From 94bd146e77d065a5d28bc3426a89dbc08cd6e03d Mon Sep 17 00:00:00 2001
From: Muaz Ahmad <m.ahmed_2000@hotmail.com>
Date: Sun, 13 Aug 2023 14:31:04 +0500
Subject: [PATCH] Basic msg chunking and writing

---
 rtmp/chunk2.go | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 rtmp/chunk2.go

diff --git a/rtmp/chunk2.go b/rtmp/chunk2.go
new file mode 100644
index 0000000..99b2b14
--- /dev/null
+++ b/rtmp/chunk2.go
@@ -0,0 +1,74 @@
+package rtmp
+
+import (
+	"net"
+	"encoding/binary"
+	"time"
+)
+
+func write_basic_header(chunk_buffer *[]byte, format uint8, csid uint32) {
+	if csid < 64 {
+		(*chunk_buffer)[0] = (format << 6) + uint8(csid)
+	} else if csid < 320 {
+		(*chunk_buffer)[0] = format << 6
+		(*chunk_buffer)[1] = uint8(csid - 64)
+	} else {
+		(*chunk_buffer)[0] = (format << 6) + 1
+		binary.LittleEndian.PutUint16((*chunk_buffer)[1:3], uint16(csid - 64))
+	}
+}
+
+func write_message_header_0(chunk_buffer *[]byte, msg_strmid uint32, msg_ptr *Message, basic_header_size uint32) {
+	msg_len_inter := make([]byte, 4)
+	binary.BigEndian.PutUint32(msg_len_inter, msg_ptr.msg_len)
+	copy((*chunk_buffer)[basic_header_size + 3:basic_header_size + 6],  msg_len_inter[1:])
+	(*chunk_buffer)[basic_header_size + 6] = msg_ptr.msg_type
+	binary.BigEndian.PutUint32((*chunk_buffer)[basic_header_size + 7:basic_header_size + 11], msg_strmid)
+}
+
+func write_chunk_data(chunk_buffer *[]byte, data []byte, bytes_buffered *uint32, chunk_data_size uint32, header_size uint32) {
+	copy((*chunk_buffer)[header_size:header_size+chunk_data_size], data[*bytes_buffered:*bytes_buffered + chunk_data_size])
+	*bytes_buffered += chunk_data_size
+}
+
+func WriteChunk(conn net.Conn, csid uint32, msg_strmid uint32, msg_ptr *Message, chunk_size uint32) (error) {
+	conn.SetDeadline(time.Now().Add(10 * time.Second))
+
+	var i uint32 = 0
+	for i < msg_ptr.msg_len {
+		var chunk_data_size uint32
+		if msg_ptr.msg_len - i > chunk_size {
+			chunk_data_size = chunk_size
+		} else {
+			chunk_data_size = msg_ptr.msg_len - i
+		}
+
+		basic_header_size := uint32(1)
+		if csid >= 64 {
+			basic_header_size += 1
+		}
+		if csid >= 320 {
+			basic_header_size += 1
+		}
+
+		var chunk_buffer []byte
+		var header_size uint32
+		if i == 0 {
+			chunk_buffer = make([]byte, basic_header_size + 11 + chunk_data_size)
+			write_basic_header(&chunk_buffer, 0, csid)
+			write_message_header_0(&chunk_buffer, msg_strmid, msg_ptr, basic_header_size)
+			header_size = basic_header_size + 11
+		} else {
+			chunk_buffer = make([]byte, basic_header_size + chunk_data_size)
+			write_basic_header(&chunk_buffer, 3, csid)
+			header_size = basic_header_size
+		}
+		write_chunk_data(&chunk_buffer, msg_ptr.data, &i, chunk_data_size, header_size)
+		if _, err := conn.Write(chunk_buffer); err != nil {
+			return err
+		}
+	}
+	conn.SetDeadline(time.Time{})
+
+	return nil
+}