Re: Basic Library Paths (was Re: ICU data file location issues)

[Gordon Henriksen]

On Saturday, April 17, 2004, at 10:35 , Gordon Henriksen wrote:

Which suggests to me a linked list of resource resolvers. First one in 
the chain to return a file handle to the data or PBC wins. The head of 
parrot's own "system" chain would be available to be appended to any 
other chains that wanted it.
And the more I mull this over, the more I really come up with maybe 4 
slots in the search chain which are logically important. The order is up 
for debate, but they all need to be in there (whenever they apply, that 
is).

1.      Paths relative to the PBC binary which is searching for a library.
2.      Paths relative to the embedding application.
3.      Paths relative to parrot itself (be that libparrot.shlib or parrot).
4.      Paths to "system" libraries as specified by the administrator.
When searching for resources, only #1 should be used. Here are some 
examples:

PBC File: (whatever)
Host app: /usr/local/bin/parrot
Parrot: /usr/local/lib/libparrot.shlib
Consider searches for:
        icu.dat
Search path:
1.      /usr/local/shared   # Relative to executable
PBC File: D:\inetpub\wwwroot\example.pbchtml
Host app: C:\Apache\libexec\httpd.exe
Parrot: C:\Parrot\lib
Consider searches for:
        icu.dat
        mod_parrot.pbc
        My::WWWUtil.pbc
        Time::HiRes.pbc
Search path:
        D:\inetpub\wwwroot{,\lib,\..\lib}  # Relative to PBC
        C:\Apache\libexec{,\lib,\..\lib}  # Relative to host app
        C:\CPAN\lib  # System libraries
        C:\Parrot\lib  # Relative to parrot
PBC File: ./bin/fib
Host app: /home/me/bin/parrot
Parrot: /home/me/bin/parrot
Consider searches for:
        icu.dat
        Time::HiRes.pbc
        fib.parrot_resource_file
One possible search path:
        ./bin/{,/lib,/../lib}  # Relative to PBC
        /usr/local/lib  # System libraries
        /home/me/lib  # Relative to parrot


The scenario which gives me a little bit of heartburn is one like this, 
though:

Consider, say, an e-commerce site package. Call it OneStep::ECS. Runs 
under mod_parrot in Apache. Has hooks to load plugins:

	• Third-party plugins to provide connectivity to payment processing 
engines (call it OneStep::VeriSignPayflow.pbc).
	• First-party plugins allowing the customer to integrate his 
storefront with his database (call it 
MySite::OneStepECSCustomizations.pbc).

Now consider searches for VeriSign::PayflowPro.pbc, PayFlowPro.dll, 
MySite::CRM.pbc, MySite::Reporting.pbc, mysite_logo.png, 
Time::HiRes.pbc, libparrot.pbc, CGI.pbc....

So maybe some libraries are "hosts" and need to be included in the 
search paths of libraries which are linked to them. One could even look 
at libparrot that way, in which case the search path model becomes:

        Paths relative to this PBC file.
        Paths relative to its hosts.
        Paths relative to its hosts' hosts.
        Paths relative to its hosts' hosts' hosts.
        ...
        Paths configured by the system administrator.
—

Gordon Henriksen
[EMAIL PROTECTED]