Add a QHttpHeaders convenience method for unique header name setting

The function replaces one of the found entries with the new value,
and removes any other entries. If no entries are found, a new entry
will be appended. The replacement search is done for performance
reasons; it's cheaper to replace an existing value.

All in all the function is a more convenient and performant
alternative for this sequence (which proved to be common while
porting QtNetwork internals to QHttpHeaders):
header.removeAll(<headername>);
header.append(<headername>, <value>);

[ChangeLog][QtNetwork][QHttpHeaders] Added replaceOrAppend()
convenience method, which either replaces previous entries with
a single entry, or appends a new one if no entries existed

Fixes: QTBUG-122175
Change-Id: I03957645d7e916a732ac7b8d3ae724bb6b16af87
Reviewed-by: Lena Biliaieva <lena.biliaieva@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/network/access/qhttpheaders.cpp

@@ -789,6 +789,7 @@ public:
     // we can define common methods which 'detach()' the private itself.
     using Self = QExplicitlySharedDataPointer<QHttpHeadersPrivate>;
     static void removeAll(Self &d, const HeaderName &name);
+    static void replaceOrAppend(Self &d, const HeaderName &name, const QByteArray &value);
 
     void combinedValue(const HeaderName &name, QByteArray &result) const;
     void values(const HeaderName &name, QList<QByteArray> &result) const;
@@ -852,6 +853,23 @@ QByteArrayView QHttpHeadersPrivate::value(const HeaderName &name, QByteArrayView
     return defaultValue;
 }
 
+void QHttpHeadersPrivate::replaceOrAppend(Self &d, const HeaderName &name, const QByteArray &value)
+{
+    d.detach();
+    auto it = std::find_if(d->headers.begin(), d->headers.end(), headerNameMatches(name));
+    if (it != d->headers.end()) {
+        // Found something to replace => replace, and then rearrange any remaining
+        // matches to the end and erase them
+        it->value = value;
+        d->headers.erase(
+                std::remove_if(it + 1, d->headers.end(), headerNameMatches(name)),
+                d->headers.end());
+    } else {
+        // Found nothing to replace => append
+        d->headers.append(Header{name, value});
+    }
+}
+
 /*!
     Creates a new QHttpHeaders object.
 */
@@ -1216,6 +1234,47 @@ bool QHttpHeaders::replace(qsizetype i, WellKnownHeader name, QAnyStringView new
     return true;
 }
 
+/*!
+    \since 6.8
+
+    If QHttpHeaders already contains \a name, replaces its value with
+    \a newValue and removes possible additional \a name entries.
+    If \a name didn't exist, appends a new entry. Returns \c true
+    if successful.
+
+    This function is a convenience method for setting a unique
+    \a name : \a newValue header. For most headers the relative order does not
+    matter, which allows reusing an existing entry if one exists.
+
+    \sa replaceOrAppend(QAnyStringView, QAnyStringView)
+*/
+bool QHttpHeaders::replaceOrAppend(WellKnownHeader name, QAnyStringView newValue)
+{
+    if (isEmpty())
+        return append(name, newValue);
+
+    if (!isValidHttpHeaderValueField(newValue))
+        return false;
+
+    QHttpHeadersPrivate::replaceOrAppend(d, HeaderName{name}, normalizedValue(newValue));
+    return true;
+}
+
+/*!
+    \overload replaceOrAppend(WellKnownHeader, QAnyStringView)
+*/
+bool QHttpHeaders::replaceOrAppend(QAnyStringView name, QAnyStringView newValue)
+{
+    if (isEmpty())
+        return append(name, newValue);
+
+    if (!isValidHttpHeaderNameField(name) || !isValidHttpHeaderValueField(newValue))
+        return false;
+
+    QHttpHeadersPrivate::replaceOrAppend(d, HeaderName{name}, normalizedValue(newValue));
+    return true;
+}
+
 /*!
     Returns whether the headers contain header with \a name.
 

src/network/access/qhttpheaders.h

@@ -219,6 +219,9 @@ public:
     Q_NETWORK_EXPORT bool replace(qsizetype i, QAnyStringView name, QAnyStringView newValue);
     Q_NETWORK_EXPORT bool replace(qsizetype i, WellKnownHeader name, QAnyStringView newValue);
 
+    Q_NETWORK_EXPORT bool replaceOrAppend(QAnyStringView name, QAnyStringView newValue);
+    Q_NETWORK_EXPORT bool replaceOrAppend(WellKnownHeader name, QAnyStringView newValue);
+
     Q_NETWORK_EXPORT bool contains(QAnyStringView name) const;
     Q_NETWORK_EXPORT bool contains(WellKnownHeader name) const;
 

tests/auto/network/access/qhttpheaders/tst_qhttpheaders.cpp

@@ -21,6 +21,7 @@ private slots:
     void headerNameField();
     void headerValueField();
     void valueEncoding();
+    void replaceOrAppend();
 
 private:
     static constexpr QAnyStringView n1{"name1"};
@@ -488,5 +489,64 @@ void tst_QHttpHeaders::valueEncoding()
     QCOMPARE(h1.values(n1).at(0), "foo%E2%82%AC");
 }
 
+void tst_QHttpHeaders::replaceOrAppend()
+{
+    QHttpHeaders h1;
+
+#define REPLACE_OR_APPEND(NAME, VALUE, INDEX, TOTALSIZE) \
+    do {                                                 \
+        QVERIFY(h1.replaceOrAppend(NAME, VALUE));        \
+        QCOMPARE(h1.size(), TOTALSIZE);                  \
+        QCOMPARE(h1.nameAt(INDEX), NAME);                \
+        QCOMPARE(h1.valueAt(INDEX), VALUE);              \
+    } while (false)
+
+    // Append to empty container and replace it
+    REPLACE_OR_APPEND(n1, v1, 0, 1); // Appends
+    REPLACE_OR_APPEND(n1, v2, 0, 1); // Replaces
+
+    // Replace at beginning, middle, and end
+    h1.clear();
+    REPLACE_OR_APPEND(n1, v1, 0, 1); // Appends
+    REPLACE_OR_APPEND(n2, v2, 1, 2); // Appends
+    REPLACE_OR_APPEND(n3, v3, 2, 3); // Appends
+    REPLACE_OR_APPEND(n1, V1, 0, 3); // Replaces at beginning
+    REPLACE_OR_APPEND(n2, V2, 1, 3); // Replaces at middle
+    REPLACE_OR_APPEND(n3, V3, 2, 3); // Replaces at end
+
+    // Pre-existing multiple values (n2) are removed
+    h1.clear();
+    h1.append(n1, v1);
+    h1.append(n2, v2); // First n2 is at index 1
+    h1.append(n2, v2);
+    h1.append(n3, v3);
+    h1.append(n2, v2);
+    QCOMPARE(h1.size(), 5);
+    QCOMPARE(h1.combinedValue(n2), "value2, value2, value2");
+    REPLACE_OR_APPEND(n2, V2, 1, 3); // Replaces value at index 1, and removes the rest
+    QCOMPARE(h1.combinedValue(n2), "VALUE2");
+#undef REPLACE_OR_APPEND
+
+    // Implicit sharing / detaching
+    h1.clear();
+    h1.append(n1, v1);
+    QHttpHeaders h2 = h1;
+    QCOMPARE(h1.size(), h2.size());
+    QCOMPARE(h1.valueAt(0), h2.valueAt(0)); // Iniially values are equal
+    h1.replaceOrAppend(n1, v2);  // Change value in h1 => detaches h1
+    QCOMPARE_NE(h1.valueAt(0), h2.valueAt(0)); // Values are no more equal
+    QCOMPARE(h1.valueAt(0), v2); // Value in h1 changed
+    QCOMPARE(h2.valueAt(0), v1); // Value in h2 remained
+
+    // Failed attempts
+    h1.clear();
+    h1.append(n1, v1);
+    QRegularExpression re("HTTP header*");
+    QTest::ignoreMessage(QtMsgType::QtWarningMsg, re);
+    QVERIFY(!h1.replaceOrAppend("", V1));
+    QTest::ignoreMessage(QtMsgType::QtWarningMsg, re);
+    QVERIFY(!h1.replaceOrAppend(v1, "foo\x08"));
+}
+
 QTEST_MAIN(tst_QHttpHeaders)
 #include "tst_qhttpheaders.moc"