qpdf/README

This is the QPDF package.  Information about it can be found at
http://qpdf.sourceforge.net.  The source code repository is hosted
at github: https://github.com/qpdf/qpdf.

QPDF is copyright (c) 2005-2017 Jay Berkenbilt

This software may be distributed under the terms of version 2 of the
Artistic License which may be found in the source distribution as
"Artistic-2.0".  It is provided "as is" without express or implied
warranty.


Prerequisites
=============

QPDF depends on the external libraries "zlib" and "jpeg". These are
part of every Linux distribution and are readily available. Download
information appears in the documentation. For Windows, you can
download pre-built binary versions of these libraries for some
compilers; see README-windows.txt for additional details.

QPDF requires a C++ compiler that works with STL.  Your compiler must
also support "long long".  Almost all modern compilers do.  If you are
trying to port qpdf to a compiler that doesn't support long long, you
could change all occurrences of "long long" to "long" in the source
code, noting that this would break binary compatibility with other
builds of qpdf.  Doing so would certainly prevent qpdf from working
with files larger than 2 GB, but remaining functionality would most
likely work fine.  If you built qpdf this way and it passed its test
suite with large file support disabled, you could be confident that
you had an otherwise working qpdf.


Licensing terms of embedded software
====================================

QPDF makes use of zlib and jpeg libraries for its functionality. These
packages can be downloaded separately from their own download
locations, or they can be downloaded in the external-libs area of the
qpdf download site.

The Rijndael encryption implementation used as the basis for AES
encryption and decryption support comes from Philip J. Erdelsky's
public domain implementation.  The files libqpdf/rijndael.cc and
libqpdf/qpdf/rijndael.h remain in the public domain.  They were
obtained from

  http://www.efgh.com/software/rijndael.htm
  http://www.efgh.com/software/rijndael.txt

The embedded sha2 code comes from sphlib 3.0

  http://www.saphir2.com/sphlib/

That code has the following license:

  Copyright (c) 2007-2011  Projet RNRT SAPHIR

  Permission is hereby granted, free of charge, to any person obtaining
  a copy of this software and associated documentation files (the
  "Software"), to deal in the Software without restriction, including
  without limitation the rights to use, copy, modify, merge, publish,
  distribute, sublicense, and/or sell copies of the Software, and to
  permit persons to whom the Software is furnished to do so, subject to
  the following conditions:

  The above copyright notice and this permission notice shall be included
  in all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


Building from a pristine checkout
=================================

When building qpdf from a pristine checkout from version control,
documentation and automatically generated files are not present.
Building on Windows from a pristine checkout is not guaranteed to work
because of issues running autoconf; see README-windows.txt for how to
handle this.  For UNIX and UNIX-like systems, you must have some
addditional tools installed to build from the source repository.  To
do this, you should run

./autogen.sh
./configure --enable-doc-maintenance
make
make install

If you don't have Apache fop and the docbook stylesheets installed,
you won't be able to build documentation.  You can omit
--enable-doc-maintenance and produce working qpdf software that passes
its test suite, but make install will fail because the documentation
files won't exist.  Depending on your purposes, you can either work
around this or grab the docs from a source distribution.


Building from source distribution on UNIX/Linux
===============================================

For UNIX and UNIX-like systems, you can usually get by with just

./configure
make
make install

Packagers may set DESTDIR, in which case make install will install
inside of DESTDIR, as is customary with many packages.  For more
detailed general information, see the "INSTALL" file in this
directory.  If you are already accustomed to building and installing
software that uses autoconf, there's nothing new for you in the
INSTALL file.


Building on Windows
===================

QPDF is known to build and pass its test suite with mingw (latest
version tested: gcc 4.6.2), mingw64 (latest version tested: 4.7.0) and
Microsoft Visual C++ 2010, both 32-bit and 64-bit versions.  MSYS plus
ActiveState Perl is required to build as well in order to get make
and other related tools.  See README-windows.txt for details on how to
build under Windows, see README-windows.txt.


Additional Notes on Build
=========================

QPDF's build system, inspired by abuild (http://www.abuild.org), can
optionally use its own built-in rules rather than using libtool and
obeying the compiler specified with configure.  This can be enabled by
passing --with-buildrules=buildrules where buildrules corresponds to
one of the .mk files (other than rules.mk) in the make directory.
This should never be necessary on a UNIX system, but may be necessary
on a Windows system.  See README-windows.txt for details.  There is a
gcc-linux.mk file enable "gcc-linux" build rules, but it is intended
to help test the build system; Linux users should build with the
"libtools" rules, which are enabled by default.

The QPDF package provides some executables and a software library.  A
user's manual can be found in the "doc" directory.  The docbook
sources to the user's manual can be found in the "manual" directory.

The software library is just libqpdf, and all the header files are in
the qpdf subdirectory. If you link statically with -lqpdf, then you
will also need to link with -lz and -ljpeg. The shared qpdf library is
linked with -lz and -ljpeg, none of qpdf's public header files
directly include files from libz, and only Pl_DCT.hh includes files
from libjpeg, so for most cases, qpdf's development files are self
contained. If you need to use Pl_DCT in your application code, you
will need to have the header files for some libjpeg distribution in
your include path.

To learn about using the library, please read comments in the header
files in include/qpdf, especially QPDF.hh, QPDFObjectHandle.hh, and
QPDFWriter.hh.  You can also study the code of qpdf/qpdf.cc, which
exercises most of the public interface.  There are additional example
programs in the examples directory.  Reading all the source files in
the qpdf directory (including the qpdf command-line tool and some test
drivers) along with the code in the examples directory will give you a
complete picture of every aspect of the public interface.


Additional Notes on Test Suite
==============================

By default, slow tests are disabled.  Slow tests include image
comparison tests and large file tests.  Image comparison tests can be
enabled by passing --enable-test-compare-images to ./configure.  This
was on by default in qpdf versions prior to 3.0, but is now off by
default.  Large file tests can be enabled by passing
--with-large-file-test-path=path to ./configure or by setting the
QPDF_LARGE_FILE_TEST_PATH environment variable.  Run ./configure
--help for additional options.  The test suite provides nearly full
coverage even without these tests.  Unless you are making deep changes
to the library that would impact the contents of the generated PDF
files or testing this on a new platform for the first time, there is
no real reason to run these tests.  If you're just running the test
suite to make sure that qpdf works for your build, the default tests
are adequate.  The configure rules for these tests do nothing other
than setting variables in autoconf.mk, so you can feel free to turn
these on and off directly in autoconf.mk rather than rerunning
configure.

If you are packaging qpdf for a distribution and preparing a build
that is run by an autobuilder, you may want to add the
--enable-show-failed-test-output to configure options.  This way, if
the test suite fails, test failure detail will be included in the
build output.  Otherwise, you will have to have access to the
qtest.log file from the build to view test failures.  The debian
packages for qpdf enable this option, for example.


Random Number Generation
========================

By default, when the qpdf detects either the Windows cryptography API
or the existence of /dev/urandom, /dev/arandom, or /dev/random, it
uses them to generate cryptography secure random numbers.  If none of
these conditions are true, the build will fail with an error.  This
behavior can be modified in several ways:

 * If you configure with --disable-os-secure-random or define
   SKIP_OS_SECURE_RANDOM, qpdf will not attempt to use Windows
   cryptography or the random device.  You must either supply your own
   random data provider or allow use of insecure random numbers.

 * If you configure qpdf with the --enable-insecure-random option or
   define USE_INSECURE_RANDOM, qpdf will try insecure random numbers
   if OS-provided secure random numbers are disabled.  This is not a
   fallback.  In order for insecure random numbers to be used, you
   must also disable OS secure random numbers since, otherwise,
   failure to find OS secure random numbers is a compile error.  The
   insecure random number source is stdlib's random() or rand() calls.
   These random numbers are not cryptography secure, but the qpdf
   library is fully functional using them.  Using non-secure random
   numbers means that it's easier in some cases to guess encryption
   keys.  If you're not generating encrypted files, there's no
   advantage to using secure random numbers.

 * In all cases, you may supply your own random data provider.  To do
   this, derive a class from qpdf/RandomDataProvider (since 5.1.0) and
   call QUtil::setRandomDataProvider before you create any QPDF
   objects.  If you supply your own random data provider, it will
   always be used even if support for one of the other random data
   providers is compiled in.  If you wish to avoid any possibility of
   your build of qpdf from using anything but a user-supplied random
   data provider, you can define SKIP_OS_SECURE_RANDOM and not
   USE_INSECURE_RANDOM.  In this case, qpdf will throw a runtime error
   if any attempt is made to generate random numbers and no random
   data provider has been supplied.

If you are building qpdf on a platform that qpdf doesn't know how to
generate secure random numbers on, a patch would be welcome.