cmd, ui: Move size parsing code and make it more robust

internal/ui/format.go

@@ -3,7 +3,10 @@ package ui
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"fmt"
+	"math/bits"
+	"strconv"
 	"time"
 )
 
@@ -56,6 +59,44 @@ func FormatSeconds(sec uint64) string {
 	return fmt.Sprintf("%d:%02d", min, sec)
 }
 
+// ParseBytes parses a size in bytes from s. It understands the suffixes
+// B, K, M, G and T for powers of 1024.
+func ParseBytes(s string) (int64, error) {
+	if s == "" {
+		return 0, errors.New("expected size, got empty string")
+	}
+
+	numStr := s[:len(s)-1]
+	var unit uint64 = 1
+
+	switch s[len(s)-1] {
+	case 'b', 'B':
+		// use initialized values, do nothing here
+	case 'k', 'K':
+		unit = 1024
+	case 'm', 'M':
+		unit = 1024 * 1024
+	case 'g', 'G':
+		unit = 1024 * 1024 * 1024
+	case 't', 'T':
+		unit = 1024 * 1024 * 1024 * 1024
+	default:
+		numStr = s
+	}
+	value, err := strconv.ParseInt(numStr, 10, 64)
+	if err != nil {
+		return 0, err
+	}
+
+	hi, lo := bits.Mul64(uint64(value), unit)
+	value = int64(lo)
+	if hi != 0 || value < 0 {
+		return 0, fmt.Errorf("ParseSize: %q: %w", numStr, strconv.ErrRange)
+	}
+
+	return value, nil
+}
+
 func ToJSONString(status interface{}) string {
 	buf := new(bytes.Buffer)
 	err := json.NewEncoder(buf).Encode(status)

internal/ui/format_test.go

@@ -1,6 +1,10 @@
 package ui
 
-import "testing"
+import (
+	"testing"
+
+	"github.com/restic/restic/internal/test"
+)
 
 func TestFormatBytes(t *testing.T) {
 	for _, c := range []struct {
@@ -36,3 +40,47 @@ func TestFormatPercent(t *testing.T) {
 		}
 	}
 }
+
+func TestParseBytes(t *testing.T) {
+	for _, tt := range []struct {
+		in       string
+		expected int64
+	}{
+		{"1024", 1024},
+		{"1024b", 1024},
+		{"1024B", 1024},
+		{"1k", 1024},
+		{"100k", 102400},
+		{"100K", 102400},
+		{"10M", 10485760},
+		{"100m", 104857600},
+		{"20G", 21474836480},
+		{"10g", 10737418240},
+		{"2T", 2199023255552},
+		{"2t", 2199023255552},
+		{"9223372036854775807", 1<<63 - 1},
+	} {
+		actual, err := ParseBytes(tt.in)
+		test.OK(t, err)
+		test.Equals(t, tt.expected, actual)
+	}
+}
+
+func TestParseBytesInvalid(t *testing.T) {
+	for _, s := range []string{
+		"",
+		" ",
+		"foobar",
+		"zzz",
+		"18446744073709551615", // 1<<64-1.
+		"9223372036854775807k", // 1<<63-1 kiB.
+		"9999999999999M",
+		"99999999999999999999",
+	} {
+		v, err := ParseBytes(s)
+		if err == nil {
+			t.Errorf("wanted error for invalid value %q, got nil", s)
+		}
+		test.Equals(t, int64(0), v)
+	}
+}