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281 lines
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281 lines
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<div class="container">
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<h1 id="pkg-overview">package bufio</h1>
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<p><code>import "bufio"</code>
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</p><p>bufio包实现了有缓冲的I/O。它包装一个io.Reader或io.Writer接口对象，创建另一个也实现了该接口，且同时还提供了缓冲和一些文本I/O的帮助函数的对象。</p>
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<h2 id="pkg-constants">Constants </h2>
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<pre>const (
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<span class="com">// 用于缓冲一个token，实际需要的最大token尺寸可能小一些，例如缓冲中需要保存一整行内容</span><span class="com"></span>
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<span id="MaxScanTokenSize">MaxScanTokenSize</span> = 64 * 1024
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)</pre>
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<h2 id="pkg-variables">Variables </h2>
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<pre>var (
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<span id="ErrInvalidUnreadByte">ErrInvalidUnreadByte</span> = <a href="errors.htm">errors</a>.<a href="errors.htm#New">New</a>("bufio: invalid use of UnreadByte")
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<span id="ErrInvalidUnreadRune">ErrInvalidUnreadRune</span> = <a href="errors.htm">errors</a>.<a href="errors.htm#New">New</a>("bufio: invalid use of UnreadRune")
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<span id="ErrBufferFull">ErrBufferFull</span> = <a href="errors.htm">errors</a>.<a href="errors.htm#New">New</a>("bufio: buffer full")
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<span id="ErrNegativeCount">ErrNegativeCount</span> = <a href="errors.htm">errors</a>.<a href="errors.htm#New">New</a>("bufio: negative count")
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)</pre>
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<pre>var (
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<span id="ErrTooLong">ErrTooLong</span> = <a href="errors.htm">errors</a>.<a href="errors.htm#New">New</a>("bufio.Scanner: token too long")
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<span id="ErrNegativeAdvance">ErrNegativeAdvance</span> = <a href="errors.htm">errors</a>.<a href="errors.htm#New">New</a>("bufio.Scanner: SplitFunc returns negative advance count")
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<span id="ErrAdvanceTooFar">ErrAdvanceTooFar</span> = <a href="errors.htm">errors</a>.<a href="errors.htm#New">New</a>("bufio.Scanner: SplitFunc returns advance count beyond input")
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)</pre>
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<p>会被Scanner类型返回的错误。</p>
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<h2 id="Reader">type <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#31" title="View Source">Reader</a> </h2>
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<pre>type Reader struct {
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<span class="com">// 内含隐藏或非导出字段</span>
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}</pre>
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<p>Reader实现了给一个io.Reader接口对象附加缓冲。</p>
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<h3 id="NewReader">func <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#61" title="View Source">NewReader</a> </h3>
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<pre class="funcdecl">func NewReader(rd <a href="io.htm">io</a>.<a href="io.htm#Reader">Reader</a>) *<a href="#Reader">Reader</a></pre>
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<p>NewReader创建一个具有默认大小缓冲、从r读取的*Reader。</p>
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<h3 id="NewReaderSize">func <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#46" title="View Source">NewReaderSize</a> </h3>
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<pre class="funcdecl">func NewReaderSize(rd <a href="io.htm">io</a>.<a href="io.htm#Reader">Reader</a>, size <a href="builtin.htm#int">int</a>) *<a href="#Reader">Reader</a></pre>
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<p>NewReaderSize创建一个具有最少有size尺寸的缓冲、从r读取的*Reader。如果参数r已经是一个具有足够大缓冲的* Reader类型值，会返回r。</p>
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<h3 id="Reader.Reset">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#67" title="View Source">Reset</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) Reset(r <a href="io.htm">io</a>.<a href="io.htm#Reader">Reader</a>)</pre>
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<p>Reset丢弃缓冲中的数据，清除任何错误，将b重设为其下层从r读取数据。</p>
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<h3 id="Reader.Buffered">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#261" title="View Source">Buffered</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) Buffered() <a href="builtin.htm#int">int</a></pre>
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<p>Buffered返回缓冲中现有的可读取的字节数。</p>
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<h3 id="Reader.Peek">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#123" title="View Source">Peek</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) Peek(n <a href="builtin.htm#int">int</a>) ([]<a href="builtin.htm#byte">byte</a>, <a href="builtin.htm#error">error</a>)</pre>
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<p>Peek返回输入流的下n个字节，而不会移动读取位置。返回的[]byte只在下一次调用读取操作前合法。如果Peek返回的切片长度比n小，它也会返会一个错误说明原因。如果n比缓冲尺寸还大，返回的错误将是ErrBufferFull。</p>
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<h3 id="Reader.Read">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#153" title="View Source">Read</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) Read(p []<a href="builtin.htm#byte">byte</a>) (n <a href="builtin.htm#int">int</a>, err <a href="builtin.htm#error">error</a>)</pre>
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<p>Read读取数据写入p。本方法返回写入p的字节数。本方法一次调用最多会调用下层Reader接口一次Read方法，因此返回值n可能小于len(p)。读取到达结尾时，返回值n将为0而err将为io.EOF。</p>
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<h3 id="Reader.ReadByte">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#193" title="View Source">ReadByte</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) ReadByte() (c <a href="builtin.htm#byte">byte</a>, err <a href="builtin.htm#error">error</a>)</pre>
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<p>ReadByte读取并返回一个字节。如果没有可用的数据，会返回错误。</p>
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<h3 id="Reader.UnreadByte">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#208" title="View Source">UnreadByte</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) UnreadByte() <a href="builtin.htm#error">error</a></pre>
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<p>UnreadByte吐出最近一次读取操作读取的最后一个字节。（只能吐出最后一个，多次调用会出问题）</p>
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<h3 id="Reader.ReadRune">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#228" title="View Source">ReadRune</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) ReadRune() (r <a href="builtin.htm#rune">rune</a>, size <a href="builtin.htm#int">int</a>, err <a href="builtin.htm#error">error</a>)</pre>
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<p>ReadRune读取一个utf-8编码的unicode码值，返回该码值、其编码长度和可能的错误。如果utf-8编码非法，读取位置只移动1字节，返回U+FFFD，返回值size为1而err为nil。如果没有可用的数据，会返回错误。</p>
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<h3 id="Reader.UnreadRune">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#250" title="View Source">UnreadRune</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) UnreadRune() <a href="builtin.htm#error">error</a></pre>
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<p>UnreadRune吐出最近一次ReadRune调用读取的unicode码值。如果最近一次读取不是调用的ReadRune，会返回错误。（从这点看，UnreadRune比UnreadByte严格很多）</p>
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<h3 id="Reader.ReadLine">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#325" title="View Source">ReadLine</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) ReadLine() (line []<a href="builtin.htm#byte">byte</a>, isPrefix <a href="builtin.htm#bool">bool</a>, err <a href="builtin.htm#error">error</a>)</pre>
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<p align="left">ReadLine是一个低水平的行数据读取原语。大多数调用者应使用ReadBytes('\n')或ReadString('\n')代替，或者使用Scanner。</p>
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<p align="left">ReadLine尝试返回一行数据，不包括行尾标志的字节。如果行太长超过了缓冲，返回值isPrefix会被设为true，并返回行的前面一部分。该行剩下的部分将在之后的调用中返回。返回值isPrefix会在返回该行最后一个片段时才设为false。返回切片是缓冲的子切片，只在下一次读取操作之前有效。ReadLine要么返回一个非nil的line，要么返回一个非nil的err，两个返回值至少一个非nil。</p>
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<p align="left">返回的文本不包含行尾的标志字节（"\r\n"或"\n"）。如果输入流结束时没有行尾标志字节，方法不会出错，也不会指出这一情况。在调用ReadLine之后调用UnreadByte会总是吐出最后一个读取的字节（很可能是该行的行尾标志字节），即使该字节不是ReadLine返回值的一部分。</p>
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<h3 id="Reader.ReadSlice">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#273" title="View Source">ReadSlice</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) ReadSlice(delim <a href="builtin.htm#byte">byte</a>) (line []<a href="builtin.htm#byte">byte</a>, err <a href="builtin.htm#error">error</a>)</pre>
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<p>ReadSlice读取直到第一次遇到delim字节，返回缓冲里的包含已读取的数据和delim字节的切片。该返回值只在下一次读取操作之前合法。如果ReadSlice放在在读取到delim之前遇到了错误，它会返回在错误之前读取的数据在缓冲中的切片以及该错误（一般是io.EOF）。如果在读取到delim之前缓冲就被写满了，ReadSlice失败并返回ErrBufferFull。因为ReadSlice的返回值会被下一次I/O操作重写，调用者应尽量使用ReadBytes或ReadString替代本法功法。当且仅当ReadBytes方法返回的切片不以delim结尾时，会返回一个非nil的错误。</p>
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<h3 id="Reader.ReadBytes">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#367" title="View Source">ReadBytes</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) ReadBytes(delim <a href="builtin.htm#byte">byte</a>) (line []<a href="builtin.htm#byte">byte</a>, err <a href="builtin.htm#error">error</a>)</pre>
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<p>ReadBytes读取直到第一次遇到delim字节，返回一个包含已读取的数据和delim字节的切片。如果ReadBytes方法在读取到delim之前遇到了错误，它会返回在错误之前读取的数据以及该错误（一般是io.EOF）。当且仅当ReadBytes方法返回的切片不以delim结尾时，会返回一个非nil的错误。</p>
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<h3 id="Reader.ReadString">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#415" title="View Source">ReadString</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) ReadString(delim <a href="builtin.htm#byte">byte</a>) (line <a href="builtin.htm#string">string</a>, err <a href="builtin.htm#error">error</a>)</pre>
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<p>ReadString读取直到第一次遇到delim字节，返回一个包含已读取的数据和delim字节的字符串。如果ReadString方法在读取到delim之前遇到了错误，它会返回在错误之前读取的数据以及该错误（一般是io.EOF）。当且仅当ReadString方法返回的切片不以delim结尾时，会返回一个非nil的错误。</p>
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<h3 id="Reader.WriteTo">func (*Reader) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#422" title="View Source">WriteTo</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Reader">Reader</a>) WriteTo(w <a href="io.htm">io</a>.<a href="io.htm#Writer">Writer</a>) (n <a href="builtin.htm#int64">int64</a>, err <a href="builtin.htm#error">error</a>)</pre>
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<p>WriteTo方法实现了io.WriterTo接口。</p>
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<h2 id="Writer">type <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#479" title="View Source">Writer</a> </h2>
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<pre>type Writer struct {
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<span class="com">// 内含隐藏或非导出字段</span>
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}</pre>
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<p>Writer实现了为io.Writer接口对象提供缓冲。如果在向一个Writer类型值写入时遇到了错误，该对象将不再接受任何数据，且所有写操作都会返回该错误。在说有数据都写入后，调用者有义务调用Flush方法以保证所有的数据都交给了下层的io.Writer。</p>
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<div class="panel-group">
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<div class="panel panel-default" id="example-Writer">
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<div class="panel-heading" onclick="document.getElementById('ex-Writer').style.display = document.getElementById('ex-Writer').style.display=='none'?'block':'none';">Example</div>
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<div class="panel-collapse collapse" id="ex-Writer">
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<div class="panel-body">
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<pre>w := bufio.NewWriter(os.Stdout)
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fmt.Fprint(w, "Hello, ")
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fmt.Fprint(w, "world!")
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w.Flush() <span class="com">// Don't forget to flush!</span></pre>
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<p>Output:
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</p><pre>Hello, world!
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</pre>
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</div>
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</div>
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</div>
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</div>
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<h3 id="NewWriter">func <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#505" title="View Source">NewWriter</a> </h3>
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<pre class="funcdecl">func NewWriter(w <a href="io.htm">io</a>.<a href="io.htm#Writer">Writer</a>) *<a href="#Writer">Writer</a></pre>
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<p>NewWriter创建一个具有默认大小缓冲、写入w的*Writer。</p>
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<h3 id="NewWriterSize">func <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#489" title="View Source">NewWriterSize</a> </h3>
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<pre class="funcdecl">func NewWriterSize(w <a href="io.htm">io</a>.<a href="io.htm#Writer">Writer</a>, size <a href="builtin.htm#int">int</a>) *<a href="#Writer">Writer</a></pre>
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<p>NewWriterSize创建一个具有最少有size尺寸的缓冲、写入w的*Writer。如果参数w已经是一个具有足够大缓冲的*Writer类型值，会返回w。</p>
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<h3 id="Writer.Reset">func (*Writer) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#511" title="View Source">Reset</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Writer">Writer</a>) Reset(w <a href="io.htm">io</a>.<a href="io.htm#Writer">Writer</a>)</pre>
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<p>Reset丢弃缓冲中的数据，清除任何错误，将b重设为将其输出写入w。</p>
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<h3 id="Writer.Buffered">func (*Writer) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#550" title="View Source">Buffered</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Writer">Writer</a>) Buffered() <a href="builtin.htm#int">int</a></pre>
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<p>Buffered返回缓冲中已使用的字节数。</p>
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<h3 id="Writer.Available">func (*Writer) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#547" title="View Source">Available</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Writer">Writer</a>) Available() <a href="builtin.htm#int">int</a></pre>
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<p>Available返回缓冲中还有多少字节未使用。</p>
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<h3 id="Writer.Write">func (*Writer) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#556" title="View Source">Write</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Writer">Writer</a>) Write(p []<a href="builtin.htm#byte">byte</a>) (nn <a href="builtin.htm#int">int</a>, err <a href="builtin.htm#error">error</a>)</pre>
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<p>Write将p的内容写入缓冲。返回写入的字节数。如果返回值nn < len(p)，还会返回一个错误说明原因。</p>
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<h3 id="Writer.WriteString">func (*Writer) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#626" title="View Source">WriteString</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Writer">Writer</a>) WriteString(s <a href="builtin.htm#string">string</a>) (<a href="builtin.htm#int">int</a>, <a href="builtin.htm#error">error</a>)</pre>
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<p>WriteString写入一个字符串。返回写入的字节数。如果返回值nn < len(s)，还会返回一个错误说明原因。</p>
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<h3 id="Writer.WriteByte">func (*Writer) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#581" title="View Source">WriteByte</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Writer">Writer</a>) WriteByte(c <a href="builtin.htm#byte">byte</a>) <a href="builtin.htm#error">error</a></pre>
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<p>WriteByte写入单个字节。</p>
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<h3 id="Writer.WriteRune">func (*Writer) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#595" title="View Source">WriteRune</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Writer">Writer</a>) WriteRune(r <a href="builtin.htm#rune">rune</a>) (size <a href="builtin.htm#int">int</a>, err <a href="builtin.htm#error">error</a>)</pre>
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<p>WriteRune写入一个unicode码值（的utf-8编码），返回写入的字节数和可能的错误。</p>
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<h3 id="Writer.Flush">func (*Writer) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#518" title="View Source">Flush</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Writer">Writer</a>) Flush() <a href="builtin.htm#error">error</a></pre>
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<p>Flush方法将缓冲中的数据写入下层的io.Writer接口。</p>
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<h3 id="Writer.ReadFrom">func (*Writer) <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#645" title="View Source">ReadFrom</a> </h3>
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<pre class="funcdecl">func (b *<a href="#Writer">Writer</a>) ReadFrom(r <a href="io.htm">io</a>.<a href="io.htm#Reader">Reader</a>) (n <a href="builtin.htm#int64">int64</a>, err <a href="builtin.htm#error">error</a>)</pre>
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<p>ReadFrom实现了io.ReaderFrom接口。</p>
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<h2 id="ReadWriter">type <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#690" title="View Source">ReadWriter</a> </h2>
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<pre>type ReadWriter struct {
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*<a href="#Reader">Reader</a>
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*<a href="#Writer">Writer</a>
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}</pre>
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<p>ReadWriter类型保管了指向Reader和Writer类型的指针，（因此）实现了io.ReadWriter接口。</p>
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<h3 id="NewReadWriter">func <a href="https://github.com/golang/go/blob/master/src/bufio/bufio.go?name=release#696" title="View Source">NewReadWriter</a> </h3>
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<pre class="funcdecl">func NewReadWriter(r *<a href="#Reader">Reader</a>, w *<a href="#Writer">Writer</a>) *<a href="#ReadWriter">ReadWriter</a></pre>
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<p>NewReadWriter申请创建一个新的、将读写操作分派给r和w 的ReadWriter。</p>
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<h2 id="SplitFunc">type <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#57" title="View Source">SplitFunc</a> </h2>
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<pre>type SplitFunc func(data []<a href="builtin.htm#byte">byte</a>, atEOF <a href="builtin.htm#bool">bool</a>) (advance <a href="builtin.htm#int">int</a>, token []<a href="builtin.htm#byte">byte</a>, err <a href="builtin.htm#error">error</a>)</pre>
|
||
<p align="left">SplitFunc类型代表用于对输出作词法分析的分割函数。</p>
|
||
<p align="left">参数data是尚未处理的数据的一个开始部分的切片，参数atEOF表示是否Reader接口不能提供更多的数据。返回值是解析位置前进的字节数，将要返回给调用者的token切片，以及可能遇到的错误。如果数据不足以（保证）生成一个完整的token，例如需要一整行数据但data里没有换行符，SplitFunc可以返回(0, nil, nil)来告诉Scanner读取更多的数据写入切片然后用从同一位置起始、长度更长的切片再试一次（调用SplitFunc类型函数）。</p>
|
||
<p align="left">如果返回值err非nil，扫描将终止并将该错误返回给Scanner的调用者。</p>
|
||
<p align="left">除非atEOF为真，永远不会使用空切片data调用SplitFunc类型函数。然而，如果atEOF为真，data却可能是非空的、且包含着未处理的文本。</p>
|
||
<h2 id="ScanBytes">func <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#213" title="View Source">ScanBytes</a> </h2>
|
||
<pre class="funcdecl">func ScanBytes(data []<a href="builtin.htm#byte">byte</a>, atEOF <a href="builtin.htm#bool">bool</a>) (advance <a href="builtin.htm#int">int</a>, token []<a href="builtin.htm#byte">byte</a>, err <a href="builtin.htm#error">error</a>)</pre>
|
||
<p>ScanBytes是用于Scanner类型的分割函数（符合SplitFunc），本函数会将每个字节作为一个token返回。</p>
|
||
<h2 id="ScanRunes">func <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#228" title="View Source">ScanRunes</a> </h2>
|
||
<pre class="funcdecl">func ScanRunes(data []<a href="builtin.htm#byte">byte</a>, atEOF <a href="builtin.htm#bool">bool</a>) (advance <a href="builtin.htm#int">int</a>, token []<a href="builtin.htm#byte">byte</a>, err <a href="builtin.htm#error">error</a>)</pre>
|
||
<p>ScanRunes是用于Scanner类型的分割函数（符合SplitFunc），本函数会将每个utf-8编码的unicode码值作为一个token返回。本函数返回的rune序列和range一个字符串的输出rune序列相同。错误的utf-8编码会翻译为U+FFFD = "\xef\xbf\xbd"，但只会消耗一个字节。调用者无法区分正确编码的rune和错误编码的rune。</p>
|
||
<h2 id="ScanWords">func <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#319" title="View Source">ScanWords</a> </h2>
|
||
<pre class="funcdecl">func ScanWords(data []<a href="builtin.htm#byte">byte</a>, atEOF <a href="builtin.htm#bool">bool</a>) (advance <a href="builtin.htm#int">int</a>, token []<a href="builtin.htm#byte">byte</a>, err <a href="builtin.htm#error">error</a>)</pre>
|
||
<p>ScanRunes是用于Scanner类型的分割函数（符合SplitFunc），本函数会将空白（参见unicode.IsSpace）分隔的片段（去掉前后空白后）作为一个token返回。本函数永远不会返回空字符串。</p>
|
||
<h2 id="ScanLines">func <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#274" title="View Source">ScanLines</a> </h2>
|
||
<pre class="funcdecl">func ScanLines(data []<a href="builtin.htm#byte">byte</a>, atEOF <a href="builtin.htm#bool">bool</a>) (advance <a href="builtin.htm#int">int</a>, token []<a href="builtin.htm#byte">byte</a>, err <a href="builtin.htm#error">error</a>)</pre>
|
||
<p>ScanRunes是用于Scanner类型的分割函数（符合SplitFunc），本函数会将每一行文本去掉末尾的换行标记作为一个token返回。返回的行可以是空字符串。换行标记为一个可选的回车后跟一个必选的换行符。最后一行即使没有换行符也会作为一个token返回。</p>
|
||
<h2 id="Scanner">type <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#30" title="View Source">Scanner</a> </h2>
|
||
<pre>type Scanner struct {
|
||
<span class="com">// 内含隐藏或非导出字段</span>
|
||
}</pre>
|
||
<p align="left">Scanner类型提供了方便的读取数据的接口，如从换行符分隔的文本里读取每一行。</p>
|
||
<p align="left">成功调用的Scan方法会逐步提供文件的token，跳过token之间的字节。token由SplitFunc类型的分割函数指定；默认的分割函数会将输入分割为多个行，并去掉行尾的换行标志。本包预定义的分割函数可以将文件分割为行、字节、unicode码值、空白分隔的word。调用者可以定制自己的分割函数。</p>
|
||
<p align="left">扫描会在抵达输入流结尾、遇到的第一个I/O错误、token过大不能保存进缓冲时，不可恢复的停止。当扫描停止后，当前读取位置可能会远在最后一个获得的token后面。需要更多对错误管理的控制或token很大，或必须从reader连续扫描的程序，应使用bufio.Reader代替。</p>
|
||
<div class="panel-group">
|
||
<div class="panel panel-default" id="example-Scanner--Custom">
|
||
<div class="panel-heading" onclick="document.getElementById('ex-Scanner--Custom').style.display = document.getElementById('ex-Scanner--Custom').style.display=='none'?'block':'none';">Example (Custom)</div>
|
||
<div class="panel-collapse collapse" id="ex-Scanner--Custom">
|
||
<div class="panel-body">
|
||
<pre><span class="com">// An artificial input source.</span>
|
||
const input = "1234 5678 1234567901234567890"
|
||
scanner := bufio.NewScanner(strings.NewReader(input))
|
||
<span class="com">// Create a custom split function by wrapping the existing ScanWords function.</span>
|
||
split := func(data []byte, atEOF bool) (advance int, token []byte, err error) {
|
||
advance, token, err = bufio.ScanWords(data, atEOF)
|
||
if err == nil && token != nil {
|
||
_, err = strconv.ParseInt(string(token), 10, 32)
|
||
}
|
||
return
|
||
}
|
||
<span class="com">// Set the split function for the scanning operation.</span>
|
||
scanner.Split(split)
|
||
<span class="com">// Validate the input</span>
|
||
for scanner.Scan() {
|
||
fmt.Printf("%s\n", scanner.Text())
|
||
}
|
||
if err := scanner.Err(); err != nil {
|
||
fmt.Printf("Invalid input: %s", err)
|
||
}</pre>
|
||
<p>Output:
|
||
</p><pre>1234
|
||
5678
|
||
Invalid input: strconv.ParseInt: parsing "1234567901234567890": value out of range
|
||
</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="panel panel-default" id="example-Scanner--Lines">
|
||
<div class="panel-heading" onclick="document.getElementById('ex-Scanner--Lines').style.display = document.getElementById('ex-Scanner--Lines').style.display=='none'?'block':'none';">Example (Lines)</div>
|
||
<div class="panel-collapse collapse" id="ex-Scanner--Lines">
|
||
<div class="panel-body">
|
||
<pre>scanner := bufio.NewScanner(os.Stdin)
|
||
for scanner.Scan() {
|
||
fmt.Println(scanner.Text()) <span class="com">// Println will add back the final '\n'</span>
|
||
}
|
||
if err := scanner.Err(); err != nil {
|
||
fmt.Fprintln(os.Stderr, "reading standard input:", err)
|
||
}
|
||
</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="panel panel-default" id="example-Scanner--Words">
|
||
<div class="panel-heading" onclick="document.getElementById('ex-Scanner--Words').style.display = document.getElementById('ex-Scanner--Words').style.display=='none'?'block':'none';">Example (Words)</div>
|
||
<div class="panel-collapse collapse" id="ex-Scanner--Words">
|
||
<div class="panel-body">
|
||
<pre><span class="com">// An artificial input source.</span>
|
||
const input = "Now is the winter of our discontent,\nMade glorious summer by this sun of York.\n"
|
||
scanner := bufio.NewScanner(strings.NewReader(input))
|
||
<span class="com">// Set the split function for the scanning operation.</span>
|
||
scanner.Split(bufio.ScanWords)
|
||
<span class="com">// Count the words.</span>
|
||
count := 0
|
||
for scanner.Scan() {
|
||
count++
|
||
}
|
||
if err := scanner.Err(); err != nil {
|
||
fmt.Fprintln(os.Stderr, "reading input:", err)
|
||
}
|
||
fmt.Printf("%d\n", count)</pre>
|
||
<p>Output:
|
||
</p><pre>15
|
||
</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h3 id="NewScanner">func <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#74" title="View Source">NewScanner</a> </h3>
|
||
<pre class="funcdecl">func NewScanner(r <a href="io.htm">io</a>.<a href="io.htm#Reader">Reader</a>) *<a href="#Scanner">Scanner</a></pre>
|
||
<p>NewScanner创建并返回一个从r读取数据的Scanner，默认的分割函数是ScanLines。</p>
|
||
<h3 id="Scanner.Split">func (*Scanner) <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#206" title="View Source">Split</a> </h3>
|
||
<pre class="funcdecl">func (s *<a href="#Scanner">Scanner</a>) Split(split <a href="#SplitFunc">SplitFunc</a>)</pre>
|
||
<p>Split设置该Scanner的分割函数。本方法必须在Scan之前调用。</p>
|
||
<h3 id="Scanner.Scan">func (*Scanner) <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#110" title="View Source">Scan</a> </h3>
|
||
<pre class="funcdecl">func (s *<a href="#Scanner">Scanner</a>) Scan() <a href="builtin.htm#bool">bool</a></pre>
|
||
<p>Scan方法获取当前位置的token（该token可以通过Bytes或Text方法获得），并让Scanner的扫描位置移动到下一个token。当扫描因为抵达输入流结尾或者遇到错误而停止时，本方法会返回false。在Scan方法返回false后，Err方法将返回扫描时遇到的任何错误；除非是io.EOF，此时Err会返回nil。</p>
|
||
<h3 id="Scanner.Bytes">func (*Scanner) <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#94" title="View Source">Bytes</a> </h3>
|
||
<pre class="funcdecl">func (s *<a href="#Scanner">Scanner</a>) Bytes() []<a href="builtin.htm#byte">byte</a></pre>
|
||
<p>Bytes方法返回最近一次Scan调用生成的token。底层数组指向的数据可能会被下一次Scan的调用重写。</p>
|
||
<h3 id="Scanner.Text">func (*Scanner) <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#100" title="View Source">Text</a> </h3>
|
||
<pre class="funcdecl">func (s *<a href="#Scanner">Scanner</a>) Text() <a href="builtin.htm#string">string</a></pre>
|
||
<p>Bytes方法返回最近一次Scan调用生成的token，会申请创建一个字符串保存token并返回该字符串。</p>
|
||
<h3 id="Scanner.Err">func (*Scanner) <a href="https://github.com/golang/go/blob/master/src/bufio/scan.go?name=release#84" title="View Source">Err</a> </h3>
|
||
<pre class="funcdecl">func (s *<a href="#Scanner">Scanner</a>) Err() <a href="builtin.htm#error">error</a></pre>
|
||
<p>Err返回Scanner遇到的第一个非EOF的错误。</p>
|
||
</div> |