Test the size() method and fix bug with missing whence

Change-Id: I2ef9faca323f333e7f828d757d8740d20e5e467a

python/pyarrow/tests/test_io.py

@@ -48,10 +48,13 @@ def test_python_file_write():
 
 
 def test_python_file_read():
-    buf = BytesIO(b'some sample data')
+    data = b'some sample data'
 
+    buf = BytesIO(data)
     f = io.PythonFileInterface(buf, mode='r')
 
+    assert f.size() == len(data)
+
     assert f.tell() == 0
 
     assert f.read(4) == b'some'
@@ -70,10 +73,13 @@ def test_python_file_read():
 
 def test_bytes_reader():
     # Like a BytesIO, but zero-copy underneath for C++ consumers
-    f = io.BytesReader(b'some sample data')
+    data = b'some sample data'
+    f = io.BytesReader(data)
 
     assert f.tell() == 0
 
+    assert f.size() == len(data)
+
     assert f.read(4) == b'some'
     assert f.tell() == 4
 

python/src/pyarrow/common.h

@@ -133,7 +133,7 @@ class PYARROW_EXPORT NumPyBuffer : public arrow::Buffer {
 class PYARROW_EXPORT PyBytesBuffer : public arrow::Buffer {
  public:
   PyBytesBuffer(PyObject* obj);
-  virtual ~PyBytesBuffer();
+  ~PyBytesBuffer();
 
  private:
   PyObject* obj_;

python/src/pyarrow/io.cc

@@ -66,7 +66,7 @@ arrow::Status PythonFile::Close() {
 
 arrow::Status PythonFile::Seek(int64_t position, int whence) {
   // whence: 0 for relative to start of file, 2 for end of file
-  PyObject* result = PyObject_CallMethod(file_, "seek", "(i)", position);
+  PyObject* result = PyObject_CallMethod(file_, "seek", "(ii)", position, whence);
   Py_XDECREF(result);
   ARROW_RETURN_NOT_OK(CheckPyError());
   return arrow::Status::OK();