/*
 * arch/sh/lib/csum_parial.c
 *
 * This file contains network checksum routines that are better done
 * in an architecture-specific manner due to speed..
 */

#undef DEBUG

#include <linux/config.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <asm/byteorder.h>
#include <asm/uaccess.h>

static inline unsigned short from64to16(unsigned long 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;
}

static inline unsigned short foldto16(unsigned long x)
{
        /* add up 16-bit for 17 bits */
        x = (x & 0xffff) + (x >> 16);
        /* add up carry.. */
        x = (x & 0xffff) + (x >> 16);
        return x;
}

static inline unsigned short myfoldto16(unsigned long long x)
{
        /* Fold down to 32-bits so we don't loose in the typedef-less
           network stack.  */
        /* 64 to 33 */
        x = (x & 0xffffffff) + (x >> 32);
        /* 33 to 32 */
        x = (x & 0xffffffff) + (x >> 32);

        /* add up 16-bit for 17 bits */
        x = (x & 0xffff) + (x >> 16);
        /* add up carry.. */
        x = (x & 0xffff) + (x >> 16);
        return x;
}

#define odd(x) ((x)&1)
#define U16(x) ntohs(x)

static unsigned long do_csum(const unsigned char *buff, int len)
{
        int odd, count;
        unsigned long result = 0;

        pr_debug("do_csum buff %p, len %d (0x%x)\n", buff, len, len);
#ifdef DEBUG
        for (i = 0; i < len; i++) {
                if ((i % 26) == 0)
                        printk("\n");
                printk("%02X ", buff[i]);
        }
#endif

        if (len <= 0)
                goto out;

        odd = 1 & (unsigned long) buff;
        if (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) {
                        unsigned long carry = 0;
                        do {
                                unsigned long w = *(unsigned long *) buff;
                                buff += 4;
                                count--;
                                result += carry;
                                result += w;
                                carry = (w > result);
                        } while (count);
                        result += carry;
                        result = (result & 0xffff) + (result >> 16);
                }
                if (len & 2) {
                        result += *(unsigned short *) buff;
                        buff += 2;
                }
        }
        if (len & 1)
                result += *buff;
        result = foldto16(result);
        if (odd)
                result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);

        pr_debug("\nCHECKSUM is 0x%x\n", result);

      out:
        return result;
}

/* computes the checksum of a memory block at buff, length len,
   and adds in "sum" (32-bit)  */
unsigned int csum_partial(const unsigned char *buff, int len, unsigned int sum)
{
        unsigned long long result = do_csum(buff, len);

        /* add in old sum, and carry.. */
        result += sum;
        /* 32+c bits -> 32 bits */
        result = (result & 0xffffffff) + (result >> 32);

        pr_debug("csum_partial, buff %p len %d sum 0x%x result=0x%016Lx\n",
                buff, len, sum, result);

        return result;
}

/* Copy while checksumming, otherwise like csum_partial.  */
unsigned int
csum_partial_copy(const char *src, char *dst, int len, unsigned int sum)
{
        sum = csum_partial(src, len, sum);
        memcpy(dst, src, len);

        return sum;
}

/* Copy from userspace and compute checksum.  If we catch an exception
   then zero the rest of the buffer.  */
unsigned int
csum_partial_copy_from_user(const char *src, char *dst, int len,
                            unsigned int sum, int *err_ptr)
{
        int missing;

        pr_debug
            ("csum_partial_copy_from_user src %p, dest %p, len %d, sum %08x, err_ptr %p\n",
             src, dst, len, sum, err_ptr);
        missing = copy_from_user(dst, src, len);
        pr_debug("  access_ok %d\n", __access_ok((unsigned long) src, len));
        pr_debug("  missing %d\n", missing);
        if (missing) {
                memset(dst + len - missing, 0, missing);
                *err_ptr = -EFAULT;
        }

        return csum_partial(dst, len, sum);
}

/* Copy to userspace and compute checksum.  */
unsigned int
csum_partial_copy_to_user(const char *src, char *dst, int len,
                          unsigned int sum, int *err_ptr)
{
        sum = csum_partial(src, len, sum);

        if (copy_to_user(dst, src, len))
                *err_ptr = -EFAULT;

        return sum;
}

/*
 *      This is a version of ip_compute_csum() optimized for IP headers,
 *      which always checksum on 4 octet boundaries.
 */
unsigned short ip_fast_csum(unsigned char *iph, unsigned int ihl)
{
        pr_debug("ip_fast_csum %p,%d\n", iph, ihl);

        return ~do_csum(iph, ihl * 4);
}

unsigned int csum_tcpudp_nofold(unsigned long saddr,
                                unsigned long daddr,
                                unsigned short len,
                                unsigned short proto, unsigned int sum)
{
        unsigned long long result;

        pr_debug("ntohs(0x%x)=0x%x\n", 0xdead, ntohs(0xdead));
        pr_debug("htons(0x%x)=0x%x\n", 0xdead, htons(0xdead));

        result = ((unsigned long long) saddr +
                  (unsigned long long) daddr +
                  (unsigned long long) sum +
                  ((unsigned long long) ntohs(len) << 16) +
                  ((unsigned long long) proto << 8));

        /* Fold down to 32-bits so we don't loose in the typedef-less
           network stack.  */
        /* 64 to 33 */
        result = (result & 0xffffffff) + (result >> 32);
        /* 33 to 32 */
        result = (result & 0xffffffff) + (result >> 32);

        pr_debug("%s saddr %x daddr %x len %x proto %x sum %x result %08Lx\n",
                __FUNCTION__, saddr, daddr, len, proto, sum, result);

        return result;
}

// Post SIM:
unsigned int
csum_partial_copy_nocheck(const char *src, char *dst, int len, unsigned int sum)
{
        //  unsigned dummy;
        pr_debug("csum_partial_copy_nocheck src %p dst %p len %d\n", src, dst,
                len);

        return csum_partial_copy(src, dst, len, sum);
}