Add Content-Length and Content-Disposition Header

for GetFileContent route.

pkg/nullio/content_length.go

@@ -0,0 +1,59 @@
+package nullio
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+)
+
+var ErrRegexMatching = errors.New("could not match content length")
+
+// ContentLengthWriter implements io.Writer.
+// It parses the size from the first line as Content Length Header and streams the following data to the Target.
+// The first line is expected to follow the format headerLineRegex.
+type ContentLengthWriter struct {
+	Target           http.ResponseWriter
+	contentLengthSet bool
+	firstLine        []byte
+}
+
+func (w *ContentLengthWriter) Write(p []byte) (count int, err error) {
+	if w.contentLengthSet {
+		count, err = w.Target.Write(p)
+		if err != nil {
+			err = fmt.Errorf("could not write to target: %w", err)
+		}
+		return count, err
+	}
+
+	for i, char := range p {
+		if char != '\n' {
+			continue
+		}
+
+		w.firstLine = append(w.firstLine, p[:i]...)
+		matches := headerLineRegex.FindSubmatch(w.firstLine)
+		if len(matches) < headerLineGroupName {
+			log.WithField("line", string(w.firstLine)).Error(ErrRegexMatching.Error())
+			return 0, ErrRegexMatching
+		}
+		size := string(matches[headerLineGroupSize])
+		w.Target.Header().Set("Content-Length", size)
+		w.contentLengthSet = true
+
+		if i < len(p)-1 {
+			count, err = w.Target.Write(p[i+1:])
+			if err != nil {
+				err = fmt.Errorf("could not write to target: %w", err)
+			}
+		}
+
+		return len(p[:i]) + 1 + count, err
+	}
+
+	if !w.contentLengthSet {
+		w.firstLine = append(w.firstLine, p...)
+	}
+
+	return len(p), nil
+}