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lib/div64.c 2.3 KB
1da177e4c   Linus Torvalds   Linux-2.6.12-rc2
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  /*
   * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
   *
   * Based on former do_div() implementation from asm-parisc/div64.h:
   *	Copyright (C) 1999 Hewlett-Packard Co
   *	Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
   *
   *
   * Generic C version of 64bit/32bit division and modulo, with
   * 64bit result and 32bit remainder.
   *
   * The fast case for (n>>32 == 0) is handled inline by do_div(). 
   *
   * Code generated for this function might be very inefficient
   * for some CPUs. __div64_32() can be overridden by linking arch-specific
   * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S.
   */
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  #include <linux/module.h>
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  #include <linux/math64.h>
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  /* Not needed on 64bit architectures */
  #if BITS_PER_LONG == 32
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  uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
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  {
  	uint64_t rem = *n;
  	uint64_t b = base;
  	uint64_t res, d = 1;
  	uint32_t high = rem >> 32;
  
  	/* Reduce the thing a bit first */
  	res = 0;
  	if (high >= base) {
  		high /= base;
  		res = (uint64_t) high << 32;
  		rem -= (uint64_t) (high*base) << 32;
  	}
  
  	while ((int64_t)b > 0 && b < rem) {
  		b = b+b;
  		d = d+d;
  	}
  
  	do {
  		if (rem >= b) {
  			rem -= b;
  			res += d;
  		}
  		b >>= 1;
  		d >>= 1;
  	} while (d);
  
  	*n = res;
  	return rem;
  }
  
  EXPORT_SYMBOL(__div64_32);
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  #ifndef div_s64_rem
  s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
  {
  	u64 quotient;
  
  	if (dividend < 0) {
  		quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
  		*remainder = -*remainder;
  		if (divisor > 0)
  			quotient = -quotient;
  	} else {
  		quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
  		if (divisor < 0)
  			quotient = -quotient;
  	}
  	return quotient;
  }
  EXPORT_SYMBOL(div_s64_rem);
  #endif
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  /* 64bit divisor, dividend and result. dynamic precision */
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  #ifndef div64_u64
  u64 div64_u64(u64 dividend, u64 divisor)
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  {
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  	u32 high, d;
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  	high = divisor >> 32;
  	if (high) {
  		unsigned int shift = fls(high);
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  		d = divisor >> shift;
  		dividend >>= shift;
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  	} else
  		d = divisor;
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  	return div_u64(dividend, d);
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  }
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  EXPORT_SYMBOL(div64_u64);
  #endif
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  #endif /* BITS_PER_LONG == 32 */
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  /*
   * Iterative div/mod for use when dividend is not expected to be much
   * bigger than divisor.
   */
  u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
  {
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  	return __iter_div_u64_rem(dividend, divisor, remainder);
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  }
  EXPORT_SYMBOL(iter_div_u64_rem);