Question

This is a bit esoteric, but there have to be a few people here who know how OS X’s Carbon Component Manager works. I’ve made a couple of little apps to play around with making Components (see here for some background). Actually, one of the apps is a sample program straight from Apple called ‘Fiendishthngs’. It lists all the Components that the Component Manager is making available. My program is a simple little thing that registers a Component, lists all the Components that the Component Manager has, and then waits around indefinately (to avoid purging the Component that it registered).

On my system, the Component Manager is tracking 873 Components (mostly codecs of one sort of another). My program that registers a Component registers it, and then counts 874 Components because it just registered one itself, of course). Here’s the source:

void RegisterBasicComponent()
{
    ComponentDescription desc;
    desc.componentType = kMyComponentType;
    desc.componentSubType = kMyComponentSubType;
    desc.componentManufacturer = kMyComponentManufacturer;
    desc.componentFlags = 0;
    desc.componentFlagsMask = cmpIsMissing;

    ComponentRoutineUPP MyComponentRoutineUPP 
        = NewComponentRoutineUPP( &MyComponentRoutineProc );

    //  Handle name_handle = NewHandle( sizeof( kMyComponentName ) );
    //strcpy( *(char**)name_handle, kMyComponentName );

    //RegisterComponent( &desc, MyComponentRoutineUPP, registerComponentGlobal, name_handle, NULL, NULL );
    Component component = RegisterComponent( &desc, MyComponentRoutineUPP, registerComponentGlobal, NULL, NULL, NULL );
    if ( NULL != component )
        printf("The registration seems to have worked!\n");
    else
        printf("Nope - didn't work for some reason.\n");

}


int main( void )
{
    RegisterBasicComponent();

    ComponentDescription looking;
//  OSType              componentType;          /* A unique 4-byte code indentifying the command set */
//  OSType              componentSubType;       /* Particular flavor of this instance */
//  OSType              componentManufacturer;  /* Vendor indentification */
//  UInt32              componentFlags;         /* 8 each for Component,Type,SubType,Manuf/revision */
//  UInt32              componentFlagsMask;     /* Mask for specifying which flags to consider in search, zero during registration */
    looking.componentType           = kAnyComponentType;          
    looking.componentSubType        = kAnyComponentSubType;
//  looking.componentSubType        = kComponentResourceType
    looking.componentManufacturer   = kAnyComponentManufacturer;
    looking.componentFlags          = 0;
    looking.componentFlagsMask      = cmpIsMissing;

    long numComponents = CountComponents ( &looking );

    printf("Found %ld components.\n", numComponents);

    Component component = 0;
    int i = 0;
    while (true) 
    {
        component = FindNextComponent(component, &looking);

        if ( 0 == component )
            break;

        ComponentDescription desc;
        Handle componentName = NewHandle(256);
        Handle componentInfo = NewHandle(1024);
        Handle componentIcon = 0;
        OSErr err = GetComponentInfo( component,
                                &desc,
                                componentName,
                                componentInfo,
                                componentIcon );

        if ( err != noErr )
        {
            printf("Couldn't find any info on component %d of %ld in list!\n", i
                   , numComponents);
            break;
        }


        printf( "%d of %ld: '%c%c%c%c', '%c%c%c%c', '%c%c%c%c', '%s'\n", 
            i, numComponents,
            SPLAT_WORD( desc.componentManufacturer ),
            SPLAT_WORD( desc.componentType ),
            SPLAT_WORD( desc.componentSubType ),
            *componentName );

        RecoverHandle( *componentName );
        RecoverHandle( *componentInfo );

        ++i;
    }

    while (true) 
    {
        printf("Waiting around for someone to use me...\n");
        sleep( 3 );
    }
}

Anyways, when I run this, keep it running (so the Component would presumably stay registered with the Component Manager), and then run Fiendishthngs, Fiendishthngs can’t see my test Component that I register – it only sees 873 Components. The ‘registerComponentGlobal’ flag passed into RegisterComponent() is supposed to make the Component available to other processes, but it seems like something is going awry.

Any ideas?

Answer 1

Well, I left this issue behind, resigning myself to the fact that OS X’s Component Manager probably doesn’t support the ‘global’ option anymore.

This would make a lot of sense, really. Making your component ‘global’ from your process to other processes would require out-of-process call marshalling, like with RPC, with OS X. On the other hand, in OS 9 and earlier, it would make perfect sense, given that all processes lived in a common address space. For OS 9 it would be trivial to make a component globally available to all processes.

Anyways, today I was disassembling RegisterComponentFileRefEntries() where the relevant code seems to reside, and sure enough, I saw this in the pre-amble to the function (the comments are mine):

0x9841a026  <+0018>  mov    eax, DWORD PTR [ebp+0x8]        // load param spec
0x9841a029  <+0021>  mov    DWORD PTR [ebp-0xdc],eax        // local spec = param spec
0x9841a02f  <+0027>  mov    edx,DWORD PTR [ebp+0x10]        // load param toRegister
0x9841a032  <+0030>  mov    DWORD PTR [ebp-0xe0],edx        // local toRegister = param toRegister

The signature for RegisterComponentFileRefEntries is

extern OSErr 
RegisterComponentFileEntries(
  const FSSpec *                spec,
  short                         global,
  const ComponentDescription *  toRegister,          /* can be NULL */
  UInt32                        registerCount)   

The only 2 parameters that RegisterComponentFileRefEntries bothers with are spec (at ebp+0x8) and toRegister (at ebp+0x10). global (at ebp+0xc) and registerCount (at ebp+0x14) are completely ignored.