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// Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
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// All rights reserved.
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// This component and the accompanying materials are made available
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// under the terms of the License "Eclipse Public License v1.0"
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// which accompanies this distribution, and is available
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// at the URL "http://www.eclipse.org/legal/epl-v10.html".
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//
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// Initial Contributors:
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// Nokia Corporation - initial contribution.
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//
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// Contributors:
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//
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// Description:
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// e32/include/e32shbufcmn.h
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// Shareable Data Buffers
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/**
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@file
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@publishedPartner
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@prototype
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*/
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#ifndef E32SHBUFCMN_H
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#define E32SHBUFCMN_H
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#include <e32shbuf_priv.h>
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#include <e32def.h>
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/**
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Defines values used to modify client behaviour when opening a pool or buffer in a new process.
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@publishedPartner
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@prototype
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*/
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enum TShPoolHandleFlags
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{
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/**
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The buffers will be writeable in the process where this handle is used.
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If not set, the buffers will be read-only.
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*/
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EShPoolWriteable = 0x0001,
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/**
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The process will be able to allocate buffers from this pool.
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If not set, the process will not be able to allocate buffers from this pool.
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*/
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EShPoolAllocate = 0x0002,
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};
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/**
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Defines flags for RShBuf::Alloc() and DShPool::Alloc().
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@see RShBuf::Alloc()
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@see DShPool::Alloc()
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@publishedPartner
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@prototype
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*/
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enum TShPoolAllocFlags
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{
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/**
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The thread is willing to wait for a pool grow if no buffer is immediately available.
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If this is not set, the Alloc() will return immediately if no free buffer is available,
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but the pool might be able to grow to create new buffers.
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*/
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EShPoolAllocCanWait = 0x0001,
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/**
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Do not automatically map the newly-allocated buffer into this process, if the pool is page-aligned.
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(RShBuf::Alloc() only.)
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*/
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EShPoolAllocNoMap = 0x0002,
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};
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/**
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Defines the attributes of a pool.
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@publishedPartner
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@prototype
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*/
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class TShPoolInfo
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{
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public:
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IMPORT_C TShPoolInfo();
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/**
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Specifies the size of each buffer in the pool.
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*/
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TUint iBufSize;
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/**
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Specifies the initial number of buffers to be allocated to the pool.
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*/
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TUint iInitialBufs;
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/**
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Specifies the maximum number of buffers the pool can grow to.
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*/
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TUint iMaxBufs;
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/**
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This specifies when the pool grows. If zero, the pool will not grow or shrink
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automatically.
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This is the proportion of free buffers left in the pool at which it should be grown.
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For example, if the ratio is 0.1, the pool will be grown when the number of free
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buffers drops to 10%.
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This value is expressed as a 32-bit fixed-point number, where the binary
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point is defined to be between bits 7 and 8 (where the least-significant
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bit is defined as bit 0). (This format is also known as a Q8, or fx24.8
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number, or alternatively as the value * 256.) For the example given of 10%,
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use the value 26. It represents a value < 1 (i.e. must be < 256). Calculations
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are rounded down towards zero, but if calculating how many buffers to trigger
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on gives 0, the grow will be triggered when 1 buffer is free.
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*/
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TUint iGrowTriggerRatio;
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/**
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This specifies the proportion by which to grow the pool each time it is grown.
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If zero, the pool will not grow or shrink automatically.
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It is expressed as a 32-bit fx24.8 fixed-point number, in the same way as
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iGrowTriggerRatio. Calculations are rounded down towards zero, but if calculating
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how many buffers to grow by yields 0, then the pool will be grown by 1 buffer.
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*/
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TUint iGrowByRatio;
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/**
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The hysteresis value to ensure that the pool does not automatically shrink
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immediately after is grows.
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Automatic shrinking will only happen when there are (iGrowTriggerRatio +
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iGrowByRatio) * iShrinkHysteresisRatio * (total buffers in the pool) free
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buffers left in the pool.
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The amount by which the pool is shrunk depends on iGrowByRatio: it is the operational
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inverse, such that the pool would shrink down to the same number of buffers if shrunk
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immediately after growing (although hysteresis normally prevents this).
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For example, if iGrowByRatio is 10%, a pool of 100 buffers would grow to 110 buffers.
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To shrink back to 100, a shrink ratio of 10/110 = 9% is required. That is, if the
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grow-by ration is G, the shrink-by ratio S is calculated as S = 1 - 1 / (1 + G).
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iShrinkHysteresisRatio is a 32-bit fx24.8 fixed-point number in the same way as
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iGrowTriggerRatio and iGrowByRatio. It represents a value > 1 (i.e. must be > 256).
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@see iGrowByRatio
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*/
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TUint iShrinkHysteresisRatio;
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/**
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Specifies the alignment for each buffer, as a shift count (log2 bytes).
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For example, 9 means that each buffer is aligned on a 512-byte boundary.
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*/
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TUint iAlignment;
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/**
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Specifies flags for the pool, as bit values from TShPoolCreateFlags or-ed together.
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@see TShPoolCreateFlags
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*/
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TUint iFlags;
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private:
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TInt iSpare1; // Reserved for future use
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TInt iSpare2;
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TInt iSpare3;
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TInt iSpare4;
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};
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#endif // E32SHBUF_H
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