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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#include "qv4compilationunitmapper_p.h"
#include <private/qcore_unix_p.h>
#include <private/qv4compileddata_p.h>
#include <QtCore/qscopeguard.h>
#include <QtCore/qdatetime.h>
#include <functional>
#include <sys/mman.h>
QT_BEGIN_NAMESPACE
using namespace QV4;
CompiledData::Unit *CompilationUnitMapper::open(const QString &cacheFileName, const QDateTime &sourceTimeStamp, QString *errorString)
{
close();
int fd = qt_safe_open(QFile::encodeName(cacheFileName).constData(), O_RDONLY);
if (fd == -1) {
*errorString = qt_error_string(errno);
return nullptr;
}
auto cleanup = qScopeGuard([fd]{
qt_safe_close(fd) ;
});
CompiledData::Unit header;
qint64 bytesRead = qt_safe_read(fd, reinterpret_cast<char *>(&header), sizeof(header));
if (bytesRead != sizeof(header)) {
*errorString = QStringLiteral("File too small for the header fields");
return nullptr;
}
if (!header.verifyHeader(sourceTimeStamp, errorString))
return nullptr;
// Data structure and qt version matched, so now we can access the rest of the file safely.
length = static_cast<size_t>(lseek(fd, 0, SEEK_END));
/* Error out early on file corruption. We assume we can read header.unitSize bytes
later (even before verifying the checksum), potentially causing out-of-bound
reads
Also, no need to wait until checksum verification if we know beforehand
that the cached unit is bogus
*/
if (length != header.unitSize) {
*errorString = QStringLiteral("Potential file corruption, file too small");
return nullptr;
}
void *ptr = mmap(nullptr, length, PROT_READ, MAP_SHARED, fd, /*offset*/0);
if (ptr == MAP_FAILED) {
*errorString = qt_error_string(errno);
return nullptr;
}
dataPtr = ptr;
return reinterpret_cast<CompiledData::Unit*>(dataPtr);
}
void CompilationUnitMapper::close()
{
// Do not unmap the data here.
if (dataPtr != nullptr) {
// Do not unmap cache files that are built with the StaticData flag. That's the majority of
// them and it's necessary to benefit from the QString literal optimization. There might
// still be QString instances around that point into that memory area. The memory is backed
// on the disk, so the kernel is free to release the pages and all that remains is the
// address space allocation.
if (!(reinterpret_cast<CompiledData::Unit*>(dataPtr)->flags & CompiledData::Unit::StaticData))
munmap(dataPtr, length);
}
dataPtr = nullptr;
}
QT_END_NAMESPACE
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