array_view was changed to span in upcoming C++20

...see <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0122r7.pdf>
"span: bounds-safe views for sequences of objects".  o3tl::span is still an
incomplete approximation of std::span; removed those o3tl::array_view members
that are not present in std::span (and were not used in the code).

Relies on C++17 __has_include to use standard <span> where available (e.g., in
LLVM 7 libc++).

Change-Id: I82a7e246b61b2456fa6183025d25eec4121ad3c9
Reviewed-on: https://gerrit.libreoffice.org/66215
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

9 files changed, 172 insertions, 259 deletions

diff --git a/include/o3tl/array_view.hxx b/include/o3tl/array_view.hxx
deleted file mode 100644
index dd6ca7fa94c0..000000000000
--- a/include/o3tl/array_view.hxx
+++ /dev/null
@@ -1,163 +0,0 @@
-/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
-/*
- * This file is part of the LibreOffice project.
- *
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/.
- */
-
-#ifndef INCLUDED_O3TL_ARRAY_VIEW_HXX
-#define INCLUDED_O3TL_ARRAY_VIEW_HXX
-
-#include <sal/config.h>
-
-#include <algorithm>
-#include <cstddef>
-#include <ios>
-#include <iterator>
-#include <ostream>
-#include <stdexcept>
-#include <string>
-#include <type_traits>
-#include <utility>
-
-#include <rtl/string.hxx>
-#include <rtl/ustring.hxx>
-#include <sal/types.h>
-
-namespace o3tl {
-
-#if defined _MSC_VER
-#pragma warning(push)
-#pragma warning(disable: 4522) // multiple assignment operators specified
-#endif
-
-/** A barebones approximation of C++17(?) <array_view>.
-  Haven't bothered with more than single-dimensional arrays.
-*/
-template<typename T>
-class array_view {
-    friend class array_view<T const>;
-public:
-    using value_type = T;
-    using pointer = value_type *;
-    using const_pointer = value_type const *;
-    using reference = value_type &;
-    using const_reference = value_type const &;
-    using const_iterator = const_pointer;
-    using iterator = pointer;
-    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
-    using reverse_iterator = std::reverse_iterator<iterator>;
-    using size_type = std::size_t;
-    using difference_type = std::ptrdiff_t;
-
-    static constexpr size_type npos = size_type(-1);
-
-    constexpr array_view() noexcept : data_(nullptr), size_(0) {}
-
-    template<size_type N>
-    constexpr array_view (T (&a)[N]) noexcept : data_(a), size_(N) {}
-
-    constexpr array_view (T *a, size_type len) noexcept
-        : data_(a), size_(len)
-    {
-        // not terribly sure about this, might need to relax it
-        assert((a == nullptr && len == 0) || (a != nullptr && len > 0));
-    }
-
-    /// Allow for assigning array_view<T> to array_view<T const> i.e.
-    ///   array_view<T> a;
-    ///   array_view<T const> b = a;
-    template<typename = std::enable_if< std::is_const<value_type>::value > >
-    array_view& operator=(array_view<typename std::remove_const<value_type>::type> const & other)
-    {
-        data_ = other.data_;
-        size_ = other.size_;
-        return *this;
-    }
-
-    constexpr bool empty() const noexcept { return size_ == 0; }
-
-    constexpr iterator begin() const noexcept { return data_; }
-    constexpr iterator end() const noexcept { return begin() + size(); }
-
-    constexpr const_iterator cbegin() const noexcept { return begin(); }
-    constexpr const_iterator cend() const noexcept { return end(); }
-
-    reverse_iterator rbegin() const noexcept
-    { return reverse_iterator(end()); }
-    reverse_iterator rend() const noexcept
-    { return reverse_iterator(begin()); }
-
-    constexpr const_reverse_iterator crbegin() const noexcept
-    { return rbegin(); }
-    constexpr const_reverse_iterator crend() const noexcept { return rend(); }
-
-    constexpr size_type size() const noexcept { return size_; }
-    constexpr size_type length() const noexcept { return size(); }
-
-    constexpr size_type max_size() const noexcept {
-        (void) this; // silence loplugin:staticmethods
-        return npos - 1;
-    }
-
-    constexpr reference operator [](size_type pos) const {
-        assert(pos < size());
-        return data_[pos];
-    }
-
-    constexpr reference at(size_type pos) const {
-        if (pos >= size()) {
-            throw std::out_of_range("o3tl::array_view::at");
-        }
-        return operator [](pos);
-    }
-
-    constexpr reference front() const {
-        assert(!empty());
-        return operator [](0);
-    }
-
-    constexpr reference back() const {
-        assert(!empty());
-        return operator [](size() - 1);
-    }
-
-    constexpr pointer data() const noexcept { return data_; }
-
-    constexpr void swap(array_view & s) noexcept {
-        std::swap(data_, s.data_);
-        std::swap(size_, s.size_);
-    }
-
-    /// so we can use it in associative containers
-    constexpr bool operator<(array_view const & other) const noexcept {
-        return data_ < other.data_ && size_ < other.size_;
-    }
-
-private:
-    pointer    data_;
-    size_type  size_;
-};
-
-
-#if defined _MSC_VER
-#pragma warning(pop)
-#endif
-
-} // namespace o3tl
-
-namespace std {
-
-template<typename T>
-struct hash<o3tl::array_view<T>> {
-    std::size_t operator()(o3tl::array_view<T> s) const
-    { return hash<T[]>()(s.data(), s.size()); }
-};
-
-} // namespace std
-
-#endif
-
-/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
diff --git a/include/o3tl/span.hxx b/include/o3tl/span.hxx
new file mode 100644
index 000000000000..acb31bab728d
--- /dev/null
+++ b/include/o3tl/span.hxx
@@ -0,0 +1,95 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_O3TL_SPAN_HXX
+#define INCLUDED_O3TL_SPAN_HXX
+
+#include <sal/config.h>
+
+#if __has_include(<span>)
+
+#include <span>
+
+namespace o3tl { using std::span; }
+
+#else
+
+#include <cassert>
+#include <cstddef>
+#include <iterator>
+
+namespace o3tl {
+
+/** A barebones approximation of C++20 <span>.
+*/
+template<typename T>
+class span {
+public:
+    using value_type = T;
+    using pointer = value_type *;
+    using const_pointer = value_type const *;
+    using reference = value_type &;
+    using const_reference = value_type const &;
+    using const_iterator = const_pointer;
+    using iterator = pointer;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+    using reverse_iterator = std::reverse_iterator<iterator>;
+    using index_type = std::ptrdiff_t;
+    using difference_type = std::ptrdiff_t;
+
+    constexpr span() noexcept : data_(nullptr), size_(0) {}
+
+    template<std::size_t N>
+    constexpr span (T (&a)[N]) noexcept : data_(a), size_(N) {}
+
+    constexpr span (T *a, index_type len) noexcept
+        : data_(a), size_(len)
+    {
+        // not terribly sure about this, might need to strengthen it
+        assert((a == nullptr && len == 0) || (a != nullptr && len >= 0));
+    }
+
+    constexpr bool empty() const noexcept { return size_ == 0; }
+
+    constexpr iterator begin() const noexcept { return data_; }
+    constexpr iterator end() const noexcept { return begin() + size(); }
+
+    constexpr const_iterator cbegin() const noexcept { return begin(); }
+    constexpr const_iterator cend() const noexcept { return end(); }
+
+    reverse_iterator rbegin() const noexcept
+    { return reverse_iterator(end()); }
+    reverse_iterator rend() const noexcept
+    { return reverse_iterator(begin()); }
+
+    constexpr const_reverse_iterator crbegin() const noexcept
+    { return rbegin(); }
+    constexpr const_reverse_iterator crend() const noexcept { return rend(); }
+
+    constexpr index_type size() const noexcept { return size_; }
+
+    constexpr reference operator [](index_type pos) const {
+        assert(0 <= pos && pos < size());
+        return data_[pos];
+    }
+
+    constexpr pointer data() const noexcept { return data_; }
+
+private:
+    pointer    data_;
+    index_type size_;
+};
+
+} // namespace o3tl
+
+#endif
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
diff --git a/include/sfx2/dispatch.hxx b/include/sfx2/dispatch.hxx
index 9e2f0a0379a2..899957133024 100644
--- a/include/sfx2/dispatch.hxx
+++ b/include/sfx2/dispatch.hxx
@@ -29,7 +29,7 @@
 #include <sfx2/viewfrm.hxx>
 #include <vcl/menu.hxx>
 #include <o3tl/typed_flags_set.hxx>
-#include <o3tl/array_view.hxx>
+#include <o3tl/span.hxx>
 
 #include <initializer_list>
 
@@ -161,7 +161,7 @@ public:
     void                Lock( bool bLock );
     bool                IsLocked() const;
     void                SetSlotFilter( SfxSlotFilterState nEnable = SfxSlotFilterState::DISABLED,
-                                       o3tl::array_view<sal_uInt16 const> pSIDs = o3tl::array_view<sal_uInt16 const>());
+                                       o3tl::span<sal_uInt16 const> pSIDs = o3tl::span<sal_uInt16 const>());
 
     void                HideUI( bool bHide = true );
     ToolbarId           GetObjectBarId( sal_uInt16 nPos ) const;
diff --git a/o3tl/CppunitTest_o3tl_tests.mk b/o3tl/CppunitTest_o3tl_tests.mk
index 1dbfebdf798a..152fa48c72ca 100644
--- a/o3tl/CppunitTest_o3tl_tests.mk
+++ b/o3tl/CppunitTest_o3tl_tests.mk
@@ -27,12 +27,12 @@ $(eval $(call gb_CppunitTest_use_libraries,o3tl_tests,\
 
 $(eval $(call gb_CppunitTest_add_exception_objects,o3tl_tests,\
 	o3tl/qa/cow_wrapper_clients \
-	o3tl/qa/test-array_view \
 	o3tl/qa/test-cow_wrapper \
 	o3tl/qa/test-enumarray \
 	o3tl/qa/test-lru_map \
 	o3tl/qa/test-safeint \
 	o3tl/qa/test-sorted_vector \
+	o3tl/qa/test-span \
 	o3tl/qa/test-typed_flags \
 	o3tl/qa/test-vector_pool \
 ))
diff --git a/o3tl/qa/test-array_view.cxx b/o3tl/qa/test-array_view.cxx
deleted file mode 100644
index b82aa8cd1bf4..000000000000
--- a/o3tl/qa/test-array_view.cxx
+++ /dev/null
@@ -1,85 +0,0 @@
-/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
-/*
- * This file is part of the LibreOffice project.
- *
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/.
- */
-
-#include <sal/config.h>
-
-#include <stdexcept>
-
-#include <cppunit/TestAssert.h>
-#include <cppunit/TestFixture.h>
-#include <cppunit/extensions/HelperMacros.h>
-
-#include <o3tl/array_view.hxx>
-
-namespace {
-
-class Test: public CppUnit::TestFixture {
-private:
-    CPPUNIT_TEST_SUITE(Test);
-    CPPUNIT_TEST(testOperations);
-    CPPUNIT_TEST_SUITE_END();
-
-
-    void testOperations() {
-        int const some_data[] { 1, 2, 3 };
-        o3tl::array_view<int const> v(some_data);
-
-        CPPUNIT_ASSERT_EQUAL(1, *v.begin());
-        CPPUNIT_ASSERT_EQUAL(
-            o3tl::array_view<int>::difference_type(3), v.end() - v.begin());
-        CPPUNIT_ASSERT_EQUAL(1, *v.cbegin());
-        CPPUNIT_ASSERT_EQUAL(
-            o3tl::array_view<int>::difference_type(3), v.cend() - v.cbegin());
-        CPPUNIT_ASSERT_EQUAL(3, *v.rbegin());
-        CPPUNIT_ASSERT_EQUAL(
-            o3tl::array_view<int>::difference_type(3), v.rend() - v.rbegin());
-        CPPUNIT_ASSERT_EQUAL(3, *v.crbegin());
-        CPPUNIT_ASSERT_EQUAL(
-            o3tl::array_view<int>::difference_type(3), v.crend() - v.crbegin());
-        CPPUNIT_ASSERT_EQUAL(o3tl::array_view<int>::size_type(3), v.size());
-        CPPUNIT_ASSERT_EQUAL(o3tl::array_view<int>::size_type(3), v.length());
-        CPPUNIT_ASSERT_EQUAL(o3tl::array_view<int>::npos - 1, v.max_size());
-        CPPUNIT_ASSERT(!v.empty());
-        CPPUNIT_ASSERT_EQUAL(2, v[1]);
-        try {
-            v.at(o3tl::array_view<int>::npos);
-            CPPUNIT_FAIL("missing exception");
-        } catch (std::out_of_range &) {}
-        CPPUNIT_ASSERT_EQUAL(1, v.at(0));
-        CPPUNIT_ASSERT_EQUAL(3, v.at(2));
-        try {
-            v.at(3);
-            CPPUNIT_FAIL("missing exception");
-        } catch (std::out_of_range &) {}
-        CPPUNIT_ASSERT_EQUAL(1, v.front());
-        CPPUNIT_ASSERT_EQUAL(3, v.back());
-        CPPUNIT_ASSERT_EQUAL(1, *v.data());
-        {
-            int const d1[] { 1, 2 };
-            int const d2[] { 3, 4, 5, 6 };
-            o3tl::array_view<int const> v1( d1 );
-            o3tl::array_view<int const> v2( d2 );
-            v1.swap(v2);
-            CPPUNIT_ASSERT_EQUAL(o3tl::array_view<int>::size_type(4), v1.size());
-            CPPUNIT_ASSERT_EQUAL(o3tl::array_view<int>::size_type(2), v2.size());
-        }
-        {
-            int d1[] { 1, 2, 3 };
-            o3tl::array_view<int> v1(d1);
-            o3tl::array_view<int const> v2;
-            v2 = v1; // the special operator=
-        }
-    }
-};
-
-CPPUNIT_TEST_SUITE_REGISTRATION(Test);
-
-}
-
-/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
diff --git a/o3tl/qa/test-span.cxx b/o3tl/qa/test-span.cxx
new file mode 100644
index 000000000000..7ec67fa7fd91
--- /dev/null
+++ b/o3tl/qa/test-span.cxx
@@ -0,0 +1,65 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <sal/config.h>
+
+#include <utility>
+
+#include <cppunit/TestAssert.h>
+#include <cppunit/TestFixture.h>
+#include <cppunit/extensions/HelperMacros.h>
+
+#include <o3tl/span.hxx>
+
+namespace {
+
+class Test: public CppUnit::TestFixture {
+private:
+    CPPUNIT_TEST_SUITE(Test);
+    CPPUNIT_TEST(testOperations);
+    CPPUNIT_TEST_SUITE_END();
+
+
+    void testOperations() {
+        int const some_data[] { 1, 2, 3 };
+        o3tl::span<int const> v(some_data);
+
+        CPPUNIT_ASSERT_EQUAL(1, *v.begin());
+        CPPUNIT_ASSERT_EQUAL(
+            o3tl::span<int>::difference_type(3), v.end() - v.begin());
+        CPPUNIT_ASSERT_EQUAL(1, *v.cbegin());
+        CPPUNIT_ASSERT_EQUAL(
+            o3tl::span<int>::difference_type(3), v.cend() - v.cbegin());
+        CPPUNIT_ASSERT_EQUAL(3, *v.rbegin());
+        CPPUNIT_ASSERT_EQUAL(
+            o3tl::span<int>::difference_type(3), v.rend() - v.rbegin());
+        CPPUNIT_ASSERT_EQUAL(3, *v.crbegin());
+        CPPUNIT_ASSERT_EQUAL(
+            o3tl::span<int>::difference_type(3), v.crend() - v.crbegin());
+        CPPUNIT_ASSERT_EQUAL(o3tl::span<int>::index_type(3), v.size());
+        CPPUNIT_ASSERT(!v.empty());
+        CPPUNIT_ASSERT_EQUAL(2, v[1]);
+        CPPUNIT_ASSERT_EQUAL(1, *v.data());
+        {
+            int const d1[] { 1, 2 };
+            int const d2[] { 3, 4, 5, 6 };
+            o3tl::span<int const> v1( d1 );
+            o3tl::span<int const> v2( d2 );
+            std::swap(v1, v2);
+            CPPUNIT_ASSERT_EQUAL(o3tl::span<int>::index_type(4), v1.size());
+            CPPUNIT_ASSERT_EQUAL(o3tl::span<int>::index_type(2), v2.size());
+        }
+    }
+};
+
+CPPUNIT_TEST_SUITE_REGISTRATION(Test);
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
diff --git a/sd/source/ui/inc/DrawDocShell.hxx b/sd/source/ui/inc/DrawDocShell.hxx
index 84d6d277e40a..3d400c889974 100644
--- a/sd/source/ui/inc/DrawDocShell.hxx
+++ b/sd/source/ui/inc/DrawDocShell.hxx
@@ -20,7 +20,7 @@
 #ifndef INCLUDED_SD_SOURCE_UI_INC_DRAWDOCSHELL_HXX
 #define INCLUDED_SD_SOURCE_UI_INC_DRAWDOCSHELL_HXX
 
-#include <o3tl/array_view.hxx>
+#include <o3tl/span.hxx>
 #include <sfx2/docfac.hxx>
 #include <sfx2/objsh.hxx>
 
@@ -146,7 +146,7 @@ public:
      */
     bool                    CheckPageName(weld::Window* pWin, OUString& rName );
 
-    void                    SetSlotFilter(bool bEnable = false, o3tl::array_view<sal_uInt16 const> pSIDs = o3tl::array_view<sal_uInt16 const>()) { mbFilterEnable = bEnable; mpFilterSIDs = pSIDs; }
+    void                    SetSlotFilter(bool bEnable = false, o3tl::span<sal_uInt16 const> pSIDs = o3tl::span<sal_uInt16 const>()) { mbFilterEnable = bEnable; mpFilterSIDs = pSIDs; }
     void                    ApplySlotFilter() const;
 
     SfxStyleFamily          GetStyleFamily() const { return mnStyleFamily; }
@@ -212,7 +212,7 @@ protected:
     rtl::Reference<FuPoor> mxDocShellFunction;
     DocumentType const      meDocType;
     SfxStyleFamily          mnStyleFamily;
-    o3tl::array_view<sal_uInt16 const>
+    o3tl::span<sal_uInt16 const>
                             mpFilterSIDs;
     bool                    mbFilterEnable;
     bool const              mbSdDataObj;
diff --git a/sfx2/source/control/dispatch.cxx b/sfx2/source/control/dispatch.cxx
index 7a0d8a267d84..40c7652c1f42 100644
--- a/sfx2/source/control/dispatch.cxx
+++ b/sfx2/source/control/dispatch.cxx
@@ -20,6 +20,7 @@
 #include <config_features.h>
 
 #include <algorithm>
+#include <cstddef>
 #include <deque>
 #include <vector>
 
@@ -132,7 +133,7 @@ struct SfxDispatcher_Impl
 
     SfxSlotFilterState   nFilterEnabling; // 1==filter enabled slots,
                                           // 2==ReadOnlyDoc overturned
-    o3tl::array_view<sal_uInt16 const>
+    o3tl::span<sal_uInt16 const>
                          pFilterSIDs;   // sorted Array of SIDs
     SfxDisableFlags      nDisableFlags;
     bool                 bFlushed;
@@ -1541,11 +1542,11 @@ void SfxDispatcher::FlushImpl()
         pDisp->SetSlotFilter();
 */
 void SfxDispatcher::SetSlotFilter(SfxSlotFilterState nEnable,
-        o3tl::array_view<sal_uInt16 const> pSIDs)
+        o3tl::span<sal_uInt16 const> pSIDs)
 {
 #ifdef DBG_UTIL
     // Check Array
-    for ( size_t n = 1; n < pSIDs.size(); ++n )
+    for ( std::ptrdiff_t n = 1; n < pSIDs.size(); ++n )
         DBG_ASSERT( pSIDs[n] > pSIDs[n-1], "SetSlotFilter: SIDs not sorted" );
 #endif
 
diff --git a/solenv/clang-format/blacklist b/solenv/clang-format/blacklist
index 0287ee50af5c..87f88d633832 100644
--- a/solenv/clang-format/blacklist
+++ b/solenv/clang-format/blacklist
@@ -6489,7 +6489,6 @@ include/linguistic/lngprops.hxx
 include/linguistic/misc.hxx
 include/linguistic/spelldta.hxx
 include/o3tl/any.hxx
-include/o3tl/array_view.hxx
 include/o3tl/char16_t2wchar_t.hxx
 include/o3tl/cow_wrapper.hxx
 include/o3tl/deleter.hxx
@@ -6504,6 +6503,7 @@ include/o3tl/numeric.hxx
 include/o3tl/runtimetooustring.hxx
 include/o3tl/safeint.hxx
 include/o3tl/sorted_vector.hxx
+include/o3tl/span.hxx
 include/o3tl/strong_int.hxx
 include/o3tl/typed_flags_set.hxx
 include/o3tl/vector_pool.hxx
@@ -8777,12 +8777,12 @@ mysqlc/source/mysqlc_types.cxx
 mysqlc/source/mysqlc_types.hxx
 o3tl/qa/cow_wrapper_clients.cxx
 o3tl/qa/cow_wrapper_clients.hxx
-o3tl/qa/test-array_view.cxx
 o3tl/qa/test-cow_wrapper.cxx
 o3tl/qa/test-enumarray.cxx
 o3tl/qa/test-lru_map.cxx
 o3tl/qa/test-safeint.cxx
 o3tl/qa/test-sorted_vector.cxx
+o3tl/qa/test-span.cxx
 o3tl/qa/test-string_view.cxx
 o3tl/qa/test-typed_flags.cxx
 o3tl/qa/test-vector_pool.cxx