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CRC16 accumulate function
- From: Simon Kallweit <simon dot kallweit at intefo dot ch>
- To: eCos Patches List <ecos-patches at ecos dot sourceware dot org>
- Date: Fri, 20 Mar 2009 16:36:19 +0100
- Subject: CRC16 accumulate function
This patch adds a cyg_crc16_accumulate function which allows to continue
on previous crc calculations. Besides my need for this it also makes the
group of crc function more consistent.
Simon
diff --git a/packages/services/crc/current/ChangeLog b/packages/services/crc/current/ChangeLog
index 8a8342e..d3d07b4 100644
--- a/packages/services/crc/current/ChangeLog
+++ b/packages/services/crc/current/ChangeLog
@@ -1,3 +1,9 @@
+2009-03-20 Simon Kallweit <simon.kallweit@intefo.ch>
+
+ * include/crc.h:
+ * src/crc16.c:
+ Added cyg_crc16_accumulate() to continue on previous crc calculation.
+
2005-08-03 Andrew Lunn <andrew.lunn@ascom.ch>
* tests/crc_test.c: casts to make it gcc 4.0.1 frendly.
diff --git a/packages/services/crc/current/include/crc.h b/packages/services/crc/current/include/crc.h
index 6f20b49..d58d4d1 100644
--- a/packages/services/crc/current/include/crc.h
+++ b/packages/services/crc/current/include/crc.h
@@ -96,6 +96,9 @@ cyg_ether_crc32_accumulate(cyg_uint32 crc, unsigned char *s, int len);
__externC cyg_uint16
cyg_crc16(unsigned char *s, int len);
+__externC cyg_uint16
+cyg_crc16_accumulate(cyg_uint16 crc, unsigned char *s, int len);
+
#endif // _SERVICES_CRC_CRC_H_
diff --git a/packages/services/crc/current/src/crc16.c b/packages/services/crc/current/src/crc16.c
index 7d6fa38..60f810f 100644
--- a/packages/services/crc/current/src/crc16.c
+++ b/packages/services/crc/current/src/crc16.c
@@ -92,13 +92,16 @@ static const cyg_uint16 crc16_tab[] = {
cyg_uint16
cyg_crc16(unsigned char *buf, int len)
{
+ return cyg_crc16_accumulate(0, buf, len);
+}
+
+cyg_uint16
+cyg_crc16_accumulate(cyg_uint16 crc16val, unsigned char *buf, int len)
+{
int i;
- cyg_uint16 cksum;
- cksum = 0;
for (i = 0; i < len; i++) {
- cksum = crc16_tab[((cksum>>8) ^ *buf++) & 0xFF] ^ (cksum << 8);
+ crc16val = crc16_tab[((crc16val>>8) ^ *buf++) & 0xFF] ^ (crc16val << 8);
}
- return cksum;
+ return crc16val;
}
-