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>

2 files changed, 62 insertions, 0 deletions

diff --git a/src/network/access/qhttpheaders.cpp b/src/network/access/qhttpheaders.cpp
index 4a65e662cf..c63da899a8 100644
--- a/src/network/access/qhttpheaders.cpp
+++ b/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.
 */
@@ -1217,6 +1235,47 @@ bool QHttpHeaders::replace(qsizetype i, WellKnownHeader name, QAnyStringView new
 }
 
 /*!
+    \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.
 
     \sa contains(QHttpHeaders::WellKnownHeader)
diff --git a/src/network/access/qhttpheaders.h b/src/network/access/qhttpheaders.h
index fb426eed80..97dc415e55 100644
--- a/src/network/access/qhttpheaders.h
+++ b/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;