ligang/vpp
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

docs: clarify vector element alignment description.

Browse Source 
Change-Id: I6da153779010263e6fc4b51c64b01444aaadca17
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>
This commit is contained in:
Dave Wallace
2018-12-13 12:29:44 -05:00
committed by Florin Coras
parent 4ee633e84a
commit 4659d0e823
2 changed files with 16 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
docs/gettingstarted/developers/infrastructure.md
View File

@ -48,13 +48,16 @@ macro! It's smart about NULL pointers.\]
Typically, the user header is not present. User headers allow for other
data structures to be built atop vppinfra vectors. Users may specify the
alignment for data elements via the [vec]()\*\_aligned macros.
alignment for first data element of a vector via the [vec]()\*\_aligned
macros.
Vectors elements can be any C type e.g. (int, double, struct bar). This
Vector elements can be any C type e.g. (int, double, struct bar). This
is also true for data types built atop vectors (e.g. heap, pool, etc.).
Many macros have \_a variants supporting alignment of vector data and
\_h variants supporting non-zero-length vector headers. The \_ha
variants support both.
Many macros have \_a variants supporting alignment of vector elements
and \_h variants supporting non-zero-length vector headers. The \_ha
variants support both. Additionally cacheline alignment within a
vector element structure can be specified using the
[CLIB_CACHE_LINE_ALIGN_MARK]() macro.
Inconsistent usage of header and/or alignment related macro variants
will cause delayed, confusing failures.

14
src/vppinfra/vec.h
View File

@ -70,16 +70,18 @@
Typically, the header is not present. Headers allow for other
data structures to be built atop CLIB vectors.
Users may specify the alignment for data elements via the
vec_*_aligned macros.
Users may specify the alignment for first data element of a vector
via the vec_*_aligned macros.
Vectors elements can be any C type e.g. (int, double, struct bar).
Vector elements can be any C type e.g. (int, double, struct bar).
This is also true for data types built atop vectors (e.g. heap,
pool, etc.).
Many macros have _a variants supporting alignment of vector data
and _h variants supporting non zero length vector headers.
The _ha variants support both.
Many macros have \_a variants supporting alignment of vector elements
and \_h variants supporting non-zero-length vector headers. The \_ha
variants support both. Additionally cacheline alignment within a
vector element structure can be specified using the
CLIB_CACHE_LINE_ALIGN_MARK() macro.
Standard programming error: memorize a pointer to the ith element
of a vector then expand it. Vectors expand by 3/2, so such code