Merge "Keep the ReadFileToString/ReadFdToString overhead down." (53552048) · Commits · e / os / android_system_core

base/file.cpp

+8 −0

Original line number	Diff line number	Diff line
		@@ -49,6 +49,14 @@ using namespace android::base::utf8;
		bool ReadFdToString(int fd, std::string* content) {
		content->clear();

		// Although original we had small files in mind, this code gets used for
		// very large files too, where the std::string growth heuristics might not
		// be suitable. https://code.google.com/p/android/issues/detail?id=258500.
		struct stat sb;
		if (fstat(fd, &sb) != -1 && sb.st_size > 0) {
		content->reserve(sb.st_size);
		}

		char buf[BUFSIZ];
		ssize_t n;
		while ((n = TEMP_FAILURE_RETRY(read(fd, &buf[0], sizeof(buf)))) > 0) {

base/file_test.cpp

+43 −0

Original line number	Diff line number	Diff line
		@@ -214,3 +214,46 @@ TEST(file, Dirname) {
		EXPECT_EQ(".", android::base::Dirname("sh"));
		EXPECT_EQ("/system/bin", android::base::Dirname("/system/bin/sh/"));
		}

		TEST(file, ReadFileToString_capacity) {
		TemporaryFile tf;
		ASSERT_TRUE(tf.fd != -1);

		// For a huge file, the overhead should still be small.
		std::string s;
		size_t size = 16 * 1024 * 1024;
		ASSERT_TRUE(android::base::WriteStringToFile(std::string(size, 'x'), tf.path));
		ASSERT_TRUE(android::base::ReadFileToString(tf.path, &s));
		EXPECT_EQ(size, s.size());
		EXPECT_LT(s.capacity(), size + 16);

		// Even for weird badly-aligned sizes.
		size += 12345;
		ASSERT_TRUE(android::base::WriteStringToFile(std::string(size, 'x'), tf.path));
		ASSERT_TRUE(android::base::ReadFileToString(tf.path, &s));
		EXPECT_EQ(size, s.size());
		EXPECT_LT(s.capacity(), size + 16);

		// We'll shrink an enormous string if you read a small file into it.
		size = 64;
		ASSERT_TRUE(android::base::WriteStringToFile(std::string(size, 'x'), tf.path));
		ASSERT_TRUE(android::base::ReadFileToString(tf.path, &s));
		EXPECT_EQ(size, s.size());
		EXPECT_LT(s.capacity(), size + 16);
		}

		TEST(file, ReadFileToString_capacity_0) {
		TemporaryFile tf;
		ASSERT_TRUE(tf.fd != -1);

		// Because /proc reports its files as zero-length, we don't actually trust
		// any file that claims to be zero-length. Rather than add increasingly
		// complex heuristics for shrinking the passed-in string in that case, we
		// currently leave it alone.
		std::string s;
		size_t initial_capacity = s.capacity();
		ASSERT_TRUE(android::base::WriteStringToFile("", tf.path));
		ASSERT_TRUE(android::base::ReadFileToString(tf.path, &s));
		EXPECT_EQ(0U, s.size());
		EXPECT_EQ(initial_capacity, s.capacity());
		}