.

t/neo/xcommon/xslice/slice.go

@@ -7,7 +7,7 @@ import (
 
 // Grow increase length of slice by n elements.
 // If there is not enough capacity the slice is reallocated.
-// The memory for grown elements are not initialized.
+// The memory for grown elements is not initialized.
 func Grow(b []byte, n int) []byte {
 	ln := len(b) + n
 	if ln <= cap(b) {
@@ -33,6 +33,18 @@ func Resize(b []byte, n int) []byte {
 }
 
 
+// Realloc resizes the slice to be of length n not preserving content.
+// If slice length is increased and there is not enough capacity the slice is reallocated.
+// The memory for all elements becomes uninitialized.
+// XXX semantic clash with C realloc(3) ? or it does not matter?
+func Realloc(b []byte, n int) []byte {
+	if cap(b) >= n {
+		return b[:n]
+	}
+
+	return make([]byte, n, xmath.CeilPow2(uint64(n)))
+}
+
 // TODO Resize without copy ?
 
 // // GrowSlice makes sure cap(b) >= n.

t/neo/xcommon/xslice/slice_test.go

 package xslice
 
-//import (
-//	"testing"
-//)
-
-// TODO
-
-// func TestGrowSlice(t *testing) {
-// 	testv := []struct {in []byte, n int, Cap int} {
-// 		{nil, 0, 0},
-// 	}
-// 
-// }
+import (
+	"bytes"
+	"reflect"
+	"testing"
+	"unsafe"
+)
+
+// aliases returns whether two slice memory is aliased
+func aliases(b1, b2 []byte) bool {
+	s1 := (*reflect.SliceHeader)(unsafe.Pointer(&b1))
+	s2 := (*reflect.SliceHeader)(unsafe.Pointer(&b2))
+	return s1.Data == s2.Data
+}
+
+func TestSlice(t *testing.T) {
+	s := make([]byte, 0, 10)
+
+	testv := []struct {op func([]byte, int) []byte; n, Len, Cap int; aliased bool; content []byte} {
+		// op,    n, Len, Cap, aliased, content
+		{Grow,     5,  5, 10, true,  []byte{0,0,0,0,0}},
+
+		// here "Hello" is assigned
+		{Grow,     6, 11, 16, false, []byte("Hello\x00\x00\x00\x00\x00\x00")},
+		{Resize,   8,  8, 16, true,  []byte("Hello\x00\x00\x00")},
+		{Resize,  17, 17, 32, false, []byte("Hello\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00")},
+		{Realloc, 16, 16, 32, true,  []byte("Hello\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00")},
+		{Realloc, 33, 33, 64, false, make([]byte, 33)},
+	}
+
+	for i, tt := range testv {
+		sprev := s
+		s = tt.op(s, tt.n)
+
+		if !(len(s) == tt.Len && cap(s) == tt.Cap && bytes.Equal(s, tt.content)) {
+			t.Fatalf("step %d: %v: unexpected slice state: %v", i, tt, s)
+		}
+
+		if !(aliases(s, sprev) == tt.aliased) {
+			t.Fatalf("step %d: %v: unexpected slice aliasing: %v", aliases(s, sprev))
+		}
+
+
+		// assign data after fisrt iteration
+		if i == 0 {
+			copy(s, "Hello")
+		}
+	}
+}