Roll forward to cl/314549634

Change-Id: I4d1e7eacd5fa4078a094571ad6d5f51e422535ff

cpp/platform_v2/impl/shared/file.cc

@@ -0,0 +1,81 @@
+#include "platform_v2/impl/shared/file.h"
+
+#include <cstddef>
+#include <memory>
+
+#include "platform_v2/base/exception.h"
+#include "absl/strings/string_view.h"
+
+namespace location {
+namespace nearby {
+namespace shared {
+
+// InputFile
+
+InputFile::InputFile(const std::string& path, std::int64_t size)
+    : file_(path), path_(path), total_size_(size) {}
+
+ExceptionOr<ByteArray> InputFile::Read(std::int64_t size) {
+  if (!file_.is_open()) {
+    return ExceptionOr<ByteArray>{Exception::kIo};
+  }
+
+  if (file_.peek() == EOF) {
+    return ExceptionOr<ByteArray>{ByteArray{}};
+  }
+
+  if (!file_.good()) {
+    return ExceptionOr<ByteArray>{Exception::kIo};
+  }
+
+  ByteArray bytes(size);
+  std::unique_ptr<char[]> read_bytes{new char[size]};
+  file_.read(read_bytes.get(), static_cast<ptrdiff_t>(size));
+  auto num_bytes_read = file_.gcount();
+  if (num_bytes_read == 0) {
+    return ExceptionOr<ByteArray>{Exception::kIo};
+  }
+
+  return ExceptionOr<ByteArray>(ByteArray(read_bytes.get(), num_bytes_read));
+}
+
+Exception InputFile::Close() {
+  if (file_.is_open()) {
+    file_.close();
+  }
+  return {Exception::kSuccess};
+}
+
+// OutputFile
+
+OutputFile::OutputFile(absl::string_view path) : file_(std::string(path)) {}
+
+Exception OutputFile::Write(const ByteArray& data) {
+  if (!file_.is_open()) {
+    return {Exception::kIo};
+  }
+
+  if (!file_.good()) {
+    return {Exception::kIo};
+  }
+
+  file_.write(data.data(), data.size());
+  file_.flush();
+  return {file_.good() ? Exception::kSuccess : Exception::kIo};
+}
+
+Exception OutputFile::Flush() {
+  file_.flush();
+  return {file_.good() ? Exception::kSuccess : Exception::kIo};
+}
+
+Exception OutputFile::Close() {
+  if (file_.is_open()) {
+    file_.close();
+  }
+  return {Exception::kSuccess};
+}
+
+}  // namespace shared
+}  // namespace nearby
+}  // namespace location