util: Add ParseInt64 and ParseDouble functions

Strict parsing functions for other numeric types.

- ParseInt64 analogous to ParseInt32, but for 64-bit values.
- ParseDouble for doubles.
- Make all three Parse* functions more strict (e.g. reject whitespace on
  the inside)

Also add tests.

src/utilstrencodings.cpp

@@ -416,12 +416,25 @@ string DecodeBase32(const string& str)
     return (vchRet.size() == 0) ? string() : string((const char*)&vchRet[0], vchRet.size());
 }
 
+static bool ParsePrechecks(const std::string& str)
+{
+    if (str.empty()) // No empty string allowed
+        return false;
+    if (str.size() >= 1 && (isspace(str[0]) || isspace(str[str.size()-1]))) // No padding allowed
+        return false;
+    if (str.size() != strlen(str.c_str())) // No embedded NUL characters allowed
+        return false;
+    return true;
+}
+
 bool ParseInt32(const std::string& str, int32_t *out)
 {
+    if (!ParsePrechecks(str))
+        return false;
     char *endp = NULL;
     errno = 0; // strtol will not set errno if valid
     long int n = strtol(str.c_str(), &endp, 10);
-    if(out) *out = (int)n;
+    if(out) *out = (int32_t)n;
     // Note that strtol returns a *long int*, so even if strtol doesn't report a over/underflow
     // we still have to check that the returned value is within the range of an *int32_t*. On 64-bit
     // platforms the size of these types may be different.
@@ -430,6 +443,34 @@ bool ParseInt32(const std::string& str, int32_t *out)
         n <= std::numeric_limits<int32_t>::max();
 }
 
+bool ParseInt64(const std::string& str, int64_t *out)
+{
+    if (!ParsePrechecks(str))
+        return false;
+    char *endp = NULL;
+    errno = 0; // strtoll will not set errno if valid
+    long long int n = strtoll(str.c_str(), &endp, 10);
+    if(out) *out = (int64_t)n;
+    // Note that strtoll returns a *long long int*, so even if strtol doesn't report a over/underflow
+    // we still have to check that the returned value is within the range of an *int64_t*.
+    return endp && *endp == 0 && !errno &&
+        n >= std::numeric_limits<int64_t>::min() &&
+        n <= std::numeric_limits<int64_t>::max();
+}
+
+bool ParseDouble(const std::string& str, double *out)
+{
+    if (!ParsePrechecks(str))
+        return false;
+    if (str.size() >= 2 && str[0] == '0' && str[1] == 'x') // No hexadecimal floats allowed
+        return false;
+    char *endp = NULL;
+    errno = 0; // strtod will not set errno if valid
+    double n = strtod(str.c_str(), &endp);
+    if(out) *out = n;
+    return endp && *endp == 0 && !errno;
+}
+
 std::string FormatParagraph(const std::string in, size_t width, size_t indent)
 {
     std::stringstream out;