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<title>Batteries user guide : Batteries.Marshal</title>
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<h1>Module <a href="type_Batteries.Marshal.html">Batteries.Marshal</a></h1>
<pre><span class="keyword">module</span> Marshal: <code class="type">BatMarshal</code></pre><hr width="100%">
<pre><span id="TYPEextern_flags"><span class="keyword">type</span> <code class="type"></code>extern_flags</span> = <code class="type">Marshal.extern_flags</code> = </pre><table class="typetable">
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTextern_flags.No_sharing"><span class="constructor">No_sharing</span></span></code></td>
<td class="typefieldcomment" align="left" valign="top" ><code>(*</code></td><td class="typefieldcomment" align="left" valign="top" >Don't preserve sharing</td><td class="typefieldcomment" align="left" valign="bottom" ><code>*)</code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTextern_flags.Closures"><span class="constructor">Closures</span></span></code></td>
<td class="typefieldcomment" align="left" valign="top" ><code>(*</code></td><td class="typefieldcomment" align="left" valign="top" >Send function closures</td><td class="typefieldcomment" align="left" valign="bottom" ><code>*)</code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTextern_flags.Compat_32"><span class="constructor">Compat_32</span></span></code></td>
<td class="typefieldcomment" align="left" valign="top" ><code>(*</code></td><td class="typefieldcomment" align="left" valign="top" >Ensure 32-bit compatibility</td><td class="typefieldcomment" align="left" valign="bottom" ><code>*)</code></td>
</tr></table>
<div class="info ">
The flags to the <code class="code"><span class="constructor">Marshal</span>.to_*</code> functions below.<br>
</div>
<pre><span id="VALoutput"><span class="keyword">val</span> output</span> : <code class="type">'b <a href="BatInnerIO.html#TYPEoutput">BatInnerIO.output</a> -> ?sharing:bool -> ?closures:bool -> 'a -> unit</code></pre><div class="info ">
<code class="code">output out v</code> writes the representation of <code class="code">v</code> on <code class="code">chan</code>.<br>
</div>
<div class="param_info"><code class="code">sharing</code> : If <code class="code"><span class="keyword">true</span></code> (default value), circularities
and sharing inside the value <code class="code">v</code> are detected and preserved
in the sequence of bytes produced. In particular, this
guarantees that marshaling always terminates. Sharing
between values marshaled by successive calls to
<code class="code">output</code> is not detected, though. If <code class="code"><span class="keyword">false</span></code>, sharing is ignored.
This results in faster marshaling if <code class="code">v</code> contains no shared
substructures, but may cause slower marshaling and larger
byte representations if <code class="code">v</code> actually contains sharing,
or even non-termination if <code class="code">v</code> contains cycles.</div>
<div class="param_info"><code class="code">closures</code> : If <code class="code"><span class="keyword">false</span></code> (default value) marshaling fails when
it encounters a functional value inside <code class="code">v</code>: only ``pure'' data
structures, containing neither functions nor objects, can safely
be transmitted between different programs. If <code class="code"><span class="keyword">true</span></code>, functional
values will be marshaled as a position in the code of the
program. In this case, the output of marshaling can only be read
back in processes that run exactly the same program, with
exactly the same compiled code. (This is checked at
un-marshaling time, using an MD5 digest of the code transmitted
along with the code position.)</div>
<pre><span id="VALto_string"><span class="keyword">val</span> to_string</span> : <code class="type">'a -> <a href="BatMarshal.html#TYPEextern_flags">extern_flags</a> list -> string</code></pre><div class="info ">
<code class="code"><span class="constructor">Marshal</span>.to_string v flags</code> returns a string containing
the representation of <code class="code">v</code> as a sequence of bytes.
The <code class="code">flags</code> argument has the same meaning as for
<code class="code"><span class="constructor">Marshal</span>.to_channel</code>.<br>
</div>
<pre><span id="VALto_buffer"><span class="keyword">val</span> to_buffer</span> : <code class="type">string -> int -> int -> 'a -> <a href="BatMarshal.html#TYPEextern_flags">extern_flags</a> list -> int</code></pre><div class="info ">
<code class="code"><span class="constructor">Marshal</span>.to_buffer buff ofs len v flags</code> marshals the value <code class="code">v</code>,
storing its byte representation in the string <code class="code">buff</code>,
starting at character number <code class="code">ofs</code>, and writing at most
<code class="code">len</code> characters. It returns the number of characters
actually written to the string. If the byte representation
of <code class="code">v</code> does not fit in <code class="code">len</code> characters, the exception <code class="code"><span class="constructor">Failure</span></code>
is raised.<br>
</div>
<pre><span id="VALinput"><span class="keyword">val</span> input</span> : <code class="type"><a href="BatInnerIO.html#TYPEinput">BatInnerIO.input</a> -> 'a</code></pre><div class="info ">
<code class="code">input inp</code> reads from <code class="code">inp</code> the
byte representation of a structured value, as produced by
one of the <code class="code"><span class="constructor">Marshal</span>.to_*</code> functions, and reconstructs and
returns the corresponding value.<br>
</div>
<pre><span id="VALfrom_string"><span class="keyword">val</span> from_string</span> : <code class="type">string -> int -> 'a</code></pre><div class="info ">
<code class="code"><span class="constructor">Marshal</span>.from_string buff ofs</code> unmarshals a structured value
like <code class="code"><span class="constructor">Marshal</span>.from_channel</code> does, except that the byte
representation is not read from a channel, but taken from
the string <code class="code">buff</code>, starting at position <code class="code">ofs</code>.<br>
</div>
<pre><span id="VALheader_size"><span class="keyword">val</span> header_size</span> : <code class="type">int</code></pre><div class="info ">
The bytes representing a marshaled value are composed of
a fixed-size header and a variable-sized data part,
whose size can be determined from the header.
<code class="code"><span class="constructor">Marshal</span>.header_size</code> is the size, in characters, of the header.
<code class="code"><span class="constructor">Marshal</span>.data_size</code><code class="code"> buff ofs</code> is the size, in characters,
of the data part, assuming a valid header is stored in
<code class="code">buff</code> starting at position <code class="code">ofs</code>.
Finally, <code class="code"><span class="constructor">Marshal</span>.total_size</code><code class="code"> buff ofs</code> is the total size,
in characters, of the marshaled value.
Both <code class="code"><span class="constructor">Marshal</span>.data_size</code> and <code class="code"><span class="constructor">Marshal</span>.total_size</code> raise <code class="code"><span class="constructor">Failure</span></code>
if <code class="code">buff</code>, <code class="code">ofs</code> does not contain a valid header.
<p>
To read the byte representation of a marshaled value into
a string buffer, the program needs to read first
<code class="code"><span class="constructor">Marshal</span>.header_size</code> characters into the buffer,
then determine the length of the remainder of the
representation using <code class="code"><span class="constructor">Marshal</span>.data_size</code>,
make sure the buffer is large enough to hold the remaining
data, then read it, and finally call <code class="code"><span class="constructor">Marshal</span>.from_string</code>
to unmarshal the value.<br>
</div>
<pre><span id="VALdata_size"><span class="keyword">val</span> data_size</span> : <code class="type">string -> int -> int</code></pre><div class="info ">
See <code class="code"><span class="constructor">Marshal</span>.header_size</code>.<br>
</div>
<pre><span id="VALtotal_size"><span class="keyword">val</span> total_size</span> : <code class="type">string -> int -> int</code></pre><div class="info ">
See <code class="code"><span class="constructor">Marshal</span>.header_size</code>.<br>
</div>
<br>
<h6 id="6_Deprecated">Deprecated</h6><br>
<pre><span id="VALto_channel"><span class="keyword">val</span> to_channel</span> : <code class="type">'b <a href="BatInnerIO.html#TYPEoutput">BatInnerIO.output</a> -> 'a -> <a href="BatMarshal.html#TYPEextern_flags">extern_flags</a> list -> unit</code></pre><div class="info ">
<span class="warning">Deprecated.</span>Use <a href="BatMarshal.html#VALoutput"><code class="code"><span class="constructor">BatMarshal</span>.output</code></a> instead<br>
</div>
<pre><span id="VALfrom_channel"><span class="keyword">val</span> from_channel</span> : <code class="type"><a href="BatInnerIO.html#TYPEinput">BatInnerIO.input</a> -> 'a</code></pre><div class="info ">
<span class="warning">Deprecated.</span>Use <a href="BatMarshal.html#VALinput"><code class="code"><span class="constructor">BatMarshal</span>.input</code></a> instead<br>
</div>
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