websocket: add type for continuous (fragmented) frame

A type Frames is actually a wrapper to slice of frame.  We prefer if
user is not directly access to underlying frames but focus on payload
instead.

1 files changed, 92 insertions, 0 deletions

diff --git a/lib/websocket/frames.go b/lib/websocket/frames.go
new file mode 100644
index 00000000..a16886c4
--- /dev/null
+++ b/lib/websocket/frames.go
@@ -0,0 +1,92 @@
+// Copyright 2019, Shulhan <ms@kilabit.info>. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package websocket
+
+//
+// Frames represent continuous (fragmented) frame.
+//
+// A fragmented message consists of a single frame with the FIN bit clear and
+// an opcode other than 0, followed by zero or more frames with the FIN bit
+// clear and the opcode set to 0, and terminated by a single frame with the
+// FIN bit set and an opcode of 0.
+//
+type Frames struct {
+	v []*Frame
+}
+
+//
+// Append a frame as part of continuous frame.
+// This function does not check if the appended frame is valid (i.e. zero
+// operation code on second or later frame).
+//
+func (frames *Frames) Append(f *Frame) {
+	if f != nil {
+		frames.v = append(frames.v, f)
+	}
+}
+
+//
+// Get frame at specific index or nil if index out of range.
+//
+func (frames *Frames) Get(x int) *Frame {
+	if x < 0 || x >= len(frames.v) {
+		return nil
+	}
+	return frames.v[x]
+}
+
+//
+// IsClosed will return true if one of the frame is control CLOSE frame.
+//
+func (frames *Frames) IsClosed() bool {
+	if len(frames.v) == 0 {
+		return false
+	}
+	for x := 0; x < len(frames.v); x++ {
+		if frames.v[x].Opcode == OpCodeClose {
+			return true
+		}
+	}
+	return false
+}
+
+//
+// Len return the number of frame.
+//
+func (frames *Frames) Len() int {
+	return len(frames.v)
+}
+
+//
+// Payload return the concatenation of continuous data frame's payload.
+//
+// The first frame must be a data frame, either text or binary, otherwise it
+// will be considered empty payload, even if frames list is not empty.
+//
+// Any control CLOSE frame of frame with Fin set will considered the last
+// frame.
+//
+func (frames *Frames) Payload() (payload []byte) {
+	if len(frames.v) == 0 {
+		return
+	}
+	if !frames.v[0].IsData() {
+		return
+	}
+
+	for x := 0; x < len(frames.v); x++ {
+		if frames.v[x].Opcode == OpCodeClose {
+			break
+		}
+
+		payload = append(payload, frames.v[x].Payload...)
+
+		if frames.v[x].Fin == FrameIsFinished {
+			break
+		}
+	}
+
+	return
+}