Fixed parsing decimals from string (#11017)

Author: vitstn

ydb/library/yql/public/decimal/ut/yql_decimal_ut.cpp

@@ -215,6 +215,8 @@ Y_UNIT_TEST_SUITE(TYqlDecimalTest) {
         UNIT_ASSERT(FromStringEx("-1e-99", 10, 2) == 0);
         UNIT_ASSERT(FromStringEx("-510e-3", 1, 0) == -1);
         UNIT_ASSERT(FromStringEx("+99E3", 5, 0) == 99000);
+        UNIT_ASSERT(FromStringEx("2.1E-130", 35, 2) == 0);
+        UNIT_ASSERT(FromStringEx("2.1E0", 35, 2) == 210);
     }
 
     Y_UNIT_TEST(TestFormStringExInvalidValues) {
@@ -225,8 +227,11 @@ Y_UNIT_TEST_SUITE(TYqlDecimalTest) {
 
         UNIT_ASSERT(IsError(FromStringEx("E2", 35, 15))); // empty
         UNIT_ASSERT(IsError(FromStringEx("E2E4", 35, 15))); // empty
-        UNIT_ASSERT(IsError(FromStringEx("12E0", 35, 15))); // zero isn't avail
         UNIT_ASSERT(IsError(FromStringEx("NANE5", 35, 15))); // nan with exp
+        UNIT_ASSERT(IsError(FromStringEx("infE5", 35, 15))); // inf with exp
+        UNIT_ASSERT(IsError(FromStringEx("-infe-5", 35, 15))); // inf with exp
+        UNIT_ASSERT(IsError(FromStringEx("2.1E0X", 35, 2))); // not fully parsed exp
+        UNIT_ASSERT(IsError(FromStringEx("2.1E+-1", 35, 2))); // two signs
     }
 
     Y_UNIT_TEST(TestSpecialAsString) {

ydb/library/yql/public/decimal/yql_decimal.cpp

@@ -3,13 +3,18 @@
 #include <cstring>
 #include <ostream>
 #include <string>
+#include <charconv>
 
 namespace NYql {
 namespace NDecimal {
 
 static const TUint128 Ten(10U);
 
 TUint128 GetDivider(ui8 scale) {
+    if (scale > MaxPrecision) {
+        return Inf();
+    }
+
     TUint128 d(1U);
     while (scale--)
         d *= Ten;
@@ -215,8 +220,16 @@ TInt128 FromStringEx(const TStringBuf& str, ui8 precision, ui8 scale) {
             if (!len)
                 return Err();
 
-            const auto exp = std::atoi(++ptr);
-            if (!exp)
+            ++ptr;
+            if (ptr != s + str.size() && *ptr == '+') {
+                ++ptr;
+                if (ptr != s + str.size() && *ptr == '-')
+                    return Err();
+            }
+
+            int exp;
+            auto [finish, ec] = std::from_chars(ptr, s + str.size(), exp);
+            if (ec != std::errc() || finish != s + str.size())
                 return Err();
 
             const int p = precision, s = int(scale) + exp;
@@ -229,8 +242,19 @@ TInt128 FromStringEx(const TStringBuf& str, ui8 precision, ui8 scale) {
                 return Err();
             }
 
+            if (IsInf(r)) {
+                auto p = str.data();
+                if (*p == '+' || *p == '-')
+                    ++p;
+
+                if (!std::isdigit(*p))
+                    return Err();
+
+                return r;
+            }
+
             if (const auto e = exp > 0 ? std::max(0, s - p) : std::min(0, s)) {
-                if (r && IsNormal(r)) {
+                if (r) {
                     if (exp > 0)
                         return Mul(r, GetDivider(+e));
                     if (exp < 0)