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CBOR: implement faster comparison for equality in strings

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If we don't need to sort, then we can use QtPrivate::equalStrings() to
get a few cycles of performance per string comparison.

Change-Id: I5f663c2f9f4149af84fefffd17c03d9b52ca696e
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
This commit is contained in:
Thiago Macieira 2024-03-25 23:46:35 -07:00
parent edc2d41456
commit 8e5ce9cd36
2 changed files with 19 additions and 6 deletions
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19
src/corelib/serialization/qcborvalue.cpp
View File

@ -1156,6 +1156,12 @@ static int compareElementRecursive(const QCborContainerPrivate *c1, const Elemen
const ByteData *b1 = c1 ? c1->byteData(e1) : nullptr;
const ByteData *b2 = c2 ? c2->byteData(e2) : nullptr;
if (b1 || b2) {
auto compareStrings = [mode](auto s1, auto s2) {
if (mode == Comparison::ForEquality)
return QtPrivate::equalStrings(s1, s2) ? 0 : 1;
return QtPrivate::compareStrings(s1, s2);
};
auto len1 = b1 ? b1->len : 0;
auto len2 = b2 ? b2->len : 0;
@ -1184,15 +1190,20 @@ static int compareElementRecursive(const QCborContainerPrivate *c1, const Elemen
// Case 1: both UTF-16, so lengths are comparable.
// (we can't use memcmp in little-endian machines)
if (len1 == len2)
return QtPrivate::compareStrings(b1->asStringView(), b2->asStringView());
return compareStrings(b1->asStringView(), b2->asStringView());
return len1 < len2 ? -1 : 1;
}
if (!(e1.flags & Element::StringIsUtf16) && !(e2.flags & Element::StringIsUtf16)) {
// Cases 4, 5 and 6: neither is UTF-16, so lengths are comparable too
// (this case includes byte arrays too)
if (len1 == len2)
if (len1 == len2) {
if (mode == Comparison::ForEquality) {
// GCC optimizes this to __memcmpeq(); Clang to bcmp()
return memcmp(b1->byte(), b2->byte(), size_t(len1)) == 0 ? 0 : 1;
}
return memcmp(b1->byte(), b2->byte(), size_t(len1));
}
return len1 < len2 ? -1 : 1;
}
@ -1217,8 +1228,8 @@ static int compareElementRecursive(const QCborContainerPrivate *c1, const Elemen
if (len1 != len2)
return len1 < len2 ? -1 : 1;
if (e1.flags & Element::StringIsUtf16)
return QtPrivate::compareStrings(b1->asStringView(), b2->asLatin1());
return QtPrivate::compareStrings(b1->asLatin1(), b2->asStringView());
return compareStrings(b1->asStringView(), b2->asLatin1());
return compareStrings(b1->asLatin1(), b2->asStringView());
}
return compareElementNoData(e1, e2);

6
src/corelib/serialization/qcborvalue_p.h
View File

@ -360,9 +360,11 @@ public:
if (!b)
return s.isEmpty() ? 0 : -1;
Q_UNUSED(mode);
if (e.flags & QtCbor::Element::StringIsUtf16)
if (e.flags & QtCbor::Element::StringIsUtf16) {
if (mode == QtCbor::Comparison::ForEquality)
return QtPrivate::equalStrings(b->asStringView(), s) ? 0 : 1;
return QtPrivate::compareStrings(b->asStringView(), s);
}
return compareUtf8(b, s);
}