GmisubToAtom: output result to any io.Writer rather than return a string

2 files changed, 16 insertions, 7 deletions

diff --git a/gemini/gemtext/sub.go b/gemini/gemtext/sub.go
index 1247643..365d41b 100644
--- a/gemini/gemtext/sub.go
+++ b/gemini/gemtext/sub.go
@@ -3,6 +3,7 @@ package gemtext
 import (
 	"bytes"
 	"html/template"
+	"io"
 	"net/url"
 	"regexp"
 	"strconv"
@@ -14,12 +15,17 @@ import (
 //
 // It identifies feed fields and entries according to the specification at
 // gemini://gemini.circumlunar.space/docs/companion/subscription.gmi
-func GmisubToAtom(doc Document, location url.URL) string {
-	buf := &bytes.Buffer{}
-	if err := atomTmpl.Execute(buf, parseGemSub(doc, &location)); err != nil {
-		panic(err)
+func GmisubToAtom(doc Document, location url.URL, out io.Writer) error {
+	if _, err := out.Write([]byte(`<?xml version="1.0" encoding="utf-8"?>`)); err != nil {
+		return err
 	}
-	return `<?xml version="1.0" encoding="utf-8"?>` + "\n" + buf.String()
+	if _, err := out.Write([]byte{'\n'}); err != nil {
+		return err
+	}
+	if err := atomTmpl.Execute(out, parseGemSub(doc, &location)); err != nil {
+		return err
+	}
+	return nil
 }
 
 type gmiSub struct {
diff --git a/gemini/gemtext/sub_test.go b/gemini/gemtext/sub_test.go
index 26f98ed..f080705 100644
--- a/gemini/gemtext/sub_test.go
+++ b/gemini/gemtext/sub_test.go
@@ -51,8 +51,11 @@ func TestGemsubToAtom(t *testing.T) {
 			if err != nil {
 				t.Fatal(err)
 			}
-			xml := GmisubToAtom(doc, *loc)
-			if xml != test.output {
+			out := &bytes.Buffer{}
+			if err := GmisubToAtom(doc, *loc, out); err != nil {
+				t.Fatal(err)
+			}
+			if out.String() != test.output {
 				t.Fatal("mismatched output")
 			}
 		})