无符号字节的饱和减法/加法

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无符号字节的饱和减法/加法

b = 3; x = 5;
bsub = b - x; // bsub must be 0, not 254

b = 250; x = 10;
badd = b + x; // badd must be 255, not 4

bsub = b - min(b, x);
badd = b + min(255 - b, x);

bsum = a + b;
bsum = (bsum < a || bsum < b) ? 255 : bsum;
bsub = a - b;
bsub = (bsub > a || bsub > b) ? 0 : bsub;

bsub = b - x;
if (bsub > b)
    bsub = 0;
badd = b + x;
if (badd < b)
    badd = 255;
}

u32b sat_addu32b(u32b x, u32b y)
    u32b res = x + y;
    res |= -(res < x);
    return res;
}

uint8_t  sat_addu8b(uint8_t x, uint8_t y)
    uint8_t res = x + y;
    res |= -(res < x);
    return res;
}

u32b sat_subu32b(u32b x, u32b y)
    u32b res = x - y;
    res &= -(res <= x);
    return res;
}

uint8_t sat_subu8b(uint8_t x, uint8_t y)
    uint8_t res = x - y;
    res &= -(res <= x);
    return res;
}

// Addition without overflow
return (b > 255 - a) ? 255 : a + b
// Subtraction without underflow
return (b > a) ? 0 : a - b;

static unsigned char   maxTable[511];
memset(maxTable, 0, 255);           // If smaller, emulates cutoff at zero
maxTable[255]=0;                    // If equal     - return zero
for (int i=0; i<256; i++)
    maxTable[255+i] = i;            // If greater   - return the difference

#define MINUS(A,B)    maxTable[A-B+255];

const unsigned char *result = maxTable+255;
#define MINUS(A,B)    result[A-B];

bsub  = MINUS(13,15); // i.e 13-15 with zero cutoff as requested

// (num1>num2) ? 1 : 0
#define        is_int_biggerNotEqual( num1,num2) ((((__int32)((num2)-(num1)))&0x80000000)>>31)

inline __int32 MIN_INT(__int32 x, __int32 y){   __int32 d=x-y; return y+(d&(d>>31)); }

无符号字节的饱和减法/加法

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