implements gzip interpolation func

config/interpolate_funcs.go

@@ -1,6 +1,8 @@
 package config
 
 import (
+	"bytes"
+	"compress/gzip"
 	"crypto/md5"
 	"crypto/sha1"
 	"crypto/sha256"
@@ -57,6 +59,7 @@ func Funcs() map[string]ast.Function {
 		"basename":     interpolationFuncBasename(),
 		"base64decode": interpolationFuncBase64Decode(),
 		"base64encode": interpolationFuncBase64Encode(),
+		"base64gzip":   interpolationFuncBase64Gzip(),
 		"base64sha256": interpolationFuncBase64Sha256(),
 		"base64sha512": interpolationFuncBase64Sha512(),
 		"ceil":         interpolationFuncCeil(),
@@ -1178,6 +1181,32 @@ func interpolationFuncBase64Decode() ast.Function {
 	}
 }
 
+// interpolationFuncBase64Gzip implements the "gzip" function that allows gzip
+// compression encoding the result using base64
+func interpolationFuncBase64Gzip() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeString},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			s := args[0].(string)
+
+			var b bytes.Buffer
+			gz := gzip.NewWriter(&b)
+			if _, err := gz.Write([]byte(s)); err != nil {
+				return "", fmt.Errorf("failed to write gzip raw data: '%s'", s)
+			}
+			if err := gz.Flush(); err != nil {
+				return "", fmt.Errorf("failed to flush gzip writer: '%s'", s)
+			}
+			if err := gz.Close(); err != nil {
+				return "", fmt.Errorf("failed to close gzip writer: '%s'", s)
+			}
+
+			return base64.StdEncoding.EncodeToString(b.Bytes()), nil
+		},
+	}
+}
+
 // interpolationFuncLower implements the "lower" function that does
 // string lower casing.
 func interpolationFuncLower() ast.Function {

config/interpolate_funcs_test.go

@@ -2215,6 +2215,18 @@ func TestInterpolateFuncTrimSpace(t *testing.T) {
 	})
 }
 
+func TestInterpolateFuncBase64Gzip(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${base64gzip("test")}`,
+				"H4sIAAAAAAAA/ypJLS4BAAAA//8BAAD//wx+f9gEAAAA",
+				false,
+			},
+		},
+	})
+}
+
 func TestInterpolateFuncBase64Sha256(t *testing.T) {
 	testFunction(t, testFunctionConfig{
 		Cases: []testFunctionCase{