1 /* 2 ** 2013-04-17 3 ** 4 ** The author disclaims copyright to this source code. In place of 5 ** a legal notice, here is a blessing: 6 ** 7 ** May you do good and not evil. 8 ** May you find forgiveness for yourself and forgive others. 9 ** May you share freely, never taking more than you give. 10 ** 11 ****************************************************************************** 12 ** 13 ** This SQLite extension implements functions for the exact display 14 ** and input of IEEE754 Binary64 floating-point numbers. 15 ** 16 ** ieee754(X) 17 ** ieee754(Y,Z) 18 ** 19 ** In the first form, the value X should be a floating-point number. 20 ** The function will return a string of the form 'ieee754(Y,Z)' where 21 ** Y and Z are integers such that X==Y*pow(2,Z). 22 ** 23 ** In the second form, Y and Z are integers which are the mantissa and 24 ** base-2 exponent of a new floating point number. The function returns 25 ** a floating-point value equal to Y*pow(2,Z). 26 ** 27 ** Examples: 28 ** 29 ** ieee754(2.0) -> 'ieee754(2,0)' 30 ** ieee754(45.25) -> 'ieee754(181,-2)' 31 ** ieee754(2, 0) -> 2.0 32 ** ieee754(181, -2) -> 45.25 33 */ 34 #include "sqlite3ext.h" 35 SQLITE_EXTENSION_INIT1 36 #include <assert.h> 37 #include <string.h> 38 39 /* 40 ** Implementation of the ieee754() function 41 */ 42 static void ieee754func( 43 sqlite3_context *context, 44 int argc, 45 sqlite3_value **argv 46 ){ 47 if( argc==1 ){ 48 sqlite3_int64 m, a; 49 double r; 50 int e; 51 int isNeg; 52 char zResult[100]; 53 assert( sizeof(m)==sizeof(r) ); 54 if( sqlite3_value_type(argv[0])!=SQLITE_FLOAT ) return; 55 r = sqlite3_value_double(argv[0]); 56 if( r<0.0 ){ 57 isNeg = 1; 58 r = -r; 59 }else{ 60 isNeg = 0; 61 } 62 memcpy(&a,&r,sizeof(a)); 63 if( a==0 ){ 64 e = 0; 65 m = 0; 66 }else{ 67 e = a>>52; 68 m = a & ((((sqlite3_int64)1)<<52)-1); 69 m |= ((sqlite3_int64)1)<<52; 70 while( e<1075 && m>0 && (m&1)==0 ){ 71 m >>= 1; 72 e++; 73 } 74 if( isNeg ) m = -m; 75 } 76 sqlite3_snprintf(sizeof(zResult), zResult, "ieee754(%lld,%d)", 77 m, e-1075); 78 sqlite3_result_text(context, zResult, -1, SQLITE_TRANSIENT); 79 }else if( argc==2 ){ 80 sqlite3_int64 m, e, a; 81 double r; 82 int isNeg = 0; 83 m = sqlite3_value_int64(argv[0]); 84 e = sqlite3_value_int64(argv[1]); 85 if( m<0 ){ 86 isNeg = 1; 87 m = -m; 88 if( m<0 ) return; 89 }else if( m==0 && e>1000 && e<1000 ){ 90 sqlite3_result_double(context, 0.0); 91 return; 92 } 93 while( (m>>32)&0xffe00000 ){ 94 m >>= 1; 95 e++; 96 } 97 while( m!=0 && ((m>>32)&0xfff00000)==0 ){ 98 m <<= 1; 99 e--; 100 } 101 e += 1075; 102 if( e<0 ) e = m = 0; 103 if( e>0x7ff ) e = 0x7ff; 104 a = m & ((((sqlite3_int64)1)<<52)-1); 105 a |= e<<52; 106 if( isNeg ) a |= ((sqlite3_uint64)1)<<63; 107 memcpy(&r, &a, sizeof(r)); 108 sqlite3_result_double(context, r); 109 } 110 } 111 112 113 #ifdef _WIN32 114 __declspec(dllexport) 115 #endif 116 int sqlite3_ieee_init( 117 sqlite3 *db, 118 char **pzErrMsg, 119 const sqlite3_api_routines *pApi 120 ){ 121 int rc = SQLITE_OK; 122 SQLITE_EXTENSION_INIT2(pApi); 123 (void)pzErrMsg; /* Unused parameter */ 124 rc = sqlite3_create_function(db, "ieee754", 1, SQLITE_UTF8, 0, 125 ieee754func, 0, 0); 126 if( rc==SQLITE_OK ){ 127 rc = sqlite3_create_function(db, "ieee754", 2, SQLITE_UTF8, 0, 128 ieee754func, 0, 0); 129 } 130 return rc; 131 } 132