| /* |
| ** 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; |
| } |