• Type-Length-Value编码

    Within data communication protocols, optional information may be encoded as a type-length-value or TLV element inside a protocol. TLV is also known as tag-length value.

    The type and length are fixed in size (typically 1-4 bytes), and the value field is of variable size. 一条经TLV编码的消息,有三部分组成:Type,Length,Value。其中,Type是指消息的类型,供解析时识别;Length是指消息的长度,通常以Byte计;Value是真正的消息体,因为已经通过Length携带了消息体的具体长度,所以,这里的消息体长度是可变的。另外,Type和Length所占的Byte位数通常是固定的,通常用1-4个字符。

    These fields are used as follows:

    - Type: A binary code, often simply alphanumeric, which indicates the kind of field that this part of the message represents;

    - Length: The size of the value field (typically in bytes);

    - Value: Variable-sized series of bytes which contains data for this part of the message.

    Some advantages of using a TLV representation:

    - TLV sequences are easily searched using generalized parsing functions;

    - New message elements which are received at an older node can be safely skipped and the rest of the message can be parsed.

    - This is similar to the way that unknown XML tags can be safely skipped;

    - TLV elements can be placed in any order inside the message body;

    - TLV elements are typically used in a binary format which makes parsing faster and the data smaller;

    - It is easier to generate XML from TLV to make human inspection of the data possible.

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  • 原文地址:https://www.cnblogs.com/pied/p/3844039.html
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