Bit Manipulation Techniques

#include 

uint32_t reg = 0xDEADBEEFu;

/* AND (&): clear bits / mask extraction */
uint32_t lower_byte = reg & 0x000000FFu;     /* = 0xEF */

/* OR (|): set bits */
uint32_t with_bit5  = reg | (1u << 5u);       /* set bit 5 */

/* XOR (^): toggle bits */
uint32_t toggled    = reg ^ (1u << 5u);       /* toggle bit 5 */

/* NOT (~): bitwise complement */
uint32_t inverted   = ~reg;                   /* flip all bits */

/* Shifts: always prefer unsigned operands (MISRA Rule 12.2) */
uint32_t shifted_l  = 1u << 8u;              /* = 0x100 */
uint32_t shifted_r  = reg >> 4u;             /* logical right shift (unsigned) */
/* NEVER right-shift signed integers: result is implementation-defined */

/* Compound assignment */
reg &= ~(1u << 5u);   /* clear bit 5 */
reg |=  (1u << 5u);   /* set bit 5 */
reg ^=  (1u << 5u);   /* toggle bit 5 */

#include 

/* Extract a multi-bit field from a register */
/* Field: bits [10:5] = ADC result (6-bit value) */
#define ADC_FIELD_SHIFT  5u
#define ADC_FIELD_WIDTH  6u
#define ADC_FIELD_MASK   ((1u << ADC_FIELD_WIDTH) - 1u)   /* = 0x3Fu */

uint32_t reg_value = 0x000003E0u;  /* bits [10:5] = 0b011111 = 31 */
uint32_t adc_value = (reg_value >> ADC_FIELD_SHIFT) & ADC_FIELD_MASK;
/* adc_value = (0x3E0 >> 5) & 0x3F = 0x1F = 31 */

/* Insert a value into a field (read-modify-write) */
void set_adc_channel(volatile uint32_t *reg, uint8_t channel)
{
    const uint32_t CH_SHIFT = 8u;
    const uint32_t CH_MASK  = 0x0Fu;         /* 4-bit channel field */
    *reg = (*reg & ~(CH_MASK << CH_SHIFT))    /* clear field */
         | ((channel & CH_MASK) << CH_SHIFT); /* insert new value */
}

/* Count set bits (population count) — useful for CAN DLC validation */
uint8_t popcount8(uint8_t x)
{
    x = x - ((x >> 1u) & 0x55u);
    x = (x & 0x33u) + ((x >> 2u) & 0x33u);
    return (uint8_t)((x + (x >> 4u)) & 0x0Fu);
}

/* Check if a value is a power of two */
static inline boolean is_power_of_two(uint32_t x) {
    return (boolean)((x != 0u) && ((x & (x - 1u)) == 0u));
}