GUAC-236: Add guac_socket_tee() function which allocates a socket that delegates all operations to a primary socket while duplicating write operations to a secondary socket.

src/libguac/Makefile.am

@@ -89,6 +89,7 @@ libguac_la_SOURCES =  \
     socket.c          \
     socket-fd.c       \
     socket-nest.c     \
+    socket-tee.c      \
     timestamp.c       \
     unicode.c         \
     user.c            \

src/libguac/guacamole/socket.h

@@ -191,6 +191,38 @@ guac_socket* guac_socket_open(int fd);
  */
 guac_socket* guac_socket_nest(guac_socket* parent, int index);
 
+/**
+ * Allocates and initializes a new guac_socket which delegates all socket
+ * operations to the given primary socket, while simultaneously duplicating all
+ * written data to the secondary socket. Freeing the returned guac_socket will
+ * free both primary and secondary sockets.
+ *
+ * Return values (error codes) will come only from the primary socket. Locks
+ * (like those used by guac_socket_instruction_begin() and
+ * guac_socket_instruction_end()) will affect only the primary socket.
+ *
+ * If an error occurs while allocating the guac_socket object, NULL is returned,
+ * and guac_error is set appropriately.
+ *
+ * @param primary
+ *     The primary guac_socket to which all socket operations should be
+ *     delegated. The error codes returned by socket operations, if any, will
+ *     always come from this socket. This socket will also be the only socket
+ *     locked when instructions begin (or unlocked when instructions end).
+ *
+ * @param secondary
+ *     The secondary guac_socket to which all data written to the primary
+ *     guac_socket should be copied. If an error prevents the write from
+ *     succeeding, that error will be ignored. Only errors from the primary
+ *     guac_socket will be acknowledged.
+ *
+ * @return
+ *     A newly allocated guac_socket object associated with the given primary
+ *     and secondary sockets, or NULL if an error occurs while allocating the
+ *     guac_socket object.
+ */
+guac_socket* guac_socket_tee(guac_socket* primary, guac_socket* secondary);
+
 /**
  * Writes the given unsigned int to the given guac_socket object. The data
  * written may be buffered until the buffer is flushed automatically or

src/libguac/socket-tee.c

@@ -0,0 +1,234 @@
+/*
+ * Copyright (C) 2016 Glyptodon LLC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "config.h"
+
+#include "socket.h"
+
+#include <stdlib.h>
+
+/**
+ * Data specific to the tee implementation of guac_socket.
+ */
+typedef struct guac_socket_tee_data {
+
+    /**
+     * The guac_socket to which all socket operations should be delegated.
+     */
+    guac_socket* primary;
+
+    /**
+     * The guac_socket to which all write and flush operations should be
+     * duplicated.
+     */
+    guac_socket* secondary;
+
+} guac_socket_tee_data;
+
+/**
+ * Callback function which reads only from the primary socket.
+ *
+ * @param socket
+ *     The tee socket to read from.
+ *
+ * @param buf
+ *     The buffer to read data into.
+ *
+ * @param count
+ *     The maximum number of bytes to read into the given buffer.
+ *
+ * @return
+ *     The value returned by guac_socket_read() when invoked on the primary
+ *     socket with the given parameters.
+ */
+static ssize_t __guac_socket_tee_read_handler(guac_socket* socket,
+        void* buf, size_t count) {
+
+    guac_socket_tee_data* data = (guac_socket_tee_data*) socket->data;
+
+    /* Delegate read to wrapped socket */
+    return guac_socket_read(data->primary, buf, count);
+
+}
+
+/**
+ * Callback function which writes the given data to both underlying sockets,
+ * returning only the result from the primary socket.
+ *
+ * @param socket
+ *     The tee socket to write through.
+ *
+ * @param buf
+ *     The buffer of data to write.
+ *
+ * @param count
+ *     The number of bytes in the buffer to be written.
+ *
+ * @return
+ *     The number of bytes written if the write was successful, or -1 if an
+ *     error occurs.
+ */
+static ssize_t __guac_socket_tee_write_handler(guac_socket* socket,
+        const void* buf, size_t count) {
+
+    guac_socket_tee_data* data = (guac_socket_tee_data*) socket->data;
+
+    /* Write to secondary socket (ignoring result) */
+    guac_socket_write(data->secondary, buf, count);
+
+    /* Delegate write to wrapped socket */
+    if (guac_socket_write(data->primary, buf, count))
+        return -1;
+
+    /* All data written successfully */
+    return count;
+
+}
+
+/**
+ * Callback function which flushes both underlying sockets, returning only the
+ * result from the primary socket.
+ *
+ * @param socket
+ *     The tee socket to flush.
+ *
+ * @return
+ *     The value returned by guac_socket_flush() when invoked on the primary
+ *     socket.
+ */
+static ssize_t __guac_socket_tee_flush_handler(guac_socket* socket) {
+
+    guac_socket_tee_data* data = (guac_socket_tee_data*) socket->data;
+
+    /* Flush secondary socket (ignoring result) */
+    guac_socket_flush(data->secondary);
+
+    /* Delegate flush to wrapped socket */
+    return guac_socket_flush(data->primary);
+
+}
+
+/**
+ * Callback function which delegates the lock operation to the primary
+ * socket alone.
+ *
+ * @param socket
+ *     The tee socket on which guac_socket_instruction_begin() was invoked.
+ */
+static void __guac_socket_tee_lock_handler(guac_socket* socket) {
+
+    guac_socket_tee_data* data = (guac_socket_tee_data*) socket->data;
+
+    /* Delegate lock to wrapped socket */
+    guac_socket_instruction_begin(data->primary);
+
+}
+
+/**
+ * Callback function which delegates the unlock operation to the primary
+ * socket alone.
+ *
+ * @param socket
+ *     The tee socket on which guac_socket_instruction_end() was invoked.
+ */
+static void __guac_socket_tee_unlock_handler(guac_socket* socket) {
+
+    guac_socket_tee_data* data = (guac_socket_tee_data*) socket->data;
+
+    /* Delegate unlock to wrapped socket */
+    guac_socket_instruction_end(data->primary);
+
+}
+
+/**
+ * Callback function which delegates the select operation to the primary
+ * socket alone.
+ *
+ * @param socket
+ *     The tee socket on which guac_socket_select() was invoked.
+ *
+ * @param usec_timeout
+ *     The timeout to specify when invoking guac_socket_select() on the
+ *     primary socket.
+ *
+ * @return
+ *     The value returned by guac_socket_select() when invoked with the
+ *     given parameters on the primary socket.
+ */
+static int __guac_socket_tee_select_handler(guac_socket* socket,
+        int usec_timeout) {
+
+    guac_socket_tee_data* data = (guac_socket_tee_data*) socket->data;
+
+    /* Delegate select to wrapped socket */
+    return guac_socket_select(data->primary, usec_timeout);
+
+}
+
+/**
+ * Callback function which frees all underlying data associated with the
+ * given tee socket, including both primary and secondary sockets.
+ *
+ * @param socket
+ *     The tee socket being freed.
+ *
+ * @return
+ *     Always zero.
+ */
+static int __guac_socket_tee_free_handler(guac_socket* socket) {
+
+    guac_socket_tee_data* data = (guac_socket_tee_data*) socket->data;
+
+    /* Free underlying sockets */
+    guac_socket_free(data->primary);
+    guac_socket_free(data->secondary);
+
+    /* Freeing the tee socket always succeeds */
+    free(data);
+    return 0;
+
+}
+
+guac_socket* guac_socket_tee(guac_socket* primary, guac_socket* secondary) {
+
+    /* Set up socket to split outout into a file */
+    guac_socket_tee_data* data = malloc(sizeof(guac_socket_tee_data));
+    data->primary = primary;
+    data->secondary = secondary;
+
+    /* Associate tee-specific data with new socket */
+    guac_socket* socket = guac_socket_alloc();
+    socket->data = data;
+
+    /* Assign handlers */
+    socket->read_handler   = __guac_socket_tee_read_handler;
+    socket->write_handler  = __guac_socket_tee_write_handler;
+    socket->select_handler = __guac_socket_tee_select_handler;
+    socket->flush_handler  = __guac_socket_tee_flush_handler;
+    socket->lock_handler   = __guac_socket_tee_lock_handler;
+    socket->unlock_handler = __guac_socket_tee_unlock_handler;
+    socket->free_handler   = __guac_socket_tee_free_handler;
+
+    return socket;
+
+}
+