public DelimiterBasedFrameDecoder(int maxFrameLength, ByteBuf... delimiters) {this(maxFrameLength, true, delimiters);
}

protected final void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {Object decoded = decode(ctx, in);if (decoded != null) {out.add(decoded);}
}

protected Object decode(ChannelHandlerContext ctx, ByteBuf buffer) throws Exception {//行处理器(1)if (lineBasedDecoder != null) { return lineBasedDecoder.decode(ctx, buffer);}int minFrameLength = Integer.MAX_VALUE;ByteBuf minDelim = null; //找到最小长度的分隔符(2)for (ByteBuf delim: delimiters) {//每个分隔符分隔的数据包长度int frameLength = indexOf(buffer, delim);if (frameLength >= 0 && frameLength < minFrameLength) {minFrameLength = frameLength;minDelim = delim;}}//解码(3)//已经找到分隔符if (minDelim != null) {int minDelimLength = minDelim.capacity();ByteBuf frame;//当前分隔符否处于丢弃模式if (discardingTooLongFrame) { //首先设置为非丢弃模式discardingTooLongFrame = false;//丢弃buffer.skipBytes(minFrameLength + minDelimLength);int tooLongFrameLength = this.tooLongFrameLength;this.tooLongFrameLength = 0;if (!failFast) {fail(tooLongFrameLength);}return null;}//处于非丢弃模式//当前找到的数据包, 大于允许的数据包if (minFrameLength > maxFrameLength) {//当前数据包+最小分隔符长度 全部丢弃buffer.skipBytes(minFrameLength + minDelimLength);//传递异常事件
            fail(minFrameLength);return null;}//如果是正常的长度//解析出来的数据包是否忽略分隔符if (stripDelimiter) {//如果不包含分隔符//截取frame = buffer.readRetainedSlice(minFrameLength);//跳过分隔符
            buffer.skipBytes(minDelimLength);} else {//截取包含分隔符的长度frame = buffer.readRetainedSlice(minFrameLength + minDelimLength);}return frame;} else {//如果没有找到分隔符//非丢弃模式if (!discardingTooLongFrame) {//可读字节大于允许的解析出来的长度if (buffer.readableBytes() > maxFrameLength) {//将这个长度记录下tooLongFrameLength = buffer.readableBytes();//跳过这段长度
                buffer.skipBytes(buffer.readableBytes());//标记当前处于丢弃状态discardingTooLongFrame = true;if (failFast) {fail(tooLongFrameLength);}}} else {tooLongFrameLength += buffer.readableBytes();buffer.skipBytes(buffer.readableBytes());}return null;}
}

if (lineBasedDecoder != null) { return lineBasedDecoder.decode(ctx, buffer);
}

public DelimiterBasedFrameDecoder(int maxFrameLength, boolean stripDelimiter, boolean failFast, ByteBuf... delimiters) {//代码省略//如果是基于行的分隔if (isLineBased(delimiters) && !isSubclass()) {//初始化行处理器lineBasedDecoder = new LineBasedFrameDecoder(maxFrameLength, stripDelimiter, failFast);this.delimiters = null;} else {//代码省略
    }//代码省略
}

private static boolean isLineBased(final ByteBuf[] delimiters) {//分隔符长度不为2if (delimiters.length != 2) {return false;}//拿到第一个分隔符ByteBuf a = delimiters[0];//拿到第二个分隔符ByteBuf b = delimiters[1];if (a.capacity() < b.capacity()) {a = delimiters[1];b = delimiters[0];}//确保a是/r/n分隔符, 确保b是/n分隔符return a.capacity() == 2 && b.capacity() == 1&& a.getByte(0) == '\r' && a.getByte(1) == '\n'&& b.getByte(0) == '\n';
}

for (ByteBuf delim: delimiters) {//每个分隔符分隔的数据包长度int frameLength = indexOf(buffer, delim);if (frameLength >= 0 && frameLength < minFrameLength) {minFrameLength = frameLength;minDelim = delim;}
}

int minDelimLength = minDelim.capacity();
ByteBuf frame;
if (discardingTooLongFrame) { discardingTooLongFrame = false; buffer.skipBytes(minFrameLength + minDelimLength); int tooLongFrameLength = this.tooLongFrameLength;this.tooLongFrameLength = 0;if (!failFast) {fail(tooLongFrameLength);}return null;
}
if (minFrameLength > maxFrameLength) { buffer.skipBytes(minFrameLength + minDelimLength); fail(minFrameLength);return null;
}
if (stripDelimiter) { frame = buffer.readRetainedSlice(minFrameLength); buffer.skipBytes(minDelimLength);
} else { frame = buffer.readRetainedSlice(minFrameLength + minDelimLength);
}
return frame;

if (!discardingTooLongFrame) { if (buffer.readableBytes() > maxFrameLength) { tooLongFrameLength = buffer.readableBytes();buffer.skipBytes(buffer.readableBytes());discardingTooLongFrame = true;if (failFast) {fail(tooLongFrameLength);}}
} else {tooLongFrameLength += buffer.readableBytes();buffer.skipBytes(buffer.readableBytes());
}
return null;