iOS Framework Introduction (VI)---Core OS tier

Directory

1. Core OS Layer
1. Accelerate frame
2. External Accessory Frame
3. Security Framework
4. System

Core OS Layer

The underlying functionality of the Core OS layer is the foundation of many other technologies. Typically, these features are not applied directly to the application, but are applied to other frameworks. However, when dealing directly with a security transaction or communicating with a peripheral, you must apply the framework to that layer.

Accelerate frame

IOS 4.0 introduces the accelerate framework ( Accelerate.framework ). The interface of the framework can be used to perform mathematical, large-number, and DSP operations. The advantage of this framework is that it is optimized based on the hardware configuration of the various existing iOS devices, compared to the library that the developer personally wrote. As a result, you only need to encode once to ensure that it runs efficiently on all devices.

To learn more about the accelerate framework, see the Accelerate Framework reference .

External Accessory Frame

externalaccessory.framework ), which enables iOS devices to communicate with bound attachments. The attachment can be connected via a 30-pin docking station and the device, or via Bluetooth. With the external accessory framework, you can obtain information for each peripheral and initialize a communication session. After the communication session has been initialized, you can manipulate it directly using the commands that the device supports.

For more information on how the External accessory framework is used, see External Accessory Programming Overview . For information about the related classes in the External accessory framework, see the External Accessory Framework Reference . To learn how to develop iOS device attachments, please visit the http://www.apple.com.cn/developer/ page.

Security Framework

The iOS system not only provides built-in security features, but also provides security framework ( Security.framework ) to keep the data managed by the application secure. The framework provides interfaces that can be used to manage certificates, public keys, private keys, and trust policies. It supports generating encrypted security pseudo-random numbers. It also supports the storage of certificates and keychain keys and is a secure repository for user-sensitive data.

The Commoncrypto interface also supports symmetric encryption, HMAC, and digests. In fact, Digests's functionality is compatible with the functionality commonly used by the OpenSSL library, but iOS cannot use the OpenSSL library.

In IOS 3.0 and subsequent versions of the system, you can have multiple applications created that share certain keychain items, which allows for smoother application interoperability within the same suite. As an example, you can share user passwords and other elements among applications. In this way, you do not need to give users a separate hint in each application. If your application needs to share data, the Xcode project for each application must be appropriately qualified.

For further information on the features and features of the security framework, please review the Security framework reference . For information on how to access Keychain, please review the Keychain Service Programming Guide . To learn how to qualify your app in the Xcode project, check out the IOS Development Guide . To find out which application qualifications you can configure, see the functions in the Keychain Service reference SecItemAdd .

System

The system layer includes kernel environment, driver and operating system underlying UNIX interface. The kernel is based on Mach, which is responsible for all aspects of the operating system, including managing the system's virtual memory, threads, file systems, networks, and interprocess communication. This layer contains the drivers that are the interface of the system hardware and the system framework. For security reasons, the kernel and the driver only allow access to a few system frameworks and applications.

Applications can use the libraries provided by iOS to LibSystem access the underlying features of various operating systems. LibSystemthe interface of the library is based on the C language, which provides support for the following functions:

• Threads (POSIX threads)

• Network (BSD sockets)

• File system access

• Standard I/O

• Bonjour and DNS Services

• Regional information

• Memory allocation

• Mathematical calculations

The header files for many Core OS technologies are located in the <iOS_SDK> /usr/include/ directory, and<iOS_SDK> is the path to the target SDK in the Xcode installation directory. If you need to know about the features associated with these technologies, please visit the iOS Manuals page .

iOS Framework Introduction (VI)---Core OS layer (RPM)