virt: Allow more than 26 disks

resources/virt.go

@@ -998,7 +998,7 @@ func (d *diskDevice) GetXML(idx int) string {
 	b += "<disk type='file' device='disk'>"
 	b += fmt.Sprintf("<driver name='qemu' type='%s'/>", d.Type)
 	b += fmt.Sprintf("<source file='%s'/>", source)
-	b += fmt.Sprintf("<target dev='vd%s' bus='virtio'/>", (string)(idx+97)) // TODO: 26, 27... should be 'aa', 'ab'...
+	b += fmt.Sprintf("<target dev='vd%s' bus='virtio'/>", numToAlpha(idx))
 	b += "</disk>"
 	return b
 }
@@ -1009,7 +1009,7 @@ func (d *cdRomDevice) GetXML(idx int) string {
 	b += "<disk type='file' device='cdrom'>"
 	b += fmt.Sprintf("<driver name='qemu' type='%s'/>", d.Type)
 	b += fmt.Sprintf("<source file='%s'/>", source)
-	b += fmt.Sprintf("<target dev='hd%s' bus='ide'/>", (string)(idx+97)) // TODO: 26, 27... should be 'aa', 'ab'...
+	b += fmt.Sprintf("<target dev='hd%s' bus='ide'/>", numToAlpha(idx))
 	b += "<readonly/>"
 	b += "</disk>"
 	return b
@@ -1195,3 +1195,12 @@ func expandHome(p string) (string, error) {
 
 	return p, nil
 }
+
+func numToAlpha(idx int) string {
+	var mod = idx % 26
+	var div = idx / 26
+	if div > 0 {
+		return numToAlpha(div-1) + string(rune(mod+int('a')))
+	}
+	return string(rune(mod + int('a')))
+}

resources/virt_test.go

@@ -46,3 +46,25 @@ func TestExpandHome(t *testing.T) {
 		}
 	}
 }
+
+func TestNumToAlpha(t *testing.T) {
+	var numToAlphaTests = []struct {
+		number int
+		result string
+	}{
+		{0, "a"},
+		{25, "z"},
+		{26, "aa"},
+		{27, "ab"},
+		{702, "aaa"},
+		{703, "aab"},
+		{63269, "cool"},
+	}
+
+	for _, test := range numToAlphaTests {
+		actual := numToAlpha(test.number)
+		if actual != test.result {
+			t.Errorf("numToAlpha(%d): expected %s, actual %s", test.number, test.result, actual)
+		}
+	}
+}