Return correct length for Authority token

Regression from f4fd558ac9d61fe06aa0f56d829916ef9e5ee7b9
Take the chance to calculate token prefix just once.

Change-Id: I19ce5cb037198cb918e79c760a92b285f9b725f1
(cherry picked from commit 34b98af8e5a4e568d8316700bea1ce604d825ce8)
Reviewed-on: https://gerrit.libreoffice.org/52621
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>
diff --git a/sw/source/core/tox/tox.cxx b/sw/source/core/tox/tox.cxx
index ed47165..c86b4c9 100644
--- a/sw/source/core/tox/tox.cxx
+++ b/sw/source/core/tox/tox.cxx
@@ -745,30 +745,29 @@ static FormTokenType lcl_GetTokenType(const OUString & sToken,
{
    static struct
    {
        OUString sNm;
        sal_uInt16 nOffset;
        FormTokenType eToken;
        OUString sTokenStart;
        sal_Int16 nTokenLength;
        FormTokenType eTokenType;
    } const aTokenArr[] = {
        { SwForm::GetFormTab(),         1, TOKEN_TAB_STOP },
        { SwForm::GetFormPageNums(),    1, TOKEN_PAGE_NUMS },
        { SwForm::GetFormLinkStt(),     1, TOKEN_LINK_START },
        { SwForm::GetFormLinkEnd(),     1, TOKEN_LINK_END },
        { SwForm::GetFormEntryNum(),    1, TOKEN_ENTRY_NO },
        { SwForm::GetFormEntryText(),    1, TOKEN_ENTRY_TEXT },
        { SwForm::GetFormChapterMark(), 1, TOKEN_CHAPTER_INFO },
        { SwForm::GetFormText(),        1, TOKEN_TEXT },
        { SwForm::GetFormEntry(),       1, TOKEN_ENTRY },
        { SwForm::GetFormAuth(),        3, TOKEN_AUTHORITY }
        { SwForm::GetFormTab().copy(0, 2),         3, TOKEN_TAB_STOP },
        { SwForm::GetFormPageNums().copy(0, 2),    3, TOKEN_PAGE_NUMS },
        { SwForm::GetFormLinkStt().copy(0, 3),     4, TOKEN_LINK_START },
        { SwForm::GetFormLinkEnd().copy(0, 3),     4, TOKEN_LINK_END },
        { SwForm::GetFormEntryNum().copy(0, 3),    4, TOKEN_ENTRY_NO },
        { SwForm::GetFormEntryText().copy(0, 3),   4, TOKEN_ENTRY_TEXT },
        { SwForm::GetFormChapterMark().copy(0, 2), 3, TOKEN_CHAPTER_INFO },
        { SwForm::GetFormText().copy(0, 2),        3, TOKEN_TEXT },
        { SwForm::GetFormEntry().copy(0, 2),       3, TOKEN_ENTRY },
        { SwForm::GetFormAuth().copy(0, 2),        5, TOKEN_AUTHORITY }
    };

    for(const auto & i : aTokenArr)
    {
        const sal_Int32 nLen(i.sNm.getLength());
        if( sToken.startsWith( i.sNm.copy(0, nLen - i.nOffset) ))
        if( sToken.startsWith( i.sTokenStart ) )
        {
            if (pTokenLen)
                *pTokenLen = nLen;
            return i.eToken;
                *pTokenLen = i.nTokenLength;
            return i.eTokenType;
        }
    }