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![Leonardo Bras](/assets/img/avatar_default.png)
Add flags to io_writev and introduce io_flush as optional callback to QIOChannelClass, allowing the implementation of zero copy writes by subclasses. How to use them: - Write data using qio_channel_writev*(...,QIO_CHANNEL_WRITE_FLAG_ZERO_COPY), - Wait write completion with qio_channel_flush(). Notes: As some zero copy write implementations work asynchronously, it's recommended to keep the write buffer untouched until the return of qio_channel_flush(), to avoid the risk of sending an updated buffer instead of the buffer state during write. As io_flush callback is optional, if a subclass does not implement it, then: - io_flush will return 0 without changing anything. Also, some functions like qio_channel_writev_full_all() were adapted to receive a flag parameter. That allows shared code between zero copy and non-zero copy writev, and also an easier implementation on new flags. Signed-off-by: Leonardo Bras <leobras@redhat.com> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Reviewed-by: Peter Xu <peterx@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Message-Id: <20220513062836.965425-3-leobras@redhat.com> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
253 lines
7 KiB
C
253 lines
7 KiB
C
/*
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* QEMU I/O channels memory buffer driver
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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 2.1 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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#include "qemu/osdep.h"
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#include "io/channel-buffer.h"
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#include "io/channel-watch.h"
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#include "qemu/module.h"
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#include "qemu/sockets.h"
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#include "trace.h"
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QIOChannelBuffer *
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qio_channel_buffer_new(size_t capacity)
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{
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QIOChannelBuffer *ioc;
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ioc = QIO_CHANNEL_BUFFER(object_new(TYPE_QIO_CHANNEL_BUFFER));
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if (capacity) {
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ioc->data = g_new0(uint8_t, capacity);
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ioc->capacity = capacity;
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}
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return ioc;
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}
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static void qio_channel_buffer_finalize(Object *obj)
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{
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QIOChannelBuffer *ioc = QIO_CHANNEL_BUFFER(obj);
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g_free(ioc->data);
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ioc->capacity = ioc->usage = ioc->offset = 0;
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}
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static ssize_t qio_channel_buffer_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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{
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QIOChannelBuffer *bioc = QIO_CHANNEL_BUFFER(ioc);
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ssize_t ret = 0;
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size_t i;
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for (i = 0; i < niov; i++) {
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size_t want = iov[i].iov_len;
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if (bioc->offset >= bioc->usage) {
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break;
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}
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if ((bioc->offset + want) > bioc->usage) {
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want = bioc->usage - bioc->offset;
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}
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memcpy(iov[i].iov_base, bioc->data + bioc->offset, want);
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ret += want;
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bioc->offset += want;
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}
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return ret;
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}
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static ssize_t qio_channel_buffer_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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int flags,
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Error **errp)
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{
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QIOChannelBuffer *bioc = QIO_CHANNEL_BUFFER(ioc);
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ssize_t ret = 0;
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size_t i;
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size_t towrite = 0;
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for (i = 0; i < niov; i++) {
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towrite += iov[i].iov_len;
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}
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if ((bioc->offset + towrite) > bioc->capacity) {
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bioc->capacity = bioc->offset + towrite;
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bioc->data = g_realloc(bioc->data, bioc->capacity);
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}
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if (bioc->offset > bioc->usage) {
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memset(bioc->data, 0, bioc->offset - bioc->usage);
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bioc->usage = bioc->offset;
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}
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for (i = 0; i < niov; i++) {
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memcpy(bioc->data + bioc->usage,
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iov[i].iov_base,
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iov[i].iov_len);
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bioc->usage += iov[i].iov_len;
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bioc->offset += iov[i].iov_len;
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ret += iov[i].iov_len;
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}
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return ret;
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}
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static int qio_channel_buffer_set_blocking(QIOChannel *ioc G_GNUC_UNUSED,
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bool enabled G_GNUC_UNUSED,
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Error **errp G_GNUC_UNUSED)
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{
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return 0;
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}
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static off_t qio_channel_buffer_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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QIOChannelBuffer *bioc = QIO_CHANNEL_BUFFER(ioc);
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bioc->offset = offset;
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return offset;
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}
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static int qio_channel_buffer_close(QIOChannel *ioc,
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Error **errp)
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{
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QIOChannelBuffer *bioc = QIO_CHANNEL_BUFFER(ioc);
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g_free(bioc->data);
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bioc->data = NULL;
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bioc->capacity = bioc->usage = bioc->offset = 0;
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return 0;
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}
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typedef struct QIOChannelBufferSource QIOChannelBufferSource;
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struct QIOChannelBufferSource {
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GSource parent;
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QIOChannelBuffer *bioc;
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GIOCondition condition;
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};
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static gboolean
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qio_channel_buffer_source_prepare(GSource *source,
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gint *timeout)
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{
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QIOChannelBufferSource *bsource = (QIOChannelBufferSource *)source;
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*timeout = -1;
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return (G_IO_IN | G_IO_OUT) & bsource->condition;
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}
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static gboolean
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qio_channel_buffer_source_check(GSource *source)
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{
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QIOChannelBufferSource *bsource = (QIOChannelBufferSource *)source;
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return (G_IO_IN | G_IO_OUT) & bsource->condition;
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}
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static gboolean
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qio_channel_buffer_source_dispatch(GSource *source,
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GSourceFunc callback,
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gpointer user_data)
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{
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QIOChannelFunc func = (QIOChannelFunc)callback;
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QIOChannelBufferSource *bsource = (QIOChannelBufferSource *)source;
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return (*func)(QIO_CHANNEL(bsource->bioc),
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((G_IO_IN | G_IO_OUT) & bsource->condition),
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user_data);
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}
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static void
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qio_channel_buffer_source_finalize(GSource *source)
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{
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QIOChannelBufferSource *ssource = (QIOChannelBufferSource *)source;
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object_unref(OBJECT(ssource->bioc));
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}
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GSourceFuncs qio_channel_buffer_source_funcs = {
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qio_channel_buffer_source_prepare,
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qio_channel_buffer_source_check,
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qio_channel_buffer_source_dispatch,
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qio_channel_buffer_source_finalize
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};
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static GSource *qio_channel_buffer_create_watch(QIOChannel *ioc,
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GIOCondition condition)
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{
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QIOChannelBuffer *bioc = QIO_CHANNEL_BUFFER(ioc);
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QIOChannelBufferSource *ssource;
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GSource *source;
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source = g_source_new(&qio_channel_buffer_source_funcs,
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sizeof(QIOChannelBufferSource));
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ssource = (QIOChannelBufferSource *)source;
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ssource->bioc = bioc;
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object_ref(OBJECT(bioc));
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ssource->condition = condition;
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return source;
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}
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static void qio_channel_buffer_class_init(ObjectClass *klass,
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void *class_data G_GNUC_UNUSED)
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{
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QIOChannelClass *ioc_klass = QIO_CHANNEL_CLASS(klass);
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ioc_klass->io_writev = qio_channel_buffer_writev;
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ioc_klass->io_readv = qio_channel_buffer_readv;
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ioc_klass->io_set_blocking = qio_channel_buffer_set_blocking;
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ioc_klass->io_seek = qio_channel_buffer_seek;
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ioc_klass->io_close = qio_channel_buffer_close;
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ioc_klass->io_create_watch = qio_channel_buffer_create_watch;
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}
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static const TypeInfo qio_channel_buffer_info = {
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.parent = TYPE_QIO_CHANNEL,
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.name = TYPE_QIO_CHANNEL_BUFFER,
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.instance_size = sizeof(QIOChannelBuffer),
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.instance_finalize = qio_channel_buffer_finalize,
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.class_init = qio_channel_buffer_class_init,
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};
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static void qio_channel_buffer_register_types(void)
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{
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type_register_static(&qio_channel_buffer_info);
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}
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type_init(qio_channel_buffer_register_types);
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