2 * Copyright (c) 2008, 2009, 2010 Zmanda, Inc. All Rights Reserved.
4 * This program is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 as published
6 * by the Free Software Foundation.
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
10 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * You should have received a copy of the GNU General Public License along
14 * with this program; if not, write to the Free Software Foundation, Inc.,
15 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17 * Contact information: Zmanda Inc., 465 S. Mathilda Ave., Suite 300
18 * Sunnyvale, CA 94085, USA, or: http://www.zmanda.com
21 /* An Xfer abstracts an active data transfer through the Amanda core.
29 /* An Xfer represents a flow of data from a source, via zero or more filters,
30 * to a destination. Sources, filters, and destinations are "transfer elements".
31 * The job of the Xfer is glue together a sequence of elements, and provide a
32 * dispatch point for messages from those elements to the caller.
34 * Xfers are not implemented as GObjects because there is no reason to subclass an
35 * Xfer or apply any of the other features that come with GObject.
38 /* The moment-to-moment state of a transfer */
40 XFER_INIT = 1, /* initializing */
41 XFER_START = 2, /* starting */
42 XFER_RUNNING = 3, /* data flowing */
43 XFER_CANCELLING = 4,/* cancellation begun */
44 XFER_CANCELLED = 5, /* all elements cancelled; draining data */
45 XFER_DONE = 6, /* data no longer flowing */
48 /* forward declarations */
58 /* The current status of this transfer. This is read-only, and
59 * must only be accessed from the main thread or with status_mutex
63 /* lock this while checking status in a thread
64 * other than the main thread */
67 /* and wait on this for status changes */
70 /* -- remaining fields are private -- */
74 /* All transfer elements for this transfer, in order from
75 * source to destination. This is initialized when the Xfer is
79 /* temporary string for a representation of this transfer */
82 /* GSource and queue for incoming messages */
83 struct XMsgSource *msg_source;
86 /* Number of active elements remaining (a.k.a. the number of
87 * XMSG_DONE messages to expect) */
88 gint num_active_elements;
90 /* Used to coordinate handing off file descriptors among elements of this
95 typedef struct Xfer Xfer;
97 /* Note that all functions must be called from the main thread unless
100 /* Create a new Xfer object, which should later be freed with xfref_free.
102 * This function adds a reference to each element. The caller should
103 * unreference the elements if it does not intend to use them directly.
104 * The Xfer returned has a refcount of one.
106 * @param elements: array of pointers to transfer elements, in order from source
108 * @param nelements: length of 'elements'
109 * @returns: new Xfer object
111 Xfer *xfer_new(struct XferElement **elements, unsigned int nelements);
113 /* Increase the reference count of a transfer.
115 * @param xfer: the transfer
117 void xfer_ref(Xfer *xfer);
119 /* Decrease the reference count of a transfer, possibly freeing it. A running
120 * transfer (state neither XFER_INIT nor XFER_DONE) will not be freed.
122 * @param xfer: the transfer
124 void xfer_unref(Xfer *xfer);
126 /* Get a GSource which will produce events corresponding to messages from
127 * this transfer. This is a "peek" operation, so the reference count for the
128 * GSource is not affected. Note that the same GSource is returned on every
129 * call for a particular transfer.
131 * @returns: GSource object
133 GSource *xfer_get_source(Xfer *xfer);
135 /* Typedef for the callback to be set on the GSource returned from
138 typedef void (*XMsgCallback)(gpointer data, struct XMsg *msg, Xfer *xfer);
140 /* Queue a message for delivery via this transfer's GSource. This can
141 * be called in any thread.
143 * @param xfer: the transfer
144 * @param msg: the message to queue
146 void xfer_queue_message(Xfer *xfer, struct XMsg *msg);
148 /* Get a representation of this transfer. The string belongs to the transfer, and
149 * will be freed when the transfer is freed.
151 * @param xfer: the Xfer object
152 * @returns: statically allocated string
154 char *xfer_repr(Xfer *xfer);
156 /* Start a transfer. This function will fail with an error message if it is
157 * unable to set up the transfer (e.g., if the elements cannot be connected
160 * @param xfer: the Xfer object
162 void xfer_start(Xfer *xfer);
164 /* Abort a running transfer. This essentially tells the source to stop
165 * producing data and allows the remainder of the transfer to "drain". Thus
166 * the transfer will signal its completion "normally" some time after
167 * xfer_cancel returns. In particular, the state transitions will occur
171 * - xfer_cancel() (note state may still be XFER_RUNNING on return)
173 * - (individual elements' cancel() methods are invoked)
175 * - (data drains from the transfer)
178 * This function can be called from any thread at any time. It will return
181 * @param xfer: the Xfer object
183 void xfer_cancel(Xfer *xfer);
189 /* Wait for the xfer's state to become CANCELLED or DONE; this is useful to
190 * wait until a cancelletion is in progress before returning an EOF or
191 * otherwise handling a failure. If you call this in the main thread, you'll
192 * be waiting for a while.
194 * @param xfer: the transfer object
195 * @returns: the new status (XFER_CANCELLED or XFER_DONE)
197 xfer_status wait_until_xfer_cancelled(Xfer *xfer);
199 /* Wait for the xfer's state to become anything but START; this is
200 * called *automatically* for every xfer_element_pull_buffer call, as the
201 * upstream element may not be running and ready for a pull just yet. But
202 * the function may be useful in other places, too.
204 * @param xfer: the transfer object
205 * @returns: the new status (XFER_CANCELLED or XFER_DONE)
207 xfer_status wait_until_xfer_running(Xfer *xfer);
209 /* Send an XMSG_ERROR constructed with the given format and arguments, then
210 * cancel the transfer, then wait until the transfer is completely cancelled.
211 * This is the most common error-handling process for transfer elements. All
212 * that remains to be done on return is to branch to the appropriate point in
213 * the cancellation-handling portion of the transfer.
215 * @param elt: the transfer element producing the error
216 * @param fmt: the format for the error message
217 * @param ...: arguments corresponding to the format
219 void xfer_cancel_with_error(struct XferElement *elt, const char *fmt, ...)
222 /* Return the fd in *FDP and set *FDP to NEWFD, all in one step. The operation
223 * is atomic with respect to all other such operations in this transfer, making
224 * this a good way to "move" a file descriptor from one element to another. If
225 * xfer is NULL, the operation proceeds with no locking.
227 * @param xfer: the xfer within which this fd is used
228 * @param fdp: pointer to the file descriptor to swap
229 * @param newfd: the new value for *FDP
230 * @returns: the previous contents of *fdp (may be -1)
232 gint xfer_atomic_swap_fd(Xfer *xfer, gint *fdp, gint newfd);