Support zero-length mapped files

Bug: http://b/119818070 "app crashes when reading asset of zero length"

Add support for zero-length mappings for the Windows code path as well.

Test: ran libbase_test on Windows under wine.
Change-Id: Iccb65fa800c636444100c9369f41e36d24a53a99

1 files changed, 8 insertions, 1 deletions

diff --git a/base/mapped_file.cpp b/base/mapped_file.cpp
index faa845d14..7c65dc3c5 100644
--- a/base/mapped_file.cpp
+++ b/base/mapped_file.cpp
@@ -41,7 +41,14 @@ std::unique_ptr<MappedFile> MappedFile::FromFd(int fd, off64_t offset, size_t le
   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;
+  if (handle == nullptr) {
+    // http://b/119818070 "app crashes when reading asset of zero length".
+    // Return a MappedFile that's only valid for reading the size.
+    if (length == 0) {
+      return std::unique_ptr<MappedFile>(new MappedFile{nullptr, 0, 0, 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) {