Example use of blocks

hs-bindgen/blocktest/c/Makefile

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+libblocktest: iterator.o
+	clang -Wall -shared -lBlocksRuntime -o libblocktest.so iterator.o
+
+iterator.o:
+	clang -Wall -std=c23 -fblocks -fPIC -c -o iterator.o iterator.c
+
+.PHONY: clean
+clean:
+	rm -f *.o *.so

hs-bindgen/blocktest/c/iterator.c

@@ -0,0 +1,64 @@
+#include "Block.h"
+
+#include "iterator.h"
+
+// Toggle
+
+Toggle makeToggle(bool start) {
+    __block int b = start;
+
+    return Block_copy( ^(void) {
+        bool ret = b;
+        b = !b;
+        return ret;
+    });
+}
+
+bool toggleNext(Toggle block) {
+    return block();
+}
+
+void releaseToggle(Toggle block) {
+    Block_release(block);
+}
+
+// Counter
+
+Counter makeCounter(int start, int increment) {
+	__block int i = start; // __block storage makes it assignable
+
+	return Block_copy( ^(void) {
+		int ret = i;
+		i += increment;
+		return ret;
+	});
+}
+
+int counterNext(Counter block) {
+    return block();
+}
+
+void releaseCounter(Counter block) {
+	Block_release(block);
+}
+
+// Variable increment
+
+VarCounter makeVarCounter(int start) {
+	__block int i = start; // __block storage makes it assignable
+
+	return Block_copy( ^(int increment) {
+		int ret = i;
+		i += increment;
+		return ret;
+	});
+}
+
+int varCounterNext(VarCounter block, int increment) {
+    return block(increment);
+}
+
+void releaseVarCounter(VarCounter block) {
+    Block_release(block);
+}
+

hs-bindgen/blocktest/c/iterator.h

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+// Toggle between true and false
+
+typedef bool (^Toggle)();
+Toggle makeToggle(bool start);
+bool toggleNext(Toggle block);
+void releaseToggle(Toggle block);
+
+// Simple counter, fixed increment
+
+typedef int(^Counter)();
+Counter makeCounter(int start, int increment);
+int counterNext(Counter block);
+void releaseCounter(Counter block);
+
+// Counter with variable increment
+
+typedef int(^VarCounter)(int increment);
+VarCounter makeVarCounter(int start);
+int varCounterNext(VarCounter block, int increment);
+void releaseVarCounter(VarCounter block);

hs-bindgen/blocktest/generate.sh

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+#!/bin/bash
+
+cabal run -- \
+  hs-bindgen-cli preprocess \
+   -I c \
+   -o hs/generated/Iterator.hs \
+   --module Iterator \
+   --standard c23 \
+   --enable-blocks \
+   iterator.h

hs-bindgen/blocktest/hs/LICENSE

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+Copyright (c) 2024-2025, Well-Typed LLP and Anduril Industries Inc. 
+
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of the copyright holder nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

hs-bindgen/blocktest/hs/app/Main.hs

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+module Main where
+
+import Control.Exception
+import Control.Monad
+
+import Iterator
+
+main :: IO ()
+main = do
+    bracket (makeToggle 0) releaseToggle $ \toggle ->
+      replicateM_ 5 $
+        print =<< toggleNext toggle
+
+    bracket (makeCounter 5 2) releaseCounter $ \counter ->
+      replicateM_ 5 $
+        print =<< counterNext counter
+
+    bracket (makeVarCounter 5) releaseVarCounter $ \varCounter ->
+      forM_ [0 .. 4] $ \i ->
+        print =<< varCounterNext varCounter i
+

hs-bindgen/blocktest/hs/blocktest.cabal

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+cabal-version: 3.0
+name:          blocktest
+version:       0.1.0
+license:       BSD-3-Clause
+license-file:  LICENSE
+author:        Edsko de Vries
+maintainer:    [email protected]
+build-type:    Simple
+
+common lang
+  build-depends:    base >= 4.17 && < 5
+  default-language: GHC2021
+  ghc-options:      -Wall
+
+executable blocktest
+  import:           lang
+  main-is:          Main.hs
+  hs-source-dirs:   app, generated
+  other-modules:    Iterator
+  extra-libraries:  blocktest
+  build-depends:    hs-bindgen-runtime
+  ghc-options:      -pgmc clang -optc -std=c23 -optc -fblocks
+                    -pgma clang
+

hs-bindgen/blocktest/hs/cabal.project

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+packages: ., ../../../hs-bindgen-runtime

hs-bindgen/blocktest/hs/generated/.gitignore

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+*.hs