gistfile1.txt

package bench

import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"io"
	"os"
	"strconv"
)

const (
	bufferSize = 100
)

//TODO doc
func Find(path, s string) (string, error) {
	if len(s) == 0 {
		return "", errors.New("")
	}

	f, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer f.Close()

	runes := []rune(s)

	myReader := &MyReader{
		reader:  bufio.NewReader(f),
		history: make([]rune, len(runes)),
	}

	row := 1
	col := 0

	var buf bytes.Buffer
	matchIndex := 0

	defer func() {
		if r := recover(); r != nil {
			fmt.Println("asdf: ", r)
			panic(r)
		}
	}()

	for {
		current, err := myReader.ReadRune()
		if err == io.EOF {
			break
		}
		if current == '\n' {
			// start fresh on next row
			row++
			col = -1
			matchIndex = 0
		} else if current == runes[matchIndex] {
			if matchIndex == len(runes)-1 {
				// rewind to start of match
				myReader.UnRead(matchIndex)
				col -= matchIndex
				matchIndex = 0

				// record match
				buf.WriteRune(',')
				buf.WriteString(strconv.FormatInt(int64(row), 10))
				buf.WriteRune(':')
				buf.WriteString(strconv.FormatInt(int64(col), 10))
			} else {
				// not done yet, advance match
				matchIndex++
			}
		} else if matchIndex > 0 {
			// failed match, rewind to start of match
			myReader.UnRead(matchIndex)
			col -= matchIndex
			matchIndex = 0
		}
		//next
		col++
	}

	result := buf.String()
	if len(result) > 0 {
		// ignore the first comma
		result = result[1:]
	}
	return result, nil
}

type MyReader struct {
	reader  *bufio.Reader
	history []rune
	// last returned rune
	currentIndex int
	// last read rune
	latestIndex int
}

func (m *MyReader) UnRead(offset int) {
	m.currentIndex -= offset
	if m.currentIndex < 0 {
		m.currentIndex += len(m.history)
	}
}

func (m *MyReader) ReadRune() (rune, error) {
	var err error
	doRead := m.currentIndex == m.latestIndex

	m.currentIndex++
	if m.currentIndex == len(m.history) {
		m.currentIndex = 0
	}

	if doRead {
		m.latestIndex = m.currentIndex
		m.history[m.latestIndex], _, err = m.reader.ReadRune()
	}

	return m.history[m.currentIndex], err
}