gobench Find Words

find.go

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

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

func Find(path, s string) (string, error) {
	if s == "" {
		return "", errors.New("empty string to search for")
	}

	var f, err = os.Open(path)
	if err != nil {
		return "", fmt.Errorf("failed to open file: %v", err)
	}

	var (
		lens    = len(s)
		sb      = []byte(s)
		answer  = make([]byte, 0, 1<<16)
		lineno  int64
		first   = true
		scanner = bufio.NewScanner(f)
	)
	for scanner.Scan() {
		lineno++
		var line = scanner.Bytes()
		if lens > len(line) {
			continue
		}
		for i := range line[:len(line)-lens] {
			if bytes.HasPrefix(line[i:], sb) {
				if !first {
					answer = append(answer, ',')
				}
				answer = strconv.AppendInt(answer, lineno, 10)
				answer = append(answer, ':')
				answer = strconv.AppendInt(answer, int64(i), 10)
				first = false
			}
		}
	}
	return string(answer), nil
}