[libvirt] virDomainInfo marshalling prolem

[arnaud.champion at devatom.fr]

Mouarf, funny thing :)


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From: "Matthias Bolte" <matthias.bolte at googlemail.com>
Sent: Friday, October 29, 2010 4:36 PM
To: "Daniel P. Berrange" <berrange at redhat.com>
Cc: <arnaud.champion at devatom.fr>; <libvir-list at redhat.com>
Subject: Re: [libvirt] virDomainInfo marshalling prolem

> 2010/10/29 Daniel P. Berrange <berrange at redhat.com>:
>> 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
>>
>
> Ah yes. I forgot about that one. So this gets even more complicated
> when you want to get the C# bindings working on 32 and 64 bit Windows
> and Linux.
>
> Matthias
>