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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/System-IO-MMap.html">Source</a></li><li><a href="index.html">Contents</a></li><li><a href="doc-index.html">Index</a></li></ul><p class="caption">mmap-0.5.9: Memory mapped files for POSIX and Windows</p></div><div id="content"><div id="module-header"><table class="info"><tr><th valign="top">Copyright</th><td>(c) Gracjan Polak 2009</td></tr><tr><th>License</th><td>BSD-style</td></tr><tr><th>Stability</th><td>experimental</td></tr><tr><th>Portability</th><td>portable</td></tr><tr><th>Safe Haskell</th><td>None</td></tr><tr><th>Language</th><td>Haskell98</td></tr></table><p class="caption">System.IO.MMap</p></div><div id="table-of-contents"><p class="caption">Contents</p><ul><li><a href="#g:1">Mapping mode</a></li><li><a href="#g:2">Memory mapped files strict interface</a></li><li><a href="#g:3">Memory mapped files lazy interface</a></li></ul></div><div id="description"><p class="caption">Description</p><div class="doc"><p>This library provides a wrapper to mmap(2) or MapViewOfFile,
allowing files or devices to be lazily loaded into memory as strict
or lazy ByteStrings, ForeignPtrs or plain Ptrs, using the virtual
memory subsystem to do on-demand loading. Modifications are also
supported.</p></div></div><div id="synopsis"><p id="control.syn" class="caption expander" onclick="toggleSection('syn')">Synopsis</p><ul id="section.syn" class="hide" onclick="toggleSection('syn')"><li class="src short"><span class="keyword">data</span> <a href="#t:Mode">Mode</a><ul class="subs"><li>= <a href="#v:ReadOnly">ReadOnly</a></li><li>| <a href="#v:ReadWrite">ReadWrite</a></li><li>| <a href="#v:WriteCopy">WriteCopy</a></li><li>| <a href="#v:ReadWriteEx">ReadWriteEx</a></li></ul></li><li class="src short"><a href="#v:mmapFilePtr">mmapFilePtr</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>) -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-Ptr.html#t:Ptr">Ptr</a> a, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>)</li><li class="src short"><a href="#v:mmapWithFilePtr">mmapWithFilePtr</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>) -> ((<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-Ptr.html#t:Ptr">Ptr</a> (), <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>) -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> a) -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> a</li><li class="src short"><a href="#v:mmapFileForeignPtr">mmapFileForeignPtr</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>) -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-ForeignPtr.html#t:ForeignPtr">ForeignPtr</a> a, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>)</li><li class="src short"><a href="#v:mmapFileByteString">mmapFileByteString</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>) -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> <a href="file:///usr/share/doc/ghc-doc/html/libraries/bytestring-0.10.8.1/Data-ByteString.html#t:ByteString">ByteString</a></li><li class="src short"><a href="#v:munmapFilePtr">munmapFilePtr</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-Ptr.html#t:Ptr">Ptr</a> a -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> ()</li><li class="src short"><a href="#v:mmapFileForeignPtrLazy">mmapFileForeignPtrLazy</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>) -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> [(<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-ForeignPtr.html#t:ForeignPtr">ForeignPtr</a> a, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>)]</li><li class="src short"><a href="#v:mmapFileByteStringLazy">mmapFileByteStringLazy</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>) -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> <a href="file:///usr/share/doc/ghc-doc/html/libraries/bytestring-0.10.8.1/Data-ByteString-Lazy.html#t:ByteString">ByteString</a></li></ul></div><div id="interface"><h1>Documentation</h1><div class="doc"><p>This module is an interface to <code>mmap(2)</code> system call under POSIX
(Unix, Linux, Mac OS X) and <code>CreateFileMapping</code>, <code>MapViewOfFile</code> under
Windows.</p><p>We can consider mmap as lazy IO pushed into the virtual memory
subsystem.</p><p>It is only safe to mmap a file if you know you are the sole
user. Otherwise referential transparency may be or may be not
compromised. Sadly semantics differ much between operating systems.</p><p>In case of IO errors all function use <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-C-Error.html#v:throwErrno">throwErrno</a></code> or <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-C-Error.html#v:throwErrnoPath">throwErrnoPath</a></code>.</p><p>In case of <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-ForeignPtr.html#t:ForeignPtr">ForeignPtr</a></code> or <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/bytestring-0.10.8.1/Data-ByteString.html#t:ByteString">ByteString</a></code> functions the storage
manager is used to free the mapped memory. When the garbage
collector notices there are no further references to the mapped
memory, a call to <code>munmap</code> is made. It is not necessary to do this
yourself. In tight memory situations it may be profitable to use
<code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-Mem.html#v:performGC">performGC</a></code> or <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-ForeignPtr.html#v:finalizeForeignPtr">finalizeForeignPtr</a></code> to force an unmap
action. You can also use <code><a href="System-IO-MMap.html#v:mmapWithFilePtr">mmapWithFilePtr</a></code> that uses scope based
resource allocation.</p><p>To free resources returned as Ptr use <code><a href="System-IO-MMap.html#v:munmapFilePtr">munmapFilePtr</a></code>.</p><p>For modes <code><a href="System-IO-MMap.html#v:ReadOnly">ReadOnly</a></code>, <code><a href="System-IO-MMap.html#v:ReadWrite">ReadWrite</a></code> and <code><a href="System-IO-MMap.html#v:WriteCopy">WriteCopy</a></code> file must exist
before mapping it into memory. It also needs to have correct
permissions for reading and/or writing (depending on mode). In
<code><a href="System-IO-MMap.html#v:ReadWriteEx">ReadWriteEx</a></code> the file will be created with default permissions if
it does not exist.</p><p>If mode is <code><a href="System-IO-MMap.html#v:ReadWrite">ReadWrite</a></code>, <code><a href="System-IO-MMap.html#v:ReadWriteEx">ReadWriteEx</a></code> or <code><a href="System-IO-MMap.html#v:WriteCopy">WriteCopy</a></code> the returned
memory region may be written to with <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-Storable.html#v:poke">poke</a></code> and
friends. In <code><a href="System-IO-MMap.html#v:WriteCopy">WriteCopy</a></code> mode changes will not be written to disk.
It is an error to modify mapped memory in <code><a href="System-IO-MMap.html#v:ReadOnly">ReadOnly</a></code> mode. If is
undefined if and how changes from external changes affect your
mmapped regions, they may reflect in your memory or may not and
this note applies equally to all modes.</p><p>Range specified may be <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#v:Nothing">Nothing</a></code>, in this case whole file will be
mapped. Otherwise range should be 'Just (offset,size)' where
offsets is the beginning byte of file region to map and size tells
mapping length. There are no alignment requirements. Returned Ptr or
ForeignPtr will be aligned to page size boundary and you'll be
given offset to your data. Both <code>offset</code> and <code>size</code> must be
nonnegative. Sum <code>offset + size</code> should not be greater than file
length, except in <code><a href="System-IO-MMap.html#v:ReadWriteEx">ReadWriteEx</a></code> mode when file will be extended to
cover whole range. We do allow <code>size</code> to be 0 and we do mmap files
of 0 length. If your offset is 0 you are guaranteed to receive page
aligned pointer back. You are required to give explicit range in
case of <code><a href="System-IO-MMap.html#v:ReadWriteEx">ReadWriteEx</a></code> even if the file exists.</p><p>File extension in <code><a href="System-IO-MMap.html#v:ReadWriteEx">ReadWriteEx</a></code> mode seems to use sparse files
whenever supported by oprating system and therefore returns
immediatelly as postpones real block allocation for later.</p><p>For more details about mmap and its consequences see:</p><ul><li><a href="http://opengroup.org/onlinepubs/009695399/functions/mmap.html">http://opengroup.org/onlinepubs/009695399/functions/mmap.html</a></li><li><a href="http://www.gnu.org/software/libc/manual/html_node/Memory_002dmapped-I_002fO.html">http://www.gnu.org/software/libc/manual/html_node/Memory_002dmapped-I_002fO.html</a></li><li><a href="http://msdn2.microsoft.com/en-us/library/aa366781(VS.85).aspx">http://msdn2.microsoft.com/en-us/library/aa366781(VS.85).aspx</a></li></ul><p>Questions and Answers</p><ul><li>Q: What happens if somebody writes to my mmapped file? A:
Undefined. System is free to not synchronize write system call and
mmap so nothing is sure. So this might be reflected in your memory
or not. This applies even in <code><a href="System-IO-MMap.html#v:WriteCopy">WriteCopy</a></code> mode.</li><li>Q: What happens if I map <code><a href="System-IO-MMap.html#v:ReadWrite">ReadWrite</a></code> and change memory? A: After
some time in will be written to disk. It is unspecified when this
happens.</li><li>Q: What if somebody removes my file? A: Undefined. File with
mmapped region is treated by system as open file. Removing such
file works the same way as removing open file and different systems
have different ideas what to do in such case.</li><li>Q: Why can't I open my file for writting after mmaping it? A:
File needs to be unmapped first. Either make sure you don't
reference memory mapped regions and force garbage collection (this
is hard to do) or better yet use mmaping with explicit memory
management.</li><li>Q: Can I map region after end of file? A: You need to use
<code><a href="System-IO-MMap.html#v:ReadWriteEx">ReadWriteEx</a></code> mode.</li></ul></div><h1 id="g:1">Mapping mode</h1><div class="top"><p class="src"><span class="keyword">data</span> <a id="t:Mode" class="def">Mode</a> <a href="src/System-IO-MMap.html#Mode" class="link">Source</a> <a href="#t:Mode" class="selflink">#</a></p><div class="doc"><p>Mode of mapping. Four cases are supported.</p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a id="v:ReadOnly" class="def">ReadOnly</a></td><td class="doc"><p>file is mapped read-only, file must
exist</p></td></tr><tr><td class="src"><a id="v:ReadWrite" class="def">ReadWrite</a></td><td class="doc"><p>file is mapped read-write, file must
exist</p></td></tr><tr><td class="src"><a id="v:WriteCopy" class="def">WriteCopy</a></td><td class="doc"><p>file is mapped read-write, but changes
aren't propagated to disk, file must exist</p></td></tr><tr><td class="src"><a id="v:ReadWriteEx" class="def">ReadWriteEx</a></td><td class="doc"><p>file is mapped read-write, if file does
not exist it will be created with default
permissions, region parameter specifies
size, if file size is lower it will be
extended with zeros</p></td></tr></table></div><div class="subs instances"><p id="control.i:Mode" class="caption collapser" onclick="toggleSection('i:Mode')">Instances</p><div id="section.i:Mode" class="show"><table><tr><td class="src clearfix"><span class="inst-left"><span id="control.i:id:Mode:Enum:1" class="instance expander" onclick="toggleSection('i:id:Mode:Enum:1')"></span> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Prelude.html#t:Enum">Enum</a> <a href="System-IO-MMap.html#t:Mode">Mode</a></span> <a href="src/System-IO-MMap.html#line-165" class="link">Source</a> <a href="#t:Mode" class="selflink">#</a></td><td class="doc empty"> </td></tr><tr><td colspan="2"><div id="section.i:id:Mode:Enum:1" class="inst-details hide"><div class="subs methods"><p class="caption">Methods</p><p class="src"><a href="#v:succ">succ</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> <a href="#v:succ" class="selflink">#</a></p><p class="src"><a href="#v:pred">pred</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> <a href="#v:pred" class="selflink">#</a></p><p class="src"><a href="#v:toEnum">toEnum</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> <a href="#v:toEnum" class="selflink">#</a></p><p class="src"><a href="#v:fromEnum">fromEnum</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a> <a href="#v:fromEnum" class="selflink">#</a></p><p class="src"><a href="#v:enumFrom">enumFrom</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> [<a href="System-IO-MMap.html#t:Mode">Mode</a>] <a href="#v:enumFrom" class="selflink">#</a></p><p class="src"><a href="#v:enumFromThen">enumFromThen</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> [<a href="System-IO-MMap.html#t:Mode">Mode</a>] <a href="#v:enumFromThen" class="selflink">#</a></p><p class="src"><a href="#v:enumFromTo">enumFromTo</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> [<a href="System-IO-MMap.html#t:Mode">Mode</a>] <a href="#v:enumFromTo" class="selflink">#</a></p><p class="src"><a href="#v:enumFromThenTo">enumFromThenTo</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> [<a href="System-IO-MMap.html#t:Mode">Mode</a>] <a href="#v:enumFromThenTo" class="selflink">#</a></p></div></div></td></tr><tr><td class="src clearfix"><span class="inst-left"><span id="control.i:id:Mode:Eq:2" class="instance expander" onclick="toggleSection('i:id:Mode:Eq:2')"></span> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Eq.html#t:Eq">Eq</a> <a href="System-IO-MMap.html#t:Mode">Mode</a></span> <a href="src/System-IO-MMap.html#line-165" class="link">Source</a> <a href="#t:Mode" class="selflink">#</a></td><td class="doc empty"> </td></tr><tr><td colspan="2"><div id="section.i:id:Mode:Eq:2" class="inst-details hide"><div class="subs methods"><p class="caption">Methods</p><p class="src"><a href="#v:-61--61-">(==)</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Bool.html#t:Bool">Bool</a> <a href="#v:-61--61-" class="selflink">#</a></p><p class="src"><a href="#v:-47--61-">(/=)</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Bool.html#t:Bool">Bool</a> <a href="#v:-47--61-" class="selflink">#</a></p></div></div></td></tr><tr><td class="src clearfix"><span class="inst-left"><span id="control.i:id:Mode:Ord:3" class="instance expander" onclick="toggleSection('i:id:Mode:Ord:3')"></span> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Ord.html#t:Ord">Ord</a> <a href="System-IO-MMap.html#t:Mode">Mode</a></span> <a href="src/System-IO-MMap.html#line-165" class="link">Source</a> <a href="#t:Mode" class="selflink">#</a></td><td class="doc empty"> </td></tr><tr><td colspan="2"><div id="section.i:id:Mode:Ord:3" class="inst-details hide"><div class="subs methods"><p class="caption">Methods</p><p class="src"><a href="#v:compare">compare</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Ord.html#t:Ordering">Ordering</a> <a href="#v:compare" class="selflink">#</a></p><p class="src"><a href="#v:-60-">(<)</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Bool.html#t:Bool">Bool</a> <a href="#v:-60-" class="selflink">#</a></p><p class="src"><a href="#v:-60--61-">(<=)</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Bool.html#t:Bool">Bool</a> <a href="#v:-60--61-" class="selflink">#</a></p><p class="src"><a href="#v:-62-">(>)</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Bool.html#t:Bool">Bool</a> <a href="#v:-62-" class="selflink">#</a></p><p class="src"><a href="#v:-62--61-">(>=)</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Bool.html#t:Bool">Bool</a> <a href="#v:-62--61-" class="selflink">#</a></p><p class="src"><a href="#v:max">max</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> <a href="#v:max" class="selflink">#</a></p><p class="src"><a href="#v:min">min</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> <a href="#v:min" class="selflink">#</a></p></div></div></td></tr><tr><td class="src clearfix"><span class="inst-left"><span id="control.i:id:Mode:Read:4" class="instance expander" onclick="toggleSection('i:id:Mode:Read:4')"></span> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Text-Read.html#t:Read">Read</a> <a href="System-IO-MMap.html#t:Mode">Mode</a></span> <a href="src/System-IO-MMap.html#line-165" class="link">Source</a> <a href="#t:Mode" class="selflink">#</a></td><td class="doc empty"> </td></tr><tr><td colspan="2"><div id="section.i:id:Mode:Read:4" class="inst-details hide"><div class="subs methods"><p class="caption">Methods</p><p class="src"><a href="#v:readsPrec">readsPrec</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Text-ParserCombinators-ReadP.html#t:ReadS">ReadS</a> <a href="System-IO-MMap.html#t:Mode">Mode</a> <a href="#v:readsPrec" class="selflink">#</a></p><p class="src"><a href="#v:readList">readList</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Text-ParserCombinators-ReadP.html#t:ReadS">ReadS</a> [<a href="System-IO-MMap.html#t:Mode">Mode</a>] <a href="#v:readList" class="selflink">#</a></p><p class="src"><a href="#v:readPrec">readPrec</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Text-ParserCombinators-ReadPrec.html#t:ReadPrec">ReadPrec</a> <a href="System-IO-MMap.html#t:Mode">Mode</a> <a href="#v:readPrec" class="selflink">#</a></p><p class="src"><a href="#v:readListPrec">readListPrec</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Text-ParserCombinators-ReadPrec.html#t:ReadPrec">ReadPrec</a> [<a href="System-IO-MMap.html#t:Mode">Mode</a>] <a href="#v:readListPrec" class="selflink">#</a></p></div></div></td></tr><tr><td class="src clearfix"><span class="inst-left"><span id="control.i:id:Mode:Show:5" class="instance expander" onclick="toggleSection('i:id:Mode:Show:5')"></span> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Text-Show.html#t:Show">Show</a> <a href="System-IO-MMap.html#t:Mode">Mode</a></span> <a href="src/System-IO-MMap.html#line-165" class="link">Source</a> <a href="#t:Mode" class="selflink">#</a></td><td class="doc empty"> </td></tr><tr><td colspan="2"><div id="section.i:id:Mode:Show:5" class="inst-details hide"><div class="subs methods"><p class="caption">Methods</p><p class="src"><a href="#v:showsPrec">showsPrec</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a> -> <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Text-Show.html#t:ShowS">ShowS</a> <a href="#v:showsPrec" class="selflink">#</a></p><p class="src"><a href="#v:show">show</a> :: <a href="System-IO-MMap.html#t:Mode">Mode</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-String.html#t:String">String</a> <a href="#v:show" class="selflink">#</a></p><p class="src"><a href="#v:showList">showList</a> :: [<a href="System-IO-MMap.html#t:Mode">Mode</a>] -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Text-Show.html#t:ShowS">ShowS</a> <a href="#v:showList" class="selflink">#</a></p></div></div></td></tr></table></div></div></div><h1 id="g:2">Memory mapped files strict interface</h1><div class="top"><p class="src"><a id="v:mmapFilePtr" class="def">mmapFilePtr</a> <a href="src/System-IO-MMap.html#mmapFilePtr" class="link">Source</a> <a href="#v:mmapFilePtr" class="selflink">#</a></p><div class="subs arguments"><p class="caption">Arguments</p><table><tr><td class="src">:: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a></td><td class="doc"><p>name of file to mmap</p></td></tr><tr><td class="src">-> <a href="System-IO-MMap.html#t:Mode">Mode</a></td><td class="doc"><p>access mode</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>)</td><td class="doc"><p>range to map, maps whole file if Nothing</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-Ptr.html#t:Ptr">Ptr</a> a, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>)</td><td class="doc"><p>(ptr,rawsize,offset,size)</p></td></tr></table></div><div class="doc"><p>The <code><a href="System-IO-MMap.html#v:mmapFilePtr">mmapFilePtr</a></code> function maps a file or device into memory,
returning a tuple <code>(ptr,rawsize,offset,size)</code> where:</p><ul><li><code>ptr</code> is pointer to mmapped region</li><li><code>rawsize</code> is length (in bytes) of mapped data, rawsize might be
greater than size because of alignment</li><li><code>offset</code> tell where your data lives: <code>plusPtr ptr offset</code></li><li><code>size</code> your data length (in bytes)</li></ul><p>If <code><a href="System-IO-MMap.html#v:mmapFilePtr">mmapFilePtr</a></code> fails for some reason, a <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-C-Error.html#v:throwErrno">throwErrno</a></code> is used.</p><p>Use <code>munmapFilePtr ptr rawsize</code> to unmap memory.</p><p>Memory mapped files will behave as if they were read lazily
pages from the file will be loaded into memory on demand.</p></div></div><div class="top"><p class="src"><a id="v:mmapWithFilePtr" class="def">mmapWithFilePtr</a> <a href="src/System-IO-MMap.html#mmapWithFilePtr" class="link">Source</a> <a href="#v:mmapWithFilePtr" class="selflink">#</a></p><div class="subs arguments"><p class="caption">Arguments</p><table><tr><td class="src">:: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a></td><td class="doc"><p>name of file to mmap</p></td></tr><tr><td class="src">-> <a href="System-IO-MMap.html#t:Mode">Mode</a></td><td class="doc"><p>access mode</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>)</td><td class="doc"><p>range to map, maps whole file if Nothing</p></td></tr><tr><td class="src">-> ((<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-Ptr.html#t:Ptr">Ptr</a> (), <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>) -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> a)</td><td class="doc"><p>action to run</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> a</td><td class="doc"><p>result of action</p></td></tr></table></div><div class="doc"><p>Memory map region of file using autounmap semantics. See
<code><a href="System-IO-MMap.html#v:mmapFilePtr">mmapFilePtr</a></code> for description of parameters. The <code>action</code> will be
executed with tuple <code>(ptr,size)</code> as single argument. This is the
pointer to mapped data already adjusted and size of requested
region. Return value is that of action.</p></div></div><div class="top"><p class="src"><a id="v:mmapFileForeignPtr" class="def">mmapFileForeignPtr</a> <a href="src/System-IO-MMap.html#mmapFileForeignPtr" class="link">Source</a> <a href="#v:mmapFileForeignPtr" class="selflink">#</a></p><div class="subs arguments"><p class="caption">Arguments</p><table><tr><td class="src">:: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a></td><td class="doc"><p>name of file to map</p></td></tr><tr><td class="src">-> <a href="System-IO-MMap.html#t:Mode">Mode</a></td><td class="doc"><p>access mode</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>)</td><td class="doc"><p>range to map, maps whole file if Nothing</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-ForeignPtr.html#t:ForeignPtr">ForeignPtr</a> a, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>)</td><td class="doc"><p>foreign pointer to beginning of raw region,
offset to your data and size of your data</p></td></tr></table></div><div class="doc"><p>Maps region of file and returns it as <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-ForeignPtr.html#t:ForeignPtr">ForeignPtr</a></code>. See <code><a href="System-IO-MMap.html#v:mmapFilePtr">mmapFilePtr</a></code> for details.</p></div></div><div class="top"><p class="src"><a id="v:mmapFileByteString" class="def">mmapFileByteString</a> <a href="src/System-IO-MMap.html#mmapFileByteString" class="link">Source</a> <a href="#v:mmapFileByteString" class="selflink">#</a></p><div class="subs arguments"><p class="caption">Arguments</p><table><tr><td class="src">:: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a></td><td class="doc"><p>name of file to map</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>)</td><td class="doc"><p>range to map, maps whole file if Nothing</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> <a href="file:///usr/share/doc/ghc-doc/html/libraries/bytestring-0.10.8.1/Data-ByteString.html#t:ByteString">ByteString</a></td><td class="doc"><p>bytestring with file contents</p></td></tr></table></div><div class="doc"><p>Maps region of file and returns it as <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/bytestring-0.10.8.1/Data-ByteString.html#t:ByteString">ByteString</a></code>. File is
mapped in in <code><a href="System-IO-MMap.html#v:ReadOnly">ReadOnly</a></code> mode. See <code><a href="System-IO-MMap.html#v:mmapFilePtr">mmapFilePtr</a></code> for details.</p></div></div><div class="top"><p class="src"><a id="v:munmapFilePtr" class="def">munmapFilePtr</a> <a href="src/System-IO-MMap.html#munmapFilePtr" class="link">Source</a> <a href="#v:munmapFilePtr" class="selflink">#</a></p><div class="subs arguments"><p class="caption">Arguments</p><table><tr><td class="src">:: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-Ptr.html#t:Ptr">Ptr</a> a</td><td class="doc"><p>pointer</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a></td><td class="doc"><p>rawsize</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> ()</td><td class="doc empty"> </td></tr></table></div><div class="doc"><p>Unmaps memory region. As parameters use values marked as ptr and
rawsize in description of <code><a href="System-IO-MMap.html#v:mmapFilePtr">mmapFilePtr</a></code>.</p></div></div><h1 id="g:3">Memory mapped files lazy interface</h1><div class="top"><p class="src"><a id="v:mmapFileForeignPtrLazy" class="def">mmapFileForeignPtrLazy</a> <a href="src/System-IO-MMap.html#mmapFileForeignPtrLazy" class="link">Source</a> <a href="#v:mmapFileForeignPtrLazy" class="selflink">#</a></p><div class="subs arguments"><p class="caption">Arguments</p><table><tr><td class="src">:: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a></td><td class="doc"><p>name of file to mmap</p></td></tr><tr><td class="src">-> <a href="System-IO-MMap.html#t:Mode">Mode</a></td><td class="doc"><p>access mode</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>)</td><td class="doc"><p>range to map, maps whole file if Nothing</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> [(<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Foreign-ForeignPtr.html#t:ForeignPtr">ForeignPtr</a> a, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a>)]</td><td class="doc"><p>(ptr,offset,size)</p></td></tr></table></div><div class="doc"><p>The <code><a href="System-IO-MMap.html#v:mmapFileForeignPtrLazy">mmapFileForeignPtrLazy</a></code> function maps a file or device into
memory, returning a list of tuples with the same meaning as in
function <code><a href="System-IO-MMap.html#v:mmapFileForeignPtr">mmapFileForeignPtr</a></code>.</p><p>Chunks are really mapped into memory at the first inspection of a
chunk. They are kept in memory while they are referenced, garbage
collector takes care of the later.</p></div></div><div class="top"><p class="src"><a id="v:mmapFileByteStringLazy" class="def">mmapFileByteStringLazy</a> <a href="src/System-IO-MMap.html#mmapFileByteStringLazy" class="link">Source</a> <a href="#v:mmapFileByteStringLazy" class="selflink">#</a></p><div class="subs arguments"><p class="caption">Arguments</p><table><tr><td class="src">:: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:FilePath">FilePath</a></td><td class="doc"><p>name of file to map</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int64">Int64</a>)</td><td class="doc"><p>range to map, maps whole file if Nothing</p></td></tr><tr><td class="src">-> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> <a href="file:///usr/share/doc/ghc-doc/html/libraries/bytestring-0.10.8.1/Data-ByteString-Lazy.html#t:ByteString">ByteString</a></td><td class="doc"><p>bytestring with file content</p></td></tr></table></div><div class="doc"><p>Maps region of file and returns it as <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/bytestring-0.10.8.1/Data-ByteString-Lazy.html#t:ByteString">ByteString</a></code>. File is
mapped in in <code><a href="System-IO-MMap.html#v:ReadOnly">ReadOnly</a></code> mode. See <code><a href="System-IO-MMap.html#v:mmapFileForeignPtrLazy">mmapFileForeignPtrLazy</a></code> for
details.</p></div></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.17.3</p></div></body></html>
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