Add API to get c slice from c++ Slice.

include/grpc++/support/slice.h

@@ -77,6 +77,9 @@ class Slice GRPC_FINAL {
   /// Raw pointer to the end (one byte \em past the last element) of the slice.
   const uint8_t* end() const { return GPR_SLICE_END_PTR(slice_); }
 
+  /// Raw C slice. Caller needs to call gpr_slice_unref when done.
+  gpr_slice c_slice() const { return gpr_slice_ref(slice_); }
+
  private:
   friend class ByteBuffer;
 

test/cpp/util/slice_test.cc

@@ -68,6 +68,16 @@ TEST_F(SliceTest, Empty) {
   CheckSlice(empty_slice, "");
 }
 
+TEST_F(SliceTest, Cslice) {
+  gpr_slice s = gpr_slice_from_copied_string(kContent);
+  Slice spp(s, Slice::STEAL_REF);
+  CheckSlice(spp, kContent);
+  gpr_slice c_slice = spp.c_slice();
+  EXPECT_EQ(GPR_SLICE_START_PTR(s), GPR_SLICE_START_PTR(c_slice));
+  EXPECT_EQ(GPR_SLICE_END_PTR(s), GPR_SLICE_END_PTR(c_slice));
+  gpr_slice_unref(c_slice);
+}
+
 }  // namespace
 }  // namespace grpc