Explains the functions to create and allocate flat and segmented buffers.
Allocating buffers is simple: use the desired class’s static NewL() function. You must specify a granularity,
whose meaning is particular to the buffer type.
To allocate a flat buffer, use CFlatBuf::NewL(). The granularity in this case means the number of bytes by which
the buffer will be re-allocated, whenever expansion is necessary.
If expansion by a greater amount than this is required, the next highest
multiple of the granularity will be used.
In this example, the buffer pointer is pushed to the cleanup stack for the lifetime of the buffer. If any operation involving the buffer should leave, the buffer will be destroyed. In real use, the buffer pointer would be stored as member data, and care should be taken to ensure that the consequences of a leave are not fatal to the application. For example, if the buffer is being used to store a word processor document, an attempt to add a character may fail due to lack of memory. This should never cause the entire document to be destroyed! Instead, the editing code should function in such a way that the update is either implemented successfully, or no change is made to the document.
The function StandardBufferStuffL() is one which
takes a CBufBase type.
// do flat buffer tests CBufFlat* flatBuf=CBufFlat::NewL(4); CleanupStack::PushL(flatBuf); StandardBufferStuffL(flatBuf); CleanupStack::PopAndDestroy();
A segmented buffer is allocated in a similar way to a flat buffer. The granularity in this case specifies the size of each segment. During buffer operations, each segment may contain less data than the granularity. After a compress, data is optimally distributed to segments, so that all segments except possibly the last one are full.
During their lifetime, all standard buffer
operations can be performed on either flat or segmented buffers. This
is shown in the examples above by calling standardBufferStuffL() with both a flat and a segmented buffer pointer. The argument to
this function is a CBufBase*.
The granularities chosen for these examples are much smaller than would be used in most real applications.
// do segmented buffer tests CBufSeg* segBuf=CBufSeg::NewL(4); CleanupStack::PushL(segBuf); standardBufferStuffL(segBuf); CleanupStack::PopAndDestroy();