Fprintf(out, "%v\n%v {\n", time.Now(), ev.Name)
fmt.Fprintf(out, "%v", ev.Text)
fmt.Fprintf(out, "}\n\n")
return nil
}
// ProcessAll reads, parses and displays all events from src. The events are
// displayed to out.
func ProcessAll(src io.Reader, filters []string, out *os.File) error {
ep := newEventProcessor(filters)
for {
switch err := ep.processOne(src, out); err {
case nil:
continue
case io.EOF:
return nil
default:
return err
}
}
}
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