Difference between revisions of "Creating bindings for C libraries"
| Line 69: | Line 69: | ||
*The -l library path is "mpich". | *The -l library path is "mpich". | ||
*Output extension is ".pas" | *Output extension is ".pas" | ||
| − | *Output directory is h2pas/ | + | *Output directory is h2pas/, so leave it empty |
=Run the wizard= | =Run the wizard= | ||
Revision as of 00:33, 21 September 2006
Overview
This page describes how to create pascal bindings for C libraries. Normally Pascal can not use C libraries directly. You have to create for every C function, type, variable a pascal translation. There is the h2pas tool, which can automatically translate many common C things. And there is a GUI for Lazarus using h2pas and other tools to automate the creation, so that if the bindings needs to be updated you don't have to restart all over.
Work flow
- Fetch the C header files you want to translate.
- Create a working directory and give your bindings a name
- Create a new h2pas project with the h2pas wizard.
- add the .h files to the project
- setup the h2pas options
- run the wizard
- fix errors by adding text tools and run the wizard again
- when h2pas runs without errors, test compilation and add optional tools to beautify the output
- write some test programs to test your bindings
- publish your bindings on lazarus-ccr or Free Pascal
Install tools
The h2pas tool comes with every normal fpc installation.
Install the h2paswizard package in the Lazarus IDE. Go to "Components -> Configure installed packages ...", select from the right list the H2PasWizard package and click 'Install selection', then 'Save and rebuild IDE'. Restart the IDE and you get a new menu entry: Tools -> h2pas
Fetch C header files
The C header files .h describes the interface of a C library. They are normally not provided with the library. You have to get the sources or the development package of the library. For example the C header files of the gtk libraries are in the package gtk+-devel.
Example: MPICH2
Download the mpich2-1.0.3.tar.gz from http://www-unix.mcs.anl.gov/mpi/mpich2/ and unpack them. The .h files are under mpich2-1.0.3/src/include.
Create a working directory and name your bindings
Create a directory with a useful name. A name should not contain special characters, like spaces, umlaute, points or commas. Copy the .h files.
Example: MPICH2
The h2p directory will be used for the pascal files. The h2p/c_sources directory will be used for the .h files.
mkdir -p h2p/c_sources cp mpich2-1.0.3/src/include/*.h h2p/c_sources
Create a new h2pas project with the h2pas wizard
Open the h2pas wizard: "Tools -> h2pas". This will open a window. You can switch between this window and the other IDE windows. Your last h2pas project will be loaded automatically. To create a new project click on "Settings -> New/Clear settings". Then click on the bottom button "Save settings" and choose a filename.
Example: MPICH2
Click on "Settings -> New/Clear settings". Then click on the bottom button "Save settings" and save it as h2p/mpi2.h2p.
Add the .h files to the project
In the "C header files" page you can add/delete the .h files. You can enable/disable .h files to convert only part of the files.
Example: MPICH2
Click on "C header files -> Add .h files ..." and select "mpi.h". It will be enabled automatically.
Setup the h2pas options
Under "h2pas Options" you can set the parameters for the h2pas program.
Example: MPICH2
- Enable -e, -i, -D, -p, -w and disable all others.
- The -l library path is "mpich".
- Output extension is ".pas"
- Output directory is h2pas/, so leave it empty
Run the wizard
Click on the bottom button "Run"
