Re: [Chicken-users] Basic FFI Principle in Chicken
Hey Chris, I though I'd mention the srfi-4 unit and it's u32vector. This may come in handy for your particular struct. While make-blobs are great for allocating managed memory for arbitrary structs, you can sometimes use make-s32vector, for example, where the struct is basically an array like yours. Note that this may not be a good idea if your struct members are just using int because you wouldn't know if it's a s32vector or a s64vector. Also, your foreign-type would go from (pointer (struct color)) to a u32vectorwhich means you may have to cast it to a (struct color*) in C. However, it does make extracting the individual color-components much easier than having to work with raw blobs. Because size of an int can generally be either 32 or 64-bit depending on your architecture, the srfi-4 vectors are possible better suited for floats and doubles where the sizes are all set. It's worth knowing about them though. Cheers, K. On Fri, Sep 6, 2013 at 12:23 PM, Chris Mueller ruunsm...@gmail.com wrote: On 06.09.2013 09:07, Peter Bex wrote: On Fri, Sep 06, 2013 at 08:52:08AM +0200, Chris Mueller wrote: Hope its not too basic for you. :) Never, user questions are what this mailing list is for! I hope my answers make a little sense. Definitely! This is very helpful. I will immediately check and use this. Now it also makes sense for me what's one of the intensions behind blobs in the documentation/wiki. Never thought it can be used for memory allocation in C interfaces :) Thanks Chris __**_ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/**mailman/listinfo/chicken-usershttps://lists.nongnu.org/mailman/listinfo/chicken-users ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
Re: [Chicken-users] Basic FFI Principle in Chicken
On Sat, Sep 07, 2013 at 12:48:27PM +0200, Kristian Lein-Mathisen wrote: Note that this may not be a good idea if your struct members are just using int because you wouldn't know if it's a s32vector or a s64vector. Also, your foreign-type would go from (pointer (struct color)) to a u32vectorwhich means you may have to cast it to a (struct color*) in C. However, it does make extracting the individual color-components much easier than having to work with raw blobs. Because size of an int can generally be either 32 or 64-bit depending on your architecture, the srfi-4 vectors are possible better suited for floats and doubles where the sizes are all set. It's worth knowing about them though. Good call! There's also the bitstring egg which makes destructuring blobs into component values pretty easy as well. Cheers, Peter -- http://www.more-magic.net ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
Re: [Chicken-users] Basic FFI Principle in Chicken
Kristian Lein-Mathisen scripsit: Because size of an int can generally be either 32 or 64-bit depending on your architecture, the srfi-4 vectors are possible better suited for floats and doubles where the sizes are all set. It's worth knowing about them though. Actually, there are essentially no architectures on which int is anything but 32 bits: unless you have an ancient Cray running Unicos (modern ones run Linux), a (now-defunct) HAL Systems port of Solaris, or an IBM PC/AT, you don't have to worry about that. What does vary is long, which is 32 bits on 32-bit systems and Win64, and 64 bits on non-Windows 64-bit systems. -- John Cowanhttp://ccil.org/~cowanco...@ccil.org SAXParserFactory [is] a hideous, evil monstrosity of a class that should be hung, shot, beheaded, drawn and quartered, burned at the stake, buried in unconsecrated ground, dug up, cremated, and the ashes tossed in the Tiber while the complete cast of Wicked sings Ding dong, the witch is dead. --Elliotte Rusty Harold on xml-dev ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
