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context.go
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context.go
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// Licensed to Elasticsearch B.V. under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. Elasticsearch B.V. licenses this file to you 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 stacktrace // import "go.atatus.com/agent/stacktrace"
import (
"bufio"
"net/http"
"os"
"go.atatus.com/agent/model"
)
// SetContext sets the source context for the given stack frames,
// with the specified number of pre- and post- lines.
func SetContext(setter ContextSetter, frames []model.StacktraceFrame, pre, post int) error {
for i := 0; i < len(frames); i++ {
if err := setter.SetContext(&frames[i], pre, post); err != nil {
return err
}
}
return nil
}
// ContextSetter is an interface that can be used for setting the source
// context for a stack frame.
type ContextSetter interface {
// SetContext sets the source context for the given stack frame,
// with the specified number of pre- and post- lines.
SetContext(frame *model.StacktraceFrame, pre, post int) error
}
// FileSystemContextSetter returns a ContextSetter that sets context
// by reading file contents from the provided http.FileSystem.
func FileSystemContextSetter(fs http.FileSystem) ContextSetter {
if fs == nil {
panic("fs is nil")
}
return &fileSystemContextSetter{fs}
}
type fileSystemContextSetter struct {
http.FileSystem
}
func (s *fileSystemContextSetter) SetContext(frame *model.StacktraceFrame, pre, post int) error {
if frame.Line <= 0 {
return nil
}
f, err := s.Open(frame.AbsolutePath)
if err != nil {
if os.IsNotExist(err) {
return nil
}
return err
}
defer f.Close()
var lineno int
var line string
preLines := make([]string, 0, pre)
postLines := make([]string, 0, post)
scanner := bufio.NewScanner(f)
for scanner.Scan() {
lineno++
if lineno > frame.Line+post {
break
}
switch {
case lineno == frame.Line:
line = scanner.Text()
case lineno < frame.Line && lineno >= frame.Line-pre:
preLines = append(preLines, scanner.Text())
case lineno > frame.Line && lineno <= frame.Line+post:
postLines = append(postLines, scanner.Text())
}
}
if err := scanner.Err(); err != nil {
return err
}
frame.ContextLine = line
frame.PreContext = preLines
frame.PostContext = postLines
return nil
}