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Alternative decimal2double implementation using an algorithm

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more similar to my_strtod() (and maybe even a bit faster due
to less floating point divisions).

This should at least partially fix Bug #23260 for DECIMALs
with a moderate number of total digits.
This commit is contained in:
tsmith/tim@siva.hindu.god
2006-12-19 17:42:26 -07:00
parent 2bc45899c0
commit 6cbfc343a8
1 changed files with 26 additions and 8 deletions
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34
strings/decimal.c
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@ -138,6 +138,12 @@ static const dec1 frac_max[DIG_PER_DEC1-1]={
900000000, 990000000, 999000000, 900000000, 990000000, 999000000,
999900000, 999990000, 999999000, 999900000, 999990000, 999999000,
999999900, 999999990 }; 999999900, 999999990 };
static double scaler10[]= {
1.0, 1e10, 1e20, 1e30, 1e40, 1e50, 1e60, 1e70, 1e80, 1e90
};
static double scaler1[]= {
1.0, 10.0, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9
};
#ifdef HAVE_purify #ifdef HAVE_purify
#define sanity(d) DBUG_ASSERT((d)->len > 0) #define sanity(d) DBUG_ASSERT((d)->len > 0)
@ -946,15 +952,27 @@ fatal_error:
int decimal2double(decimal_t *from, double *to) int decimal2double(decimal_t *from, double *to)
{ {
double x=0, t=DIG_BASE; double result= 0.0;
int intg, frac; int i, exp= 0;
dec1 *buf=from->buf; dec1 *buf= from->buf;
for (i= from->intg; i > 0; i-= DIG_PER_DEC1)
result= result * DIG_BASE + *buf++;
for (i= from->frac; i > 0; i-= DIG_PER_DEC1) {
result= result * DIG_BASE + *buf++;
exp+= DIG_PER_DEC1;
}
DBUG_PRINT("info", ("interm.: %f %d %f", result, exp,
scaler10[exp / 10] * scaler1[exp % 10]));
result/= scaler10[exp / 10] * scaler1[exp % 10];
*to= from->sign ? -result : result;
DBUG_PRINT("info", ("result: %f (%lx)", *to, *to));
for (intg=from->intg; intg > 0; intg-=DIG_PER_DEC1)
x=x*DIG_BASE + *buf++;
for (frac=from->frac; frac > 0; frac-=DIG_PER_DEC1, t*=DIG_BASE)
x+=*buf++/t;
*to=from->sign ? -x : x;
return E_DEC_OK; return E_DEC_OK;
} }