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最新推荐文章于 2024-08-14 17:49:20 发布

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本文深入探讨了复合数据的封装原理，包括长度、计数器及其在不同类型的封装中的应用，如列表、映射和数组。文章详细介绍了各种类型的编码规则、描述和实例，旨在为读者提供全面的技术指南。

1.2.3 复合数据

复合数据的封装是由一个长度值和计数器值，以及紧跟计数器值后封装的数据组成的。复合数据中长度值和计数器值对应占用的空间宽度可以通过格式码的类型来计算出来。

+----------= count items =---------+
| |
n OCTETs n OCTETs | |
+-------------+---------------+--------------+------------+-----------+
| size | count | ... / | item | \ ... |
+-------------+---------------+------------/ +-------------+ \--------+
/ / \ \
/ / \ \
/ / \ \
+---------------+----------+
| constructor | data |
+----------------+----------+

Subcategory n
=================
0xC 1
0xD 4

Type: list
<type name="list" class="primitive"/>
Encoding Code Category Description
list0 0x45 fixed-width, 0 byte value the empty list (i.e. the list with no elements)
list8 0xc0 variable-width, 1 byte size up to 2^8 - 1 list elements with total size less
than 2^8octets
list32 0xd0 variable-width, 4 byte size up to 2^32 - 1 list elements with total size less
than 2^32octets

Type: map
<type name="map" class="primitive"/>

映射数据是按照复合数据封装的，元素是由不同的键-值对组成的。
item 0 item 1 item n-1 item n
+-------+-------+----+---------+---------+
| key 1 | val 1 | .. | key n/2 | val n/2 |
+-------+-------+----+---------+---------+

映射数据包含着一些列选项（等于键-值对的数目和）。在映射数据中，存在两个相同的键索引是不合法的。除非另有原因，否则映射数据必须考虑成有序的，键-值对的有序在语义上是比较重要的，如果两个映射中仅仅是键-值对在顺序上有所不同，那么这两个键-值对封装在映射中的时候是不一样的。
Encoding Code Category Description
map8 0xc1 variable-width, 1 byte size up to 2^8 - 1 octets of encoded map data
map32 0xd1 variable-width, 4 byte size up to 2^32 - 1 octets of encoded map data

1.2.4 数组

All array encodings consist of a size followed by a count followed by an element constructor followed
by count elements of encoded data formated as required by the element constructor:

Type: array

<type name="array" class="primitive"/>
Encoding Code Category Description
array8 0xe0 variable-width, 1 byte size up to 2^8 - 1 array elements with total size less
than 2^8 octets
array32 0xf0 variable-width, 4 byte size up to 2^32 - 1 array elements with total size less
than 2^32 octets

1.2.5 封装类型的列表

Type Encoding Code Category Description
null 0x40 fixed/0 the null value
boolean 0x56 fixed/1 boolean with the octet 0x00 being false and
octet 0x01 being true
boolean true 0x41 fixed/0 the boolean value true
boolean false 0x42 fixed/0 the boolean value false
ubyte 0x50 fixed/1 8-bit unsigned integer
ushort 0x60 fixed/2 16-bit unsigned integer in network byte order
uint 0x70 fixed/4 32-bit unsigned integer in network byte order
uint smalluint 0x52 fixed/1 unsigned integer value in the range 0 to 255 inclusive
uint uint0 0x43 fixed/0 the uint value 0
ulong 0x80 fixed/8 64-bit unsigned integer in network byte order
ulong smallulong 0x53 fixed/1 unsigned long value in the range 0 to 255 inclusive
ulong ulong0 0x44 fixed/0 the ulong value 0
byte 0x51 fixed/1 8-bit two's-complement integer
short 0x61 fixed/2 16-bit two's-complement integer in network byte order
int 0x71 fixed/4 32-bit two's-complement integer in network byte order
int smallint 0x54 fixed/1 signed integer value in the range -128 to 127 inclusive
long 0x81 fixed/8 64-bit two's-complement integer in network byte order
long smalllong 0x55 fixed/1 signed long value in the range -128 to 127 inclusive
float ieee-754 0x72 fixed/4 IEEE 754-2008 binary32
double ieee-754 0x82 fixed/8 IEEE 754-2008 binary64
decimal32 ieee-754 0x74 fixed/4 IEEE 754-2008 decimal32 using the Binary Integer

Decimal encoding
decimal64 ieee-754 0x84 fixed/8 IEEE 754-2008 decimal64 using the Binary Integer

Decimal encoding
decimal128 ieee-754 0x94 fixed/16 IEEE 754-2008 decimal128 using the Binary
Integer Decimal encoding
char utf32 0x73 fixed/4 a UTF-32BE encoded unicode character
timestamp ms64 0x83 fixed/8 64-bit signed integer representing milliseconds
since the unix epoch
uuid 0x98 fixed/16 UUID as de ned in section 4.1.2 of RFC-4122
binary vbin8 0xa0 variable/1 up to 2^8 - 1 octets of binary data
binary vbin32 0xb0 variable/4 up to 2^32 - 1 octets of binary data
string str8-utf8 0xa1 variable/1 up to 2^8 - 1 octets worth of UTF-8 unicode
(with no byte order mark)
string str32-utf8 0xb1 variable/4 up to 2^32 - 1 octets worth of UTF-8 unicode
(with no byte order mark)
symbol sym8 0xa3 variable/1 up to 2^8 - 1 seven bit ASCII characters

representing a symbolic value
symbol sym32 0xb3 variable/4 up to 2^32 - 1 seven bit ASCII characters

representing a symbolic value
list list0 0x45 fixed/0 the empty list (i.e. the list with no elements)
list list8 0xc0 compound/1 up to 2^8 - 1 list elements with total size less
than 2^8 octets
list list32 0xd0 compound/4 up to 2^32 - 1 list elements with total size less
than 2^32 octets
map map8 0xc1 compound/1 up to 2^8 - 1 octets of encoded map data
map map32 0xd1 compound/4 up to 2^32 - 1 octets of encoded map data
array array8 0xe0 array/1 up to 2^8 - 1 array elements with total size less
than 2^8 octets
array array32 0xf0 array/4 up to 2^32 - 1 array elements with total size less
than 2^32 octets