1 files changed, 131 insertions, 0 deletions
diff --git a/ext/misc/ieee754.c b/ext/misc/ieee754.c
new file mode 100644
index 0000000..436b11e
--- /dev/null
+++ b/ext/misc/ieee754.c
@@ -0,0 +1,131 @@
+/*
+** 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(w.0,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(2.0,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>>32)&0xfff00000)==0 ){
+      m <<= 1;
+      e--;
+    }
+    e += 1075;
+    if( e<0 ) e = m = 0;
+    if( e>0x7ff ) m = 0;
+    a = m & ((((sqlite3_int64)1)<<52)-1);
+    a |= e<<52;
+    if( isNeg ) a |= ((sqlite3_int64)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;
+}