1 files changed, 130 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/SNIP/crc-16f.c b/reference/C/CONTRIB/SNIP/crc-16f.c
new file mode 100755
index 0000000..ad45a4a
--- /dev/null
+++ b/reference/C/CONTRIB/SNIP/crc-16f.c
@@ -0,0 +1,130 @@
+/*
+ * Calculate, intelligently, the CRC of a dataset incrementally given a
+ * buffer full at a time.
+ * Initialize crc to 0 for XMODEM, -1 for CCITT.
+ *
+ * Usage:
+ *   newcrc = updcrc( oldcrc, bufadr, buflen )
+ *        unsigned int oldcrc, buflen;
+ *        char *bufadr;
+ *
+ * Compile with -DTEST to generate program that prints CRC of stdin to stdout.
+ * Compile with -DMAKETAB to print values for crctab to stdout
+ */
+
+    /* the CRC polynomial. This is used by XMODEM (almost CCITT).
+     * If you change P, you must change crctab[]'s initial value to what is
+     * printed by initcrctab()
+     */
+#define   P    0x1021
+
+    /* number of bits in CRC: don't change it. */
+#define W 16
+
+    /* this the number of bits per char: don't change it. */
+#define B 8
+
+static unsigned short crctab[1<<B] = { /* as calculated by initcrctab() */
+    0x0000,  0x1021,  0x2042,  0x3063,  0x4084,  0x50a5,  0x60c6,  0x70e7,
+    0x8108,  0x9129,  0xa14a,  0xb16b,  0xc18c,  0xd1ad,  0xe1ce,  0xf1ef,
+    0x1231,  0x0210,  0x3273,  0x2252,  0x52b5,  0x4294,  0x72f7,  0x62d6,
+    0x9339,  0x8318,  0xb37b,  0xa35a,  0xd3bd,  0xc39c,  0xf3ff,  0xe3de,
+    0x2462,  0x3443,  0x0420,  0x1401,  0x64e6,  0x74c7,  0x44a4,  0x5485,
+    0xa56a,  0xb54b,  0x8528,  0x9509,  0xe5ee,  0xf5cf,  0xc5ac,  0xd58d,
+    0x3653,  0x2672,  0x1611,  0x0630,  0x76d7,  0x66f6,  0x5695,  0x46b4,
+    0xb75b,  0xa77a,  0x9719,  0x8738,  0xf7df,  0xe7fe,  0xd79d,  0xc7bc,
+    0x48c4,  0x58e5,  0x6886,  0x78a7,  0x0840,  0x1861,  0x2802,  0x3823,
+    0xc9cc,  0xd9ed,  0xe98e,  0xf9af,  0x8948,  0x9969,  0xa90a,  0xb92b,
+    0x5af5,  0x4ad4,  0x7ab7,  0x6a96,  0x1a71,  0x0a50,  0x3a33,  0x2a12,
+    0xdbfd,  0xcbdc,  0xfbbf,  0xeb9e,  0x9b79,  0x8b58,  0xbb3b,  0xab1a,
+    0x6ca6,  0x7c87,  0x4ce4,  0x5cc5,  0x2c22,  0x3c03,  0x0c60,  0x1c41,
+    0xedae,  0xfd8f,  0xcdec,  0xddcd,  0xad2a,  0xbd0b,  0x8d68,  0x9d49,
+    0x7e97,  0x6eb6,  0x5ed5,  0x4ef4,  0x3e13,  0x2e32,  0x1e51,  0x0e70,
+    0xff9f,  0xefbe,  0xdfdd,  0xcffc,  0xbf1b,  0xaf3a,  0x9f59,  0x8f78,
+    0x9188,  0x81a9,  0xb1ca,  0xa1eb,  0xd10c,  0xc12d,  0xf14e,  0xe16f,
+    0x1080,  0x00a1,  0x30c2,  0x20e3,  0x5004,  0x4025,  0x7046,  0x6067,
+    0x83b9,  0x9398,  0xa3fb,  0xb3da,  0xc33d,  0xd31c,  0xe37f,  0xf35e,
+    0x02b1,  0x1290,  0x22f3,  0x32d2,  0x4235,  0x5214,  0x6277,  0x7256,
+    0xb5ea,  0xa5cb,  0x95a8,  0x8589,  0xf56e,  0xe54f,  0xd52c,  0xc50d,
+    0x34e2,  0x24c3,  0x14a0,  0x0481,  0x7466,  0x6447,  0x5424,  0x4405,
+    0xa7db,  0xb7fa,  0x8799,  0x97b8,  0xe75f,  0xf77e,  0xc71d,  0xd73c,
+    0x26d3,  0x36f2,  0x0691,  0x16b0,  0x6657,  0x7676,  0x4615,  0x5634,
+    0xd94c,  0xc96d,  0xf90e,  0xe92f,  0x99c8,  0x89e9,  0xb98a,  0xa9ab,
+    0x5844,  0x4865,  0x7806,  0x6827,  0x18c0,  0x08e1,  0x3882,  0x28a3,
+    0xcb7d,  0xdb5c,  0xeb3f,  0xfb1e,  0x8bf9,  0x9bd8,  0xabbb,  0xbb9a,
+    0x4a75,  0x5a54,  0x6a37,  0x7a16,  0x0af1,  0x1ad0,  0x2ab3,  0x3a92,
+    0xfd2e,  0xed0f,  0xdd6c,  0xcd4d,  0xbdaa,  0xad8b,  0x9de8,  0x8dc9,
+    0x7c26,  0x6c07,  0x5c64,  0x4c45,  0x3ca2,  0x2c83,  0x1ce0,  0x0cc1,
+    0xef1f,  0xff3e,  0xcf5d,  0xdf7c,  0xaf9b,  0xbfba,  0x8fd9,  0x9ff8,
+    0x6e17,  0x7e36,  0x4e55,  0x5e74,  0x2e93,  0x3eb2,  0x0ed1,  0x1ef0
+    };
+
+unsigned short updcrc(unsigned short icrc,
+                      unsigned char *icp,
+                      unsigned int icnt )
+{
+      register unsigned short crc = icrc;
+      register unsigned char *cp = icp;
+      register unsigned int cnt = icnt;
+
+      while( cnt-- )
+            crc = (crc<<B) ^ crctab[(crc>>(W-B)) ^ *cp++];
+
+      return( crc );
+}
+
+#ifdef MAKETAB
+main()
+{
+      initcrctab();
+}
+
+initcrctab()
+{
+      register  b, v, i;
+
+      for( b = 0; b <= (1<<B)-1; ++b )
+      {
+            for( v = b<<(W-B), i = B; --i >= 0; )
+                  v = v&0x8000 ? (v<<1)^P : v<<1;
+            crctab[b] = v;
+
+            printf( "0x%04x,", v & 0xFFFF );
+            if( (b&7) == 7 )
+                  printf("\n" );
+            else  printf("  ");
+      }
+}
+#endif
+
+#ifdef TEST
+
+#include <stdio.h>
+#include <fcntl.h>
+
+#define MAXBUF 4096
+
+void main(int argc, char **argv)
+{
+      int fd = 0;
+      int nr;
+      char buf[MAXBUF];
+      unsigned short crc;
+
+      if( argc > 1 )
+      {
+            if( (fd = open( argv[1], O_RDONLY )) < 0 )
+            {
+                  perror( argv[1] );
+                  exit( -1 );
+            }
+      }
+      crc = 0;
+      while( (nr = read( fd, buf, MAXBUF )) > 0 )
+            crc = updcrc( crc, buf, nr );
+      printf( "%04x\n", crc );
+      if( nr != 0 )
+            perror( "reading" );
+}
+
+#endif