Re: [ID 20010529.006] String plus zero inconsistent across platforms

Message-Id: <200106031356.OAA12517@crypt.compulink.co.uk>

p4raw-id: //depot/perl@10396

diff --git a/util.c b/util.c
index 9786081..8d51730 100644 (file)
--- a/util.c
+++ b/util.c
@@ -4033,6 +4033,35 @@ Perl_my_atof(pTHX_ const char* s)
     return x;
 }
 
+NV
+S_mulexp10(NV value, I32 exponent)
+{
+    NV result = value;
+    NV power = 10.0;
+    I32 bit;
+
+    if (exponent > 0) {
+       for (bit = 1; exponent; bit <<= 1) {
+           if (exponent & bit) {
+               exponent ^= bit;
+               result *= power;
+           }
+           power *= power;
+       }
+    }
+    else if (exponent < 0) {
+       exponent = -exponent;
+       for (bit = 1; exponent; bit <<= 1) {
+           if (exponent & bit) {
+               exponent ^= bit;
+               result /= power;
+           }
+           power *= power;
+       }
+    }
+    return result;
+}
+
 char*
 Perl_my_atof2(pTHX_ const char* orig, NV* value)
 {
@@ -4042,10 +4071,26 @@ Perl_my_atof2(pTHX_ const char* orig, NV* value)
     char* point = "."; /* locale-dependent decimal point equivalent */
     STRLEN pointlen = 1;
     bool seendigit = 0;
+    I32 expextra = 0;
+    I32 exponent = 0;
+    I32 i;
+/* this is arbitrary */
+#define PARTLIM 6
+/* we want the largest integers we can usefully use */
+#if defined(HAS_QUAD) && defined(USE_64_BIT_INT)
+#   define PARTSIZE ((int)TYPE_DIGITS(U64)-1)
+    U64 part[PARTLIM];
+#else
+#   define PARTSIZE ((int)TYPE_DIGITS(U32)-1)
+    U32 part[PARTLIM];
+#endif
+    I32 ipart = 0;     /* index into part[] */
+    I32 offcount;      /* number of digits in least significant part */
 
     if (PL_numeric_radix_sv)
        point = SvPV(PL_numeric_radix_sv, pointlen);
 
+    /* sign */
     switch (*s) {
        case '-':
            negative = 1;
@@ -4053,23 +4098,77 @@ Perl_my_atof2(pTHX_ const char* orig, NV* value)
        case '+':
            ++s;
     }
+
+    part[0] = offcount = 0;
+    if (isDIGIT(*s)) {
+       seendigit = 1;  /* get this over with */
+
+       /* skip leading zeros */
+       while (*s == '0')
+           ++s;
+    }
+
+    /* integer digits */
     while (isDIGIT(*s)) {
-       result = result * 10 + (*s++ - '0');
-       seendigit = 1;
+       if (++offcount > PARTSIZE) {
+           if (++ipart < PARTLIM) {
+               part[ipart] = 0;
+               offcount = 1;   /* ++0 */
+           }
+           else {
+               /* limits of precision reached */
+               --ipart;
+               --offcount;
+               if (*s >= '5')
+                   ++part[ipart];
+               while (isDIGIT(*s)) {
+                   ++expextra;
+                   ++s;
+               }
+               /* warn of loss of precision? */
+               break;
+           }
+       }
+       part[ipart] = part[ipart] * 10 + (*s++ - '0');
     }
-    if (memEQ(s, point, pointlen)) {
-       NV decimal = 0.1;
 
+    /* decimal point */
+    if (memEQ(s, point, pointlen)) {
        s += pointlen;
+       if (isDIGIT(*s))
+           seendigit = 1;      /* get this over with */
+
+       /* decimal digits */
        while (isDIGIT(*s)) {
-           result += (*s++ - '0') * decimal;
-           decimal *= 0.1;
-           seendigit = 1;
+           if (++offcount > PARTSIZE) {
+               if (++ipart < PARTLIM) {
+                   part[ipart] = 0;
+                   offcount = 1;       /* ++0 */
+               }
+               else {
+                   /* limits of precision reached */
+                   --ipart;
+                   --offcount;
+                   if (*s >= '5')
+                       ++part[ipart];
+                   while (isDIGIT(*s))
+                       ++s;
+                   /* warn of loss of precision? */
+                   break;
+               }
+           }
+           --expextra;
+           part[ipart] = part[ipart] * 10 + (*s++ - '0');
        }
     }
+
+    /* combine components of mantissa */
+    for (i = 0; i <= ipart; ++i)
+       result += S_mulexp10((NV)part[ipart - i],
+               i ? offcount + (i - 1) * PARTSIZE : 0);
+
     if (seendigit && (*s == 'e' || *s == 'E')) {
-       I32 exponent = 0;
-       I32 expnegative = 0;
+       bool expnegative = 0;
        I32 bit;
        NV power;
 
@@ -4083,17 +4182,15 @@ Perl_my_atof2(pTHX_ const char* orig, NV* value)
        }
        while (isDIGIT(*s))
            exponent = exponent * 10 + (*s++ - '0');
-
-       /* now apply the exponent */
-       power = (expnegative) ? 0.1 : 10.0;
-       for (bit = 1; exponent; bit <<= 1) {
-           if (exponent & bit) {
-               exponent ^= bit;
-               result *= power;
-           }
-           power *= power;
-       }
+       if (expnegative)
+           exponent = -exponent;
     }
+
+    /* now apply the exponent */
+    exponent += expextra;
+    result = S_mulexp10(result, exponent);
+
+    /* now apply the sign */
     if (negative)
        result = -result;
     *value = result;