Prefix Group

These functions provide the ability to determine the runtime location of a software package. More...

Typedefs

typedef struct _Eina_Prefix Eina_Prefix
 This is a prefix object that is returned by eina_prefix_new() when trying to determine the runtime location of the software in question so other data files such as images, sound files, other executable utilities, libraries, modules and locale files can be found. More...
 

Functions

Eina_Prefixeina_prefix_new (const char *argv0, void *symbol, const char *envprefix, const char *sharedir, const char *magicsharefile, const char *pkg_bin, const char *pkg_lib, const char *pkg_data, const char *pkg_locale)
 Create a new prefix handle given some input information. More...
 
void eina_prefix_free (Eina_Prefix *pfx)
 Free the prefix object and all its contents. More...
 
const char * eina_prefix_get (Eina_Prefix *pfx)
 Get the prefix base directory. More...
 
const char * eina_prefix_bin_get (Eina_Prefix *pfx)
 Get the binary installation directory. More...
 
const char * eina_prefix_lib_get (Eina_Prefix *pfx)
 Get the library installation directory. More...
 
const char * eina_prefix_data_get (Eina_Prefix *pfx)
 Get the data installation directory. More...
 
const char * eina_prefix_locale_get (Eina_Prefix *pfx)
 Get the locale installation directory. More...
 

Detailed Description

These functions provide the ability to determine the runtime location of a software package.

Since
1.1.0

Typedef Documentation

This is a prefix object that is returned by eina_prefix_new() when trying to determine the runtime location of the software in question so other data files such as images, sound files, other executable utilities, libraries, modules and locale files can be found.

Since
1.1.0

Function Documentation

Eina_Prefix* eina_prefix_new ( const char *  argv0,
void *  symbol,
const char *  envprefix,
const char *  sharedir,
const char *  magicsharefile,
const char *  pkg_bin,
const char *  pkg_lib,
const char *  pkg_data,
const char *  pkg_locale 
)

Create a new prefix handle given some input information.

Parameters
argv0If this is an executable this is argv[0] of the binary, or NULL if it is used from a shared library
symbolThis is a symbol (function for example) inside the binary or library to find the source location of. Provide NULL if not used
envprefixThis is the prefix to any environment variables that may override prefix detection and give the exact location of the software
sharedirThis is the directory inside the standard share or data dir where the software will store data files
magicsharefileThis is a magic file to check existence of to determine the prefix find was correct, and it must be located in the data dir under the share dir provided above, or NULL if the check is not to be done.
pkg_binThis is the compile-time binary install dir
pkg_libThis is the compile-time library install dir
pkg_dataThis is the compile-time share/data install dir
pkg_localeThis is the compile-time locale install dir
Returns
The prefix handle, or NULL on failure.

Applications and libraries are most often not just single executables nor single shared library binaries, but also come with extra modules they have to load, extra binary utilities they need to run, or have data files they need to load. A very primitive application ASSUMES a fixed install location at compile-time, but this disallows the ability to re-locate the application (or library) somewhere else after compilation (if you run out of space on a given disk, partition etc. for example), or necessitate the need for having to maintain environment variables for every piece of software to let it know its location, or have to use large sets of symlinks pointing from the compiled location to the new one.

Being re-locatable at runtime allows much easier distribution and installation into places like the users own home directory, instead of on a system partition, if the developer wishes for easier distribution of pre-compiled binaries.

The prefix system is designed to locate where the given software is installed (under a common prefix) at runtime and then report specific locations of this prefix and common directories inside this prefix like the binary, library, data and locale directories.

To do this some information needs to be provided to eina_prefix_new(). If you have developed a binary executable, then provide argv[0] as the argv0 argument. This plus the PATH environment variable help the prefix system to determine its location. Call eina_prefix_new() early on before you change working directory or anything about argv[0] so it gets accurate information. It will use the first argument, being the executable itself, to look in absolute directories, relative paths and PATH to see if it finds the right executable to determine just where the actual binary is installed and being run from. If you develop a share library, just pass NULL as argv0

It would prefer to use the symbol function to determine location as that function will be unique inside the application and try and trace back which file this function comes from (be it a binary or shared library) as this avoids more expensive searches via argv0. It will use this symbol if given in preference to argv0.

The envprefix parameter, provides a string prefix to prepend before environment variables to allow a fallback to specific environment variables to locate the software. For example if "MYAPP" is provided a the prefix, then it uses "MYAPP_PREFIX" as a master environment variable to specify the exact install prefix for the software, or more specific environment variables like "MYAPP_BIN_DIR", "MYAPP_LIB_DIR", "MYAPP_DATA_DIR" and "MYAPP_LOCALE_DIR" which can be set by the user or scripts before launching. If not provided (NULL) environment variables will not be used to override compiled-in defaults or auto detections.

The sharedir string provides a subdirectory inside the system shared data dir for data files. For example, if the system dir is /usr/local/share then this dir name is appended, creating /usr/local/share/appname if this dir was the "appname" string. It is expected the application or library installs data files in this directory.

The magicsharefile is a filename or path of something inside the share or data dir to be used to test that the prefix detection worked. For example, your app will install a wallpaper image as /usr/local/share/appname/images/wallpaper.jpg and so to check that this worked, provide "images/wallpaper.jpg" as the magicsharefile string so detection can know if it worked or not.

The pkg_bin, pkg_lib, pkg_data and pkg_locale are compile-time strings (the kind standard autoconf/automake define) to be passed in so there can be a fallback to compiled-in defaults as well as use them to determine actual names of directories like libdirs maybe changing to be lib32 or lib64 instead of lib etc.

Compile the following defining at compile time your prefixes like (example):

gcc appname.c -o appname -DPACKAGE_BIN_DIR=\"/usr/local/bin\" -DPACKAGE_LIB_DIR=\"/usr/local/lib\" -DPACKAGE_DATA_DIR=\"/usr/local/share/appname\" -DLOCALE_DIR=\"/usr/local/share/locale\" pkg-config --cflags --libs eina

(of course add appropriate compile flags to linking etc. etc. and note that locale dir is optional. if you don't need it provide data dir as the locale dir. also note that the magicsharefile is optional for testing and ensuring that the prefix check is correct. this file must be installed in the application data dir (eg /usr/local/share/appname) and be referred to using a unix-style relative path from that dir, eg directory/filename.png)

* #include <Eina.h>
*
* static Eina_Prefix *pfx = NULL;
*
* int main(int argc, char **argv)
* {
*
* pfx = eina_prefix_new(argv[0], main, "APPNAME", "appname", NULL,
* PACKAGE_BIN_DIR, PACKAGE_LIB_DIR,
* PACKAGE_DATA_DIR, LOCALE_DIR);
* if (!pfx) printf("ERROR: Critical error in finding prefix\n");
* printf("install prefix is: %s\n", eina_prefix_get(pfx));
* printf("binaries are in: %s\n", eina_prefix_bin_get(pfx));
* printf("libraries are in: %s\n", eina_prefix_lib_get(pfx));
* printf("data files are in: %s\n", eina_prefix_data_get(pfx));
*
* }
*
Since
1.1.0
void eina_prefix_free ( Eina_Prefix pfx)

Free the prefix object and all its contents.

Parameters
pfxThe prefix object

Free the prefix object and all its allocated content. It will be invalid to access the object after being freed.

Since
1.1.0
const char* eina_prefix_get ( Eina_Prefix pfx)

Get the prefix base directory.

Parameters
pfxThe prefix object
Returns
The base prefix (eg "/usr/local", "/usr", "/opt/appname" or "/home/user/myapps/appname" etc.) that the software resides in at runtime.
Since
1.1.0
const char* eina_prefix_bin_get ( Eina_Prefix pfx)

Get the binary installation directory.

Parameters
pfxThe prefix object
Returns
The location of installed binaries (eg "/usr/local/bin", "/usr/bin", "/opt/appname/bin", "/home/user/myapps/appname/bin" etc.).
Since
1.1.0
const char* eina_prefix_lib_get ( Eina_Prefix pfx)

Get the library installation directory.

Parameters
pfxThe prefix object
Returns
The location of installed binaries (eg "/usr/local/lib", "/usr/lib32", "/opt/appname/lib64", "/home/user/myapps/appname/lib" etc.).
Since
1.1.0
const char* eina_prefix_data_get ( Eina_Prefix pfx)

Get the data installation directory.

Parameters
pfxThe prefix object
Returns
The location of installed binaries (eg "/usr/local/share/appname", "/usr/share/appname", "/opt/appname/share/appname", "/home/user/myapps/appname/share/appname" etc.).
Since
1.1.0
const char* eina_prefix_locale_get ( Eina_Prefix pfx)

Get the locale installation directory.

Parameters
pfxThe prefix object
Returns
The location of installed binaries (eg "/usr/local/share/locale", "/usr/share/locale", "/opt/appname/share/locale", "/home/user/myapps/appname/share/locale" etc.).
Since
1.1.0