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39
40 #include "qv4compilationunitmapper_p.h"
41
42 #include <sys/mman.h>
43 #include <functional>
44 #include <private/qcore_unix_p.h>
45 #include <QScopeGuard>
46 #include <QDateTime>
47
48 #include "qv4executablecompilationunit_p.h"
49
50 QT_BEGIN_NAMESPACE
51
52 using namespace QV4;
53
open(const QString & cacheFileName,const QDateTime & sourceTimeStamp,QString * errorString)54 CompiledData::Unit *CompilationUnitMapper::open(const QString &cacheFileName, const QDateTime &sourceTimeStamp, QString *errorString)
55 {
56 close();
57
58 int fd = qt_safe_open(QFile::encodeName(cacheFileName).constData(), O_RDONLY);
59 if (fd == -1) {
60 *errorString = qt_error_string(errno);
61 return nullptr;
62 }
63
64 auto cleanup = qScopeGuard([fd]{
65 qt_safe_close(fd) ;
66 });
67
68 CompiledData::Unit header;
69 qint64 bytesRead = qt_safe_read(fd, reinterpret_cast<char *>(&header), sizeof(header));
70
71 if (bytesRead != sizeof(header)) {
72 *errorString = QStringLiteral("File too small for the header fields");
73 return nullptr;
74 }
75
76 if (!ExecutableCompilationUnit::verifyHeader(&header, sourceTimeStamp, errorString))
77 return nullptr;
78
79 // Data structure and qt version matched, so now we can access the rest of the file safely.
80
81 length = static_cast<size_t>(lseek(fd, 0, SEEK_END));
82
83 void *ptr = mmap(nullptr, length, PROT_READ, MAP_SHARED, fd, /*offset*/0);
84 if (ptr == MAP_FAILED) {
85 *errorString = qt_error_string(errno);
86 return nullptr;
87 }
88 dataPtr = ptr;
89
90 return reinterpret_cast<CompiledData::Unit*>(dataPtr);
91 }
92
close()93 void CompilationUnitMapper::close()
94 {
95 // Do not unmap the data here.
96 if (dataPtr != nullptr) {
97 // Do not unmap cache files that are built with the StaticData flag. That's the majority of
98 // them and it's necessary to benefit from the QString literal optimization. There might
99 // still be QString instances around that point into that memory area. The memory is backed
100 // on the disk, so the kernel is free to release the pages and all that remains is the
101 // address space allocation.
102 if (!(reinterpret_cast<CompiledData::Unit*>(dataPtr)->flags & CompiledData::Unit::StaticData))
103 munmap(dataPtr, length);
104 }
105 dataPtr = nullptr;
106 }
107
108 QT_END_NAMESPACE
109