Merge "[base] Make MappedFile work with OS file handles" (2bb4f40d) · Commits · e / os / android_system_core

base/include/android-base/mapped_file.h

+22 −3

Original line number	Diff line number	Diff line
		@@ -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:
		@@ -48,17 +50,34 @@ class MappedFile {
		static std::unique_ptr<MappedFile> FromFd(borrowed_fd fd, off64_t offset, size_t length,
		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_;

base/mapped_file.cpp

+55 −18

Original line number	Diff line number	Diff line
		@@ -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 @@ static off64_t InitPageSize() {

		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;

base/mapped_file_test.cpp

+4 −1

Original line number	Diff line number	Diff line
		@@ -44,5 +44,8 @@ TEST(mapped_file, zero_length_mapping) {
		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());
		}