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..
.. NB:  This file is machine generated, DO NOT EDIT!
..
.. Edit vmod.vcc and run make instead
..

.. role:: ref(emphasis)

.. _vmod_blobcode(3):

=============
vmod_blobcode
=============

------------------------------------------------------------
binary-to-text encodings and decodings for the VCL blob type
------------------------------------------------------------

:Manual section: 3

SYNOPSIS
========

import blobcode [from "path"] ;


::

  sub vcl_init {
      # Create blob objects from encodings such as base64 or hex.
      new myblob   = blobcode.blob(BASE64, "Zm9vYmFy");
      new yourblob = blobcode.blob(encoded="666F6F", decoding=HEX);
  }

  sub vcl_deliver {
      # The .get() method retrieves the BLOB from an object.
      set resp.http.MyBlob-As-Hex
          = blobcode.encode(blob=myblob.get(), encoding=HEXLC);

      # The .encode() method efficiently retrieves an encoding.
      set resp.http.YourBlob-As-Base64 = yourblob.encode(BASE64);

      # decode() and encode() functions convert blobs to text and
      # vice versa at runtime.
      set resp.http.Base64-Encoded
          = blobcode.encode(BASE64,
                            blobcode.decode(HEX, req.http.Hex-Encoded));
  }

  sub vcl_recv {
      # transcode() converts from one encoding to another.
      set req.http.Hex-Encoded
          = blobcode.transcode(decoding=BASE64, encoding=HEXUC, encoded="YmF6");

      # transcode() can replace other specific encoding/deconding
      # vmods - e.g. vmod_urlcode
      set req.url = blobcode.transcode(encoded=req.url, decoding=URL);
      set req.http.url_urlcoded
          = blobcode.transcode(encoded=req.url, encoding=URLLC);
  }


DESCRIPTION
===========

This Varnish module (VMOD) supports binary-to-text encodings and
decodings for the VCL data type BLOB, which may contain arbitrary data
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of any length. Currently BLOBs may only be used as arguments of VMOD
functions; so this module is meant to facilitate the use of other
VMODs.
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ENCODING SCHEMES
================

Encoding schemes are specified by ENUMs in the VMOD's constructor,
methods and functions. Decodings convert a (possibly concatenated)
string into a blob, while encodings convert a blob into a string.

ENUM values for a decoding can be one of:

* ``IDENTITY``
* ``BASE64``
* ``BASE64URL``
* ``BASE64URLNOPAD``
* ``HEX``
* ``URL``

An encoding can be one of:

* ``IDENTITY``
* ``BASE64``
* ``BASE64URL``
* ``BASE64URLNOPAD``
* ``HEXUC``
* ``HEXLC``
* ``URLUC``
* ``URLLC``

Empty strings are decoded into a "null blob" (of length 0),
and conversely a null blob is encoded as the empty string.

IDENTITY
--------

The simplest encoding converts between the BLOB and STRING data types,
leaving the contents byte-identical.

Note that a BLOB may contain a null byte at any position before its
end; if such a BLOB is decoded with IDENTITY, the resulting STRING
will have a null byte at that position. Since VCL strings, like C
strings, are represented with a terminating null byte, the string will
be truncated, appearing to contain less data than the original
blob. For example::

  # Decode from the hex encoding for "foo\0bar".
  # The header will be seen as "foo".
  set resp.http.Trunced-Foo1
    = blobcode.encode(IDENTITY, blobcode.decode(HEX, "666f6f00626172"));

Because the IDENTITY is the default encoding and decoding, the above
can also be written as::

  # Decode from the hex encoding for "foo\0bar".
  # The header will be seen as "foo".
  set resp.http.Trunced-Foo2
    = blobcode.encode(blob=blobcode.decode(HEX, "666f6f00626172"));

BASE64*
-------

The base64 encoding schemes use 4 characters to encode 3 bytes. There
are no newlines or maximal line lengths -- whitespace is not
permitted.

The ``BASE64`` encoding uses the alphanumeric characters, ``+`` and
``/``; and encoded strings are padded with the ``=`` character so that
their length is always a multiple of four.

The ``BASE64URL`` encoding also uses the alphanumeric characters, but
``-`` and ``_`` instead of ``+`` and ``/``, so that an encoded string
can be used safely in a URL. This scheme also uses the padding
character ``=``.

The ``BASE64URLNOPAD`` encoding uses the same alphabet as
``BASE6URL``, but leaves out the padding. Thus the length of an
encoding with this scheme is not necessarily a mutltiple of four.

HEX*
----

The ``HEX`` decoding converts a hex string, which may contain upper-
or lowercase characters for hex digits ``A`` through ``f``, into a
blob. The ``HEXUC`` or ``HEXLC`` encodings convert a blob into a hex
string with upper- and lowercase digits, respectively. A prefix such
as ``0x`` is not used for any of these schemes.

If a hex string to be decoded has an odd number of digits, it is
decoded as if a ``0`` is prepended to it; that is, the first digit is
interpreted as representing the least significant nibble of the first
byte. For example::

  # The concatenated string is "abcdef0", and is decoded as "0abcdef0".
  set resp.http.First = "abc";
  set resp.http.Second = "def0";
  set resp.http.Hex-Decoded
      = blobcode.encode(HEXLC, blobcode.decode(HEX,
                        resp.http.First + resp.http.Second));

URL*
----

The ``URL`` decoding replaces any ``%<2-hex-digits>`` substrings with
the binary value of the hexadecimal number after the % sign.

The ``URLLC`` and ``URLUC`` encodings implement "percent encoding" as per
RFC3986, the hexadecimal characters A-F being output in lower- and
uppercase, respectively.

CONTENTS
========

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* BLOB decode(ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEX,URL}, STRING)
* BLOB decode_n(INT, ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEX,URL}, STRING)
* STRING encode(ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEXUC,HEXLC,URLUC,URLLC}, BLOB)
* STRING transcode(ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEX,URL}, ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEXUC,HEXLC,URLUC,URLLC}, STRING)
* STRING transcode_n(INT, ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEX,URL}, ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEXUC,HEXLC,URLUC,URLLC}, STRING)
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* STRING version()
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* blob(ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEX,URL}, STRING)
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.. _func_decode:

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decode
------
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::

	BLOB decode(ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEX,URL} decoding="IDENTITY", STRING encoded)
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Returns the BLOB derived from the string ``encoded`` according to the
scheme specified by ``decoding``.

``decoding`` defaults to IDENTITY

Example::

	blobcode.decode(BASE64, "Zm9vYmFyYmF6");

	# same with named parameters
	blobcode.decode(encoded="Zm9vYmFyYmF6", decoding=BASE64);

	# convert string to blob
	blobcode.decode(encoded="foo");

.. _func_decode_n:

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decode_n
--------
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::

	BLOB decode_n(INT n, ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEX,URL} decoding="IDENTITY", STRING encoded)
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Same as ``decode()``, but only decode the first ``n`` characters of
the decoded string. If ``n`` is greater than the length of the string,
then return the same result as ``decode()``.

.. _func_encode:

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encode
------

::
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	STRING encode(ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEXUC,HEXLC,URLUC,URLLC} encoding="IDENTITY", BLOB blob)
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Returns a string representation of the BLOB ``blob`` as specifed by
``encoding``.

``encoding`` defaults to IDENTITY

Example::

	set resp.http.encode1
	    = blobcode.encode(HEXLC, blobcode.decode(BASE64, "Zm9vYmFyYmF6"));

	# same with named parameters
	set resp.http.encode2
	    = blobcode.encode(blob=blobcode.decode(encoded="Zm9vYmFyYmF6",
						   decoding=BASE64),
			      encoding=HEXLC);

	# convert blob to string
	set resp.http.encode3
	    = blobcode.encode(blob=blobcode.decode(encoded="foo"));

.. _func_transcode:

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transcode
---------
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::

	STRING transcode(ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEX,URL} decoding="IDENTITY", ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEXUC,HEXLC,URLUC,URLLC} encoding="IDENTITY", STRING encoded)
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Translates from one encoding to another, by first decoding the string
``encoded`` according to the scheme ``decoding``, and then returning
the encoding of the resulting blob according to the scheme
``encoding``.

``decoding`` and ``encoding`` default to IDENTITY

Example::

	set resp.http.Hex2Base64-1 = blobcode.transcode(HEX, BASE64, "666f6f");

	# same with named parameters
	set resp.http.Hex2Base64-2
	    = blobcode.transcode(encoded="666f6f",
				 encoding=BASE64, decoding=HEX);

	# replacement for urlcode.decode("foo%20bar")
	set resp.http.urldecoded
	    = blobcode.transcode(encoded="foo%20bar", decoding=URLLC);

	# replacement for urlcode.encode("foo bar")
	set resp.http.urlencoded
	    = blobcode.transcode(encoded="foo bar", encoding=URL);

.. _func_transcode_n:

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transcode_n
-----------

::
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	STRING transcode_n(INT n, ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEX,URL} decoding="IDENTITY", ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEXUC,HEXLC,URLUC,URLLC} encoding="IDENTITY", STRING encoded)
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Same as ``transcode()``, but only from the first ``n`` characters of
the encoded string.

.. _func_version:

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version
-------

::
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	STRING version()

Returns the version string for this VMOD.

Example::

	std.log("Using VMOD blobcode version " + blobcode.version());

.. _obj_blob:

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blob
----
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::
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	new OBJ = blob(ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEX,URL} decoding="IDENTITY", STRING encoded)
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Creates an object that contains the BLOB derived from the string
``encoded`` according to the scheme ``decoding``.

Example::

	new theblob1 = blobcode.blob(BASE64, "YmxvYg==");

	# same with named arguments
	new theblob2 = blobcode.blob(encoded="YmxvYg==", decoding=BASE64);

	# string as a blob
	new stringblob = blobcode.blob(encoded="bazz");

.. _func_blob.get:

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blob.get
--------

::
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	BLOB blob.get()

Returns the BLOB created by the constructor.

Example::

	set resp.http.The-Blob1 =
	    blobcode.encode(blob=theblob1.get());

	set resp.http.The-Blob2 =
	    blobcode.encode(blob=theblob2.get());

	set resp.http.The-Stringblob =
	    blobcode.encode(blob=stringblob.get());

.. _func_blob.encode:

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blob.encode
-----------
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::

	STRING blob.encode(ENUM {IDENTITY,BASE64,BASE64URL,BASE64URLNOPAD,HEXUC,HEXLC,URLUC,URLLC} encoding="IDENTITY")
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Returns an encoding of BLOB created by the constructor, according to
the scheme ``encoding``.

Example::

	# blob as text
	set resp.http.The-Blob = theblob1.encode();

	# blob as base64
	set resp.http.The-Blob-b64 = theblob1.encode(BASE64);

For any ``blob`` object and encoding ``ENC``, encodings via the ``.encode()``
method and the ``encode()`` function are equal::

  # Always true:
  blobcode.encode(ENC, blob.get()) == blob.encode(ENC)

But the object method is more efficient -- the encoding is computed
once and cached (with allocation in heap memory), and the cached
encoding is retrieved on every subsequent call. The ``encode()``
function computes the encoding on every call, allocating space for the
string in Varnish workspaces.

So if the data in a BLOB are fixed at VCL initialization time, so that
its encodings will always be the same, it is better to create a
``blob`` object. The VMOD's functions should be used for data that are
not known until runtime.

ERRORS
======

The encoders and decoders may fail if there is insufficient space to
create the new blob or string. Decoders may also fail if the encoded
string is an illegal format for the decoding scheme.

If the ``blob`` object constructor fails, then the VCL program will
fail to load, and the VCC compiler will emit an error message.

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For varnish versions before 5.0, the VMOD functions -- ``encode()``,
``decode()`` and ``transcode()`` -- may not be called in
``vcl_init()`` or ``vcl_fini()`` (since a workspace must be
available). Use in ``vcl_init()`` will also cause the VCL program to
fail with a VCC compiler error.

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If any of the VMOD's methods or functions fail at runtime, then an
error message will be written to the Varnish log using the tag
``VCL_Error``. The encoders and decoders return ``NULL`` on failure;
this means that, for example, if the return value was to be assigned
to a header, then the header will not be set.

REQUIREMENTS
============

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This version of the VMOD requires Varnish version 5.0.0. (See the
project repository for versions that are compatible with other
versions of Varnish.)
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Perl 5 is required for the build.

INSTALLATION
============

The VMOD is built against a Varnish installation, and the autotools
use ``pkg-config(1)`` to locate the necessary header files and other
resources. This sequence will install the VMOD::

  > ./autogen.sh	# for builds from the git repo
  > ./configure
  > make
  > make check		# to run unit tests in src/tests/*.vtc
  > make distcheck	# run check and prepare a distribution tarball
  > sudo make install

If you have installed Varnish in a non-standard directory, call
``autogen.sh`` and ``configure`` with the ``PKG_CONFIG_PATH``
environment variable pointing to the appropriate path. For example,
when varnishd configure was called with ``--prefix=$PREFIX``, use::

  > PKG_CONFIG_PATH=${PREFIX}/lib/pkgconfig
  > export PKG_CONFIG_PATH

By default, the vmod ``configure`` script installs the vmod in
the same directory as Varnish, determined via ``pkg-config(1)``. The
vmod installation directory can be overridden by passing the
``VMOD_DIR`` variable to ``configure``.

Other files such as this man-page are installed in the locations
determined by ``configure``, which inherits its default ``--prefix``
setting from Varnish.

For developers
--------------

The build specifies C99 conformance, all compiler warnings turned on,
and all warnings considered errors (compiler options ``-std=c99
-Werror -Wall``).

By default, ``CFLAGS`` is set to ``-g -O2``, so that symbols are
included in the shared library, and optimization is at level
``O2``. To change or disable these options, set ``CFLAGS`` explicitly
before calling ``make`` (it may be set to the empty string).

For development/debugging cycles, the ``configure`` option
``--enable-debugging`` is recommended (off by default). This will turn
off optimizations and function inlining, so that a debugger will step
through the code as expected.

LIMITATIONS
===========

The VMOD allocates memory in various ways for new blobs and
strings. The ``blob`` object and its methods allocate memory from the
heap, and hence they are only limited by available virtual memory.

The ``encode()``, ``decode()`` and ``transcode()`` functions allocate
Varnish workspace.  If these functions are failing, as indicated by
"out of space" messages in the Varnish log (with the ``VCL_Error``
tag), then you will need to increase the varnishd parameters
``workspace_client`` and/or ``workspace_backend``.

The ``transcode()`` function also allocates space on the stack for a
temporary BLOB. If this function causes stack overflow, you may need
to increase the stack size for the varnishd process, for example with
``ulimit -s``. By default, the VMOD is built with the stack protector
enabled (compile option ``-fstack-protector``), but it can be disabled
with the ``configure`` option ``--disable-stack-protector``.

AUTHORS
=======

* Geoffrey Simmons <geoff@uplex.de>
* Nils Goroll <nils.goroll@uplex.de>

UPLEX Nils Goroll Systemoptimierung

This VMOD was originally adapted from, and is heavily indebted to, the
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digest VMOD by Kristian Lyngstoel.
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HISTORY
=======

* version 0.1: initial version

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* version 1.0: compatible with Varnish versions since 4.1.2

* version 2.0: compatible with Varnish versions since 5.0.0

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SEE ALSO
========

* varnishd(1)
* vcl(7)
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* project repository: https://code.uplex.de/uplex-varnish/libvmod-blobcode
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* VMOD digest: https://github.com/varnish/libvmod-digest

COPYRIGHT
=========

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::

  This document is licensed under the same conditions as the
  libvmod-blobcode project. See LICENSE for details.
 
  Authors: Nils Goroll <nils.goroll@uplex.de>
           Geoffrey Simmons <geoffrey.simmons@uplex.de>
 
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