geraldstanje/README.md

## README.md

      
    Raw
  

              README.md
            
          
example:
https://medium.com/swlh/build-and-use-go-packages-as-c-libraries-889eb0c19838

https://medium.com/@walkert/fun-building-shared-libraries-in-go-639500a6a669
https://www.darkcoding.net/software/building-shared-libraries-in-go-part-2/
https://karthikkaranth.me/blog/calling-c-code-from-go/


more infos:
https://youtu.be/ILfPgkqdSYc?t=228
https://www.youtube.com/watch?v=RFX5-1hNJmE


cgo:
https://www.youtube.com/watch?v=lhMhApWQp2E


https://www.cockroachlabs.com/blog/the-cost-and-complexity-of-cgo/
https://golang.org/cmd/cgo/#hdr-Passing_pointers
https://blog.filippo.io/building-python-modules-with-go-1-5/

from https://golang.org/cmd/go/

Build modes
The 'go build' and 'go install' commands take a -buildmode argument which indicates which kind of object file is to be built. Currently supported values are:
-buildmode=archive
Build the listed non-main packages into .a files. Packages named
main are ignored.
-buildmode=c-archive
Build the listed main package, plus all packages it imports,
into a C archive file. The only callable symbols will be those
functions exported using a cgo //export comment. Requires
exactly one main package to be listed.
-buildmode=c-shared
Build the listed main package, plus all packages it imports,
into a C shared library. The only callable symbols will
be those functions exported using a cgo //export comment.
Requires exactly one main package to be listed.
-buildmode=default
Listed main packages are built into executables and listed
non-main packages are built into .a files (the default
behavior).
-buildmode=shared
Combine all the listed non-main packages into a single shared
library that will be used when building with the -linkshared
option. Packages named main are ignored.
-buildmode=exe
Build the listed main packages and everything they import into
executables. Packages not named main are ignored.
-buildmode=pie
Build the listed main packages and everything they import into
position independent executables (PIE). Packages not named
main are ignored.
-buildmode=plugin
Build the listed main packages, plus all packages that they
import, into a Go plugin. Packages not named main are ignored.
On AIX, when linking a C program that uses a Go archiv

  
## bidder_module.go
package main

import "C"

import (
	"sort"
)

//export Add
func Add(a, b int) int {
	return a + b
}

//export Sub
func Sub(a, b int) int {
	return a - b
}

//export Print
func Print(str string) {
	fmt.Printf("Go prints: %s\n", str)
}

func strFxn(input string) string {
    return "Hello " + input + " World"
}

//export StrFxn
func StrFxn(cinput *C.char) *C.char {
    // C data needs to be manually managed in memory.
    // But we will do it from C++.
    input := C.GoString(cinput)
    return C.CString(strFxn(input))
}

//export Sort
func Sort(vals []int) {
	sort.Ints(vals)
}

func main() {
	// We need the main function to make possible
	// CGO compiler to compile the package as C shared library
}

## main.cpp
#include <iostream>
#include <string>
#include "bidder_module.h"

int main() {
    int res = Add(1, 2);
    std::cout << res << std::endl;

    GoString str;
    str.p = "Hello World";
    str.n = strlen(str.p);
    Print(str);

    std::string s = "Bidder";
    char *cstr = new char[s.length()+1];
    std::strcpy (cstr, s.c_str());

    cstr = StrFxn(cstr);
    std::cout << cstr << std::endl;
    delete[] cstr;

    return 0;
}

## run.sh
# if you are on osx:
# this creates bidder_module.h and bidder_module.dylib file
go build -o bidder_module.dylib -buildmode=c-shared bidder_module.go
g++ main.cpp bidder_module.dylib -o main && ./main

# if you are on linux:
# this creates bidder_module.h and bidder_module.so file
# go build -o bidder_module.so -buildmode=c-shared bidder_module.go
# g++ main.cpp bidder_module.so -o main && ./main
	package main

	import "C"

	import (
	"sort"
	)

	//export Add
	func Add(a, b int) int {
	return a + b
	}

	//export Sub
	func Sub(a, b int) int {
	return a - b
	}

	//export Print
	func Print(str string) {
	fmt.Printf("Go prints: %s\n", str)
	}

	func strFxn(input string) string {
	return "Hello " + input + " World"
	}

	//export StrFxn
	func StrFxn(cinput C.char) C.char {
	// C data needs to be manually managed in memory.
	// But we will do it from C++.
	input := C.GoString(cinput)
	return C.CString(strFxn(input))
	}

	//export Sort
	func Sort(vals []int) {
	sort.Ints(vals)
	}

	func main() {
	// We need the main function to make possible
	// CGO compiler to compile the package as C shared library
	}
	#include <iostream>
	#include <string>
	#include "bidder_module.h"

	int main() {
	int res = Add(1, 2);
	std::cout << res << std::endl;

	GoString str;
	str.p = "Hello World";
	str.n = strlen(str.p);
	Print(str);

	std::string s = "Bidder";
	char *cstr = new char[s.length()+1];
	std::strcpy (cstr, s.c_str());

	cstr = StrFxn(cstr);
	std::cout << cstr << std::endl;
	delete[] cstr;

	return 0;
	}
	# if you are on osx:
	# this creates bidder_module.h and bidder_module.dylib file
	go build -o bidder_module.dylib -buildmode=c-shared bidder_module.go
	g++ main.cpp bidder_module.dylib -o main && ./main

	# if you are on linux:
	# this creates bidder_module.h and bidder_module.so file
	# go build -o bidder_module.so -buildmode=c-shared bidder_module.go
	# g++ main.cpp bidder_module.so -o main && ./main