This change modifies Gonum to support Slice in Struct

cmem/encoder.go

@@ -4,6 +4,10 @@
 
 package cmem
 
+// #include <stdlib.h>
+// #include <string.h>
+import "C"
+
 import (
 	"encoding/binary"
 	"fmt"
@@ -26,8 +30,16 @@ func init() {
 // subsequently write an in memory object to a PacketTable using Append().
 type Encoder struct {
 	// Buf contains the encoded data.
-	Buf    []byte
-	offset int
+	Buf          []byte
+	offset       int
+	pointerSlice []unsafe.Pointer
+}
+
+// FreeMemory is to free memory from C
+func (enc *Encoder) FreeMemory() {
+	for i := 0; i < len(enc.pointerSlice); i++ {
+		C.free(enc.pointerSlice[i])
+	}
 }
 
 // Encode encodes the value passed as data to binary form stored in []Buf. This
@@ -61,7 +73,39 @@ func (enc *Encoder) Encode(data interface{}) error {
 	rt := rv.Type()
 
 	switch rt.Kind() {
-	case reflect.Slice, reflect.Array:
+	case reflect.Slice:
+		length := C.size_t(reflect.ValueOf(data).Len())
+		msize := C.size_t(rv.Index(0).Type().Size() * uintptr(length))
+
+		// this is variable length data, it should follow hvl_t format
+		enc.Encode(length)
+
+		pointer := C.malloc(msize)
+		enc.pointerSlice = append(enc.pointerSlice, pointer)
+
+		C.memset(pointer, 0, msize)
+
+		var tempBuf []byte
+		for i := 0; i < rv.Len(); i++ {
+			var myenc Encoder
+			if err := myenc.Encode(rv.Index(i).Interface()); err != nil {
+				return err
+			}
+			mypad := myenc.offset - len(myenc.Buf)
+			if mypad > 0 {
+				myenc.Buf = append(myenc.Buf, make([]byte, mypad)...)
+			}
+
+			tempBuf = append(tempBuf, myenc.Buf...)
+		}
+		// copy contents from temp buf to C memory
+		C.memcpy(pointer, unsafe.Pointer(&tempBuf[0]), msize)
+
+		enc.Encode(C.size_t(uintptr(pointer)))
+
+		return nil
+
+	case reflect.Array:
 		for i := 0; i < rv.Len(); i++ {
 			if err := enc.Encode(rv.Index(i).Interface()); err != nil {
 				return err

cmem/encoder_test.go

@@ -6,51 +6,50 @@ package cmem
 
 import (
 	"bytes"
-	"encoding/binary"
-	"strconv"
 	"testing"
+	"encoding/binary"
 )
 
 func TestEncode(t *testing.T) {
-	for i, tc := range []struct {
-		v    interface{}
-		want []byte
-	}{
-		{
-			v: struct {
-				V1 uint8
-				V2 uint64
-				V3 uint8
-				V4 uint16
-			}{1, 2, 3, 4},
-			want: []byte{
-				0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // |........|
-				0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // |........|
-				0x03, 0x00, 0x04, 0x00, /*                   */ // |....|
-			},
-		},
-		{
-			v: []int32{1, 20, 300, 4000, 50000, 600000, 7000000, 8000000},
-			want: []byte{
-				0x01, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, // |........|
-				0x2c, 0x01, 0x00, 0x00, 0xa0, 0x0f, 0x00, 0x00, // |,.......|
-				0x50, 0xc3, 0x00, 0x00, 0xc0, 0x27, 0x09, 0x00, // |P....'..|
-				0xc0, 0xcf, 0x6a, 0x00, 0x00, 0x12, 0x7a, 0x00, // |..j...z.|
-			},
-		},
-	} {
-		t.Run(strconv.Itoa(i), func(t *testing.T) {
-			oldEndian := nativeEndian
-			nativeEndian = binary.LittleEndian
-			defer func() { nativeEndian = oldEndian }()
-			var enc Encoder
-			err := enc.Encode(tc.v)
-			if err != nil {
-				t.Fatalf("could not encode: %v", err)
-			}
-			if !bytes.Equal(enc.Buf, tc.want) {
-				t.Fatalf("encoding error:\ngot = %v\nwant= %v", enc.Buf, tc.want)
-			}
-		})
+	v := struct {
+		V1 uint8
+		V2 uint64
+		V3 uint8
+		V4 uint16
+	}{1, 2, 3, 4}
+	want := []byte{
+		0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // |........|
+		0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // |........|
+		0x03, 0x00, 0x04, 0x00, /*                   */ // |....|
+	}
+	var enc Encoder
+	err := enc.Encode(v)
+	if err != nil {
+		t.Fatalf("could not encode: %v", err)
 	}
+	if !bytes.Equal(enc.Buf, want) {
+		t.Fatalf("encoding error:\ngot = %v\nwant= %v", enc.Buf, want)
+	}
+}
+
+func TestEncodeSlice(t *testing.T) {
+	v := []int32{1, 20, 300, 4000, 50000, 600000, 7000000, 8000000}
+	want := []byte{
+		0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // |........|
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // |,.......|
+	}
+	var enc Encoder
+	err := enc.Encode(v)
+	if err != nil {
+		t.Fatalf("could not encode: %v", err)
+	}
+	pointer := enc.pointerSlice[0]
+	bs := make([]byte, 8)
+        binary.LittleEndian.PutUint64(bs, uint64(uintptr(pointer)))
+	copy(want[8:16], bs[:])
+
+	if !bytes.Equal(enc.Buf, want) {
+		t.Fatalf("encoding error:\ngot = %v\nwant= %v", enc.Buf, want)
+	}
+
 }

h5pt_table.go

@@ -79,6 +79,8 @@ func (t *Table) Append(args ...interface{}) error {
 	}
 
 	var enc cmem.Encoder
+	defer enc.FreeMemory()
+
 	for _, arg := range args {
 		if err := enc.Encode(arg); err != nil {
 			return err