ARROW-3347: [Abandoned] [Rust] Implement PrimitiveArrayBuilder

[paddyhoran]

This is a sub task of ARROW-3089. The scope of this builder is just for types that implement the ArrowPrimitiveType trait, i.e. PrimitiveArray's.

There are a number of follow up items that need to be addressed below. I will create JIRA's for these once/if this PR is accepted. I wanted to ensure that others agree with the approach and get some feedback.

The general idea here was to implement the Write trait for Buffer this allows Buffer to use the WriteBytesExt extension trait from the byteorder crate which allows Buffer to remain untyped while allowing types that implement ArrowPrimitiveType to be written to a Buffer instance.

The write_to_buffer method is then implemented for each primitive type leveraging these extension methods from byteorder. byteorder did not have an implementation for bool so I had to implement it myself.

The builder itself was pretty simple and leverages these other updates.

Follow up items (JIRA's to be created upon merging this PR):

• support for Option<T> where T: ArrowPrimitiveType
• add padding up to 64 bytes, From<Vec<T>> does not do this at the moment and I am testing against it (will be addressed as added in ARROW-3357: [Rust] Add a mutable buffer implementation #2658)
• expand the add_primitive_array_impl macro to u8 and i8 (this frustrated me no end...)
• expand capacity and copy over array when capacity is reached using push (will be addressed as added in ARROW-3357: [Rust] Add a mutable buffer implementation #2658)
• add example to examples folder

cc @kszucs @sunchao @andygrove

[codecov-io]

Codecov Report

Merging #2648 into master will increase coverage by 0.97%.
The diff coverage is 92.95%.

@@            Coverage Diff             @@
##           master    #2648      +/-   ##
==========================================
+ Coverage   87.19%   88.17%   +0.97%     
==========================================
  Files         381       13     -368     
  Lines       59223     1463   -57760     
==========================================
- Hits        51642     1290   -50352     
+ Misses       7507      173    -7334     
+ Partials       74        0      -74

Impacted Files	Coverage Δ
rust/src/lib.rs	100% <ø> (ø)	⬆️
rust/src/datatypes.rs	75.31% <100%> (+1.89%)	⬆️
rust/src/array.rs	86.25% <100%> (+1.07%)	⬆️
rust/src/buffer.rs	91.04% <64.28%> (-3.13%)	⬇️
python/pyarrow/ipc.pxi
cpp/src/parquet/column_page.h
cpp/src/parquet/bloom_filter-test.cc
cpp/src/plasma/client.cc
cpp/src/arrow/io/test-common.h
cpp/src/arrow/ipc/metadata-internal.h
... and 362 more

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[sunchao]

Thanks @paddyhoran , and my apologies for being late on ARROW-3089.

The general idea here was to implement the Write trait for Buffer this allows Buffer to use the WriteBytesExt extension trait from the byteorder crate which allows Buffer to remain untyped while allowing types that implement ArrowPrimitiveType to be written to a Buffer instance.

I wonder if we can add a MutableBuffer struct, alongside the existing Buffer. The former supports growing as well as modification (perhaps by implementing the Write trait), and also conversion into a Buffer.

[paddyhoran]

@sunchao no worries, thanks for the feedback.

I think Buffer is designed to be immutable (in fact I just saw that in a comment that I should have updated), adding MutableBuffer seems like a good idea.

[sunchao]

Great. Actually I’ve already have an implementation for this. Do you mind if I post a PR for this and review it perhaps? I can create a separate Jira for it.

[paddyhoran]

Sure, sounds good.

[paddyhoran]

Closing as there is no need for the byteorder crate dependency when we have MutableBuffer and ToByteSlice