{"id":73,"date":"2021-07-16T03:32:08","date_gmt":"2021-07-15T19:32:08","guid":{"rendered":"http:\/\/139.224.63.49\/?p=73"},"modified":"2021-08-17T22:51:05","modified_gmt":"2021-08-17T14:51:05","slug":"c%e4%b8%ad%e9%81%87%e5%88%b0%e7%9a%84%e4%b8%80%e4%b8%aa%e5%a4%9a%e7%ba%bf%e7%a8%8b%e9%97%ae%e9%a2%98","status":"publish","type":"post","link":"http:\/\/iamnear.top\/?p=73","title":{"rendered":"c#\u4e2d\u9047\u5230\u7684\u4e00\u4e2a\u591a\u7ebf\u7a0b\u95ee\u9898"},"content":{"rendered":"\n

\u6628\u5929\u5728\u8c03\u8bd5c#\u7a0b\u5e8f\u7684\u65f6\u5019\uff0c\u9047\u5230\u4e86\u4e2a\u95ee\u9898\uff0c\u6000\u7591\u662f\u591a\u7ebf\u7a0b\u7ade\u4e89\u4ea7\u751f\u7684\u95ee\u9898\u3002\u5728\u6b64\u8bb0\u5f55\u4e0b\u3002<\/p>\n\n\n\n

\u95ee\u9898\u7b80\u5355\u6765\u8bf4\u662f\u8fd9\u6837\u7684\uff1a\u7a0b\u5e8f\u9700\u8981\u4e0d\u65ad\u5730\u4ece\u8bbe\u5907\u4e0a\u8bfb\u53d6\u6570\u636e\uff0c\u8bbe\u5907\u4e0a\u7684\u6570\u636e\u662f\u4e2a\u6574\u6570\uff0c\u800c\u4e14\u662f\u968f\u65f6\u95f4\u9012\u589e\u7684\u3002\u4f46\u662f\u4ec0\u4e48\u65f6\u5019\u9012\u589e\u662f\u4e0d\u5b9a\u7684\u3002<\/p>\n\n\n\n

\u7a0b\u5e8f\u9700\u8981\u5b8c\u6210\u7684\u662f\u5728\u8bbe\u5907\u4e0a\u7684\u6570\u636e\u589e\u52a0\u7684\u65f6\u5019\uff0c\u8c03\u7528\u4e00\u4e2a\u56de\u8c03\u51fd\u6570\u3002\u6211\u7684\u5b9e\u73b0\u662f\u4f7f\u7528System.Timers.Timer\u5b9a\u65f6\u5668\uff0c\u6bcf50ms\u4f1a\u53bb\u67e5\u8be2\u4e00\u4e0b\u8bbe\u5907\u7684\u6570\u636e\uff0c\u5982\u679c\u8bbe\u5907\u7684\u6570\u636e\u548c\u6211\u7c7b\u4e2d\u4e4b\u524d\u8bb0\u5f55\u7684\u6570\u636e\u4e0d\u4e00\u81f4\uff0c\u90a3\u4e48\u5c31\u662f\u9012\u589e\u4e86\uff0c\u5c31\u8c03\u7528\u90a3\u4e2a\u56de\u8c03\u51fd\u6570\u3002<\/p>\n\n\n\n

\u8c03\u8bd5\u4e2d\u53d1\u73b0\u6709\u65f6\u4f1a\u51fa\u73b0\u4e00\u4e2a\u73b0\u8c61\uff1a\u8bbe\u5907\u4e0a\u7684\u6570\u636e\u968f\u65f6\u95f4\u4ece1\u4f9d\u6b21\u9012\u589e\u5230\u4e864\uff0c\u4f46\u662f\u56de\u8c03\u51fd\u6570\u5374\u88ab\u8c03\u7528\u4e865\u6b21\uff0c\u56e0\u6b64\u5728\u56de\u8c03\u51fd\u6570\u4e2d\u4ea7\u751f\u4e86\u903b\u8f91\u9519\u8bef\uff0c\u4ece\u800c\u629b\u51fa\u4e86\u5f02\u5e38\u3002<\/p>\n\n\n\n

\u4ee3\u7801\u5927\u6982\u5982\u4e0b\u903b\u8f91<\/p>\n\n\n\n

class Example\n{\n\tint oldvalue = -1;\n\tvoid timer_callback()\/\/be called every 50ms\n\t{\n\t\tint data = get_data_from_device();\n\t\tif(data!=oldvalue)\n\t\t{\n\t\t\toldvalue = data;\n\t\t\tinvoke_callback_function();\n\t\t}\n\t}\n}<\/code><\/pre>\n\n\n\n
\u6211\u4e3b\u8981\u662f\u901a\u8fc7Console.WriteLine\u6765\u786e\u5b9a\u51fd\u6570\u6709\u6ca1\u6709\u6267\u884c\u4ee5\u53ca\u6267\u884c\u987a\u5e8f\u7684\uff0c\u5177\u4f53\u8fd9\u4e2a\u5199\u63a7\u5236\u53f0\u7684IO\u64cd\u4f5c\uff0c\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\u662f\u5426\u80fd\u6b63\u5e38\u53cd\u5e94\u7a0b\u5e8f\u7684\u987a\u5e8f\u8fd8\u4e0d\u597d\u8bf4\u3002<\/p>\n\n\n\n
\u901a\u8fc7\u63a7\u5236\u53f0\u7684\u65e5\u5fd7\u53d1\u73b0\uff0c\u6709\u4e24\u6b21\u4ece\u8bbe\u5907\u5f97\u5230\u7684\u662f\u540c\u6837\u7684data\uff0c\u4f46\u662f\u90fd\u8c03\u7528\u4e86\u56de\u8c03\u51fd\u6570\u3002\u5355\u7ebf\u7a0b\u7a0b\u5e8f\u4e2d\u663e\u7136\u4e0d\u4f1a\u6709\u8fd9\u6837\u7684\u95ee\u9898\uff0c\u6240\u4ee5\u6211\u5c31\u57fa\u672c\u786e\u5b9a\u8fd9\u4e2a\u95ee\u9898\u8ddf\u591a\u7ebf\u7a0b\u6709\u5173\u3002<\/p>\n\n\n\n
c#\u4e2d\u67093\u4e2d\u4e0d\u540c\u7684Timer\u3002\u6211\u7528\u7684\u8fd9\u4e2aSystem.Timers.Timer\u4f3c\u4e4e\u662f\u901a\u8fc7\u7ebf\u7a0b\u6c60\u5b9e\u73b0\u7684\uff0c\u901a\u8fc7\u6253\u5370Thread.CurrentThread.ManagedThreadId\u53ef\u4ee5\u786e\u5b9atimer_callback\u662f\u4f1a\u5728\u4e0d\u540c\u7684\u7ebf\u7a0b\u4e2d\u88ab\u8c03\u7528\u7684\u3002<\/p>\n\n\n\n
\u6240\u4ee5\u6211\u505a\u4e86\u4e2a\u4fee\u6539\uff0c\u5c06oldvalue\u52a0\u4e86\u4e2avolatile\u5c5e\u6027\u3002\u7136\u800c\uff0c\u5e76\u6ca1\u6709\u89e3\u51b3\u95ee\u9898\u3002\u6211\u60f3\u8d77\u6765\u770b\u8fc7\u4e00\u4e9bc++\u65b9\u9762\u7684\u4e66\uff0c\u91cc\u9762\u5f3a\u8c03volatile\u4e0d\u80fd\u7528\u4e8e\u591a\u7ebf\u7a0b\u7684\u540c\u6b65\u3002c#\u4e2d\u5462\uff1f\u6211\u53bb\u67e5\u4e86\u67e5\u3002\u53d1\u73b0\u4e0d\u8bba\u4e2d\u6587csdn\u6216\u8005\u535a\u5ba2\u56ed\u8fd8\u662fstackoverflows\u91cc\u9762\u5f88\u591a\u4eba\u90fd\u8ba4\u4e3avolatile\u53ef\u4ee5\u201d\u8ba9\u5bf9\u53d8\u91cf\u7684\u4fee\u6539\u9a6c\u4e0a\u88ab\u5176\u4ed6\u7ebf\u7a0b\u89c2\u6d4b\u5230\u201c\u3002<\/p>\n\n\n\n
\u7136\u800c\u8fd9\u65f6\u9519\u8bef\u7684\u3002\u770bms docs\uff0chttps:\/\/docs.microsoft.com\/en-us\/dotnet\/csharp\/language-reference\/keywords\/volatile<\/a>\uff0c\u91cc\u9762\u6709\u8fd9\u6837\u4e00\u6bb5\u8bdd\uff1a<\/p>\n\n\n\n
When writing to a field marked volatile<\/code>, the volatile<\/code> keyword controls the order in which writes are performed. It does not guarantee that these writes are immediately visible to other threads.<\/p><\/blockquote><\/figure>\n\n\n\n
\u7279\u522b\u5f3a\u8c03\u4e86volatile\u5e76\u4e0d\u80fd\u8ba9\u5bf9\u53d8\u91cf\u7684\u5199\u9a6c\u4e0a\u8ba9\u5176\u4ed6\u7ebf\u7a0b\u770b\u5230\u3002<\/p>\n\n\n\n
c#\u4e2d\u57fa\u672c\u7684\u540c\u6b65\u673a\u5236\u5c31volatile\uff0cInterlocked\uff0c\u8fd8\u6709\u5c31\u662flock\u4e86\u3002interlocked\u884c\u4e0d\u884c\u6211\u6ca1\u6709\u5b9e\u9a8c\uff0c\u8c03\u8bd5\u4e2d\u6211\u76f4\u63a5\u5728timer_callback\u4e2d\u5c06if\u8bed\u53e5\u653e\u5728\u4e86lock(this)\u4e4b\u4e2d\uff0c\u540e\u6765\u5b9e\u9a8c\u591a\u6b21\u786e\u8ba4\u95ee\u9898\u786e\u5b9e\u89e3\u51b3\u4e86\u3002<\/p>\n\n\n\n
\u6211\u540e\u6765\u7ffbeffective modern cpp\uff0c\u4e2d\u95f4\u6709\u4e00\u8282\u4e5f\u662f\u4e13\u95e8\u5f3a\u8c03volatile\u548clock\u7684\u533a\u522b\u3002c++\u4e2dvolatile\u4e13\u7528\u4e8e\u7279\u79cd\u5185\u5b58\u7684\u8bfb\u5199\uff0c\u4e0e\u7ebf\u7a0b\u4e4b\u95f4\u7684\u540c\u6b65\u65e0\u5173\u3002<\/p>\n\n\n\n
\u901a\u8fc7\u8fd9\u6b21\u8c03\u8bd5\uff0c\u6211\u5bf9\u7ebf\u7a0b\u4e4b\u95f4\u7684\u540c\u6b65\u591a\u4e86\u4e00\u4e9b\u4e86\u89e3\u3002\u4ee5\u524d\u6211\u8ba4\u4e3alock\u90fd\u662f\u653e\u5728\u7531\u4e8e\u5bf9\u6570\u636e\u7ed3\u6784\u540c\u65f6\u8fdb\u884c\u8bfb\u5199\u800c\u4f1a\u5bf9\u6570\u636e\u9020\u6210\u7834\u574f\u7684\u5730\u65b9\u3002\u73b0\u5728\u770b\u6765\uff0cc#\u4e2dlock\u4f3c\u4e4e\u8fd8\u80fd\u5bf9\u53ef\u89c1\u6027\u505a\u51fa\u4fdd\u8bc1\u3002\u5982\u679c\u662fcpp\uff0c\u8fd9\u79cd\u8981\u8ba9\u6240\u6709\u7ebf\u7a0b\u9a6c\u4e0a\u89c2\u6d4b\u5230\u53d8\u5316\u7684\u53d8\u91cf\uff0c\u4f3c\u4e4e\u7528\u539f\u5b50atomic<int>\u66f4\u597d\u3002\u4f46\u662fc#\u4f3c\u4e4e\u6ca1\u6709\u63d0\u4f9b\u8fd9\u79cd\u65b9\u4fbf\u7684\u539f\u5b50\u3002Interlocked\u7cfb\u5217\u51fd\u6570\u5728\u6211\u7684\u4f7f\u7528\u80cc\u666f\u4e0b\u4f3c\u4e4e\u6709\u4e9b\u9ebb\u70e6\uff0c\u6211\u6ca1\u628a\u63e1\u7528\u597d\uff0c\u5c31\u6ca1\u4f7f\u7528\u3002\u5728\u8fd9\u65b9\u9762c++\u66f4\u52a0\u65b9\u4fbf\u4e00\u4e9b\u3002<\/p>\n\n\n\n
\u5728stackoverflow\u4e0a\u67e5\u627e\u76f8\u5173\u95ee\u9898\u7684\u65f6\u5019\uff0c\u53d1\u73b0\u4e00\u7bc7\u6587\u7ae0\uff0c\u8be6\u7ec6\u8bb2\u8ff0\u4e86c\u8bed\u8a00\u4e2d\u7684volatile\u548cc#\u4e2dvolatile\u7684\u533a\u522b\uff1ahttps:\/\/ericlippert.com\/2011\/06\/16\/atomicity-volatility-and-immutability-are-different-part-three\/<\/a><\/p>\n\n\n\n
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