patch-2.4.20 linux-2.4.20/arch/x86_64/lib/csum-partial.c

• Lines: 124
• Date: Thu Nov 28 15:53:12 2002
• Orig file: linux-2.4.19/arch/x86_64/lib/csum-partial.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/arch/x86_64/lib/csum-partial.c linux-2.4.20/arch/x86_64/lib/csum-partial.c
@@ -0,0 +1,123 @@
+/*
+ * arch/x86_64/lib/csum-partial.c
+ *
+ * This file contains network checksum routines that are better done
+ * in an architecture-specific manner due to speed.
+ */
+ 
+#include <linux/compiler.h>
+#include <linux/module.h>
+
+/* Better way for this sought */
+static inline unsigned short from64to16(unsigned long x)
+{
+	/* add up 32-bit words for 33 bits */
+	x = (x & 0xffffffff) + (x >> 32);
+	/* add up 16-bit and 17-bit words for 17+c bits */
+	x = (x & 0xffff) + (x >> 16);
+	/* add up 16-bit and 2-bit for 16+c bit */
+	x = (x & 0xffff) + (x >> 16);
+	/* add up carry.. */
+	x = (x & 0xffff) + (x >> 16);
+	return x;
+}
+
+/*
+ * Do a 64-bit checksum on an arbitrary memory area.
+ * Returns a 32bit checksum.
+ *
+ * This isn't a great routine, but it's not _horrible_ either. 
+ * We rely on the compiler to unroll.
+ */
+static inline unsigned do_csum(const unsigned char * buff, int len)
+{
+	int odd, count;
+	unsigned long result = 0;
+
+	if (len <= 0)
+		goto out;
+	odd = 1 & (unsigned long) buff;
+	if (unlikely(odd)) {
+		result = *buff << 8;
+		len--;
+		buff++;
+	}
+	count = len >> 1;		/* nr of 16-bit words.. */
+	if (count) {
+		if (2 & (unsigned long) buff) {
+			result += *(unsigned short *) buff;
+			count--;
+			len -= 2;
+			buff += 2;
+		}
+		count >>= 1;		/* nr of 32-bit words.. */
+		if (count) {
+			if (4 & (unsigned long) buff) {
+				result += *(unsigned int *) buff;
+				count--;
+				len -= 4;
+				buff += 4;
+			}
+			count >>= 1;	/* nr of 64-bit words.. */
+			if (count) {
+				unsigned long zero = 0; 
+				do {
+					asm("  addq %1,%0\n"
+					    "  adcq %2,%0\n" 
+					    : "=r" (result)
+					    : "m"  (*buff), "r" (zero),  "0" (result));
+					count--;
+					buff += 8;
+				} while (count);
+				result = (result & 0xffffffff) + (result >> 32);
+			}
+			if (len & 4) {
+				result += *(unsigned int *) buff;
+				buff += 4;
+			}
+		}
+		if (len & 2) {
+			result += *(unsigned short *) buff;
+			buff += 2;
+		}
+	}
+	if (len & 1)
+		result += *buff;
+	result = from64to16(result);
+	if (unlikely(odd))
+		return ((result >> 8) & 0xff) | ((result & 0xff) << 8);
+out:
+	return result;
+}
+
+/*
+ * computes the checksum of a memory block at buff, length len,
+ * and adds in "sum" (32-bit)
+ *
+ * returns a 32-bit number suitable for feeding into itself
+ * or csum_tcpudp_magic
+ *
+ * this function must be called with even lengths, except
+ * for the last fragment, which may be odd
+ *
+ * it's best to have buff aligned on a 64-bit boundary
+ */
+unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum)
+{
+	unsigned result = do_csum(buff, len);
+
+	/* add in old sum, and carry.. */
+	asm("addl %1,%0\n\t"
+	    "adcl $0,%0" : "=r" (result) : "r" (sum), "0" (result)); 
+	return result;
+}
+
+/*
+ * this routine is used for miscellaneous IP-like checksums, mainly
+ * in icmp.c
+ */
+unsigned short ip_compute_csum(unsigned char * buff, int len)
+{
+	return ~csum_partial(buff,len,0); 
+}
+