Add OString::startsWithIgnoreAsciiCase

...analogous to the existing OUString::startsWihtIgnoreAsciiCase, to be used in
the next commit

Change-Id: Iad6989c16e1bda6b2b0a58e6c768f7852560bb00

include/rtl/string.hxx

@@ -762,6 +762,55 @@ public:
         return b;
     }
 
+    /**
+      Check whether this string starts with a given string, ignoring the case of
+      ASCII letters.
+
+      Character values between 65 and 90 (ASCII A-Z) are interpreted as
+      values between 97 and 122 (ASCII a-z).
+      This function can't be used for language specific comparison.
+
+      @param str the substring to be compared
+
+      @param rest if non-null, and this function returns true, then assign a
+      copy of the remainder of this string to *rest.
+
+      @return true if and only if the given str appears as a substring at the
+      start of this string, ignoring the case of ASCII letters ("A"--"Z" and
+      "a"--"z")
+
+      @since LibreOffice 5.1
+    */
+    bool startsWithIgnoreAsciiCase(OString const & str, OString * rest = 0)
+        const
+    {
+        bool b = matchIgnoreAsciiCase(str);
+        if (b && rest != 0) {
+            *rest = copy(str.getLength());
+        }
+        return b;
+    }
+
+    /**
+     @overload
+     This function accepts an ASCII string literal as its argument.
+     @since LibreOffice 5.1
+    */
+    template< typename T >
+    typename libreoffice_internal::ConstCharArrayDetector< T, bool >::Type
+    startsWithIgnoreAsciiCase(T & literal, OString * rest = 0) const
+    {
+        RTL_STRING_CONST_FUNCTION
+        assert(
+            libreoffice_internal::ConstCharArrayDetector<T>::isValid(literal));
+        bool b = matchIgnoreAsciiCase(literal);
+        if (b && rest != 0) {
+            *rest = copy(
+                libreoffice_internal::ConstCharArrayDetector<T>::length);
+        }
+        return b;
+    }
+
     /**
       Check whether this string ends with a given substring.
 

sal/CppunitTest_sal_rtl_strings.mk

@@ -12,6 +12,7 @@ $(eval $(call gb_CppunitTest_CppunitTest,sal_rtl_strings))
 
 $(eval $(call gb_CppunitTest_add_exception_objects,sal_rtl_strings,\
     sal/qa/rtl/strings/test_strings_replace \
+    sal/qa/rtl/strings/test_ostring \
     sal/qa/rtl/strings/test_ostring_concat \
     sal/qa/rtl/strings/test_ostring_stringliterals \
     sal/qa/rtl/strings/test_oustring_compare \

sal/qa/rtl/strings/test_ostring.cxx

+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * 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 <cppunit/TestAssert.h>
+#include <cppunit/TestFixture.h>
+#include <cppunit/extensions/HelperMacros.h>
+#include <rtl/string.hxx>
+
+namespace {
+
+class Test: public CppUnit::TestFixture {
+private:
+    void testStartsWithIgnoreAsciiCase();
+
+    CPPUNIT_TEST_SUITE(Test);
+    CPPUNIT_TEST(testStartsWithIgnoreAsciiCase);
+    CPPUNIT_TEST_SUITE_END();
+};
+
+void Test::testStartsWithIgnoreAsciiCase() {
+    {
+        OString r;
+        CPPUNIT_ASSERT(OString().startsWithIgnoreAsciiCase(OString(), &r));
+        CPPUNIT_ASSERT(r.isEmpty());
+    }
+    {
+        OString r;
+        CPPUNIT_ASSERT(OString("foo").startsWithIgnoreAsciiCase(OString(), &r));
+        CPPUNIT_ASSERT_EQUAL(OString("foo"), r);
+    }
+    {
+        OString r;
+        CPPUNIT_ASSERT(
+            OString("foo").startsWithIgnoreAsciiCase(OString("F"), &r));
+        CPPUNIT_ASSERT_EQUAL(OString("oo"), r);
+    }
+    {
+        OString r("other");
+        CPPUNIT_ASSERT(
+            !OString("foo").startsWithIgnoreAsciiCase(OString("bar"), &r));
+        CPPUNIT_ASSERT_EQUAL(OString("other"), r);
+    }
+    {
+        OString r("other");
+        CPPUNIT_ASSERT(
+            !OString("foo").startsWithIgnoreAsciiCase(OString("foobar"), &r));
+        CPPUNIT_ASSERT_EQUAL(OString("other"), r);
+    }
+
+    {
+        OString r;
+        CPPUNIT_ASSERT(OString().startsWithIgnoreAsciiCase("", &r));
+        CPPUNIT_ASSERT(r.isEmpty());
+    }
+    {
+        OString r;
+        CPPUNIT_ASSERT(OString("foo").startsWithIgnoreAsciiCase("", &r));
+        CPPUNIT_ASSERT_EQUAL(OString("foo"), r);
+    }
+    {
+        OString r;
+        CPPUNIT_ASSERT(
+            OString("foo").startsWithIgnoreAsciiCase("F", &r));
+        CPPUNIT_ASSERT_EQUAL(OString("oo"), r);
+    }
+    {
+        OString r("other");
+        CPPUNIT_ASSERT(
+            !OString("foo").startsWithIgnoreAsciiCase("bar", &r));
+        CPPUNIT_ASSERT_EQUAL(OString("other"), r);
+    }
+    {
+        OString r("other");
+        CPPUNIT_ASSERT(
+            !OString("foo").startsWithIgnoreAsciiCase("foobar", &r));
+        CPPUNIT_ASSERT_EQUAL(OString("other"), r);
+    }
+}
+
+CPPUNIT_TEST_SUITE_REGISTRATION(Test);
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */