QUrl: use QHashCombine so we use the faster & stronger QString hashing

We were only using the seed for hashing the port number, which is the
weakest of all the uses of the seed, resulting in a weak hash for the
QUrl itself. This commit changes it so QString components of the URL are
themselves also hashed using the seed. As a side benefit, the aeshash()
implementation in qhash.cpp where supported (ARM and x86) is faster than
the siphash() one because it's vectorized.

We're retaining the qHash(QUrl(), seed) == hashing of -1, but it's not
qHash(-1, seed) because QHashCombine adds a constant.

Pick-to: 6.10
Change-Id: If6466d054fd5a4f05205fffdfbc7b655eae5aefb
Reviewed-by: David Faure <[email protected]>

2 files changed, 26 insertions, 10 deletions

diff --git a/src/corelib/io/qurl.cpp b/src/corelib/io/qurl.cpp
index 565ce04c6ce..a4fbf69da8b 100644
--- a/src/corelib/io/qurl.cpp
+++ b/src/corelib/io/qurl.cpp
@@ -3660,17 +3660,29 @@ QList<QUrl> QUrl::fromStringList(const QStringList &urls, ParsingMode mode)
 */
 size_t qHash(const QUrl &url, size_t seed) noexcept
 {
+    QtPrivate::QHashCombineWithSeed hasher(seed);
+
+    // non-commutative, we must hash the port first
     if (!url.d)
-        return qHash(-1, seed); // the hash of an unset port (-1)
-
-    return qHash(url.d->scheme) ^
-            qHash(url.d->userName) ^
-            qHash(url.d->password) ^
-            qHash(url.d->host) ^
-            qHash(url.d->port, seed) ^
-            qHash(url.d->path) ^
-            qHash(url.d->query) ^
-            qHash(url.d->fragment);
+        return hasher(0, -1);
+    size_t state = hasher(0, url.d->port);
+
+    if (url.d->hasScheme())
+        state = hasher(state, url.d->scheme);
+    if (url.d->hasUserInfo()) {
+        // see presentSections(), appendUserName(), etc.
+        state = hasher(state, url.d->userName);
+        state = hasher(state, url.d->password);
+    }
+    if (url.d->hasHost() || url.d->isLocalFile())   // for XDG compatibility
+        state = hasher(state, url.d->host);
+    if (url.d->hasPath())
+        state = hasher(state, url.d->path);
+    if (url.d->hasQuery())
+        state = hasher(state, url.d->query);
+    if (url.d->hasFragment())
+        state = hasher(state, url.d->fragment);
+    return state;
 }
 
 static QUrl adjustFtpPath(QUrl url)
diff --git a/tests/auto/corelib/io/qurl/tst_qurl.cpp b/tests/auto/corelib/io/qurl/tst_qurl.cpp
index 282c7f2e360..71389abc976 100644
--- a/tests/auto/corelib/io/qurl/tst_qurl.cpp
+++ b/tests/auto/corelib/io/qurl/tst_qurl.cpp
@@ -513,6 +513,7 @@ void tst_QUrl::comparison2()
         QCOMPARE(url1.toString(), url2.toString());
         QCOMPARE(url1, url2);
         QCOMPARE(qHash(url1), qHash(url2));
+        QCOMPARE(qHash(url1, 1), qHash(url2, 1));
     } else if (ordering < 0) {
         QCOMPARE_LT(url1.toString(), url2.toString());
         QCOMPARE_NE(url1, url2);
@@ -1387,12 +1388,14 @@ void tst_QUrl::toString_constructed()
         QUrl parsed(asString);
         QCOMPARE(url, parsed);
         QCOMPARE(qHash(url), qHash(parsed));
+        QCOMPARE(qHash(url, 1), qHash(parsed, 1));
     }
 
     // clear it and ensure no memory of the previous state remains
     url.setUrl(QString());
     QCOMPARE(url, QUrl());
     QCOMPARE(qHash(url), qHash(QUrl()));
+    QCOMPARE(qHash(url, 1), qHash(QUrl(), 1));
 }
 
 void tst_QUrl::toDisplayString_PreferLocalFile_data()
@@ -4265,6 +4268,7 @@ void tst_QUrl::setComponents()
         QUrl recreated(toString);
         QCOMPARE(copy, recreated);
         QCOMPARE(qHash(copy), qHash(recreated));
+        QCOMPARE(qHash(copy, 1), qHash(recreated, 1));
     } else {
         QVERIFY(copy.toString().isEmpty());
     }