Why does the template package not have a function taking io.Reader?

<p>Since io.Reader is the idiomatic way for reading in data in Go. Does anyone know why text/template does not have a function taking in io.Reader? I know it is fairly simple to create a wrapper, I just find it odd that it&#39;s not there.</p> <hr/>**评论：**<br/><br/>kylewolfe: <pre><p>Think about why io.Reader is used in most cases, and not just because it&#39;s idiomatic. The json package for example, does not need to read the entire byte slice in to memory in order to parse it. It utilizes a tokenizer. This means that io.Reader is acting like a pointer to the original slice of bytes, preventing unnecessary memory usage.</p> <p>text/template however, needs an entire copy of the byte slice in order to do it&#39;s parsing. If it were to provide io.Reader in the API, it would have to essentially do an io.ReadAll() before continuing almost guaranteeing extra work / memory utilization (origBytes-&gt;io.Reader-&gt;copyBytes-&gt;Parse rather than origBytes-&gt;Parse)</p></pre>thorhs: <pre><p>True, but what if you are reading from a network resource? Or a compressed file, or any number of other readers?</p> <p>I can&#39;t believe the ParseFile does anything different than read from a reader internally, but I have not looked at the source though. </p></pre>kylewolfe: <pre><blockquote> <p>I can&#39;t believe the ParseFile does anything different than read from a reader internally</p> </blockquote> <p>Don&#39;t be afraid to have a look. ParseFile is simply a wrapper, but in the end it still winds up here: <a href="https://github.com/golang/go/blob/master/src/text/template/parse/parse.go" rel="nofollow">https://github.com/golang/go/blob/master/src/text/template/parse/parse.go</a></p></pre>lstokeworth: <pre><p>I wonder why the argument to <a href="https://godoc.org/text/template#Template.Parse" rel="nofollow">Parse</a> is string and not []byte.</p></pre>4ad: <pre><p>Because this makes it really easy to write templates in your Go source code.</p></pre>dominikh: <pre><p>Because templates aren&#39;t data, they&#39;re text. It&#39;s really the same reason why you use a string in <code>fmt.Println(&#34;Hello, world&#34;)</code>.</p> <p>Templates are usually hard-coded or generated from specific building blocks. They&#39;re not usually data that is read from some external source (with the exception of files; but you consider a Go source file text and not data, too. Same goes for templates.)</p></pre>zeroZshadow: <pre><p>I&#39;m guessing because text could be in utf8, and be 2 bytes per character. Making it a string means that the parser does not have to deal with the conversion.</p></pre>lstokeworth: <pre><p>The parser assumes UTF-8 encoding for strings and I would assume that it would do the same for []byte.</p></pre>