Is it possible to extract data out of memory using Ruby?

Ruby
1

Is it possible to extract data out of memory using Ruby?

Something like this: Memory.get_byte(pos)

Or something like this Perl module:

Disassemble::X86::MemRegion - Represent a region of memory - metacpan.org

This Perl module is not an extension in C, I am not sure how the
author pulled that off. I looked at the source code, but I am not very
good at Perl.

  • Erik
2

2008/8/14 Erik T. [email protected]:

Is it possible to extract data out of memory using Ruby?

Erik, to read and write longs (4 bytes) I use the DL standard library
with the following code:

require “dl”

ptr = DL::PtrData.new 0
ptr.struct! “L”, “val”
size = ptr.size

read

ptr[ address, size ].unpack( “L” )[ 0 ]

write

ptr[ address, size ] = [ val ].pack( “L” )

For reading and writing bytes you have to change the “L” to something
else. See the docs for the DL standard library.

Regards,
Pit

3

So if you would like to look at the ‘in memory’ representation of a Ruby
String how would that work?

require “dl”

ptr = DL::PtrData.new 0
ptr.struct! “L”, “val”
size = ptr.size

str = ‘Hello world!’
address = str.object_id * 2
value = ptr[ address, size ]

puts [address, value].inspect

TIA,

Erik.

Pit C. wrote:

2008/8/14 Erik T. [email protected]:

Is it possible to extract data out of memory using Ruby?

Erik, to read and write longs (4 bytes) I use the DL standard library
with the following code:

require “dl”

ptr = DL::PtrData.new 0
ptr.struct! “L”, “val”
size = ptr.size

read

ptr[ address, size ].unpack( “L” )[ 0 ]

write

ptr[ address, size ] = [ val ].pack( “L” )

For reading and writing bytes you have to change the “L” to something
else. See the docs for the DL standard library.

Regards,
Pit

4

2008/8/14 Erik T. [email protected]:

So if you would like to look at the ‘in memory’ representation of a Ruby
String how would that work?

Erik, you have to look at the C source code of Ruby to find the
structure of String instances. In MRI 1.8, you can get at the address
of a Ruby object via

object.object_id * 2

Regards,
Pit