1 files changed, 103 insertions, 0 deletions
diff --git a/include/cutils/abort_socket.h b/include/cutils/abort_socket.h
new file mode 100644
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--- /dev/null
+++ b/include/cutils/abort_socket.h
@@ -0,0 +1,103 @@
+/*
+ * Copyright 2009, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* Helper to perform abortable blocking operations on a socket:
+ *   asocket_connect()
+ *   asocket_accept()
+ *   asocket_read()
+ *   asocket_write()
+ * These calls are similar to the regular syscalls, but can be aborted with:
+ *   asocket_abort()
+ *
+ * Calling close() on a regular POSIX socket does not abort blocked syscalls on
+ * that socket in other threads.
+ *
+ * After calling asocket_abort() the socket cannot be reused.
+ *
+ * Call asocket_destory() *after* all threads have finished with the socket to
+ * finish closing the socket and free the asocket structure.
+ *
+ * The helper is implemented by setting the socket non-blocking to initiate
+ * syscalls connect(), accept(), read(), write(), then using a blocking poll()
+ * on both the primary socket and a local pipe. This makes the poll() abortable
+ * by writing a byte to the local pipe in asocket_abort().
+ *
+ * asocket_create() sets the fd to non-blocking mode. It must not be changed to
+ * blocking mode.
+ *
+ * Using asocket will triple the number of file descriptors required per
+ * socket, due to the local pipe. It may be possible to use a global pipe per
+ * process rather than per socket, but we have not been able to come up with a
+ * race-free implementation yet.
+ *
+ * All functions except asocket_init() and asocket_destroy() are thread safe.
+ */
+
+#include <stdlib.h>
+#include <sys/socket.h>
+
+#ifndef __CUTILS_ABORT_SOCKET_H__
+#define __CUTILS_ABORT_SOCKET_H__
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct asocket {
+    int fd;           /* primary socket fd */
+    int abort_fd[2];  /* pipe used to abort */
+};
+
+/* Create an asocket from fd.
+ * Sets the socket to non-blocking mode.
+ * Returns NULL on error with errno set.
+ */
+struct asocket *asocket_init(int fd);
+
+/* Blocking socket I/O with timeout.
+ * Calling asocket_abort() from another thread will cause each of these
+ * functions to immediately return with value -1 and errno ECANCELED.
+ * timeout is in ms, use -1 to indicate no timeout. On timeout -1 is returned
+ * with errno ETIMEDOUT.
+ * EINTR is handled in-call.
+ * Other semantics are identical to the regular syscalls.
+ */
+int asocket_connect(struct asocket *s, const struct sockaddr *addr,
+        socklen_t addrlen, int timeout);
+
+int asocket_accept(struct asocket *s, struct sockaddr *addr,
+        socklen_t *addrlen, int timeout);
+
+int asocket_read(struct asocket *s, void *buf, size_t count, int timeout);
+
+int asocket_write(struct asocket *s, const void *buf, size_t count,
+        int timeout);
+
+/* Abort above calls and shutdown socket.
+ * Further I/O operations on this socket will immediately fail after this call.
+ * asocket_destroy() should be used to release resources once all threads
+ * have returned from blocking calls on the socket.
+ */
+void asocket_abort(struct asocket *s);
+
+/* Close socket and free asocket structure.
+ * Must not be called until all calls on this structure have completed.
+ */
+void asocket_destroy(struct asocket *s);
+
+#ifdef __cplusplus
+}
+#endif
+#endif //__CUTILS_ABORT_SOCKET__H__