Before going to understand unsafe package in GoLang, the first thing needs to talk about is the pointer in GoLang. If you have a background of C language, you must know what pointer means and its usage. With pointer, you are free to operate any data at memory level which means you have great power, but this means that you have great responsibility as well. That's why it might be considered unsafe in lots of cases.Take a look at a simple example of doubling an integer.package mainimport "fmt"func double(x int) { x += x}func main() { var a = 3 double(a) fmt.Println(a) // 3}The above ...

GoLang provides two major ways to loop through elements of array, slice and map. They are for and for range. Many people find that for range is very convenient when don't care about the index of the element. In this post, some tricks and tips would be talked about regarding for range.1. Loop and get pointer of each elementAssume there is a code snippet like below which is to get the pointer of each element in an array and create a new array with the corresponding pointer.arr := [2]int{1, 2}res := []*int{}for _, v := range arr { res = append(res, &v)}//expect: 1 2fmt.Println(*res[0],*res...

In a GoLang web server, every request coming in will be handled by a goroutine. In the request handler, the logic may also need to create new goroutine to handle other tasks like RPC call. When the request is processed and response is returned, these goroutines created need to be exited so that no goroutine leak should happen.package mainimport ( "fmt" "log" "net/http")func main() { http.HandleFunc("/echo", func(w http.ResponseWriter, r *http.Request) { fmt.Println(&r) w.Write([]byte("hello")) }) log.Fatal(http.ListenAndServe(":8080", nil))}go run main.go0xc0000060100xc0000760480xc000076...

Normally the executable file built with go is a bit large, it is always desired that a smaller executable file should be generated though. In this post, a couple of ways to reduce the size of the executable will be introduced. The end effect is that the executable file size would be much less than the normal generated one.The file which is built normally has below size.Mode LastWriteTime Length Name---- ------------- ------ -----a---- 12/14/2019 9:47 AM 1974272 main-ori.exeAdd build flags Two ld parameters can be added when usin...

In a development environment, there might be multiple projects going on at the same time and they may require different development environments with different versions of build tool. In many programming languages, it is possible to have multiple versions of different build tool or development tool on a single environment. For example, there can be multiple JDKs, multiple versions of Ruby using RVM. For GoLang, there is a similar tool called GVM which can also be used to maintain multiple versions of Go in one single environment.In this post, we provide a mini guide on how to setup multiple ve...

In almost all mainstream programming languages, there is either built-in or third-party library to support parse JSON data because it is so popular for organizing and transferring data among different services. In GoLang, the built in json package also provides functions for marshalling and unmarshalling JSON data. Marshalling GoLang struct to a JSON string is relatively simple, just need to call json.Marshal(), it's a bit complicated to unmarshal an arbitrary JSON string into a GoLang struct object though. This post will try to walk through some scenarios of unmarshalling JSON string to GoLan...

By default, GoLang doesn't provide the ECB mode cipher for DESede though there is CBC mode provided. In cases we need to encrypt/decrypt data with ECB mode, we need to implement those by ourselves. This mode is frequently used when encrypting/decrypting PIN block which is small block data less than 16 bytes.In this post, we will introduce how to implement the DESede/ECB/NoPadding algorithm in GoLang by using the existing cipher support. Here we will not cover how DESede works in detail, instead we will just cover the logic to make it work.Below is the sample code which can be used to encrypt/d...

There are 3 components of slice:a) Pointer: Points to the start position of slice in the underlying array;b) length (type is int): the number of the valid elements of the slice;b) capacity (type is int): the total number of slots of the slice.Check the following code:package mainimport ( "fmt" "unsafe")func main() { var s1 []int fmt.Println(unsafe.Sizeof(s1))}The result is 24 on my 64-bit system (The pointer and int both occupy 8 bytes).In the next example, I will use gdb to poke the internals of slice. The code is like this:package mainimport "fmt"func main() { s1 := make([]int, 3, 5) ...