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139 lines
3.9 KiB
Lua
139 lines
3.9 KiB
Lua
-- eLua reference manual - pack
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data_en =
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{
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-- Title
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title = "eLua reference manual - pack",
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-- Menu name
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menu_name = "pack",
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-- Overview
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overview = [[This module allows for arbitrary packing of data into Lua strings and unpacking data from Lua strings. In this way, a string can be used to store data in a platform-independent
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manner. It is based on the ^http://www.tecgraf.puc-rio.br/~~lhf/ftp/lua/#lpack^lpack^ module from Luiz Henrique de Figueiredo (with some minor tweaks). </p>
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<p>Both methods of this module (@#pack@pack@ and @#unpack@unpack@) use a $format string$ to describe how to pack/unpack the data. The format string contains one or more $data specifiers$, each
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data specifier is applied to a single variable that must be packed/unpacked. The data specifier has the following general format:</p>
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~[endianness]<<format specifier>>[count]~
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<p>where:</p>
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<ul>
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<li>$endianness$ is an optional endian flags that specifies how the numbers that are to be packed/unpacked are stored in memory. It can be either:
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<ol>
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<li>$'<<'$ for little endian.</li>
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<li>$'>>'$ for big endian.</li>
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<li>$'='$ for native endian (the platform's endian order, default).</li>
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</ol></li>
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<li>$format specifier$ describes what kind of variable will be packed/unpacked. $The format specifier is case-sensitive$. The possible values of this parameter are summarized in the table below:
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<p/>
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<table class="table_center" style="margin-top: 4px; margin-bottom: 4px;">
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<tbody>
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<tr>
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<th>Format specifier</th>
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<th>Corresponding variable type</th>
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</tr>
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<tr>
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<td>'z'</td>
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<td>zero-terminated string</td>
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</tr>
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<tr>
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<td>'p' </td>
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<td>string preceded by length byte</td>
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</tr>
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<tr>
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<td>'P' </td>
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<td>string preceded by length word</td>
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</tr>
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<tr>
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<td>'a' </td>
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<td>string preceded by length size_t</td>
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</tr>
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<tr>
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<td>'A' </td>
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<td>string</td>
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</tr>
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<tr>
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<td>'f' </td>
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<td>float</td>
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</tr>
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<tr>
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<td>'d' </td>
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<td>double</td>
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</tr>
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<tr>
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<td>'n' </td>
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<td>Lua number</td>
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</tr>
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<tr>
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<td>'c' </td>
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<td>char</td>
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</tr>
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<tr>
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<td>'b' </td>
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<td>byte = unsigned char</td>
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</tr>
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<tr>
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<td>'h' </td>
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<td>short</td>
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</tr>
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<tr>
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<td>'H' </td>
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<td>unsigned short</td>
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</tr>
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<tr>
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<td>'i' </td>
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<td>int</td>
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</tr>
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<tr>
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<td>'I' </td>
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<td>unsigned int</td>
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</tr>
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<tr>
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<td>'l' </td>
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<td>long</td>
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</tr>
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<tr>
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<td>'L' </td>
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<td>unsigned long</td>
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</tr>
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</tbody>
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</table></li>
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<li>$count$ is an optional counter for the $format specifier$. For example, $i5$ instructs the code to pack/unpack 5 integer variables, as opposed to $i$ that specifies a
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single integer variable.</li>
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</ul><p>]],
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-- Functions
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funcs =
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{
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{ sig = "packed = #pack.pack#( format, val1, val2, ..., valn )",
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desc = "Packs variables in a string.",
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args =
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{
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"$format$ - format specifier (as described @#overview@here@).",
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"$val1$ - first variable to pack.",
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"$val2$ - second variable to pack.",
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"$valn$ - nth variable to pack.",
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},
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ret = "$packed$ - a string containing the packed representation of all variables according to the format."
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},
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{ sig = "nextpos, val1, val2, ..., valn = #pack.unpack#( string, format, [ init ] )",
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desc = "Unpacks a string",
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args =
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{
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"$string$ - the string to unpack.",
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"$format$ - format specifier (as described @#overview@here@).",
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"$init$ - $(optional)$ marks where in $string$ the unpacking should start (1 if not specified)."
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},
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ret =
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{
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"$nextpos$ - the position in the string after unpacking.",
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"$val1$ - the first unpacked value.",
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"$val2$ - the second unpacked value.",
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"$valn$ - the nth unpacked value."
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}
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}
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},
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}
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data_pt = data_en
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