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Support blocking blocks
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@liamappelbe
liamappelbe committed Jan 10, 2025
1 parent 5c311ca commit d42c833
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Showing 9 changed files with 913 additions and 1,090 deletions.
168 changes: 86 additions & 82 deletions pkgs/ffigen/lib/src/code_generator/objc_block.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,8 @@ class ObjCBlock extends BindingType {
final List<Parameter> params;
final bool returnsRetained;
late final ObjCBlockWrapperFuncs _blockWrappers;
late final _FnTypeHelper _typeHelper;
late final _FnTypeHelper _blockingTypeHelper;

factory ObjCBlock({
required Type returnType,
Expand Down Expand Up @@ -108,9 +110,10 @@ class ObjCBlock extends BindingType {

final voidPtr = PointerType(voidType);
final blockPtr = PointerType(objCBlockType);
final func = _FnHelper(w, returnType, params);

final blockingFunc = _FnHelper(w, returnType, [
_typeHelper = _FnTypeHelper(w, returnType, params);

_blockingTypeHelper = _FnTypeHelper(w, returnType, [
Parameter(type: voidPtr, name: 'waiter', objCConsumed: false),
...params,
]);
Expand Down Expand Up @@ -144,12 +147,9 @@ class ObjCBlock extends BindingType {
ObjCBuiltInFunctions.registerBlockClosure.gen(w);
final getBlockClosure = ObjCBuiltInFunctions.getBlockClosure.gen(w);
final releaseFn = ObjCBuiltInFunctions.objectRelease.gen(w);
final wrapBlockingBlockFn = ObjCBuiltInFunctions.wrapBlockingBlock.gen(w);
final pkgNewClosureBlock = ObjCBuiltInFunctions.newClosureBlock.gen(w);
final pkgNewBlockingBlock = ObjCBuiltInFunctions.newBlockingBlock.gen(w);
final signalWaiterFn = ObjCBuiltInFunctions.signalWaiter.gen(w);
final blockClosureDisposePort =
ObjCBuiltInFunctions.blockClosureDisposePort.gen(w);
final disposeObjCBlockWithClosure =
ObjCBuiltInFunctions.disposeObjCBlockWithClosure.gen(w);
final returnFfiDartType = returnType.getFfiDartType(w);
final voidPtrCType = voidPtr.getCType(w);
final int64Type = NativeType(SupportedNativeType.int64).getCType(w);
Expand All @@ -161,47 +161,46 @@ class ObjCBlock extends BindingType {
// Write the function pointer based trampoline function.
s.write('''
$returnFfiDartType $funcPtrTrampoline(
$blockCType block, int closureId, ${func.paramsFfiDartType}) =>
${w.ffiLibraryPrefix}.Pointer<${func.natFnFfiDartType}>.fromAddress(closureId)
.asFunction<${func.ffiDartType}>()(${func.paramsNameOnly});
$blockCType block, int closureId, ${_typeHelper.paramsFfiDartType}) =>
${w.ffiLibraryPrefix}.Pointer<${_typeHelper.natFnFfiDartType}>.fromAddress(closureId).asFunction<${_typeHelper.ffiDartType}>()(${_typeHelper.paramsNameOnly});
final $funcPtrCallable = ${w.ffiLibraryPrefix}.Pointer.fromFunction<
${func.trampCType}>($funcPtrTrampoline $exceptionalReturn);
${_typeHelper.trampCType}>($funcPtrTrampoline $exceptionalReturn);
''');

// Write the closure based trampoline function.
s.write('''
$returnFfiDartType $closureTrampoline(
$blockCType block, int closureId, ${func.paramsFfiDartType}) =>
($getBlockClosure(closureId) as ${func.ffiDartType})(${func.paramsNameOnly});
$blockCType block, int closureId, ${_typeHelper.paramsFfiDartType}) =>
($getBlockClosure(closureId) as ${_typeHelper.ffiDartType})(${_typeHelper.paramsNameOnly});
final $closureCallable = ${w.ffiLibraryPrefix}.Pointer.fromFunction<
${func.trampCType}>($closureTrampoline $exceptionalReturn);
${_typeHelper.trampCType}>($closureTrampoline $exceptionalReturn);
''');

if (hasListener) {
// Write the listener trampoline function.
s.write('''
$returnFfiDartType $listenerTrampoline(
$blockCType block, int closureId, ${func.paramsFfiDartType}) {
($getBlockClosure(closureId) as ${func.ffiDartType})(${func.paramsNameOnly});
$blockCType block, int closureId, ${_typeHelper.paramsFfiDartType}) {
($getBlockClosure(closureId) as ${_typeHelper.ffiDartType})(${_typeHelper.paramsNameOnly});
$releaseFn(block.cast());
}
${func.trampNatCallType} $listenerCallable = ${func.trampNatCallType}.listener(
$listenerTrampoline $exceptionalReturn)..keepIsolateAlive = false;
$returnFfiDartType $blockingTrampoline(
$blockCType block, int closureId, ${blockingFunc.paramsFfiDartType}) {
${_typeHelper.trampNatCallType} $listenerCallable = ${_typeHelper.trampNatCallType}.listener(
$listenerTrampoline $exceptionalReturn)..keepIsolateAlive = false;
$returnFfiDartType $blockingTrampoline($blockCType block, int closureId,
${_blockingTypeHelper.paramsFfiDartType}) {
try {
($getBlockClosure(closureId) as ${func.ffiDartType})(${func.paramsNameOnly});
($getBlockClosure(closureId) as ${_typeHelper.ffiDartType})(${_typeHelper.paramsNameOnly});
} catch (e) {
} finally {
$signalWaiterFn(waiter);
$releaseFn(block.cast());
}
}
${blockingFunc.trampNatCallType} $blockingCallable =
${blockingFunc.trampNatCallType}.isolateLocal(
${_blockingTypeHelper.trampNatCallType} $blockingCallable =
${_blockingTypeHelper.trampNatCallType}.isolateLocal(
$blockingTrampoline $exceptionalReturn)..keepIsolateAlive = false;
${blockingFunc.trampNatCallType} $blockingListenerCallable =
${blockingFunc.trampNatCallType}.listener(
${_blockingTypeHelper.trampNatCallType} $blockingListenerCallable =
${_blockingTypeHelper.trampNatCallType}.listener(
$blockingTrampoline $exceptionalReturn)..keepIsolateAlive = false;
''');
}
Expand All @@ -221,7 +220,7 @@ ${blockingFunc.trampNatCallType} $blockingListenerCallable =
objCRetain: true,
objCAutorelease: !returnsRetained,
);
final convFn = '(${func.paramsFfiDartType}) => $convFnInvocation';
final convFn = '(${_typeHelper.paramsFfiDartType}) => $convFnInvocation';

// Write the wrapper class.
s.write('''
Expand All @@ -238,7 +237,7 @@ abstract final class $name {
/// This block must be invoked by native code running on the same thread as
/// the isolate that registered it. Invoking the block on the wrong thread
/// will result in a crash.
// static $blockType fromFunctionPointer(${func.natFnPtrCType} ptr) =>
// static $blockType fromFunctionPointer(${_typeHelper.natFnPtrCType} ptr) =>
// $blockType($newPointerBlock($funcPtrCallable, ptr.cast()),
// retain: false, release: true);
Expand All @@ -247,18 +246,17 @@ abstract final class $name {
/// This block must be invoked by native code running on the same thread as
/// the isolate that registered it. Invoking the block on the wrong thread
/// will result in a crash.
static $blockType fromFunction(${func.dartType} fn) =>
$blockType($newClosureBlock(
$closureCallable, $registerBlockClosure($convFn),
$blockClosureDisposePort, $disposeObjCBlockWithClosure),
retain: false, release: true);
static $blockType fromFunction(${_typeHelper.dartType} fn) =>
$blockType($pkgNewClosureBlock(
$convFn, $closureCallable.cast(),
$newClosureBlock), retain: false, release: true);
''');

// Listener block constructor is only available for void blocks.
if (hasListener) {
// This snippet is the same as the convFn above, except that the params
// don't need to be retained because they've already been retained by
// _blockWrappers.listenerWrapper.
// _blockWrappers.newListenerBlock.
final listenerConvertedFnArgs = params
.map((p) =>
p.type.convertFfiDartTypeToDartType(w, p.name, objCRetain: false))
Expand All @@ -270,9 +268,9 @@ abstract final class $name {
objCAutorelease: !returnsRetained,
);
final listenerConvFn =
'(${func.paramsFfiDartType}) => $listenerConvFnInvocation';
final wrapListenerFn = _blockWrappers.listenerWrapper!.name;
final wrapBlockingFn = _blockWrappers.blockingWrapper!.name;
'(${_typeHelper.paramsFfiDartType}) => $listenerConvFnInvocation';
final newListenerBlock = _blockWrappers.newListenerBlock!.name;
final newBlockingBlock = _blockWrappers.newBlockingBlock!.name;

s.write('''
Expand All @@ -285,15 +283,10 @@ abstract final class $name {
///
/// Note that unlike the default behavior of NativeCallable.listener, listener
/// blocks do not keep the isolate alive.
static $blockType listener(${func.dartType} fn) {
final raw = $newClosureBlock(
$listenerCallable.nativeFunction.cast(),
$registerBlockClosure($listenerConvFn),
$blockClosureDisposePort, $disposeObjCBlockWithClosure);
final wrapper = $wrapListenerFn(raw);
$releaseFn(raw.cast());
return $blockType(wrapper, retain: false, release: true);
}
static $blockType listener(${_typeHelper.dartType} fn) =>
$blockType($pkgNewClosureBlock(
$listenerConvFn, $listenerCallable.nativeFunction.cast(),
$newListenerBlock), retain: false, release: true);
/// Creates a blocking block from a Dart function.
///
Expand All @@ -304,20 +297,11 @@ abstract final class $name {
/// This block does not keep the owner isolate alive. If the owner isolate has
/// shut down, and the block is invoked by native code, it may block
/// indefinitely, or have other undefined behavior.
static $blockType blocking(${func.dartType} fn) {
final raw = $newClosureBlock(
$blockingCallable.nativeFunction.cast(),
$registerBlockClosure($listenerConvFn),
$blockClosureDisposePort, $disposeObjCBlockWithClosure);
final rawListener = $newClosureBlock(
$blockingListenerCallable.nativeFunction.cast(),
$registerBlockClosure($listenerConvFn),
$blockClosureDisposePort, $disposeObjCBlockWithClosure);
final wrapper = $wrapBlockingBlockFn($wrapBlockingFn, raw, rawListener);
$releaseFn(raw.cast());
$releaseFn(rawListener.cast());
return $blockType(wrapper, retain: false, release: true);
}
static $blockType blocking(${_typeHelper.dartType} fn) =>
$blockType($pkgNewBlockingBlock(
$listenerConvFn, $blockingCallable.nativeFunction.cast(),
$blockingListenerCallable.nativeFunction.cast(),
$newBlockingBlock), retain: false, release: true);
''');
}
s.write('}\n\n');
Expand All @@ -339,7 +323,8 @@ abstract final class $name {
s.write('''
/// Call operator for `$blockType`.
extension $callExtension on $blockType {
${returnType.getDartType(w)} call(${func.paramsDartType}) => $callMethod;
${returnType.getDartType(w)} call(${_typeHelper.paramsDartType}) =>
$callMethod;
}
''');
Expand Down Expand Up @@ -382,7 +367,11 @@ extension $callExtension on $blockType {
final blockingName =
w.objCLevelUniqueNamer.makeUnique('_BlockingTrampoline');
final trampolineArg =
_blockWrappers.trampolineType.getNativeType(varName: 'trampoline');
_typeHelper.trampFnType.getNativeType(varName: 'trampoline');
final blockingTrampolineArg =
_blockingTypeHelper.trampFnType.getNativeType(varName: 'tramp');
final blockingListenerTrampolineArg = _blockingTypeHelper.trampFnType
.getNativeType(varName: 'listener_tramp');
final retainStr = returnsRetained ? 'NS_RETURNS_RETAINED' : '';
final dtorClass = '_${w.className}_BlockDestroyer';

Expand All @@ -400,10 +389,8 @@ __attribute__((visibility("default"))) __attribute__((used))
$blockTypeName $newClosureBlock(
$trampolineArg, int64_t closure_id, int64_t dispose_port,
void (*dtor)(int64_t, int64_t)) NS_RETURNS_RETAINED {
$dtorClass* obj = [[$dtorClass alloc] init];
obj.closure_id = closure_id;
obj.dispose_port = dispose_port;
obj.dtor = dtor;
$dtorClass* obj = [$dtorClass
new:closure_id disposePort:dispose_port destructor:dtor];
__weak __block $blockTypeName weakBlk;
$blockTypeName blk = ^$returnNativeType($argStr) {
return trampoline(weakBlk, ${['obj.closure_id', ...noRetains].join(', ')});
Expand All @@ -414,36 +401,51 @@ $blockTypeName $newClosureBlock(
''');

if (hasListener) {
final listenerWrapper = _blockWrappers.listenerWrapper!.name;
final blockingWrapper = _blockWrappers.blockingWrapper!.name;
final newListenerBlock = _blockWrappers.newListenerBlock!.name;
final newBlockingBlock = _blockWrappers.newBlockingBlock!.name;

s.write('''
__attribute__((visibility("default"))) __attribute__((used))
$blockTypeName $listenerWrapper($blockTypeName block) NS_RETURNS_RETAINED {
return ^void($argStr) {
${generateRetain('block')};
block(${retains.join(', ')});
$blockTypeName $newListenerBlock(
$trampolineArg, int64_t closure_id, int64_t dispose_port,
void (*dtor)(int64_t, int64_t)) NS_RETURNS_RETAINED {
$dtorClass* obj = [$dtorClass
new:closure_id disposePort:dispose_port destructor:dtor];
__weak __block $blockTypeName weakBlk;
$blockTypeName blk = ^$returnNativeType($argStr) {
${generateRetain('weakBlk')};
return trampoline(weakBlk, ${['obj.closure_id', ...retains].join(', ')});
};
weakBlk = blk;
return blk;
}
typedef $returnNativeType (^$blockingName)($blockingArgStr);
__attribute__((visibility("default"))) __attribute__((used))
$blockTypeName $blockingWrapper(
$blockingName block, $blockingName listenerBlock,
$blockTypeName $newBlockingBlock(
$blockingTrampolineArg, $blockingListenerTrampolineArg,
int64_t closure_id, int64_t dispose_port, void (*dtor)(int64_t, int64_t),
void* (*newWaiter)(), void (*awaitWaiter)(void*)) NS_RETURNS_RETAINED {
NSThread *targetThread = [NSThread currentThread];
return ^void($argStr) {
$dtorClass* obj = [$dtorClass
new:closure_id disposePort:dispose_port destructor:dtor];
__weak __block $blockTypeName weakBlk;
$blockTypeName blk = ^$returnNativeType($argStr) {
${generateRetain('weakBlk')};
if ([NSThread currentThread] == targetThread) {
${generateRetain('block')};
block(${blockingRetains.join(', ')});
tramp(weakBlk, ${['obj.closure_id', ...blockingRetains].join(', ')});
} else {
void* waiter = newWaiter();
${generateRetain('listenerBlock')};
listenerBlock(${blockingListenerRetains.join(', ')});
listener_tramp(weakBlk, ${[
'obj.closure_id',
...blockingListenerRetains
].join(', ')});
awaitWaiter(waiter);
}
};
weakBlk = blk;
return blk;
}
''');
}
Expand Down Expand Up @@ -523,8 +525,9 @@ $blockTypeName $blockingWrapper(
}
}

class _FnHelper {
class _FnTypeHelper {
late final NativeFunc natFnType;
late final FunctionType trampFnType;
late final String natFnFfiDartType;
late final String natFnPtrCType;
late final String dartType;
Expand All @@ -537,15 +540,15 @@ class _FnHelper {
late final String paramsFfiDartType;
late final String paramsDartType;

_FnHelper(Writer w, Type returnType, List<Parameter> params) {
_FnTypeHelper(Writer w, Type returnType, List<Parameter> params) {
final fnType = FunctionType(returnType: returnType, parameters: params);
natFnType = NativeFunc(fnType);
natFnFfiDartType = natFnType.getFfiDartType(w);
natFnPtrCType = PointerType(natFnType).getCType(w);
dartType = fnType.getDartType(w, writeArgumentNames: false);
ffiDartType = fnType.getFfiDartType(w, writeArgumentNames: false);

final trampFnType = FunctionType(
trampFnType = FunctionType(
returnType: returnType,
parameters: [
Parameter(
Expand All @@ -554,7 +557,8 @@ class _FnHelper {
objCConsumed: false),
Parameter(
type: NativeType(SupportedNativeType.int64),
name: 'closure_id', objCConsumed: false),
name: 'closure_id',
objCConsumed: false),
...params,
],
);
Expand Down
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