database/sqlite
1
0
Fork 0
mirror of https://github.com/sqlite/sqlite.git synced 2025-11-11 01:42:22 +03:00
Code Activity

Faster and smaller implementation of sqlite3AtoF() based on a suggestion

Browse Source 
from Cezary H. Noweta.

FossilOrigin-Name: fd2e0e7a770c2ce9355068aad1024c3d2861c104fd3be304a91c55ca742155fa
This commit is contained in:
drh
2017-12-26 14:46:20 +00:00
parent c8f44d245c
commit 02a43f6def
3 changed files with 28 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
src/util.c
View File

@@ -320,6 +320,24 @@ int sqlite3_strnicmp(const char *zLeft, const char *zRight, int N){
return N<0 ? 0 : UpperToLower[*a] - UpperToLower[*b];
}
/*
** Compute 10 to the E-th power. Examples: E==1 results in 10.
** E==2 results in 100. E==50 results in 1.0e50.
**
** This routine only works for values of E between 1 and 341.
*/
static LONGDOUBLE_TYPE sqlite3Pow10(int E){
LONGDOUBLE_TYPE x = 10.0;
LONGDOUBLE_TYPE r = 1.0;
while(1){
if( E & 1 ) r *= x;
E >>= 1;
if( E==0 ) break;
x *= x;
}
return r;
}
/*
** The string z[] is an text representation of a real number.
** Convert this string to a double and write it into *pResult.
@@ -475,11 +493,10 @@ do_atof_calc:
if( e==0 ){ /*OPTIMIZATION-IF-TRUE*/
result = (double)s;
}else{
LONGDOUBLE_TYPE scale = 1.0;
/* attempt to handle extremely small/large numbers better */
if( e>307 ){ /*OPTIMIZATION-IF-TRUE*/
if( e<342 ){ /*OPTIMIZATION-IF-TRUE*/
while( e%308 ) { scale *= 1.0e+1; e -= 1; }
LONGDOUBLE_TYPE scale = sqlite3Pow10(e-308);
if( esign<0 ){
result = s / scale;
result /= 1.0e+308;
@@ -499,10 +516,7 @@ do_atof_calc:
}
}
}else{
/* 1.0e+22 is the largest power of 10 than can be
** represented exactly. */
while( e%22 ) { scale *= 1.0e+1; e -= 1; }
while( e>0 ) { scale *= 1.0e+22; e -= 22; }
LONGDOUBLE_TYPE scale = sqlite3Pow10(e);
if( esign<0 ){
result = s / scale;
}else{