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