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QUdpSocket: use faster ways to get datagram size on Linux and macOS

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With MSG_TRUNC on Linux, recv/recvfrom/recvmsg will return the full size
of the datagram, even if it won't fit the buffer you passed. On Darwin,
we have a getsockopt() option to get that value.

Change-Id: I6e9274c1e7444ad48c81fffd14da7d5b93815f90
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
This commit is contained in:
Thiago Macieira 2017-08-13 12:07:37 -07:00
parent 5de734bc18
commit 23d52de321
1 changed files with 15 additions and 2 deletions
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17
src/network/socket/qnativesocketengine_unix.cpp
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@ -834,7 +834,7 @@ bool QNativeSocketEnginePrivate::nativeHasPendingDatagrams() const
QT_SOCKLEN_T storageSize = sizeof(storage);
memset(&storage, 0, storageSize);
// Peek 0 bytes into the next message. The size of the message may
// Peek 1 bytes into the next message. The size of the message may
// well be 0, so we can't check recvfrom's return value.
ssize_t readBytes;
do {
@ -855,8 +855,20 @@ bool QNativeSocketEnginePrivate::nativeHasPendingDatagrams() const
qint64 QNativeSocketEnginePrivate::nativePendingDatagramSize() const
{
QVarLengthArray<char, 8192> udpMessagePeekBuffer(8192);
ssize_t recvResult = -1;
#ifdef Q_OS_LINUX
// Linux can return the actual datagram size if we use MSG_TRUNC
char c;
EINTR_LOOP(recvResult, ::recv(socketDescriptor, &c, 1, MSG_PEEK | MSG_TRUNC));
#elif defined(SO_NREAD)
// macOS can return the actual datagram size if we use SO_NREAD
int value;
socklen_t valuelen = sizeof(value);
recvResult = getsockopt(socketDescriptor, SOL_SOCKET, SO_NREAD, &value, &valuelen);
if (recvResult != -1)
recvResult = value;
#else
QVarLengthArray<char, 8192> udpMessagePeekBuffer(8192);
for (;;) {
// the data written to udpMessagePeekBuffer is discarded, so
@ -872,6 +884,7 @@ qint64 QNativeSocketEnginePrivate::nativePendingDatagramSize() const
udpMessagePeekBuffer.resize(udpMessagePeekBuffer.size() * 2);
}
#endif
#if defined (QNATIVESOCKETENGINE_DEBUG)
qDebug("QNativeSocketEnginePrivate::nativePendingDatagramSize() == %zd", recvResult);