JT1078/src/JT1078.Hls/TS_PAT_Package.cs

using JT1078.Hls.Formatters;
using JT1078.Hls.MessagePack;
using System;
using System.Collections.Generic;
using System.Text;

namespace JT1078.Hls
{
    /// <summary>
    /// 格式节目关联表
    /// </summary>
    public class TS_PAT_Package : ITSMessagePackFormatter
    {
        /// <summary>
        /// PAT表固定为0x00
        /// 8bit
        /// </summary>
        public byte TableId { get; set; } = 0x00;
        /// <summary>
        /// 固定为二进制1
        /// 1bit
        /// </summary>
        internal byte SectionSyntaxIndicator { get; set; } = 0x01;
        /// <summary>
        /// 固定为二进制0
        /// 1bit
        /// </summary>
        internal byte Zero { get; set; } = 0x00;
        /// <summary>
        /// 固定为二进制3
        /// 2bit
        /// </summary>
        internal byte Reserved1 { get; set; } = 0x03;
        /// <summary>
        /// 后面数据的长度
        /// 12bit
        /// </summary>
        public ushort SectionLength { get; set; }
        /// <summary>
        /// 传输流ID
        /// 16bit
        /// </summary>
        internal ushort TransportStreamId { get; set; } = 0x0001;
        /// <summary>
        /// 固定为二进制3
        /// 2bit
        /// </summary>
        internal byte Reserved2 { get; set; } = 0x03;
        /// <summary>
        /// 版本号，固定为二进制00000，如果PAT有变化则版本号加1
        /// 5bit
        /// </summary>
        public byte VersionNumber { get; set; } = 0x00;
        /// <summary>
        /// 固定为二进制1，表示这个PAT表可以用，如果为0则要等待下一个PAT表
        /// 1bit
        /// </summary>
        public byte CurrentNextIndicator { get; set; } = 1;
        /// <summary>
        /// 固定为0x00
        /// bit8
        /// </summary>
        internal byte SectionNumber { get; set; } = 0x00;
        /// <summary>
        /// 固定为0x00
        /// bit8
        /// </summary>
        internal byte LastSectionNumber { get; set; } = 0x00;

        public List<TS_PAT_Program> Programs { get; set; }

        /// <summary>
        /// 前面数据的CRC32校验码
        /// </summary>
        public uint CRC32 { get; set; }

        public void ToBuffer(ref TSMessagePackWriter writer)
        {
            writer.WriteByte(TableId);
            //SectionSyntaxIndicator   Zero  Reserved1   SectionLength
            //1 0 11 0000 0000 0000
            //(ushort)(1011_0000_0000_0000 | SectionLength)
            // todo:
            //writer.WriteUInt16((ushort)(1011_0000_0000_0000 | SectionLength));
            writer.Skip(2, out int SectionLengthPosition);
            writer.WriteUInt16(TransportStreamId);
            //Reserved2 VersionNumber CurrentNextIndicator
            //11 00000 1
            var a = Reserved2 & 0xC0;
            var b = VersionNumber & 0x3E;
            var c = (byte)(a | b | CurrentNextIndicator);
            writer.WriteByte(c);
            writer.WriteByte(SectionNumber);
            writer.WriteByte(LastSectionNumber);
            if (Programs != null)
            {
                foreach (var program in Programs)
                {
                    program.ToBuffer(ref writer);
                }
            }
            writer.WriteUInt16Return((ushort)(1011_0000_0000_0000 | (ushort)(writer.GetCurrentPosition() - SectionLengthPosition - 2)), SectionLengthPosition);
            writer.WriteCRC32(SectionLengthPosition);
        }
    }
}