## Goals - Support only R7RS implementations - Same interface on all implementations - Some things that are procedures on one implementation are macros on other, but they must behave the same - Stability and being boring after 1.0.0 is reached ## Non goals - Compiling of used library C code at any point - That is no stubs, no C code generated by the library and so on - The pffi library itself may require compilation on installation ## Status In alpha. ### Current caveats - No way to pass structs by value - Most implementations are missing callback support - Always pass arguments to pffi functions/macros as '(1 2 3) and not (list 1 2 3) - Always pass pffi-define-callback procedure as lambda in place - No support for variadic function arguments - Can be partially worked around by defining multiple versions of same function with different number of arguments ## Roadmap For roadmap to 1.0.0 see [issues](https://todo.sr.ht/~retropikzel/r7rs-pffi?search=status%3Aopen%20label%3A%221.0.0%22) ## Feature mplementation table ## Primitives | | c-size-of | define-c-library | c-bytevector? | pffi-pointer-set! | pffi-pointer-get | define-c-procedure | pffi-define-callback | |--------------|:------------:|:-------------------:|:-------------:|:-----------------:|:----------------:|:-------------------:|:--------------------:| | Chibi | X | X | X | X | X | X | | | Chicken | X | X | X | X | X | X | X | | Cyclone | X | X | X | X | X | X | | | Gambit | X | | | | | | | | Gauche | X | X | X | X | X | X | | | Gerbil | | | | | | | | | Guile | X | X | X | X | X | X | X | | Kawa | X | X | X | X | X | X | X | | Larceny | | | | | | | | | Mosh | X | X | X | X | X | X | X | | Racket | X | X | X | X | X | X | X | | Saggittarius | X | X | X | X | X | X | X | | Skint | | | | | | | | | Stklos | X | X | X | | | | | | tr7 | | | | | | | | | Ypsilon | X | X | X | X | X | X | X | ## Built upon These features are built upon the primitives and if primitives are implemented and work, they should work too. - make-c-bytevector - make-c-null - c-null? - pffi-pointer-address - c-free - pffi-pointer-\>string - pffi-string-\>pointer - pffi-struct-make - pffi-struct-pointer - pffi-struct-offset-get - pffi-struct-get - pffi-struct-set! - pffi-array-allocate - pffi-array? - pffi-pointer-\>array - pffi-array-get - pffi-array-set! - pffi-list-\>array - pffi-array-\>list ### Not started - [LIPS](https://lips.js.org/) - Will work on nodejs by using some C FFI library from npm - Javascript side needs design - [Biwascheme](https://www.biwascheme.org/) - Will work on nodejs by using some C FFI library from npm - Javascript side needs design - [MIT-Scheme](https://www.gnu.org/software/mit-scheme/) - Need to study the implementation more - [Airship](https://gitlab.com/mbabich/airship-scheme) - Need to study the implementation more - [Other gambit targets](https://gambitscheme.org/) - Gambit compiles to different targets other than C too, for example Javascript. It would be cool and interesting to see if this FFI could also support some of those - When LIPS and Biwascheme Javascript side is done then Gambit should be done too - [s48-r7rs](https://codeberg.org/prescheme/s48-r7rs) - Need to study the implementation more - [prescheme](https://codeberg.org/prescheme/prescheme) - Need to study the implementation more ### Other - [s7](https://scheme.fail://ccrma.stanford.edu/software/snd/snd/s7.html) - Propably does not need FFI as it is embeddable only - [Loko](https://scheme.fail/) - Desires no C interop, I can respect that ## Documentation ### Dependencies Some implementations have extra dependencies/requirements beyond just the library. #### Chibi Building depends on libffi. Debian/Ubuntu/Mint install with: apt install libffi-dev #### Chicken Chicken needs r7rs egg installed. Install it with: chicken-install r7rs #### Gauche Building depends on libffi. Debian/Ubuntu/Mint install with: apt install libffi-dev #### Racket Needs [racket-r7rs](https://github.com/lexi-lambda/racket-r7rs), install with: raco pkg install --auto r7rs #### Kawa Kawa Needs at least Java version 22 these flags before any other arguments: - \-J--add-exports=java.base/jdk.internal.foreign.abi=ALL-UNNAMED - \-J--add-exports=java.base/jdk.internal.foreign.layout=ALL-UNNAMED - \-J--add-exports=java.base/jdk.internal.foreign=ALL-UNNAMED - \-J--enable-native-access=ALL-UNNAMED If you are running kawa.jar with plain java then give same arguments to java without the -J prefix. ### Installation Since the project is under active development is best to clone it from git, ### Project local #### Linux Assuming you have a project and your libraries live in directory called snow in it: git clone https://git.sr.ht/~retropikzel/r7rs-pffi mkdir -p snow cp -r r7rs-pffi/retropikzel snow/ cd snow/retropikzel/pffi make #### Windows There is no build scripts yet for Windows, that said many implementations work without compiling anything. If you run this and it says "There is notching to build for SCHEME" then you should be good to go. ### System global Still work in progress. ## Reference ### Types Types are given as symbols, for example 'int8 or 'pointer. - int8 - uint8 - int16 - uint16 - int32 - uint32 - int64 - uint64 - char - unsigned-char - short - unsigned-short - int - unsigned-int - long - unsigned-long - float - double - pointer - callback - Callback function ### Types ### Environment variables Setting environment variables like this on Windows works for this library: set "PFFI_LOAD_PATH=C:\Program Files (x86)/foo/bar" #### PFFI\_LOAD\_PATH To add more paths to where pffi looks for libraries set PFFI\_LOAD\_PATH to paths separated by ; on windows, and : on other operating systems. ### Procedures and macros Some of these are procedures and some macros, it might also change implementation to implementation. #### pffi-init **pffi-init** Always call this first, on most implementation it does nothing but some implementations might need initialisation run. #### c-size-of **c-size-of** object -> number Returns the size of the pffi-struct, pffi-enum or pffi-type. #### pffi-align-of **pffi-align-of** type -> number Returns the align of the type. #### define-c-library **define-c-library** headers shared-object-name [options] -> object Load given shared object automatically searching many predefined paths. Takes as argument a list of C headers, these are for the compiler ones. And an shared-object name, used by the dynamic FFI's. The name of the shared object should not contain suffix like .so or .dll. Nor should it contain any prefix like "lib". Additional options argument can be provided, theys should be a pair with a keyword. The options are: - additional-versions - Search for additional versions of shared object, given shared object "c" and additional versions "6" "7" on linux the files "libc", "libc.6", "libc.7" are searched for. - Can be either numbers or strings - additional-paths - Give additional paths to search shared objects for Example: (cond-expand (windows (define-c-library libc-stdlib '("stdlib.h") "ucrtbase" '((additional-versions ("0" "6")) (additiona-paths ("."))))) (else (define-c-library libc-stdlib (list "stdlib.h") "c" '((additional-versions ("0" "6")) (additiona-paths (".")))))) #### Notes - Do not cond-expand inside the arguments, that might lead to problems on some implementations. - Do not store options in variables, that might lead to problems on some implementations. - Do pass the headers using quote - As '(... and not (list... - Do pass the options using quote - As '(... and not (list... #### make-c-null **make-c-null** -> pointer Returns a new NULL pointer. #### c-null? **c-null?** pointer -> boolean Returns #t if given pointer is null pointer, #f otherwise. #### make-c-bytevector (make-c-bytevector *k*) (make-c-bytevector *k* *fill*) Returns a newly allocated C bytevector(pointer) of length k. If byte is given, then all elements of the C bytevector are initialized to byte, otherwise the contents of each element are unspecified. #### pffi-pointer-address **pffi-pointer-address** pointer -> pointer Returns the address of given pointer inside a pointer. This is used when passing pointers to pointers to foreign procedures. This is similar to the c's &. One **important difference** is that after you have passed a pointer to the procedure you must get value from it back to the pointer which address you are passing. Example: (define input-pointer (make-c-bytevector )) (define input-pointer-address (pffi-pointer-address input-pointer)) ( input-pointer-address) (set! input-pointer (pffi-pointer-get input-pointer-address 'pointer 0)) #### c-bytevector? **c-bytevector?** object -> boolean Returns #t if given object is pointer, #f otherwise. #### c-free **c-free** pointer Frees given pointer. #### pffi-pointer-set! **pffi-pointer-set!** pointer type offset value Sets the value on a pointer on given offset. For example: (define p (make-c-bytevector 128)) (pffi-pointer-set! p 'int 64 100) Would set the offset of 64, on pointer p to value 100. #### pffi-pointer-get **pffi-pointer-get** pointer type offset -> object Gets the value from a pointer on given offset. For example: (define p (make-c-bytevector 128)) (pffi-pointer-set! p 'int 64 100) (pffi-pointer-get p 'int 64) > 100 #### utf8->c-bytevector **utf8->c-bytevector** string -> pointer Makes pointer out of a given string. #### c-bytevector->string **c-bytevector->sring** pointer -> string Makes string out of a given pointer. #### pffi-struct-make **pffi-struct-make** c-type members . pointer -> pffi-struct Creates a new pffi-struct and allocates pointer for it. The members argument is a list of member names and types. For example: (define color (pffi-struct-make 'color '((int8 . r) (int8 . g) (int8 . b) (int8 .a )))) (define test (pffi-struct-make "struct test" '((int8 . r) (int8 . g) (int8 . b) (int8 .a )))) C-type argument can be symbol or a string. #### pffi-struct-pointer **pffi-struct-pointer** pffi-struct -> pointer Returns the pointer that holds the struct content. You need to use this when passing a struct as a pointer to foreign functions. (define s (pffi-struct-make 'test '((int . r) (int . g) (int . b)))) (pffi-struct-pointer s) #### pffi-struct-offset-get **pffi-struct-offset-get** member-name -> number Returns the offset of a struct member with given name. #### pffi-struct-get **pffi-struct-get** pffi-struct member-name -> object Returns the value of the givens struct member. #### pffi-struct-set! **pffi-struct-set!** pffi-struct member-name value Sets the value of the givens struct member. It is up to you to make sure that the type of value is correct. #### pffi-array-allocate **pffi-array-allocate** type size Allocates pointer array of given type and size. #### pffi-array-pointer **pffi-array-pointer** array Returns the pointer of the array. #### pffi-array? **pffi-array?** object Returns #t of given object is array, #f otherwise. #### pffi-pointer->array **pffi-pointer->array** pointer type size Converts given pointer to an array of giben type and size. #### pffi-array-get **pffi-array-get** array index Returns the value of given index from given array. #### pffi-array-set! **pffi-array-set!** array index value Sets the given value of given index in given array. #### pffi-list->array **pffi-list->array** type list Converts given list into C array of given type. #### pffi-array->list **pffi-array->list** type list length Converts given C array into list of given type and length. #### define-c-procedure **define-c-procedure** scheme-name shared-object c-name return-type argument-types Defines a new foreign function to be used from Scheme code. For example: (cond-expand (windows (define-c-library libc-stdlib '("stdlib.h") "ucrtbase" '(""))) (else (define-c-library libc-stdlib '("stdlib.h") "c" '("" "6")))) (define-c-procedure c-puts libc-stdlib 'puts 'int '(pointer)) (c-puts "Message brought to you by FFI!") #### pffi-define-callback **pffi-define-callback** scheme-name return-type argument-types procedure Defines a new Sceme function to be used as callback to C code. For example: ; Load the shared library (cond-expand (windows (define-c-library libc-stdlib '("stdlib.h") "ucrtbase" '())) (else (define-c-library '("stdlib.h") "c" '("" "6")))) ; Define C function that takes a callback (define-c-procedure qsort libc-stdlib 'qsort 'void '(pointer int int callback)) ; Define our callback (pffi-define-callback compare 'int '(pointer pointer) (lambda (pointer-a pointer-b) (let ((a (pffi-pointer-get pointer-a 'int 0)) (b (pffi-pointer-get pointer-b 'int 0))) (cond ((> a b) 1) ((= a b) 0) ((< a b) -1))))) ; Create new array of ints to be sorted (define array (make-c-bytevector (* (c-size-of 'int) 3))) (pffi-pointer-set! array 'int (* (c-size-of 'int) 0) 3) (pffi-pointer-set! array 'int (* (c-size-of 'int) 1) 2) (pffi-pointer-set! array 'int (* (c-size-of 'int) 2) 1) (display array) (newline) ;> (3 2 1) ; Sort the array (qsort array 3 (c-size-of 'int) compare) (display array) (newline) ;> (1 2 3)