Introduce QByteArrayView

Created a QByteArrayView in symmetry with QStringView.
Added the basic tests symmetrical to QStringView tests.

Moved the implementations of non-modifying methods of QByteArray to
namespace QtPrivate, to be reused inline from both QByteArray and
QByteArrayView. Changed QByteArray's counterparts of those methods to
take QByteArrayView as argument instead of QByteArray. Removed
QByteArray's operator QNoImplicitBoolCast(), because it was causing
ambiguity when calling those methods with QByteArray argument (it was
there to perevnt if(!ba)/if(ba) from compiling, but currently that would
be ambiguous and won't compile anyway).

[ChangeLog][QtCore][QByteArrayView] New class.

Task-number: QTBUG-84321
Change-Id: I05f92e654cf65c95f2bb31b9c9018746ac110426
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

2 files changed, 69 insertions, 2 deletions

diff --git a/src/corelib/doc/snippets/code/src_corelib_text_qbytearray.cpp b/src/corelib/doc/snippets/code/src_corelib_text_qbytearray.cpp
index 9c07a2e92c..74f14f2a4b 100644
--- a/src/corelib/doc/snippets/code/src_corelib_text_qbytearray.cpp
+++ b/src/corelib/doc/snippets/code/src_corelib_text_qbytearray.cpp
@@ -224,7 +224,7 @@ ba.replace(QByteArray("ou"), QByteArray("o"));
 
 //! [21]
 QByteArray x("sticky question");
-QByteArray y("sti");
+QByteArrayView y("sti");
 x.indexOf(y);               // returns 0
 x.indexOf(y, 1);            // returns 10
 x.indexOf(y, 10);           // returns 10
@@ -243,7 +243,7 @@ ba.indexOf("X");            // returns -1
 
 //! [23]
 QByteArray x("crazy azimuths");
-QByteArray y("az");
+QByteArrayView y("az");
 x.lastIndexOf(y);           // returns 6
 x.lastIndexOf(y, 6);        // returns 6
 x.lastIndexOf(y, 5);        // returns 2
diff --git a/src/corelib/doc/snippets/code/src_corelib_text_qbytearrayview.cpp b/src/corelib/doc/snippets/code/src_corelib_text_qbytearrayview.cpp
new file mode 100644
index 0000000000..31a2107c62
--- /dev/null
+++ b/src/corelib/doc/snippets/code/src_corelib_text_qbytearrayview.cpp
@@ -0,0 +1,67 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+#include <QtCore/qbytearrayview.h>
+
+//! [0]
+    void myfun1(QByteArrayView bv);        // preferred
+    void myfun2(const QByteArrayView &bv); // compiles and works, but slower
+//! [0]
+
+//! [1]
+    void fun(QByteArrayView bv);
+    void fun(char ch) { fun(QByteArrayView(&ch, 1)); }
+//! [1]
+
+void wrapper() {
+    const char array[1] = { 0 };
+//! [2]
+    auto bv = QByteArrayView(array, std::size(array)); // using C++17 std::size()
+//! [2]
+}