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#1
newLISP in the real world / Bug in struct with float arguments?
January 11, 2022, 02:18:15 PM
Hello,



I love newLISP and I'm trying to use it for some graphics programming. So I'm writing a FFI module for the raylib library.



I've encountered an odd behavior of struct: If I define a 'struct' with one or more floats and pass it to 'pack', the float values are stored as zeroes. But surprisingly the same struct works well with 'unpack'. Here is an example:



(struct 'Vector2 "float" "float")

(pack Vector2 200 200) => returns "0000000000000000", which is wrong!

(pack "ff" 200 200) => returns "0000HC0000HC", which is what 'pack Vector2...' also should return

(unpack Vector2 (pack "ff" 200 200)) => returns (200 200) correctly!



I'm using newLISP 10.7.5 64-bit on Arch Linux with ffi and UTF-8 support enabled.



Is there a bug or am I doing something wrong?



Thanks in advance

Alfonso
#2
Anything else we might add? / Reuse "pack"ed buffers?
March 28, 2021, 09:41:35 AM
Hello,

is there a way to re-utilize a buffer created with "pack"? What I mean is:
[list=]
  • You create a buffer using "pack" with some values
    • [/list]
    [list=]
  • You keep the address of the buffer in a symbol (maybe a default functor) so it isn't deleted automatically
    • [/list]
    [list=]
  • You "repack" the existing buffer passing the symbol or the address stored in it, writing new values into the buffer, but without allocating new memory
    • [/list]
    I think this possibility would be useful f.eg. in working with C libraries that make heavy use of buffer pointers (OpenGL, SDL etc.) and could play nicely with "struct".

    Thanks and best regards

    Alfonso
    Pages1