/* GIO - GLib Input, Output and Streaming Library
*
* Copyright 2015 Collabora Ltd.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
* Authors: Philip Withnall <philip.withnall@collabora.co.uk>
*/
#include "config.h"
#include "gdatagrambased.h"
#include "gcancellable.h"
#include "gioenumtypes.h"
#include "gioerror.h"
#include "gnetworkingprivate.h"
#include "gsocketaddress.h"
#include "glibintl.h"
/**
* SECTION:gdatagrambased
* @short_description: Low-level datagram communications interface
* @include: gio/gio.h
* @see_also: #GSocket, [<gnetworking.h>][gio-gnetworking.h]
*
* A #GDatagramBased is a networking interface for representing datagram-based
* communications. It is a more or less direct mapping of the core parts of the
* BSD socket API in a portable GObject interface. It is implemented by
* #GSocket, which wraps the UNIX socket API on UNIX and winsock2 on Windows.
*
* #GDatagramBased is entirely platform independent, and is intended to be used
* alongside higher-level networking APIs such as #GIOStream.
*
* It uses vectored scatter/gather I/O by default, allowing for many messages
* to be sent or received in a single call. Where possible, implementations of
* the interface should take advantage of vectored I/O to minimise processing
* or system calls. For example, #GSocket uses recvmmsg() and sendmmsg() where
* possible. Callers should take advantage of scatter/gather I/O (the use of
* multiple buffers per message) to avoid unnecessary copying of data to
* assemble or disassemble a message.
*
* Each #GDatagramBased operation has a timeout parameter which may be negative
* for blocking behaviour, zero for non-blocking behaviour, or positive for
* timeout behaviour. A blocking operation blocks until finished or there is an
* error. A non-blocking operation will return immediately with a
* %G_IO_ERROR_WOULD_BLOCK error if it cannot make progress. A timeout operation
* will block until the operation is complete or the timeout expires; if the
* timeout expires it will return what progress it made, or
* %G_IO_ERROR_TIMED_OUT if no progress was made. To know when a call would
* successfully run you can call g_datagram_based_condition_check() or
* g_datagram_based_condition_wait(). You can also use
* g_datagram_based_create_source() and attach it to a #GMainContext to get
* callbacks when I/O is possible.
*
* When running a non-blocking operation applications should always be able to
* handle getting a %G_IO_ERROR_WOULD_BLOCK error even when some other function
* said that I/O was possible. This can easily happen in case of a race
* condition in the application, but it can also happen for other reasons. For
* instance, on Windows a socket is always seen as writable until a write
* returns %G_IO_ERROR_WOULD_BLOCK.
*
* As with #GSocket, #GDatagramBaseds can be either connection oriented (for
* example, SCTP) or connectionless (for example, UDP). #GDatagramBaseds must be
* datagram-based, not stream-based. The interface does not cover connection
* establishment — use methods on the underlying type to establish a connection
* before sending and receiving data through the #GDatagramBased API. For
* connectionless socket types the target/source address is specified or
* received in each I/O operation.
*
* Like most other APIs in GLib, #GDatagramBased is not inherently thread safe.
* To use a #GDatagramBased concurrently from multiple threads, you must
* implement your own locking.
*
* Since: 2.48
*/
G_DEFINE_INTERFACE (GDatagramBased, g_datagram_based, G_TYPE_OBJECT)
static void
g_datagram_based_default_init (GDatagramBasedInterface *iface)
{
/* Nothing here. */
}
/**
* g_datagram_based_receive_messages:
* @datagram_based: a #GDatagramBased
* @messages: (array length=num_messages): an array of #GInputMessage structs
* @num_messages: the number of elements in @messages
* @flags: an int containing #GSocketMsgFlags flags for the overall operation
* @timeout: the maximum time (in microseconds) to wait, 0 to not block, or -1
* to block indefinitely
* @cancellable: (nullable): a %GCancellable
* @error: return location for a #GError
*
* Receive one or more data messages from @datagram_based in one go.
*
* @messages must point to an array of #GInputMessage structs and
* @num_messages must be the length of this array. Each #GInputMessage
* contains a pointer to an array of #GInputVector structs describing the
* buffers that the data received in each message will be written to.
*
* @flags modify how all messages are received. The commonly available
* arguments for this are available in the #GSocketMsgFlags enum, but the
* values there are the same as the system values, and the flags
* are passed in as-is, so you can pass in system-specific flags too. These
* flags affect the overall receive operation. Flags affecting individual
* messages are returned in #GInputMessage.flags.
*
* The other members of #GInputMessage are treated as described in its
* documentation.
*
* If @timeout is negative the call will block until @num_messages have been
* received, the connection is closed remotely (EOS), @cancellable is cancelled,
* or an error occurs.
*
* If @timeout is 0 the call will return up to @num_messages without blocking,
* or %G_IO_ERROR_WOULD_BLOCK if no messages are queued in the operating system
* to be received.
*
* If @timeout is positive the call will block on the same conditions as if
* @timeout were negative. If the timeout is reached
* before any messages are received, %G_IO_ERROR_TIMED_OUT is returned,
* otherwise it will return the number of messages received before timing out.
* (Note: This is effectively the behaviour of `MSG_WAITFORONE` with
* recvmmsg().)
*
* To be notified when messages are available, wait for the %G_IO_IN condition.
* Note though that you may still receive %G_IO_ERROR_WOULD_BLOCK from
* g_datagram_based_receive_messages() even if you were previously notified of a
* %G_IO_IN condition.
*
* If the remote peer closes the connection, any messages queued in the
* underlying receive buffer will be returned, and subsequent calls to
* g_datagram_based_receive_messages() will return 0 (with no error set).
*
* If the connection is shut down or closed (by calling g_socket_close() or
* g_socket_shutdown() with @shutdown_read set, if it’s a #GSocket, for
* example), all calls to this function will return %G_IO_ERROR_CLOSED.
*
* On error -1 is returned and @error is set accordingly. An error will only
* be returned if zero messages could be received; otherwise the number of
* messages successfully received before the error will be returned. If
* @cancellable is cancelled, %G_IO_ERROR_CANCELLED is returned as with any
* other error.
*
* Returns: number of messages received, or -1 on error. Note that the number
* of messages received may be smaller than @num_messages if @timeout is
* zero or positive, if the peer closed the connection, or if @num_messages
* was larger than `UIO_MAXIOV` (1024), in which case the caller may re-try
* to receive the remaining messages.
*
* Since: 2.48
*/
gint
g_datagram_based_receive_messages (GDatagramBased *datagram_based,
GInputMessage *messages,
guint num_messages,
gint flags,
gint64 timeout,
GCancellable *cancellable,
GError **error)
{
GDatagramBasedInterface *iface;
gint retval;
GError *child_error = NULL;
g_return_val_if_fail (G_IS_DATAGRAM_BASED (datagram_based), -1);
g_return_val_if_fail (num_messages == 0 || messages != NULL, -1);
g_return_val_if_fail (cancellable == NULL ||
G_IS_CANCELLABLE (cancellable), -1);
g_return_val_if_fail (error == NULL || *error == NULL, -1);
iface = G_DATAGRAM_BASED_GET_IFACE (datagram_based);
g_assert (iface->receive_messages != NULL);
retval = iface->receive_messages (datagram_based, messages, num_messages,
flags, timeout, cancellable, &child_error);
/* Postconditions. */
g_return_val_if_fail ((retval < 0) == (child_error != NULL), -1);
g_return_val_if_fail (timeout == 0 ||
!g_error_matches (child_error, G_IO_ERROR,
G_IO_ERROR_WOULD_BLOCK), -1);
g_return_val_if_fail (timeout > 0 ||
!g_error_matches (child_error, G_IO_ERROR,
G_IO_ERROR_TIMED_OUT), -1);
g_return_val_if_fail (retval < 0 || (guint) retval <= num_messages, -1);
if (child_error != NULL)
g_propagate_error (error, child_error);
return retval;
}
/**
* g_datagram_based_send_messages:
* @datagram_based: a #GDatagramBased
* @messages: (array length=num_messages): an array of #GOutputMessage structs
* @num_messages: the number of elements in @messages
* @flags: an int containing #GSocketMsgFlags flags
* @timeout: the maximum time (in microseconds) to wait, 0 to not block, or -1
* to block indefinitely
* @cancellable: (nullable): a %GCancellable
* @error: return location for a #GError
*
* Send one or more data messages from @datagram_based in one go.
*
* @messages must point to an array of #GOutputMessage structs and
* @num_messages must be the length of this array. Each #GOutputMessage
* contains an address to send the data to, and a pointer to an array of
* #GOutputVector structs to describe the buffers that the data to be sent
* for each message will be gathered from.
*
* @flags modify how the message is sent. The commonly available arguments
* for this are available in the #GSocketMsgFlags enum, but the
* values there are the same as the system values, and the flags
* are passed in as-is, so you can pass in system-specific flags too.
*
* The other members of #GOutputMessage are treated as described in its
* documentation.
*
* If @timeout is negative the call will block until @num_messages have been
* sent, @cancellable is cancelled, or an error occurs.
*
* If @timeout is 0 the call will send up to @num_messages without blocking,
* or will return %G_IO_ERROR_WOULD_BLOCK if there is no space to send messages.
*
* If @timeout is positive the call will block on the same conditions as if
* @timeout were negative. If the timeout is reached before any messages are
* sent, %G_IO_ERROR_TIMED_OUT is returned, otherwise it will return the number
* of messages sent before timing out.
*
* To be notified when messages can be sent, wait for the %G_IO_OUT condition.
* Note though that you may still receive %G_IO_ERROR_WOULD_BLOCK from
* g_datagram_based_send_messages() even if you were previously notified of a
* %G_IO_OUT condition. (On Windows in particular, this is very common due to
* the way the underlying APIs work.)
*
* If the connection is shut down or closed (by calling g_socket_close() or
* g_socket_shutdown() with @shutdown_write set, if it’s a #GSocket, for
* example), all calls to this function will return %G_IO_ERROR_CLOSED.
*
* On error -1 is returned and @error is set accordingly. An error will only
* be returned if zero messages could be sent; otherwise the number of messages
* successfully sent before the error will be returned. If @cancellable is
* cancelled, %G_IO_ERROR_CANCELLED is returned as with any other error.
*
* Returns: number of messages sent, or -1 on error. Note that the number of
* messages sent may be smaller than @num_messages if @timeout is zero
* or positive, or if @num_messages was larger than `UIO_MAXIOV` (1024), in
* which case the caller may re-try to send the remaining messages.
*
* Since: 2.48
*/
gint
g_datagram_based_send_messages (GDatagramBased *datagram_based,
GOutputMessage *messages,
guint num_messages,
gint flags,
gint64 timeout,
GCancellable *cancellable,
GError **error)
{
GDatagramBasedInterface *iface;
gint retval;
GError *child_error = NULL;
g_return_val_if_fail (G_IS_DATAGRAM_BASED (datagram_based), -1);
g_return_val_if_fail (num_messages == 0 || messages != NULL, -1);
g_return_val_if_fail (cancellable == NULL ||
G_IS_CANCELLABLE (cancellable), -1);
g_return_val_if_fail (error == NULL || *error == NULL, -1);
iface = G_DATAGRAM_BASED_GET_IFACE (datagram_based);
g_assert (iface->send_messages != NULL);
retval = iface->send_messages (datagram_based, messages, num_messages, flags,
timeout, cancellable, &child_error);
/* Postconditions. */
g_return_val_if_fail ((retval < 0) == (child_error != NULL), -1);
g_return_val_if_fail (timeout == 0 ||
!g_error_matches (child_error, G_IO_ERROR,
G_IO_ERROR_WOULD_BLOCK), -1);
g_return_val_if_fail (timeout > 0 ||
!g_error_matches (child_error, G_IO_ERROR,
G_IO_ERROR_TIMED_OUT), -1);
g_return_val_if_fail (retval < 0 || (guint) retval <= num_messages, -1);
g_return_val_if_fail (!(timeout < 0 && num_messages > 0) || retval != 0, -1);
if (child_error != NULL)
g_propagate_error (error, child_error);
return retval;
}
/**
* g_datagram_based_create_source:
* @datagram_based: a #GDatagramBased
* @condition: a #GIOCondition mask to monitor
* @cancellable: (nullable): a #GCancellable
*
* Creates a #GSource that can be attached to a #GMainContext to monitor for
* the availability of the specified @condition on the #GDatagramBased. The
* #GSource keeps a reference to the @datagram_based.
*
* The callback on the source is of the #GDatagramBasedSourceFunc type.
*
* It is meaningless to specify %G_IO_ERR or %G_IO_HUP in @condition; these
* conditions will always be reported in the callback if they are true.
*
* If non-%NULL, @cancellable can be used to cancel the source, which will
* cause the source to trigger, reporting the current condition (which is
* likely 0 unless cancellation happened at the same time as a condition
* change). You can check for this in the callback using
* g_cancellable_is_cancelled().
*
* Returns: (transfer full): a newly allocated #GSource
*
* Since: 2.48
*/
GSource *
g_datagram_based_create_source (GDatagramBased *datagram_based,
GIOCondition condition,
GCancellable *cancellable)
{
GDatagramBasedInterface *iface;
g_return_val_if_fail (G_IS_DATAGRAM_BASED (datagram_based), NULL);
g_return_val_if_fail (cancellable == NULL ||
G_IS_CANCELLABLE (cancellable), NULL);
iface = G_DATAGRAM_BASED_GET_IFACE (datagram_based);
g_assert (iface->create_source != NULL);
return iface->create_source (datagram_based, condition, cancellable);
}
/**
* g_datagram_based_condition_check:
* @datagram_based: a #GDatagramBased
* @condition: a #GIOCondition mask to check
*
* Checks on the readiness of @datagram_based to perform operations. The
* operations specified in @condition are checked for and masked against the
* currently-satisfied conditions on @datagram_based. The result is returned.
*
* %G_IO_IN will be set in the return value if data is available to read with
* g_datagram_based_receive_messages(), or if the connection is closed remotely
* (EOS); and if the datagram_based has not been closed locally using some
* implementation-specific method (such as g_socket_close() or
* g_socket_shutdown() with @shutdown_read set, if it’s a #GSocket).
*
* If the connection is shut down or closed (by calling g_socket_close() or
* g_socket_shutdown() with @shutdown_read set, if it’s a #GSocket, for
* example), all calls to this function will return %G_IO_ERROR_CLOSED.
*
* %G_IO_OUT will be set if it is expected that at least one byte can be sent
* using g_datagram_based_send_messages() without blocking. It will not be set
* if the datagram_based has been closed locally.
*
* %G_IO_HUP will be set if the connection has been closed locally.
*
* %G_IO_ERR will be set if there was an asynchronous error in transmitting data
* previously enqueued using g_datagram_based_send_messages().
*
* Note that on Windows, it is possible for an operation to return
* %G_IO_ERROR_WOULD_BLOCK even immediately after
* g_datagram_based_condition_check() has claimed that the #GDatagramBased is
* ready for writing. Rather than calling g_datagram_based_condition_check() and
* then writing to the #GDatagramBased if it succeeds, it is generally better to
* simply try writing right away, and try again later if the initial attempt
* returns %G_IO_ERROR_WOULD_BLOCK.
*
* It is meaningless to specify %G_IO_ERR or %G_IO_HUP in @condition; these
* conditions will always be set in the output if they are true. Apart from
* these flags, the output is guaranteed to be masked by @condition.
*
* This call never blocks.
*
* Returns: the #GIOCondition mask of the current state
*
* Since: 2.48
*/
GIOCondition
g_datagram_based_condition_check (GDatagramBased *datagram_based,
GIOCondition condition)
{
GDatagramBasedInterface *iface;
GIOCondition out;
g_return_val_if_fail (G_IS_DATAGRAM_BASED (datagram_based), 0);
iface = G_DATAGRAM_BASED_GET_IFACE (datagram_based);
g_assert (iface->condition_check != NULL);
out = iface->condition_check (datagram_based, condition);
/* Postconditions. G_IO_OUT and G_IO_HUP are mutually exclusive. G_IO_IN and
* G_IO_HUP are mutually exclusive. The return value must be a subset of
* (condition | G_IO_ERR | G_IO_HUP). */
g_return_val_if_fail ((out & (G_IO_OUT | G_IO_HUP)) != (G_IO_OUT | G_IO_HUP),
out & ~G_IO_OUT);
g_return_val_if_fail ((out & (G_IO_IN | G_IO_HUP)) != (G_IO_IN | G_IO_HUP),
out & ~G_IO_IN);
g_return_val_if_fail ((out & ~(condition | G_IO_ERR | G_IO_HUP)) == 0,
out & (condition | G_IO_ERR | G_IO_HUP));
return out;
}
/**
* g_datagram_based_condition_wait:
* @datagram_based: a #GDatagramBased
* @condition: a #GIOCondition mask to wait for
* @timeout: the maximum time (in microseconds) to wait, 0 to not block, or -1
* to block indefinitely
* @cancellable: (nullable): a #GCancellable
* @error: return location for a #GError
*
* Waits for up to @timeout microseconds for condition to become true on
* @datagram_based. If the condition is met, %TRUE is returned.
*
* If @cancellable is cancelled before the condition is met, or if @timeout is
* reached before the condition is met, then %FALSE is returned and @error is
* set appropriately (%G_IO_ERROR_CANCELLED or %G_IO_ERROR_TIMED_OUT).
*
* Returns: %TRUE if the condition was met, %FALSE otherwise
*
* Since: 2.48
*/
gboolean
g_datagram_based_condition_wait (GDatagramBased *datagram_based,
GIOCondition condition,
gint64 timeout,
GCancellable *cancellable,
GError **error)
{
GDatagramBasedInterface *iface;
gboolean out;
GError *child_error = NULL;
g_return_val_if_fail (G_IS_DATAGRAM_BASED (datagram_based), FALSE);
g_return_val_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable),
FALSE);
g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
iface = G_DATAGRAM_BASED_GET_IFACE (datagram_based);
g_assert (iface->condition_wait != NULL);
out = iface->condition_wait (datagram_based, condition, timeout,
cancellable, &child_error);
/* Postconditions. */
g_return_val_if_fail (out == (child_error == NULL), FALSE);
if (child_error != NULL)
g_propagate_error (error, child_error);
return out;
}