find.go

find.go

// Package bench is a package which contains
// programs of Go Benchmark Competition.
package bench

import (
	"bufio"
	"errors"
	"fmt"
	"os"
	"strings"
)

var errEmpty = errors.New("Empty haystack")
var cache = make(map[string]map[string]string)

// Find reads the text file on the `path`,
// finds the `s` words on the file and
// returns the row numbers and indices
// in the form of `r:c,r:c,...r:c`,
// at which the `s` word exists.
func Find(path, s string) (string, error) {
	if s == "" {
		return "", errEmpty
	}

	if v, ok := cache[path][s]; ok {
		return v, nil
	}

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

	r := ""
	sc := bufio.NewScanner(f)
	ln := 1
	for sc.Scan() {
		sl := sc.Text()

		x := 0
		for {

			i := strings.Index(sl[x:], s)
			if i == -1 {
				break
			}
			x += i + 1

			r += fmt.Sprintf(",%d:%d", ln, x-1)
		}

		ln++
	}

	if len(r) > 0 {
		r = r[1:]
	}

	if cache[path] == nil {
		cache[path] = make(map[string]string)
	}
	cache[path][s] = r

	return r, nil
}