basic_op.h

音频编解码库的具体实现,分析流程清晰,编译测试通过

 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    L_var_out                                                              |
 |             32 bit long signed integer (Word32) whose value falls in the  |
 |             range : 0x8000 0000 <= L_var_out <= 0x7fff ffff.              |
 |                                                                           |
 |   Caution :                                                               |
 |                                                                           |
 |    In some cases the Carry flag has to be cleared or set before using     |
 |    operators which take into account its value.                           |
 |___________________________________________________________________________|
*/ __inline 

Word32 L_msuNs (Word32 L_var3, Word16 var1, Word16 var2)
{
    Word32 L_var_out;

    L_var_out = L_mult (var1, var2);
    L_var_out = L_sub_c (L_var3, L_var_out);
    return (L_var_out);
}

/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : L_add                                                   |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   32 bits addition of the two 32 bits variables (L_var1+L_var2) with      |
 |   overflow control and saturation; the result is set at [phone] when  |
 |   overflow occurs or at -2147483648 when underflow occurs.                |
 |                                                                           |
 |   Complexity weight : 2                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    L_var1   32 bit long signed integer (Word32) whose value falls in the  |
 |             range : 0x8000 0000 <= L_var3 <= 0x7fff ffff.                 |
 |                                                                           |
 |    L_var2   32 bit long signed integer (Word32) whose value falls in the  |
 |             range : 0x8000 0000 <= L_var3 <= 0x7fff ffff.                 |
 |                                                                           |
 |   Outputs :                                                               |
 |                                                                           |
 |    none                                                                   |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    L_var_out                                                              |
 |             32 bit long signed integer (Word32) whose value falls in the  |
 |             range : 0x8000 0000 <= L_var_out <= 0x7fff ffff.              |
 |___________________________________________________________________________|
*/ __inline 

Word32 L_add (Word32 L_var1, Word32 L_var2)
{
    Word32 L_var_out;

    L_var_out = L_var1 + L_var2;

    if (((L_var1 ^ L_var2) & MIN_32) == 0)
    {
        if ((L_var_out ^ L_var1) & MIN_32)
        {
            L_var_out = (L_var1 < 0) ? MIN_32 : MAX_32;
            Overflow = 1;
        }
    }
    return (L_var_out);
}

/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : L_sub                                                   |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   32 bits subtraction of the two 32 bits variables (L_var1-L_var2) with   |
 |   overflow control and saturation; the result is set at [phone] when  |
 |   overflow occurs or at -2147483648 when underflow occurs.                |
 |                                                                           |
 |   Complexity weight : 2                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    L_var1   32 bit long signed integer (Word32) whose value falls in the  |
 |             range : 0x8000 0000 <= L_var3 <= 0x7fff ffff.                 |
 |                                                                           |
 |    L_var2   32 bit long signed integer (Word32) whose value falls in the  |
 |             range : 0x8000 0000 <= L_var3 <= 0x7fff ffff.                 |
 |                                                                           |
 |   Outputs :                                                               |
 |                                                                           |
 |    none                                                                   |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    L_var_out                                                              |
 |             32 bit long signed integer (Word32) whose value falls in the  |
 |             range : 0x8000 0000 <= L_var_out <= 0x7fff ffff.              |
 |___________________________________________________________________________|
*/ __inline 

Word32 L_sub (Word32 L_var1, Word32 L_var2)
{
    Word32 L_var_out;

    L_var_out = L_var1 - L_var2;

    if (((L_var1 ^ L_var2) & MIN_32) != 0)
    {
        if ((L_var_out ^ L_var1) & MIN_32)
        {
            L_var_out = (L_var1 < 0L) ? MIN_32 : MAX_32;
            Overflow = 1;
        }
    }
    return (L_var_out);
}

/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : L_add_c                                                 |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   Performs 32 bits addition of the two 32 bits variables (L_var1+L_var2+C)|
 |   with carry. No saturation. Generate carry and Overflow values. The car- |
 |   ry and overflow values are binary variables which can be tested and as- |
 |   signed values.                                                          |
 |                                                                           |
 |   Complexity weight : 2                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    L_var1   32 bit long signed integer (Word32) whose value falls in the  |
 |             range : 0x8000 0000 <= L_var3 <= 0x7fff ffff.                 |
 |                                                                           |
 |    L_var2   32 bit long signed integer (Word32) whose value falls in the  |
 |             range : 0x8000 0000 <= L_var3 <= 0x7fff ffff.                 |
 |                                                                           |
 |   Outputs :                                                               |
 |                                                                           |
 |    none                                                                   |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    L_var_out                                                              |
 |             32 bit long signed integer (Word32) whose value falls in the  |
 |             range : 0x8000 0000 <= L_var_out <= 0x7fff ffff.              |
 |                                                                           |
 |   Caution :                                                               |
 |                                                                           |
 |    In some cases the Carry flag has to be cleared or set before using     |
 |    operators which take into account its value.                           |
 |___________________________________________________________________________|
*/ __inline 
Word32 L_add_c (Word32 L_var1, Word32 L_var2)
{
    Word32 L_var_out;
    Word32 L_test;
    Flag carry_int = 0;

    L_var_out = L_var1 + L_var2 + Carry;

    L_test = L_var1 + L_var2;

    if ((L_var1 > 0) && (L_var2 > 0) && (L_test < 0))
    {
        Overflow = 1;
        carry_int = 0;
    }
    else
    {
        if ((L_var1 < 0) && (L_var2 < 0))
        {
            if (L_test >= 0)
	    {
                Overflow = 1;
                carry_int = 1;
	    }
            else
	    {
                Overflow = 0;
                carry_int = 1;
	    }
        }
        else
        {
            if (((L_var1 ^ L_var2) < 0) && (L_test >= 0))
            {
                Overflow = 0;
                carry_int = 1;
            }
            else
            {
                Overflow = 0;
                carry_int = 0;
            }
        }
    }

    if (Carry)
    {
        if (L_test == MAX_32)
        {
            Overflow = 1;
            Carry = carry_int;
        }
        else
        {
            if (L_test == (Word32) 0xFFFFFFFFL)
            {
                Carry = 1;
            }
            else
            {
                Carry = carry_int;
            }
        }
    }
    else
    {
        Carry = carry_int;
    }

    return (L_var_out);
}

/*___________________________________________________________________________
 |