Added MemoryStack::asArena

Author: squid233

.github/workflows/javadoc.yml

@@ -0,0 +1,50 @@
+name: Javadoc
+
+on: [ release, workflow_dispatch ]
+
+# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# Allow only one concurrent deployment, skipping runs queued between the run in-progress and latest queued.
+# However, do NOT cancel in-progress runs as we want to allow these production deployments to complete.
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Setup Pages
+        uses: actions/configure-pages@v5
+      - name: Set up JDK
+        uses: actions/setup-java@v4
+        with:
+          java-version: |
+            22
+          distribution: 'temurin'
+      - name: Grant execute permission for gradlew
+        if: ${{ runner.os != 'Windows' }}
+        run: chmod +x gradlew
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@v3
+      - name: Execute Gradle build
+        run: ./gradlew javadoc
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: './build/docs/javadoc'
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4

README.md

@@ -41,6 +41,6 @@ Gradle:
 
 ```groovy
 dependencies {
-    implementation("io.github.over-run:memstack:0.2.0")
+    implementation("io.github.over-run:memstack:0.3.0")
 }
 ```

gradle.properties

@@ -12,7 +12,7 @@ projGroupId=io.github.over-run
 projArtifactId=memstack
 # The project name should only contain lowercase letters, numbers and hyphen.
 projName=memstack
-projVersion=0.2.0
+projVersion=0.3.0
 projDesc=Memory stack for FFM API
 # Uncomment them if you want to publish to maven repository.
 projUrl=https://github.com/Over-Run/memstack

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.10-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.10.1-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME

src/main/java/io/github/overrun/memstack/DefaultMemoryStack.java

@@ -1,5 +1,6 @@
 package io.github.overrun.memstack;
 
+import java.lang.foreign.Arena;
 import java.lang.foreign.MemorySegment;
 import java.util.Arrays;
 
@@ -12,7 +13,9 @@
 public class DefaultMemoryStack implements MemoryStack {
     private final MemorySegment segment;
     private long[] frames;
+    private Arena[] arenas;
     private long offset = 0L;
+    private Arena arena;
     private int frameIndex = 0;
 
     /**
@@ -24,6 +27,7 @@ public class DefaultMemoryStack implements MemoryStack {
     public DefaultMemoryStack(MemorySegment segment, int frameCount) {
         this.segment = segment;
         this.frames = new long[frameCount];
+        this.arenas = new Arena[frameCount];
     }
 
     private MemorySegment trySlice(long byteSize, long byteAlignment) {
@@ -49,8 +53,10 @@ public MemorySegment allocate(long byteSize, long byteAlignment) {
     public MemoryStack push() {
         if (frameIndex >= frames.length) {
             frames = Arrays.copyOf(frames, frames.length * 3 / 2);
+            arenas = Arrays.copyOf(arenas, arenas.length * 3 / 2);
         }
         frames[frameIndex] = offset;
+        arenas[frameIndex] = arena;
         frameIndex++;
         return this;
     }
@@ -62,6 +68,10 @@ public void pop() {
         }
         frameIndex--;
         offset = frames[frameIndex];
+        if (arena != null) {
+            arena.close();
+        }
+        arena = arenas[frameIndex];
     }
 
     @Override
@@ -88,4 +98,29 @@ public void setPointer(long pointer) {
     public MemorySegment segment() {
         return segment;
     }
+
+    @Override
+    public Arena asArena() {
+        if (arena == null) {
+            arena = new Arena() {
+                private final Arena arena = Arena.ofConfined();
+
+                @Override
+                public MemorySegment allocate(long byteSize, long byteAlignment) {
+                    return DefaultMemoryStack.this.allocate(byteSize, byteAlignment);
+                }
+
+                @Override
+                public MemorySegment.Scope scope() {
+                    return arena.scope();
+                }
+
+                @Override
+                public void close() {
+                    arena.close();
+                }
+            };
+        }
+        return arena;
+    }
 }

src/main/java/io/github/overrun/memstack/MemoryStack.java

@@ -3,6 +3,7 @@
 import java.lang.foreign.Arena;
 import java.lang.foreign.MemorySegment;
 import java.lang.foreign.SegmentAllocator;
+import java.util.function.Consumer;
 
 /**
  * <h2>Memory stack</h2>
@@ -17,6 +18,8 @@
  * The stack itself does not bind to any segment scope;
  * it just slices the backing segment.
  * <p>
+ * To re-associate a memory segment with the memory stack, use {@link #asArena()}.
+ * <p>
  * Memory stack is not thread-safe;
  * consider using the {@linkplain #ofLocal() local stacks} to manage with threads.
  * <h3>Push and pop</h3>
@@ -182,4 +185,14 @@ default void close() {
      * {@return the backing memory segment}
      */
     MemorySegment segment();
+
+    /**
+     * Wraps this memory stack into an arena for re-associating a memory segment with
+     * {@link MemorySegment#reinterpret(Arena, Consumer) MemorySegment::reinterpret}.
+     * <p>
+     * The obtained arena closes when this stack is popped.
+     *
+     * @return the arena that wraps this memory stack
+     */
+    Arena asArena();
 }

src/test/java/io/github/overrun/memstack/test/MemoryStackTest.java

@@ -4,10 +4,11 @@
 import io.github.overrun.memstack.StackConfigurations;
 import org.junit.jupiter.api.Test;
 
+import java.lang.foreign.Arena;
+import java.lang.foreign.MemorySegment;
 import java.lang.foreign.ValueLayout;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertThrowsExactly;
+import static org.junit.jupiter.api.Assertions.*;
 
 /**
  * @author squid233
@@ -108,4 +109,14 @@ void testOutOfMemory() {
         assertThrowsExactly(IndexOutOfBoundsException.class, () ->
             MemoryStack.of().allocate(StackConfigurations.STACK_SIZE.get() + 1));
     }
+
+    @Test
+    void testAsArena() {
+        MemorySegment segment;
+        try (MemoryStack stack = MemoryStack.pushLocal()) {
+            segment = stack.allocate(ValueLayout.JAVA_INT)
+                .reinterpret(stack.asArena(), System.out::println);
+        }
+        assertFalse(segment.scope().isAlive());
+    }
 }