Knowledge about the Core OS layer in IOS

IOSLearning basicsCore OSLayer is the content to be introduced in this article,Core OSThe underlying functions of the layer are the basis for building many other technologies. Normally, these functions are not directly applied to applications, but to otherFramework. However, when directly processing security transactions or communicating with a peripheral, you must applyFramework.

Accelerate framework

IOS4.0 introduced AccelerateFrameworkAccelerate. framework ). TheFrameworkCan be used to perform mathematical, big numbers, and DSP operations. Compared with the library compiled by the developerFrameworkThe advantage is that it is based on the existingIOSThe hardware configuration of the device has been optimized. Therefore, you only need to code it once to ensure that it runs efficiently on all devices.

To learn more about AccelerateFramework, Please view AccelerateFrameworkFor more information, see.

External Accessory framework

IOS 3.0 introduces the External Accessory framework ExternalAccessory. framework) to support communication between iOS devices and bound attachments. The attachment can be connected to the device through a 30-pin pedestal interface or through Bluetooth. With the External Accessory framework, you can obtain information about each peripheral and initialize a communication session. After the communication Session Initialization is complete, you can use the commands supported by the device to directly operate it.

For more information about how to use the External Accessory framework, see Introduction to External Accessory programming. For more information about related classes in the External Accessory framework, see the External Accessory framework reference. For details about how to develop iOS device attachments, visit http://www.apple.com.cn.

Security Framework

IOSThe system not only provides built-in Security functions, but also provides SecurityFrameworkSecurity. framework) is used to ensure the Security of the data managed by the application. TheFrameworkThe provided interfaces can be used to manage certificates, public keys, private keys, and trust policies. It supports generating encrypted pseudo-random numbers. At the same time, it also supports saving certificates and Keychain keys, and is a secure repository for sensitive user data.

The CommonCrypto interface also supports symmetric encryption, HMAC, and Digests. In fact, the functions of Digests are compatible with those commonly used in the OpenSSL library,IOSThe OpenSSL library cannot be used.

InIOSIn systems 3.0 and later versions, you can share certain Keychain items with multiple applications created, so that applications in the same suite can interact smoothly. For example, you can share the user password and other elements between applications. In this way, you do not need to prompt the user separately in each application. If the application needs to share data, the Xcode project of each application must be properly qualified.

To learn more about SecurityFrameworkFor more information, see Security framework reference. To learn how to access the Keychain, see the Keychain Service programming guide. For more information about how to set the application qualification in the Xcode project, seeIOSDevelopment Guide. For more information about which application qualifications can be configured, see the Keychain service reference
SecItemAdd

Function.

System

The system layer includes the kernel environment, driver, and the underlying UNIX interface of the operating system. The kernel is based on Mach and is responsible for all aspects of the operating system, including managing the virtual memory, threads, file systems, networks, and inter-process communication of the system. The driver contained in this layer is system hardware and SystemFramework. For security considerations, the kernel and driver only allow a few systemsFrameworkAnd Application access.

Applications can useIOSProvided

LibSystem

Library to access a variety of underlying features of the operating system.

LibSystem

The library interface is based on the C language and can support the following functions:

Threads (POSIX Threads)

Network (BSD sockets)

File System Access

Standard I/O

Bonjour and DNS services

Region Information

Memory Allocation

Mathematical computing

ManyCore OSThe header file of the technology is located in <IOS_ SDK>

 
 

  
  
/usr/include/ 
 
 

Directory, <IOS_ SDK> is the path of the target sdk in the Xcode installation directory. For more information about the functions associated with these technologies, visitIOSManual page.

Summary:IOSLearning basicsCore OSI hope this article will help you.