comp.lang.ruby

James Tucker

2/27/2008 12:06:00 PM

On 27 Feb 2008, at 09:24, Vikrant Singh wrote:

> Hello All,
>
> This is the first time I am working on Ruby and I am not sure if I am
> asking very basics of the language.
>
>
> I am working on a tool which is written in Ruby and I need to =20
> implement
> a new feature in it. Although it=92s a small update still to work and
> understand the code I need to learn the basics of Ruby first.
>
> I am using =93Programming Ruby, 2nd Edition=94 by Dave Thomas as a
> reference. Its a good book and I am able to proceed using it.
>
> Today I got stuck in memory handling code
>
> Following is what I am doing and need your comments on the same=85
>
> 1.Working in a function which receives number of bytes as argument.
> 2.I need to allocate memory (double in the size sent in argument) to a
> buffer and also initialize all the bits to zero.
>
> I wrote following code for the last two points=85
> def FunctionName (numBytes)
> bufferSize =3D numBytes*2
> buffer =3D dl.malloc(bufferSize)
> end

def FunctionName(numBytes)
bufferSize =3D numBytes * 2
buffer =3D "\0" * bufferSize
end

Most of the external interfaces can use strings as sets of binary =20
data, as this is our best binary representation at present.

If you use a ruby string, instead of a dl.malloc, the only thing you =20
need to ensure is that the data is not GC'd prematurely. This will =20
happen if there are no references left on the ruby side.

I can't comment on the semantics of dl, as I've never used it.

>
> I am using this dl.malloc after taking reference from existing code.
> Here I searched in the book and found that Ruby presents its own APIs
> for memory allocation.
> I also found that dl is a way of using win32 APIs instead of Ruby=92s =20=

> API.
> Which one is better?
> Also, after allocation how to make sure that memory is initialized =20
> with
> all zeros.
>
> 3.Set the 10th bit in the buffer
> buffer[bufferSize -2] =3D buffer[bufferSize -2] | 0x4
>
> 4.Execute some library calls with this buffer
> 5.Clear the buffer again
>
> I searched the book and found that clear function is used to clear the
> content of an array. I am not sure if the same will work with the
> dynamically allocated buffer as well.
> Buffer.clear
>
> 6.Execute some library calls again in this buffer
> 7.Copy the first half of the buffer in a new buffer and second half of
> the buffer in another.
>
> firstHalf =3D dl.malloc(numBytes)
> secondHalf =3D dl.malloc(numBytes)
> #Copy numBytes=85numBytes/2
> memcpy(firstHalf, buffer, numBytes)
> #Copy numbytes/2 =85 0
> Memcpy(secondHalf, buffer[0..numBytes/2], numbytes)

first_half =3D buffer[0..half]
sec_half =3D buffer[half..-1]

You won't need to memcpy if you're treating the data as a regular ruby =20=

string.

>
>
> Please reply with your view on the same. Please correct me if I am =20
> wrong
> somewhere.
> --=20
> Posted via http://www.ruby-....
>