POCO C++库学习和分析 -- 平台与环境

          在写程序的时候，有时候需要收集一些系统信息，用作软硬件的绑定或生成唯一的注册码信息等。Poco中提供了一个很简单的类Environment来实现这个功能。这个类的定义如下：

class Foundation_API Environment/// This class provides access to environment variables/// and some general system information.{public:typedef UInt8 NodeId[6]; /// Ethernet address.static std::string get(const std::string& name);/// Returns the value of the environment variable/// with the given name. Throws a NotFoundException/// if the variable does not exist.static std::string get(const std::string& name, const std::string& defaultValue);/// Returns the value of the environment variable/// with the given name. If the environment variable/// is undefined, returns defaultValue instead.static bool has(const std::string& name);/// Returns true iff an environment variable/// with the given name is defined.static void set(const std::string& name, const std::string& value);/// Sets the environment variable with the given name/// to the given value.static std::string osName();/// Returns the operating system name.static std::string osVersion();/// Returns the operating system version.static std::string osArchitecture();/// Returns the operating system architecture.static std::string nodeName();/// Returns the node (or host) name.static void nodeId(NodeId& id);/// Returns the Ethernet address of the first Ethernet/// adapter found on the system.////// Throws a SystemException if no Ethernet adapter is available.static std::string nodeId();/// Returns the Ethernet address (format "xx:xx:xx:xx:xx:xx")/// of the first Ethernet adapter found on the system.////// Throws a SystemException if no Ethernet adapter is available.static unsigned processorCount();/// Returns the number of processors installed in the system.////// If the number of processors cannot be determined, returns 1.static Poco::UInt32 libraryVersion();/// Returns the POCO C++ Libraries version as a hexadecimal/// number in format 0xAABBCCDD, where///    - AA is the major version number,///    - BB is the minor version number,///    - CC is the revision number, and///    - DD is the patch level number.////// Some patch level ranges have special meanings:///    - Dx mark development releases,///    - Ax mark alpha releases, and///    - Bx mark beta releases.};

          从定义中我们可以看到，它的功能包括：

          1.  获取系统第一块网卡的信息

          2.  获取、设置指定名称的环境变量值

          3.  获取操作系统名称、版本、结构

          4.  获取处理器数量

          下面是其的一个使用例子：

#include "stdafx.h"#include "Poco/Environment.h"#include <iostream>using Poco::Environment;int main(int argc, char** argv){std::cout<< "OS Name: " << Environment::osName() << std::endl<< "OS Version: " << Environment::osVersion() << std::endl<< "OS Arch: " << Environment::osArchitecture() << std::endl<< "Node Name: " << Environment::nodeName() << std::endl<< "Node ID: " << Environment::nodeId() << std::endl<< "Processor Count: " << Environment::processorCount() << std::endl<< "Library Version: " << Environment::libraryVersion() << std::endl;if (Environment::has("TEMP"))std::cout << "TEMP: " << Environment::get("TEMP") << std::endl;Environment::set("POCO", "foo");return 0;}

          Environment的内部的实现上很简单，依赖于EnvironmentImpl类，每中操作系统实现了自己的EnvironmentImpl类，从而实现了对不同操作系统统一接口。

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