package sentry import ( "bytes" "os" "sync" ) type sourceReader struct { mu sync.Mutex cache map[string][][]byte } func newSourceReader() sourceReader { return sourceReader{ cache: make(map[string][][]byte), } } func (sr *sourceReader) readContextLines(filename string, line, context int) ([][]byte, int) { sr.mu.Lock() defer sr.mu.Unlock() lines, ok := sr.cache[filename] if !ok { data, err := os.ReadFile(filename) if err != nil { sr.cache[filename] = nil return nil, 0 } lines = bytes.Split(data, []byte{'\n'}) sr.cache[filename] = lines } return sr.calculateContextLines(lines, line, context) } func (sr *sourceReader) calculateContextLines(lines [][]byte, line, context int) ([][]byte, int) { // Stacktrace lines are 1-indexed, slices are 0-indexed line-- // contextLine points to a line that caused an issue itself, in relation to // returned slice. contextLine := context if lines == nil || line >= len(lines) || line < 0 { return nil, 0 } if context < 0 { context = 0 contextLine = 0 } start := line - context if start < 0 { contextLine += start start = 0 } end := line + context + 1 if end > len(lines) { end = len(lines) } return lines[start:end], contextLine }