I am trying to convert some of the ruby interpreter code called in C to mruby format. I am stuck and would appreciate help here.
My testruby.rb file content:
#require 'MyMod'
def helloworld(var1)
puts "You said #{var1}"
return MyMod.Issue1(var1).to_s
end
Below is the snippet of my C++ file:
Issue 1:
static mrb_value Issue1(mrb_state *mrb, mrb_value mrb_self)
{
mrb_??? val1; // What should be the type for string and where to find all the types?
mrb_get_args(mrb, "s", ?);
// How to manipulate val1? Say I want to concatenate few more data.
return mrb_????(val1); // How do I return this value?
}
The above method, I am sending as a module to the mruby interpreter so that .rb file can call this.
Please let me know if below format is the correct one:
struct RClass *mod = mrb_define_module(mrb, "MyMod");
mrb_define_module_function(mrb, mod, "SumI", Issue1, MRB_ARGS_REQ(1));
Issue2:
How do I convert the below ruby interpreter code to mruby?
rb_require("./testruby"); // where testruby is my testruby.rb file
Now I want to call the helloworld method from testruby.rb file. How do I call the equivalent method for mruby (for rb_funcall)?
How do I read the return value from the helloworld method in my c++ code?
Regards,
Re val1: mrb_value is the type that can hold any mruby object
Manipulating val1 could be done using mrb_funcall. That function returns a mrb_value:
mrb_value my_str = mrb_funcall(mrb_context, your_object, "your_method", 0);
printf("my_str = %s\n", RSTRING_PTR(my_str));
Re issue 2: There's no require in mruby: mrbgems are compiled and linked statically with the target binary (they are listed in the top-level build_config.rb file).
(A gem called mruby-require exists to mimic CRuby's require, but I've never used it)
Related
I am using (Unicode) Inno Setup 6.0.5 on Windows 10 64-bit.
The exported symbol, I want to use has the signature:
typedef int(__stdcall *GetDirVST2x86) (LPWSTR lpString1);
The Inno Setup [Code] section has its declaration as:
function GetDirVST2x86(var lpString1: String): Integer;
external 'GetDirVST2x86#files:R2RINNO.DLL stdcall setuponly';
where, lpString1 will contain a pointer to the wide-string after the function returns and R2RINNO.DLL is a 32-bit DLL.
Now my problem is, if I compile and run this setup, a read access violation occurs right when I try to retrieve the value. I get the correct result when I execute this same function from a C program. Removing the var from the prototype declaration in Inno script fetches an empty (or possibly) empty or blank string, so that doesn't help either.
I don't have the source for the DLL I wish to use, and I figured out the signature from IDA. The scripting engine Inno Setup seems hopelessly inadequate as it doesn't support pointers at all.
One interesting thing I observed was if I changed the type of lpString1 to Cardinal or Integer and used IntToStr to fetch the string I got the value of the directory in which the setup was getting created.
Here's a working C code:
#include <windows.h>
#include <stdio.h>
#define _UNICODE
#define UNICODE
typedef int(WINAPI *GetDirVST2x86) (LPWSTR );
int main() {
HMODULE hModule = LoadLibrary("R2RINNO.DLL");
if (NULL != hModule) {
GetDirVST2x86 pGetDirVST2x86 = (GetDirVST2x86) GetProcAddress (hModule, "GetDirVST2x86");
if (NULL != pGetDirVST2x86) {
LPWSTR lpszVST2x86;
pGetDirVST2x86(lpszVST2x86);
wprintf(lpszVST2x86);
}
FreeLibrary(hModule);
}
}
Here's the output:
C:\Program Files (x86)\Steinberg\VstPlugins
Here's the IDA screenshot of the function I want to use:
Pascal Script equivalent of the C declaration should be:
function GetDirVST2x86(lpString1: string): Integer;
external 'GetDirVST2x86#files:R2RINNO.DLL stdcall setuponly';
(i.e. no var, as it is an input character pointer argument).
Assuming the function contract is that you (as a caller) allocate a buffer and provide it to the function to be filled in, you should call the function like this:
var
Buf: string;
begin
{ Allocate buffer for the result large enough according to the API specification }
SetLength(Buf, 1000);
GetDirVST2x86(Buf);
SetLength(Result, Pos(#0, Result) - 1);
end;
See also How to return a string from a DLL to Inno Setup?
I need to create a parameter file that can be managed across a Python 3.7 and a C code base. This file needs to be modifiable either by the C or the Python program with the changes being taking effect on the other software (an update function will handle reading the updated file). It's best if the file is not human readable, as it contains information that is better left obfuscated.
**Is there a recommended method to do so? **
I could create separate python and C files, but the set of parameters will change over time (for code maintenance), and the values would be changed by these programs. The list would also be very long. It would be a hassle to maintain two different files and update them over time. Also, the file may need to be exchanged between users, such that a version modified by the software ran by user1 needs to be readable by the software run by user2. The idea is that other parts of both codes could access parts of the parameter list without knowing the full contents of the list.
To clarify the example, I could have a parameter.h file containing:
struct {
double par1 =1.1;
int par 2 =2;
} par_list
And I could have a parameter.py with:
class par_list:
def(__self__):
self.par1 = double(1.1)
self.par2 = int(2)
Then, by doing a import in Python or a include in C, I could initialize the parameter list. But in this case the parameters are being read on different files.
I'm considering using some kind of binary file to keep the values, and create a script that writes both the Python and C code that reads and updates the values. I'm concerned because the binary file would need to be interchangeable between ARM architecture running Linux, and x86 architecture running Windows.
Here is an example working with numpy:
C code:
#include <stdio.h>
#include <stdint.h>
struct Struct_format{
uint8_t the_unsigned_int8;
int32_t the_signed_int32[2];
double the_double;
};
typedef struct Struct_format upperStruct;
//Use separate file to define default value:
void printStruct(upperStruct test_struct){
printf("test_struct.the_unsigned_int8 = %d\n", test_struct.the_unsigned_int8);
printf("test_struct.the_signed_int32[0] = %d\n", test_struct.the_signed_int32[0]);
printf("test_struct.the_signed_int32[1] = %d\n", test_struct.the_signed_int32[1]);
printf("test_struct.the_double = %f\n", test_struct.the_double);
}
void main(){
//Define a "default" value:
upperStruct fromC2Python = {4U,{-3,-1},2.1};
printf("Printing fromC2Python\n");
printStruct(fromC2Python);
//Save this default in a file:
FILE * fid = fopen("fromC2Python.bin","w");
fwrite((void *)&fromC2Python, sizeof(fromC2Python) ,1, fid);
fclose(fid);
//Now load the file created by Python:
upperStruct fromPython2C;
FILE * fid_py = fopen("fromPython2C.bin","r");
fread(&fromPython2C, sizeof(fromPython2C) ,1, fid_py);
fclose(fid_py);
printf("Printing fromPython2C\n");
printStruct(fromPython2C);
}
Python code:
import numpy
datatype = numpy.dtype([('potato',
[('time', numpy.uint8),
('sec', numpy.int32, 2)]),
('temp', numpy.float64)],
align=True)
fromPython2C = numpy.array([((5, (-6, -7)), 61.55)], dtype=datatype)
print(fromPython2C)
fromPython2C.tofile("fromPython2C.bin", sep="")
fromC2Python = numpy.fromfile("fromC2Python.bin", dtype=datatype, count=-1, sep="")
print(fromC2Python)
print(fromC2Python['potato'])
print(fromC2Python['potato']['time'])
print(fromC2Python['temp'])
The ideia is that numpy allows reading and writing to structured binary files. Hence, it suffices to create the dtype specification with a text parser.
I am using libxml in my iOS Swift project. To debug, I need to call the following C function from Swift:
void xmlDebugDumpString (FILE * output, const xmlChar * r)
However, I don't know how to create the FILE * output pointer in Swift.
I tried the following code:
let debugDoc: UnsafeMutablePointer<FILE>
debugDoc = fopen(debugDocURL.absoluteString, "w")
xmlDebugDumpNode(debugDoc, str)
The code compiled fine but gives the following runtime error
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
The problem is the wrong usage of absoluteString, so that fopen()
fails and returns nil. The correct way to create a C string from an URL is withUnsafeFileSystemRepresentation:
guard let debugFile = debugDocURL.withUnsafeFileSystemRepresentation( { fopen($0, "w") }) else {
// Could not open file ...
}
Now you can write to the file
xmlDebugDumpNode(debugFile, ...)
and eventually close it:
fclose(debugFile)
An alternative option is to dump the debug output to the (predefined)
“standard error” file:
xmlDebugDumpNode(stderr, ...)
I am reading a file say x.c and I have to find for the string "shared". Once the string like that has been found, the following has to be done.
Example:
shared(x,n)
Output has to be
*var = &x;
*var1 = &n;
Pointers can be of any name. Output has to be written to a different file. How to do this?
I'm developing a source to source compiler for concurrent platforms using lex and yacc. This can be a routine written in C or if u can using lex and yacc. Can anyone please help?
Thanks.
If, as you state, the arguments can only be variables and not any kind of other expressions, then there are a couple of simple solutions.
One is to use regular expressions, and do a simple search/replace on the whole file using a pretty simple regular expression.
Another is to simply load the entire source file into memory, search using strstr for "shared(", and use e.g. strtok to get the arguments. Copy everything else verbatim to the destination.
Take advantage of the C preprocessor.
Put this at the top of the file
#define shared(x,n) { *var = &(x); *var1 = &(n); }
and run in through cpp. This will include external resources also and replace all macros, but you can simply remove all #something lines from the code, convert using injected preprocessor rules and then re-add them.
By the way, why not a simple macro set in a header file for the developer to include?
A doubt: where do var and var1 come from?
EDIT: corrected as shown by johnchen902
When it comes to preprocessor, I'll do this:
#define shared(x,n) (*var=&(x),*var1=&(n))
Why I think it's better than esseks's answer?
Suppose this situation:
if( someBool )
shared(x,n);
else { /* something else */ }
In esseks's answer it will becomes to:
if( someBool )
{ *var = &x; *var1 = &n; }; // compile error
else { /* something else */ }
And in my answer it will becomes to:
if( someBool )
(*var=&(x),*var1=&(n)); // good!
else { /* something else */ }
I'm writing an app that calls ruby code from c. I am having a little difficulty and wondered if anyone could point me in the rite direction.
I currently have in my C.
#include ruby.h
main()
{
ruby_init();
rb_require("myRubyFile");
rb_funcall(rb_module_new(), rb_intern("RubyFunction"), 0, NULL);
}
My ruby file is in the same directory as my c file and is called myRubyFile.rb and contains a definition of the function RubyFunction().
This is a cut down of what I actually want to do, just making it more readable for others. I just require some feedback as to whether this is the correct method to call ruby code from my c file.
Regards
Short answer:
extern VALUE rb_vm_top_self(void); /* Assumes 1.9. Under 1.8, use the global
* VALUE ruby_top_self
*/
...
rb_funcall(rb_vm_top_self(), /* irb> RubyFunction() */
rb_intern("RubyFunction"), /* irb> self.RubyFunction() # same thing */
0,
NULL);
Longer answer:
The first argument to rb_funcall is the receiver of the method call.
Assuming you defined RubyFunction() outside of any explicit class or module context, then it is added to the eigenclass of the implicit, main object at the "top level" of every ruby vm.
In ruby, this object is accessible as the top-level self:
$ cat myRubyFile.rb
# file: myRubyFile.rb
def foo
puts "foo"
end
$ irb
irb> require "myRubyFile"
=> true
irb> foo
foo
=> nil
irb> self.foo() # same thing, more explicit
foo
=> nil
irb> self
=> main
In C under 1.9 it is accessible as indicated above.
I try to use the following approach:
Basic struct to share data
typedef struct ruby_shared_data {
VALUE obj;
ID method_id;
int nargs;
VALUE args[4];
} ruby_shared_data;
Create a function for call ruby objects on some part of your code
static VALUE ruby_callback(VALUE ptr) {
ruby_shared_data *data = (ruby_shared_data*)ptr;
return rb_funcall2(data->obj,data->method_id,data->nargs,data->args);
}
On some part of your code...
ruby_shared_data rbdata;
rbdata.obj = obj;
rbdata.method_id = rb_intern("mycallback");
rbdata.nargs = 1;
rbdata.args[0] = rb_str_new2("im a parameter");
int error = 0;
VALUE result = rb_protect(ruby_callback,(VALUE)&rbdata,&error);
if (error)
throw "Ruby exception on callback";
Is always a good idea to wrap rb_funcall with rb_protect.
Another interesting thing is to know the parameters of the callback, one approach is the following
ruby_shared_data rbdata;
rbdata.obj = callback;
rbdata.method_id = rb_intern("arity");
rbdata.nargs = 0;
int error = 0;
VALUE result = rb_protect(ruby_callback,(VALUE)&rbdata,&error);
if (error)
throw "Ruby exception on callback";
narguments = NUM2INT(result);
I don't like to call ruby from inside C unless you have complex C project which you don't want to re-build in ruby.
There are two ways to interact between C and ruby. You can extend ruby with code written in C. See SWIG.
Or you can embed ruby, see here, here and here.
BTW, what do you mention is "embed" ruby, not "extend" ruby.