Linux ARM64: fix incompatibility with epoll

Author: manuelbl

java-does-usb/jextract/linux/gen_linux.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-JEXTRACT=../../../../jextract/bin/jextract
+JEXTRACT=../../../../jextract/build/jextract/bin/jextract
 
 rm -rf ../../src/main/java/net/codecrete/usb/linux/gen
 
@@ -89,8 +89,6 @@ $JEXTRACT --output ../../src/main/java \
 $JEXTRACT --output ../../src/main/java \
   --header-class-name epoll \
   --target-package net.codecrete.usb.linux.gen.epoll \
-  --include-struct epoll_event \
-  --include-union epoll_data \
   --include-constant EPOLL_CTL_ADD \
   --include-constant EPOLL_CTL_DEL \
   --include-constant EPOLLIN \

java-does-usb/src/main/java/net/codecrete/usb/linux/EPoll.java

@@ -7,29 +7,54 @@
 
 package net.codecrete.usb.linux;
 
-import net.codecrete.usb.linux.gen.epoll.epoll_event;
 import net.codecrete.usb.linux.gen.errno.errno;
 
 import java.lang.foreign.Arena;
 import java.lang.foreign.FunctionDescriptor;
+import java.lang.foreign.GroupLayout;
 import java.lang.foreign.Linker;
 import java.lang.foreign.MemoryLayout;
 import java.lang.foreign.MemorySegment;
 import java.lang.foreign.SequenceLayout;
+import java.lang.foreign.MemoryLayout.PathElement;
+import java.lang.foreign.ValueLayout.OfInt;
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.VarHandle;
 
 import static java.lang.foreign.ValueLayout.ADDRESS;
+import static java.lang.foreign.ValueLayout.ADDRESS_UNALIGNED;
 import static java.lang.foreign.ValueLayout.JAVA_INT;
+import static java.lang.foreign.ValueLayout.JAVA_INT_UNALIGNED;
+import static java.lang.foreign.ValueLayout.JAVA_LONG_UNALIGNED;
 import static net.codecrete.usb.linux.Linux.allocateErrorState;
 import static net.codecrete.usb.linux.LinuxUsbException.throwLastError;
 import static net.codecrete.usb.linux.gen.epoll.epoll.EPOLL_CTL_ADD;
 import static net.codecrete.usb.linux.gen.epoll.epoll.EPOLL_CTL_DEL;
 
 @SuppressWarnings({"OptionalGetWithoutIsPresent", "SameParameterValue", "java:S100"})
 public class EPoll {
+    private EPoll() {}
+
+    private static final boolean IS_AARCH64 = System.getProperty("os.arch").equals("aarch64");
+
+    private static final GroupLayout DATA$LAYOUT = MemoryLayout.unionLayout(
+        ADDRESS_UNALIGNED.withName("ptr"),
+        JAVA_INT_UNALIGNED.withName("fd"),
+        JAVA_INT_UNALIGNED.withName("u32"),
+        JAVA_LONG_UNALIGNED.withName("u64")
+    ).withName("epoll_data");
+
+    static final GroupLayout EVENT$LAYOUT = IS_AARCH64
+            ? MemoryLayout.structLayout(
+                    JAVA_INT.withName("events"),
+                    MemoryLayout.paddingLayout(4),
+                    DATA$LAYOUT.withName("data")).withName("epoll_event")
+            : MemoryLayout.structLayout(
+                    JAVA_INT_UNALIGNED.withName("events"),
+                    DATA$LAYOUT.withName("data")).withName("epoll_event");
+
     // Memory layout for an array of epoll_event structs
-    private static final SequenceLayout EVENT_ARRAY$LAYOUT = MemoryLayout.sequenceLayout(1, epoll_event.layout());
+    private static final SequenceLayout EVENT_ARRAY$LAYOUT = MemoryLayout.sequenceLayout(1, EVENT$LAYOUT);
 
     // varhandle to access the "fd" field in an array of epoll_event structs
     static final VarHandle EVENT_ARRAY_DATA_FD$VH = EVENT_ARRAY$LAYOUT.varHandle(
@@ -39,13 +64,16 @@ public class EPoll {
     );
 
     // varhandle to access the "fd" field in an epoll_event struct
-    static final VarHandle EVENT_DATA_FD$VH = epoll_event.layout().varHandle(
+    static final VarHandle EVENT_DATA_FD$VH = EVENT$LAYOUT.varHandle(
             MemoryLayout.PathElement.groupElement("data"),
             MemoryLayout.PathElement.groupElement("fd")
     );
 
+    private static final OfInt EVENT_EVENTS$LAYOUT = (OfInt)EVENT$LAYOUT.select(PathElement.groupElement("events"));
 
-    private EPoll() {}
+    private static void event_events(MemorySegment struct, int fieldValue) {
+        struct.set(EVENT_EVENTS$LAYOUT, 0, fieldValue);
+    }
 
     private static final Linker linker = Linker.nativeLinker();
 
@@ -89,8 +117,8 @@ static void addFileDescriptor(int epfd, int op, int fd) {
         try (var arena = Arena.ofConfined()) {
             var errorState = allocateErrorState(arena);
 
-            var event = arena.allocate(epoll_event.layout());
-            epoll_event.events(event, op);
+            var event = arena.allocate(EVENT$LAYOUT);
+            event_events(event, op);
             EVENT_DATA_FD$VH.set(event, 0, fd);
             var ret = epoll_ctl(epfd, EPOLL_CTL_ADD(), fd, event, errorState);
             if (ret < 0)
@@ -102,8 +130,8 @@ static void removeFileDescriptor(int epfd, int fd) {
         try (var arena = Arena.ofConfined()) {
             var errorState = allocateErrorState(arena);
 
-            var event = arena.allocate(epoll_event.layout());
-            epoll_event.events(event, 0);
+            var event = arena.allocate(EVENT$LAYOUT);
+            event_events(event, 0);
             EVENT_DATA_FD$VH.set(event, 0, fd);
             var ret = epoll_ctl(epfd, EPOLL_CTL_DEL(), fd, event, errorState);
             if (ret < 0) {

java-does-usb/src/main/java/net/codecrete/usb/linux/LinuxAsyncTask.java

@@ -8,7 +8,6 @@
 package net.codecrete.usb.linux;
 
 import net.codecrete.usb.UsbTransferType;
-import net.codecrete.usb.linux.gen.epoll.epoll_event;
 import net.codecrete.usb.linux.gen.errno.errno;
 import net.codecrete.usb.linux.gen.usbdevice_fs.usbdevfs_urb;
 
@@ -84,7 +83,7 @@ private void asyncCompletionTask() {
         try (var arena = Arena.ofConfined()) {
             var errorState = allocateErrorState(arena);
             var urbPointerHolder = arena.allocate(ADDRESS);
-            var events = arena.allocate(epoll_event.layout(), NUM_EVENTS);
+            var events = arena.allocate(EPoll.EVENT$LAYOUT, NUM_EVENTS);
 
             while (true) {
 

java-does-usb/src/main/java/net/codecrete/usb/linux/LinuxUsbDeviceRegistry.java

@@ -10,7 +10,6 @@
 import net.codecrete.usb.UsbDevice;
 import net.codecrete.usb.common.ScopeCleanup;
 import net.codecrete.usb.common.UsbDeviceRegistry;
-import net.codecrete.usb.linux.gen.epoll.epoll_event;
 import net.codecrete.usb.linux.gen.udev.udev;
 
 import java.lang.foreign.Arena;
@@ -111,7 +110,7 @@ protected void monitorDevices() {
             EPoll.addFileDescriptor(epfd, EPOLLIN(), monitorFd);
 
             // allocate event (as output for epoll_wait)
-            var event = arena.allocate(epoll_event.layout());
+            var event = arena.allocate(EPoll.EVENT$LAYOUT);
 
             // monitor device changes
             //noinspection InfiniteLoopStatement