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      <h1 class="title">std/memfiles</h1>
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    <ul class="simple simple-toc" id="toc-list">
  <li>
  <a class="reference reference-toplevel" href="#6" id="56">Imports</a>
</li>
<li>
  <details open>
    <summary><a class="reference reference-toplevel" href="#7" id="57">Types</a></summary>
    <ul class="simple simple-toc-section">
      <li><a class="reference" href="#MemFile" title="MemFile = object
  mem*: pointer              ## a pointer to the memory mapped file. The pointer
                             ## can be used directly to change the contents of the
                             ## file, if it was opened with write access.
  size*: int                 ## size of the memory mapped file
  when defined(windows):
    fHandle*: Handle ## **Caution**: Windows specific public field to allow
                     ## even more low level trickery.
    mapHandle*: Handle       ## **Caution**: Windows specific public field.
    wasOpened*: bool         ## **Caution**: Windows specific public field.
  else:
    handle*: cint            ## **Caution**: Posix specific public field.
    ## **Caution**: Platform specific private field.">MemFile</a></li>
<li><a class="reference" href="#MemMapFileStream" title="MemMapFileStream = ref MemMapFileStreamObj">MemMapFileStream</a></li>
<li><a class="reference" href="#MemMapFileStreamObj" title="MemMapFileStreamObj = object of Stream">MemMapFileStreamObj</a></li>
<li><a class="reference" href="#MemSlice" title="MemSlice = object
  data*: pointer
  size*: int">MemSlice</a></li>

    </ul>
  </details>
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  <details open>
    <summary><a class="reference reference-toplevel" href="#12" id="62">Procs</a></summary>
    <ul class="simple simple-toc-section">
      <ul class="simple nested-toc-section">$
  <li><a class="reference" href="#%24%2CMemSlice" title="`$`(ms: MemSlice): string">`$`(ms: MemSlice): string</a></li>

</ul>
<ul class="simple nested-toc-section">==
  <li><a class="reference" href="#%3D%3D%2CMemSlice%2CMemSlice" title="`==`(x, y: MemSlice): bool">`==`(x, y: MemSlice): bool</a></li>

</ul>
<ul class="simple nested-toc-section">close
  <li><a class="reference" href="#close%2CMemFile" title="close(f: var MemFile)">close(f: var MemFile)</a></li>

</ul>
<ul class="simple nested-toc-section">flush
  <li><a class="reference" href="#flush%2CMemFile%2CNatural" title="flush(f: var MemFile; attempts: Natural = 3)">flush(f: var MemFile; attempts: Natural = 3)</a></li>

</ul>
<ul class="simple nested-toc-section">mapMem
  <li><a class="reference" href="#mapMem%2CMemFile%2CFileMode%2Cint%2Cint" title="mapMem(m: var MemFile; mode: FileMode = fmRead; mappedSize = -1; offset = 0;
       mapFlags = cint(-1)): pointer">mapMem(m: var MemFile; mode: FileMode = fmRead; mappedSize = -1; offset = 0;
       mapFlags = cint(-1)): pointer</a></li>

</ul>
<ul class="simple nested-toc-section">newMemMapFileStream
  <li><a class="reference" href="#newMemMapFileStream%2Cstring%2CFileMode%2Cint" title="newMemMapFileStream(filename: string; mode: FileMode = fmRead;
                    fileSize: int = -1): MemMapFileStream">newMemMapFileStream(filename: string; mode: FileMode = fmRead;
                    fileSize: int = -1): MemMapFileStream</a></li>

</ul>
<ul class="simple nested-toc-section">open
  <li><a class="reference" href="#open%2Cstring%2CFileMode%2Cint%2Cint%2Cint" title="open(filename: string; mode: FileMode = fmRead; mappedSize = -1; offset = 0;
     newFileSize = -1; allowRemap = false; mapFlags = cint(-1)): MemFile">open(filename: string; mode: FileMode = fmRead; mappedSize = -1; offset = 0;
     newFileSize = -1; allowRemap = false; mapFlags = cint(-1)): MemFile</a></li>

</ul>
<ul class="simple nested-toc-section">resize
  <li><a class="reference" href="#resize%2CMemFile%2Cint" title="resize(f: var MemFile; newFileSize: int)">resize(f: var MemFile; newFileSize: int)</a></li>

</ul>
<ul class="simple nested-toc-section">unmapMem
  <li><a class="reference" href="#unmapMem%2CMemFile%2Cpointer%2Cint" title="unmapMem(f: var MemFile; p: pointer; size: int)">unmapMem(f: var MemFile; p: pointer; size: int)</a></li>

</ul>

    </ul>
  </details>
</li>
<li>
  <details open>
    <summary><a class="reference reference-toplevel" href="#15" id="65">Iterators</a></summary>
    <ul class="simple simple-toc-section">
      <ul class="simple nested-toc-section">lines
  <li><a class="reference" href="#lines.i%2CMemFile%2Cstring%2Cchar%2Cchar" title="lines(mfile: MemFile; buf: var string; delim = '\n'; eat = '\r'): string">lines(mfile: MemFile; buf: var string; delim = '\n'; eat = '\r'): string</a></li>
<li><a class="reference" href="#lines.i%2CMemFile%2Cchar%2Cchar" title="lines(mfile: MemFile; delim = '\n'; eat = '\r'): string">lines(mfile: MemFile; delim = '\n'; eat = '\r'): string</a></li>

</ul>
<ul class="simple nested-toc-section">memSlices
  <li><a class="reference" href="#memSlices.i%2CMemFile%2Cchar%2Cchar" title="memSlices(mfile: MemFile; delim = '\n'; eat = '\r'): MemSlice">memSlices(mfile: MemFile; delim = '\n'; eat = '\r'): MemSlice</a></li>

</ul>

    </ul>
  </details>
</li>

</ul>

  </div>
  <div class="nine columns" id="content">
    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L1" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L1" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

    <div id="tocRoot"></div>
    
    <p class="module-desc"><table class="docinfo" frame="void" rules="none"><col class="docinfo-name" /><col class="docinfo-content" /><tbody valign="top"><tr><th class="docinfo-name">Authors:</th><td>Zahary Karadjov, Andreas Rumpf</td></tr>
</tbody></table><p>This module provides support for <span id="memory-mapped-files_1">memory mapped files</span> (Posix's <span id="mmap_1">mmap</span>) on the different operating systems.</p>
<p>It also provides some fast iterators over lines in text files (or other &quot;line-like&quot;, variable length, delimited records).</p>
</p>
    <div class="section" id="6">
  <h1><a class="toc-backref" href="#6">Imports</a></h1>
  <dl class="item">
    <a class="reference external" href="posix.html">posix</a>, <a class="reference external" href="streams.html">streams</a>, <a class="reference external" href="oserrors.html">oserrors</a>, <a class="reference external" href="syncio.html">syncio</a>, <a class="reference external" href="assertions.html">assertions</a>, <a class="reference external" href="ansi_c.html">ansi_c</a>
  </dl>
</div>
<div class="section" id="7">
  <h1><a class="toc-backref" href="#7">Types</a></h1>
  <dl class="item">
    <div id="MemFile">
  <dt><pre><a href="memfiles.html#MemFile"><span class="Identifier">MemFile</span></a> <span class="Other">=</span> <span class="Keyword">object</span>
  <span class="Identifier">mem</span><span class="Operator">*</span><span class="Other">:</span> <a href="system.html#pointer"><span class="Identifier">pointer</span></a>              <span class="Comment">## a pointer to the memory mapped file. The pointer</span>
                             <span class="Comment">## can be used directly to change the contents of the</span>
                             <span class="Comment">## file, if it was opened with write access.</span>
  <span class="Identifier">size</span><span class="Operator">*</span><span class="Other">:</span> <a href="system.html#int"><span class="Identifier">int</span></a>                 <span class="Comment">## size of the memory mapped file</span>
  <span class="Keyword">when</span> <span class="Identifier">defined</span><span class="Other">(</span><span class="Identifier">windows</span><span class="Other">)</span><span class="Other">:</span>
    <span class="Identifier">fHandle</span><span class="Operator">*</span><span class="Other">:</span> <span class="Identifier">Handle</span> <span class="Comment">## **Caution**: Windows specific public field to allow</span>
                     <span class="Comment">## even more low level trickery.</span>
    <span class="Identifier">mapHandle</span><span class="Operator">*</span><span class="Other">:</span> <span class="Identifier">Handle</span>       <span class="Comment">## **Caution**: Windows specific public field.</span>
    <span class="Identifier">wasOpened</span><span class="Operator">*</span><span class="Other">:</span> <span class="Identifier">bool</span>         <span class="Comment">## **Caution**: Windows specific public field.</span>
  <span class="Keyword">else</span><span class="Other">:</span>
    <span class="Identifier">handle</span><span class="Operator">*</span><span class="Other">:</span> <span class="Identifier">cint</span>            <span class="Comment">## **Caution**: Posix specific public field.</span>
    <span class="Comment">## **Caution**: Platform specific private field.</span></pre></dt>
  <dd>
    
    represents a memory mapped file
    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L69" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L69" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>
<div id="MemMapFileStream">
  <dt><pre><a href="memfiles.html#MemMapFileStream"><span class="Identifier">MemMapFileStream</span></a> <span class="Other">=</span> <span class="Keyword">ref</span> <a href="memfiles.html#MemMapFileStreamObj"><span class="Identifier">MemMapFileStreamObj</span></a></pre></dt>
  <dd>
    
    a stream that encapsulates a <tt class="docutils literal"><span class="pre"><span class="Identifier">MemFile</span></span></tt>
    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L504" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L504" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>
<div id="MemMapFileStreamObj">
  <dt><pre><a href="memfiles.html#MemMapFileStreamObj"><span class="Identifier">MemMapFileStreamObj</span></a> <span class="Other">=</span> <span class="Keyword">object</span> <span class="Keyword">of</span> <a href="streams.html#Stream"><span class="Identifier">Stream</span></a></pre></dt>
  <dd>
    
    
    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L505" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L505" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>
<div id="MemSlice">
  <dt><pre><a href="memfiles.html#MemSlice"><span class="Identifier">MemSlice</span></a> <span class="Other">=</span> <span class="Keyword">object</span>
  <span class="Identifier">data</span><span class="Operator">*</span><span class="Other">:</span> <a href="system.html#pointer"><span class="Identifier">pointer</span></a>
  <span class="Identifier">size</span><span class="Operator">*</span><span class="Other">:</span> <a href="system.html#int"><span class="Identifier">int</span></a></pre></dt>
  <dd>
    
    represent slice of a MemFile for iteration over delimited lines/records
    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L407" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L407" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>

  </dl>
</div>
<div class="section" id="12">
  <h1><a class="toc-backref" href="#12">Procs</a></h1>
  <dl class="item">
    <div id="$-procs-all">
  <div id="$,MemSlice">
  <dt><pre><span class="Keyword">proc</span> <a href="#%24%2CMemSlice"><span class="Identifier">`$`</span></a><span class="Other">(</span><span class="Identifier">ms</span><span class="Other">:</span> <a href="memfiles.html#MemSlice"><span class="Identifier">MemSlice</span></a><span class="Other">)</span><span class="Other">:</span> <a href="system.html#string"><span class="Identifier">string</span></a> {.<span class="Identifier">inline</span><span class="Other">,</span> <span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    Return a Nim string built from a MemSlice.
    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L415" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L415" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>

</div>
<div id="==-procs-all">
  <div id="==,MemSlice,MemSlice">
  <dt><pre><span class="Keyword">proc</span> <a href="#%3D%3D%2CMemSlice%2CMemSlice"><span class="Identifier">`==`</span></a><span class="Other">(</span><span class="Identifier">x</span><span class="Other">,</span> <span class="Identifier">y</span><span class="Other">:</span> <a href="memfiles.html#MemSlice"><span class="Identifier">MemSlice</span></a><span class="Other">)</span><span class="Other">:</span> <a href="system.html#bool"><span class="Identifier">bool</span></a> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    Compare a pair of MemSlice for strict equality.
    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L411" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L411" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>

</div>
<div id="close-procs-all">
  <div id="close,MemFile">
  <dt><pre><span class="Keyword">proc</span> <a href="#close%2CMemFile"><span class="Identifier">close</span></a><span class="Other">(</span><span class="Identifier">f</span><span class="Other">:</span> <span class="Keyword">var</span> <a href="memfiles.html#MemFile"><span class="Identifier">MemFile</span></a><span class="Other">)</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Identifier">OSError</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    closes the memory mapped file <tt class="docutils literal"><span class="pre"><span class="Identifier">f</span></span></tt>. All changes are written back to the file system, if <tt class="docutils literal"><span class="pre"><span class="Identifier">f</span></span></tt> was opened with write access.
    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L371" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L371" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>

</div>
<div id="flush-procs-all">
  <div id="flush,MemFile,Natural">
  <dt><pre><span class="Keyword">proc</span> <a href="#flush%2CMemFile%2CNatural"><span class="Identifier">flush</span></a><span class="Other">(</span><span class="Identifier">f</span><span class="Other">:</span> <span class="Keyword">var</span> <a href="memfiles.html#MemFile"><span class="Identifier">MemFile</span></a><span class="Other">;</span> <span class="Identifier">attempts</span><span class="Other">:</span> <a href="system.html#Natural"><span class="Identifier">Natural</span></a> <span class="Other">=</span> <span class="DecNumber">3</span><span class="Other">)</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Identifier">OSError</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span>
    <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    Flushes <tt class="docutils literal"><span class="pre"><span class="Identifier">f</span></span></tt>'s buffer for the number of attempts equal to <tt class="docutils literal"><span class="pre"><span class="Identifier">attempts</span></span></tt>. If were errors an exception <tt class="docutils literal"><span class="pre"><span class="Identifier">OSError</span></span></tt> will be raised.
    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L295" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L295" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>

</div>
<div id="mapMem-procs-all">
  <div id="mapMem,MemFile,FileMode,int,int">
  <dt><pre><span class="Keyword">proc</span> <a href="#mapMem%2CMemFile%2CFileMode%2Cint%2Cint"><span class="Identifier">mapMem</span></a><span class="Other">(</span><span class="Identifier">m</span><span class="Other">:</span> <span class="Keyword">var</span> <a href="memfiles.html#MemFile"><span class="Identifier">MemFile</span></a><span class="Other">;</span> <span class="Identifier">mode</span><span class="Other">:</span> <a href="syncio.html#FileMode"><span class="Identifier">FileMode</span></a> <span class="Other">=</span> <span class="Identifier">fmRead</span><span class="Other">;</span> <span class="Identifier">mappedSize</span> <span class="Other">=</span> <span class="DecNumber">-1</span><span class="Other">;</span>
            <span class="Identifier">offset</span> <span class="Other">=</span> <span class="DecNumber">0</span><span class="Other">;</span> <span class="Identifier">mapFlags</span> <span class="Other">=</span> <a href="ctypes.html#cint"><span class="Identifier">cint</span></a><span class="Other">(</span><span class="DecNumber">-1</span><span class="Other">)</span><span class="Other">)</span><span class="Other">:</span> <a href="system.html#pointer"><span class="Identifier">pointer</span></a> {.
    <span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Identifier">IOError</span><span class="Other">,</span> <span class="Identifier">OSError</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    <p>returns a pointer to a mapped portion of MemFile <tt class="docutils literal"><span class="pre"><span class="Identifier">m</span></span></tt></p>
<p><tt class="docutils literal"><span class="pre"><span class="Identifier">mappedSize</span></span></tt> of <tt class="docutils literal"><span class="pre"><span class="Operator">-</span><span class="DecNumber">1</span></span></tt> maps to the whole file, and <tt class="docutils literal"><span class="pre"><span class="Identifier">offset</span></span></tt> must be multiples of the PAGE SIZE of your OS</p>

    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L84" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L84" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>

</div>
<div id="newMemMapFileStream-procs-all">
  <div id="newMemMapFileStream,string,FileMode,int">
  <dt><pre><span class="Keyword">proc</span> <a href="#newMemMapFileStream%2Cstring%2CFileMode%2Cint"><span class="Identifier">newMemMapFileStream</span></a><span class="Other">(</span><span class="Identifier">filename</span><span class="Other">:</span> <a href="system.html#string"><span class="Identifier">string</span></a><span class="Other">;</span> <span class="Identifier">mode</span><span class="Other">:</span> <a href="syncio.html#FileMode"><span class="Identifier">FileMode</span></a> <span class="Other">=</span> <span class="Identifier">fmRead</span><span class="Other">;</span>
                         <span class="Identifier">fileSize</span><span class="Other">:</span> <a href="system.html#int"><span class="Identifier">int</span></a> <span class="Other">=</span> <span class="DecNumber">-1</span><span class="Other">)</span><span class="Other">:</span> <a href="memfiles.html#MemMapFileStream"><span class="Identifier">MemMapFileStream</span></a> {.
    <span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Identifier">IOError</span><span class="Other">,</span> <span class="Identifier">OSError</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    creates a new stream from the file named <tt class="docutils literal"><span class="pre"><span class="Identifier">filename</span></span></tt> with the mode <tt class="docutils literal"><span class="pre"><span class="Identifier">mode</span></span></tt>. Raises ## <tt class="docutils literal"><span class="pre"><span class="Identifier">OSError</span></span></tt> if the file cannot be opened. See the <a class="reference external" href="system.html">system</a> module for a list of available FileMode enums. <tt class="docutils literal"><span class="pre"><span class="Identifier">fileSize</span></span></tt> can only be set if the file does not exist and is opened with write access (e.g., with fmReadWrite).
    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L548" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L548" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>

</div>
<div id="open-procs-all">
  <div id="open,string,FileMode,int,int,int">
  <dt><pre><span class="Keyword">proc</span> <a href="#open%2Cstring%2CFileMode%2Cint%2Cint%2Cint"><span class="Identifier">open</span></a><span class="Other">(</span><span class="Identifier">filename</span><span class="Other">:</span> <a href="system.html#string"><span class="Identifier">string</span></a><span class="Other">;</span> <span class="Identifier">mode</span><span class="Other">:</span> <a href="syncio.html#FileMode"><span class="Identifier">FileMode</span></a> <span class="Other">=</span> <span class="Identifier">fmRead</span><span class="Other">;</span> <span class="Identifier">mappedSize</span> <span class="Other">=</span> <span class="DecNumber">-1</span><span class="Other">;</span>
          <span class="Identifier">offset</span> <span class="Other">=</span> <span class="DecNumber">0</span><span class="Other">;</span> <span class="Identifier">newFileSize</span> <span class="Other">=</span> <span class="DecNumber">-1</span><span class="Other">;</span> <span class="Identifier">allowRemap</span> <span class="Other">=</span> <span class="Identifier">false</span><span class="Other">;</span> <span class="Identifier">mapFlags</span> <span class="Other">=</span> <a href="ctypes.html#cint"><span class="Identifier">cint</span></a><span class="Other">(</span><span class="DecNumber">-1</span><span class="Other">)</span><span class="Other">)</span><span class="Other">:</span> <a href="memfiles.html#MemFile"><span class="Identifier">MemFile</span></a> {.
    <span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Identifier">IOError</span><span class="Other">,</span> <span class="Identifier">OSError</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    <p>opens a memory mapped file. If this fails, <tt class="docutils literal"><span class="pre"><span class="Identifier">OSError</span></span></tt> is raised.</p>
<p><tt class="docutils literal"><span class="pre"><span class="Identifier">newFileSize</span></span></tt> can only be set if the file does not exist and is opened with write access (e.g., with fmReadWrite).</p>
<p><tt class="docutils literal"><span class="pre"><span class="Identifier">mappedSize</span></span></tt> and <tt class="docutils literal"><span class="pre"><span class="Identifier">offset</span></span></tt> can be used to map only a slice of the file.</p>
<p><tt class="docutils literal"><span class="pre"><span class="Identifier">offset</span></span></tt> must be multiples of the PAGE SIZE of your OS (usually 4K or 8K but is unique to your OS)</p>
<p><tt class="docutils literal"><span class="pre"><span class="Identifier">allowRemap</span></span></tt> only needs to be true if you want to call <tt class="docutils literal"><span class="pre"><span class="Identifier">mapMem</span></span></tt> on the resulting MemFile; else file handles are not kept open.</p>
<p><tt class="docutils literal"><span class="pre"><span class="Identifier">mapFlags</span></span></tt> allows callers to override default choices for memory mapping flags with a bitwise mask of a variety of likely platform-specific flags which may be ignored or even cause <tt class="docutils literal"><span class="pre"><span class="Identifier">open</span></span></tt> to fail if misspecified.</p>
<p>Example:</p>
<p><pre class="listing"><span class="Keyword">var</span>
  <span class="Identifier">mm</span><span class="Punctuation">,</span> <span class="Identifier">mm_full</span><span class="Punctuation">,</span> <span class="Identifier">mm_half</span><span class="Punctuation">:</span> <span class="Identifier">MemFile</span>

<span class="Identifier">mm</span> <span class="Operator">=</span> <span class="Identifier">memfiles</span><span class="Operator">.</span><span class="Identifier">open</span><span class="Punctuation">(</span><span class="StringLit">&quot;/tmp/test.mmap&quot;</span><span class="Punctuation">,</span> <span class="Identifier">mode</span> <span class="Operator">=</span> <span class="Identifier">fmWrite</span><span class="Punctuation">,</span> <span class="Identifier">newFileSize</span> <span class="Operator">=</span> <span class="DecNumber">1024</span><span class="Punctuation">)</span>    <span class="Comment"># Create a new file</span>
<span class="Identifier">mm</span><span class="Operator">.</span><span class="Identifier">close</span><span class="Punctuation">(</span><span class="Punctuation">)</span>

<span class="Comment"># Read the whole file, would fail if newFileSize was set</span>
<span class="Identifier">mm_full</span> <span class="Operator">=</span> <span class="Identifier">memfiles</span><span class="Operator">.</span><span class="Identifier">open</span><span class="Punctuation">(</span><span class="StringLit">&quot;/tmp/test.mmap&quot;</span><span class="Punctuation">,</span> <span class="Identifier">mode</span> <span class="Operator">=</span> <span class="Identifier">fmReadWrite</span><span class="Punctuation">,</span> <span class="Identifier">mappedSize</span> <span class="Operator">=</span> <span class="Operator">-</span><span class="DecNumber">1</span><span class="Punctuation">)</span>

<span class="Comment"># Read the first 512 bytes</span>
<span class="Identifier">mm_half</span> <span class="Operator">=</span> <span class="Identifier">memfiles</span><span class="Operator">.</span><span class="Identifier">open</span><span class="Punctuation">(</span><span class="StringLit">&quot;/tmp/test.mmap&quot;</span><span class="Punctuation">,</span> <span class="Identifier">mode</span> <span class="Operator">=</span> <span class="Identifier">fmReadWrite</span><span class="Punctuation">,</span> <span class="Identifier">mappedSize</span> <span class="Operator">=</span> <span class="DecNumber">512</span><span class="Punctuation">)</span></pre></p>

    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L135" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L135" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>

</div>
<div id="resize-procs-all">
  <div id="resize,MemFile,int">
  <dt><pre><span class="Keyword">proc</span> <a href="#resize%2CMemFile%2Cint"><span class="Identifier">resize</span></a><span class="Other">(</span><span class="Identifier">f</span><span class="Other">:</span> <span class="Keyword">var</span> <a href="memfiles.html#MemFile"><span class="Identifier">MemFile</span></a><span class="Other">;</span> <span class="Identifier">newFileSize</span><span class="Other">:</span> <a href="system.html#int"><span class="Identifier">int</span></a><span class="Other">)</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><a href="exceptions.html#IOError"><span class="Identifier">IOError</span></a><span class="Other">,</span> <a href="exceptions.html#OSError"><span class="Identifier">OSError</span></a><span class="Other">]</span><span class="Other">,</span>
    <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    Resize &amp; re-map the file underlying an <tt class="docutils literal"><span class="pre"><span class="Identifier">allowRemap</span> <span class="Identifier">MemFile</span></span></tt>.  If the OS/FS supports it, file space is reserved to ensure room for new virtual pages. Caller should wait often enough for <tt class="docutils literal"><span class="pre"><span class="Identifier">flush</span></span></tt> to finish to limit use of system RAM for write buffering, perhaps just prior to this call. <strong>Note</strong>: this assumes the entire file is mapped read-write at offset 0. Also, the value of <tt class="docutils literal"><span class="pre"><span class="Operator">.</span><span class="Identifier">mem</span></span></tt> will probably change.
    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L317" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L317" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>

</div>
<div id="unmapMem-procs-all">
  <div id="unmapMem,MemFile,pointer,int">
  <dt><pre><span class="Keyword">proc</span> <a href="#unmapMem%2CMemFile%2Cpointer%2Cint"><span class="Identifier">unmapMem</span></a><span class="Other">(</span><span class="Identifier">f</span><span class="Other">:</span> <span class="Keyword">var</span> <a href="memfiles.html#MemFile"><span class="Identifier">MemFile</span></a><span class="Other">;</span> <span class="Identifier">p</span><span class="Other">:</span> <a href="system.html#pointer"><span class="Identifier">pointer</span></a><span class="Other">;</span> <span class="Identifier">size</span><span class="Other">:</span> <a href="system.html#int"><span class="Identifier">int</span></a><span class="Other">)</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Identifier">OSError</span><span class="Other">]</span><span class="Other">,</span>
    <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    <p>unmaps the memory region <tt class="docutils literal"><span class="pre"><span class="Punctuation">(</span><span class="Identifier">p</span><span class="Punctuation">,</span> <span class="Operator">&lt;</span><span class="Identifier">p</span><span class="Operator">+</span><span class="Identifier">size</span><span class="Punctuation">)</span></span></tt> of the mapped file <tt class="docutils literal"><span class="pre"><span class="Identifier">f</span></span></tt>. All changes are written back to the file system, if <tt class="docutils literal"><span class="pre"><span class="Identifier">f</span></span></tt> was opened with write access.</p>
<p><tt class="docutils literal"><span class="pre"><span class="Identifier">size</span></span></tt> must be of exactly the size that was requested via <tt class="docutils literal"><span class="pre"><span class="Identifier">mapMem</span></span></tt>.</p>

    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L122" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L122" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>

</div>

  </dl>
</div>
<div class="section" id="15">
  <h1><a class="toc-backref" href="#15">Iterators</a></h1>
  <dl class="item">
    <div id="lines-iterators-all">
  <div id="lines.i,MemFile,string,char,char">
  <dt><pre><span class="Keyword">iterator</span> <a href="#lines.i%2CMemFile%2Cstring%2Cchar%2Cchar"><span class="Identifier">lines</span></a><span class="Other">(</span><span class="Identifier">mfile</span><span class="Other">:</span> <a href="memfiles.html#MemFile"><span class="Identifier">MemFile</span></a><span class="Other">;</span> <span class="Identifier">buf</span><span class="Other">:</span> <span class="Keyword">var</span> <a href="system.html#string"><span class="Identifier">string</span></a><span class="Other">;</span> <span class="Identifier">delim</span> <span class="Other">=</span> <span class="CharLit">'\n'</span><span class="Other">;</span> <span class="Identifier">eat</span> <span class="Other">=</span> <span class="CharLit">'\r'</span><span class="Other">)</span><span class="Other">:</span> <a href="system.html#string"><span class="Identifier">string</span></a> {.
    <span class="Identifier">inline</span><span class="Other">,</span> <span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    <p>Replace contents of passed buffer with each new line, like <a class="reference external" href="syncio.html#readLine,File,string">readLine(File)</a>. <tt class="docutils literal"><span class="pre"><span class="Identifier">delim</span></span></tt>, <tt class="docutils literal"><span class="pre"><span class="Identifier">eat</span></span></tt>, and delimiting logic is exactly as for <a class="reference external" href="#memSlices.i,MemFile,char,char">memSlices</a>, but Nim strings are returned.</p>
<p>Example:</p>
<p><pre class="listing"><span class="Keyword">var</span> <span class="Identifier">buffer</span><span class="Punctuation">:</span> <span class="Identifier">string</span> <span class="Operator">=</span> <span class="StringLit">&quot;&quot;</span>
<span class="Keyword">for</span> <span class="Identifier">line</span> <span class="Keyword">in</span> <span class="Identifier">lines</span><span class="Punctuation">(</span><span class="Identifier">memfiles</span><span class="Operator">.</span><span class="Identifier">open</span><span class="Punctuation">(</span><span class="StringLit">&quot;foo&quot;</span><span class="Punctuation">)</span><span class="Punctuation">,</span> <span class="Identifier">buffer</span><span class="Punctuation">)</span><span class="Punctuation">:</span>
  <span class="Identifier">echo</span> <span class="Identifier">line</span></pre></p>

    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L469" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L469" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>
<div id="lines.i,MemFile,char,char">
  <dt><pre><span class="Keyword">iterator</span> <a href="#lines.i%2CMemFile%2Cchar%2Cchar"><span class="Identifier">lines</span></a><span class="Other">(</span><span class="Identifier">mfile</span><span class="Other">:</span> <a href="memfiles.html#MemFile"><span class="Identifier">MemFile</span></a><span class="Other">;</span> <span class="Identifier">delim</span> <span class="Other">=</span> <span class="CharLit">'\n'</span><span class="Other">;</span> <span class="Identifier">eat</span> <span class="Other">=</span> <span class="CharLit">'\r'</span><span class="Other">)</span><span class="Other">:</span> <a href="system.html#string"><span class="Identifier">string</span></a> {.<span class="Identifier">inline</span><span class="Other">,</span>
    <span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    <p>Return each line in a file as a Nim string, like <a class="reference external" href="syncio.html#lines.i,File">lines(File)</a>. <tt class="docutils literal"><span class="pre"><span class="Identifier">delim</span></span></tt>, <tt class="docutils literal"><span class="pre"><span class="Identifier">eat</span></span></tt>, and delimiting logic is exactly as for <a class="reference external" href="#memSlices.i,MemFile,char,char">memSlices</a>, but Nim strings are returned.</p>
<p>Example:</p>
<p><pre class="listing"><span class="Keyword">for</span> <span class="Identifier">line</span> <span class="Keyword">in</span> <span class="Identifier">lines</span><span class="Punctuation">(</span><span class="Identifier">memfiles</span><span class="Operator">.</span><span class="Identifier">open</span><span class="Punctuation">(</span><span class="StringLit">&quot;foo&quot;</span><span class="Punctuation">)</span><span class="Punctuation">)</span><span class="Punctuation">:</span>
  <span class="Identifier">echo</span> <span class="Identifier">line</span></pre></p>

    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L488" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L488" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
</div>

</div>
<div id="memSlices-iterators-all">
  <div id="memSlices.i,MemFile,char,char">
  <dt><pre><span class="Keyword">iterator</span> <a href="#memSlices.i%2CMemFile%2Cchar%2Cchar"><span class="Identifier">memSlices</span></a><span class="Other">(</span><span class="Identifier">mfile</span><span class="Other">:</span> <a href="memfiles.html#MemFile"><span class="Identifier">MemFile</span></a><span class="Other">;</span> <span class="Identifier">delim</span> <span class="Other">=</span> <span class="CharLit">'\n'</span><span class="Other">;</span> <span class="Identifier">eat</span> <span class="Other">=</span> <span class="CharLit">'\r'</span><span class="Other">)</span><span class="Other">:</span> <a href="memfiles.html#MemSlice"><span class="Identifier">MemSlice</span></a> {.<span class="Identifier">inline</span><span class="Other">,</span>
    <span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
  <dd>
    
    <p>Iterates over [optional <tt class="docutils literal"><span class="pre"><span class="Identifier">eat</span></span></tt>] <tt class="docutils literal"><span class="pre"><span class="Identifier">delim</span></span></tt>-delimited slices in MemFile <tt class="docutils literal"><span class="pre"><span class="Identifier">mfile</span></span></tt>.</p>
<p>Default parameters parse lines ending in either Unix(\l) or Windows(\r\l) style on on a line-by-line basis.  I.e., not every line needs the same ending. Unlike readLine(File) &amp; lines(File), archaic MacOS9 \r-delimited lines are not supported as a third option for each line.  Such archaic MacOS9 files can be handled by passing delim='\r', eat='\0', though.</p>
<p>Delimiters are not part of the returned slice.  A final, unterminated line or record is returned just like any other.</p>
<p>Non-default delimiters can be passed to allow iteration over other sorts of &quot;line-like&quot; variable length records.  Pass eat='\0' to be strictly <tt class="docutils literal"><span class="pre"><span class="Identifier">delim</span></span></tt>-delimited. (Eating an optional prefix equal to '\0' is not supported.)</p>
<p>This zero copy, memchr-limited interface is probably the fastest way to iterate over line-like records in a file.  However, returned (data,size) objects are not Nim strings, bounds checked Nim arrays, or even terminated C strings.  So, care is required to access the data (e.g., think C mem* functions, not str* functions).</p>
<p>Example:</p>
<p><pre class="listing"><span class="Keyword">var</span> <span class="Identifier">count</span> <span class="Operator">=</span> <span class="DecNumber">0</span>
<span class="Keyword">for</span> <span class="Identifier">slice</span> <span class="Keyword">in</span> <span class="Identifier">memSlices</span><span class="Punctuation">(</span><span class="Identifier">memfiles</span><span class="Operator">.</span><span class="Identifier">open</span><span class="Punctuation">(</span><span class="StringLit">&quot;foo&quot;</span><span class="Punctuation">)</span><span class="Punctuation">)</span><span class="Punctuation">:</span>
  <span class="Keyword">if</span> <span class="Identifier">slice</span><span class="Operator">.</span><span class="Identifier">size</span> <span class="Operator">&gt;</span> <span class="DecNumber">0</span> <span class="Keyword">and</span> <span class="Keyword">cast</span><span class="Punctuation">[</span><span class="Identifier">cstring</span><span class="Punctuation">]</span><span class="Punctuation">(</span><span class="Identifier">slice</span><span class="Operator">.</span><span class="Identifier">data</span><span class="Punctuation">)</span><span class="Punctuation">[</span><span class="DecNumber">0</span><span class="Punctuation">]</span> <span class="Operator">!=</span> <span class="CharLit">'#'</span><span class="Punctuation">:</span>
    <span class="Identifier">inc</span><span class="Punctuation">(</span><span class="Identifier">count</span><span class="Punctuation">)</span>
<span class="Identifier">echo</span> <span class="Identifier">count</span></pre></p>

    <a href="https://github.com/nim-lang/Nim/tree/devel/lib/pure/memfiles.nim#L420" class="link-seesrc" target="_blank">Source</a>&nbsp;&nbsp;
<a href="https://github.com/nim-lang/Nim/edit/devel/lib/pure/memfiles.nim#L420" class="link-seesrc" target="_blank" >Edit</a>&nbsp;&nbsp;

  </dd>
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