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  Why accessing Java HashMap may cause infinite loop in concurrent environment

HashMap in Java is frequently used to handle key/value pairs. But it is not a good candidate to be used in concurrent environment where ConcurrentHashMap should be used instead. If used in concurrent environment, it may cause lots of unexpected behavior even including make the program getting into an infinite loop situation. To understand how this can happen, let's first discuss how HaspMap works internally. In this post we will use implementation of HashMap before Java 8 as example, Java 8 prov...

   JAVA,HASHMAP,INFINITE LOOP     2020-03-29 01:47:00

  Understand GoLang WaitGroup internals and how it works

Background Before getting into the main content, let me give a brief introduction to WaitGroup and its related background knowledge. Here, the focus is on the basic usage of WaitGroup and the fundamental knowledge of system semaphores. For those who are familiar with these, you can skip this section directly. WaitGroup WaitGroup is one of the most common concurrency control techniques in Golang, and its function can be roughly compared to the join() in concurrency control of other languages' mul...

   GOLANG,WAITGROUP,SOURCE CODE     2023-04-26 08:02:01

  Different types of keystore in Java -- PKCS12

PKCS12 is an active file format for storing cryptography objects as a single file. It can be used to store secret key, private key and certificate.It is a standardized format published by RSA Laboratories which means it can be used not only in Java but also in other libraries in C, C++ or C# etc. This file format is frequently used to import and export entries from or to other keystore types. Next we will explain the operations which can be performed on PKCS12 keystore. Create PKCS12 keystore Be...

   Java, PKCS12, keystore, tutorial     2015-01-04 21:08:49

  Do you really understand C? 21st International Obfuscated C Code Contest winning entries

The 21st International Obfuscated C Code Contest(IOCCC) officially launched the winning source code. IOCCC requires contestants to write the most creative and the most obfuscated C codes with the size limited to 4kb and less Work of each participant is impressive. The winners, including one French, one Korean, five Americans, one Belgian, one Israeli, one British, four Japanese and one Chinese. Here we list some codes: Best short program Seonghoon Kang  from Korea- Decodes spelled out ...

   C,Obsfucation contest     2012-10-25 12:26:55

  The evolving history of asynchronous operation in JavaScript

JavaScript is single threaded, it means there would be only one task running at any point of time. But this would slow down the overall program execution if there is long running task, hence asynchronous task execution is desired in complex cases. To achieve asynchronous task execution, there are a few options introduced in JavaScript. setTimeout/setInterval Event Promise Async/Await setTimeout/setInterval is one of the first mechanisms introduced in JavaScript to simulate asynchronous operati...

   JAVASCRIPT,ASYNC,PROMISE,AWAIT     2019-11-09 08:21:56

  A trick of building multithreaded application on Solaris

Firstly, Let’s see a simple multithreaded application: #include <stdio.h> #include <pthread.h> #include <errno.h> void *thread1_func(void *p_arg) { errno = 0; sleep(3); errno = 1; printf("%s exit, errno is %d\n", (char*)p_arg, errno); } void *thread2_func(void *p_arg) { errno = 0; sleep(5); printf("%s exit, errno is %d\n", (char*)p_arg, errno); } int main(void) { pthread_t t1, t2; ...

   C, Solaris     2014-10-14 02:59:40

  Go channel explained

In Go, a channel is a type of concurrent data structure that allows two or more goroutines (Go's term for lightweight threads) to communicate with each other. Channels provide a way for goroutines to send and receive values, and they are an essential part of Go's concurrency model. Here's a simple example that demonstrates how to use channels in Go: package main import ( "fmt" ) func main() { // Create a new channel with the `make` function ch := make(chan int) // Start a new ...

   GOLANG,CHANNEL     2022-12-10 22:24:26

  A simple tutorial on GoLang connecting to Clickhouse

Go, also known as Golang, is a statically-typed, concurrent programming language created by Google. ClickHouse is a high-performance, column-oriented database management system that can be used for real-time data analysis. This tutorial will provide a deep dive into how to connect to ClickHouse from a Go program, including how to perform common database operations such as SELECT and INSERT statements. Before proceeding, it is assumed that you already have Go and ClickHouse installed on your mach...

   GOLANG,CLICKHOUSE,TUTORIAL     2023-02-11 07:05:36

  Fix for-range Issue Again in Go 1.22

With the release of Go 1.22, the Go team addressed a long-standing issue with the for-range loop variable scoping, which had been a common pitfall for developers writing concurrent code. Specifically, the problem was that the loop variable in a for-range loop was reused across iterations, leading to unexpected behavior when closures were involved. The Issue Before Go 1.22 Consider the following example: package forange import "fmt" func Do() { done := make(chan bool) values := []string...

   GO,GO 1.22,FOR RANGE,BUG,GO.MOD     2024-11-21 01:03:04

  Some measures for improving Linux server security

The hackers often exploit server weakness to gain access control to some servers. With a scanner, aimlessly looking undefended host, backdoor, control, and sold to people in need. Some basic security measures can be taken on Linux servers to avoid being attacked by hackers. Disable root remote login As the default administrative account, root is the account which is most likely to be attacked.Disabling ssh remote login is necessary. Method: Edit / etc / ssh / sshd_config PermitRootLogin no At t...

   Linux server,Server security     2012-08-21 05:08:50

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