Use seek enums and show other seek methods (#524)
* Use seek whence values * Add examples of seeking with other methods
This commit is contained in:
Elias Kauppi
@@ -43,7 +43,7 @@ func main() {
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// You can also `Seek` to a known location in the file
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// and `Read` from there.
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o2, err := f.Seek(6, 0)
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o2, err := f.Seek(6, io.SeekStart)
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check(err)
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b2 := make([]byte, 2)
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n2, err := f.Read(b2)
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@@ -51,20 +51,29 @@ func main() {
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fmt.Printf("%d bytes @ %d: ", n2, o2)
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fmt.Printf("%v\n", string(b2[:n2]))
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// Other methods of seeking are relative to the
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// current cursor position,
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_, err = f.Seek(4, io.SeekCurrent)
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check(err)
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// and relative to the end of the file.
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_, err = f.Seek(-10, io.SeekEnd)
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check(err)
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// The `io` package provides some functions that may
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// be helpful for file reading. For example, reads
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// like the ones above can be more robustly
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// implemented with `ReadAtLeast`.
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o3, err := f.Seek(6, 0)
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o3, err := f.Seek(6, io.SeekStart)
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check(err)
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b3 := make([]byte, 2)
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n3, err := io.ReadAtLeast(f, b3, 2)
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check(err)
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fmt.Printf("%d bytes @ %d: %s\n", n3, o3, string(b3))
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// There is no built-in rewind, but `Seek(0, 0)`
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// accomplishes this.
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_, err = f.Seek(0, 0)
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// There is no built-in rewind, but
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// `Seek(0, io.SeekStart)` accomplishes this.
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_, err = f.Seek(0, io.SeekStart)
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check(err)
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// The `bufio` package implements a buffered
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@@ -1,2 +1,2 @@
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5351edae47bb2f2c9b5d4b9682b8176beb0c24e5
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DF2Wo8nDKaF
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754d3ce4873b6f8f1c81364bfcf5fedb17020c11
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upAKv1DPNMp
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39
public/reading-files
generated
39
public/reading-files
generated
@@ -43,7 +43,7 @@ reading files.</p>
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</td>
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<td class="code leading">
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<a href="https://go.dev/play/p/DF2Wo8nDKaF"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<a href="https://go.dev/play/p/upAKv1DPNMp"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">package</span> <span class="nx">main</span></span></span></code></pre>
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</td>
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</tr>
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@@ -141,7 +141,7 @@ and <code>Read</code> from there.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">o2</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Seek</span><span class="p">(</span><span class="mi">6</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">o2</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Seek</span><span class="p">(</span><span class="mi">6</span><span class="p">,</span> <span class="nx">io</span><span class="p">.</span><span class="nx">SeekStart</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <span class="nx">b2</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">byte</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <span class="nx">n2</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Read</span><span class="p">(</span><span class="nx">b2</span><span class="p">)</span>
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@@ -151,6 +151,31 @@ and <code>Read</code> from there.</p>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Other methods of seeking are relative to the
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current cursor position,</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">_</span><span class="p">,</span> <span class="nx">err</span> <span class="p">=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Seek</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span> <span class="nx">io</span><span class="p">.</span><span class="nx">SeekCurrent</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>and relative to the end of the file.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">_</span><span class="p">,</span> <span class="nx">err</span> <span class="p">=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Seek</span><span class="p">(</span><span class="o">-</span><span class="mi">10</span><span class="p">,</span> <span class="nx">io</span><span class="p">.</span><span class="nx">SeekEnd</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>The <code>io</code> package provides some functions that may
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@@ -161,7 +186,7 @@ implemented with <code>ReadAtLeast</code>.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">o3</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Seek</span><span class="p">(</span><span class="mi">6</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">o3</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Seek</span><span class="p">(</span><span class="mi">6</span><span class="p">,</span> <span class="nx">io</span><span class="p">.</span><span class="nx">SeekStart</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <span class="nx">b3</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">byte</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <span class="nx">n3</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">io</span><span class="p">.</span><span class="nf">ReadAtLeast</span><span class="p">(</span><span class="nx">f</span><span class="p">,</span> <span class="nx">b3</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span>
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@@ -172,13 +197,13 @@ implemented with <code>ReadAtLeast</code>.</p>
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<tr>
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<td class="docs">
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<p>There is no built-in rewind, but <code>Seek(0, 0)</code>
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accomplishes this.</p>
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<p>There is no built-in rewind, but
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<code>Seek(0, io.SeekStart)</code> accomplishes this.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">_</span><span class="p">,</span> <span class="nx">err</span> <span class="p">=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Seek</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">_</span><span class="p">,</span> <span class="nx">err</span> <span class="p">=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Seek</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="nx">io</span><span class="p">.</span><span class="nx">SeekStart</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span></span></span></code></pre>
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</td>
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</tr>
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@@ -262,7 +287,7 @@ be scheduled immediately after <code>Open</code>ing with
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</div>
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<script>
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var codeLines = [];
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</script>
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<script src="site.js" async></script>
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</body>
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