ARROW-251: Expose APIs for getting code and message of the status

Author: Jihoon Son <jihoonson@apache.org>

Closes #114 from jihoonson/ARROW-251 and squashes the following commits:

d1186bf [Jihoon Son] Fix compilation failure
4275c70 [Jihoon Son] Add tests for status
1162084 [Jihoon Son] Merge branch 'master' of https://github.com/apache/arrow into ARROW-251
a76b888 [Jihoon Son] Make code() public and add message()

Author: jihoonson

cpp/src/arrow/util/CMakeLists.txt

@@ -70,3 +70,4 @@ endif()
 ADD_ARROW_TEST(bit-util-test)
 ADD_ARROW_TEST(buffer-test)
 ADD_ARROW_TEST(memory-pool-test)
+ADD_ARROW_TEST(status-test)

cpp/src/arrow/util/status-test.cc

@@ -0,0 +1,38 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include "gtest/gtest.h"
+
+#include "arrow/util/status.h"
+#include "arrow/test-util.h"
+
+namespace arrow {
+
+TEST(StatusTest, TestCodeAndMessage) {
+  Status ok = Status::OK();
+  ASSERT_EQ(StatusCode::OK, ok.code());
+  Status file_error = Status::IOError("file error");
+  ASSERT_EQ(StatusCode::IOError, file_error.code());
+  ASSERT_EQ("file error", file_error.message());
+}
+
+TEST(StatusTest, TestToString) {
+  Status file_error = Status::IOError("file error");
+  ASSERT_EQ("IOError: file error", file_error.ToString());
+}
+
+}  // namespace arrow

cpp/src/arrow/util/status.h

@@ -138,6 +138,18 @@ class ARROW_EXPORT Status {
   // Get the POSIX code associated with this Status, or -1 if there is none.
   int16_t posix_code() const;
 
+  StatusCode code() const {
+    return ((state_ == NULL) ? StatusCode::OK : static_cast<StatusCode>(state_[4]));
+  }
+
+  std::string message() const {
+    uint32_t length;
+    memcpy(&length, state_, sizeof(length));
+    std::string msg;
+    msg.append((state_ + 7), length);
+    return msg;
+  }
+
  private:
   // OK status has a NULL state_.  Otherwise, state_ is a new[] array
   // of the following form:
@@ -147,10 +159,6 @@ class ARROW_EXPORT Status {
   //    state_[7..]  == message
   const char* state_;
 
-  StatusCode code() const {
-    return ((state_ == NULL) ? StatusCode::OK : static_cast<StatusCode>(state_[4]));
-  }
-
   Status(StatusCode code, const std::string& msg, int16_t posix_code);
   static const char* CopyState(const char* s);
 };