language: C (gcc-4.7.2)
date: 213 days 19 hours ago
link:
visibility: public 
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#include <stdio.h>
#include <limits.h>
 
#define C_ASSERT(expr) extern char CAssertExtern[(expr)?1:-1]
 
#if UINT_MAX >= 0xFFFFFFFF
typedef unsigned int uint32;
#else
typedef unsigned long uint32;
#endif
typedef unsigned long long uint64;
 
typedef unsigned long ulong;
 
// Make sure uint32=32 bits and uint64=64 bits
C_ASSERT(sizeof(uint32) * CHAR_BIT == 32);
C_ASSERT(sizeof(uint64) * CHAR_BIT == 64);
 
int div64by32eq64(uint64* dividend, uint32 divisor)
{
  uint32 dividendHi = (uint32)(*dividend >> 32);
  uint32 dividendLo = (uint32)*dividend;
  uint32 quotientHi;
  uint32 quotientLo;
 
  if (divisor == 0)
    return 0;
 
  // This can be done as one 32-bit DIV, e.g. "div ecx"
  quotientHi = dividendHi / divisor;
  dividendHi = dividendHi % divisor;
 
  // This can be done as another 32-bit DIV, e.g. "div ecx"
  quotientLo = (uint32)((((uint64)dividendHi << 32) + dividendLo) / divisor);
 
  *dividend = ((uint64)quotientHi << 32) + quotientLo;
 
  return 1;
}
 
int main(void)
{
  static const struct
  {
    uint64 dividend;
    uint32 divisor;
  } testData[] =
  {
    { 1 , 0 },
    { 0xFFFFFFFFFFFFFFFFULL, 1 },
    { 0xFFFFFFFFFFFFFFFFULL, 2 },
    { 0xFFFFFFFF00000000ULL, 0xFFFFFFFFUL },
    { 0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFUL },
  };
  int i;
 
  for (i = 0; i < sizeof(testData)/sizeof(testData[0]); i++)
  {
    uint64 dividend = testData[i].dividend;
    uint32 divisor = testData[i].divisor;
 
    printf("0x%016llX / 0x%08lX = ", dividend, (ulong)divisor);
 
    if (div64by32eq64(&dividend, divisor))
      printf("0x%016llX\n", dividend);
    else
      printf("division by 0 error\n");
  }
 
  return 0;
}