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Make the CRC-16 table static (as it's not used outside "crc16.c") and 

"const" (as nothing writes to it).

"len" is unsigned, so it can never be < 0 - it can only be 0 or != 0.

svn path=/trunk/; revision=11244
This commit is contained in:
Guy Harris 2004-06-26 09:45:27 +00:00
parent a43ec4bd7d
commit a0414ee1ab
1 changed files with 9 additions and 7 deletions
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16
crc16.c
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@ -3,7 +3,7 @@
* *
* 2004 Richard van der Hoff <richardv@mxtelecom.com> * 2004 Richard van der Hoff <richardv@mxtelecom.com>
* *
* $Id: crc16.c,v 1.1 2004/06/25 06:31:46 sahlberg Exp $ * $Id: crc16.c,v 1.2 2004/06/26 09:45:27 guy Exp $
* *
* Ethereal - Network traffic analyzer * Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@xxxxxxxxxxxx> * By Gerald Combs <gerald@xxxxxxxxxxxx>
@ -67,7 +67,7 @@
/* */ /* */
/*****************************************************************/ /*****************************************************************/
guint crc16_ccitt_table[256] = static const guint crc16_ccitt_table[256] =
{ {
0x0000, 0x1189, 0x2312, 0x329B, 0x4624, 0x57AD, 0x6536, 0x74BF, 0x0000, 0x1189, 0x2312, 0x329B, 0x4624, 0x57AD, 0x6536, 0x74BF,
0x8C48, 0x9DC1, 0xAF5A, 0xBED3, 0xCA6C, 0xDBE5, 0xE97E, 0xF8F7, 0x8C48, 0x9DC1, 0xAF5A, 0xBED3, 0xCA6C, 0xDBE5, 0xE97E, 0xF8F7,
@ -117,7 +117,7 @@ static guint16 crc16_unreflected(const unsigned char *buf, guint len,
faster. We just ignore the top 16 bits and let them do what they want. */ faster. We just ignore the top 16 bits and let them do what they want. */
guint crc16 = (guint)crc_in;; guint crc16 = (guint)crc_in;;
while( len-- > 0 ) while( len-- != 0 )
crc16 = table[(crc16 ^ *buf++) & 0xff] ^ (crc16 << 8); crc16 = table[(crc16 ^ *buf++) & 0xff] ^ (crc16 << 8);
return (guint16)crc16; return (guint16)crc16;
@ -128,16 +128,18 @@ static guint16 crc16_reflected(const unsigned char *buf, guint len,
guint16 crc_in, const guint table[]) guint16 crc_in, const guint table[])
{ {
/* we use guints, rather than guint16s, as they are likely to be /* we use guints, rather than guint16s, as they are likely to be
faster. We just ignore the top 16 bits and let them do what they want. */ faster. We just ignore the top 16 bits and let them do what they want.
guint crc16 = (guint)crc_in;; XXX - does any time saved not zero-extending guint16's to 32 bits
into a register outweigh any increased cache footprint from the
larger CRC table? */
guint crc16 = (guint)crc_in;
while( len-- > 0 ) while( len-- != 0 )
crc16 = table[(crc16 ^ *buf++) & 0xff] ^ (crc16 >> 8); crc16 = table[(crc16 ^ *buf++) & 0xff] ^ (crc16 >> 8);
return (guint16)crc16; return (guint16)crc16;
} }
guint16 crc16_ccitt(const unsigned char *buf, guint len) guint16 crc16_ccitt(const unsigned char *buf, guint len)
{ {
return crc16_reflected(buf,len,crc16_ccitt_start,crc16_ccitt_table) return crc16_reflected(buf,len,crc16_ccitt_start,crc16_ccitt_table)