QByteArray: don't detach in remove()

- If this bytearray isn't shared call d->erase() as needed
- if it's shared, instead of detaching, create a new bytearray, and copy
  all characters except for the ones that would be removed

See task for details.

Adjust unittest to test both code paths.

Task-number: QTBUG-106182
Change-Id: I806e4d1707004345a2472e056905fbf675f765ab
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/text/qbytearray.cpp

@@ -2253,11 +2253,20 @@ QByteArray &QByteArray::remove(qsizetype pos, qsizetype len)
 {
     if (len <= 0  || pos < 0 || size_t(pos) >= size_t(size()))
         return *this;
-    detach();
     if (pos + len > d->size)
         len = d->size - pos;
-    d->erase(d.begin() + pos, len);
+
+    auto begin = d.begin();
+    if (!d->isShared()) {
+        d->erase(begin + pos, len);
         d.data()[d.size] = '\0';
+    } else {
+        QByteArray copy{size() - len, Qt::Uninitialized};
+        const auto toRemove_start = d.begin() + pos;
+        copy.d->copyRanges({{d.begin(), toRemove_start},
+                           {toRemove_start + len, d.end()}});
+        swap(copy);
+    }
     return *this;
 }
 

tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp

@@ -1258,7 +1258,14 @@ void tst_QByteArray::remove()
     QFETCH(int, position);
     QFETCH(int, length);
     QFETCH(QByteArray, expected);
-    QCOMPARE(src.remove(position, length), expected);
+    // Test when it's shared
+    QByteArray ba1 = src;
+    QCOMPARE(ba1.remove(position, length), expected);
+
+    // Test when it's not shared
+    QByteArray ba2 = src;
+    ba2.detach();
+    QCOMPARE(ba2.remove(position, length), expected);
 }
 
 void tst_QByteArray::removeIf()