WIP: Aaand it....... hangs!

src/test/java/org/apposed/appose/SharedMemoryTest.java

@@ -31,6 +31,10 @@
 
 import org.junit.jupiter.api.Test;
 
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
 import java.nio.ByteBuffer;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -72,13 +76,47 @@ public void testShmCreate() {
 		}
 	}
 
-	public void testShmAttach() {
-		// TODO: ProcessBuilder exec a Python that constructs a new
-		//  shared memory using Python's plain SharedMemory API.
-		//  Modify it from Python as well, then attach to it here
-		//  and validate that the modifications there are accessible
-		//  here afterward.
-		//  What about Python's forced unlinking? Problem here?
-	}
+	@Test
+	public void testShmAttach() throws IOException {
+		ProcessBuilder pb = new ProcessBuilder();
+		boolean windows = System.getProperty("os.name").startsWith("Win");
+		String pythonCommand =  windows ? "python.exe" : "python";
+		Process p = new ProcessBuilder().command(pythonCommand, "-c", //
+			"from multiprocessing.shared_memory import SharedMemory;" + //
+			"from sys import stdin, stdout;" + //
+			"shm = SharedMemory(create=True, size=345);" + //
+			"shm.buf[0] = 123;" + //
+			"shm.buf[100] = 45;" + //
+			"shm.buf[344] = 67;" + //
+			"stdout.write(f'{shm.name}|{shm.size}');" + //
+			"stdout.flush();" + //
+			"stdin.readline();" + //
+			"shm.unlink()" //
+		).start();
+
+		// Read the name of the shared memory that Python created.
+		BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
+		String[] shmInfo = in.readLine().split("|");
+		assertEquals(2, shmInfo.length);
+		String shmName = shmInfo[0];
+		int shmSize = Integer.parseInt(shmInfo[1]);
+		assertEquals(345, shmSize);
 
+		// Attach to the shared memory.
+		try (SharedMemory shm = SharedMemory.attach(shmName)) {
+			assertNotNull(shm);
+			assertEquals(shmName, shm.name());
+			assertEquals(shmSize, shm.size());
+			ByteBuffer buf = shm.pointer().getByteBuffer(0, shmSize);
+			// TODO: byte values > 127
+			assertEquals(123, buf.get(0));
+			assertEquals(45, buf.get(100));
+			assertEquals(67, buf.get(344));
+		}
+
+		// Close out the Python process.
+		OutputStream os = p.getOutputStream();
+		os.write('\n');
+		os.flush();
+	}
 }