int64.c

/*
 * Handling of the int64 and uint64 types. Done in 32-bit integers,
 * for (pre-C99) portability. Hopefully once C99 becomes widespread
 * we can kiss this lot goodbye...
 */

#include <assert.h>
#include <string.h>

#include "int64.h"

uint64 uint64_div10(uint64 x, int *remainder)
{
  uint64 y;
  unsigned int rem, r2;
  y.hi = x.hi / 10;
  y.lo = x.lo / 10;
  rem = x.lo % 10;
  /*
   * Now we have to add in the remainder left over from x.hi.
   */
  r2 = x.hi % 10;
  y.lo += r2 * 429496729;
  rem += r2 * 6;
  y.lo += rem / 10;
  rem %= 10;

  if (remainder)
    *remainder = rem;
  return y;
}

void uint64_decimal(uint64 x, char *buffer)
{
  char buf[20];
  int start = 20;
  int d;

  do {
    x = uint64_div10(x, &d);
    assert(start > 0);
    buf[--start] = d + '0';
  } while (x.hi || x.lo);

  memcpy(buffer, buf + start, sizeof(buf) - start);
  buffer[sizeof(buf) - start] = '\0';
}

uint64 uint64_make(unsigned long hi, unsigned long lo)
{
  uint64 y;
  y.hi = hi & 0xFFFFFFFFU;
  y.lo = lo & 0xFFFFFFFFU;
  return y;
}

uint64 uint64_add(uint64 x, uint64 y)
{
  x.lo = (x.lo + y.lo) & 0xFFFFFFFFU;
  x.hi += y.hi + (x.lo < y.lo ? 1 : 0);
  return x;
}

uint64 uint64_add32(uint64 x, unsigned long y)
{
  uint64 yy;
  yy.hi = 0;
  yy.lo = y;
  return uint64_add(x, yy);
}

int uint64_compare(uint64 x, uint64 y)
{
  if (x.hi != y.hi)
    return x.hi < y.hi ? -1 : +1;
  if (x.lo != y.lo)
    return x.lo < y.lo ? -1 : +1;
  return 0;
}

uint64 uint64_subtract(uint64 x, uint64 y)
{
  x.lo = (x.lo - y.lo) & 0xFFFFFFFFU;
  x.hi = (x.hi - y.hi - (x.lo > (y.lo ^ 0xFFFFFFFFU) ? 1 : 0)) & 0xFFFFFFFFU;
  return x;
}

double uint64_to_double(uint64 x)
{
  return (4294967296.0 * x.hi) + (double)x.lo;
}

uint64 uint64_shift_right(uint64 x, int shift)
{
  if (shift < 32) {
    x.lo >>= shift;
    x.lo |= (x.hi << (32 - shift)) & 0xFFFFFFFFU;
    x.hi >>= shift;
  } else {
    x.lo = x.hi >> (shift - 32);
    x.hi = 0;
  }
  return x;
}

uint64 uint64_shift_left(uint64 x, int shift)
{
  if (shift < 32) {
    x.hi = (x.hi << shift) & 0xFFFFFFFFU;
    x.hi |= (x.lo >> (32 - shift));
    x.lo = (x.lo << shift) & 0xFFFFFFFFU;
  } else {
    x.hi = (x.lo << (shift - 32)) & 0xFFFFFFFFU;
    x.lo = 0;
  }
  return x;
}

uint64 uint64_from_decimal(char *str)
{
  uint64 ret;
  ret.hi = ret.lo = 0;
  while (*str >= '0' && *str <= '9') {
    ret = uint64_add(uint64_shift_left(ret, 3), uint64_shift_left(ret, 1));
    ret = uint64_add32(ret, *str - '0');
    str++;
  }
  return ret;
}

#ifdef TESTMODE

#include <stdio.h>

int main(void)
{
  uint64 x, y, z;
  char buf[80];

  x = uint64_make(0x3456789AUL, 0xDEF01234UL);
  printf("%08lx.%08lx\n", x.hi, x.lo);
  uint64_decimal(x, buf);
  printf("%s\n", buf);

  y = uint64_add32(x, 0xFFFFFFFFU);
  printf("%08lx.%08lx\n", y.hi, y.lo);
  uint64_decimal(y, buf);
  printf("%s\n", buf);

  z = uint64_subtract(y, x);
  printf("%08lx.%08lx\n", z.hi, z.lo);
  uint64_decimal(z, buf);
  printf("%s\n", buf);

  z = uint64_subtract(x, y);
  printf("%08lx.%08lx\n", z.hi, z.lo);
  uint64_decimal(z, buf);
  printf("%s\n", buf);

  y = uint64_shift_right(x, 4);
  printf("%08lx.%08lx\n", y.hi, y.lo);

  y = uint64_shift_right(x, 36);
  printf("%08lx.%08lx\n", y.hi, y.lo);

  y = uint64_shift_left(x, 4);
  printf("%08lx.%08lx\n", x.hi, x.lo);

  y = uint64_shift_left(x, 36);
  printf("%08lx.%08lx\n", x.hi, x.lo);

  return 0;
}
#endif