1 files changed, 71 insertions, 0 deletions
diff --git a/base/mapped_file.cpp b/base/mapped_file.cpp
new file mode 100644
index 000000000..f7901afa4
--- /dev/null
+++ b/base/mapped_file.cpp
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed 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 "android-base/mapped_file.h"
+
+namespace android {
+namespace base {
+
+static off64_t InitPageSize() {
+#if defined(_WIN32)
+  SYSTEM_INFO si;
+  GetSystemInfo(&si);
+  return si.dwAllocationGranularity;
+#else
+  return sysconf(_SC_PAGE_SIZE);
+#endif
+}
+
+std::unique_ptr<MappedFile> MappedFile::FromFd(int fd, off64_t offset, size_t length, int prot) {
+  static off64_t page_size = InitPageSize();
+  size_t slop = offset % page_size;
+  off64_t file_offset = offset - slop;
+  off64_t file_length = length + slop;
+
+#if defined(_WIN32)
+  HANDLE handle =
+      CreateFileMapping(reinterpret_cast<HANDLE>(_get_osfhandle(fd)), nullptr,
+                        (prot & PROT_WRITE) ? PAGE_READWRITE : PAGE_READONLY, 0, 0, nullptr);
+  if (handle == nullptr) return nullptr;
+  void* base = MapViewOfFile(handle, (prot & PROT_WRITE) ? FILE_MAP_ALL_ACCESS : FILE_MAP_READ, 0,
+                             file_offset, file_length);
+  if (base == nullptr) {
+    CloseHandle(handle);
+    return nullptr;
+  }
+  return std::unique_ptr<MappedFile>(
+      new MappedFile{static_cast<char*>(base), length, slop, handle});
+#else
+  void* base = mmap(nullptr, file_length, prot, MAP_SHARED, fd, file_offset);
+  if (base == MAP_FAILED) return nullptr;
+  return std::unique_ptr<MappedFile>(new MappedFile{static_cast<char*>(base), length, slop});
+#endif
+}
+
+MappedFile::~MappedFile() {
+#if defined(_WIN32)
+  if (base_ != nullptr) UnmapViewOfFile(base_);
+  if (handle_ != nullptr) CloseHandle(handle_);
+#else
+  if (base_ != nullptr) munmap(base_, size_);
+#endif
+
+  base_ = nullptr;
+  offset_ = size_ = 0;
+}
+
+}  // namespace base
+}  // namespace android