[C++] Add functionality to MemoryManager for copying a slice of a buffer #39858
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pitrou
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May 23, 2024
#41477) ### Rationale for this change Currently ```MemoryManager``` objects define functionality to Copy or View entire buffers. Occasionally there is the need to only copy a single value or slice from a buffer to a piece of CPU memory (see #39770 (comment)). It's overkill to do a bunch of whole Buffer operations and manually slicing just to copy 4 or 8 bytes. ### What changes are included in this PR? Add the ```MemoryManager::CopyBufferSliceToCPU``` function, which initially attempts to use memcpy for the specified slice. If this is not possible, it defaults to copying the entire buffer and then viewing/copying the slice. Update ```ArrayImporter::ImportStringValuesBuffer``` to use this function. ### Are these changes tested? ```ArrayImporter::ImportStringValuesBuffer``` is tested as a part of ```arrow-c-bridge-test``` * GitHub Issue: #39858 Lead-authored-by: Alan Stoate <alan.stoate@gmail.com> Co-authored-by: Mac Lilly <maclilly45@gmail.com> Co-authored-by: Felipe Oliveira Carvalho <felipekde@gmail.com> Signed-off-by: Antoine Pitrou <antoine@python.org>
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vibhatha
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May 25, 2024
…pointer (apache#41477) ### Rationale for this change Currently ```MemoryManager``` objects define functionality to Copy or View entire buffers. Occasionally there is the need to only copy a single value or slice from a buffer to a piece of CPU memory (see apache#39770 (comment)). It's overkill to do a bunch of whole Buffer operations and manually slicing just to copy 4 or 8 bytes. ### What changes are included in this PR? Add the ```MemoryManager::CopyBufferSliceToCPU``` function, which initially attempts to use memcpy for the specified slice. If this is not possible, it defaults to copying the entire buffer and then viewing/copying the slice. Update ```ArrayImporter::ImportStringValuesBuffer``` to use this function. ### Are these changes tested? ```ArrayImporter::ImportStringValuesBuffer``` is tested as a part of ```arrow-c-bridge-test``` * GitHub Issue: apache#39858 Lead-authored-by: Alan Stoate <alan.stoate@gmail.com> Co-authored-by: Mac Lilly <maclilly45@gmail.com> Co-authored-by: Felipe Oliveira Carvalho <felipekde@gmail.com> Signed-off-by: Antoine Pitrou <antoine@python.org>
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Describe the enhancement requested
Currently
MemoryManagerobjects define functionality to Copy or View entire buffers. Occasionally there is the need to only copy a single value or slice from a buffer (see #39770 (comment)). It's overkill to do a bunch of wholeBufferoperations and manually slicing just to copy 4 or 8 bytes.Instead we can add new methods to the
MemoryManagerinterface such asCopyBufferSliceetc.Component(s)
C++
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