Resource compiler

Resource files contain data in numbered resources. The index can be used to efficiently find a resource given its numeric id. There can be from 1 to 4095 resources in a resource file. A resource file has the following format:

There are four main reasons for using resource files:

• resource files make it easier for applications to run in more than one language. The resource text may be changed and the resources recompiled, without altering or recompiling the C++ program.

• they are convenient for specifying and modifying some aspects of application layout and design. Applications that use the Uikon framework must have a resource file.

• keeping data in a separate resource file may reduce RAM requirements because text strings will only be loaded into RAM when needed

• resource files may be compressed, thereby reducing program size

Resource files are produced by compiling a text source file, extension rss, using the EPOC resource compiler, rcomp. rcomp is not however usually invoked directly:

For C++ programmer's, invocation of the resource compiler is performed automatically as part of the build process by abld or by the Microsoft Visual C++ IDE. An alternative is to use the command-line tool epocrc: see Resource compiler with preprocessing epocrc.bat.

Resource compilation is a two-stage process:

• the pre-processor stage

• the main resource compilation stage

The pre-processing stage operates on the resource file statements and uses the cpp pre-processor supplied with the GNU C++ compiler. The GCC compiler is located in the directory \epoc32\gcc\bin, as downloaded from the SDK. If you also have a cpp from a different vendor on your system, make sure that the directory in which it resides follows \epoc32\gcc\bin in the path.

The main resource compilation stage generates:

• the header file, conventionally given the extension rsg

• the compiled resource file, extension rsc

The header file contains #define statements give a symbolic name for the index into the resource file, so that your source code can be independent of the number and order of resources within the file. For a named resource such as:

RESOURCE TBUF r_eik_bafl_error_offset { buf="Wrong format resource file"; }

the generated header file will have a #define such as:

#define R_EIK_BAFL_ERROR_OFFSET 0xf3b045

where the number is a resource ID which encodes the resource index, and is suitable for passing to the C++ function RResourceFile::AllocReadLC().

In the course of project development, changes to the resource file may not always result in changes to the set of #define statements generated. If there is no change, the rsg file is not rebuilt, thereby avoiding unnecessary re-compilation and linking.

The compiled resource file contains the resource data, and is the file that is referred to at run-time by the application.