Backport my_strntod() from 5.0

Change string->float conversion to delay division as long as possible.
This gives us more exact integer->float conversion for numbers of type '123.45E+02' (Bug #7740)




client/mysql.cc:
  Fix wront usage of charset (found during review of pushed code)
include/m_string.h:
  Backported my_strtod() from 5.0
mysql-test/mysql-test-run.sh:
  Run also mysql_client_test with --debug
mysql-test/r/ps_1general.result:
  Safety fix (if mysql_client_test.test fails)
mysql-test/r/type_float.result:
  More test
mysql-test/t/mysql_client_test.test:
  Comments for what to do if this test fails
mysql-test/t/ps_1general.test:
  Safety fix (if mysql_client_test.test fails)
mysql-test/t/type_float.test:
  More test to better test new strtod() function
  Test also bug #7740 (wrong comparsion between integer and float-in-integer-range)
sql/field.cc:
  Backport my_strntod() from 5.0
sql/item.cc:
  Backport my_strntod() from 5.0
sql/item.h:
  Backport my_strntod() from 5.0
sql/item_func.h:
  Backport my_strntod() from 5.0
sql/item_strfunc.cc:
  Backport my_strntod() from 5.0
sql/item_sum.cc:
  Backport my_strntod() from 5.0
sql/item_sum.h:
  Backport my_strntod() from 5.0
sql/procedure.h:
  Backport my_strntod() from 5.0
strings/ctype-simple.c:
  Backport my_strntod() from 5.0
strings/ctype-ucs2.c:
  Backport my_strntod() from 5.0
strings/strtod.c:
  Backport my_strntod() from 5.0
  Change conversion to delay division as long as possible.
  This gives us more exact integer-> float conversion for numbers of type '123.45E+02'

1 files changed, 119 insertions, 48 deletions

diff --git a/strings/strtod.c b/strings/strtod.c
index bc8105b8040..61f2c107abe 100644
--- a/strings/strtod.c
+++ b/strings/strtod.c
@@ -2,7 +2,7 @@
   An alternative implementation of "strtod()" that is both
   simplier, and thread-safe.
 
-  From mit-threads as bundled with MySQL 3.23
+  Original code from mit-threads as bundled with MySQL 3.23
 
   SQL:2003 specifies a number as
 
@@ -29,6 +29,8 @@
 #include "my_base.h"				/* Includes errno.h */
 #include "m_ctype.h"
 
+#define MAX_DBL_EXP	308
+#define MAX_RESULT_FOR_MAX_EXP 1.79769313486232
 static double scaler10[] = {
   1.0, 1e10, 1e20, 1e30, 1e40, 1e50, 1e60, 1e70, 1e80, 1e90
 };
@@ -37,89 +39,157 @@ static double scaler1[] = {
 };
 
 
-double my_strtod(const char *str, char **end)
+/*
+  Convert string to double (string doesn't have to be null terminated)
+
+  SYNOPSIS
+    my_strtod()
+    str		String to convert
+    end_ptr	Pointer to pointer that points to end of string
+		Will be updated to point to end of double.
+    error	Will contain error number in case of error (else 0)
+
+  RETURN
+    value of str as double
+*/
+
+double my_strtod(const char *str, char **end_ptr, int *error)
 {
   double result= 0.0;
-  int negative, ndigits;
-  const char *old_str;
+  uint negative= 0, ndigits, dec_digits= 0, neg_exp= 0;
+  int exp= 0, digits_after_dec_point= 0;
+  const char *old_str, *end= *end_ptr, *start_of_number;
+  char next_char;
   my_bool overflow=0;
 
+  *error= 0;
+  if (str >= end)
+    goto done;
+
   while (my_isspace(&my_charset_latin1, *str))
-    str++;
+  {
+    if (++str == end)
+      goto done;
+  }
 
+  start_of_number= str;
   if ((negative= (*str == '-')) || *str=='+')
-    str++;
+  {
+    if (++str == end)
+      goto done;                                /* Could be changed to error */
+  }
+
+  /* Skip pre-zero for easier calculation of overflows */
+  while (*str == '0')
+  {
+    if (++str == end)
+      goto done;
+    start_of_number= 0;                         /* Found digit */
+  }
 
   old_str= str;
-  while (my_isdigit (&my_charset_latin1, *str))
+  while ((next_char= *str) >= '0' && next_char <= '9')
   {
-    result= result*10.0 + (*str - '0');
-    str++;
+    result= result*10.0 + (next_char - '0');
+    if (++str == end)
+    {
+      next_char= 0;                             /* Found end of string */
+      break;
+    }
+    start_of_number= 0;                         /* Found digit */
   }
-  ndigits= str-old_str;
+  ndigits= (uint) (str-old_str);
 
-  if (*str == '.')
+  if (next_char == '.' && str < end-1)
   {
-    double p10=10;
-    str++;
-    old_str= str;
-    while (my_isdigit (&my_charset_latin1, *str))
+    /*
+      Continue to add numbers after decimal point to the result, as if there
+      was no decimal point. We will later (in the exponent handling) shift
+      the number down with the required number of fractions.  We do it this
+      way to be able to get maximum precision for numbers like 123.45E+02,
+      which are normal for some ODBC applications.
+    */
+    old_str= ++str;
+    while (my_isdigit(&my_charset_latin1, (next_char= *str)))
     {
-      result+= (*str++ - '0')/p10;
-      p10*=10;
+      result= result*10.0 + (next_char - '0');
+      digits_after_dec_point++;
+      if (++str == end)
+      {
+        next_char= 0;
+        break;
+      }
     }
-    ndigits+= str-old_str;
-    if (!ndigits) str--;
+    /* If we found just '+.' or '.' then point at first character */
+    if (!(dec_digits= (uint) (str-old_str)) && start_of_number)
+      str= start_of_number;                     /* Point at '+' or '.' */
   }
-  if (ndigits && (*str=='e' || *str=='E'))
+  if ((next_char == 'e' || next_char == 'E') &&
+      dec_digits + ndigits != 0 && str < end-1)
   {
-    int exp= 0;
-    int neg= 0;
     const char *old_str= str++;
 
-    if ((neg= (*str == '-')) || *str == '+')
+    if ((neg_exp= (*str == '-')) || *str == '+')
       str++;
 
-    if (!my_isdigit (&my_charset_latin1, *str))
+    if (str == end || !my_isdigit(&my_charset_latin1, *str))
       str= old_str;
     else
     {
-      double scaler= 1.0;
-      while (my_isdigit (&my_charset_latin1, *str))
+      do
       {
-        if (exp < 9999) /* protection against exp overflow */
-          exp= exp*10 + *str - '0';
+        if (exp < 9999)                         /* prot. against exp overfl. */
+          exp= exp*10 + (*str - '0');
         str++;
-      }
-      if (exp >= 1000)
+      } while (str < end && my_isdigit(&my_charset_latin1, *str));
+    }
+  }
+  if ((exp= (neg_exp ? exp + digits_after_dec_point :
+             exp - digits_after_dec_point)))
+  {
+    double scaler;
+    if (exp < 0)
+    {
+      exp= -exp;
+      neg_exp= 1;                               /* neg_exp was 0 before */
+    }
+    if (exp + ndigits >= MAX_DBL_EXP + 1 && result)
+    {
+      /*
+        This is not 100 % as we actually will give an owerflow for
+        17E307 but not for 1.7E308 but lets cut some corners to make life
+        simpler
+      */
+      if (exp + ndigits > MAX_DBL_EXP + 1 ||
+          result >= MAX_RESULT_FOR_MAX_EXP)
       {
-	if (neg)
-	  result= 0.0;
-	else
+        if (neg_exp)
+          result= 0.0;
+        else
           overflow= 1;
         goto done;
       }
-      while (exp >= 100)
-      {
-        scaler*= 1.0e100;
-        exp-= 100;
-      }
-      scaler*= scaler10[exp/10]*scaler1[exp%10];
-      if (neg)
-        result/= scaler;
-      else
-        result*= scaler;
     }
+    scaler= 1.0;
+    while (exp >= 100)
+    {
+      scaler*= 1.0e100;
+      exp-= 100;
+    }
+    scaler*= scaler10[exp/10]*scaler1[exp%10];
+    if (neg_exp)
+      result/= scaler;
+    else
+      result*= scaler;
   }
 
 done:
-  if (end)
-    *end = (char *)str;
+  *end_ptr= (char*) str;                        /* end of number */
 
   if (overflow || isinf(result))
   {
     result= DBL_MAX;
-    errno= EOVERFLOW;
+    *error= EOVERFLOW;
   }
 
   return negative ? -result : result;
@@ -127,6 +197,7 @@ done:
 
 double my_atof(const char *nptr)
 {
-  return (my_strtod(nptr, 0));
+  int error;
+  const char *end= nptr+65535;                  /* Should be enough */
+  return (my_strtod(nptr, (char**) &end, &error));
 }
-