common,native: Properly handle virtual non-blocking connect, read

On Windows, "connect" may return "already is connected", whereas a
non-blocking read may erroneously be thrown as an exception.

junixsocket-common/src/main/java/org/newsclub/net/unix/AFSocketImpl.java

@@ -484,7 +484,7 @@ final boolean connect0(SocketAddress addr, int connectTimeout) throws IOExceptio
  core.configureVirtualBlocking(true);
  }
  try {
- success = NativeUnixSocket.connect(ab, ab.limit(), fd, -1);
+ success = NativeUnixSocket.connect(ab, ab.limit(), fd, -2);
  if (!success && virtualBlocking) {
  // try again (non-blocking timeout)
  if (virtualConnectTimeout == null) {
@@ -627,6 +627,8 @@ public int read(byte[] buf, int off, int len) throws IOException {
  opt = defaultOpt;
  }
 
+ int read;
+
  boolean park = false;
  virtualThreadLoop : do {
  if (virtualBlocking) {
@@ -638,8 +640,17 @@ public int read(byte[] buf, int off, int len) throws IOException {
  }
 
  try {
- return NativeUnixSocket.read(fdesc, buf, off, len, opt, ancillaryDataSupport,
+ read = NativeUnixSocket.read(fdesc, buf, off, len, opt, ancillaryDataSupport,
  socketTimeout.get());
+ if (read == -2) {
+ if (virtualBlocking) {
+ // sleep again
+ park = true;
+ continue virtualThreadLoop;
+ } else {
+ read = 0;
+ }
+ }
  } catch (SocketTimeoutException e) {
  if (virtualBlocking) {
  // sleep again
@@ -656,7 +667,10 @@ public int read(byte[] buf, int off, int len) throws IOException {
  core.configureVirtualBlocking(false);
  }
  }
+ break; // NOPMD.AvoidBranchingStatementAsLastInLoop virtualThreadLoop
  } while (true); // NOPMD.WhileLoopWithLiteralBoolean
+
+ return read;
  }
 
  @SuppressWarnings("PMD.CognitiveComplexity")
@@ -695,6 +709,15 @@ public int read() throws IOException {
  int byteRead = NativeUnixSocket.read(fdesc, null, 0, 1, opt, ancillaryDataSupport,
  socketTimeout.get());
  if (byteRead < 0) {
+ if (byteRead == -2) {
+ if (virtualBlocking) {
+ // sleep again
+ park = true;
+ continue virtualThreadLoop;
+ } else {
+ byteRead = -1;
+ }
+ }
  eofReached.set(true);
  return -1;
  } else {

junixsocket-native/src/main/c/connect.c

@@ -35,6 +35,14 @@ JNIEXPORT jboolean JNICALL Java_org_newsclub_net_unix_NativeUnixSocket_connect
  JNIEnv * env, jclass clazz CK_UNUSED, jobject ab, jint abLen, jobject fd,
  jlong expectedInode)
 {
+ jboolean existingConnectOK;
+ if(expectedInode == -2) {
+ expectedInode = -1;
+ existingConnectOK = true;
+ } else {
+ existingConnectOK = false;
+ }
+
  jux_sockaddr_t *addr = (*env)->GetDirectBufferAddress(env, ab);
  socklen_t addrLength = (socklen_t)abLen;
  if(addrLength == 0) {
@@ -80,7 +88,9 @@ JNIEXPORT jboolean JNICALL Java_org_newsclub_net_unix_NativeUnixSocket_connect
  } while(ret == -1 && myErr == EINTR);
 
  if(ret == -1) {
- if(checkNonBlocking(socketHandle, myErr)) {
+ if(myErr == EISCONN && existingConnectOK) {
+ return true;
+ } else if(checkNonBlocking(socketHandle, myErr)) {
  // non-blocking connect
  return false;
  } else {

junixsocket-native/src/main/c/receive.c

@@ -276,8 +276,12 @@ JNIEXPORT jint JNICALL Java_org_newsclub_net_unix_NativeUnixSocket_read(
  jint returnValue;
  if(count < 0) {
  // read(2) returns -1 on error. Java throws an Exception.
- _throwErrnumException(env, errno, fd);
- returnValue = -1;
+ if(errno == EWOULDBLOCK) {
+ returnValue = -2;
+ } else {
+ _throwErrnumException(env, errno, fd);
+ returnValue = -1;
+ }
  } else if(count == 0) {
  // read(2)/recv return 0 on EOF. Java returns -1.
  returnValue = -1;