Bootstrap Arguments and Micro Deployment |
|
Contents
Abstract
While introducing a simple concept for UNO bootstrapping I noticed that there is a need for a general bootstrap-argument-passing-mechanism. At the moment, we have different locations where some kind of context knowledge for bootstrapping is needed:
- configuration:
- needs a bootstraprc (bootstrap.ini) to find the appropriate user configuration (e.g., local, portal, remote, etc.)
- currently a special file (bootstraprc) is used
- UNO:
- needs to find the appropriate rdb files to get the needed types and services (see uno default bootstrapping for a more detailed discussion), currently this has to be programmed by hand
- Java:
- needs to know the Java installation to use, this may include a shared library path and needed jar files
Different, but similar concepts are used (e.g., a file with an entry which points to a special directory). First, I would like to unify these concepts and to use one mechanism for bootstrapping. Second, I also would like to be able to configure the bootstrapping via command line arguments or via environment variables (which, for instance, may be set by setsolar). And third, I want not only micro deploy applications but also libraries/subsystems.
Micro Deployment
All the different mechanisms used to configure any subsystem have something in common, which I would like to call MICRO DEPLOYMENT. Micro Deployment allows an arbitrary component (application/library) to be configured at deployment time, so that some deployment dependent parameters do not have to be compiled in.
For example, a UNO service becomes typically deployed as a shared library. Because it needs some minimal configuration data to work properly, every application which uses the service has to pass this minimal configuration to the service. Using Micro Deployment, this burden vanishes. The installer can create a minimal configuration, which the service will use during runtime. This Micro Deployment is not only usable by shared libraries, but also by executables.
The Micro Deployment should be as flexible and as simple as possible. It is not designed to do some complex stuff during startup. Its API decomposes into three parts:
- Accessing Deployment/Bootstrap arguments for executables
- Accessing Deployment/Bootstrap arguments for shared objects/shared libraries/subsystems
- Accessing simple command line arguments
Bootstrap Arguments
A mechanism to allow differentiated access to bootstrap arguments at the runtime library (RTL) level is needed.
Passing Bootstrap Arguments
Bootstrap arguments may be passed to an executable or library, in different ways:- parameters may be passed by command line arguments
- parameters may be passed by an optional .ini/rc file
- parameters may be passed by environment variables
- parameters may be passed by inheritance
- parameters may be passed as default values for 'rtl_bootstrap_get' (see below)
Passing Bootstrap Arguments via Command Line
Bootstrap arguments passed via command line must have a special shape to be distinguishable from other command line arguments:
myapp.bin -env:UNO_SERVICES=service.rdb
Here, the bootstrap parameter "UNO_SERVICES", is passed as a command line parameter.
Passing Bootstrap Arguments via .ini/rc Files
Bootstrap arguments may be passed by an optional .ini/rc file. Using the static methods of the Bootstrap class, an .ini/rc file is searched beneath the executable. The .ini/rc file must have the same name as the executable, extended with an '.ini' for windows or an 'rc' for Unix. Any executable extension like '.bin' or '.exe' is stripped from the name:
echo 'UNO_SERVICES=service.rdb' > myapprc
./myapp.bin
The name of the .ini/rc file to use can be overwritten with the 'setIniFileName' function.
It is also possible to use a custom .ini/rc file name. Particularly, when using micro deployment for shared libraries, this makes sense.
echo 'UNO_SERVICES=service.rdb' > mylibrc ./an-app-using-mylib.so.bin
Passing Bootstrap via Inheritance
Bootstrap arguments may be inherited from an executable rc, e.g., when using custom rc file for libraries, this custom rc inherits the bootstrap variables from the executable rc file.Passing Bootstrap Arguments via Environment Variables
Bootstrap arguments may also be passed via environment variables:
setenv UNO_SERVICES service.rdb
./myapp.bin
Accessing Bootstrap Arguments via the RTL (Runtime Library)
To access bootstrap arguments a c and a c++ API exists. I just give some brief code examples of how to use the c++ API. Please have a look at the header files, bootstrap.h and bootstrap.hxx, in sal/inc/rtl for the whole API.Accessing an executable bootstrap argument:
int main() {
int result = 0;
OUString argValue;
if(Bootstrap::get(
OUString(RTL_CONSTASCII_USTRINGPARAM("aNeededParameter")),
argValue)) {
fprintf(stderr, "found the parameter, doing something...\n");
do_something();
}
else {
fprintf(stderr, "did not find the parameter, dying...\n");
result = -1;
}
return result;
}
Accessing a library bootstrap argument:
int aLibraryFunction() {
OUString libraryFileUrl;
Module::getModuleUrl((void *)aLibraryFunction, libraryFileUrl);
// cut the library extension
iniName = libraryFileUrl.copy(0,
libraryFileUrl.lastIndexOf((sal_Unicode)'.'));
// add the rc file extension
iniName += OUString(RTL_CONSTASCII_USTRINGPARAM(SAL_CONFIGFILE("")));
Bootstrap bootstrap(iniName);
int result = 0;
OUString argValue;
if(bootstrap.getFrom(
OUString(RTL_CONSTASCII_USTRINGPARAM("aNeededParameter")),
argValue))
{
fprintf(stderr, "found the parameter, doing something...\n");
do_something();
}
else {
fprintf(stderr, "did not find the parameter, dying...\n");
result = -1;
}
return result;
}
Miscellaneous
Conventions for Names of Bootstrap Arguments
Names may only include allowable characters for environment variables. This excludes '.', ' ', ';', ':' and all non-ASCII characters. Names are case insensitive.Range of Values for Bootstrap Arguments
Values may be arbitrary Unicode strings which have to be encoded using UTF8. A simple argument expansion is supported:
- Allow expansion of variables on the right side of
assignments:
MYVAR=hallo
MYMYVAR=${MYVAR}/test
The value of MYMYVAR is 'hallo/test'
-
Allow indirect expansion of variables through 'osl' profiles:
KEYVALUE=${sversionrc:versions:StarOffice6.0}
The first part of the indirection is the file to use for expansion, the second part is the section, and the third part is the key. After expansion, the variable KEYVALUE has the value of the matching key of the sversionrc.
The special characters are:
- $ - introduces a macro name, which should become expanded
- \ - quotes the next character
- \uXXXX - allows the definition of an 16 bit character (Unicode)
- {} - group the characters of macro name or an indirection to an ini-file
- - or ; or / - delimiters, which differentiate macros, which are not grouped with {}
Special Variables
There are some integral variables available:
- SYSUSERCONFIG is mapped to osl_getConfigDir
- SYSUSERHOME is mapped to osl_getHomeDir
- SYSBINDIR is mapped to the executable's directory path
- ORIGIN is mapped to the directory path of the ini/rc file itself
A special bootstrap argument is supported. This argument defines the name of the '.ini/rc' to use for finding bootstrap arguments for executables. The name of the argument is:
INIFILENAME
This argument can only be used on the command line:
./myapp -env:INIFILENAME=globalrc
Application Arguments
Application arguments are like bootstrap arguments, except, that they are not specifiable via environment variables or ini-files. Application arguments have to be given on the command line and are more like, the formerly called, command line arguments.
The following two functions give access to application arguments:
- oslProcessError SAL_CALL rtl_getAppCommandArg(sal_uInt32 nArg, rtl_uString **strCommandArg)
- sal_uInt32 SAL_CALL rtl_getAppCommandArgCount()
The function "rtl_getAppCommandArg" also supports macro expansion as defined for bootstrap arguments.
|
Author:
KayRamme
($Date: 2004/11/27 05:58:37 $)
|
