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App Inventor 2 蓝牙发送十六进制字节方案：文本转Hex字节详解 - App应用开...
问题描述用户在文本框输入"ABCD"，想通过蓝牙发送 0xAB 0xCD 两个字节，而不是四个ASCII字符（0x41 0x42 0x43 0x44）。
每两个字符代表一个十六进制字节，需要将字符对解析为实际的字节值。
问题本质输入期望发送实际发送...
Difference between std::system_clock and std::steady_clock?
...eryPerformanceCounter(&counter);
return time_point(duration(static_cast<rep>((double)counter.QuadPart / frequency.QuadPart *
period::den / period::num)));
}
private:
static bool is_inited; ...
App Inventor 2 BLE扩展源码分析 - WriteBytes vs WriteStrings 23字节硬编...
一、问题背景
用户反馈：WriteBytes 发送字符串硬件能收到，WriteStrings 发送却收不到。
同样的字符串数据，通过 WriteBytes 方法发送时硬件正常接收，但通过 WriteStrings 方法发送时硬件收不到或收到截断数据。
源码仓库: mit-c...
Weak and strong property setter attributes in Objective-C
...s the parent so neither is ever released).
The 'toll free bridging' part (casting from NS to CF) is a little tricky. You still have to manually manage CFRelease() and CFRetain() for CF objects. When you convert them back to NS objects you have to tell the compiler about the retain count so it kno...
Wi-Fi 是什么的缩写 - 程序人生、谈天论地 - 清泛IT论坛，有思想、有深度
请对照上图自测。如果你是 Level 0，阅读本文前建议先搜索并查看相关资料学习 Wi-Fi 的基本概念，本文将不涉及定义或技术上的解释。Wi-Fi 是 Wireless Fidelity 吗一天和客户闲聊，我随口问了一句，Wi-Fi 是什么的缩写？客户是个美...
Creating an index on a table variable
...lly works:
declare @cmd varchar(500)='CREATE NONCLUSTERED INDEX [ix_temp'+cast(newid() as varchar(40))+'] ON #temp (NonUniqueIndexNeeded);';
exec (@cmd);
This insures the name is always unique even between simultaneous executions of the same procedure.
...
Is unsigned integer subtraction defined behavior?
...ake sure that the result is signed, then stored it into signed variable or cast it to signed. When you want to get the difference between numbers and make sure that the modular arithmetic will not be applied, then you should consider using abs() function defined in stdlib.h:
int c = five - seven; ...
一分钟读懂低功耗蓝牙(BLE) MTU交换数据包 - 创客硬件开发 - 清泛IT社区，...
1.概述
* MTU: 最大传输单元（MAXIMUM TRANSMISSION UNIT） ， 指在一个PDU （Protocol Data Unit： 协议数据单元，在一个传输单元中的有效传输数据）能够传输的最大数据量（多少字节可以一次性传输到对方）。
* MTU 交...
Does const mean thread-safe in C++11?
...thread-safe since no writes are possible (and if you are considering const_cast-ing something originally declared const then you get undefined-behavior and that's it).
So what does it mean then?
Let's assume --for the sake of argument-- that multiplication operations are extremely costly and we be...
C++11 rvalues and move semantics confusion (return statement)
...emporary created on the return line. move doesn't create a temporary. It casts an lvalue to an xvalue, making no copies, creating nothing, destroying nothing. That example is the exact same situation as if you returned by lvalue-reference and removed the move from the return line: Either way you...