Provide a concrete implementation of bdlbb::BlobBufferFactory.
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Namespaces |
| namespace | bdlbb |
Detailed Description
- Outline
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- Purpose:
- Provide a concrete implementation of
bdlbb::BlobBufferFactory.
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- Classes:
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- See also:
- Component bdlbb_blob, Component bdlma_concurrentpool
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- Description:
- This component provides a mechanism for allocating
bdlbb::BlobBuffer objects of a fixed specified size. The size is passed at construction of the bdlbb::PooledBlobBufferFactory instance. A bdlbb::BlobBuffer is basically a shared pointer to a buffer of char of the prescribed size. Thus it is generally more efficient to create them with a uniform size, for the same reason as a pool is more efficient than a general-purpose memory allocator. In order to gain further efficiency, this factory allocates the shared pointer representation together with the buffer (contiguously).
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- Potential Lifetime Issues:
- Be aware that the destruction of a
bdlbb::PooledBlobBufferFactory object releases all the BlobBuffer objects allocated by that factory. A common misconception is that, because of the use of shared_ptr, the data referred to in BlobBuffer objects created will remain valid until the last shared reference is destroyed, even if a reference outlives the PooledBlobBufferFactory that created it. This is not the case. Destroying a PooledBlobBufferFactory releases any memory created by that pool, even if shared references remain to the data, and it is therefore undefined behavior to use any BlobBuffer created by a pool after that pool is destroyed. A user must clearly understand the lifetime of memory allocated by a subsystem, and scope the lifetime of the PooledBlobBufferFactory to be greater than the active lifetime of that subsystem.
