How can we instrument a specific instruction using dyninst?

See more:

C

Linux

Injection

ELF

C++14

Using Dyninst API, we can perform both static and dynamic binary instrumentation.
In static instrumentation, we can rewrite a binary file and inject an extra code (snippets) at a specific points.
I have tested the following code in order to patch a binary code. However, this code inject the snippets at the entery of the interested function, i.e. foo.
How can we inject a snippets at a specific address?
this is the code (link to original code)

#include <stdio.h>
#include "BPatch.h"
#include "BPatch_addressSpace.h"
#include "BPatch_function.h"
#include "BPatch_binaryEdit.h"
#include "BPatch_point.h"

int main(int argc, const char *argv[]) {
    
    // Use BPatch_* classes to initialize
    BPatch bpatch;
    BPatch_addressSpace *app = bpatch.openBinary("hello", true);
    bool flag = false; 
    flag = app->loadLibrary("liblib.so");
    
    BPatch_image* image = app->getImage();
  
    std::vector<BPatch_function*> func;
    image->findFunction("code_to_inject", func);
    
    std::cout<<"\nFunction is: "<<func[0]->getName()<<std::endl;
    
    std::vector<BPatch_snippet*> openArgs;
    BPatch_funcCallExpr enter_call(*(func[0]), openArgs);
    
    func.clear();
    std::vector<BPatch_point *> *points;
    image->findFunction("foo1", func);
    points = func[0]->findPoint(BPatch_entry);
    
    app->insertSnippet(enter_call, *points);
    
    BPatch_binaryEdit *appBin = dynamic_cast<BPatch_binaryEdit *>(app);
    
    appBin->writeFile("newbinary");
      
    return 0;
}

What I have tried:

I think we should use BPatch_function and pass a specific address, but i field to comiple the modified code. Maybe we should use Dyninst::Address.
Thanks for helps