reinterpret cast an array from string to int

Question

I'd like to reinterpret a string in a array of int where every int take charge of 4 or 8 chars based on processor architecture.

Is there a way to achieve this in a relatively inexpensive way? I tried out this but doesn't seem to reinterpret 4 chars in one int

string text = "abcdabcdefghefgh";

unsafe
{
    fixed( char* charPointer = text )
    {
        Int32* intPointer = (Int32*)charPointer;

        for( int index = 0; index < text.Length / 4; index++ )
        {
            Console.WriteLine( intPointer[ index ] );
        }
    }
}

SOLUTION: (change Int64 or Int32 based on your needs)

string text = "abcdabcdefghefgh";

unsafe
{
    fixed( char* charPointer = text )
    {
            Int64* intPointer = (Int64*)charPointer;
            int conversionFactor = sizeof( Int64 ) / sizeof( char );

            int index = 0;
            for(index = 0; index < text.Length / conversionFactor; index++)
            {
                Console.WriteLine( intPointer[ index ] );
            }

            if( text.Length % conversionFactor != 0 )
            {
                intPointer[ index ] <<= sizeof( Int64 );
                intPointer[ index ] >>= sizeof( Int64 );

                Console.WriteLine( intPointer[ index ] );
            }
     }
}

Chars in C# are 2 bytes, so with an Int32 pointer you're going to get two chars per int. — Doctor Vermilion Wizard
– Doctor Vermilion Wizard, Commented Mar 24, 2015 at 16:42
If you know your characters are 8-bit friendly you could extract them and stuff four into each integer yourself, but you would need to make a copy of the data. — yoyo
– yoyo, Commented Mar 24, 2015 at 16:46
Please see "Should questions include “tags” in their titles?", where the consensus is "no, they should not"! — user57508
– user57508, Commented Mar 25, 2015 at 9:31
@AndreasNiedermair please mess somewhere else.. I want my title to be expressive of the problem so google can help — Mauro Sampietro
– Mauro Sampietro, Commented Mar 25, 2015 at 9:53
@sam Please follow my link: Stack Overflow is optimized so that tags are indexed by search engines along with the content of the question. ... and watch your tongue! — user57508
– user57508, Commented Mar 25, 2015 at 9:53

usr · Accepted Answer · 2015-03-24 16:58:00Z

4

You almost got it right. sizeof(char) == 2 && sizeof(int) == 4. The loop conversion factor must be 2, not 4. It's sizeof(int) / sizeof(char). If you like this style you can use this exact expression. sizeof is a little known C# feature.

Note, that right now you lose the last character if the length is not even.

About performance: The way you have done it is as inexpensive as it gets.

answered Mar 24, 2015 at 16:58

usr

172k38 gold badges251 silver badges380 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

reinterpret cast an array from string to int

1 Answer 1

Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Related