executor/src/parsenum.c

/* Copyright 1995 by Abacus Research and
 * Development, Inc.  All rights reserved.
 */

#if !defined (OMIT_RCSID_STRINGS)
char ROMlib_rcsid_parsenum[] =
	    "$Id: parsenum.c 63 2004-12-24 18:19:43Z ctm $";
#endif

#include "rsys/common.h"
#include "rsys/parsenum.h"
#include <ctype.h>


/* If the given string has a 'k', 'K', 'm', or 'M' suffix, returns the
 * log base 2 corresponding to that size (either 10 or 20) and removes
 * the suffix from the string.  If no suffix is found, returns 0.
 */
static int
fetch_and_remove_shift_suffix (char *num)
{
  char *end;
  int shift, last;

  end = &num[strlen (num) - 1];
  last = *end;
  if (islower (last))	/* Check not actually needed under ANSI C. */
    last = toupper (last);

  if (last == 'K')
    shift = 10;  /* 1K == 1 << 10 */
  else if (last == 'M')
    shift = 20;  /* 1M == 1 << 20 */
  else
    shift = 0;

  if (shift)
    *end = '\0';

  return shift;
}


/* Parses the given input string as a number of base strlen(digits)
 * with the specified digits.  Returns by reference the parsed value
 * as (*vp / *divisorp), which may be fractional.  All letters in the
 * digits string must be uppercase.  All input characters are
 * converted to upper case.
 */
static boolean_t
parse_base_number (const char *s, const char *digits, long long *vp,
		   long long *divisorp)
{
  long long v, divisor;
  boolean_t found_dot_p;
  int radix;

  /* Make sure there's at least one digit. */  
  if (s[0] == '\0')
    return FALSE;

  radix = strlen (digits);

  for (v = 0, divisor = 1, found_dot_p = FALSE; *s; s++)
    {
      const char *p;
      int n;

      n = toupper (*s);
      if (n == '.')
	{
	  if (found_dot_p)  /* Only one decimal point allowed. */
	    return FALSE;
	  found_dot_p = TRUE;
	}
      else
	{
	  p = strchr (digits, n);
	  if (p == NULL)
	    return FALSE;
	  if (v > 0x7FFFFFFFFFFFFFFFLL / radix    /* Check overflow. */
	      || divisor > 0x7FFFFFFFFFFFFFFFLL / radix)
	    return FALSE;
	  v = (v * radix) + (p - digits);
	  if (found_dot_p)
	    divisor *= radix;
	}	  
    }

  *vp = v;
  *divisorp = divisor;
  return TRUE;
}


/* Parse a number specified in a flexible format.  Returns TRUE iff
 * the parse was successful and the result didn't exceed 32 bits,
 * else FALSE.  Returns by reference the parsed value in *val.
 *
 * Each number may have an optional preceding "+" or "-" sign, which
 * do the obvious thing.
 * 
 * Base numbers may be specified in several ways:
 *
 * "123"	; decimal number
 * "146.5"	; floating point value
 * "0x12AC"	; hexadecimal number
 * "0x12AC.12A"	; hexadecimal floating point
 * "0b010010"	; binary number
 * "0b010.10"	; binary floating point
 *
 * I decided not to allow octal because that might confuse
 * unsophisticated users who accidentally precede a number with a
 * leading zero.
 *
 * The number may be followed by an optional case-insensitive suffix:
 *
 * "K" or "k"	; multiply the value by 1024 (1K)
 * "M" or "m"	; multiply the value by 1024*1024 (1M)
 *
 * Floating point results will be rounded toward zero before they are
 * returned.  The rounding happens *after* any multiplication suffix
 * is applied, so "1.5K" is exactly equivalent to "1536".
 *
 * The truncated result can then be rounded up to the next highest
 * (farther from zero) multiple of a specified number.  If you don't
 * want rounding, just pass "1" for round_up_to_multiple_of.
 */
boolean_t
parse_number (const char *orig_num, int32 *val,
	      unsigned round_up_to_multiple_of)
{
  long long orig_raw_val, raw_val, div;
  int shift_factor;
  boolean_t negate_p, parsed_p;
  int32 v;
  char *num;

  /* Default value to be safe. */
  *val = 0;

  /* Empty string is an error.  We check this here to simplify checks later. */
  if (orig_num == NULL || orig_num[0] == '\0')
    return FALSE;

  num = (char *) alloca (strlen (orig_num) + 1);
  strcpy (num, orig_num);

  /* Check for leading + or -, and advance past it. */
  negate_p = (num[0] == '-');
  num += (num[0] == '-' || num[0] == '+');

  /* Look for a trailing suffix. */
  shift_factor = fetch_and_remove_shift_suffix (num);

  /* Figure out which parsing function to use. */
  if (num[0] == '0' && num[1] == 'x')
    parsed_p = parse_base_number (num + 2, "0123456789ABCDEF", &raw_val, &div);
  else if (num[0] == '0' && num[1] == 'b')
    parsed_p = parse_base_number (num + 2, "01", &raw_val, &div);
  else
    parsed_p = parse_base_number (num, "0123456789", &raw_val, &div);

  /* Make sure we parsed successfully. */
  if (!parsed_p)
    return FALSE;

  /* Compute the resulting number by applying the scaling factors. */
  orig_raw_val = raw_val;
  raw_val <<= shift_factor;
  if (raw_val >> shift_factor != orig_raw_val)  /* exceeded precision? */
    return FALSE;
  raw_val /= div;

  /* Make sure we didn't exceed the precision of the result. */
  v = raw_val;
  if (v != raw_val)
    return FALSE;

  /* Round up if so specified. */
  if (round_up_to_multiple_of > 1)
    {
      v += round_up_to_multiple_of - 1;
      v -= v % round_up_to_multiple_of;
    }

  *val = negate_p ? -v : v;

  return TRUE;
}