/*---------------------------------------------------------------------------*
  Project:  TwlSDK - MATH - 
  File:     checksum.c

  Copyright 2003-2008 Nintendo. All rights reserved.

  These coded instructions, statements, and computer programs contain
  proprietary information of Nintendo of America Inc. and/or Nintendo
  Company Ltd., and are protected by Federal copyright law. They may
  not be disclosed to third parties or copied or duplicated in any form,
  in whole or in part, without the prior written consent of Nintendo.

  $Date:: 2008-11-07#$
  $Rev: 9262 $
  $Author:$
 *---------------------------------------------------------------------------*/

#include <nitro/math/checksum.h>

/*---------------------------------------------------------------------------*
  Name:         MATHi_Checksum16Update

  Description:  Finds the 16-bit Checksum value.

  Arguments:    input: Pointer to input data
                length: Length of input data

  Returns:      Calculation result.
 *---------------------------------------------------------------------------*/
static inline u32 MATHi_Checksum16Update(const void *input, u32 length)
{
    u32     sum;
    u32     n;
    BOOL    fSwap = FALSE;

    sum = 0;

    if (((u32)input) & 1)
    {
        sum += (*((u8 *)input) << 8); // BIGENDIAN
        input = (u8 *)input + 1;
        length--;
        fSwap = TRUE;
    }

    while ((length >> 17) > 0)
    {
        length -= (1 << 17);
        for (n = (1 << 16); n > 0; n--)
        {
            sum += *(u16 *)input;
            input = (u16 *)input + 1;
        }

        sum = (sum >> 16) + (sum & 0xffff);
        sum = (u16)((sum >> 16) + sum);
    }

    for (n = (length >> 1); n > 0; n--)
    {
        sum += *(u16 *)input;
        input = (u16 *)input + 1;
    }

    if (length & 1)
    {
        sum += *((u8 *)input);
    }

    sum = (sum >> 16) + (sum & 0xffff);
    sum = (sum >> 16) + (sum & 0xffff);

    if (fSwap)
    {
        sum = ((sum << 24) | (sum << 8)) >> 16;
    }

    return sum;
}

/*---------------------------------------------------------------------------*
  Name:         MATH_Checksum16Update

  Description:  Updates the 16bit Checksum value with added data.

  Arguments:    context: MATHChecksum16Context structure
                input: Pointer to input data
                length: Length of input data

  Returns:      None.
 *---------------------------------------------------------------------------*/
void MATH_Checksum16Update(MATHChecksum16Context * context, const void *input, u32 length)
{
    u32     sum;

    sum = MATHi_Checksum16Update(input, length);

    sum += *context;
    sum += (sum >> 16);

    *context = (u16)sum;
}

/*---------------------------------------------------------------------------*
  Name:         MATH_CalcChecksum16

  Description:  Calculates the 16bit Checksum.
  
  Arguments:    data: Pointer to input data
                dataLength: Length of input data
  
  Returns:      Checksum value.
 *---------------------------------------------------------------------------*/
u16 MATH_CalcChecksum16(const void *data, u32 dataLength)
{
    u32     sum;

    sum = MATHi_Checksum16Update(data, dataLength);

    return (u16)(~sum);
}

/*---------------------------------------------------------------------------*
  Name:         MATH_Checksum8Update

  Description:  Finds the 8-bit Checksum value.

  Arguments:    input: Pointer to input data
                length: Length of input data

  Returns:      Calculation result.
 *---------------------------------------------------------------------------*/
static inline u32 MATHi_Checksum8Update(const void *input, u32 length)
{
    u32     sum;
    u32     n;

    sum = 0;

    if (((u32)input) & 1)
    {
        sum += *(u8 *)input;
        input = (u8 *)input + 1;
        length--;
    }

    while ((length >> 17) > 0)
    {
        length -= (1 << 17);
        for (n = (1 << 16); n > 0; n--)
        {
            sum += *(u16 *)input;
            input = (u16 *)input + 1;
        }

        sum = (sum >> 16) + (sum & 0xffff);
        sum = (u16)(sum + (sum >> 16));
    }

    for (n = (length >> 1); n > 0; n--)
    {
        sum += *(u16 *)input;
        input = (u16 *)input + 1;
    }

    if (length & 1)
    {
        sum += *((u8 *)input);
    }

    sum = (sum >> 16) + (sum & 0xffff);
    sum += (sum >> 16);

    return (u16)sum;
}

/*---------------------------------------------------------------------------*
  Name:         MATH_Checksum8Update

  Description:  Updates the 8bit Checksum value with added data.

  Arguments:    context: MATHChecksum8Context structure
                input: Pointer to input data
                length: Length of input data

  Returns:      None.
 *---------------------------------------------------------------------------*/
void MATH_Checksum8Update(MATHChecksum8Context * context, const void *input, u32 length)
{
    u32     sum;

    sum = MATHi_Checksum8Update(input, length);

    sum += *context;
    sum += (sum >> 16);

    *context = (u16)sum;
}

/*---------------------------------------------------------------------------*
  Name:         MATH_CalcChecksum8

  Description:  Calculates the 16bit Checksum.
  
  Arguments:    data: Pointer to input data
                dataLength: Length of input data
  
  Returns:      Checksum value.
 *---------------------------------------------------------------------------*/
u8 MATH_CalcChecksum8(const void *data, u32 dataLength)
{
    u32     sum;

    sum = MATHi_Checksum8Update(data, dataLength);

    sum = (sum >> 8) + (sum & 0xff);
    sum += (sum >> 8);

    return (u8)(~sum);
}