From: pjb@... (Pascal J. Bourguignon)
Date: 2008-03-17T22:44:55+09:00
Subject: Re: How to make an unix library from some ruby code?

Pavel Smerk <smerk@fi.muni.cz> writes:

> Marc Heiler wrote:
>>> I need to have some functionality "packaged" as an unix library
>> Just write the ruby code or use what is already available.
>> Ruby can do the same what the unix tools can. Its just a question of
>> how much work to invest :-)
>
> Unfortunately, I definitely need a library which could be easily used
> in C programs (or elsewhere). A ruby script does not fit my needs.
>
> Because it is possible to embed Perl interpreter to a C program (man
> perlembed, http://perldoc.perl.org/perlembed.html), I believe there
> could be something similar in Ruby.


But unix provides all that is needed to do such a thing.


/* pseudo-code */

typedef struct ruby{
    int to_ruby; 
    int from_ruby;
} ruby;

ruby* init_ruby(){
   int to_ruby[2];
   int from_ruby[2];
   int res=0;
   res=pipe(to_ruby); if(res!=0){perror("pipe");exit(1);}
   res=pipe(from_ruby); if(res!=0){perror("pipe");exit(1);}
   if(0==fork()){
       close(to_ruby[0]);
       close(from_ruby[1]);
       ruby* r=malloc(sizeof(ruby));
       r->to_ruby=to_ruby[1];
       r->from_ruby=from_ruby[0];
       return(r);
   }else{
       close(to_ruby[0]);
       close(from_ruby[1]);
       close(0);
       close(1);
       dup2(to_ruby[1],0);
       dup2(from_ruby[0],1);
       execl("/usr/bin/irb");
       exit(0);
   }  
}

char* ruby_eval(ruby* r,const char* e){
   while(strlen(e)>0){
      int wrote=write(r->to_ruby,e,strlen(e));
      if(wrote<0){
          perror("write to ruby");
          exit(1);
      }else{
          e+=wrote;
      }
   }
   {
      int   bufsize=65536;
      char* buffer=malloc(bufsize);
      int readed=read(r->from_ruby,buffer,bufsize-1);
      if(readed<0){
          /* actually, should check for EAGAIN, etc */
          perror("read from ruby");
      }
      buffer[readed]=0;
      return(buffer);
   }
}


so now you can write:

ruby* r=init_ruby();
printf("%s\n",ruby_eval(r,"[1,2,3].length;\n"););
// etc...


You don't need a _library_ for just two routines, I would think...

-- 
__Pascal Bourguignon__