Boundary reader - long lines processing fixed (#200)

* Boundary reader - long lines processing fixed
* boundaryReader.Next - buffer allocation only for lines longer than buffer

Co-authored-by: Pavel Bazika <pavel.bazika@icewarp.com>

boundary.go

@@ -181,10 +181,25 @@ func (b *boundaryReader) Next() (bool, error) {
 		_, _ = io.Copy(ioutil.Discard, b)
 	}
 	for {
-		line, err := b.r.ReadSlice('\n')
-		if err != nil && err != io.EOF {
-			return false, errors.WithStack(err)
+		var line []byte = nil
+		var err error
+		for {
+			// Read whole line, handle extra long lines in cycle
+			var segment []byte
+			segment, err = b.r.ReadSlice('\n')
+			if line == nil {
+				line = segment
+			} else {
+				line = append(line, segment...)
+			}
+
+			if err == nil || err == io.EOF {
+				break
+			} else if err != bufio.ErrBufferFull || len(segment) == 0 {
+				return false, errors.WithStack(err)
+			}
 		}
+
 		if len(line) > 0 && (line[0] == '\r' || line[0] == '\n') {
 			// Blank line
 			continue

boundary_test.go

@@ -477,6 +477,24 @@ func TestBoundaryReaderReadErrors(t *testing.T) {
 	}
 }
 
+// TestBoundaryReaderLongLine checks that boundaryReader can read lines longer than the `peekBufferSize`.
+func TestBoundaryReaderLongLine(t *testing.T) {
+	data := bytes.Repeat([]byte{1}, 7*1024)
+	data[6*1024] = '\n'
+
+	br := &boundaryReader{
+		r: bufio.NewReader(bytes.NewReader(data)),
+	}
+
+	next, err := br.Next()
+	if next {
+		t.Fatal("Next() should have returned false, failed")
+	}
+	if err != nil {
+		t.Fatal("Next() should have returned no error, failed")
+	}
+}
+
 // TestReadLenNotCap checks that the `boundaryReader` `io.Reader` implementation fills the provided
 // slice based on its length (as per the `io.Reader` documentation), and not its capacity.
 func TestReadLenNotCap(t *testing.T) {