{"id":10008087,"date":"2023-07-13T10:59:10","date_gmt":"2023-07-13T02:59:10","guid":{"rendered":"https:\/\/ityet.com\/?p=10008087"},"modified":"2023-07-13T10:59:10","modified_gmt":"2023-07-13T02:59:10","slug":"%e4%b8%80%e6%96%87%e4%ba%86%e8%a7%a3io%e5%8c%85%e4%b8%ad%e7%9a%84discard%e7%b1%bb%e5%9e%8b","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10008087","title":{"rendered":"\u4e00\u6587\u4e86\u89e3io\u5305\u4e2d\u7684discard\u7c7b\u578b"},"content":{"rendered":"<h2>1. \u5f15\u8a00<\/h2>\n<p><code>io.discard<\/code>\u662fGo\u8bed\u8a00\u6807\u51c6\u5e93\u63d0\u4f9b\u4e00\u4e2a\u7ed3\u6784\u4f53\u7c7b\u578b\uff0c\u5176\u5728\u4e22\u5f03\u4e0d\u9700\u8981\u7684\u6570\u636e\u573a\u666f\u4e0b\u975e\u5e38\u597d\u7528\u3002\u672c\u6587\u6211\u4eec\u5c06\u4ece<code>io.discard<\/code> \u7c7b\u578b\u7684\u57fa\u672c\u5b9a\u4e49\u51fa\u53d1\uff0c\u8bb2\u8ff0\u5176\u57fa\u672c\u4f7f\u7528\u548c\u5b9e\u73b0\u539f\u7406\uff0c\u63a5\u7740\u7b80\u5355\u63cf\u8ff0 <code>io.discard<\/code> \u7684\u4f7f\u7528\u573a\u666f\uff0c\u57fa\u4e8e\u6b64\u5b8c\u6210\u5bf9 <code>io.discard<\/code> \u7c7b\u578b\u7684\u4ecb\u7ecd\u3002<\/p>\n<h2>2. \u4ecb\u7ecd<\/h2>\n<h4>2.1 \u57fa\u672c\u5b9a\u4e49<\/h4>\n<p><code>io.discard<\/code> \u662f Go\u8bed\u8a00\u63d0\u4f9b\u7684\u4e00\u4e2a<code>Writer<\/code>\uff0c\u8fd9\u4e2a<code>Writer<\/code> \u6bd4\u8f83\u7279\u6b8a\uff0c\u5176\u4e0d\u4f1a\u505a\u4efb\u4f55\u4e8b\u60c5\u3002\u5b83\u4f1a\u5c06\u5199\u5165\u7684\u6570\u636e<strong>\u7acb\u5373\u4e22\u5f03<\/strong>\uff0c\u4e0d\u4f1a\u505a\u4efb\u4f55\u5904\u7406\u3002\u5176\u5b9a\u4e49\u5982\u4e0b:<\/p>\n<pre><code class=\"go\">type discard struct{}\nfunc (discard) Write(p []byte) (int, error) {}\nfunc (discard) WriteString(s string) (int, error) {}\nfunc (discard) ReadFrom(r Reader) (n int64, err error) {}<\/code><\/pre>\n<p><code>discard<\/code> \u7ed3\u6784\u4f53\u7c7b\u578b\u6ca1\u6709\u5b9a\u4e49\u4efb\u4f55\u5b57\u6bb5\uff0c\u540c\u65f6\u8fd8\u63d0\u4f9b\u4e86<code>Write<\/code> ,<code>ReadFrom<\/code>\u548c<code>WriteString<\/code> \u65b9\u6cd5\uff0c<code>Write<\/code> \u65b9\u6cd5\u548c<code>WriteString<\/code> \u65b9\u6cd5\u5206\u522b\u63a5\u6536\u5b57\u8282\u5207\u7247\u548c\u5b57\u7b26\u4e32\uff0c\u7136\u540e\u8fd4\u56de\u5199\u5165\u7684\u5b57\u8282\u6570\u3002<\/p>\n<p>\u540c\u65f6\u8fd8\u5b9e\u73b0\u4e86<code>io.ReaderFrom<\/code> \u63a5\u53e3\uff0c\u8fd9\u4e2a\u662f\u4e3a\u4e86\u5728\u4f7f\u7528 <code>io.Copy<\/code> \u51fd\u6570\u65f6\uff0c\u5c06\u6570\u636e\u4ece\u6e90\u590d\u5236\u5230<code>io.discard<\/code> \u65f6\uff0c\u907f\u514d\u4e0d\u5fc5\u8981\u7684\u64cd\u4f5c\u3002<\/p>\n<p>\u4ece\u4e0a\u9762<code>discard<\/code> \u7684\u5b9a\u4e49\u53ef\u4ee5\u770b\u8d77\u6765\uff0c\u5176\u4e0d\u662f\u4e00\u4e2a\u516c\u5f00\u7c7b\u578b\u7684\u7ed3\u6784\u4f53\u7c7b\u578b\uff0c\u6240\u4ee5\u6211\u4eec\u5e76\u4e0d\u80fd\u521b\u5efa\u7ed3\u6784\u4f53\u5b9e\u4f8b\u3002\u4e8b\u5b9e\u4e0aGo\u8bed\u8a00\u63d0\u4f9b\u4e86\u4e00\u4e2a<code>io.discard<\/code> \u5b9e\u4f8b\u7684\u9884\u5b9a\u4e49\u5e38\u91cf\uff0c\u6211\u4eec\u76f4\u63a5\u4f7f\u7528\uff0c\u65e0\u9700\u81ea\u5df1\u521b\u5efa\u5b9e\u4f8b\uff0c\u5b9a\u4e49\u5982\u4e0b:<\/p>\n<pre><code class=\"go\">var Discard Writer = discard{}<\/code><\/pre>\n<h4>\u00a0\u00a02.2 \u4f7f\u7528\u8bf4\u660e<\/h4>\n<p>\u4e0b\u9762\u901a\u8fc7\u4e00\u4e2a\u4e22\u5f03\u7f51\u7edc\u8fde\u63a5\u4e2d\u4e0d\u518d\u9700\u8981\u7684\u6570\u636e\u7684\u4f8b\u5b50\uff0c\u6765\u5c55\u793a<code>io.Discard<\/code> \u7684\u4f7f\u7528\uff0c\u4ee3\u7801\u793a\u4f8b\u5982\u4e0b:<\/p>\n<pre><code class=\"go\">package main\n\nimport (\n        &quot;fmt&quot;\n        &quot;io&quot;\n        &quot;net&quot;\n        &quot;os&quot;\n)\n\nfunc discardData(conn net.Conn, bytesToDiscard int64) error {\n        _, err := io.CopyN(io.Discard, conn, bytesToDiscard)\n        return err\n}\n\nfunc main() {\n        conn, err := net.Dial(&quot;tcp&quot;, &quot;example.com:80&quot;)\n        if err != nil {\n                fmt.Println(&quot;\u8fde\u63a5\u9519\u8bef:&quot;, err)\n                return\n        }\n        defer conn.Close()\n\n        bytesToDiscard := int64(1024) \/\/ \u8981\u4e22\u5f03\u7684\u5b57\u8282\u6570\n\n        err = discardData(conn, bytesToDiscard)\n        if err != nil {\n                fmt.Println(&quot;\u4e22\u5f03\u6570\u636e\u9519\u8bef:&quot;, err)\n                return\n        }\n\n        fmt.Println(&quot;\u6570\u636e\u5df2\u6210\u529f\u4e22\u5f03\u3002&quot;)\n}<\/code><\/pre>\n<p>\u5728\u4e0a\u9762\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5efa\u7acb\u4e86\u7f51\u7edc\u8fde\u63a5\uff0c\u7136\u540e\u8fde\u63a5\u4e2d\u7684\u524d1024\u4e2a\u5b57\u8282\u7684\u6570\u636e\u662f\u4e0d\u9700\u8981\u7684\u3002\u8fd9\u4e2a\u65f6\u5019\uff0c\u6211\u4eec\u901a\u8fc7<code>io.CopyN<\/code> \u51fd\u6570\u5c06\u6570\u636e\u4ece<code>conn<\/code> \u62f7\u8d1d\u5230<code>io.Discard<\/code> \u5f53\u4e2d\uff0c\u57fa\u4e8e<code>io.Discard<\/code> \u4e22\u5f03\u6570\u636e\u7684\u7279\u6027\uff0c\u6210\u529f\u5c06\u8fde\u63a5\u7684\u524d1024\u4e2a\u5b57\u8282\u4e22\u5f03\u6389\uff0c\u800c\u4e0d\u9700\u8981\u81ea\u5b9a\u4e49\u7f13\u51b2\u533a\u4e4b\u7c7b\u7684\u64cd\u4f5c\uff0c\u7b80\u5355\u9ad8\u6548\u3002<\/p>\n<h2>3. \u5b9e\u73b0\u539f\u7406<\/h2>\n<p><code>io.Discard<\/code>\u7684\u76ee\u7684\u662f\u5728\u67d0\u4e9b\u573a\u666f\u4e0b\u63d0\u4f9b\u4e00\u4e2a\u6ee1\u8db3<code>io.Writer<\/code>\u63a5\u53e3\u7684\u5b9e\u4f8b\uff0c\u4f46\u7528\u6237\u5bf9\u4e8e\u6570\u636e\u7684\u5199\u5165\u64cd\u4f5c\u5e76\u4e0d\u5173\u5fc3\u3002\u5b83\u53ef\u4ee5\u88ab\u7528\u4f5c\u4e00\u4e2a\u9ed1\u6d1e\u822c\u7684\u5199\u5165\u76ee\u6807\uff0c\u9ed8\u9ed8\u5730\u4e22\u5f03\u6240\u6709\u5199\u5165\u5b83\u7684\u6570\u636e\u3002\u6240\u4ee5<code>io.discard<\/code> \u7684\u5b9e\u73b0\u4e5f\u76f8\u5bf9\u6bd4\u8f83\u7b80\u5355\uff0c\u4e0d\u5bf9\u8f93\u5165\u7684\u6570\u636e\u8fdb\u884c\u4efb\u4f55\u5904\u7406\u5373\u53ef\uff0c\u4e0b\u9762\u6211\u4eec\u6765\u770b\u5177\u4f53\u7684\u5b9e\u73b0\u3002<\/p>\n<p>\u9996\u5148\u662f<code>io.discard<\/code> \u7ed3\u6784\u4f53\u7684\u5b9a\u4e49\uff0c\u6ca1\u6709\u5b9a\u4e49\u4efb\u4f55\u5b57\u6bb5\uff0c\u56e0\u4e3a\u672c\u6765\u4e5f\u4e0d\u9700\u8981\u6267\u884c\u4efb\u4f55\u5199\u5165\u64cd\u4f5c:<\/p>\n<pre><code class=\"go\">type discard struct{}<\/code><\/pre>\n<p>\u800c\u5bf9\u4e8e<code>Write<\/code> \u548c <code>WriteString<\/code> \u65b9\u6cd5\uff0c\u5176\u76f4\u63a5\u8fd4\u56de\u4e86\u4f20\u5165\u53c2\u6570\u7684\u957f\u5ea6\uff0c\u5f80\u8be5<code>Writer<\/code> \u5199\u5165\u7684\u6570\u636e\u4e0d\u4f1a\u88ab\u5199\u5165\u5230\u5176\u4ed6\u5730\u65b9\uff0c\u800c\u662f\u88ab\u76f4\u63a5\u4e22\u5f03:<\/p>\n<pre><code class=\"go\">func (discard) Write(p []byte) (int, error) {\n   return len(p), nil\n}\n\nfunc (discard) WriteString(s string) (int, error) {\n   return len(s), nil\n}<\/code><\/pre>\n<p>\u540c\u65f6<code>discard<\/code> \u4e5f\u5b9e\u73b0\u4e86<code>io.ReaderFrom<\/code> \u63a5\u53e3\uff0c\u5b9e\u73b0\u4e86<code>ReadFrom<\/code> \u65b9\u6cd5\uff0c\u5b9e\u73b0\u4e5f\u662f\u975e\u5e38\u7b80\u5355\uff0c\u4ece<code>blackHolePool<\/code> \u7f13\u51b2\u6c60\u4e2d\u83b7\u53d6\u5b57\u8282\u5207\u7247\uff0c\u7136\u540e\u4e0d\u65ad\u8bfb\u53d6\u6570\u636e\uff0c\u8bfb\u53d6\u5b8c\u6210\u4e4b\u540e\uff0c\u518d\u5c06\u5b57\u8282\u5207\u7247\u91cd\u65b0\u653e\u5165\u7f13\u51b2\u6c60\u5f53\u4e2d:<\/p>\n<pre><code class=\"go\">\/\/ \u5b58\u5728\u4e00\u4e2a\u5b57\u8282\u5207\u7247\u7f13\u51b2\u6c60\nvar blackHolePool = sync.Pool{\n   New: func() any {\n      b := make([]byte, 8192)\n      return &amp;b\n   },\n}\n\nfunc (discard) ReadFrom(r Reader) (n int64, err error) {\n   \/\/ \u4ece\u7f13\u51b2\u6c60\u4e2d\u53d6\u51fa\u4e00\u4e2a \u5b57\u8282\u5207\u7247\n   bufp := blackHolePool.Get().(*[]byte)\n   readSize := 0\n   for {\n      \/\/ \u4e0d\u65ad\u8bfb\u53d6\u6570\u636e\uff0cbufp \u53ea\u662f\u4f5c\u4e3a\u4e00\u4e2a\u8bfb\u53d6\u6570\u636e\u7684\u4e2d\u4ecb\uff0c\u8bfb\u53d6\u5230\u7684\u6570\u636e\u5e76\u65e0\u610f\u4e49\n      readSize, err = r.Read(*bufp)\n      n += int64(readSize)\n      if err != nil {\n         \/\/ \u5c06\u5b57\u8282\u5207\u7247 \u91cd\u65b0\u653e\u5165\u5230 blackHolePool \u5f53\u4e2d\n         blackHolePool.Put(bufp)\n         if err == EOF {\n            return n, nil\n         }\n         return\n      }\n   }\n}<\/code><\/pre>\n<p>\u5728<code>io.Copy<\/code> \u51fd\u6570\u4e2d\uff0c\u5c06\u8c03\u7528<code>discard<\/code> \u4e2d\u7684<code>ReadFrom<\/code> \u65b9\u6cd5\uff0c\u80fd\u591f\u5c06<code>Writer<\/code>\u4e2d\u7684\u6240\u6709\u6570\u636e\u8bfb\u53d6\u5b8c\uff0c\u7136\u540e\u4e22\u5f03\u6389\u3002<\/p>\n<h2>4. \u4f7f\u7528\u573a\u666f<\/h2>\n<p><code>io.Discard<\/code> \u7ed9\u6211\u4eec\u63d0\u4f9b\u4e86\u4e00\u4e2a<code>io.Writer<\/code> \u63a5\u53e3\u7684\u5b9e\u4f8b\uff0c\u540c\u65f6\u5176\u53c8\u4e0d\u4f1a\u771f\u5b9e\u5f97\u5199\u5165\u6570\u636e\uff0c\u8fd9\u4e2a\u5728\u67d0\u4e9b\u573a\u666f\u4e0b\u975e\u5e38\u6709\u7528\u3002<\/p>\n<p>\u6709\u65f6\u5019\uff0c\u6211\u4eec\u53ef\u80fd\u9700\u8981\u4e00\u4e2a\u5b9e\u73b0<code>io.Writer<\/code> \u63a5\u53e3\u7684\u5b9e\u4f8b\uff0c\u4f46\u662f\u6211\u4eec\u5e76\u4e0d\u5173\u5fc3\u6570\u636e\u5199\u5165<code>Writer<\/code> \u7684\u7ed3\u679c\uff0c\u4e5f\u4e0d\u5173\u5fc3\u6570\u636e\u662f\u5426\u5199\u5230\u4e86\u54ea\u4e2a\u5730\u65b9\uff0c\u6b64\u65f6<code>io.Discard<\/code> \u5c31\u7ed9\u6211\u4eec\u63d0\u4f9b\u4e86\u4e00\u4e2a\u65b9\u4fbf\u7684\u89e3\u51b3\u65b9\u6848\u3002\u540c\u65f6<code>io.Discard<\/code> \u53ef\u4ee5\u4f5c\u4e3a\u4e00\u4e2a\u9ed1\u6d1e\u5199\u5165\u76ee\u6807\uff0c\u80fd\u591f\u5c06\u6570\u636e\u9ed8\u9ed8\u4e22\u5f03\u6389\uff0c\u4e0d\u4f1a\u8fdb\u884c\u5b9e\u9645\u7684\u5904\u7406\u548c\u5b58\u50a8\u3002<\/p>\n<p>\u6240\u4ee5\u5982\u679c\u6211\u4eec\u60f3\u8981\u4e22\u5f03\u67d0\u4e9b\u6570\u636e\uff0c\u4ea6\u6216\u8005\u662f\u9700\u8981\u4e00\u4e2a<code>io.Writer<\/code>\u63a5\u53e3\u7684\u5b9e\u4f8b\uff0c\u4f46\u662f\u5bf9\u4e8e\u5199\u5165\u7ed3\u679c\u4e0d\u9700\u8981\u5173\u6ce8\u65f6\uff0c\u6b64\u65f6\u4f7f\u7528<code>io.Discard<\/code> \u662f\u975e\u5e38\u5408\u9002\u7684\u3002<\/p>\n<h2>5. \u603b\u7ed3<\/h2>\n<p><code>io.discard<\/code> \u51fd\u6570\u662fGo\u8bed\u8a00\u6807\u51c6\u5e93\u4e2d\u4e00\u4e2a\u5b9e\u73b0\u4e86<code>Writer<\/code>\u63a5\u53e3\u7684\u7ed3\u6784\u4f53\u7c7b\u578b\uff0c\u80fd\u591f\u6084\u65e0\u58f0\u606f\u5f97\u5b9e\u73b0\u6570\u636e\u7684\u4e22\u5f03\u3002 \u6211\u4eec\u5148\u4ece<code>io.discard<\/code> \u7c7b\u578b\u7684\u57fa\u672c\u5b9a\u4e49\u51fa\u53d1\uff0c\u4e4b\u540e\u901a\u8fc7\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u5c55\u793a\u5982\u4f55\u4f7f\u7528<code>io.discard<\/code> \u7c7b\u578b\u5b9e\u73b0\u5bf9\u4e0d\u9700\u8981\u6570\u636e\u7684\u4e22\u5f03\u3002<\/p>\n<p>\u63a5\u7740\u6211\u4eec\u8bb2\u8ff0\u4e86<code>io.discard<\/code> \u7c7b\u578b\u7684\u5b9e\u73b0\u539f\u7406\uff0c\u5176\u5b9e\u5c31\u662f\u4e0d\u5bf9\u5199\u5165\u7684\u6570\u636e\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002\u5728\u4f7f\u7528\u573a\u666f\u4e0b\uff0c\u6211\u4eec\u60f3\u8981\u4e22\u5f03\u67d0\u4e9b\u6570\u636e\uff0c\u4ea6\u6216\u8005\u662f\u9700\u8981\u4e00\u4e2a<code>io.Writer<\/code>\u63a5\u53e3\u7684\u5b9e\u4f8b\uff0c\u4f46\u662f\u5bf9\u4e8e\u5199\u5165\u7ed3\u679c\u4e0d\u9700\u8981\u5173\u6ce8\u65f6\uff0c\u6b64\u65f6\u4f7f\u7528<code>io.Discard<\/code> \u662f\u975e\u5e38\u5408\u9002\u7684\u3002<\/p>\n<p>\u57fa\u4e8e\u6b64\uff0c\u4fbf\u5b8c\u6210\u4e86\u5bf9<code>io.discard<\/code> \u7c7b\u578b\u7684\u4ecb\u7ecd\uff0c\u5e0c\u671b\u5bf9\u4f60\u6709\u6240\u5e2e\u52a9\u3002<\/p>\n<p><a href=\"https:\/\/segmentfault.com\/a\/1190000044004036\">https:\/\/segmentfault.com\/a\/1190000044004036<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>1. \u5f15\u8a00 io.discard\u662fGo\u8bed\u8a00\u6807\u51c6\u5e93\u63d0\u4f9b\u4e00\u4e2a\u7ed3\u6784\u4f53\u7c7b\u578b\uff0c\u5176\u5728\u4e22\u5f03\u4e0d\u9700\u8981\u7684\u6570\u636e\u573a\u666f\u4e0b\u975e\u5e38\u597d\u7528\u3002\u672c\u6587\u6211 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-10008087","post","type-post","status-publish","format-standard","hentry","category-share"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10008087","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10008087"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10008087\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10008087"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10008087"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10008087"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}