467 lines
21 KiB
Markdown
467 lines
21 KiB
Markdown
---
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title: Portable Foreign Function Interface for R7RS Documentation
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version: 0.6.0
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---
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# Portable Foreign Function Interface for R7RS
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Portable foreign function interface for R7RS. It is portable in the sense that
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it supports multiple implementations, as opposed to being portable by
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conforming to some specification.
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[Project](https://todo.sr.ht/~retropikzel/r7rs-pffi)
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[Issue trackers](https://sr.ht/~retropikzel/r7rs-pffi/trackers)
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[Maling lists](https://sr.ht/~retropikzel/r7rs-pffi/lists)
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[Jenkins](https://jenkins.scheme.org/job/r7rs_pffi/job/r7rs-pffi/)
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## Table of contents
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<nav>
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- [Goals](#goals)
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- [Non Goals](#non-goals)
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- [Status](#status)
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- [Current caveats](#current-caveats)
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- [Roadmap](#roadmap)
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- [Implementation table](#implementation-table)
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- [Beta](#beta)
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- [Alpha](#alpha)
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- [Not started](#not-started)
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- [Other](#other)
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- [Documentation](#documentation)
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- [Usage](#usage)
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- [Chibi](#usage-chibi)
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- [Chicken](#usage-chicken)
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- [Racket](#usage-racket)
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- [Kawa](#usage-kawa)
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- [Reference](#reference)
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- [Types](#types)
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- [Procedures and macros](#procedures-and-macros)
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- [pffi-init](#pffi-init)
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- [pffi-size-of](#pffi-size-of)
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- [pffi-align-of](#pffi-align-of)
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- [pffi-load](#pffi-load)
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- [pffi-pointer-null](#pffi-pointer-null)
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- [pffi-pointer-null?](#pffi-pointer-null?)
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- [pffi-pointer-allocate](#pffi-pointer-allocate)
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- [pffi-pointer-address](#pffi-pointer-address)
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- [pffi-pointer?](#pffi-pointer?)
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- [pffi-pointer-free](#pffi-pointer-free)
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- [pffi-pointer-set!](#pffi-pointer-set!)
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- [pffi-pointer-get](#pffi-pointer-get)
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- [pffi-string->pointer](#pffi-string-to-pointer)
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- [pffi-pointer->string](#pffi-pointer-to-string)
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- [pffi-struct-make](#pffi-struct-make)
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- [pffi-struct-pointer](#pffi-struct-pointer)
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- [pffi-struct-offset-get](#pffi-struct-offset-get)
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- [pffi-struct-get](#pffi-struct-get)
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- [pffi-struct-set!](#pffi-struct-set!)
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- [pffi-define](#pffi-define)
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- [pffi-define-callback](#pffi-define-callback)
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</nav>
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<main>
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## Goals
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<a name="goals"></a>
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- Support only R7RS implementations
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- Same interface on all implementations
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- Some things that are procedures on one implementation are macros on other,
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but they must behave the same
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- Stability and being boring after 1.0.0 is reached
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## Non goals
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<a name="non-goals"></a>
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- To have every possible FFI feature
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- Compiling of used library C code at any point
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- That is no stubs, no C code generated by the library and so on
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- The pffi library itself may require compilation on installation
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## Status
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<a name="status"></a>
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Currently the interface of the library is in okay shape. It propably will not change much but no
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guarantees are being made just yet.
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Due to supporting many different Scheme implementations, different parts of this software are in
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different stage. As a whole it is still in **alpha** stage. That said the interface should not be
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changing anymore and some implementations are in **beta**.
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### Current caveats
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<a name="current-caveats"></a>
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- No way to pass structs by value
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- Most implementations are missing callback support
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## Roadmap
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For roadmap to 1.0.0 see [issues](https://todo.sr.ht/~retropikzel/r7rs-pffi?search=status%3Aopen%20label%3A%221.0.0%22)
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## Implementation table
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<a name="implementation-table"></a>
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### Released
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<a name="released"></a>
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### Beta
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<a name="beta"></a>
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| | pffi-init | pffi-size-of | pffi-load | pffi-pointer-null | pffi-pointer-null? | pffi-pointer-allocate | pffi-pointer-address | pffi-pointer? | pffi-pointer-free | pffi-pointer-set! | pffi-pointer-get | pffi-string->pointer | pffi-pointer->string | pffi-struct-make | pffi-struct-pointer | pffi-struct-offset-get | pffi-struct-get | pffi-struct-set! | pffi-define | pffi-define-callback |
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|--------------|:---------:|:------------:|:---------:|:-----------------:|:------------------:|:---------------------:|:--------------------:|:-------------:|:-----------------:|:-----------------:|:----------------:|:--------------------:|:--------------------:|:----------------:|:-------------------:|:----------------------:|:---------------:|:----------------:|:-----------:|:--------------------:|
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| Chibi | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | |
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| Chicken-5 | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X |
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| Gauche | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | |
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| Guile | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X |
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| Kawa | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X |
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| Racket | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X |
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| Saggittarius | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X |
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### Alpha
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<a name="alpha"></a>
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| | pffi-init | pffi-size-of | pffi-load | pffi-pointer-null | pffi-pointer-null? | pffi-pointer-allocate | pffi-pointer-address | pffi-pointer? | pffi-pointer-free | pffi-pointer-set! | pffi-pointer-get | pffi-string->pointer | pffi-pointer->string | pffi-struct-make | pffi-struct-pointer | pffi-struct-offset-get | pffi-struct-get | pffi-struct-set! | pffi-define | pffi-define-callback |
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|--------------|:---------:|:------------:|:---------:|:-----------------:|:------------------:|:---------------------:|:--------------------:|:-------------:|:-----------------:|:-----------------:|:----------------:|:--------------------:|:--------------------:|:----------------:|:-------------------:|:----------------------:|:---------------:|:----------------:|:-----------:|:--------------------:|
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| Cyclone | X | X | X | X | X | X | | X | X | X | X | X | X | X | X | X | X | X | X | |
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| Gambit | X | X | | | | | X | | | | | | | X | X | X | X | X | | |
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| Gerbil | X | | | | | | | | | | | | | X | X | X | X | X | | |
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| Larceny | X | | | | | | | | | | | | | X | X | X | X | X | | |
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| Mosh | X | X | X | X | X | X | | X | X | X | X | X | X | X | X | X | X | X | X | X |
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| Skint | X | | | | | | | | | | | | | X | X | X | X | X | | |
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| Stklos | X | X | X | X | X | X | | X | X | | | | | X | X | X | X | X | | |
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| tr7 | | | | | | | | | | | | | | X | X | X | X | X | | |
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| Ypsilon | | | | | | | | | | | | | | X | X | X | X | X | | |
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### Not started
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<a name="not-started"></a>
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- [LIPS](https://lips.js.org/)
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- Will work on nodejs by using some C FFI library from npm
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- Javascript side needs design
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- [Biwascheme](https://www.biwascheme.org/)
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- Will work on nodejs by using some C FFI library from npm
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- Javascript side needs design
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- [MIT-Scheme](https://www.gnu.org/software/mit-scheme/)
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- Need to study the implementation more
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- [Airship](https://gitlab.com/mbabich/airship-scheme)
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- Need to study the implementation more
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- [Other gambit targets](https://gambitscheme.org/)
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- Gambit compiles to different targets other than C too, for example Javascript. It would be cool
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and interesting to see if this FFI could also support some of those
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- When LIPS and Biwascheme Javascript side is done then Gambit should be done too
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- [s48-r7rs](https://codeberg.org/prescheme/s48-r7rs)
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- Need to study the implementation more
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- [prescheme](https://codeberg.org/prescheme/prescheme)
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- Need to study the implementation more
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### Other
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<a name="other"></a>
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- [s7](https://scheme.fail://ccrma.stanford.edu/software/snd/snd/s7.html)
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- Propably does not need FFI as it is embeddable only
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- [Loko](https://scheme.fail/)
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- Desires no C interop, I can respect that
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## Documentation
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<a name="documentation"></a>
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### Usage
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<a name="usage"></a>
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#### Chibi
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<a name="usage-chibi"></a>
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Needs libffi-dev, on Debina/Ubuntu/Mint install with:
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apt install libffi-dev
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Build with:
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make chibi
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#### Chicken
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<a name="usage-chicken"></a>
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Needs [r7rs egg](https://wiki.call-cc.org/eggref/5/r7rs), install with:
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chicken-install r7rs
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#### Racket
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<a name="usage-racket"></a>
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Needs [racket-r7rs](https://github.com/lexi-lambda/racket-r7rs), install with:
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raco pkg install --auto r7rs
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#### Kawa
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<a name="usage-kawa"></a>
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Kawa Needs at least Java version 22
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Needs jvm flags:
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- \--add-exports java.base/jdk.internal.foreign.abi=ALL-UNNAMED
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- \--add-exports java.base/jdk.internal.foreign.layout=ALL-UNNAMED
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- \--add-exports java.base/jdk.internal.foreign=ALL-UNNAMED
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- \--enable-native-access=ALL-UNNAMED
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## Reference
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<a name="reference"></a>
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### Types
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<a name="types"></a>
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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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- callback
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- Callback function
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### Procedures and macros
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<a name="procedures-and-macros"></a>
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Some of these are procedures and some macros, it might also change implementation to implementation.
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#### pffi-init <a name="pffi-init"></a>
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**pffi-init**
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Always call this first, on most implementation it does nothing but some implementations might need
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initialisation run.
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#### pffi-size-of <a name="pffi-size-of"></a>
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**pffi-size-of** object -> number
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Returns the size of the pffi-struct, pffi-enum or pffi-type.
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#### pffi-align-of <a name="pffi-align-of"></a>
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**pffi-align-of** type -> number
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Returns the align of the type.
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#### pffi-load <a name="pffi-load"></a>
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**pffi-load** headers shared-object-name [options] -> object
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Load given shared object automatically searching many predefined paths.
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Takes as argument a list of C headers, these are for the compiler ones. And an shared-object name,
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used by the dynamic FFI's. The name of the shared object should not contain suffix like .so or
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.dll. Nor should it contain any prefix like "lib".
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Additional options argument can be provided, theys should be a pair with a
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keyword. The options are:
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- additional-versions
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- Search for additional versions of shared object, given shared object "c" and additional
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versions "6" "7" on linux the files "libc", "libc.6", "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 for
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Example:
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(define libc-stdlib
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(cond-expand
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(windows (pffi-load (list "stdlib.h") "ucrtbase"))
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(else (pffi-load (list "stdlib.h")
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"c"
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'(additional-versions . ("6"))
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'(additional-search-paths . ("."))))))
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#### pffi-pointer-null <a name="pffi-pointer-null"></a>
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**pffi-pointer-null** -> pointer
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Returns a new NULL pointer.
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#### pffi-pointer-null? <a name="pffi-pointer-null?"></a>
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**pffi-pointer-null?** pointer -> boolean
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Returns #t if given pointer is null pointer, #f otherwise.
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#### pffi-pointer-allocate <a name="pffi-pointer-allocate"></a>
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**pffi-pointer-allocate** size -> pointer
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Returns newly allocated pointer of given size.
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#### pffi-pointer-address <a name="pffi-pointer-address"></a>
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**pffi-pointer-address** pointer -> number
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Returns the address of given pointer as number.
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#### pffi-pointer? <a name="pffi-pointer?"></a>
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**pffi-pointer?** object -> boolean
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Returns #t if given object is pointer, #f otherwise.
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#### pffi-pointer-free <a name="pffi-pointer-free"></a>
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**pffi-pointer-free** pointer
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Frees given pointer.
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#### pffi-pointer-set! <a name="pffi-pointer-set!"></a>
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**pffi-pointer-set!** pointer type offset value
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Sets the value on a pointer on given offset. For example:
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(define p (pffi-pointer-allocate 128))
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(pffi-pointer-set! p 'int 64 100)
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Would set the offset of 64, on pointer p to value 100.
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#### pffi-pointer-get <a name="pffi-pointer-get"></a>
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**pffi-pointer-get** pointer type offset -> object
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Gets the value from a pointer on given offset. For example:
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(define p (pffi-pointer-allocate 128))
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(pffi-pointer-set! p 'int 64 100)
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(pffi-pointer-get p 'int 64)
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> 100
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#### pffi-string->pointer <a name="pffi-string-to-pointer"></a>
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**pffi-string->pointer** string -> pointer
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Makes pointer out of a given string.
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#### pffi-pointer->string <a name="pffi-pointer-to-string"></a>
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**pffi-pointer->string** pointer -> string
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Makes string out of a given pointer.
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#### pffi-struct-make <a name="pffi-struct-make"></a>
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**pffi-struct-make** c-type members . pointer -> pffi-struct
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Creates a new pffi-struct and allocates pointer for it. The members argument is a list of member
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names and types. For example:
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(define color (pffi-struct-make 'color '((int8 . r) (int8 . g) (int8 . b) (int8 .a ))))
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(define test (pffi-struct-make "struct test" '((int8 . r) (int8 . g) (int8 . b) (int8 .a ))))
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C-type argument can be symbol or a string.
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#### pffi-struct-pointer <a name="pffi-struct-pointer"></a>
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**pffi-struct-pointer** pffi-struct -> pointer
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Returns the pointer that holds the struct content. You need to use this when passing a struct as
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a pointer to foreign functions.
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(define s (pffi-struct-make 'test '((int . r) (int . g) (int . b))))
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(pffi-struct-pointer s)
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#### pffi-struct-offset-get <a name="pffi-struct-offset-get"></a>
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**pffi-struct-offset-get** member-name -> number
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Returns the offset of a struct member with given name.
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#### pffi-struct-get <a name="pffi-struct-get"></a>
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**pffi-struct-get** pffi-struct member-name -> object
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Returns the value of the givens struct member.
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#### pffi-struct-set! <a name="pffi-struct-set!"></a>
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**pffi-struct-set!** pffi-struct member-name value
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Sets the value of the givens struct member. It is up to you to make sure that the type of value is
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correct.
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#### pffi-define <a name="pffi-define"></a>
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**pffi-define** scheme-name shared-object c-name return-type argument-types
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Defines a new foreign function to be used from Scheme code. For example:
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(define libc-stdlib
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(cond-expand
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(windows (pffi-load (list "stdlib.h") (list) "ucrtbase" (list "")))
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(else (pffi-load (list "stdlib.h") (list) "c" (list "" "6")))))
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(pffi-define c-puts libc-stdlib 'puts 'int (list 'pointer))
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(c-puts "Message brought to you by FFI!")
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#### pffi-define-callback <a name="pffi-define-callback"></a>
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**pffi-define-callback** scheme-name return-type argument-types procedure
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Defines a new Sceme function to be used as callback to C code. For example:
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; Load the shared library
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(define libc-stdlib
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(cond-expand
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(windows (pffi-load (list "stdlib.h") (list) "ucrtbase" (list "")))
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(else (pffi-load (list "stdlib.h") (list) "c" (list "" "6")))))
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; Define C function that takes a callback
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(pffi-define qsort libc-stdlib 'qsort 'void (list '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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(list '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 (pffi-pointer-allocate (* (pffi-size-of 'int) 3)))
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(pffi-pointer-set! array 'int (* (pffi-size-of 'int) 0) 3)
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(pffi-pointer-set! array 'int (* (pffi-size-of 'int) 1) 2)
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(pffi-pointer-set! array 'int (* (pffi-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 (pffi-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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</main>
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