Binding generator for FFI bindings
Binding generator for FFI bindings.
Note: ffigen only supports parsing
C
headers.
Example
For some header file example.h:
int sum(int a, int b);
Add configurations to Pubspec File:
ffigen:
output: 'generated_bindings.dart'
headers:
entry-points:
- 'example.h'
Output (generated_bindings.dart).
class NativeLibrary {
final Pointer<T> Function<T extends NativeType>(String symbolName)
_lookup;
NativeLibrary(DynamicLibrary dynamicLibrary)
: _lookup = dynamicLibrary.lookup;
NativeLibrary.fromLookup(
Pointer<T> Function<T extends NativeType>(String symbolName)
lookup)
: _lookup = lookup;
int sum(int a, int b) {
return _sum(a, b);
}
late final _sumPtr = _lookup<ffi.NativeFunction<ffi.Int32 Function(ffi.Int32, ffi.Int32)>>('sum');
late final _sum = _sum_ptr.asFunction<int Function(int, int)>();
}
Using this package
- Add
ffigen
underdev_dependencies
in yourpubspec.yaml
. - Install LLVM (see Installing LLVM).
- Configurations must be provided in
pubspec.yaml
or in a custom YAML file (see configurations). - Run the tool-
dart run ffigen
.
Jump to FAQ.
Installing LLVM
package:ffigen
uses LLVM. Install LLVM (9+) in the following way.
ubuntu/linux
- Install libclangdev –
sudo apt-get install libclang-dev
.
Windows
- Install Visual Studio with C++ development support.
- Install LLVM or
winget install -e --id LLVM.LLVM
.
MacOS
- Install Xcode.
- Install LLVM –
brew install llvm
.
Configurations
Configurations can be provided in 2 ways-
- In the project’s
pubspec.yaml
file under the keyffigen
. - Via a custom YAML file, then specify this file while running –
dart run ffigen --config config.yaml
The following configuration options are available-
Key | Explaination | Example |
---|---|---|
output (Required) |
Output path of the generated bindings. |
output: 'generated_bindings.dart'
|
llvm-path | Path to llvm folder. ffigen will sequentially search for `lib/libclang.so` on linux, `lib/libclang.dylib` on macOs and `bin\libclang.dll` on windows, in the specified paths. Complete path to the dynamic library can also be supplied. |
llvm-path:
- '/usr/local/opt/llvm'
- 'C:\Program Files\llvm`
- '/usr/lib/llvm-11'
# Specify exact path to dylib
- '/usr/lib64/libclang.so'
|
headers (Required) |
The header entry-points and include-directives. Glob syntax is allowed. If include-directives are not specified ffigen will generate everything directly/transitively under the entry-points. |
headers:
entry-points:
- 'folder/**.h'
- 'folder/specific_header.h'
include-directives:
- '**index.h'
- '**/clang-c/**'
- '/full/path/to/a/header.h'
|
name (Prefer) |
Name of generated class. |
name: 'SQLite'
|
description (Prefer) |
Dart Doc for generated class. |
description: 'Bindings to SQLite'
|
compiler-opts | Pass compiler options to clang. You can also pass these via the command line tool. |
compiler-opts:
- '-I/usr/lib/llvm-9/include/'
and/or via the command line – dart run ffigen --compiler-opts "-I/headers
-L 'path/to/folder name/file'"
|
compiler-opts-automatic -> macos -> include-c-standard-library | Tries to automatically find and add C standard library path to compiler-opts on macos. Default: true |
compiler-opts-automatic:
macos:
include-c-standard-library: false
|
functions
structs unions enums unnamed-enums macros globals |
Filters for declarations. Default: all are included. Options – |
functions:
include: # 'exclude' is also available.
# Matches using regexp.
- [a-z][a-zA-Z0-9]*
# '.' matches any character.
- prefix.*
# Matches with exact name
- someFuncName
# Full names have higher priority.
- anotherName
rename:
# Regexp groups based replacement.
'clang_(.*)': '$1'
'clang_dispose': 'dispose'
# Removes '_' from beginning.
'_(.*)': '$1'
symbol-address:
# Used to expose symbol address.
include:
- myFunc
structs:
rename:
# Removes prefix underscores
# from all structures.
'_(.*)': '$1'
member-rename:
'.*': # Matches any struct.
# Removes prefix underscores
# from members.
'_(.*)': '$1'
enums:
rename:
# Regexp groups based replacement.
'CXType_(.*)': '$1'
member-rename:
'(.*)': # Matches any enum.
# Removes '_' from beginning
# enum member name.
'_(.*)': '$1'
# Full names have higher priority.
'CXTypeKind':
# $1 keeps only the 1st
# group i.e only '(.*)'.
'CXType(.*)': '$1'
globals:
exclude:
- aGlobal
rename:
# Removes '_' from
# beginning of a name.
'_(.*)': '$1'
|
typedefs | Filters for referred typedefs.
Options – Note: Typedefs that are not referred to anywhere will not be generated. |
typedefs:
exclude:
# Typedefs starting with `p` are not generated.
- 'p.*'
rename:
# Removes '_' from beginning of a typedef.
'_(.*)': '$1'
|
functions -> expose-typedefs | Generate the typedefs to Native and Dart type of a function Default: Inline types are used and no typedefs to Native/Dart type are generated. |
functions:
expose-typedefs:
include:
# Match function name.
- 'myFunc'
# Do this to expose types for all function.
- '.*'
exclude:
# If you only use exclude, then everything
# not excluded is generated.
- 'dispose'
|
structs -> pack | Override the @Packed(X) annotation for generated structs.
Options – none, 1, 2, 4, 8, 16 Note: Ffigen can only reliably identify packing specified using |
structs:
pack:
# Matches with the generated name.
'NoPackStruct': none # No packing
'.*': 1 # Pack all structs with value 1
|
comments | Extract documentation comments for declarations. The style and length of the comments recognized can be specified with the following options- style: doxygen(default) | any length: brief | full(default) If you want to disable all comments you can also pass comments: false. |
comments:
style: any
length: full
|
structs -> dependency-only
unions -> dependency-only |
If `opaque`, generates empty `Opaque` structs/unions if they were not included in config (but were added since they are a dependency) and only passed by reference(pointer). Options – full(default) | opaque |
structs:
dependency-only: opaque
unions:
dependency-only: opaque
|
sort | Sort the bindings according to name. Default: false, i.e keep the order as in the source files. |
sort: true
|
use-supported-typedefs | Should automatically map typedefs, E.g uint8_t => Uint8, int16_t => Int16 etc. Default: true |
use-supported-typedefs: true
|
dart-bool | Should generate dart `bool` instead of Uint8 for c99 bool in functions. Default: true |
dart-bool: true
|
use-dart-handle | Should map `Dart_Handle` to `Handle`. Default: true |
use-dart-handle: true
|
preamble | Raw header of the file, pasted as-it-is. |
preamble: |
// ignore_for_file: camel_case_types, non_constant_identifier_names
|
typedef-map | Map typedefs to Native Types. Values can only be Void, Uint8, Int8, Uint16, Int16, Uint32, Int32, Uint64, Int64, IntPtr, Float and Double. |
typedef-map:
'my_custom_type': 'IntPtr'
'size_t': 'Int64'
|
size-map | Size of integers to use (in bytes). The defaults (see example) may not be portable on all OS. Do not change these unless absolutely sure. |
# These are optional and also default,
# Omitting any and the default
# will be used.
size-map:
char: 1
unsigned char: 1
short: 2
unsigned short: 2
int: 4
unsigned int: 4
long: 8
unsigned long: 8
long long: 8
unsigned long long: 8
enum: 4
|
Limitations
- Multi OS support for types such as long. Issue #7
Trying out examples
cd examples/<example_u_want_to_run>
, Rundart pub get
.- Run
dart run ffigen
.
Running Tests
- Dynamic library for some tests need to be built before running the examples.
cd test/native_test
.- Run
dart build_test_dylib.dart
.
Run tests from the root of the package with dart run test
.
Note: If llvm is not installed in one of the default locations, tests may fail.
FAQ
Can ffigen be used for removing underscores or renaming declarations?
Ffigen supports regexp based renaming, the regexp must be a
full match, for renaming you can use regexp groups ($1
means group 1).
E.g – For renaming clang_dispose_string
to string_dispose
.
We can can match it using clang_(.*)_(.*)
and rename with $2_$1
.
Here’s an example of how to remove prefix underscores from any struct and its members.
structs:
...
rename:
'_(.*)': '$1' # Removes prefix underscores from all structures.
member-rename:
'.*': # Matches any struct.
'_(.*)': '$1' # Removes prefix underscores from members.
How to generate declarations only from particular headers?
The default behaviour is to include everything directly/transitively under
each of the entry-points
specified.
If you only want to have declarations directly particular header you can do so
using include-directives
. You can use glob matching to match header paths.
headers:
entry-points:
- 'path/to/my_header.h'
include-directives:
- '**my_header.h' # This glob pattern matches the header path.
Can ffigen filter declarations by name?
Ffigen supports including/excluding declarations using full regexp matching.
Here’s an example to filter functions using names
functions:
include:
- 'clang.*' # Include all functions starting with clang.
exclude:
- '.*dispose': # Exclude all functions ending with dispose.
This will include clang_help
. But will exclude clang_dispose
.
Note: exclude overrides include.
How does ffigen handle C Strings?
Ffigen treats char*
just as any other pointer,(Pointer<Int8>
).
To convert these to/from String
, you can use package:ffi. Use ptr.cast<Utf8>().toDartString()
to convert char*
to dart string
and "str".toNativeUtf8()
to convert string
to char*
.
How does ffigen handle C99 bool data type?
Although dart:ffi
doesn’t have a NativeType for bool
, they can be implemented as Uint8
.
Ffigen generates dart bool
for function parameters and return type by default.
To disable this, and use int
instead, set dart-bool: false
in configurations.
How are unnamed enums handled?
Unnamed enums are handled separately, under the key unnamed-enums
, and are generated as top level constants.
Here’s an example that shows how to include/exclude/rename unnamed enums
unnamed-enums:
include:
- 'CX_.*'
exclude:
- '.*Flag'
rename:
'CXType_(.*)': '$1'
Why are some struct/union declarations generated even after excluded them in config?
This happens when an excluded struct/union is a dependency to some included declaration.
(A dependency means a struct is being passed/returned by a function or is member of another struct in some way)
Note: If you supply structs
-> dependency-only
as opaque
ffigen will generate
these struct dependencies as Opaque
if they were only passed by reference(pointer).
structs:
dependency-only: opaque
unions:
dependency-only: opaque
How to expose the native pointers?
By default the native pointers are private, but you can use the
symbol-address
subkey for functions/globals and make them public by matching with its name. The pointers are then accesible via nativeLibrary.addresses
.
Example –
functions:
symbol-address:
include:
- 'myFunc' # Match function name.
- '.*' # Do this to expose all function pointers.
exclude: # If you only use exclude, then everything not excluded is generated.
- 'dispose'
How to get typedefs to Native and Dart type of a function?
By default these types are inline. But you can use the expose-typedef
subkey
for functions to generate them. This will expose the Native and Dart type.
E.g – for a function named hello
, the generated typedefs are named
as NativeHello
and DartHello
.
Example –
functions:
expose-typedefs:
include:
- 'myFunc' # Match function name.
- '.*' # Do this to expose types for all function.
exclude: # If you only use exclude, then everything not excluded is generated.
- 'dispose'
How are Structs/Unions/Enums that are reffered to via typedefs handled?
Named declarations use their own names even when inside another typedef.
However, unnamed declarations inside typedefs take the name of the first typedef
that refers to them.
Why are some typedefs not generated?
The following typedefs are not generated –
- They are not referred to anywhere in the included declarations.
- They refer to a struct/union having the same name as itself.
- They refer to a boolean, enum, inline array, Handle or any unsupported type.