On Thu, May 7, 2015 at 8:53 AM, Holger Freyther <hol...@freyther.de> wrote:
> Good Morning, > > I used NB to access openlog, closelog and syslog of libc and I am not sure > if I got it right but didn’t really get further by browsing > testcases/reading the > examples. > > openlog(3) takes an “char *ident” as first parameter and the caller needs > to > make sure that the string passed remains valid until closelog is called. > > My binding looks like this: > > c_openlog: ident opt: aOpt facility: aFac > "openlog(const char *ident, int logopt, int facility);" > <primitive: #primitiveNativeCall module: #NativeBoostPlugin error: > errorCode> > ^self nbCall: #(void openlog(char *ident, int aOpt, int aFac)) > > And I call it like this: > > Identity := anIdentity asNBExternalString. > self c_openlog: Identity opt: anOption facility: aFacility. > > The things I am not sure with: > > 1.) is it right to use “char *ident” instead of “String ident”? “String” > will copy > the string by value but the pointer passed to openlog would be a pointer > from > the C callstack? > asNBExternalString will do this with a NBExternalAddress: fromString: aString | result | result := NativeBoost allocate: aString size + 1. (self assert: result notNil). result writeString: aString. ^ result writeString: aString "write a null-terminated byte string to receiver's address" | str | str := aString copyWith: (Character value: 0). NativeBoost memCopy: str asByteArray to: self size: str size. So, yes, it allocates heap memory basicAllocate: numBytes "Allocate a memory block with given size in bytes, answer an NBExternalAddress instance - address to the beginning of memory block" | addr | addr := heap allocate: numBytes. addr = 0 ifTrue: [ ^ nil ]. ^ NBExternalAddress value: addr char * looks a null terminated string, which str := aString copyWith: (Character value: 0). provides So, asNBExternalString is compatible with the char * > 2.) Am I right with the call to asNBExternalString? > Should work. > > 3.) How does this integrate with GC and image quit/image resume? E.g. I > could > use >>#freeAfterUse and if I do “Identity := nil” at some point free > should be called > on the old string. Is there anything in the system that sets the address > to 0x0 after > the image is starting? > As the thing is a NBExternalAddress, there is a finalize self free which will do the "free" call when the Identity will be gc'd. As for the statup/shutdown, maybe startUp: resuming shutDown: quitting methods on the class side of your facility will do the necessary things. I am pretty sure the address would be pointing to invalid crap upon image restart. Doing free too many times will just raise an error I guess (which you can catch). free: address sema critical: [ | block | block := reservedBlocks removeKey: address ifAbsent: [ self error: 'Unable to find a memory block with given address' ]. block makeFreeFor: self ] HTH Phil > > thanks > holger >
