Basic, functional-but-extremely-pessimal versions (taken from

uip-0.9/unix/uip_arch.c).

src/proto/uip/uip_arch.c

@@ -0,0 +1,83 @@
+#include <stdint.h>
+#include <byteswap.h>
+#include "uip_arch.h"
+#include "uip.h"
+
+volatile u8_t uip_acc32[4];
+
+void uip_add32 ( u8_t *op32, u16_t op16 ) {
+	* ( ( uint32_t * ) uip_acc32 ) =
+		htonl ( ntohl ( *( ( uint32_t * ) op32 ) )  + op16 );
+}
+
+#define BUF ((uip_tcpip_hdr *)&uip_buf[UIP_LLH_LEN])
+#define IP_PROTO_TCP    6
+
+u16_t uip_chksum(u16_t *sdata, u16_t len) {
+  u16_t acc;
+  
+  for(acc = 0; len > 1; len -= 2) {
+    acc += *sdata;
+    if(acc < *sdata) {
+      /* Overflow, so we add the carry to acc (i.e., increase by
+         one). */
+      ++acc;
+    }
+    ++sdata;
+  }
+
+  /* add up any odd byte */
+  if(len == 1) {
+    acc += htons(((u16_t)(*(u8_t *)sdata)) << 8);
+    if(acc < htons(((u16_t)(*(u8_t *)sdata)) << 8)) {
+      ++acc;
+    }
+  }
+
+  return acc;
+}
+
+u16_t uip_ipchksum(void) {
+  return uip_chksum((u16_t *)&uip_buf[UIP_LLH_LEN], 20);
+}
+
+u16_t uip_tcpchksum(void) {
+  u16_t hsum, sum;
+
+  
+  /* Compute the checksum of the TCP header. */
+  hsum = uip_chksum((u16_t *)&uip_buf[20 + UIP_LLH_LEN], 20);
+
+  /* Compute the checksum of the data in the TCP packet and add it to
+     the TCP header checksum. */
+  sum = uip_chksum((u16_t *)uip_appdata,
+		   (u16_t)(((((u16_t)(BUF->len[0]) << 8) + BUF->len[1]) - 40)));
+
+  if((sum += hsum) < hsum) {
+    ++sum;
+  }
+  
+  if((sum += BUF->srcipaddr[0]) < BUF->srcipaddr[0]) {
+    ++sum;
+  }
+  if((sum += BUF->srcipaddr[1]) < BUF->srcipaddr[1]) {
+    ++sum;
+  }
+  if((sum += BUF->destipaddr[0]) < BUF->destipaddr[0]) {
+    ++sum;
+  }
+  if((sum += BUF->destipaddr[1]) < BUF->destipaddr[1]) {
+    ++sum;
+  }
+  if((sum += (u16_t)htons((u16_t)IP_PROTO_TCP)) < (u16_t)htons((u16_t)IP_PROTO_TCP)) {
+    ++sum;
+  }
+
+  hsum = (u16_t)htons((((u16_t)(BUF->len[0]) << 8) + BUF->len[1]) - 20);
+  
+  if((sum += hsum) < hsum) {
+    ++sum;
+  }
+  
+  return sum;
+}