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doc: clean up discussion of scratch space

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Justin Viiret 2016-05-03 11:12:36 +10:00 committed by Matthew Barr
parent b2ea641715
commit 3426bf57ec
1 changed files with 13 additions and 15 deletions
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doc/dev-reference/runtime.rst
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@ -124,13 +124,19 @@ databases, only a single scratch region is necessary: in this case, calling
will ensure that the scratch space is large enough to support scanning against
any of the given databases.
Importantly, only one such space is required per thread and can (and indeed
should) be allocated before data scanning is to commence. In a scenario where a
set of expressions are compiled by a single "master" thread and data will be
scanned by multiple "worker" threads, the convenience function
:c:func:`hs_clone_scratch` allows multiple copies of an existing scratch space
to be made for each thread (rather than forcing the caller to pass all the
compiled databases through :c:func:`hs_alloc_scratch` multiple times).
While the Hyperscan library is re-entrant, the use of scratch spaces is not.
For example, if by design it is deemed necessary to run recursive or nested
scanning (say, from the match callback function), then an additional scratch
space is required for that context.
In the absence of recursive scanning, only one such space is required per thread
and can (and indeed should) be allocated before data scanning is to commence.
In a scenario where a set of expressions are compiled by a single "master"
thread and data will be scanned by multiple "worker" threads, the convenience
function :c:func:`hs_clone_scratch` allows multiple copies of an existing
scratch space to be made for each thread (rather than forcing the caller to pass
all the compiled databases through :c:func:`hs_alloc_scratch` multiple times).
For example:
@ -163,14 +169,6 @@ For example:
/* Now two threads can both scan against database db,
each with its own scratch space. */
While the Hyperscan library is re-entrant, the use of scratch spaces is not.
For example, if by design it is deemed necessary to run recursive or nested
scanning (say, from the match callback function), then an additional scratch
space is required for that context.
The easiest way to achieve this is to build up a single scratch space as a
prototype, then clone it for each context:
*****************
Custom Allocators
*****************