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74 lines
3.6 KiB
Text
74 lines
3.6 KiB
Text
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NSBundle is a class that provides a simple front-end to the dynamic
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linking capabilities of a computer system. It allows one to more
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easily locate and load data and object files at run-time. Object files
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can include both simple functions as well as additional classes that
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the program may use.
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NSBundle locates files within bundles. A bundle is essentially a
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directory that contains text files, data files, and object files (which
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contain C functions and Objective-C classes). Usually the bundle
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directory has the extension "bundle" and the main object file that
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resides in the directory has the same name as the bundle directory,
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without any extension.
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The NSBundle class provided with GNU libobjects is meant to run on a
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variety of systems. However, some set-up is required to use it.
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Currently it has been tested on only a few systems that support
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dynamic linking -- SunOS, Solaris. It configures for HP, but I
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haven't been able to get it to work yet. There are unconfirmed reports
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it work on Linux systems.
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NSBundle set-up:
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To compile NSBundle into your programs, you need to make sure that
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libobjects was configured correctly for the dynamic linking system on
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your machine. This is done automatically in the configure script that
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comes with libobjects, but it is possible that the configuration is
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incorrect for your system (especially if it is not one of the systems
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listed above). In particular, the Makefile variable DYNAMIC_LINKER is
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set to link in the proper header file that prvides the dynamic linking
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for the system.
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You also need to configure your own program to take advantage of
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NSBundle, and also configure the compilation of any "bundles" you want
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to link into your program. Most likely you will accomplish this
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through you own customized configure script. The examples directory
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contains an example configure.example.in and Makefile.example.in which
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you can use as a template for configuring your system for compiling so
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that you can dynamically load object files into your running program.
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You will need the file aclocal.m4 that comes with the libobjects
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distribution in order to use configure.example.in in your system.
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In particular, the example configure script sets the following
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Makefile variables:
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DYNAMIC_BUNDLER_LINKER - The program that is used to link your bundle so
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it can be loaded into a running program (e.g. "gcc -Xlinker -r").
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DYNAMIC_LDFLAGS - Flags needed to link the main program so it can
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accept dynamically loaded bundles.
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DYNAMIC_CFLAGS - Flags needed to compile the sources in the bundle so
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they can be loaded into the main program (e.g. "-fPIC").
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The configure script also determines which libraries need to be linked
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in with the main program for the system to perform dynamic linking and
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adds these to the LIBS variable in Makefile.
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Also, look at the nsbundle program in the checks directory for an
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example of how to use bundles.
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NSBundle problems:
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As stated previously, NSBundle does not necessarily work on all systems.
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You cannot link in bundles on systems that do not support dynamic linking,
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although you can use the other facilities of NSBundle, such as locating
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data files within a bundle.
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If NSBundle does not work on systems that do support dynamic linking,
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it is likely that the Makefile variable DYNAMIC_BUNDLER_LINKER is not
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set-up correctly, or that libobjects did not link in the correct
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header file to use dynamic linking. Diagnosing and fixing these
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problems is not trivial and requires some knowledge of dynamic
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linking, object file formats and the Objective-C runtime. Contact Adam
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Fedor <fedor@boulder.colorado.edu> for help.
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