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Diffstat (limited to 'perl.h')
| -rw-r--r-- | perl.h | 74 |
1 files changed, 74 insertions, 0 deletions
@@ -25,6 +25,80 @@ #endif /* PERL_FOR_X2P */ #ifdef PERL_OBJECT + +/* PERL_OBJECT explained - DickH and DougL @ ActiveState.com + +Defining PERL_OBJECT turns on creation of a C++ object that +contains all writable core perl global variables and functions. +Stated another way, all necessary global variables and functions +are members of a big C++ object. This object's class is CPerlObj. +This allows a Perl Host to have multiple, independent perl +interpreters in the same process space. This is very important on +Win32 systems as the overhead of process creation is quite high -- +this could be even higher than the script compile and execute time +for small scripts. + +The perl executable implementation on Win32 is composed of perl.exe +(the Perl Host) and perlX.dll. (the Perl Core). This allows the +same Perl Core to easily be embedded in other applications that use +the perl interpreter. + ++-----------+ +| Perl Host | ++-----------+ + ^ + | + v ++-----------+ +-----------+ +| Perl Core |<->| Extension | ++-----------+ +-----------+ ... + +Defining PERL_OBJECT has the following effects: + +PERL CORE +1. CPerlObj is defined (this is the PERL_OBJECT) +2. all static functions that needed to access either global +variables or functions needed are made member functions +3. all writable static variables are made member variables +4. all global variables and functions are defined as: + #define var CPerlObj::Perl_var + #define func CPerlObj::Perl_func + * these are in objpp.h +This necessitated renaming some local variables and functions that +had the same name as a global variable or function. This was +probably a _good_ thing anyway. + + +EXTENSIONS +1. Access to global variables and perl functions is through a +pointer to the PERL_OBJECT. This pointer type is CPerlObj*. This is +made transparent to extension developers by the following macros: + #define var pPerl->Perl_var + #define func pPerl->Perl_func + * these are done in ObjXSub.h +This requires that the extension be compiled as C++, which means +that the code must be ANSI C and not K&R C. For K&R extensions, +please see the C API notes located in Win32/GenCAPI.pl. This script +creates a PerlCAPI.lib that provides a K & R compatible C interface +to the PERL_OBJECT. +2. Local variables and functions cannot have the same name as perl's +variables or functions since the macros will redefine these. Look for +this if you get some strange error message and it does not look like +the code that you had written. This often happens with variables that +are local to a function. + +PERL HOST +1. The perl host is linked with perlX.lib to get perl_alloc. This +function will return a pointer to CPerlObj (the PERL_OBJECT). It +takes pointers to the various PerlXXX_YYY interfaces (see ipdir.h for +information on this). +2. The perl host calls the same functions as normally would be +called in setting up and running a perl script, except that the +functions are now member functions of the PERL_OBJECT. + +*/ + + class CPerlObj; #define STATIC |