503 lines
16 KiB
C
503 lines
16 KiB
C
/*
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* QEMU I/O channels
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*
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* Copyright (c) 2015 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#ifndef QIO_CHANNEL_H__
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#define QIO_CHANNEL_H__
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#include "qemu-common.h"
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#include "qapi/error.h"
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#include "qom/object.h"
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#define TYPE_QIO_CHANNEL "qio-channel"
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#define QIO_CHANNEL(obj) \
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OBJECT_CHECK(QIOChannel, (obj), TYPE_QIO_CHANNEL)
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#define QIO_CHANNEL_CLASS(klass) \
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OBJECT_CLASS_CHECK(QIOChannelClass, klass, TYPE_QIO_CHANNEL)
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#define QIO_CHANNEL_GET_CLASS(obj) \
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OBJECT_GET_CLASS(QIOChannelClass, obj, TYPE_QIO_CHANNEL)
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typedef struct QIOChannel QIOChannel;
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typedef struct QIOChannelClass QIOChannelClass;
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#define QIO_CHANNEL_ERR_BLOCK -2
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typedef enum QIOChannelFeature QIOChannelFeature;
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enum QIOChannelFeature {
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QIO_CHANNEL_FEATURE_FD_PASS = (1 << 0),
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QIO_CHANNEL_FEATURE_SHUTDOWN = (1 << 1),
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};
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typedef enum QIOChannelShutdown QIOChannelShutdown;
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enum QIOChannelShutdown {
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QIO_CHANNEL_SHUTDOWN_BOTH,
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QIO_CHANNEL_SHUTDOWN_READ,
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QIO_CHANNEL_SHUTDOWN_WRITE,
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};
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typedef gboolean (*QIOChannelFunc)(QIOChannel *ioc,
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GIOCondition condition,
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gpointer data);
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/**
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* QIOChannel:
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*
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* The QIOChannel defines the core API for a generic I/O channel
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* class hierarchy. It is inspired by GIOChannel, but has the
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* following differences
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*
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* - Use QOM to properly support arbitrary subclassing
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* - Support use of iovecs for efficient I/O with multiple blocks
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* - None of the character set translation, binary data exclusively
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* - Direct support for QEMU Error object reporting
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* - File descriptor passing
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*
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* This base class is abstract so cannot be instantiated. There
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* will be subclasses for dealing with sockets, files, and higher
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* level protocols such as TLS, WebSocket, etc.
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*/
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struct QIOChannel {
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Object parent;
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unsigned int features; /* bitmask of QIOChannelFeatures */
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};
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/**
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* QIOChannelClass:
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*
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* This class defines the contract that all subclasses
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* must follow to provide specific channel implementations.
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* The first five callbacks are mandatory to support, others
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* provide additional optional features.
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*
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* Consult the corresponding public API docs for a description
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* of the semantics of each callback
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*/
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struct QIOChannelClass {
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ObjectClass parent;
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/* Mandatory callbacks */
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ssize_t (*io_writev)(QIOChannel *ioc,
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const struct iovec *iov,
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size_t niov,
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int *fds,
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size_t nfds,
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Error **errp);
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ssize_t (*io_readv)(QIOChannel *ioc,
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const struct iovec *iov,
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size_t niov,
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int **fds,
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size_t *nfds,
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Error **errp);
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int (*io_close)(QIOChannel *ioc,
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Error **errp);
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GSource * (*io_create_watch)(QIOChannel *ioc,
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GIOCondition condition);
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int (*io_set_blocking)(QIOChannel *ioc,
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bool enabled,
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Error **errp);
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/* Optional callbacks */
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int (*io_shutdown)(QIOChannel *ioc,
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QIOChannelShutdown how,
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Error **errp);
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void (*io_set_cork)(QIOChannel *ioc,
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bool enabled);
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void (*io_set_delay)(QIOChannel *ioc,
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bool enabled);
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off_t (*io_seek)(QIOChannel *ioc,
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off_t offset,
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int whence,
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Error **errp);
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};
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/* General I/O handling functions */
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/**
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* qio_channel_has_feature:
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* @ioc: the channel object
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* @feature: the feature to check support of
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*
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* Determine whether the channel implementation supports
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* the optional feature named in @feature.
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*
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* Returns: true if supported, false otherwise.
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*/
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bool qio_channel_has_feature(QIOChannel *ioc,
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QIOChannelFeature feature);
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/**
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* qio_channel_readv_full:
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* @ioc: the channel object
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* @iov: the array of memory regions to read data into
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* @niov: the length of the @iov array
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* @fds: pointer to an array that will received file handles
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* @nfds: pointer filled with number of elements in @fds on return
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* @errp: pointer to a NULL-initialized error object
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*
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* Read data from the IO channel, storing it in the
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* memory regions referenced by @iov. Each element
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* in the @iov will be fully populated with data
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* before the next one is used. The @niov parameter
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* specifies the total number of elements in @iov.
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*
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* It is not required for all @iov to be filled with
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* data. If the channel is in blocking mode, at least
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* one byte of data will be read, but no more is
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* guaranteed. If the channel is non-blocking and no
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* data is available, it will return QIO_CHANNEL_ERR_BLOCK
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*
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* If the channel has passed any file descriptors,
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* the @fds array pointer will be allocated and
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* the elements filled with the received file
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* descriptors. The @nfds pointer will be updated
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* to indicate the size of the @fds array that
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* was allocated. It is the callers responsibility
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* to call close() on each file descriptor and to
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* call g_free() on the array pointer in @fds.
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*
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* It is an error to pass a non-NULL @fds parameter
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* unless qio_channel_has_feature() returns a true
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* value for the QIO_CHANNEL_FEATURE_FD_PASS constant.
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*
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* Returns: the number of bytes read, or -1 on error,
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* or QIO_CHANNEL_ERR_BLOCK if no data is available
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* and the channel is non-blocking
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*/
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ssize_t qio_channel_readv_full(QIOChannel *ioc,
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const struct iovec *iov,
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size_t niov,
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int **fds,
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size_t *nfds,
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Error **errp);
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/**
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* qio_channel_writev_full:
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* @ioc: the channel object
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* @iov: the array of memory regions to write data from
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* @niov: the length of the @iov array
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* @fds: an array of file handles to send
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* @nfds: number of file handles in @fds
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* @errp: pointer to a NULL-initialized error object
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*
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* Write data to the IO channel, reading it from the
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* memory regions referenced by @iov. Each element
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* in the @iov will be fully sent, before the next
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* one is used. The @niov parameter specifies the
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* total number of elements in @iov.
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*
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* It is not required for all @iov data to be fully
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* sent. If the channel is in blocking mode, at least
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* one byte of data will be sent, but no more is
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* guaranteed. If the channel is non-blocking and no
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* data can be sent, it will return QIO_CHANNEL_ERR_BLOCK
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*
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* If there are file descriptors to send, the @fds
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* array should be non-NULL and provide the handles.
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* All file descriptors will be sent if at least one
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* byte of data was sent.
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*
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* It is an error to pass a non-NULL @fds parameter
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* unless qio_channel_has_feature() returns a true
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* value for the QIO_CHANNEL_FEATURE_FD_PASS constant.
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*
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* Returns: the number of bytes sent, or -1 on error,
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* or QIO_CHANNEL_ERR_BLOCK if no data is can be sent
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* and the channel is non-blocking
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*/
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ssize_t qio_channel_writev_full(QIOChannel *ioc,
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const struct iovec *iov,
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size_t niov,
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int *fds,
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size_t nfds,
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Error **errp);
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/**
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* qio_channel_readv:
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* @ioc: the channel object
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* @iov: the array of memory regions to read data into
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* @niov: the length of the @iov array
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* @errp: pointer to a NULL-initialized error object
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*
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* Behaves as qio_channel_readv_full() but does not support
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* receiving of file handles.
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*/
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ssize_t qio_channel_readv(QIOChannel *ioc,
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const struct iovec *iov,
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size_t niov,
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Error **errp);
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/**
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* qio_channel_writev:
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* @ioc: the channel object
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* @iov: the array of memory regions to write data from
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* @niov: the length of the @iov array
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* @errp: pointer to a NULL-initialized error object
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*
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* Behaves as qio_channel_writev_full() but does not support
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* sending of file handles.
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*/
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ssize_t qio_channel_writev(QIOChannel *ioc,
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const struct iovec *iov,
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size_t niov,
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Error **errp);
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/**
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* qio_channel_readv:
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* @ioc: the channel object
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* @buf: the memory region to read data into
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* @buflen: the length of @buf
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* @errp: pointer to a NULL-initialized error object
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*
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* Behaves as qio_channel_readv_full() but does not support
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* receiving of file handles, and only supports reading into
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* a single memory region.
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*/
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ssize_t qio_channel_read(QIOChannel *ioc,
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char *buf,
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size_t buflen,
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Error **errp);
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/**
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* qio_channel_writev:
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* @ioc: the channel object
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* @buf: the memory regions to send data from
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* @buflen: the length of @buf
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* @errp: pointer to a NULL-initialized error object
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*
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* Behaves as qio_channel_writev_full() but does not support
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* sending of file handles, and only supports writing from a
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* single memory region.
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*/
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ssize_t qio_channel_write(QIOChannel *ioc,
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const char *buf,
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size_t buflen,
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Error **errp);
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/**
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* qio_channel_set_blocking:
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* @ioc: the channel object
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* @enabled: the blocking flag state
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* @errp: pointer to a NULL-initialized error object
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*
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* If @enabled is true, then the channel is put into
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* blocking mode, otherwise it will be non-blocking.
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*
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* In non-blocking mode, read/write operations may
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* return QIO_CHANNEL_ERR_BLOCK if they would otherwise
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* block on I/O
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*/
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int qio_channel_set_blocking(QIOChannel *ioc,
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bool enabled,
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Error **errp);
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/**
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* qio_channel_close:
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* @ioc: the channel object
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* @errp: pointer to a NULL-initialized error object
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*
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* Close the channel, flushing any pending I/O
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*
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* Returns: 0 on success, -1 on error
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*/
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int qio_channel_close(QIOChannel *ioc,
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Error **errp);
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/**
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* qio_channel_shutdown:
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* @ioc: the channel object
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* @how: the direction to shutdown
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* @errp: pointer to a NULL-initialized error object
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*
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* Shutdowns transmission and/or receiving of data
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* without closing the underlying transport.
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*
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* Not all implementations will support this facility,
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* so may report an error. To avoid errors, the
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* caller may check for the feature flag
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* QIO_CHANNEL_FEATURE_SHUTDOWN prior to calling
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* this method.
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*
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* Returns: 0 on success, -1 on error
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*/
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int qio_channel_shutdown(QIOChannel *ioc,
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QIOChannelShutdown how,
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Error **errp);
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/**
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* qio_channel_set_delay:
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* @ioc: the channel object
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* @enabled: the new flag state
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*
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* Controls whether the underlying transport is
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* permitted to delay writes in order to merge
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* small packets. If @enabled is true, then the
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* writes may be delayed in order to opportunistically
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* merge small packets into larger ones. If @enabled
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* is false, writes are dispatched immediately with
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* no delay.
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*
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* When @enabled is false, applications may wish to
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* use the qio_channel_set_cork() method to explicitly
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* control write merging.
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*
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* On channels which are backed by a socket, this
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* API corresponds to the inverse of TCP_NODELAY flag,
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* controlling whether the Nagle algorithm is active.
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*
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* This setting is merely a hint, so implementations are
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* free to ignore this without it being considered an
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* error.
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*/
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void qio_channel_set_delay(QIOChannel *ioc,
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bool enabled);
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/**
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* qio_channel_set_cork:
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* @ioc: the channel object
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* @enabled: the new flag state
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*
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* Controls whether the underlying transport is
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* permitted to dispatch data that is written.
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* If @enabled is true, then any data written will
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* be queued in local buffers until @enabled is
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* set to false once again.
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*
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* This feature is typically used when the automatic
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* write coalescing facility is disabled via the
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* qio_channel_set_delay() method.
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*
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* On channels which are backed by a socket, this
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* API corresponds to the TCP_CORK flag.
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*
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* This setting is merely a hint, so implementations are
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* free to ignore this without it being considered an
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* error.
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*/
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void qio_channel_set_cork(QIOChannel *ioc,
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bool enabled);
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/**
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* qio_channel_seek:
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* @ioc: the channel object
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* @offset: the position to seek to, relative to @whence
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* @whence: one of the (POSIX) SEEK_* constants listed below
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* @errp: pointer to a NULL-initialized error object
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*
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* Moves the current I/O position within the channel
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* @ioc, to be @offset. The value of @offset is
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* interpreted relative to @whence:
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*
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* SEEK_SET - the position is set to @offset bytes
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* SEEK_CUR - the position is moved by @offset bytes
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* SEEK_END - the position is set to end of the file plus @offset bytes
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*
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* Not all implementations will support this facility,
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* so may report an error.
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*
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* Returns: the new position on success, (off_t)-1 on failure
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*/
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off_t qio_channel_io_seek(QIOChannel *ioc,
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off_t offset,
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int whence,
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Error **errp);
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/**
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* qio_channel_create_watch:
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* @ioc: the channel object
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* @condition: the I/O condition to monitor
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*
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* Create a new main loop source that is used to watch
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* for the I/O condition @condition. Typically the
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* qio_channel_add_watch() method would be used instead
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* of this, since it directly attaches a callback to
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* the source
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*
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* Returns: the new main loop source.
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*/
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GSource *qio_channel_create_watch(QIOChannel *ioc,
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GIOCondition condition);
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/**
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* qio_channel_add_watch:
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* @ioc: the channel object
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* @condition: the I/O condition to monitor
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* @func: callback to invoke when the source becomes ready
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* @user_data: opaque data to pass to @func
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* @notify: callback to free @user_data
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*
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* Create a new main loop source that is used to watch
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* for the I/O condition @condition. The callback @func
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* will be registered against the source, to be invoked
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* when the source becomes ready. The optional @user_data
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* will be passed to @func when it is invoked. The @notify
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* callback will be used to free @user_data when the
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* watch is deleted
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*
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* The returned source ID can be used with g_source_remove()
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* to remove and free the source when no longer required.
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* Alternatively the @func callback can return a FALSE
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* value.
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*
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* Returns: the source ID
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*/
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guint qio_channel_add_watch(QIOChannel *ioc,
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GIOCondition condition,
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QIOChannelFunc func,
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gpointer user_data,
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GDestroyNotify notify);
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/**
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* qio_channel_yield:
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* @ioc: the channel object
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* @condition: the I/O condition to wait for
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*
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* Yields execution from the current coroutine until
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* the condition indicated by @condition becomes
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* available.
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*
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* This must only be called from coroutine context
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*/
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void qio_channel_yield(QIOChannel *ioc,
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GIOCondition condition);
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/**
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* qio_channel_wait:
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* @ioc: the channel object
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* @condition: the I/O condition to wait for
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*
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* Block execution from the current thread until
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* the condition indicated by @condition becomes
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* available.
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*
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* This will enter a nested event loop to perform
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* the wait.
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*/
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void qio_channel_wait(QIOChannel *ioc,
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GIOCondition condition);
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#endif /* QIO_CHANNEL_H__ */
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