Ri Xu Online

In this post, I build a shared library and dynamic library by a Go source code and use it for spreadsheet decryption. A Shared Object/Library is a binary file with a dynamic/static loading table for functions.

Go language Source Code

// decrypt.go
package main

import "C"
import (
    "fmt"

    "github.com/xuri/excelize/v2"
)

//export  decryption
func decryption(file *C.char, passwd *C.char) {
    f, err := excelize.OpenFile(C.GoString(file), excelize.Options{Password: C.GoString(passwd)})
    if err != nil {
        return
    }
    defer func() {
        if err := f.Close(); err != nil {
            fmt.Println(err)
        }
    }()
    if err := f.SaveAs("decrypted workbook.xlsx", excelize.Options{}); err != nil {
        fmt.Println(err)
    }
}

func main() {
}

Build shared libraries

Build a dynamic shared library

go build -o libdecrypt.so -buildmode=c-shared decrypt.go

It will generate two files: libdecrypt.a and libdecrypt.h.

Build a static shared library

go build -o libdecrypt.a -buildmode=c-archive

It will generate two files: libdecrypt.so and libdecrypt.h.

Using a dynamic shared library in C++ program

// decrypt.cpp
#include <stdio.h>
#include <unistd.h>

#include "libdecrypt.h"

int main() {
    decryption((char*)"encryptAES.xlsx", (char*)"password");
}

Build a executable file:

gcc -v decrypt.cpp -o decrypt ./libdecrypt.so

By executing the following command we can get decrypted spreadsheet: decrypted workbook.xlsx.

./decrypt

Using a static shared library in C program

// decrypt.c
#include "libdecrypt.h"


int main ()
{
    decryption("encryptAES.xlsx", "password");
}

Build a executable file:

gcc -o decrypt decrypt.c libdecrypt.a -lpthread

By executing the following command we can get decrypted spreadsheet.

./decrypt

That explains how to build the dynamic and static shared library (shared object) in Go, and how to use them.

The open-source project excelize-py is a practice for more complex scenario such as complex custom data structure.