Draft API for Arrow IO wrappers for Python files

Change-Id: I712800f68cd0c9b0de1cca0d511f3f7d297c05b2

python/src/pyarrow/common.h

@@ -19,9 +19,7 @@
 #define PYARROW_COMMON_H
 
 #include "pyarrow/config.h"
-
 #include "arrow/util/buffer.h"
-
 #include "pyarrow/visibility.h"
 
 namespace arrow { class MemoryPool; }

python/src/pyarrow/io.cc

@@ -0,0 +1,90 @@
+// 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 "pyarrow/common.h"
+
+#include <cstdlib>
+#include <sstream>
+
+#include <arrow/util/memory-pool.h>
+#include <arrow/util/status.h>
+#include "pyarrow/status.h"
+
+namespace pyarrow {
+
+// ----------------------------------------------------------------------
+// Seekable input stream
+
+PyReadableFile::PyReadableFile(PyObject* file)
+    : file_(file) {
+  Py_INCREF(file);
+}
+
+PyReadableFile::~PyReadableFile() {
+  Py_DECREF();
+}
+
+arrow::Status PyReadableFile::ReadAt(
+    int64_t position, int64_t nbytes, int64_t* bytes_read, uint8_t* out) override {
+
+  return Status::OK();
+}
+
+arrow::Status PyReadableFile::GetSize(int64_t* size) override {
+  return Status::OK();
+}
+
+  // Does not copy if not necessary
+Status PyReadableFile::ReadAt(
+    int64_t position, int64_t nbytes, std::shared_ptr<Buffer>* out) override {
+
+  return Status::OK();
+}
+
+bool PyReadableFile::supports_zero_copy() const {
+  return false;
+}
+
+// ----------------------------------------------------------------------
+// Output stream
+
+PyOutputStream::PyOutputStream(PyObject* file)
+    : file_(file) {
+  Py_INCREF(file);
+}
+
+PyOutputStream::~PyOutputStream() {
+  Py_DECREF(file_);
+}
+
+Status PyOutputStream::Close() override {
+  return arrow::Status::OK();
+}
+
+Status PyOutputStream::Tell(int64_t* position) {
+  return arrow::Status::OK();
+}
+
+Status PyOutputStream::Write(const uint8_t* data, int64_t nbytes) {
+  return arrow::Status::OK();
+}
+
+private:
+  PyObject* file_;
+};
+
+} // namespace pyarrow

python/src/pyarrow/io.h

@@ -0,0 +1,63 @@
+// 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.
+
+#ifndef PYARROW_COMMON_H
+#define PYARROW_COMMON_H
+
+#include "arrow/io/interfaces.h"
+
+#include "pyarrow/config.h"
+#include "pyarrow/visibility.h"
+
+namespace arrow { class MemoryPool; }
+
+namespace pyarrow {
+
+class PYARROW_EXPORT PyReadableFile : public arrow::io::ReadableFileInterface {
+public:
+  explicit PyReadableFile(PyObject* file);
+  ~PyReadableFile();
+
+  arrow::Status ReadAt(
+      int64_t position, int64_t nbytes, int64_t* bytes_read, uint8_t* out) override;
+
+  arrow::Status GetSize(int64_t* size) override;
+
+  // Does not copy if not necessary
+  arrow::Status ReadAt(
+      int64_t position, int64_t nbytes, std::shared_ptr<Buffer>* out) override;
+
+  bool supports_zero_copy() const override;
+
+private:
+  PyObject* file_;
+};
+
+class PYARROW_EXPORT PyOutputStream : public arrow::io::OutputStream {
+public:
+  explicit PyOutputStream(PyObject* file);
+  ~PyOutputStream();
+
+  arrow::Status Close() override;
+  arrow::Status Tell(int64_t* position) override;
+  arrow::Status Write(const uint8_t* data, int64_t nbytes) override;
+
+private:
+  PyObject* file_;
+};
+
+} // namespace pyarrow