pkg/units: Add FromHumanSize

This does the "reverse" of HumanSize, i.e. maps a string to an int64
using SI prefixes for the extension.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <[email protected]> (github: alexlarsson)

pkg/units/size.go

@@ -21,6 +21,42 @@ func HumanSize(size int64) string {
 	return fmt.Sprintf("%.4g %s", sizef, units[i])
 }
 
+// FromHumanSize returns an integer from a human-readable specification of a size
+// using SI standard (eg. "44kB", "17MB")
+func FromHumanSize(size string) (int64, error) {
+	re, error := regexp.Compile("^(\\d+)([kKmMgGtTpP])?[bB]?$")
+	if error != nil {
+		return -1, fmt.Errorf("%s does not specify not a size", size)
+	}
+
+	matches := re.FindStringSubmatch(size)
+
+	if len(matches) != 3 {
+		return -1, fmt.Errorf("Invalid size: '%s'", size)
+	}
+
+	theSize, error := strconv.ParseInt(matches[1], 10, 0)
+	if error != nil {
+		return -1, error
+	}
+
+	unit := strings.ToLower(matches[2])
+
+	if unit == "k" {
+		theSize *= 1000
+	} else if unit == "m" {
+		theSize *= 1000 * 1000
+	} else if unit == "g" {
+		theSize *= 1000 * 1000 * 1000
+	} else if unit == "t" {
+		theSize *= 1000 * 1000 * 1000 * 1000
+	} else if unit == "p" {
+		theSize *= 1000 * 1000 * 1000 * 1000 * 1000
+	}
+
+	return theSize, nil
+}
+
 // Parses a human-readable string representing an amount of RAM
 // in bytes, kibibytes, mebibytes or gibibytes, and returns the
 // number of bytes, or -1 if the string is unparseable.

pkg/units/size_test.go

@@ -20,6 +20,41 @@ func TestHumanSize(t *testing.T) {
 	}
 }
 
+func TestFromHumanSize(t *testing.T) {
+	assertFromHumanSize(t, "32", false, 32)
+	assertFromHumanSize(t, "32b", false, 32)
+	assertFromHumanSize(t, "32B", false, 32)
+	assertFromHumanSize(t, "32k", false, 32*1000)
+	assertFromHumanSize(t, "32K", false, 32*1000)
+	assertFromHumanSize(t, "32kb", false, 32*1000)
+	assertFromHumanSize(t, "32Kb", false, 32*1000)
+	assertFromHumanSize(t, "32Mb", false, 32*1000*1000)
+	assertFromHumanSize(t, "32Gb", false, 32*1000*1000*1000)
+	assertFromHumanSize(t, "32Tb", false, 32*1000*1000*1000*1000)
+	assertFromHumanSize(t, "8Pb", false, 8*1000*1000*1000*1000*1000)
+
+	assertFromHumanSize(t, "", true, -1)
+	assertFromHumanSize(t, "hello", true, -1)
+	assertFromHumanSize(t, "-32", true, -1)
+	assertFromHumanSize(t, " 32 ", true, -1)
+	assertFromHumanSize(t, "32 mb", true, -1)
+	assertFromHumanSize(t, "32m b", true, -1)
+	assertFromHumanSize(t, "32bm", true, -1)
+}
+
+func assertFromHumanSize(t *testing.T, size string, expectError bool, expectedBytes int64) {
+	actualBytes, err := FromHumanSize(size)
+	if (err != nil) && !expectError {
+		t.Errorf("Unexpected error parsing '%s': %s", size, err)
+	}
+	if (err == nil) && expectError {
+		t.Errorf("Expected to get an error parsing '%s', but got none (bytes=%d)", size, actualBytes)
+	}
+	if actualBytes != expectedBytes {
+		t.Errorf("Expected '%s' to parse as %d bytes, got %d", size, expectedBytes, actualBytes)
+	}
+}
+
 func TestRAMInBytes(t *testing.T) {
 	assertRAMInBytes(t, "32", false, 32)
 	assertRAMInBytes(t, "32b", false, 32)