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libs/libc/crc16: add some comments for crc16ccitt

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The search table of ccitt should describe more algorithm details:

- CRC-16/CCITT, CRC-16/CCITT-TRUE, CRC-16/KERMIT
initial seed: 0x0000, xor output: 0x0000

: width=16
: poly=0x1021
: init=0x0000
: refin=true
: refout=true
: xorout=0x0000
: check=0x2189
: residue=0x0000
: name="CRC-16/KERMIT"

https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-kermit

Signed-off-by: chao an <anchao.archer@bytedance.com>
This commit is contained in:
chao an
2025-04-07 09:02:01 +08:00
committed by Lup Yuen Lee
parent c061bb08c4
commit 4e2f6eabb3
2 changed files with 40 additions and 0 deletions
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include/nuttx/crc16.h
+20
View File
@@ -77,6 +77,16 @@ uint16_t crc16(FAR const uint8_t *src, size_t len);
* Continue 16-bit CRC-CCITT calculation on a part of the buffer using the
* polynomial x^16+x^12+x^5+1.
*
* This function is able to calculate any CRC that uses 0x1021 as it
* polynomial and requires reflecting both the input and the output.
* The following checksums can, among others, be calculated by this
* function, depending on the value provided for the initial seed and the
* value the final calculated CRC is XORed with:
*
* - CRC-16/CCITT, CRC-16/CCITT-TRUE, CRC-16/KERMIT
* https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-kermit
* initial seed: 0x0000, xor output: 0x0000
*
****************************************************************************/
uint16_t crc16ccittpart(FAR const uint8_t *src, size_t len,
@@ -89,6 +99,16 @@ uint16_t crc16ccittpart(FAR const uint8_t *src, size_t len,
* Return a 16-bit CRC-CCITT of the contents of the 'src' buffer, length
* 'len' using the polynomial x^16+x^12+x^5+1.
*
* This function is able to calculate any CRC that uses 0x1021 as it
* polynomial and requires reflecting both the input and the output.
* The following checksums can, among others, be calculated by this
* function, depending on the value provided for the initial seed and the
* value the final calculated CRC is XORed with:
*
* - CRC-16/CCITT, CRC-16/CCITT-TRUE, CRC-16/KERMIT
* https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-kermit
* initial seed: 0x0000, xor output: 0x0000
*
****************************************************************************/
uint16_t crc16ccitt(FAR const uint8_t *src, size_t len);
libs/libc/misc/lib_crc16ccitt.c
+20
View File
@@ -82,6 +82,16 @@ static uint16_t crc16ccitt_tab[256] =
* Continue 16-bit CRC-CCITT calculation on a part of the buffer using the
* polynomial x^16+x^12+x^5+1.
*
* This function is able to calculate any CRC that uses 0x1021 as it
* polynomial and requires reflecting both the input and the output.
* The following checksums can, among others, be calculated by this
* function, depending on the value provided for the initial seed and the
* value the final calculated CRC is XORed with:
*
* - CRC-16/CCITT, CRC-16/CCITT-TRUE, CRC-16/KERMIT
* https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-kermit
* initial seed: 0x0000, xor output: 0x0000
*
****************************************************************************/
uint16_t crc16ccittpart(FAR const uint8_t *src, size_t len,
@@ -105,6 +115,16 @@ uint16_t crc16ccittpart(FAR const uint8_t *src, size_t len,
* Return a 16-bit CRC-CCITT of the contents of the 'src' buffer, length
* 'len' using the polynomial x^16+x^12+x^5+1.
*
* This function is able to calculate any CRC that uses 0x1021 as it
* polynomial and requires reflecting both the input and the output.
* The following checksums can, among others, be calculated by this
* function, depending on the value provided for the initial seed and the
* value the final calculated CRC is XORed with:
*
* - CRC-16/CCITT, CRC-16/CCITT-TRUE, CRC-16/KERMIT
* https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-kermit
* initial seed: 0x0000, xor output: 0x0000
*
****************************************************************************/
uint16_t crc16ccitt(FAR const uint8_t *src, size_t len)