#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;
}