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<title>12.17.1 Packer Objects
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<H2><A NAME=
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<tt class=
"class">Packer
</tt> instances have the following methods:
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4165' xml:id='l2h-
4165'
class=
"method">get_buffer
</tt></b>(
</nobr></td>
<td><var></var>)
</td></tr></table></dt>
Returns the current pack buffer as a string.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4166' xml:id='l2h-
4166'
class=
"method">reset
</tt></b>(
</nobr></td>
<td><var></var>)
</td></tr></table></dt>
Resets the pack buffer to the empty string.
In general, you can pack any of the most common XDR data types by
calling the appropriate
<code>pack_
<var>type
</var>()
</code> method. Each method
takes a single argument, the value to pack. The following simple data
type packing methods are supported:
<tt class=
"method">pack_uint()
</tt>,
<tt class=
"method">pack_int()
</tt>,
<tt class=
"method">pack_enum()
</tt>,
<tt class=
"method">pack_bool()
</tt>,
<tt class=
"method">pack_uhyper()
</tt>, and
<tt class=
"method">pack_hyper()
</tt>.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4167' xml:id='l2h-
4167'
class=
"method">pack_float
</tt></b>(
</nobr></td>
<td><var>value
</var>)
</td></tr></table></dt>
Packs the single-precision floating point number
<var>value
</var>.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4168' xml:id='l2h-
4168'
class=
"method">pack_double
</tt></b>(
</nobr></td>
<td><var>value
</var>)
</td></tr></table></dt>
Packs the double-precision floating point number
<var>value
</var>.
The following methods support packing strings, bytes, and opaque data:
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4169' xml:id='l2h-
4169'
class=
"method">pack_fstring
</tt></b>(
</nobr></td>
<td><var>n, s
</var>)
</td></tr></table></dt>
Packs a fixed length string,
<var>s
</var>.
<var>n
</var> is the length of the
string but it is
<em>not
</em> packed into the data buffer. The string
is padded with null bytes if necessary to guaranteed
4 byte alignment.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4170' xml:id='l2h-
4170'
class=
"method">pack_fopaque
</tt></b>(
</nobr></td>
<td><var>n, data
</var>)
</td></tr></table></dt>
Packs a fixed length opaque data stream, similarly to
<tt class=
"method">pack_fstring()
</tt>.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4171' xml:id='l2h-
4171'
class=
"method">pack_string
</tt></b>(
</nobr></td>
<td><var>s
</var>)
</td></tr></table></dt>
Packs a variable length string,
<var>s
</var>. The length of the string is
first packed as an unsigned integer, then the string data is packed
with
<tt class=
"method">pack_fstring()
</tt>.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4172' xml:id='l2h-
4172'
class=
"method">pack_opaque
</tt></b>(
</nobr></td>
<td><var>data
</var>)
</td></tr></table></dt>
Packs a variable length opaque data string, similarly to
<tt class=
"method">pack_string()
</tt>.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4173' xml:id='l2h-
4173'
class=
"method">pack_bytes
</tt></b>(
</nobr></td>
<td><var>bytes
</var>)
</td></tr></table></dt>
Packs a variable length byte stream, similarly to
<tt class=
"method">pack_string()
</tt>.
The following methods support packing arrays and lists:
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4174' xml:id='l2h-
4174'
class=
"method">pack_list
</tt></b>(
</nobr></td>
<td><var>list, pack_item
</var>)
</td></tr></table></dt>
Packs a
<var>list
</var> of homogeneous items. This method is useful for
lists with an indeterminate size; i.e. the size is not available until
the entire list has been walked. For each item in the list, an
unsigned integer
<code>1</code> is packed first, followed by the data value
from the list.
<var>pack_item
</var> is the function that is called to pack
the individual item. At the end of the list, an unsigned integer
<code>0</code> is packed.
For example, to pack a list of integers, the code might appear like
<div class=
"verbatim"><pre>
p.pack_list([
1,
2,
3], p.pack_int)
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4175' xml:id='l2h-
4175'
class=
"method">pack_farray
</tt></b>(
</nobr></td>
<td><var>n, array, pack_item
</var>)
</td></tr></table></dt>
Packs a fixed length list (
<var>array
</var>) of homogeneous items.
<var>n
</var>
is the length of the list; it is
<em>not
</em> packed into the buffer,
but a
<tt class=
"exception">ValueError
</tt> exception is raised if
<code>len(
<var>array
</var>)
</code> is not equal to
<var>n
</var>. As above,
<var>pack_item
</var> is the function used to pack each element.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4176' xml:id='l2h-
4176'
class=
"method">pack_array
</tt></b>(
</nobr></td>
<td><var>list, pack_item
</var>)
</td></tr></table></dt>
Packs a variable length
<var>list
</var> of homogeneous items. First, the
length of the list is packed as an unsigned integer, then each element
is packed as in
<tt class=
"method">pack_farray()
</tt> above.
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<span class=
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2.4.2, documentation updated on
28 September
2005.
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