Sorry, I understand.
Thanks for your great patience!
On 09 июля 2014 г., at 0:27, Sergey Isakov <[email protected]> wrote:
> Andrew,
> In this case buffer is not record. It is empty array.
> It is a pointer used by C program as UINT8* Buffer and doesn’t contain POOL
> record.
> It must be special codes in FreePool to get the Head of Pool list but these
> codes absent.
>
> On 09 июля 2014 г., at 0:21, Andrew Fish <[email protected]> wrote:
>
>>
>> On Jul 8, 2014, at 1:02 PM, Sergey Isakov <[email protected]> wrote:
>>
>>>
>>> On 08 июля 2014 г., at 23:56, Andrew Fish <[email protected]> wrote:
>>>
>>>> ASSERT(Buffer != NULL);
>>>> //
>>>> // Get the head & tail of the pool entry
>>>> //
>>>> Head = CR (Buffer, POOL_HEAD, Data, POOL_HEAD_SIGNATURE);
>>>> ASSERT(Head != NULL);
>>>>
>>> CR macro will not find POOL_HEAD structure. It assumes buffer contain it.
>>
>> Buffer is the pointer returned by gBS->AllocatePool() and that same pointer
>> must be passed into gBS->FreePool().
>>
>> The BASE_CR() macro does the pointer magic in the CR() macro:
>> https://svn.code.sf.net/p/edk2/code/trunk/edk2/MdePkg/Include/Base.h
>> /**
>> Macro that returns a pointer to the data structure that contains a
>> specified field of
>> that data structure. This is a lightweight method to hide information by
>> placing a
>> public data structure inside a larger private data structure and using a
>> pointer to
>> the public data structure to retrieve a pointer to the private data
>> structure.
>>
>> This function computes the offset, in bytes, of field specified by Field
>> from the beginning
>> of the data structure specified by TYPE. This offset is subtracted from
>> Record, and is
>> used to return a pointer to a data structure of the type specified by
>> TYPE. If the data type
>> specified by TYPE does not contain the field specified by Field, then the
>> module will not compile.
>>
>> @param Record Pointer to the field specified by Field within a data
>> structure of type TYPE.
>> @param TYPE The name of the data structure type to return. This
>> data structure must
>> contain the field specified by Field.
>> @param Field The name of the field in the data structure specified by
>> TYPE to which Record points.
>>
>> @return A pointer to the structure from one of it's elements.
>>
>> **/
>> #define BASE_CR(Record, TYPE, Field) ((TYPE *) ((CHAR8 *) (Record) - (CHAR8
>> *) &(((TYPE *) 0)->Field))
>>
>> So in our case:
>> Record == Buffer
>> TYPE == POOL_HEAD
>> Field == Data
>>
>> So basically “&(((TYPE *) 0)->Field)” figures out the offset of Data in the
>> POOL_HEAD struct. This offset is subtracted from Buffer, so that a pointer
>> to POOL_HEAD is returned.
>>
>>
>> The CR() macro is used in a lot of protocol implementations to get the
>> drivers private data back from the pointer to the protocol instance. The
>> memory for the protocol data structure is part of the drivers larger private
>> data.
>>
>> Thanks,
>>
>> Andrew Fish
>>
>>> ------------------------------------------------------------------------------
>>> Open source business process management suite built on Java and Eclipse
>>> Turn processes into business applications with Bonita BPM Community Edition
>>> Quickly connect people, data, and systems into organized workflows
>>> Winner of BOSSIE, CODIE, OW2 and Gartner awards
>>> http://p.sf.net/sfu/Bonitasoft_______________________________________________
>>> edk2-devel mailing list
>>> [email protected]
>>> https://lists.sourceforge.net/lists/listinfo/edk2-devel
>>
>> ------------------------------------------------------------------------------
>> Open source business process management suite built on Java and Eclipse
>> Turn processes into business applications with Bonita BPM Community Edition
>> Quickly connect people, data, and systems into organized workflows
>> Winner of BOSSIE, CODIE, OW2 and Gartner awards
>> http://p.sf.net/sfu/Bonitasoft_______________________________________________
>> edk2-devel mailing list
>> [email protected]
>> https://lists.sourceforge.net/lists/listinfo/edk2-devel
>
> ------------------------------------------------------------------------------
> Open source business process management suite built on Java and Eclipse
> Turn processes into business applications with Bonita BPM Community Edition
> Quickly connect people, data, and systems into organized workflows
> Winner of BOSSIE, CODIE, OW2 and Gartner awards
> http://p.sf.net/sfu/Bonitasoft_______________________________________________
> edk2-devel mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/edk2-devel
------------------------------------------------------------------------------
Open source business process management suite built on Java and Eclipse
Turn processes into business applications with Bonita BPM Community Edition
Quickly connect people, data, and systems into organized workflows
Winner of BOSSIE, CODIE, OW2 and Gartner awards
http://p.sf.net/sfu/Bonitasoft
_______________________________________________
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