[base] Make MappedFile work with OS file handles
adb uses its own implementation of Windows HANDLE->int mapping,
and it doesn't play well with _get_osfhandle() function used in
MappedFile::FromFd().
This CL adds another function that accepts raw handle, so adb
can pass it directly
+ make constant functions 'const'
+ make the MappedFile movable, as nothing prevents it from being
one
Test: libbase_test
Change-Id: Ifde4a4094b910e9c7b431126ecf3fef5aa3bb4a6
diff --git a/base/include/android-base/mapped_file.h b/base/include/android-base/mapped_file.h
index 2ab49ab..6a19f1b 100644
--- a/base/include/android-base/mapped_file.h
+++ b/base/include/android-base/mapped_file.h
@@ -28,15 +28,17 @@
#include <windows.h>
#define PROT_READ 1
#define PROT_WRITE 2
+using os_handle = HANDLE;
#else
#include <sys/mman.h>
+using os_handle = int;
#endif
namespace android {
namespace base {
/**
- * A region of a file mapped into memory, also known as MmapFile.
+ * A region of a file mapped into memory (for grepping: also known as MmapFile or file mapping).
*/
class MappedFile {
public:
@@ -49,16 +51,33 @@
int prot);
/**
+ * Same thing, but using the raw OS file handle instead of a CRT wrapper.
+ */
+ static MappedFile FromOsHandle(os_handle h, off64_t offset, size_t length, int prot);
+
+ /**
* Removes the mapping.
*/
~MappedFile();
- char* data() { return base_ + offset_; }
- size_t size() { return size_; }
+ /**
+ * Not copyable but movable.
+ */
+ MappedFile(MappedFile&& other);
+ MappedFile& operator=(MappedFile&& other);
+
+ char* data() const { return base_ + offset_; }
+ size_t size() const { return size_; }
+
+ bool isValid() const { return base_ != nullptr; }
+
+ explicit operator bool() const { return isValid(); }
private:
DISALLOW_IMPLICIT_CONSTRUCTORS(MappedFile);
+ void Close();
+
char* base_;
size_t size_;
diff --git a/base/mapped_file.cpp b/base/mapped_file.cpp
index f60de56..862b73b 100644
--- a/base/mapped_file.cpp
+++ b/base/mapped_file.cpp
@@ -16,13 +16,15 @@
#include "android-base/mapped_file.h"
-#include <errno.h>
+#include <utility>
-#include "android-base/unique_fd.h"
+#include <errno.h>
namespace android {
namespace base {
+static constexpr char kEmptyBuffer[] = {'0'};
+
static off64_t InitPageSize() {
#if defined(_WIN32)
SYSTEM_INFO si;
@@ -35,51 +37,86 @@
std::unique_ptr<MappedFile> MappedFile::FromFd(borrowed_fd fd, off64_t offset, size_t length,
int prot) {
- static off64_t page_size = InitPageSize();
+#if defined(_WIN32)
+ auto file =
+ FromOsHandle(reinterpret_cast<HANDLE>(_get_osfhandle(fd.get())), offset, length, prot);
+#else
+ auto file = FromOsHandle(fd.get(), offset, length, prot);
+#endif
+ return file ? std::make_unique<MappedFile>(std::move(file)) : std::unique_ptr<MappedFile>{};
+}
+
+MappedFile MappedFile::FromOsHandle(os_handle h, off64_t offset, size_t length, int prot) {
+ static const 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.get())), nullptr,
- (prot & PROT_WRITE) ? PAGE_READWRITE : PAGE_READONLY, 0, 0, nullptr);
+ HANDLE handle = CreateFileMappingW(
+ h, nullptr, (prot & PROT_WRITE) ? PAGE_READWRITE : PAGE_READONLY, 0, 0, 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});
+ if (length == 0 && ::GetLastError() == ERROR_FILE_INVALID) {
+ return MappedFile{const_cast<char*>(kEmptyBuffer), 0, 0, nullptr};
}
- return nullptr;
+ return MappedFile(nullptr, 0, 0, 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 MappedFile(nullptr, 0, 0, nullptr);
}
- return std::unique_ptr<MappedFile>(
- new MappedFile{static_cast<char*>(base), length, slop, handle});
+ return MappedFile{static_cast<char*>(base), length, slop, handle};
#else
- void* base = mmap(nullptr, file_length, prot, MAP_SHARED, fd.get(), file_offset);
+ void* base = mmap(nullptr, file_length, prot, MAP_SHARED, h, file_offset);
if (base == MAP_FAILED) {
// http://b/119818070 "app crashes when reading asset of zero length".
// mmap fails with EINVAL for a zero length region.
if (errno == EINVAL && length == 0) {
- return std::unique_ptr<MappedFile>(new MappedFile{nullptr, 0, 0});
+ return MappedFile{const_cast<char*>(kEmptyBuffer), 0, 0};
}
- return nullptr;
+ return MappedFile(nullptr, 0, 0);
}
- return std::unique_ptr<MappedFile>(new MappedFile{static_cast<char*>(base), length, slop});
+ return MappedFile{static_cast<char*>(base), length, slop};
#endif
}
+MappedFile::MappedFile(MappedFile&& other)
+ : base_(std::exchange(other.base_, nullptr)),
+ size_(std::exchange(other.size_, 0)),
+ offset_(std::exchange(other.offset_, 0))
+#ifdef _WIN32
+ ,
+ handle_(std::exchange(other.handle_, nullptr))
+#endif
+{
+}
+
+MappedFile& MappedFile::operator=(MappedFile&& other) {
+ Close();
+ base_ = std::exchange(other.base_, nullptr);
+ size_ = std::exchange(other.size_, 0);
+ offset_ = std::exchange(other.offset_, 0);
+#ifdef _WIN32
+ handle_ = std::exchange(other.handle_, nullptr);
+#endif
+ return *this;
+}
+
MappedFile::~MappedFile() {
+ Close();
+}
+
+void MappedFile::Close() {
#if defined(_WIN32)
- if (base_ != nullptr) UnmapViewOfFile(base_);
+ if (base_ != nullptr && size_ != 0) UnmapViewOfFile(base_);
if (handle_ != nullptr) CloseHandle(handle_);
+ handle_ = nullptr;
#else
- if (base_ != nullptr) munmap(base_, size_ + offset_);
+ if (base_ != nullptr && size_ != 0) munmap(base_, size_ + offset_);
#endif
base_ = nullptr;
diff --git a/base/mapped_file_test.cpp b/base/mapped_file_test.cpp
index cfde73c..3629108 100644
--- a/base/mapped_file_test.cpp
+++ b/base/mapped_file_test.cpp
@@ -44,5 +44,8 @@
ASSERT_TRUE(tf.fd != -1);
auto m = android::base::MappedFile::FromFd(tf.fd, 4096, 0, PROT_READ);
- ASSERT_EQ(0u, m->size());
+ ASSERT_NE(nullptr, m);
+ EXPECT_TRUE((bool)*m);
+ EXPECT_EQ(0u, m->size());
+ EXPECT_NE(nullptr, m->data());
}