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Best way to serialize an NSData into a hexadeximal string
...e Gallagher's answer is sufficient for a relatively small size, memory and cpu performance deteriorate for large amounts of data. I profiled this with a 2MB file on my iPhone 5. Time comparison was 0.05 vs 12 seconds. Memory footprint is negligible with this method while the other method grew the he...
导航条使用指导 · App Inventor 2 中文网
...旋转屏幕后导航条仍保留当前位置与选择。
常见问题
现象
检查
标签空白、只剩占位
调了设置全部标签（图标列表，标签文字列表）（SetItems）吗？两个列表长度要一致
...
How can I profile C++ code running on Linux?
... one of the suggested ones.
However, if you're in a hurry and you can manually interrupt your program under the debugger while it's being subjectively slow, there's a simple way to find performance problems.
Just halt it several times, and each time look at the call stack. If there is some code th...
在MongoDB中模拟Auto Increment - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...给_id就OK了，因为它的实现满足原子性，所以不存在并发问题。
另外说明一点，findAndModify本身提供了一个upsert参数，为true的话可以自动insert，但那样就不能自定义初始值了，所以文中示例没有使用upsert。
BTW，数据库“_seq”的...
调用空智能指针对象的函数，Windows及Linux行为解析 - C/C++ - 清泛网 - 专...
...-O0以上优化版本访问空智能指针对象函数会发生崩溃。
问题起因：一个智能指针对象使用IsNull()判断是否为空后，执行函数，仅在Linux开优化（-O0以上）发生崩溃，代码如下：
#include <stdio.h>
#include <memory>
#include <assert.h>
c...
Best practices for circular shift (rotate) operations in C++
...,7 which is slower and takes more bytes than rol edi,7 on some CPUs (especially AMD, but also some Intel), when BMI2 isn't available for rorx eax,edi,25 to save a MOV.
MSVC: x86-64 CL19: Only recognized for constant-count rotates. (The wikipedia idiom is recognized, but the branch and AND aren't op...
关于php的socket初探 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...程来处理的 IO 模型，但是效率相对比较差，也很容易出问题，所以暂时不做介绍了）。在这些多路复用的模式中，异步阻塞/非阻塞模式的扩展性和性能最好。
引入阻塞/非阻塞,、同步/异步比喻很形象的一段话：
有A，B，C，D...
JavaScript OOP in NodeJS: how?
...onstructor.apply( this, arguments );
}
//Pointless override to show super calls
//note that for performance (e.g. inlining the below is impossible)
//you should do
//method.$getAge = _super.getAge;
//and then use this.$getAge() instead of super()
method.getAge = function() {
return _super.getAge...
Add native files from NuGet package to project output directory
...ch simpler targets file though, using a None element, as MSBuild will copy all None files to referencing projects.
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<ItemGroup>
<NativeLibs Include="$(MSBuildThisFileDirectory)**\*.dll" />
<None Incl...
Where are my postgres *.conf files?
I have recently reinstalled postgresql 8.3 on my Ubuntu 8.04 after update. Used EnterpriseDB package. I can connect to the database locally, I see system DB postgres but I can't configure it because I can't find config files. Searched through entire hard drive and found only samples like pg_hba.con...