Michael McGuinness
fee71e7740
Feature/postprocessing * tests * passtest * fixshorttests * mosttests * improvingbasedockerfile * testspeeds * testing * host * canparallel * clean * passfullsuite * singlepagemax * test * findfeatures * findstables * tbls * tablestoo * tablestoo * lateraltests * tableloc * cleanup * inlinetable * childids * cleanup * tests
104 lines
2.6 KiB
Markdown
104 lines
2.6 KiB
Markdown
# ffi
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[](https://pkg.go.dev/github.com/jupiterrider/ffi)
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A purego binding for libffi.
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## Purpose
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You can use [purego](https://github.com/ebitengine/purego) to call C code without cgo. ffi provides extra functionality (e.g. passing and returning structs by value).
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## Requirements
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### OS/Architecture
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- darwin/amd64
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- darwin/arm64
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- freebsd/amd64
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- freebsd/arm64
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- linux/amd64
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- linux/arm64
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- windows/amd64
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- windows/arm64
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### Software
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[libffi](https://github.com/libffi/libffi) is preinstalled on most distributions, because it also is a dependency of Python and Ruby. If not, you can install it explicitly:
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#### Arch Linux
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```sh
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sudo pacman -S libffi
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```
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#### Debian 12, Ubuntu 22.04, Ubuntu 24.04
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```sh
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sudo apt install libffi8
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```
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#### Debian 11, Ubuntu 20.04
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```sh
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sudo apt install libffi7
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```
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#### FreeBSD
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```sh
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pkg install libffi
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```
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Note: Use this `-gcflags="github.com/ebitengine/purego/internal/fakecgo=-std"` build flag when cross compiling or having CGO_ENABLED set to 0 (FreeBSD only).
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#### Windows
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You need a `libffi-8.dll` next to the executable/root folder of your project or inside C:\Windows\System32. If you don't want to build libffi from source, you can find this dll for example inside the [Windows embeddable package](https://www.python.org/downloads/windows/) of Python.
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#### macOS
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You can use [Homebrew](https://brew.sh/) to install libffi:
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```sh
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brew install libffi
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```
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Note: If dlopen can't find the libffi.8.dylib file, you can try setting this environment variable:
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```sh
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export DYLD_FALLBACK_LIBRARY_PATH=$DYLD_FALLBACK_LIBRARY_PATH:/opt/homebrew/opt/libffi/lib
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```
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## Examples
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In this example we use the puts function inside the standard C library to print "Hello World!" to the console:
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```c
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int puts(const char *s);
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```
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```golang
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package main
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import (
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"unsafe"
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"github.com/ebitengine/purego"
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"github.com/jupiterrider/ffi"
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"golang.org/x/sys/unix"
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)
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func main() {
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// open the C library
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libm, err := purego.Dlopen("libc.so.6", purego.RTLD_LAZY)
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if err != nil {
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panic(err)
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}
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// get the address of puts
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puts, err := purego.Dlsym(libm, "puts")
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if err != nil {
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panic(err)
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}
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// describe the function's signature
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var cif ffi.Cif
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if status := ffi.PrepCif(&cif, ffi.DefaultAbi, 1, &ffi.TypeSint32, &ffi.TypePointer); status != ffi.OK {
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panic(status)
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}
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// convert the go string into a pointer
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text, _ := unix.BytePtrFromString("Hello World!")
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// call the puts function
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var result ffi.Arg
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ffi.Call(&cif, puts, unsafe.Pointer(&result), unsafe.Pointer(&text))
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}
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```
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You can find more examples inside the [examples](examples) folder of this repository.
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