xiaoxiang781216 commented on code in PR #15570:
URL: https://github.com/apache/nuttx/pull/15570#discussion_r1917600126
##########
include/nuttx/sensors/msxxxx_crc4.h:
##########
@@ -44,41 +44,40 @@ static uint8_t msxxxx_crc4(FAR uint16_t *src,
uint16_t crcmask)
{
uint16_t cnt;
- uint16_t n_rem;
- uint16_t crc_read;
+ uint16_t n_rem; /* CRC remainder */
+ uint16_t crc_read; /* Original value of the CRC */
uint8_t n_bit;
n_rem = 0x00;
- crc_read = src[crcndx];
- src[crcndx] &= ~crcmask;
+ crc_read = src[crcndx]; /* Save read CRC */
+ src[crcndx] &= ~crcmask; /* CRC byte is replaced by 0 */
- for (cnt = 0; cnt < 16; cnt++)
+ for (cnt = 0; cnt < 16; cnt++) /* Operation is performed on bytes */
{
if (cnt % 2 == 1)
{
- n_rem ^= src[cnt >> 1] & 0x00ff;
+ n_rem ^= (uint16_t)((src[cnt >> 1]) & 0x00ff);
}
else
{
- n_rem ^= src[cnt >> 1] >> 8;
+ n_rem ^= (uint16_t)(src[cnt >> 1] >> 8);
}
for (n_bit = 8; n_bit > 0; n_bit--)
{
- if (n_rem & (0x8000) != 0)
+ if (n_rem & (0x8000))
{
n_rem = (n_rem << 1) ^ 0x3000;
}
else
{
- n_rem <<= 1;
+ n_rem = (n_rem << 1);
Review Comment:
why change
##########
include/nuttx/sensors/msxxxx_crc4.h:
##########
@@ -44,41 +44,40 @@ static uint8_t msxxxx_crc4(FAR uint16_t *src,
uint16_t crcmask)
{
uint16_t cnt;
- uint16_t n_rem;
- uint16_t crc_read;
+ uint16_t n_rem; /* CRC remainder */
+ uint16_t crc_read; /* Original value of the CRC */
uint8_t n_bit;
n_rem = 0x00;
- crc_read = src[crcndx];
- src[crcndx] &= ~crcmask;
+ crc_read = src[crcndx]; /* Save read CRC */
+ src[crcndx] &= ~crcmask; /* CRC byte is replaced by 0 */
- for (cnt = 0; cnt < 16; cnt++)
+ for (cnt = 0; cnt < 16; cnt++) /* Operation is performed on bytes */
{
if (cnt % 2 == 1)
{
- n_rem ^= src[cnt >> 1] & 0x00ff;
+ n_rem ^= (uint16_t)((src[cnt >> 1]) & 0x00ff);
}
else
{
- n_rem ^= src[cnt >> 1] >> 8;
+ n_rem ^= (uint16_t)(src[cnt >> 1] >> 8);
Review Comment:
ditto
##########
include/nuttx/sensors/msxxxx_crc4.h:
##########
@@ -44,41 +44,40 @@ static uint8_t msxxxx_crc4(FAR uint16_t *src,
uint16_t crcmask)
{
uint16_t cnt;
- uint16_t n_rem;
- uint16_t crc_read;
+ uint16_t n_rem; /* CRC remainder */
+ uint16_t crc_read; /* Original value of the CRC */
uint8_t n_bit;
n_rem = 0x00;
- crc_read = src[crcndx];
- src[crcndx] &= ~crcmask;
+ crc_read = src[crcndx]; /* Save read CRC */
+ src[crcndx] &= ~crcmask; /* CRC byte is replaced by 0 */
- for (cnt = 0; cnt < 16; cnt++)
+ for (cnt = 0; cnt < 16; cnt++) /* Operation is performed on bytes */
{
if (cnt % 2 == 1)
{
- n_rem ^= src[cnt >> 1] & 0x00ff;
+ n_rem ^= (uint16_t)((src[cnt >> 1]) & 0x00ff);
Review Comment:
why need the cast
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