356 lines
12 KiB
Markdown
356 lines
12 KiB
Markdown
---
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title: foreign-c a portable foreign function interface for R7RS Schemes
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version: 0.10.0
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---
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# foreign-c
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foreign-c is a C foreign function interface (FFI) library for R7RS Schemes. It
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is portable in the sense that it supports multiple implementations, as opposed
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to being portable by conforming to some specification.
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[Issue tracker](https://sr.ht/~retropikzel/foreign-c/trackers)
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[Maling lists](https://sr.ht/~retropikzel/foreign-c/lists)
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- [Installation](#installation)
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- [Documentation](#documentation)
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- [Types](#types)
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- [Primitives 1](#primitives-1)
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- [Primitives 2](#primitives-2)
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- [c-bytevector](#c-bytevector)
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- [Accessors](#accessors)
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- [Environment variables](#environment-variables)
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## Implementation support tables
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### Primitives 1 table
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| | c-size-of | c-bytevector-u8-set! |c-bytevector-u8-ref | define-c-library | c-bytevector? | define-c-procedure |
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|------------------|:------------:|:--------------------:|:------------------:|:-------------------:|:-------------:|:-------------------:|
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| **Chibi** | X | X |X | X | X | X |
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| **Chicken** | X | X |X | X | X | X |
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| **Gauche** | X | X |X | X | X | X |
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| **Guile** | X | X |X | X | X | X |
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| **Kawa** | X | X |X | X | X | X |
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| **Mosh** | X | X |X | X | X | X |
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| **Racket** | X | X |X | X | X | X |
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| **Saggittarius** | X | X |X | X | X | X |
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| **Stklos** | X | X |X | X | X | X |
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| **Ypsilon** | X | X |X | X | X | X |
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### Primitives 2 table
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| | define-c-callback |
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|------------------|:-----------------:|
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| Chibi | |
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| **Chicken** | X |
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| Gauche | |
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| **Guile** | X |
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| Kawa | |
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| **Mosh** | X |
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| **Racket** | X |
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| **Saggittarius** | X |
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| Stklos | |
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| **Ypsilon** | X |
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### Test files pass
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| | primitives.scm | addressof.scm | callback.scm |
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|------------------|:--------------:|:-------------:|-------------:|
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| Chibi | X | X | |
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| **Chicken** | X | X | X |
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| Gauche | X | X | |
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| **Guile** | X | X | X |
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| Kawa | X | X | |
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| Mosh | X | X | |
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| Racket | X | | |
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| **Saggittarius** | X | X | X |
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| Stklos | X | X | |
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| Ypsilon | X | X | |
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### Installation
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Either download the latest release from
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[https://git.sr.ht/~retropikzel/foreign-c/refs](https://git.sr.ht/~retropikzel/foreign-c/refs) or git clone
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, preferably with a tag, and copy the _foreign_ directory to your library
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directory.
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Example assuming libraries in directory _snow_:
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git clone https://git.sr.ht/~retropikzel/foreign-c --branch LATEST_VERSION
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mkdir -p snow
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cp -r foreign-c/foreign snow/
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make -C snow/foreign/c SCHEME_IMPLEMENTATION_NAME
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With most implementations the make command does not compile anything. When that
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is the case it will say "Nothing to build on SCHEME\_IMPLEMENTATION\_NAME."
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## Documentation
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### Types
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Types are given as symbols, for example 'int8 or 'pointer.
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- int8
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- uint8
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- int16
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- uint16
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- int32
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- uint32
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- int64
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- uint64
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- char
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- unsigned-char
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- short
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- unsigned-short
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- int
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- unsigned-int
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- long
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- unsigned-long
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- float
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- double
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- pointer
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- c-bytevector on Scheme side
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- callback
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- Callback function
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- void
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- Can not be argument type, only return type
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### Primitives 1
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(**c-type-size** _type_)
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Returns the size of given C type.
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(**define-c-library** _scheme-name_ _headers_ _object-name_ _options_)
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Takes a scheme-name to bind the library to, list of C headers as
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strings, shared-object name and options.
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The C header strings should not contain "<" or ">", they are added
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automatically.
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The name of the shared object should not contain suffix like .so or .dll.
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Nor should it contain any prefix like "lib".
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Options:
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- additional-versions
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- Search for additional versions of shared object, given shared object "c"
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and additional versions "6" "7" on linux the files "libc", "libc.6",
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"libc.7" are searched for.
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- Can be either numbers or strings
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- additional-paths
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- Give additional paths to search shared objects from
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Example:
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(cond-expand
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(windows (define-c-library libc-stdlib
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'("stdlib.h")
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"ucrtbase"
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'((additional-versions ("0" "6"))
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(additiona-paths (".")))))
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(else (define-c-library libc-stdlib
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(list "stdlib.h")
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"c"
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'((additional-versions ("0" "6"))
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(additiona-paths ("."))))))
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#### Notes
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- Do not cond-expand inside the arguments, that might lead to problems on some
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implementations.
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- Do not store options in variables, that might lead to problems on some
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implementations.
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- Pass the headers using quote
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- As '(...) and not (list...)
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- Pass the options using quote
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- As '(...) and not (list...)
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(**define-c-procedure** _scheme-name_ _shared-object_ _c-name_ _return-type_
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_argument-type_)
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Takes a scheme-name to bind the C procedure to, shared-object where the function
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is looked from, c-name of the function as symbol, return-type and argument-types.
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Defines a new foreign function to be used from Scheme code.
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Example:
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(cond-expand
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(windows (define-c-library libc-stdlib '("stdlib.h") "ucrtbase" '()))
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(else (define-c-library libc-stdlib '("stdlib.h") "c" '("6"))))
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(define-c-procedure c-puts libc-stdlib 'puts 'int '(pointer))
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(c-puts "Message brought to you by foreign-c!")
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#### Notes
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- Pass the return-types using quote
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- As '(...) and not (list...)
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(**c-bytevector?** _obj_)
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Returns **#t** if _obj_ is c-bytevector, otherwise returns **#f**.
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(**c-bytevector-u8-set!** _c-bytevector_ _k_ _byte_)
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If K is not a valid index of c-bytevector the behaviour is undefined.
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Stores the byte in element k of c-bytevector.
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(**c-bytevector-u8-ref** _c-bytevector_ _k_)
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If K is not a valid index of c-bytevector the behaviour is undefined.
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Returns the byte at index k of c-bytevector.
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(**c-bytevector-pointer-set!** _c-bytevector_ _k_ _pointer_)
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If K is not a valid index of c-bytevector the behaviour is undefined.
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Stores the pointer(which is also c-bytevector) in element k of c-bytevector.
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(**c-bytevector-pointer-ref** _c-bytevector_ _k_ _pointer_)
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If K is not a valid index of c-bytevector the behaviour is undefined.
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Returns the pointer(which is also c-bytevector) at index k of c-bytevector.
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### Primitives 2
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(**define-c-callback** _scheme-name_ _return-type_ _argument-types_ _procedure_)
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Takes scheme-name to bind the Scheme procedure to, return-type, argument-types
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and procedure as in place lambda.
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Defines a new Sceme function to be used as callback to C code.
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Example:
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; Load the shared library
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(cond-expand
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(windows (define-c-library libc-stdlib '("stdlib.h") "ucrtbase" '()))
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(else (define-c-library '("stdlib.h") "c" '("" "6"))))
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; Define C function that takes a callback
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(define-c-procedure qsort libc-stdlib 'qsort 'void '(pointer int int callback))
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; Define our callback
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(pffi-define-callback compare
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'int
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'(pointer pointer)
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(lambda (pointer-a pointer-b)
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(let ((a (pffi-pointer-get pointer-a 'int 0))
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(b (pffi-pointer-get pointer-b 'int 0)))
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(cond ((> a b) 1)
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((= a b) 0)
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((< a b) -1)))))
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; Create new array of ints to be sorted
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(define array (make-c-bytevector (* (c-size-of 'int) 3)))
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(pffi-pointer-set! array 'int (* (c-size-of 'int) 0) 3)
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(pffi-pointer-set! array 'int (* (c-size-of 'int) 1) 2)
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(pffi-pointer-set! array 'int (* (c-size-of 'int) 2) 1)
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(display array)
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(newline)
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;> (3 2 1)
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; Sort the array
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(qsort array 3 (c-size-of 'int) compare)
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(display array)
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(newline)
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;> (1 2 3)
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### c-bytevector
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(**make-c-null**)
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Returns a null C pointer.
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(**c-null?** _obj_)
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Returns **#t** if _obj_ is a null C pointer, otherwise returns **#f**.
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(**c-free** _c-bytevector_)
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Frees _c-bytevector_ from memory.
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(**make-c-bytevector** _k_)
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(**make-c-bytevector** _k_ _fill_)
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Returns a newly allocated c-bytevector of _k_ bytes.
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If the _fill_ argument is missing, the initial contents of the
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returned c-bytevector are unspecified.
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If the _fill_ argument is present, it's value must confine to C uint8_t values
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, it specifies the initial value for the bytes of the c-bytevector
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#### Accessors
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(**native-endianness**)
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c-bytevector-s8-set!
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c-bytevector-s8-ref
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c-bytevector-s16-set!
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c-bytevector-s16-ref
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c-bytevector-s16-native-set!
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c-bytevector-s16-native-ref
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c-bytevector-u16-set!
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c-bytevector-u16-ref
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c-bytevector-u16-native-set!
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c-bytevector-u16-native-ref
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c-bytevector-s32-set!
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c-bytevector-s32-ref
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c-bytevector-s32-native-set!
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c-bytevector-s32-native-ref
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c-bytevector-u32-set!
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c-bytevector-u32-ref
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c-bytevector-u32-native-set!
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c-bytevector-u32-native-ref
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c-bytevector-s64-set!
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c-bytevector-s64-ref
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c-bytevector-s64-native-set!
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c-bytevector-s64-native-ref
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c-bytevector-u64-set!
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c-bytevector-u64-ref
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c-bytevector-u64-native-set!
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c-bytevector-u64-native-ref
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c-bytevector-sint-set!
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c-bytevector-sint-ref
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c-bytevector-uint-set!
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c-bytevector-uint-ref
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c-bytevector-ieee-single-set!
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c-bytevector-ieee-single-native-set!
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c-bytevector-ieee-single-ref
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c-bytevector-ieee-single-native-ref
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c-bytevector-ieee-double-set!
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c-bytevector-ieee-double-native-set!
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c-bytevector-ieee-double-ref
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c-bytevector-ieee-double-native-ref
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bytevector->c-bytevector
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c-bytevector->bytevector
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call-with-address-of
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string->c-utf8
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c-utf8->string
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### Environment variables
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Setting environment variables like this on Windows works for this library:
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set "PFFI_LOAD_PATH=C:\Program Files (x86)/foo/bar"
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#### PFFI\_LOAD\_PATH
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To add more paths to where pffi looks for libraries set PFFI\_LOAD\_PATH to
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paths separated by ; on windows, and : on other operating systems.
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