IO Buffers¶
The IO buffer data structure is the building block of the vconnection
abstraction. An IO buffer (TSIOBuffer) is composed of a list of
buffer blocks that point to buffer data. Both the buffer block
(TSIOBufferBlock) and buffer data (TSIOBufferData) data
structures are reference-counted, so they can reside in multiple buffers
at the same time. This makes it extremely efficient to copy data from
one IO buffer to another via TSIOBufferCopy(), since Traffic Server
must only copy pointers and adjust reference counts appropriately (and
doesn’t actually copy any data).
The IO buffer abstraction provides for a single writer and multiple
readers. In order for the readers to have no knowledge of each other,
they manipulate IO buffers through the TSIOBufferReader data
structure. Since only a single writer is allowed, there is no
corresponding TSIOBufferWriter data structure. The writer simply
modifies the IO buffer directly. To see an example that illustrates how
to use IOBuffers, refer to the sample code in the description of
TSIOBufferBlockReadStart().
Additional information about IO buffer functions:
- The
TSIOBufferReaderdata structure tracks how much data inTSIOBufferhas been read. It has an offset number of bytes that is the current start point of a particular buffer reader (for every read operation on anTSIOBuffer, you must allocate anTSIOBufferReader). - Bytes that have already been read may not necessarily be freed within
the
TSIOBuffer. To consume bytes that have been read, you must callTSIOBufferConsume.