[libvirt] virDomainInfo marshalling prolem

[Daniel P. Berrange]

On Fri, Oct 29, 2010 at 04:19:22PM +0200, Matthias Bolte wrote:
> 2010/10/29  <arnaud.champion at devatom.fr>:
> > Hi,
> >
> > I am working on the marshaling of the virDomainInfo structure. I have
> > marshalled it in this way :
> >
> >
> > ///
> >
> > <summary>
> >
> > /// Structure to handle domain informations
> >
> > /// </summary>
> >
> > [
> >
> > StructLayout(LayoutKind.Sequential)]
> >
> > public class DomainInfo
> >
> > {
> >
> >     /// <summary>
> >     /// The running state, one of virDomainState.
> >     /// </summary>
> >     private Byte state;
> >     /// <summary>
> >     /// The maximum memory in KBytes allowed.
> >     /// </summary>
> >     public int maxMem;
> >     /// <summary>
> >     /// The memory in KBytes used by the domain.
> >     /// </summary>
> >     public int memory;
> >     /// <summary>
> >     /// The number of virtual CPUs for the domain.
> >     /// </summary>
> >     public short nrVirtCpu;
> >     /// <summary>
> >     /// The CPU time used in nanoseconds.
> >     /// </summary>
> >     public long cpuTime;
> >     /// <summary>
> >     /// The running state, one of virDomainState.
> >     /// </summary>
> >     public DomainState State { get { return (DomainState)state; } }
> >
> > }
> >
> > It work fine in 32 bits, but not in 64 bits, it seems that packing in 64
> > bits is different so infos are not in order. Am I right ?
> >
> 
> In the struct looks like this
> 
> struct _virDomainInfo {
>     unsigned char state;        /* the running state, one of virDomainState */
>     unsigned long maxMem;       /* the maximum memory in KBytes allowed */
>     unsigned long memory;       /* the memory in KBytes used by the domain */
>     unsigned short nrVirtCpu;   /* the number of virtual CPUs for the domain */
>     unsigned long long cpuTime; /* the CPU time used in nanoseconds */
> };
> 
> but you mapped unsigned long to int. First of all you should map this
> to an unsigned type. You also lost the unsigned for some other
> members.
> 
> The problem probably is that long in C is 32bit on a 32bit platform an
> 64bit on a 64bit platform. You mapped it to int that is always 32bit
> in C#, when I looked it up correctly.

Not quite. Windows just had to do things diffrently on 64-bit and so used
the LLP64 model instead of LP64 used by the rest of the world :-(

  http://technet.microsoft.com/en-us/library/bb496995.aspx

  In the UNIX/64 data model:
      The size of int is 32 bits and the size of long and pointers is 64 bits.

  In the Win64 model:
      The size of int and long is 32 bits; the size of int64 (new type) and pointers is 64 bits.

Regards,
Daniel
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