Add GetSizeInBytes.

Useful to parse strings like 1GB or 12 mb into an unsigned integer number of bytes.

util.go

@@ -19,8 +19,10 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+	"unicode"
 
 	"github.com/BurntSushi/toml"
+	"github.com/spf13/cast"
 	jww "github.com/spf13/jwalterweatherman"
 	"gopkg.in/yaml.v2"
 )
@@ -139,3 +141,46 @@ func marshallConfigReader(in io.Reader, c map[string]interface{}, configType str
 
 	insensativiseMap(c)
 }
+
+func safeMul(a, b uint) uint {
+	c := a * b
+	if a > 1 && b > 1 && c/b != a {
+		return 0
+	}
+	return c
+}
+
+// parseSizeInBytes converts strings like 1GB or 12 mb into an unsigned integer number of bytes
+func parseSizeInBytes(sizeStr string) uint {
+	sizeStr = strings.TrimSpace(sizeStr)
+	lastChar := len(sizeStr) - 1
+	multiplier := uint(1)
+
+	if lastChar > 0 {
+		if sizeStr[lastChar] == 'b' || sizeStr[lastChar] == 'B' {
+			if lastChar > 1 {
+				switch unicode.ToLower(rune(sizeStr[lastChar-1])) {
+				case 'k':
+					multiplier = 1 << 10
+					sizeStr = strings.TrimSpace(sizeStr[:lastChar-1])
+				case 'm':
+					multiplier = 1 << 20
+					sizeStr = strings.TrimSpace(sizeStr[:lastChar-1])
+				case 'g':
+					multiplier = 1 << 30
+					sizeStr = strings.TrimSpace(sizeStr[:lastChar-1])
+				default:
+					multiplier = 1
+					sizeStr = strings.TrimSpace(sizeStr[:lastChar])
+				}
+			}
+		}
+	}
+
+	size := cast.ToInt(sizeStr)
+	if size < 0 {
+		size = 0
+	}
+
+	return safeMul(uint(size), multiplier)
+}

viper.go

@@ -313,6 +313,12 @@ func (v *viper) GetStringMapString(key string) map[string]string {
 	return cast.ToStringMapString(v.Get(key))
 }
 
+func GetSizeInBytes(key string) uint { return v.GetSizeInBytes(key) }
+func (v *viper) GetSizeInBytes(key string) uint {
+	sizeStr := cast.ToString(v.Get(key))
+	return parseSizeInBytes(sizeStr)
+}
+
 // Takes a single key and marshals it into a Struct
 func MarshalKey(key string, rawVal interface{}) error { return v.MarshalKey(key, rawVal) }
 func (v *viper) MarshalKey(key string, rawVal interface{}) error {

viper_test.go

@@ -362,3 +362,20 @@ func TestBoundCaseSensitivity(t *testing.T) {
 	assert.Equal(t, "green", Get("eyes"))
 
 }
+
+func TestSizeInBytes(t *testing.T) {
+	input := map[string]uint{
+		"":               0,
+		"b":              0,
+		"12 bytes":       0,
+		"200000000000gb": 0,
+		"12 b":           12,
+		"43 MB":          43 * (1 << 20),
+		"10mb":           10 * (1 << 20),
+		"1gb":            1 << 30,
+	}
+
+	for str, expected := range input {
+		assert.Equal(t, expected, parseSizeInBytes(str), str)
+	}
+}