loplugin:stringview

Add new methods "subView" to O(U)String to return substring views
of the underlying data.

Add a clang plugin to warn when replacing existing calls to copy()
would be better to use subView().

Change-Id: I03a5732431ce60808946f2ce2c923b22845689ca
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/105420
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

2 files changed, 80 insertions, 0 deletions

diff --git a/include/rtl/string.hxx b/include/rtl/string.hxx
index be78e199c412..4d229fd86931 100644
--- a/include/rtl/string.hxx
+++ b/include/rtl/string.hxx
@@ -1393,6 +1393,46 @@ public:
         return OString( pNew, SAL_NO_ACQUIRE );
     }
 
+#if defined LIBO_INTERNAL_ONLY
+    /**
+      Returns a std::string_view that is a view of a substring of this string.
+
+      The substring begins at the specified beginIndex. If
+      beginIndex is negative or be greater than the length of
+      this string, behaviour is undefined.
+
+      @param     beginIndex   the beginning index, inclusive.
+      @return    the specified substring.
+    */
+    SAL_WARN_UNUSED_RESULT std::string_view subView( sal_Int32 beginIndex ) const
+    {
+        assert(beginIndex >= 0);
+        assert(beginIndex <= getLength());
+        return subView(beginIndex, getLength() - beginIndex);
+    }
+
+    /**
+      Returns a std::string_view that is a view of a substring of this string.
+
+      The substring begins at the specified beginIndex and contains count
+      characters.  If either beginIndex or count are negative,
+      or beginIndex + count are greater than the length of this string
+      then behaviour is undefined.
+
+      @param     beginIndex   the beginning index, inclusive.
+      @param     count        the number of characters.
+      @return    the specified substring.
+    */
+    SAL_WARN_UNUSED_RESULT std::string_view subView( sal_Int32 beginIndex, sal_Int32 count ) const
+    {
+        assert(beginIndex >= 0);
+        assert(count >= 0);
+        assert(beginIndex <= getLength());
+        assert(count <= getLength() - beginIndex);
+        return std::string_view(*this).substr(beginIndex, count);
+    }
+#endif
+
 #ifndef LIBO_INTERNAL_ONLY // "RTL_FAST_STRING"
     /**
       Concatenates the specified string to the end of this string.
diff --git a/include/rtl/ustring.hxx b/include/rtl/ustring.hxx
index f3006847de1e..48aca3243383 100644
--- a/include/rtl/ustring.hxx
+++ b/include/rtl/ustring.hxx
@@ -2300,6 +2300,46 @@ public:
         return OUString( pNew, SAL_NO_ACQUIRE );
     }
 
+#if defined LIBO_INTERNAL_ONLY
+    /**
+      Returns a std::u16string_view that is a view of a substring of this string.
+
+      The substring begins at the specified beginIndex. If
+      beginIndex is negative or be greater than the length of
+      this string, behaviour is undefined.
+
+      @param     beginIndex   the beginning index, inclusive.
+      @return    the specified substring.
+    */
+    SAL_WARN_UNUSED_RESULT std::u16string_view subView( sal_Int32 beginIndex ) const
+    {
+        assert(beginIndex >= 0);
+        assert(beginIndex <= getLength());
+        return subView(beginIndex, getLength() - beginIndex);
+    }
+
+    /**
+      Returns a std::u16string_view that is a view of a substring of this string.
+
+      The substring begins at the specified beginIndex and contains count
+      characters.  If either beginIndex or count are negative,
+      or beginIndex + count are greater than the length of this string
+      then behaviour is undefined.
+
+      @param     beginIndex   the beginning index, inclusive.
+      @param     count        the number of characters.
+      @return    the specified substring.
+    */
+    SAL_WARN_UNUSED_RESULT std::u16string_view subView( sal_Int32 beginIndex, sal_Int32 count ) const
+    {
+        assert(beginIndex >= 0);
+        assert(count >= 0);
+        assert(beginIndex <= getLength());
+        assert(count <= getLength() - beginIndex);
+        return std::u16string_view(*this).substr(beginIndex, count);
+    }
+#endif
+
 #ifndef LIBO_INTERNAL_ONLY // "RTL_FAST_STRING"
     /**
       Concatenates the specified string to the end of this string.