Backport of WL #2934: Make/find library for doing float/double

                      to string conversions and vice versa" 
Initial import of the dtoa.c code and custom wrappers around it 
to allow its usage from the server code. 
 
Conversion of FLOAT/DOUBLE values to DECIMAL ones or strings 
and vice versa has been significantly reworked. As the new 
algoritms are more precise than the older ones, results of such 
conversions may not always match those obtained from older 
server versions. This in turn may break compatibility for some 
applications. 
 
This patch also fixes the following bugs: 
- bug #12860 "Difference in zero padding of exponent between 
Unix and Windows" 
- bug #21497 "DOUBLE truncated to unusable value" 
- bug #26788 "mysqld (debug) aborts when inserting specific 
numbers into char fields" 
- bug #24541 "Data truncated..." on decimal type columns 
without any good reason" 

1 files changed, 30 insertions, 213 deletions

diff --git a/sql/field.cc b/sql/field.cc
index 0934bb04ccd..56da32959f9 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -31,9 +31,6 @@
 #include "slave.h"                              // Pull in rpl_master_has_bug()
 #include <m_ctype.h>
 #include <errno.h>
-#ifdef HAVE_FCONVERT
-#include <floatingpoint.h>
-#endif
 
 // Maximum allowed exponent value for converting string to decimal
 #define MAX_EXPONENT 1024
@@ -50,7 +47,7 @@ template class List_iterator<Create_field>;
 uchar Field_null::null[1]={1};
 const char field_separator=',';
 
-#define DOUBLE_TO_STRING_CONVERSION_BUFFER_SIZE 320
+#define DOUBLE_TO_STRING_CONVERSION_BUFFER_SIZE FLOATING_POINT_BUFFER
 #define LONGLONG_TO_STRING_CONVERSION_BUFFER_SIZE 128
 #define DECIMAL_TO_STRING_CONVERSION_BUFFER_SIZE 128
 #define BLOB_PACK_LENGTH_TO_MAX_LENGH(arg) \
@@ -2304,13 +2301,7 @@ int Field_decimal::store(double nr)
   char buff[DOUBLE_TO_STRING_CONVERSION_BUFFER_SIZE];
 
   fyllchar = zerofill ? (char) '0' : (char) ' ';
-#ifdef HAVE_SNPRINTF
-  buff[sizeof(buff)-1]=0;			// Safety
-  snprintf(buff,sizeof(buff)-1, "%.*f",(int) dec,nr);
-  length= strlen(buff);
-#else
-  length= my_sprintf(buff,(buff,"%.*f",dec,nr));
-#endif
+  length= my_fcvt(nr, dec, buff, NULL);
 
   if (length > field_length)
   {
@@ -2723,17 +2714,6 @@ int Field_new_decimal::store(double nr)
 
   err= double2my_decimal(E_DEC_FATAL_ERROR & ~E_DEC_OVERFLOW, nr,
                          &decimal_value);
-  /*
-    TODO: fix following when double2my_decimal when double2decimal
-    will return E_DEC_TRUNCATED always correctly
-  */
-  if (!err)
-  {
-    double nr2;
-    my_decimal2double(E_DEC_FATAL_ERROR, &decimal_value, &nr2);
-    if (nr2 != nr)
-      err= E_DEC_TRUNCATED;
-  }
   if (err)
   {
     if (check_overflow(err))
@@ -4231,67 +4211,20 @@ String *Field_float::val_str(String *val_buffer,
   uint to_length=max(field_length,70);
   val_buffer->alloc(to_length);
   char *to=(char*) val_buffer->ptr();
+  size_t len;
 
   if (dec >= NOT_FIXED_DEC)
-  {
-    sprintf(to,"%-*.*g",(int) field_length,FLT_DIG,nr);
-    to=strcend(to,' ');
-    *to=0;
-  }
+    len= my_gcvt(nr, MY_GCVT_ARG_FLOAT, to_length - 1, to, NULL);
   else
   {
-#ifdef HAVE_FCONVERT
-    char buff[70],*pos=buff;
-    int decpt,sign,tmp_dec=dec;
-
-    (void) sfconvert(&nr,tmp_dec,&decpt,&sign,buff);
-    if (sign)
-    {
-      *to++='-';
-    }
-    if (decpt < 0)
-    {					/* val_buffer is < 0 */
-      *to++='0';
-      if (!tmp_dec)
-	goto end;
-      *to++='.';
-      if (-decpt > tmp_dec)
-	decpt= - (int) tmp_dec;
-      tmp_dec=(uint) ((int) tmp_dec+decpt);
-      while (decpt++ < 0)
-	*to++='0';
-    }
-    else if (decpt == 0)
-    {
-      *to++= '0';
-      if (!tmp_dec)
-	goto end;
-      *to++='.';
-    }
-    else
-    {
-      while (decpt-- > 0)
-	*to++= *pos++;
-      if (!tmp_dec)
-	goto end;
-      *to++='.';
-    }
-    while (tmp_dec--)
-      *to++= *pos++;
-#else
-#ifdef HAVE_SNPRINTF
-    to[to_length-1]=0;			// Safety
-    snprintf(to,to_length-1,"%.*f",dec,nr);
-    to=strend(to);
-#else
-    to+= my_sprintf(to,(to,"%.*f",dec,nr));
-#endif
-#endif
+    /*
+      We are safe here because the buffer length is >= 70, and
+      fabs(float) < 10^39, dec < NOT_FIXED_DEC. So the resulting string
+      will be not longer than 69 chars + terminating '\0'.
+    */
+    len= my_fcvt(nr, dec, to, NULL);
   }
-#ifdef HAVE_FCONVERT
- end:
-#endif
-  val_buffer->length((uint) (to-val_buffer->ptr()));
+  val_buffer->length((uint) len);
   if (zerofill)
     prepend_zeros(val_buffer);
   return val_buffer;
@@ -4479,8 +4412,12 @@ int Field_real::truncate(double *nr, double max_value)
     max_value*= log_10[order];
     max_value-= 1.0 / log_10[dec];
 
-    double tmp= rint((res - floor(res)) * log_10[dec]) / log_10[dec];
-    res= floor(res) + tmp;
+    /* Check for infinity so we don't get NaN in calculations */
+    if (!my_isinf(res))
+    {
+      double tmp= rint((res - floor(res)) * log_10[dec]) / log_10[dec];
+      res= floor(res) + tmp;
+    }
   }
   
   if (res < -max_value)
@@ -4590,68 +4527,14 @@ String *Field_double::val_str(String *val_buffer,
   uint to_length=max(field_length, DOUBLE_TO_STRING_CONVERSION_BUFFER_SIZE);
   val_buffer->alloc(to_length);
   char *to=(char*) val_buffer->ptr();
+  size_t len;
 
   if (dec >= NOT_FIXED_DEC)
-  {
-    sprintf(to,"%-*.*g",(int) field_length,DBL_DIG,nr);
-    to=strcend(to,' ');
-  }
+    len= my_gcvt(nr, MY_GCVT_ARG_DOUBLE, to_length - 1, to, NULL);
   else
-  {
-#ifdef HAVE_FCONVERT
-    char buff[DOUBLE_TO_STRING_CONVERSION_BUFFER_SIZE];
-    char *pos= buff;
-    int decpt,sign,tmp_dec=dec;
-
-    (void) fconvert(nr,tmp_dec,&decpt,&sign,buff);
-    if (sign)
-    {
-      *to++='-';
-    }
-    if (decpt < 0)
-    {					/* val_buffer is < 0 */
-      *to++='0';
-      if (!tmp_dec)
-	goto end;
-      *to++='.';
-      if (-decpt > tmp_dec)
-	decpt= - (int) tmp_dec;
-      tmp_dec=(uint) ((int) tmp_dec+decpt);
-      while (decpt++ < 0)
-	*to++='0';
-    }
-    else if (decpt == 0)
-    {
-      *to++= '0';
-      if (!tmp_dec)
-	goto end;
-      *to++='.';
-    }
-    else
-    {
-      while (decpt-- > 0)
-	*to++= *pos++;
-      if (!tmp_dec)
-	goto end;
-      *to++='.';
-    }
-    while (tmp_dec--)
-      *to++= *pos++;
-#else
-#ifdef HAVE_SNPRINTF
-    to[to_length-1]=0;			// Safety
-    snprintf(to,to_length-1,"%.*f",dec,nr);
-    to=strend(to);
-#else
-    to+= my_sprintf(to,(to,"%.*f",dec,nr));
-#endif
-#endif
-  }
-#ifdef HAVE_FCONVERT
- end:
-#endif
+    len= my_fcvt(nr, dec, to, NULL);
 
-  val_buffer->length((uint) (to-val_buffer->ptr()));
+  val_buffer->length((uint) len);
   if (zerofill)
     prepend_zeros(val_buffer);
   return val_buffer;
@@ -6448,84 +6331,18 @@ int Field_str::store(double nr)
 {
   ASSERT_COLUMN_MARKED_FOR_WRITE;
   char buff[DOUBLE_TO_STRING_CONVERSION_BUFFER_SIZE];
-  uint length;
   uint local_char_length= field_length / charset()->mbmaxlen;
-  double anr= fabs(nr);
-  bool fractional= (anr != floor(anr));
-  int neg= (nr < 0.0) ? 1 : 0;
-  uint max_length;
-  int exp;
-  uint digits;
-  uint i;
-
-  /* Calculate the exponent from the 'e'-format conversion */
-  if (anr < 1.0 && anr > 0)
-  {
-    for (exp= 0; anr < 1e-100; exp-= 100, anr*= 1e100) ;
-    for (; anr < 1e-10; exp-= 10, anr*= 1e10) ;
-    for (i= 1; anr < 1 / log_10[i]; exp--, i++) ;
-    exp--;
-  }
-  else
-  {
-    for (exp= 0; anr > 1e100; exp+= 100, anr/= 1e100) ;
-    for (; anr > 1e10; exp+= 10, anr/= 1e10) ;
-    for (i= 1; anr > log_10[i]; exp++, i++) ;
-  }
-
-  max_length= local_char_length - neg;
-
-  /*
-    Since in sprintf("%g") precision means the number of significant digits,
-    calculate the maximum number of significant digits if the 'f'-format
-    would be used (+1 for decimal point if the number has a fractional part).
-  */
-  digits= max(1, (int) max_length - fractional);
-  /*
-    If the exponent is negative, decrease digits by the number of leading zeros
-    after the decimal point that do not count as significant digits.
-  */
-  if (exp < 0)
-    digits= max(1, (int) digits + exp);
-  /*
-    'e'-format is used only if the exponent is less than -4 or greater than or
-    equal to the precision. In this case we need to adjust the number of
-    significant digits to take "e+NN" + decimal point into account (hence -5).
-    We also have to reserve one additional character if abs(exp) >= 100.
-  */
-  if (exp >= (int) digits || exp < -4)
-    digits= max(1, (int) (max_length - 5 - (exp >= 100 || exp <= -100)));
-
-  /* Limit precision to DBL_DIG to avoid garbage past significant digits */
-  set_if_smaller(digits, DBL_DIG);
-  
-  length= (uint) my_sprintf(buff, (buff, "%-.*g", digits, nr));
+  size_t length;
+  my_bool error;
 
-#ifdef __WIN__
-  /*
-    Windows always zero-pads the exponent to 3 digits, we want to remove the
-    leading 0 to match the sprintf() output on other platforms.
-  */
-  if ((exp >= (int) digits || exp < -4) && exp > -100 && exp < 100)
+  length= my_gcvt(nr, MY_GCVT_ARG_DOUBLE, local_char_length, buff, &error);
+  if (error)
   {
-    DBUG_ASSERT(length >= 6); /* 1e+NNN */
-    uint tmp= length - 3;
-    buff[tmp]= buff[tmp + 1];
-    tmp++;
-    buff[tmp]= buff[tmp + 1];
-    length--;
+    if (table->in_use->abort_on_warning)
+      set_warning(MYSQL_ERROR::WARN_LEVEL_WARN, ER_DATA_TOO_LONG, 1);
+    else
+      set_warning(MYSQL_ERROR::WARN_LEVEL_WARN, WARN_DATA_TRUNCATED, 1);
   }
-#endif
-  
-  /*
-    +1 below is because "precision" in %g above means the
-    max. number of significant digits, not the output width.
-    Thus the width can be larger than number of significant digits by 1
-    (for decimal point)
-    the test for local_char_length < 5 is for extreme cases,
-    like inserting 500.0 in char(1)
-  */
-  DBUG_ASSERT(local_char_length < 5 || length <= local_char_length+1);
   return store(buff, length, charset());
 }
 
@@ -7601,7 +7418,7 @@ oom_error:
 int Field_blob::store(double nr)
 {
   CHARSET_INFO *cs=charset();
-  value.set_real(nr, 2, cs);
+  value.set_real(nr, NOT_FIXED_DEC, cs);
   return Field_blob::store(value.ptr(),(uint) value.length(), cs);
 }