block | 易学教程

Copy a file block per block in C

阅读更多关于 Copy a file block per block in C

问题 I'm trying to divide a file into an x ammount of blocks of size y (in bytes), so that I can copy each block individually. How can I do that? 回答1: Try using fread char buffer[ysize]; fread(buffer, ysize, 1, fp); Each time you read ysize bytes in buffer from the file. 回答2: Some struct stat structures have additional members in them that prove useful when copying files: st_blksize The optimal I/O block size for the file. st_blocks The actual number of blocks allocated for the file in (check

Java 封装与类

阅读更多关于 Java 封装与类

　　一、面向对象编程　　面向对象编程三大特性：封装、继承和多态。　　类是实现封装的手段，是面向对象编程的基本单元。　　封装隐藏了类的内部实现细节，暴露给外界可控的操作，提高数据的完整性和安全性，提高模块的可重用性和开发效率，降低开发的复杂性。　　从面向对象程序设计方法的角度看，程序中所有的东西都是对象，而程序是对象的组合，对象间通过消息传递实现协作。　　二、类　　类是Java程序设计的核心概念和基本单元。　　类是对一类事物的特征的描述，是抽象后的描述；对象是一个实例。　　1、Java没有全局变量，只有：　　静态变量：隶属于类　　实例变量：类体中定义，类的属性，隶属于对象。　　局部变量：形参、方法内定义或代码块中定义，隶属于方法。　　　　2、成员修饰符——public、private、protected、default 　　作用：实现访问权限控制。　　public：被public修饰的成员，可以在任何一个类中被调用。　　private：除了本类的方法能够调用私有成员（方法、属性），其他任何类都不能直接访问私有成员。　　所有修饰符都能修饰数据成员、方法成员和构造方法；只有public和default能修饰类（外部类）。　　3、方法重载　　（1）方法名相同　　（2）方法的参数签名不相同（参数类型、个数、顺序）。　　（3）方法的返回类型可以不同

Use of variables in Django template {% block %} tags

阅读更多关于 Use of variables in Django template {% block %} tags

问题 The main question is how can I programatically choose what block to put some content in. The following is working in a different project, but in a fresh project this does not work for some reason. I'm using the same (default) template context processors on the same machine for both projects. I have a base template that goes something like this ... {% block Title %}<h1>Whoo</h1>{% endblock %} {% block Content %}<p>Hi there</p>{% endblock %} ... And an extending template like this {% extends

CSS: Why don't these two div (or span) elements float next to each other

阅读更多关于 CSS: Why don't these two div (or span) elements float next to each other

问题 In the following code, I need the div elements #ldiv and #rdiv to be placed next to each other. So I am using the CSS float property. I looked up this answer, and I think I am following it, but still the div's won't position next to each other. The second div displays in the next line. Then I thought that div is a block level element, so I replaced the div by span elements. But that did not help either. JSFiddle here. <div style="padding:25px; width:400px;"> <div style="background-color:

Authenticate GameKit local player using swift

阅读更多关于 Authenticate GameKit local player using swift

问题 Im looking to migrate a game over to swift, the only trouble I am having is with blocks/closures. It's the syntax I just don't understand, whereas in Objective C I would use: GKLocalPlayer *localPlayer = [GKLocalPlayer localPlayer]; localPlayer.authenticateHandler = ^(UIViewController *viewController, NSError *error){ if (viewController != nil) { [self presentViewController:viewController animated:YES completion:nil]; } } etc.etc. but I'm not sure how to go about doing the same in Swift. I

Interpret Variable in Powershell { } scriptblock

阅读更多关于 Interpret Variable in Powershell { } scriptblock

问题 I have a shell script which should start a .exe in the background: $strPath = get-location $block = {& $strPath"\storage\bin\storage.exe" $args} start-job -scriptblock $block -argumentlist "-f", $strPath"\storage\conf\storage.conf" In a preceding Question I found out that I need absolute Paths. However the $strPath variable isn't interpreted, if you look at the command: PS Q:\mles\etl-i_test> .\iprog.ps1 --start1 Start Storage Id Name State HasMoreData Location Command -- ---- ----- ---------

AFNetworking synchronous calls (like/unlike)

阅读更多关于 AFNetworking synchronous calls (like/unlike)

问题 I need to implement like/unlike functionality in app. All API calls are made with AFNetworking and success/errors handlers ( ios blocks ). Problem is that when user making many clicks on a button in a short period of time, some of the request are received by server in a wrong sequence and then everything becomes wrong. For example double like or double unlike happens. Is there a way to send all request via AFNetworking synchronously? If no what is the best practice to design this kind of API

R: split matrix into arbitrary number of blocks

阅读更多关于 R: split matrix into arbitrary number of blocks

问题 Say I have a matrix of values set.seed(1) A <- matrix(runif(25),ncol=5) I'd like to calculate some statistics for approximately square neighborhoods within this matrix of approximately equal size. Either of these kinds of output would do: N1 <- matrix(c(rep(c("A","A","B","B","B"),2),rep(c("C","C","D","D","D"),3)),ncol=5) N2 <- matrix(c(rep(c("A","A","A","B","B"),3),rep(c("C","C","D","D","D"),2)),ncol=5) N1 [,1] [,2] [,3] [,4] [,5] [1,] "A" "A" "C" "C" "C" [2,] "A" "A" "C" "C" "C" [3,] "B" "B"

关于HDFS应知应会的几个问题

阅读更多关于关于HDFS应知应会的几个问题

1.Namenode的安全模式？安全模式是Namenode的一种状态（Namenode主要有active/standby/safemode三种模式）。 2.哪些情况下，Namenode会进入安全模式？ a. Namenode发现集群中的block丢失率达到一定比例时（默认0.01%），Namenode就会进入安全模式，在安全模式下，客户端不能对任何数据进行操作，只能查看元数据信息 b. 在hdfs集群正常冷启动时，Namenode也会在safemode状态下维持相当长的一段时间，此时你不需要去理会，等待它自动退出安全模式即可 3.为什么，在HDFS集群冷启动时，Namenode会在安全模式下维持相当长的一段时间？ Namenode的内存元数据中，包含文件路径、副本数、blockid，及每一个block所在Datanode的信息，而fsimage中，不包含block所在的Datanode信息。那么，当Namenode冷启动时，此时内存中的元数据只能从fsimage中加载而来，从而就没有block所在的Datanode信息 ——> 就会导致Namenode认为所有的block都已经丢失 ——> 进入安全模式 ——> 所在的Datanode信息启动后，会定期向Namenode汇报自身所持有的block信息 ——> 随着Datanode陆续启动，从而陆续汇报block信息

Sphinx variable substitution in code blocks

阅读更多关于 Sphinx variable substitution in code blocks

问题 Using Sphinx 1.2.3 and given this RST snippet: .. code-block:: xml <foo> <bar>|version|</bar> </foo> and in conf.py I have: version = '1.0.2' How do you ensure that the above RST snippet renders as: <foo> <bar>1.0.2</bar> </foo> This previous question indicates that we should use .. parsed-literal:: instead of .. code-block:: , but that does not work, nor does the referenced link in that question work either. I also want to retain syntax highlighting. 回答1: You can get the wanted output by