601 lines
22 KiB
Markdown
601 lines
22 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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[Jenkins](https://jenkins.scheme.org/job/foreign_c/job/foreign-c/)
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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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- c-type-size
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- define-c-library
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- define-c-procedure
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- c-bytevector?
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- c-bytevector-u8-set!
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- c-bytevector-u8-ref
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- c-bytevector-pointer-set!
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- c-bytevector-pointer-ref
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- [Primitives 2](#primitives-2)
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- define-c-callback
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- [c-bytevector](#c-bytevector)
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- make-c-null
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- c-null?
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- c-free
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- make-c-bytevector
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- call-with-address-of
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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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- string-\>c-utf8
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- c-utf8-\>string
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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-type-size | 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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Eithe 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)
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or git clone, preferably with a tag, and copy the _foreign_ directory to your
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library 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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(define-c-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 (c-bytevector-sint-get pointer-a (native-endianness) 0))
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(b (c-bytevector-sint-get pointer-b (native-endianness) 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-type-size 'int) 3)))
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(c-bytevector-s32-native-set! array (* (c-type-size 'int) 0) 3)
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(c-bytevector-s32-native-set! array (* (c-type-size 'int) 1) 2)
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(c-bytevector-s32-native-set! array (* (c-type-size '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-type-size '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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Foreign-c c-bytevector interface is copied from R6RS bytevectors, with some
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added functionality for C null pointers and manual memory management.
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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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(**call-with-address-of** _c-bytevector_ _thunk_)
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Calls _thunk_ with address pointer of _c-bytevector_.
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Since the support for calling C functions taking pointer address arguments,
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ones prefixrd with & in C, varies, some additional ceremony is needed on
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the Scheme side.
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Example:
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Calling from C:
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//void func(int** i);
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func(&i);
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Calling from Scheme:
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(define cbv (make-bytevector (c-type-size 'int)))
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(call-with-address-of
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cbv
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(lambda (address)
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(func address)))
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; Use cbv here
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The passed c-bytevector, in example named cbv, should only be used **after**
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call to call-with-addres-of ends.
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(**bytevector->c-bytevector** _bytevector_)
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Returns a newly allocated c-bytevector of the bytes of _bytevector_.
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(**c-bytevector->bytevector**)
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Returns a newly allocated bytevector of the bytes of _c-bytevector_.
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(**native-endianness**)
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Returns the endianness symbol associated implementation’s preferred endianness
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(usually that of the underlying machine architecture). This may be any
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\<endianness symbol\>, including a symbol other than big and little.
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(**make-c-bytevector** _k_)</br>
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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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(**c-bytevector-s8-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-s8-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-char-set!** _c-bytevector_ _k_ _char_)
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If _k_ is not a valid index of c-bytevector the behaviour is undefined.
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Stores the _char_ in element _k_ of _c-bytevector_.
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(**c-bytevector-char-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 char at index _k_ of _c-bytevector_.
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(**c-bytevector-uchar-set!** _c-bytevector_ _k_ _char_)
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If _k_ is not a valid index of c-bytevector the behaviour is undefined.
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Stores the unsigned _char_ in element _k_ of _c-bytevector_.
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(**c-bytevector-uchar-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 unsigned char at index _k_ of _c-bytevector_.
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(**c-bytevector-uint-ref** _c-bytevector_ _k_ _endianness_ _size_)</br>
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(**c-bytevector-sint-ref** _c-bytevector_ _k_ _endianness_ _size_)</br>
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(**c-bytevector-uint-set!** _c-bytevector_ _k_ _n_ _endianness_ _size_)</br>
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(**c-bytevector-sint-set!** _c-bytevector_ _k_ _n_ _endianness_ _size_)
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Size must be a positive exact integer object. If _k_,...,_k_ + _size_ − 1 is
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not valid indices of c-bytevector the behavior is unspecified.
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The c-bytevector-uint-ref procedure retrieves the exact integer object
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corresponding to the unsigned representation of size _size_ and specified by
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_endianness_ at indices _k_,...,_k_ + _size_ − 1.
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The c-bytevector-sint-ref procedure retrieves the exact integer object
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corresponding to the two’s-complement representation of size _size_ and
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specified by _endianness_ at indices _k_,...,_k_ + _size_ − 1. For
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c-bytevector-uint-set!, _n_ must be an exact integer object in the interval
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{0,...,256^_size_ − 1}.
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The c-bytevector-uint-set! procedure stores the unsigned representation of
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size _size_ and specified by _endianness_ into c-bytevector at indices
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_k_,...,_k_ + size − 1.
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The . . . -set! procedures return unspecified values.
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Examples:
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(define cbv (make-c-bytevector (c-type-size 'int)))
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(c-bytevector-sint-set! cbv 0 100 (native-endianness) (c-type-size 'int))
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(c-bytevector-sint-ref cbv 0 (native-endianness) (c-type-size 'int))
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> 100
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(**c-bytevector-u16-ref** _c-bytevector_ _k_ _endianness_)</br>
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(**c-bytevector-s16-ref** _c-bytevector_ _k_ _endianness_)</br>
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(**c-bytevector-u16-native-ref** _c-bytevector_ _k_)</br>
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(**c-bytevector-s16-native-ref** _c-bytevector_ _k_)</br>
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(**c-bytevector-u16-set!** _c-bytevector_ _k_ _n_ _endianness_)</br>
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(**c-bytevector-s16-set!** _c-bytevector_ _k_ _n_ _endianness_)</br>
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(**c-bytevector-u16-native-set!** _c-bytevector_ _k_ _n_)</br>
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(**c-bytevector-s16-native-set!** _c-bytevector_ _k_ _n_)
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_K_ must be a valid index of _c-bytevector_ ; so must _k_ + 1. For
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c-bytevector-u16-set! and c-bytevector-u16-native-set!, _n_ must be an exact
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integer object in the interval {0,...,216 − 1}. For c-bytevector-s16-set! and
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c-bytevector-s16-native-set!, _n_ must be an exact integer object in the
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interval {−215,...,215 − 1}.
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These retrieve and set two-byte representations of numbers at indices _k_ and
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_k_ + 1, according to the endianness specified by _endianness_. The procedures
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with u16 in their names deal with the unsigned representation; those with s16
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in their names deal with the two’s-complement representation.
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The procedures with native in their names employ the native endianness, and
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work only at aligned indices: _k_ must be a multiple of 2.
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The ...-set! procedures return unspecified values.
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(**c-bytevector-u32-ref** _c-bytevector_ _k_ _endianness_)</br>
|
||
(**c-bytevector-s32-ref** _c-bytevector_ _k_ _endianness_)</br>
|
||
(**c-bytevector-u32-native-ref** _c-bytevector_ _k_)</br>
|
||
(**c-bytevector-s32-native-ref** _c-bytevector_ _k_)</br>
|
||
(**c-bytevector-u32-set!** _c-bytevector_ _k_ _n_ _endianness_)</br>
|
||
(**c-bytevector-s32-set!** _c-bytevector_ _k_ _n_ _endianness_)</br>
|
||
(**c-bytevector-u32-native-set!** _c-bytevector_ _k_ _n_)</br>
|
||
(**c-bytevector-s32-native-set!** _c-bytevector_ _k_ _n_)
|
||
|
||
_K_,...,_k_ + 3 must be valid indices of bytevector. For c-bytevector-u32-set!
|
||
and bytevector-u32-native-set!, _n_ must be an exact integer object in the
|
||
interval {0,...,232 − 1}. For bytevector-s32-set! and
|
||
bytevector-s32-native-set!, _n_ must be an exact integer object in the
|
||
interval {−231,...,232 − 1}.
|
||
|
||
These retrieve and set four-byte representations of numbers at indices
|
||
_k_,...,_k_ + 3, according to the endianness specified by _endianness_.
|
||
The procedures with u32 in their names deal with the unsigned representation;
|
||
those with s32 with the two’s-complement representation.
|
||
|
||
The procedures with native in their names employ the native endianness, and
|
||
work only at aligned indices: _k_ must be a multiple of 4.
|
||
|
||
The ...-set! procedures return unspecified values.
|
||
|
||
(**c-bytevector-u64-ref** _c-bytevector_ _k_ _endianness_)</br>
|
||
(**c-bytevector-s64-ref** _c-bytevector_ _k_ _endianness_)</br>
|
||
(**c-bytevector-u64-native-ref** _c-bytevector_ _k_)</br>
|
||
(**c-bytevector-s64-native-ref** _c-bytevector_ _k_)</br>
|
||
(**c-bytevector-u64-set!** _c-bytevector_ _k_ _n_ _endianness_)</br>
|
||
(**c-bytevector-s64-set!** _c-bytevector_ _k_ _n_ _endianness_)</br>
|
||
(**c-bytevector-u64-native-set!** _c-bytevector_ _k_ _n_)</br>
|
||
(**c-bytevector-s64-native-set!** _c-bytevector_ _k_ _n_)
|
||
|
||
_K_,...,_k_ + 7 must be valid indices of _c-bytevector_. For
|
||
c-bytevector-u64-set! and c-bytevector-u64-native-set!, _n_ must be an exact
|
||
integer object in the interval {0,...,264 − 1}. For c-bytevector-s64-set! and
|
||
c-bytevector-s64-native-set!, _n_ must be an exact integer object in the
|
||
interval {−263,...,264 − 1}.
|
||
|
||
These retrieve and set eight-byte representations of numbers at indices
|
||
_k_,...,_k_ + 7, according to the endianness specified by _endianness_. The
|
||
procedures with u64 in their names deal with the unsigned representation; those
|
||
with s64 with the two’s-complement representation.
|
||
|
||
The procedures with native in their names employ the native endianness, and
|
||
work only at aligned indices: _k_ must be a multiple of 8.
|
||
|
||
The ...-set! procedures return unspecified values.
|
||
|
||
(**c-bytevector-ieee-single-native-ref**)</br>
|
||
(**c-bytevector-ieee-single-ref**)</br>
|
||
|
||
_K_,...,_k_ + 3 must be valid indices of _c-bytevector_. For
|
||
c-bytevector-ieee-single-native-ref, _k_ must be a multiple of 4.
|
||
|
||
These procedures return the inexact real number object that best represents the
|
||
IEEE-754 single-precision number represented by the four bytes beginning at
|
||
index _k_.
|
||
|
||
(**c-bytevector-ieee-double-native-ref**)</br>
|
||
(**c-bytevector-ieee-double-ref**)
|
||
|
||
_K_,...,_k_ + 7 must be valid indices of _c-bytevector_. For
|
||
c-bytevector-ieee-double-native-ref, _k_ must be a multiple of 8.
|
||
|
||
These procedures return the inexact real number object that best represents the
|
||
IEEE-754 double-precision number represented by the eight bytes beginning at
|
||
index _k_.
|
||
|
||
(**c-bytevector-ieee-single-native-set!**)</br>
|
||
(**c-bytevector-ieee-single-set!**)
|
||
|
||
_K_,...,_k_ + 3 must be valid indices of _c-bytevector_. For
|
||
c-bytevector-ieee-single-native-set!, _k_ must be a multiple of 4.
|
||
|
||
These procedures store an IEEE-754 single-precision representation of x into
|
||
elements _k_ through _k_ + 3 of bytevector, and return unspecified values.
|
||
|
||
(**c-bytevector-ieee-double-native-set!**)</br>
|
||
(**c-bytevector-ieee-double-set!**)
|
||
|
||
_K_,...,_k_ + 7 must be valid indices of bytevector. For
|
||
c-bytevector-ieee-double-native-set!, _k_ must be a multiple of 8.
|
||
|
||
These procedures store an IEEE-754 double-precision representation of x into
|
||
elements _k_ through _k_ + 7 of bytevector, andreturn unspecified values.
|
||
|
||
|
||
(**string->c-utf8** _string_)
|
||
|
||
Returns a newly allocated (unless empty) c-bytevector that contains the
|
||
UTF-8 encoding of the given string.
|
||
|
||
(**c-utf8->string** _c-bytevector_)
|
||
|
||
Returns a newly allocated (unless empty) string whose character sequence is
|
||
encoded by the given c-bytevector.
|
||
|
||
### Environment variables
|
||
|
||
Setting environment variables like this on Windows works for this library:
|
||
|
||
set "FOREIGN_C_LOAD_PATH=C:\Program Files (x86)/foo/bar"
|
||
|
||
#### FOREIGN_C_\_LOAD\_PATH
|
||
|
||
To add more paths to where foreign c looks for libraries set
|
||
FOREIGN_C\_LOAD\_PATH to paths separated by ; on windows, and : on other
|
||
operating systems.
|
||
|