added test util

text.go

@@ -1,6 +1,10 @@
 package toolbox
 
-import "unicode"
+import (
+	"bufio"
+	"io"
+	"unicode"
+)
 
 //IsASCIIText return true if supplied string does not have binary data
 func IsASCIIText(candidate string) bool {
@@ -38,16 +42,58 @@ func TerminatedSplitN(text string, fragmentCount int, terminator string) []strin
 	lowerBound := 0
 	for i := fragmentSize - 1; i < len(text); i++ {
 		isLast := i+1 == len(text)
-		isAtLeastOfFragementSize := i-lowerBound >= fragmentSize
+		isAtLeastOfFragmentSize := i-lowerBound >= fragmentSize
 		isNewLine := string(text[i:i+len(terminator)]) == terminator
-		if (isAtLeastOfFragementSize && isNewLine) || isLast {
+		if (isAtLeastOfFragmentSize && isNewLine) || isLast {
 			result = append(result, string(text[lowerBound:i+1]))
 			lowerBound = i + 1
 		}
 	}
 	return result
 }
 
+//SplitTextStream divides reader supplied text by number of specified line
+func SplitTextStream(reader io.Reader, writerProvider func() io.WriteCloser, elementCount int) error {
+	scanner := bufio.NewScanner(reader)
+	var writer io.WriteCloser
+	counter := 0
+	var err error
+	if elementCount == 0 {
+		elementCount = 1
+	}
+	for scanner.Scan() {
+
+		if writer == nil {
+			writer = writerProvider()
+		}
+		data := scanner.Bytes()
+		if err = scanner.Err(); err != nil {
+			return err
+		}
+
+		if counter > 0 {
+			if _, err = writer.Write([]byte{'\n'}); err != nil {
+				return err
+			}
+		}
+		if _, err = writer.Write(data); err != nil {
+			return err
+		}
+		counter++
+		if counter == elementCount {
+			if err := writer.Close(); err != nil {
+				return err
+			}
+			counter = 0
+			writer = nil
+		}
+	}
+	if writer != nil {
+		return writer.Close()
+	}
+	return nil
+}
+
 const (
 	CaseUpper = iota
 	CaseLower

text_test.go

@@ -1,8 +1,10 @@
 package toolbox
 
 import (
+	"bytes"
 	"fmt"
 	"github.com/stretchr/testify/assert"
+	"io"
 	"strings"
 	"testing"
 )
@@ -163,6 +165,88 @@ func TestTerminatedSplitN(t *testing.T) {
 	}
 }
 
+type testWriter struct {
+	*bytes.Buffer
+	data *[]string
+}
+
+func (t *testWriter) Close() error {
+	*t.data = append(*t.data, t.String())
+	return nil
+}
+
+func newTestWriter(data *[]string) io.WriteCloser {
+	return &testWriter{
+		data:   data,
+		Buffer: new(bytes.Buffer),
+	}
+}
+
+func TestSplitTextStream(t *testing.T) {
+
+	var data = make([]byte, 0)
+	for i := 0; i < 9; i++ {
+		data = append(data, []byte(fmt.Sprintf("%v %v\n", strings.Repeat("x", 2), i))...)
+	}
+	text := string(data)
+
+	useCases := []struct {
+		description string
+		elements    int
+		expect      []string
+	}{
+		{
+			description: "no more then 4 lines case",
+			elements:    4,
+			expect: []string{
+				"xx 0\nxx 1\nxx 2\nxx 3", "xx 4\nxx 5\nxx 6\nxx 7", "xx 8",
+			},
+		},
+		{
+			description: "3 elements each",
+			elements:    3,
+			expect: []string{
+				"xx 0\nxx 1\nxx 2", "xx 3\nxx 4\nxx 5", "xx 6\nxx 7\nxx 8",
+			},
+		},
+		{
+			description: "9 elements",
+			elements:    1,
+			expect: []string{
+				"xx 0", "xx 1", "xx 2", "xx 3", "xx 4", "xx 5", "xx 6", "xx 7", "xx 8",
+			},
+		},
+		{
+			description: "9 elements",
+			elements:    0,
+			expect: []string{
+				"xx 0", "xx 1", "xx 2", "xx 3", "xx 4", "xx 5", "xx 6", "xx 7", "xx 8",
+			},
+		},
+		{
+			description: "1 elements",
+			elements:    10,
+			expect: []string{
+				"xx 0\nxx 1\nxx 2\nxx 3\nxx 4\nxx 5\nxx 6\nxx 7\nxx 8",
+			},
+		},
+		{
+			description: "1 elements",
+			elements:    9,
+			expect: []string{
+				"xx 0\nxx 1\nxx 2\nxx 3\nxx 4\nxx 5\nxx 6\nxx 7\nxx 8",
+			},
+		},
+	}
+
+	for _, useCase := range useCases {
+		var data = make([]string, 0)
+		err := SplitTextStream(strings.NewReader(text), func() io.WriteCloser { return newTestWriter(&data) }, useCase.elements)
+		assert.Nil(t, err)
+		assert.EqualValues(t, useCase.expect, data, useCase.description)
+	}
+}
+
 func Test_CaseFormat(t *testing.T) {
 	var useCases = []struct {
 		description string