[GitHub] [arrow] mundaym commented on a change in pull request #8011: ARROW-9803: [Go] Add initial support for s390x

[GitBox <gi...@apache.org>]

mundaym commented on a change in pull request #8011:
URL: https://github.com/apache/arrow/pull/8011#discussion_r487033507



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File path: go/arrow/type_traits_decimal128.go
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@@ -39,8 +40,13 @@ func (decimal128Traits) BytesRequired(n int) int { return Decimal128SizeBytes *
 
 // PutValue
 func (decimal128Traits) PutValue(b []byte, v decimal128.Num) {
-	binary.LittleEndian.PutUint64(b[:8], uint64(v.LowBits()))
-	binary.LittleEndian.PutUint64(b[8:], uint64(v.HighBits()))
+	if runtime.GOARCH == "s390x" {

Review comment:
       A simple 'endian' (or another name) package containing some files like this might help reduce the if statement spam, and address @emkornfield's concerns (though the compiler is pretty good at removing those branches):
   
   big.go:
   ```go
   // +build s390x
   
   package endian
   import "encoding/binary"
   var Native = binary.BigEndian
   ```
   little.go:
   ```go
   // +build !s390x
   
   package endian
   import "encoding/binary"
   var Native = binary.LittleEndian
   ```
   
   Then you can just use `endian.Native.*` functions instead of having if statements. Plus support for other big endian platforms becomes easy.
   
   (Note that even though Native is a variable the methods called on it will still be resolved at compile time because the type is constant).




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