View source for Performance/Improver performance about string

I tried three methods.
= About string cache:= 
Sometimes cache the struct 'rtl_uString'  in a hash object. 

That will add the cost like 'internRelease',
'rtl_ustring_intern_internal'  when add a 'rtl_uString' and a 'rtl_uString'  refCount is '0'. 

I think it's purpose is reducing memory cost( right or no). 

We can don't use the cache to improver performance.

= About some methods:= 
Calculate the 'rtl_uString'/'rtl_String' hashCode and compare the 'rtl_uString'/'rtl_String', 
that is one by one. So many 'sal_Cahr'/'sal_Unicode' and many operator times. 

The 'sal_Cahr'/'sal_Unicode' and 'sal_Int32' are the same data type. 

We can operator the 'sal_Cahr'/'sal_Unicode' like operator 'sal_Int32', and one 'sal_Int32' is 4/2 'sal_Cahr'/'sal_Unicode' ;that will reduce the operator times. 

As :
<source lang="cpp">
sal_Int32 SAL_CALL IMPL_RTL_STRNAME( hashCode_WithLength )
( const IMPL_RTL_STRCODE* pStr, sal_Int32 nLen )
{
    static sal_Int32 _count = sizeof(sal_Int32)/sizeof(IMPL_RTL_STRCODE);
    sal_Int32 h = nLen;
    while ( nLen > 0 )
    {
        if( nLen > _count )
        {
            h +=  (*((sal_Int32*)(void *)pStr ))*37;
            pStr+= _count;
            nLen-= _count;
        }else
        {
            h = (h)*37 + IMPL_RTL_USTRCODE( *pStr );
            pStr++;
            nLen--;
        }
    }   
    return h;
}
</source>

= About string struct design:= 
Now the struct has three members: 'refCount',  'length',  'buffer'. 

Compare and calculate hash value for string that is frequent . 

We can add a field it cache the string's hash value. 

Some times Compare or calculate hash value; these will compare the cache value or  return the cache value directly. 

<b>I 'd tried the three methods; it is not particularly evident from the time comparison.</b>

[[Category:Performance]]