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QIODevice: allow subclasses to enforce unbuffered mode

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For subclasses that implement alternative buffering (such as
QLocalSocket), it would be useful to bypass the QIODevice's internal
buffer, even if the QIODeviceBase::Unbuffered flag is not set when
opened.

By setting the readBufferChunkSize member to 0 in their constructors,
these classes now unconditionally switch the base class to unbuffered
mode, while still reporting buffering with openMode() function.

Change-Id: I351bc57ac0ccb45c81f8c6be15f1745131aa26ba
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
This commit is contained in:
Alex Trotsenko 2021-07-21 14:44:13 +03:00
parent 69c833dae9
commit 3bc976c2bd
1 changed files with 16 additions and 9 deletions
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25
src/corelib/io/qiodevice.cpp
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@ -703,8 +703,15 @@ void QIODevice::setCurrentReadChannel(int channel)
void QIODevicePrivate::setReadChannelCount(int count) void QIODevicePrivate::setReadChannelCount(int count)
{ {
if (count > readBuffers.size()) { if (count > readBuffers.size()) {
// If readBufferChunkSize is zero, we should bypass QIODevice's
// read buffers, even if the QIODeviceBase::Unbuffered flag is not
// set when opened. However, if a read transaction is started or
// ungetChar() is called, we still have to use the internal buffer.
// To support these cases, pass a default value to the QRingBuffer
// constructor.
readBuffers.insert(readBuffers.end(), count - readBuffers.size(), readBuffers.insert(readBuffers.end(), count - readBuffers.size(),
QRingBuffer(readBufferChunkSize)); QRingBuffer(readBufferChunkSize != 0 ? readBufferChunkSize
: QIODEVICE_BUFFERSIZE));
} else { } else {
readBuffers.resize(count); readBuffers.resize(count);
} }
@ -1068,7 +1075,7 @@ qint64 QIODevicePrivate::read(char *data, qint64 maxSize, bool peeking)
{ {
Q_Q(QIODevice); Q_Q(QIODevice);
const bool buffered = (openMode & QIODevice::Unbuffered) == 0; const bool buffered = (readBufferChunkSize != 0 && (openMode & QIODevice::Unbuffered) == 0);
const bool sequential = isSequential(); const bool sequential = isSequential();
const bool keepDataInBuffer = sequential const bool keepDataInBuffer = sequential
? peeking || transactionStarted ? peeking || transactionStarted
@ -1121,9 +1128,9 @@ qint64 QIODevicePrivate::read(char *data, qint64 maxSize, bool peeking)
} }
} else { } else {
// Do not read more than maxSize on unbuffered devices // Do not read more than maxSize on unbuffered devices
const qint64 bytesToBuffer = (buffered || readBufferChunkSize < maxSize) const qint64 bytesToBuffer = (!buffered && maxSize < buffer.chunkSize())
? qint64(readBufferChunkSize) ? maxSize
: maxSize; : qint64(buffer.chunkSize());
// Try to fill QIODevice buffer by single read // Try to fill QIODevice buffer by single read
readFromDevice = q->readData(buffer.reserve(bytesToBuffer), bytesToBuffer); readFromDevice = q->readData(buffer.reserve(bytesToBuffer), bytesToBuffer);
deviceAtEof = (readFromDevice != bytesToBuffer); deviceAtEof = (readFromDevice != bytesToBuffer);
@ -1266,7 +1273,7 @@ QByteArray QIODevice::readAll()
qint64 readBytes = (d->isSequential() ? Q_INT64_C(0) : size()); qint64 readBytes = (d->isSequential() ? Q_INT64_C(0) : size());
if (readBytes == 0) { if (readBytes == 0) {
// Size is unknown, read incrementally. // Size is unknown, read incrementally.
qint64 readChunkSize = qMax(qint64(d->readBufferChunkSize), qint64 readChunkSize = qMax(qint64(d->buffer.chunkSize()),
d->isSequential() ? (d->buffer.size() - d->transactionPos) d->isSequential() ? (d->buffer.size() - d->transactionPos)
: d->buffer.size()); : d->buffer.size());
qint64 readResult; qint64 readResult;
@ -1279,7 +1286,7 @@ QByteArray QIODevice::readAll()
readResult = d->read(result.data() + readBytes, readChunkSize); readResult = d->read(result.data() + readBytes, readChunkSize);
if (readResult > 0 || readBytes == 0) { if (readResult > 0 || readBytes == 0) {
readBytes += readResult; readBytes += readResult;
readChunkSize = d->readBufferChunkSize; readChunkSize = d->buffer.chunkSize();
} }
} while (readResult > 0); } while (readResult > 0);
} else { } else {
@ -1485,11 +1492,11 @@ QByteArray QIODevice::readLine(qint64 maxSize)
qint64 readResult; qint64 readResult;
do { do {
result.resize(int(qMin(maxSize, qint64(result.size() + d->readBufferChunkSize)))); result.resize(int(qMin(maxSize, qint64(result.size() + d->buffer.chunkSize()))));
readResult = d->readLine(result.data() + readBytes, result.size() - readBytes); readResult = d->readLine(result.data() + readBytes, result.size() - readBytes);
if (readResult > 0 || readBytes == 0) if (readResult > 0 || readBytes == 0)
readBytes += readResult; readBytes += readResult;
} while (readResult == d->readBufferChunkSize } while (readResult == d->buffer.chunkSize()
&& result[int(readBytes - 1)] != '\n'); && result[int(readBytes - 1)] != '\n');
} else { } else {
CHECK_LINEMAXLEN(readLine, result); CHECK_LINEMAXLEN(readLine, result);