[arrow] branch main updated: GH-35911: [Go] Fix method CastToBytes of decimal256Traits (#35912)

[zeroshade]

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The following commit(s) were added to refs/heads/main by this push:
     new 4ec231b234 GH-35911: [Go] Fix method CastToBytes of decimal256Traits 
(#35912)
4ec231b234 is described below

commit 4ec231b23432e9af340ed1a10d914f9bee84aca7
Author: Igor Izvekov <izvei...@gmail.com>
AuthorDate: Tue Jun 6 17:45:06 2023 +0300

    GH-35911: [Go] Fix method CastToBytes of decimal256Traits (#35912)
    
    
    
    ### Rationale for this change
    
    ### What changes are included in this PR?
    
    ### Are these changes tested?
    Yes
    
    ### Are there any user-facing changes?
    Yes
    
    * Closes: #35911
    
    Authored-by: izveigor <izvei...@gmail.com>
    Signed-off-by: Matt Topol <zotthewiz...@gmail.com>
---
 go/arrow/type_traits_decimal256.go |  2 +-
 go/arrow/type_traits_test.go       | 45 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/go/arrow/type_traits_decimal256.go 
b/go/arrow/type_traits_decimal256.go
index b213df32fb..38d26ce100 100644
--- a/go/arrow/type_traits_decimal256.go
+++ b/go/arrow/type_traits_decimal256.go
@@ -59,7 +59,7 @@ func (decimal256Traits) CastToBytes(b []decimal256.Num) 
[]byte {
        h := (*reflect.SliceHeader)(unsafe.Pointer(&b))
 
        var res []byte
-       s := (*reflect.SliceHeader)(unsafe.Pointer(&b))
+       s := (*reflect.SliceHeader)(unsafe.Pointer(&res))
        s.Data = h.Data
        s.Len = h.Len * Decimal256SizeBytes
        s.Cap = h.Cap * Decimal256SizeBytes
diff --git a/go/arrow/type_traits_test.go b/go/arrow/type_traits_test.go
index 3b9571d3d3..a54d2d7c69 100644
--- a/go/arrow/type_traits_test.go
+++ b/go/arrow/type_traits_test.go
@@ -24,6 +24,7 @@ import (
 
        "github.com/apache/arrow/go/v13/arrow"
        "github.com/apache/arrow/go/v13/arrow/decimal128"
+       "github.com/apache/arrow/go/v13/arrow/decimal256"
        "github.com/apache/arrow/go/v13/arrow/float16"
 )
 
@@ -133,6 +134,50 @@ func TestDecimal128Traits(t *testing.T) {
        }
 }
 
+func TestDecimal256Traits(t *testing.T) {
+       const N = 10
+       nbytes := arrow.Decimal256Traits.BytesRequired(N)
+       b1 := arrow.Decimal256Traits.CastToBytes([]decimal256.Num{
+               decimal256.New(0, 0, 0, 10),
+               decimal256.New(1, 1, 1, 10),
+               decimal256.New(2, 2, 2, 10),
+               decimal256.New(3, 3, 3, 10),
+               decimal256.New(4, 4, 4, 10),
+               decimal256.New(5, 5, 5, 10),
+               decimal256.New(6, 6, 6, 10),
+               decimal256.New(7, 7, 7, 10),
+               decimal256.New(8, 8, 8, 10),
+               decimal256.New(9, 9, 9, 10),
+       })
+
+       b2 := make([]byte, nbytes)
+       for i := 0; i < N; i++ {
+               beg := i * arrow.Decimal256SizeBytes
+               end := (i + 1) * arrow.Decimal256SizeBytes
+               arrow.Decimal256Traits.PutValue(b2[beg:end], 
decimal256.New(uint64(i), uint64(i), uint64(i), 10))
+       }
+
+       if !reflect.DeepEqual(b1, b2) {
+               v1 := arrow.Decimal256Traits.CastFromBytes(b1)
+               v2 := arrow.Decimal256Traits.CastFromBytes(b2)
+               t.Fatalf("invalid values:\nb1=%v\nb2=%v\nv1=%v\nv2=%v\n", b1, 
b2, v1, v2)
+       }
+
+       v1 := arrow.Decimal256Traits.CastFromBytes(b1)
+       for i, v := range v1 {
+               if got, want := v, decimal256.New(uint64(i), uint64(i), 
uint64(i), 10); got != want {
+                       t.Fatalf("invalid value[%d]. got=%v, want=%v", i, got, 
want)
+               }
+       }
+
+       v2 := make([]decimal256.Num, N)
+       arrow.Decimal256Traits.Copy(v2, v1)
+
+       if !reflect.DeepEqual(v1, v2) {
+               t.Fatalf("invalid values:\nv1=%v\nv2=%v\n", v1, v2)
+       }
+}
+
 func TestMonthIntervalTraits(t *testing.T) {
        const N = 10
        b1 := arrow.MonthIntervalTraits.CastToBytes([]arrow.MonthInterval{