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Micro-optimize char_decimal_value.

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* libguile/numbers.c (char_decimal_value): A wee micro-optimization.
This commit is contained in:
Andy Wingo 2013-08-31 11:15:01 +02:00
parent 25752c4d1c
commit 6871327742
1 changed files with 17 additions and 12 deletions
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29
libguile/numbers.c
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@ -5798,20 +5798,25 @@ enum t_exactness {NO_EXACTNESS, INEXACT, EXACT};
static unsigned int
char_decimal_value (scm_t_uint32 c)
{
/* uc_decimal_value returns -1 on error. When cast to an unsigned int,
that's certainly above any valid decimal, so we take advantage of
that to elide some tests. */
unsigned int d = (unsigned int) uc_decimal_value (c);
/* If that failed, try extended hexadecimals, then. Only accept ascii
hexadecimals. */
if (d >= 10U)
if (c >= (scm_t_uint32) '0' && c <= (scm_t_uint32) '9')
return c - (scm_t_uint32) '0';
else
{
c = uc_tolower (c);
if (c >= (scm_t_uint32) 'a')
d = c - (scm_t_uint32)'a' + 10U;
/* uc_decimal_value returns -1 on error. When cast to an unsigned int,
that's certainly above any valid decimal, so we take advantage of
that to elide some tests. */
unsigned int d = (unsigned int) uc_decimal_value (c);
/* If that failed, try extended hexadecimals, then. Only accept ascii
hexadecimals. */
if (d >= 10U)
{
c = uc_tolower (c);
if (c >= (scm_t_uint32) 'a')
d = c - (scm_t_uint32)'a' + 10U;
}
return d;
}
return d;
}
/* Parse the substring of MEM starting at *P_IDX for an unsigned integer