dart+stack overflow

content/post/go-dart-plugin.md

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++++
+title = "Go Dart Plugin"
+date = 2022-11-06T18:35:52-05:00
+lastmod = 2022-11-06T18:35:52-05:00
+tags = ["Dart","golang"]
+categories = ["Coding","Dart"]
+imgs = []
+cover = ""  # image show on top
+readingTime = true  # show reading time after article date
+toc = true
+comments = false
+justify = false  # text-align: justify;
+single = false  # display as a single page, hide navigation on bottom, like as about page.
+license = ""  # CC License
+draft = false
++++
+
+
+**Part One** the GO side:
+1. We need to make the function exportable, so the name should be capitalized and become `GetKey()` 
+2. We need to use `cgo` so that we can create shared library, `cgo` means we need to:
+<!--more-->
+2.1. Use `import "C"`
+
+2.2. Use comment with the function as `//export GetKey`
+
+2.3. Use `C.type` interface, in this example to instead of `string` use `C.char` and `C.CString` and as working with pointer is the preferable way, use `*C.char`
+
+So, the `Go` function in the question, should be re-written as:
+```go
+// filename: lib.go
+package main
+
+import "C"
+
+//export GetKey
+func GetKey() *C.char {
+	theKey := "123-456-789"
+	return C.CString(theKey)
+}
+
+func main() {}  
+``` 
+
+3. Compile the above and create the shared library as:
+```bash
+go build -buildmode=c-shared -o lib.a lib.go
+```
+
+**Part Two** the Dart side:
+
+1. Create the `pubspec.yaml` and add to its dependencies the `ffi: ^0.1.3`, so it be as:
+```yaml
+name: dart_app
+description: A new Dart application.
+
+# The following line prevents the package from being accidentally published to
+# pub.dev using `pub publish`. This is preferred for private packages.
+publish_to: 'none' # Remove this line if you wish to publish to pub.dev
+version: 1.0.0+1
+
+environment:
+  sdk: ">=2.7.0 <3.0.0"
+
+dependencies:
+  ffi: ^0.1.3
+```
+2. Copy the generated files from GO which are `lib.a` and `lib.h` to the dart projetc folder
+3. Create dart file to handle the FFI, where you need to:
+3.1. Import the `ffi` and the `utf8`
+
+3.2. Define the FFI funtion signature as `typedef get_key_func = ffi.Pointer<Utf8> Function();`
+
+3.3. Define the Dart funtion signature as `typedef GetKey = ffi.Pointer<Utf8> Function();`
+
+3.4. Load the shared library as `final dylib = ffi.DynamicLibrary.open('lib.a');`
+
+3.5. Map FFI and Dart function signatures as `final GetKey getKey dylib.lookup<ffi.NativeFunction<get_key_func>>('GetKey').asFunction();`
+
+3.6. Define a function todo the execution, and inside this function do the following:
+
+3.6.1. Invoke the Dart function and assign the output to a variabe as `var addressOf = getKey();`
+
+3.6.2. Decode the result, which is the address of the pointer, and get the string from it, as: `print(addressOf.ref.toString());`
+
+So, the Dart code will become:
+```dart
+//file name fficheck.dart
+import 'dart:ffi' as ffi; // For FFI
+import 'package:ffi/ffi.dart';
+import 'package:ffi/src/utf8.dart';
+
+typedef get_key_func = ffi.Pointer<Utf8> Function(); // FFI fn signature
+typedef GetKey = ffi.Pointer<Utf8> Function(); // Dart fn signature
+final dylib = ffi.DynamicLibrary.open('lib.a');
+
+final GetKey getKey =
+    dylib.lookup<ffi.NativeFunction<get_key_func>>('GetKey').asFunction();
+
+void testffi() {
+  print("Hi from dart");
+  var addressOf = getKey();
+  print(addressOf.ref.toString());
+}
+```
+
+4. Create the main Dart file, and import the file that is handling the FFI, and call the required function, as:
+```dart
+// file name lib.dart
+import 'fficheck.dart';
+
+main() {
+  print("Hello, World!");
+  testffi();
+}
+```
+
+5. Execute the dart file as `dart main.dart`
+
+[![enter image description here][1]][1]  
+
+
+  [1]: https://i.stack.imgur.com/5UfS2.png
+
+Source : https://stackoverflow.com/questions/63747683/how-to-call-go-lib-from-dart-using-ffi/63747684#63747684 

content/post/stackoverflow-source.md

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+title = "Stackoverflow Source"
+date = 2022-11-06T18:39:54-05:00
+lastmod = 2022-11-06T18:39:54-05:00
+tags = ["Markdown"]
+categories = ["Markdown"]
+imgs = []
+cover = ""  # image show on top
+readingTime = true  # show reading time after article date
+toc = true
+comments = false
+justify = false  # text-align: justify;
+single = false  # display as a single page, hide navigation on bottom, like as about page.
+license = ""  # CC License
+draft = false
++++
+##### 1. If you have a particular StackOverflow question such as:
+<!--more-->
++ https://stackoverflow.com/questions/69419055/find-the-pseudo-version-of-the-current-main-module
+
+##### 2. When you click on the little recylcing symbol next to a question or answer "Show activity on this post", you will get to the timeline:
+
+https://stackoverflow.com/posts/69419917/timeline#history_9281a690-64c3-4302-bb36-1ebb6dfd3ecf
+
+##### 3. Take the post ID that is exposed in the timeline url as above 
+Go to Question revision history:
+
+https://sitename.stackexchange.com/posts/{post-id}/revisions
+
++ shown as the “history” link for questions and answers with at least two revisions
++ contains links to individual revisions and their source code, as well as summaries of a number of other events such as closing, reopening, (un)deleting, bounty start/end, (un)locking, tweeting, marked (not) community wiki, and merging.
+
+##### 4. So then you will have a URL like this:
+https://stackoverflow.com/posts/69419917/revisions
+
+##### 5. And then the source code looks like this:
+https://stackoverflow.com/revisions/9281a690-64c3-4302-bb36-1ebb6dfd3ecf/view-source
+
+
+
+Source : https://gist.github.com/StevenACoffman/14487c47b7b15c8889ae1c8f12a25d43