Fix floating-point input from decimal string.

A bug was introduced in 3480230e: The divide-and-conquer method multiplies
with a power of the base, but this power is one too much if there is a
decimal point. This may happen because digits_to_I(...) is also called
from read_float(...). As a result, the number containd spurious zeros
(in the base used for reading it).

Thanks to Thomas Luthe <tluthe@physik.uni-bielefeld.de>.

src/integer/conv/cl_I_from_digits.cc

@@ -18,7 +18,7 @@ static const cl_I digits_to_I_base2 (const char * MSBptr, uintC len, uintD base)
 {
 	// base is a power of two: write the digits from least significant
 	// to most significant into the result NUDS. Result needs
-	// 1+ceiling(len*log(base)/(intDsize*log(2))) or some more digits
+	// 1+ceiling(len*log(base)/(intDsize*log(2))) or some more digits.
 	CL_ALLOCA_STACK;
 	var uintD* erg_MSDptr;
 	var uintC erg_len;
@@ -64,7 +64,7 @@ static const cl_I digits_to_I_base2 (const char * MSBptr, uintC len, uintD base)
 
 static const cl_I digits_to_I_baseN (const char * MSBptr, uintC len, uintD base)
 {
-	// base is not a power of two: Add digits one by one. Result nees
+	// base is not a power of two: Add digits one by one. Result needs
 	// 1+ceiling(len*log(base)/(intDsize*log(2))) or some more digits.
 	CL_ALLOCA_STACK;
 	var uintD* erg_MSDptr;
@@ -121,7 +121,6 @@ static const cl_I digits_to_I_baseN (const char * MSBptr, uintC len, uintD base)
 		var uintD factor = 1;
 		while (chx < power_table[base-2].k && len > 0) {
 			var uintB ch = *(const uintB *)MSBptr; MSBptr++; // next character
-			if (ch!='.') { // skip decimal point
 			// Compute value of ('0'-'9','A'-'Z','a'-'z'):
 			ch = ch-'0';
 			if (ch > '9'-'0') { // not a digit?
@@ -133,7 +132,6 @@ static const cl_I digits_to_I_baseN (const char * MSBptr, uintC len, uintD base)
 			factor = factor*base;
 			newdigit = base*newdigit+ch;
 			chx++;
-			}
 			len--;
 		}
 		var uintD carry = mulusmall_loop_lsp(factor,erg_LSDptr,erg_len,newdigit);
@@ -146,11 +144,8 @@ static const cl_I digits_to_I_baseN (const char * MSBptr, uintC len, uintD base)
 	return NUDS_to_I(erg_MSDptr,erg_len);
 }
 
-const cl_I digits_to_I (const char * MSBptr, uintC len, uintD base)
+static const cl_I digits_to_I_divconq (const char * MSBptr, uintC len, uintD base)
 {
-	if ((base & (base-1)) == 0) {
-		return digits_to_I_base2(MSBptr, len, base);
-	} else {
 	// This is quite insensitive to the breakeven point.
 	// On a 1GHz Athlon I get approximately:
 	//   base  3: breakeven around 25000
@@ -167,12 +162,33 @@ const cl_I digits_to_I (const char * MSBptr, uintC len, uintD base)
 				break;
 			len_B = len_B*2;
 		}
-			return digits_to_I(MSBptr,len-len_B,base)*p->base_pow
-			      +digits_to_I(MSBptr+len-len_B,len_B,base);
+			return digits_to_I_divconq(MSBptr,len-len_B,base) * p->base_pow
+			     + digits_to_I_divconq(MSBptr+len-len_B,len_B,base);
 	} else {
 		return digits_to_I_baseN(MSBptr, len, base);
 	}
 }
+
+const cl_I digits_to_I (const char * MSBptr, uintC len, uintD base)
+{
+	if ((base & (base-1)) == 0) {
+		return digits_to_I_base2(MSBptr, len, base);
+	} else {
+		// digits_to_I_divconq cannot handle decimal points, so remove it here
+		CL_ALLOCA_STACK;
+		const uintD * digits_copy;
+		num_stack_alloc(len,,digits_copy=);
+		char * copy_ptr = (char *)digits_copy;
+		uintC n = 0;
+		for (uintC i = 0; i < len; ++i) {
+			const char ch = MSBptr[i];
+			if (ch != '.') { // skip decimal point
+				copy_ptr[n] = ch;
+				n++;
+			}
+		}
+		return digits_to_I_divconq((const char*)digits_copy, n, base);
+	}
 }
 
 }  // namespace cln