update sproto (#1720)

Co-authored-by: zixun <lb151450@alibaba-inc.com>

lualib-src/sproto/README.md

@@ -104,7 +104,7 @@ local sprotocore = require "sproto.core" -- optional
 * `sproto.new(spbin)` creates a sproto object by a schema binary string (generates by parser).
 * `sprotocore.newproto(spbin)` creates a sproto c object by a schema binary string (generates by parser).
 * `sproto.sharenew(spbin)` share a sproto object from a sproto c object (generates by sprotocore.newproto).
-* `sproto.parse(schema)` creares a sproto object by a schema text string (by calling parser.parse)
+* `sproto.parse(schema)` creates a sproto object by a schema text string (by calling parser.parse)
 * `sproto:exist_type(typename)` detect whether a type exist in sproto object.
 * `sproto:encode(typename, luatable)` encodes a lua table with typename into a binary string.
 * `sproto:decode(typename, blob [,sz])` decodes a binary string generated by sproto.encode with typename. If blob is a lightuserdata (C ptr), sz (integer) is needed.
@@ -217,7 +217,7 @@ Types
 * **string** : string
 * **binary** : binary string (it's a sub type of string)
 * **integer** : integer, the max length of an integer is signed 64bit. It can be a fixed-point number with specified precision.
-* **double** : double, floating-point number.
+* **double** : double precision floating-point number, satisfy [the IEEE 754 standard](https://en.wikipedia.org/wiki/Double-precision_floating-point_format).
 * **boolean** : true or false
 
 You can add * before the typename to declare an array.
@@ -230,7 +230,7 @@ User defined type can be any name in alphanumeric characters except the build-in
 
 * Where are double or real types?
 
-I have been using Google protocol buffers for many years in many projects, and I found the real types were seldom used. If you really need it, you can use string to serialize the double numbers. When you need decimal, you can specify the fixed-point presision.
+I have been using Google protocol buffers for many years in many projects, and I found the real types were seldom used. If you really need it, you can use string to serialize the double numbers. When you need decimal, you can specify the fixed-point precision.
 
 **NOTE** : `double` is supported now.
 
@@ -263,6 +263,7 @@ For integer array, an additional byte (4 or 8) to indicate the value is 32bit or
 Read the examples below to see more details.
 
 Notice: If the tag is not declared in schema, the decoder will simply ignore the field for protocol version compatibility.
+Notice more: all examples are tested in `test_wire_protocol.lua`, update `test_wire_protocol.lua` when update examples.
 
 ```
 .Person {
@@ -277,6 +278,9 @@ Notice: If the tag is not declared in schema, the decoder will simply ignore the
 	bools 1 : *boolean
 	number 2 : integer
 	bignumber 3 : integer
+ 	double 4 : double
+ 	doubles 5 : *double
+ 	fpn 6 : integer(2)
 }
 ```
 
@@ -405,6 +409,39 @@ A0 86 01 00 (100000, 32bit integer)
 00 1C F4 AB FD FF FF FF (-10000000000, 64bit integer)
 ```
 
+Example 7:
+```
+data {
+    double = 0.01171875,
+    doubles = {0.01171875, 23, 4}
+}
+
+03 00 (fn = 3)
+07 00 (skip id = 3)
+00 00 (id = 4, value in data part)
+00 00 (id = 5, value in data part)
+
+08 00 00 00 (sizeof number, data part)
+00 00 00 00 00 00 88 3f (0.01171875, 64bit double)
+
+19 00 00 00 (sizeof doubles)
+08 (sizeof double)
+00 00 00 00 00 00 88 3f (0.01171875, 64bit double)
+00 00 00 00 00 00 37 40 (23, 64bit double)
+00 00 00 00 00 00 10 40 (4, 64bit double)
+```
+
+Example 8:
+```
+data {
+    fpn = 1.82,
+}
+
+02 00 (fn = 2)
+0b 00 (skip id = 5)
+6e 01 (id = 6, value = 0x16e/2 - 1 = 182)
+```
+
 0 Packing
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