From 0998da8d871ce8d71cb4135d169315a354fe0897 Mon Sep 17 00:00:00 2001
From: Muaz Ahmad <m.ahmed_2000@hotmail.com>
Date: Thu, 10 Aug 2023 01:02:54 +0500
Subject: [PATCH] Basic chunk reading, format 0

---
 rtmp/chunk.go | 140 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 rtmp/chunk.go

diff --git a/rtmp/chunk.go b/rtmp/chunk.go
new file mode 100644
index 0000000..28cfef6
--- /dev/null
+++ b/rtmp/chunk.go
@@ -0,0 +1,140 @@
+package rtmp
+
+import (
+	"net"
+	"time"
+	"encoding/binary"
+)
+
+type chnk_stream struct {
+	timestamp uint32
+	last_msg_strm_id uint32
+	timedelta uint32
+}
+
+type message struct {
+//	msg_strm_id uint32
+	data []byte
+	curr_bytes_read uint32
+	timestamp uint32
+	msg_type uint8
+	msg_len uint32
+}
+
+
+func read_basic_header(conn net.Conn) (uint8, uint32, error) {
+	fmt_csid_byte := make([]byte, 1)
+	if _, err := conn.Read(fmt_csid_byte); err != nil {
+		return 0, 0, err
+	}
+	format := uint8(fmt_csid_byte[0] >> 6)
+	var csid uint32
+	switch fmt_csid_byte[0] & 0x3f {
+	case 0:
+		csid_true := make([]byte, 1)
+		if _, err := conn.Read(csid_true); err != nil {
+			return 0, 0, err
+		}
+		csid = uint32(csid_true[0]) + 64
+	case 1:
+		csid_true := make([]byte, 2)
+		if _, err := conn.Read(csid_true); err != nil {
+			return 0, 0, err
+		}
+		csid = uint32(binary.LittleEndian.Uint16(csid_true)) + 64
+	default:
+		csid = uint32(fmt_csid_byte[0] & 0x3f)
+	}
+	return format, csid, nil
+}
+
+func read_message_header_0(conn net.Conn, chnk_stream_ptr *chnk_stream, msg_ptr *message) (error) {
+	var extended_time bool
+	timestamp := make([]byte, 4)
+	if _, err := conn.Read(timestamp[1:]); err != nil {
+		return err
+	}
+	chnk_stream_ptr.timestamp = binary.BigEndian.Uint32(timestamp)
+	
+	if chnk_stream_ptr.timestamp ^ 0xffffff == 0 {
+		extended_time = true
+	}
+
+	msg_len := make([]byte, 4)
+	if _, err := conn.Read(msg_len[1:]); err != nil {
+		return err
+	}
+	msg_ptr.msg_len = binary.BigEndian.Uint32(msg_len)
+	msg_ptr.data = make([]byte, msg_ptr.msg_len)
+
+	msg_typeid := make([]byte, 1)
+	if _, err := conn.Read(msg_typeid); err != nil {
+		return err
+	}
+	msg_ptr.msg_type = msg_typeid[0]
+
+	msg_streamid := make([]byte, 4)
+	if _, err := conn.Read(msg_typeid); err != nil {
+		return err
+	}
+	chnk_stream_ptr.last_msg_strm_id = binary.BigEndian.Uint32(msg_streamid)
+
+	if extended_time {
+		if _, err := conn.Read(timestamp); err != nil {
+			return err
+		}
+		chnk_stream_ptr.timestamp = binary.BigEndian.Uint32(timestamp)
+	}
+	msg_ptr.timestamp = chnk_stream_ptr.timestamp
+
+	return nil
+}
+
+func read_chunk_data(conn net.Conn, msg_ptr *message, chnk_size uint32) (error) {
+	bytes_left := msg_ptr.msg_len - msg_ptr.curr_bytes_read
+	var buffer_end uint32
+	if bytes_left < chnk_size {
+		buffer_end = bytes_left + msg_ptr.curr_bytes_read + 1
+	} else {
+		buffer_end = chnk_size + msg_ptr.curr_bytes_read + 1
+	}
+	n, err := conn.Read(msg_ptr.data[msg_ptr.curr_bytes_read:buffer_end])
+	if err != nil {
+		return err
+	}
+	msg_ptr.curr_bytes_read += uint32(n)
+	return nil
+
+}
+
+func ReadChunk(conn net.Conn, open_chnkstrms map[uint32]*chnk_stream, open_msgs map[uint32]*message, chnk_size uint32) (*message, error){
+	conn.SetDeadline(time.Now().Add(10 * time.Second))
+
+	format, csid, err := read_basic_header(conn)
+	if err != nil {
+		return nil, err
+	}
+
+	switch format {
+	case 0:
+		chnkstream_ptr := new(chnk_stream)
+		open_chnkstrms[csid] = chnkstream_ptr
+		msg_ptr := new(message)
+
+		if err := read_message_header_0(conn, chnkstream_ptr, msg_ptr); err != nil {
+			return nil, err
+		}
+		if err := read_chunk_data(conn, msg_ptr, chnk_size); err != nil {
+			return nil, err
+		}
+		if msg_ptr.msg_len > chnk_size {
+			open_msgs[chnkstream_ptr.last_msg_strm_id] = msg_ptr
+			return nil, nil
+		} else {
+			return msg_ptr, nil
+		}
+	}
+
+	conn.SetDeadline(time.Time{})
+	return nil, nil
+}