Beispiel #1
0
func headLines(file *hdfs.FileReader, numLines int64) {
	reader := bufio.NewReader(file)

	var newlines, offset int64
	for newlines < numLines {
		b, err := reader.ReadByte()
		if err == io.EOF {
			offset = -1
			break
		} else if err != nil {
			fatal(err)
		}

		if b == '\n' {
			newlines++
		}

		offset++
	}

	_, err := file.Seek(0, 0)
	if err != nil {
		fatal(err)
	}

	if offset < 0 {
		io.Copy(os.Stdout, file)
	} else {
		io.CopyN(os.Stdout, file, offset)
	}
}
Beispiel #2
0
func tailLines(file *hdfs.FileReader, numLines int64) {
	fileSize := file.Stat().Size()
	searchPoint := file.Stat().Size() - tailSearchSize
	if searchPoint < 0 {
		searchPoint = 0
	}

	var printOffset int64
	for searchPoint >= 0 {
		section := bufio.NewReader(io.NewSectionReader(file, searchPoint, tailSearchSize))
		off := searchPoint
		newlines := make([]int64, 0, tailSearchSize/64)

		b, err := section.ReadByte()
		for err == nil {
			if b == '\n' && (off+1 != fileSize) {
				newlines = append(newlines, off)
			}

			off++
			b, err = section.ReadByte()
		}

		if err != nil && err != io.EOF {
			fatal(err)
		}

		foundNewlines := int64(len(newlines))
		if foundNewlines >= numLines {
			printOffset = newlines[foundNewlines-numLines] + 1
			break
		}

		numLines -= foundNewlines
		searchPoint -= tailSearchSize
	}

	_, err := file.Seek(printOffset, 0)
	if err != nil {
		fatal(err)
	}

	io.Copy(os.Stdout, file)
}