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QFsFileEngine: avoid triple(quadruple) lookup of the same key

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Instead of contains(), 1-2x operator[](), and remove(), equalling 3-4
separate lookups, use find() + erase(), which does just one
lookup.

Since our erase() function is C++11-compliant these days and takes
const_iterator instead of (mutable) iterator, we can use the const
find() overload to delay a detach (attempt) until we actually erase().

Change-Id: I8e67a48e221e548528049fa093ab7ef2f1802f7e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Marc Mutz 2021-08-02 14:00:12 +02:00
parent a46d0b480b
commit e933d71a61
2 changed files with 9 additions and 7 deletions
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9
src/corelib/io/qfsfileengine_unix.cpp
View File

@ -646,18 +646,19 @@ bool QFSFileEnginePrivate::unmap(uchar *ptr)
{
#if !defined(Q_OS_INTEGRITY)
Q_Q(QFSFileEngine);
if (!maps.contains(ptr)) {
const auto it = std::as_const(maps).find(ptr);
if (it == maps.cend()) {
q->setError(QFile::PermissionsError, qt_error_string(EACCES));
return false;
}
uchar *start = ptr - maps[ptr].first;
size_t len = maps[ptr].second;
uchar *start = ptr - it->first;
size_t len = it->second;
if (-1 == munmap(start, len)) {
q->setError(QFile::UnspecifiedError, qt_error_string(errno));
return false;
}
maps.remove(ptr);
maps.erase(it);
return true;
#else
return false;

7
src/corelib/io/qfsfileengine_win.cpp
View File

@ -871,17 +871,18 @@ uchar *QFSFileEnginePrivate::map(qint64 offset, qint64 size,
bool QFSFileEnginePrivate::unmap(uchar *ptr)
{
Q_Q(QFSFileEngine);
if (!maps.contains(ptr)) {
const auto it = std::as_const(maps).find(ptr);
if (it == maps.cend()) {
q->setError(QFile::PermissionsError, qt_error_string(ERROR_ACCESS_DENIED));
return false;
}
uchar *start = ptr - maps[ptr];
uchar *start = ptr - *it;
if (!UnmapViewOfFile(start)) {
q->setError(QFile::PermissionsError, qt_error_string());
return false;
}
maps.remove(ptr);
maps.erase(it);
if (maps.isEmpty()) {
::CloseHandle(mapHandle);
mapHandle = NULL;