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/*
** 2013-04-17
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** This SQLite extension implements functions for the exact display
** and input of IEEE754 Binary64 floating-point numbers.
**
** ieee754(X)
** ieee754(Y,Z)
**
** In the first form, the value X should be a floating-point number.
** The function will return a string of the form 'ieee754(Y,Z)' where
** Y and Z are integers such that X==Y*pow(2,Z).
**
** In the second form, Y and Z are integers which are the mantissa and
** base-2 exponent of a new floating point number. The function returns
** a floating-point value equal to Y*pow(2,Z).
**
** Examples:
**
** ieee754(2.0) -> 'ieee754(2,0)'
** ieee754(45.25) -> 'ieee754(181,-2)'
** ieee754(2, 0) -> 2.0
** ieee754(181, -2) -> 45.25
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
/*
** Implementation of the ieee754() function
*/
static void ieee754func(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
if( argc==1 ){
sqlite3_int64 m, a;
double r;
int e;
int isNeg;
char zResult[100];
assert( sizeof(m)==sizeof(r) );
if( sqlite3_value_type(argv[0])!=SQLITE_FLOAT ) return;
r = sqlite3_value_double(argv[0]);
if( r<0.0 ){
isNeg = 1;
r = -r;
}else{
isNeg = 0;
}
memcpy(&a,&r,sizeof(a));
if( a==0 ){
e = 0;
m = 0;
}else{
e = a>>52;
m = a & ((((sqlite3_int64)1)<<52)-1);
m |= ((sqlite3_int64)1)<<52;
while( e<1075 && m>0 && (m&1)==0 ){
m >>= 1;
e++;
}
if( isNeg ) m = -m;
}
sqlite3_snprintf(sizeof(zResult), zResult, "ieee754(%lld,%d)",
m, e-1075);
sqlite3_result_text(context, zResult, -1, SQLITE_TRANSIENT);
}else if( argc==2 ){
sqlite3_int64 m, e, a;
double r;
int isNeg = 0;
m = sqlite3_value_int64(argv[0]);
e = sqlite3_value_int64(argv[1]);
if( m<0 ){
isNeg = 1;
m = -m;
if( m<0 ) return;
}else if( m==0 && e>1000 && e<1000 ){
sqlite3_result_double(context, 0.0);
return;
}
while( (m>>32)&0xffe00000 ){
m >>= 1;
e++;
}
while( m!=0 && ((m>>32)&0xfff00000)==0 ){
m <<= 1;
e--;
}
e += 1075;
if( e<0 ) e = m = 0;
if( e>0x7ff ) e = 0x7ff;
a = m & ((((sqlite3_int64)1)<<52)-1);
a |= e<<52;
if( isNeg ) a |= ((sqlite3_uint64)1)<<63;
memcpy(&r, &a, sizeof(r));
sqlite3_result_double(context, r);
}
}
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_ieee_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
(void)pzErrMsg; /* Unused parameter */
rc = sqlite3_create_function(db, "ieee754", 1, SQLITE_UTF8, 0,
ieee754func, 0, 0);
if( rc==SQLITE_OK ){
rc = sqlite3_create_function(db, "ieee754", 2, SQLITE_UTF8, 0,
ieee754func, 0, 0);
}
return rc;
}
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