Add bytesranger package

Author: hioki-daichi

kadai3-2/hioki-daichi/bytesranger/bytesranger.go

@@ -0,0 +1,68 @@
+package bytesranger
+
+import (
+	"errors"
+	"fmt"
+)
+
+var (
+	errZeroDivision       = errors.New("bytesranger: zero division error")
+	errNumberOfPartitions = errors.New("bytesranger: numberOfPartitions must be less than or equal to number")
+)
+
+// Split splits the number into the specified numberOfPartitions and changes to bytes range strings.
+func Split(number int, numberOfPartitions int) ([]string, error) {
+	err := validate(number, numberOfPartitions)
+	if err != nil {
+		return nil, err
+	}
+
+	return toBytesRangeStrings(toBytesRanges(number, numberOfPartitions)), nil
+}
+
+type bytesRange struct {
+	first int
+	last  int
+}
+
+func validate(number int, numberOfPartitions int) error {
+	if numberOfPartitions == 0 {
+		return errZeroDivision
+	}
+
+	if number < numberOfPartitions {
+		return errNumberOfPartitions
+	}
+
+	return nil
+}
+
+func toBytesRanges(number int, numberOfPartitions int) []bytesRange {
+	ret := make([]bytesRange, 0)
+
+	numberPerUnit := number / numberOfPartitions
+
+	n := 0
+
+	for i := numberOfPartitions; i > 0; i-- {
+		br := bytesRange{first: n, last: n + numberPerUnit - 1}
+		ret = append(ret, br)
+		n += numberPerUnit
+	}
+
+	if rem := number % numberOfPartitions; rem != 0 {
+		ret[len(ret)-1].last += rem
+	}
+
+	return ret
+}
+
+func toBytesRangeStrings(bytesRanges []bytesRange) []string {
+	ret := make([]string, 0)
+
+	for _, br := range bytesRanges {
+		ret = append(ret, fmt.Sprintf("bytes=%d-%d", br.first, br.last))
+	}
+
+	return ret
+}

kadai3-2/hioki-daichi/bytesranger/bytesranger_test.go

@@ -0,0 +1,59 @@
+package bytesranger
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestBytesranger_Split(t *testing.T) {
+	cases := map[string]struct {
+		number             int
+		numberOfPartitions int
+		expected           []string
+	}{
+		"split 5 into 1": {number: 5, numberOfPartitions: 1, expected: []string{"bytes=0-4"}},
+		"split 5 into 2": {number: 5, numberOfPartitions: 2, expected: []string{"bytes=0-1", "bytes=2-4"}},
+		"split 5 into 3": {number: 5, numberOfPartitions: 3, expected: []string{"bytes=0-0", "bytes=1-1", "bytes=2-4"}},
+		"split 5 into 4": {number: 5, numberOfPartitions: 4, expected: []string{"bytes=0-0", "bytes=1-1", "bytes=2-2", "bytes=3-4"}},
+		"split 5 into 5": {number: 5, numberOfPartitions: 5, expected: []string{"bytes=0-0", "bytes=1-1", "bytes=2-2", "bytes=3-3", "bytes=4-4"}},
+	}
+
+	for n, c := range cases {
+		c := c
+		t.Run(n, func(t *testing.T) {
+			t.Parallel()
+
+			number := c.number
+			numberOfPartitions := c.numberOfPartitions
+			expected := c.expected
+
+			actual, err := Split(number, numberOfPartitions)
+			if err != nil {
+				t.Fatalf("err %s", err)
+			}
+			if !reflect.DeepEqual(actual, expected) {
+				t.Errorf(`expected="%s" actual="%s"`, expected, actual)
+			}
+		})
+	}
+}
+
+func TestBytesranger_Split_ZeroDivisionError(t *testing.T) {
+	actual, err := Split(10, 0)
+	if len(actual) != 0 {
+		t.Fatalf("expected that length is 0, but %d", len(actual))
+	}
+	if err != errZeroDivision {
+		t.Errorf(`expected="%v" actual="%v"`, errZeroDivision, err)
+	}
+}
+
+func TestBytesranger_Split_NumberOfPartitionsError(t *testing.T) {
+	actual, err := Split(10, 11)
+	if len(actual) != 0 {
+		t.Fatalf("expected that length is 0, but %d", len(actual))
+	}
+	if err != errNumberOfPartitions {
+		t.Errorf(`expected="%v" actual="%v"`, errNumberOfPartitions, err)
+	}
+}