Added imghdr,xdrlib; reformatted Makefile somewhat

7 files changed, 614 insertions, 31 deletions

diff --git a/Doc/Makefile b/Doc/Makefile
index ce469ca..81d8e72 100644
--- a/Doc/Makefile
+++ b/Doc/Makefile
@@ -108,37 +108,26 @@ ref.ps:	ref.dvi
 
 # LaTeX source files for the Python Library Reference
 LIBFILES = lib.tex \
-libal.tex libaifc.tex liballos.tex \
-	libamoeba.tex libarray.tex libaudio.tex libaudioop.tex \
-libbltin.tex libbinascii.tex \
-libcd.tex \
-libcgi.tex libcopy.tex libctb.tex libcrypto.tex \
-libdbm.tex \
-libexcs.tex \
-libfcntl.tex libfl.tex libfm.tex libftplib.tex libfuncs.tex \
-libgdbm.tex libgetopt.tex libgl.tex libgopherlib.tex libgrp.tex \
-libhtmllib.tex libhttplib.tex \
-libimageop.tex libimgfile.tex libintro.tex \
-libjpeg.tex \
-libmac.tex libmacconsole.tex libmacdnr.tex \
-	libmacfs.tex libmacos.tex libmacostools.tex libmactcp.tex \
-	libmacspeech.tex libmacui.tex \
-	libmain.tex libmarshal.tex libmath.tex \
-	libmd5.tex libmimetools.tex libmisc.tex \
-	libmm.tex libmpz.tex \
-libnntplib.tex \
-libobjs.tex libos.tex \
-libpanel.tex libparser.tex libpickle.tex libposix.tex libposixfile.tex \
-	libppath.tex libprofile.tex libpwd.tex libpython.tex \
-librand.tex libregex.tex libregsub.tex \
-	librfc822.tex librgbimg.tex librotor.tex \
-libselect.tex libsgi.tex libsgmllib.tex \
-	libshelve.tex libsocket.tex libsomeos.tex libstdwin.tex \
-	libstring.tex libstrings.tex libstruct.tex libsun.tex libsys.tex \
-libtempfile.tex libtermios.tex libthread.tex libtime.tex \
-	libtraceback.tex libtypes.tex libtypes2.tex \
-libunix.tex liburllib.tex liburlparse.tex \
-libwhrandom.tex libwww.tex
+    libintro.tex libobjs.tex libtypes.tex libexcs.tex libfuncs.tex \
+    libpython.tex libsys.tex libtypes2.tex libtraceback.tex libpickle.tex \
+    libshelve.tex libcopy.tex libmarshal.tex libimp.tex libparser.tex \
+    libbltin.tex libmain.tex libstrings.tex libstring.tex libregex.tex \
+    libregsub.tex libstruct.tex libmisc.tex libmath.tex librand.tex \
+    libwhrandom.tex libarray.tex liballos.tex libos.tex libtime.tex \
+    libgetopt.tex libtempfile.tex liberrno.tex libsomeos.tex libsignal.tex \
+    libsocket.tex libselect.tex libthread.tex libunix.tex libposix.tex \
+    libppath.tex libpwd.tex libgrp.tex libcrypt.tex libdbm.tex libgdbm.tex \
+    libtermios.tex libfcntl.tex libposixfile.tex libsyslog.tex libpdb.tex \
+    libprofile.tex libwww.tex libcgi.tex liburllib.tex libhttplib.tex \
+    libftplib.tex libgopherlib.tex libnntplib.tex liburlparse.tex \
+    libhtmllib.tex libsgmllib.tex librfc822.tex libmimetools.tex \
+    libbinascii.tex libmm.tex libaudioop.tex libimageop.tex libaifc.tex \
+    libjpeg.tex librgbimg.tex libcrypto.tex libmd5.tex libmpz.tex \
+    librotor.tex libmac.tex libctb.tex libmacconsole.tex libmacdnr.tex \
+    libmacfs.tex libmacos.tex libmacostools.tex libmactcp.tex \
+    libmacspeech.tex libmacui.tex libstdwin.tex libsgi.tex libal.tex \
+    libcd.tex libfl.tex libfm.tex libgl.tex libimgfile.tex libsun.tex \
+    libxdrlib.tex libimghdr.tex
 
 # Library document
 lib.dvi: $(LIBFILES)
diff --git a/Doc/lib.tex b/Doc/lib.tex
index 4239c4a..2c99cbe 100644
--- a/Doc/lib.tex
+++ b/Doc/lib.tex
@@ -142,6 +142,7 @@ to Python and how to embed it in other applications.
 \input{librfc822}
 \input{libmimetools}
 \input{libbinascii}
+\input{libxdrlib}
 
 \input{libmm}			% Multimedia Services
 \input{libaudioop}
@@ -149,6 +150,7 @@ to Python and how to embed it in other applications.
 \input{libaifc}
 \input{libjpeg}
 \input{librgbimg}
+\input{libimghdr}
 
 \input{libcrypto}		% Cryptographic Services
 \input{libmd5}
diff --git a/Doc/lib/lib.tex b/Doc/lib/lib.tex
index 4239c4a..2c99cbe 100644
--- a/Doc/lib/lib.tex
+++ b/Doc/lib/lib.tex
@@ -142,6 +142,7 @@ to Python and how to embed it in other applications.
 \input{librfc822}
 \input{libmimetools}
 \input{libbinascii}
+\input{libxdrlib}
 
 \input{libmm}			% Multimedia Services
 \input{libaudioop}
@@ -149,6 +150,7 @@ to Python and how to embed it in other applications.
 \input{libaifc}
 \input{libjpeg}
 \input{librgbimg}
+\input{libimghdr}
 
 \input{libcrypto}		% Cryptographic Services
 \input{libmd5}
diff --git a/Doc/lib/libimghdr.tex b/Doc/lib/libimghdr.tex
new file mode 100644
index 0000000..22d4d0d
--- /dev/null
+++ b/Doc/lib/libimghdr.tex
@@ -0,0 +1,60 @@
+\section{Standard module \sectcode{imghdr}}
+\stmodindex{imghdr}
+
+The \code{imghdr} module determines the type of image contained in a
+file or byte stream.
+
+The \code{imghdr} module defines the following function:
+
+\renewcommand{\indexsubitem}{(in module imghdr)}
+
+\begin{funcdesc}{what}{filename\optional{\, h}}
+Tests the image data contained in the file named by \var{filename},
+and returns a string describing the image type.  If optional \var{h}
+is provided, the \var{filename} is ignored and \var{h} is assumed to
+contain the byte stream to test.
+\end{funcdesc}
+
+The following image types are recognized, as listed below with the
+return value from \code{what}:
+
+\begin{enumerate}
+\item[``rgb''] SGI ImgLib Files
+
+\item[``gif''] GIF 87a and 89a Files
+
+\item[``pbm''] Portable Bitmap Files
+
+\item[``pgm''] Portable Graymap Files
+
+\item[``ppm''] Portable Pixmap Files
+
+\item[``tiff''] TIFF Files
+
+\item[``rast''] Sun Raster Files
+
+\item[``xbm''] X Bitmap Files
+
+\item[``jpeg''] JPEG data in JIFF format
+\end{enumerate}
+
+You can extend the list of file types \code{imghdr} can recognize by
+appending to this variable:
+
+\begin{datadesc}{tests}
+A list of functions performing the individual tests.  Each function
+takes two arguments: the byte-stream and an open file-like object.
+When \code{what()} is called with a byte-stream, the file-like
+object will be \code{None}.
+
+The test function should return a string describing the image type if
+the test succeeded, or \code{None} if it failed.
+\end{datadesc}
+
+Example:
+
+\begin{verbatim}
+>>> import imghdr
+>>> imghdr.what('/tmp/bass.gif')
+'gif'
+\end{verbatim}
diff --git a/Doc/lib/libxdrlib.tex b/Doc/lib/libxdrlib.tex
new file mode 100644
index 0000000..705dd0f
--- /dev/null
+++ b/Doc/lib/libxdrlib.tex
@@ -0,0 +1,235 @@
+\section{Standard module \sectcode{xdrlib}}
+\stmodindex{xdrlib}
+\index{XDR}
+
+\renewcommand{\indexsubitem}{(in module xdrlib)}
+
+
+The \code{xdrlib} module supports the External Data Representation
+Standard as described in RFC 1014, written by Sun Microsystems,
+Inc. June 1987.  It supports most of the data types described in the
+RFC, although some, most notably \code{float} and \code{double} are
+only supported on those operating systems that provide an XDR
+library.
+
+The \code{xdrlib} module defines two classes, one for packing
+variables into XDR representation, and another for unpacking from XDR
+representation.  There are also two exception classes.
+
+
+\subsection{Packer Objects}
+
+\code{Packer} is the class for packing data into XDR representation.
+The \code{Packer} class is instantiated with no arguments.
+
+\begin{funcdesc}{get_buffer}{}
+Returns the current pack buffer as a string.
+\end{funcdesc}
+
+\begin{funcdesc}{reset}{}
+Resets the pack buffer to the empty string.
+\end{funcdesc}
+
+In general, you can pack any of the most common XDR data types by
+calling the appropriate \code{pack_\var{type}} method.  Each method
+takes a single argument, the value to pack.  The following simple data
+type packing methods are supported: \code{pack_uint}, \code{pack_int},
+\code{pack_enum}, \code{pack_bool}, \code{pack_uhyper},
+and \code{pack_hyper}.
+
+The following methods pack floating point numbers, however they
+require C library support.  Without the optional C built-in module,
+both of these methods will raise an \code{xdrlib.ConversionError}
+exception.  See the note at the end of this chapter for details.
+
+\begin{funcdesc}{pack_float}{value}
+Packs the single-precision floating point number \var{value}.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_double}{value}
+Packs the double-precision floating point number \var{value}.
+\end{funcdesc}
+
+The following methods support packing strings, bytes, and opaque data:
+
+\begin{funcdesc}{pack_fstring}{n\, s}
+Packs a fixed length string, \var{s}.  \var{n} is the length of the
+string but it is \emph{not} packed into the data buffer.  The string
+is padded with null bytes if necessary to guaranteed 4 byte alignment.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_fopaque}{n\, data}
+Packs a fixed length opaque data stream, similarly to
+\code{pack_fstring}.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_string}{s}
+Packs a variable length string, \var{s}.  The length of the string is
+first packed as an unsigned integer, then the string data is packed
+with \code{pack_fstring}.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_opaque}{data}
+Packs a variable length opaque data string, similarly to
+\code{pack_string}.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_bytes}{bytes}
+Packs a variable length byte stream, similarly to \code{pack_string}.
+\end{funcdesc}
+
+The following methods support packing arrays and lists:
+
+\begin{funcdesc}{pack_list}{list\, pack_item}
+Packs a \var{list} 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} is packed first, followed by the data value
+from the list.  \var{pack_item} is the function that is called to pack
+the individual item.  At the end of the list, an unsigned integer
+\code{0} is packed.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_farray}{n\, array\, pack_item}
+Packs a fixed length list (\var{array}) of homogeneous items.  \var{n}
+is the length of the list; it is \emph{not} packed into the buffer,
+but a \code{ValueError} exception is raised if \code{len(array)} is not
+equal to \var{n}.  As above, \var{pack_item} is the function used to
+pack each element.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_array}{list\, pack_item}
+Packs a variable length \var{list} of homogeneous items.  First, the
+length of the list is packed as an unsigned integer, then each element
+is packed as in \code{pack_farray} above.
+\end{funcdesc}
+
+\subsection{Unpacker Objects}
+
+\code{Unpacker} is the complementary class which unpacks XDR data
+values from a string buffer, and has the following methods:
+
+\begin{funcdesc}{__init__}{data}
+Instantiates an \code{Unpacker} object with the string buffer
+\var{data}.
+\end{funcdesc}
+
+\begin{funcdesc}{reset}{data}
+Resets the string buffer with the given \var{data}.
+\end{funcdesc}
+
+\begin{funcdesc}{get_position}{}
+Returns the current unpack position in the data buffer.
+\end{funcdesc}
+
+\begin{funcdesc}{set_position}{position}
+Sets the data buffer unpack position to \var{position}.  You should be
+careful about using \code{get_position()} and \code{set_position()}.
+\end{funcdesc}
+
+\begin{funcdesc}{done}{}
+Indicates unpack completion.  Raises an \code{xdrlib.Error} exception
+if all of the data has not been unpacked.
+\end{funcdesc}
+
+In addition, every data type that can be packed with a \code{Packer},
+can be unpacked with an \code{Unpacker}.  Unpacking methods are of the
+form \code{unpack_\var{type}}, and take no arguments.  They return the
+unpacked object.  The same caveats apply for \code{unpack_float} and
+\code{unpack_double} as above.
+
+In addition, the following methods unpack strings, bytes, and opaque
+data:
+
+\begin{funcdesc}{unpack_fstring}{n}
+Unpacks and returns a fixed length string.  \var{n} is the number of
+characters expected.  Padding with null bytes to guaranteed 4 byte
+alignment is assumed.
+\end{funcdesc}
+
+\begin{funcdesc}{unpack_fopaque}{n}
+Unpacks and returns a fixed length opaque data stream, similarly to
+\code{unpack_fstring}.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_string}{}
+Unpacks and returns a variable length string.  The length of the
+string is first unpacked as an unsigned integer, then the string data
+is unpacked with \code{unpack_fstring}.
+\end{funcdesc}
+
+\begin{funcdesc}{unpack_opaque}{}
+Unpacks and returns a variable length opaque data string, similarly to
+\code{pack_string}.
+\end{funcdesc}
+
+\begin{funcdesc}{unpack_bytes}{}
+Unpacks and returns a variable length byte stream, similarly to
+\code{pack_string}.
+\end{funcdesc}
+
+The following methods support unpacking arrays and lists:
+
+\begin{funcdesc}{unpack_list}{unpack_item}
+Unpacks and returns a list of homogeneous items.  The list is unpacked
+one element at a time
+by first unpacking an unsigned integer flag.  If the flag is \code{1},
+then the item is unpacked and appended to the list.  A flag of
+\code{0} indicates the end of the list.  \var{unpack_item} is the
+function that is called to unpack the items.
+\end{funcdesc}
+
+\begin{funcdesc}{unpack_farray}{n\, unpack_item}
+Unpacks and returns (as a list) a fixed length array of homogeneous
+items.  \var{n} is number of list elements to expect in the buffer.
+As above, \var{unpack_item} is the function used to unpack each element.
+\end{funcdesc}
+
+\begin{funcdesc}{unpack_array}{unpack_item}
+Unpacks and returns a variable length \var{list} of homogeneous items.
+First, the length of the list is unpacked as an unsigned integer, then
+each element is unpacked as in \code{unpack_farray} above.
+\end{funcdesc}
+
+\subsection{Exceptions}
+
+Exceptions in this module are coded as class instances:
+
+\begin{excdesc}{Error}
+The base exception class.  \code{Error} has a single public data
+member \code{msg} containing the description of the error.
+\end{excdesc}
+
+\begin{excdesc}{ConversionError}
+Class derived from \code{Error}.  Contains no additional instance
+variables.
+\end{excdesc}
+
+Here is an example of how you would catch one of these exceptions:
+
+\begin{verbatim}
+import xdrlib
+p = xdrlib.Packer()
+try:
+    p.pack_double(8.01)
+except xdrlib.ConversionError, instance:
+    print 'packing the double failed:', instance.msg
+\end{verbatim}
+
+\subsection{Supporting Floating Point Data}
+
+Packing and unpacking floating point data,
+i.e. \code{Packer.pack_float}, \code{Packer.pack_double},
+\code{Unpacker.unpack_float}, and \code{Unpacker.unpack_double}, are
+only supported with the helper built-in \code{_xdr} module, which
+relies on your operating system having the appropriate XDR library
+routines.
+
+If you have built the Python interpeter with the \code{_xdr} module,
+or have built the \code{_xdr} module as a shared library,
+\code{xdrlib} will use these to pack and unpack floating point
+numbers.  Otherwise, using these routines will raise a
+\code{ConversionError} exception.
+
+See the Python installation instructions for details on building the
+\code{_xdr} module.
diff --git a/Doc/libimghdr.tex b/Doc/libimghdr.tex
new file mode 100644
index 0000000..22d4d0d
--- /dev/null
+++ b/Doc/libimghdr.tex
@@ -0,0 +1,60 @@
+\section{Standard module \sectcode{imghdr}}
+\stmodindex{imghdr}
+
+The \code{imghdr} module determines the type of image contained in a
+file or byte stream.
+
+The \code{imghdr} module defines the following function:
+
+\renewcommand{\indexsubitem}{(in module imghdr)}
+
+\begin{funcdesc}{what}{filename\optional{\, h}}
+Tests the image data contained in the file named by \var{filename},
+and returns a string describing the image type.  If optional \var{h}
+is provided, the \var{filename} is ignored and \var{h} is assumed to
+contain the byte stream to test.
+\end{funcdesc}
+
+The following image types are recognized, as listed below with the
+return value from \code{what}:
+
+\begin{enumerate}
+\item[``rgb''] SGI ImgLib Files
+
+\item[``gif''] GIF 87a and 89a Files
+
+\item[``pbm''] Portable Bitmap Files
+
+\item[``pgm''] Portable Graymap Files
+
+\item[``ppm''] Portable Pixmap Files
+
+\item[``tiff''] TIFF Files
+
+\item[``rast''] Sun Raster Files
+
+\item[``xbm''] X Bitmap Files
+
+\item[``jpeg''] JPEG data in JIFF format
+\end{enumerate}
+
+You can extend the list of file types \code{imghdr} can recognize by
+appending to this variable:
+
+\begin{datadesc}{tests}
+A list of functions performing the individual tests.  Each function
+takes two arguments: the byte-stream and an open file-like object.
+When \code{what()} is called with a byte-stream, the file-like
+object will be \code{None}.
+
+The test function should return a string describing the image type if
+the test succeeded, or \code{None} if it failed.
+\end{datadesc}
+
+Example:
+
+\begin{verbatim}
+>>> import imghdr
+>>> imghdr.what('/tmp/bass.gif')
+'gif'
+\end{verbatim}
diff --git a/Doc/libxdrlib.tex b/Doc/libxdrlib.tex
new file mode 100644
index 0000000..705dd0f
--- /dev/null
+++ b/Doc/libxdrlib.tex
@@ -0,0 +1,235 @@
+\section{Standard module \sectcode{xdrlib}}
+\stmodindex{xdrlib}
+\index{XDR}
+
+\renewcommand{\indexsubitem}{(in module xdrlib)}
+
+
+The \code{xdrlib} module supports the External Data Representation
+Standard as described in RFC 1014, written by Sun Microsystems,
+Inc. June 1987.  It supports most of the data types described in the
+RFC, although some, most notably \code{float} and \code{double} are
+only supported on those operating systems that provide an XDR
+library.
+
+The \code{xdrlib} module defines two classes, one for packing
+variables into XDR representation, and another for unpacking from XDR
+representation.  There are also two exception classes.
+
+
+\subsection{Packer Objects}
+
+\code{Packer} is the class for packing data into XDR representation.
+The \code{Packer} class is instantiated with no arguments.
+
+\begin{funcdesc}{get_buffer}{}
+Returns the current pack buffer as a string.
+\end{funcdesc}
+
+\begin{funcdesc}{reset}{}
+Resets the pack buffer to the empty string.
+\end{funcdesc}
+
+In general, you can pack any of the most common XDR data types by
+calling the appropriate \code{pack_\var{type}} method.  Each method
+takes a single argument, the value to pack.  The following simple data
+type packing methods are supported: \code{pack_uint}, \code{pack_int},
+\code{pack_enum}, \code{pack_bool}, \code{pack_uhyper},
+and \code{pack_hyper}.
+
+The following methods pack floating point numbers, however they
+require C library support.  Without the optional C built-in module,
+both of these methods will raise an \code{xdrlib.ConversionError}
+exception.  See the note at the end of this chapter for details.
+
+\begin{funcdesc}{pack_float}{value}
+Packs the single-precision floating point number \var{value}.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_double}{value}
+Packs the double-precision floating point number \var{value}.
+\end{funcdesc}
+
+The following methods support packing strings, bytes, and opaque data:
+
+\begin{funcdesc}{pack_fstring}{n\, s}
+Packs a fixed length string, \var{s}.  \var{n} is the length of the
+string but it is \emph{not} packed into the data buffer.  The string
+is padded with null bytes if necessary to guaranteed 4 byte alignment.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_fopaque}{n\, data}
+Packs a fixed length opaque data stream, similarly to
+\code{pack_fstring}.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_string}{s}
+Packs a variable length string, \var{s}.  The length of the string is
+first packed as an unsigned integer, then the string data is packed
+with \code{pack_fstring}.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_opaque}{data}
+Packs a variable length opaque data string, similarly to
+\code{pack_string}.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_bytes}{bytes}
+Packs a variable length byte stream, similarly to \code{pack_string}.
+\end{funcdesc}
+
+The following methods support packing arrays and lists:
+
+\begin{funcdesc}{pack_list}{list\, pack_item}
+Packs a \var{list} 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} is packed first, followed by the data value
+from the list.  \var{pack_item} is the function that is called to pack
+the individual item.  At the end of the list, an unsigned integer
+\code{0} is packed.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_farray}{n\, array\, pack_item}
+Packs a fixed length list (\var{array}) of homogeneous items.  \var{n}
+is the length of the list; it is \emph{not} packed into the buffer,
+but a \code{ValueError} exception is raised if \code{len(array)} is not
+equal to \var{n}.  As above, \var{pack_item} is the function used to
+pack each element.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_array}{list\, pack_item}
+Packs a variable length \var{list} of homogeneous items.  First, the
+length of the list is packed as an unsigned integer, then each element
+is packed as in \code{pack_farray} above.
+\end{funcdesc}
+
+\subsection{Unpacker Objects}
+
+\code{Unpacker} is the complementary class which unpacks XDR data
+values from a string buffer, and has the following methods:
+
+\begin{funcdesc}{__init__}{data}
+Instantiates an \code{Unpacker} object with the string buffer
+\var{data}.
+\end{funcdesc}
+
+\begin{funcdesc}{reset}{data}
+Resets the string buffer with the given \var{data}.
+\end{funcdesc}
+
+\begin{funcdesc}{get_position}{}
+Returns the current unpack position in the data buffer.
+\end{funcdesc}
+
+\begin{funcdesc}{set_position}{position}
+Sets the data buffer unpack position to \var{position}.  You should be
+careful about using \code{get_position()} and \code{set_position()}.
+\end{funcdesc}
+
+\begin{funcdesc}{done}{}
+Indicates unpack completion.  Raises an \code{xdrlib.Error} exception
+if all of the data has not been unpacked.
+\end{funcdesc}
+
+In addition, every data type that can be packed with a \code{Packer},
+can be unpacked with an \code{Unpacker}.  Unpacking methods are of the
+form \code{unpack_\var{type}}, and take no arguments.  They return the
+unpacked object.  The same caveats apply for \code{unpack_float} and
+\code{unpack_double} as above.
+
+In addition, the following methods unpack strings, bytes, and opaque
+data:
+
+\begin{funcdesc}{unpack_fstring}{n}
+Unpacks and returns a fixed length string.  \var{n} is the number of
+characters expected.  Padding with null bytes to guaranteed 4 byte
+alignment is assumed.
+\end{funcdesc}
+
+\begin{funcdesc}{unpack_fopaque}{n}
+Unpacks and returns a fixed length opaque data stream, similarly to
+\code{unpack_fstring}.
+\end{funcdesc}
+
+\begin{funcdesc}{pack_string}{}
+Unpacks and returns a variable length string.  The length of the
+string is first unpacked as an unsigned integer, then the string data
+is unpacked with \code{unpack_fstring}.
+\end{funcdesc}
+
+\begin{funcdesc}{unpack_opaque}{}
+Unpacks and returns a variable length opaque data string, similarly to
+\code{pack_string}.
+\end{funcdesc}
+
+\begin{funcdesc}{unpack_bytes}{}
+Unpacks and returns a variable length byte stream, similarly to
+\code{pack_string}.
+\end{funcdesc}
+
+The following methods support unpacking arrays and lists:
+
+\begin{funcdesc}{unpack_list}{unpack_item}
+Unpacks and returns a list of homogeneous items.  The list is unpacked
+one element at a time
+by first unpacking an unsigned integer flag.  If the flag is \code{1},
+then the item is unpacked and appended to the list.  A flag of
+\code{0} indicates the end of the list.  \var{unpack_item} is the
+function that is called to unpack the items.
+\end{funcdesc}
+
+\begin{funcdesc}{unpack_farray}{n\, unpack_item}
+Unpacks and returns (as a list) a fixed length array of homogeneous
+items.  \var{n} is number of list elements to expect in the buffer.
+As above, \var{unpack_item} is the function used to unpack each element.
+\end{funcdesc}
+
+\begin{funcdesc}{unpack_array}{unpack_item}
+Unpacks and returns a variable length \var{list} of homogeneous items.
+First, the length of the list is unpacked as an unsigned integer, then
+each element is unpacked as in \code{unpack_farray} above.
+\end{funcdesc}
+
+\subsection{Exceptions}
+
+Exceptions in this module are coded as class instances:
+
+\begin{excdesc}{Error}
+The base exception class.  \code{Error} has a single public data
+member \code{msg} containing the description of the error.
+\end{excdesc}
+
+\begin{excdesc}{ConversionError}
+Class derived from \code{Error}.  Contains no additional instance
+variables.
+\end{excdesc}
+
+Here is an example of how you would catch one of these exceptions:
+
+\begin{verbatim}
+import xdrlib
+p = xdrlib.Packer()
+try:
+    p.pack_double(8.01)
+except xdrlib.ConversionError, instance:
+    print 'packing the double failed:', instance.msg
+\end{verbatim}
+
+\subsection{Supporting Floating Point Data}
+
+Packing and unpacking floating point data,
+i.e. \code{Packer.pack_float}, \code{Packer.pack_double},
+\code{Unpacker.unpack_float}, and \code{Unpacker.unpack_double}, are
+only supported with the helper built-in \code{_xdr} module, which
+relies on your operating system having the appropriate XDR library
+routines.
+
+If you have built the Python interpeter with the \code{_xdr} module,
+or have built the \code{_xdr} module as a shared library,
+\code{xdrlib} will use these to pack and unpack floating point
+numbers.  Otherwise, using these routines will raise a
+\code{ConversionError} exception.
+
+See the Python installation instructions for details on building the
+\code{_xdr} module.