Add getInt<Integral>() helper

configure.ac

@@ -45,8 +45,8 @@ AC_SUBST(LIBUNIVALUE_AGE)
 LT_INIT
 LT_LANG([C++])
 
-dnl Require C++11 compiler (no GNU extensions)
-AX_CXX_COMPILE_STDCXX([11], [noext], [mandatory], [nodefault])
+dnl Require C++17 compiler (no GNU extensions)
+AX_CXX_COMPILE_STDCXX([17], [noext], [mandatory], [nodefault])
 
 case $host in
   *mingw*)

include/univalue.h

@@ -6,10 +6,13 @@
 #ifndef __UNIVALUE_H__
 #define __UNIVALUE_H__
 
+#include <charconv>
 #include <cstdint>
 #include <cstring>
 #include <map>
+#include <stdexcept>
 #include <string>
+#include <type_traits>
 #include <vector>
 
 class UniValue {
@@ -166,10 +169,24 @@ class UniValue {
     // value is of unexpected type
     const std::vector<std::string>& getKeys() const;
     const std::vector<UniValue>& getValues() const;
+    template <typename Int>
+    auto getInt() const
+    {
+        static_assert(std::is_integral<Int>::value);
+        if (typ != VNUM) {
+            throw std::runtime_error("JSON value is not an integer as expected");
+        }
+        Int result;
+        const auto [first_nonmatching, error_condition] = std::from_chars(val.data(), val.data() + val.size(), result);
+        if (first_nonmatching != val.data() + val.size() || error_condition != std::errc{}) {
+            throw std::runtime_error("JSON integer out of range");
+        }
+        return result;
+    }
     bool get_bool() const;
     const std::string& get_str() const;
-    int get_int() const;
-    int64_t get_int64() const;
+    auto get_int() const { return getInt<int>(); };
+    auto get_int64() const { return getInt<int64_t>(); };
     double get_real() const;
     const UniValue& get_obj() const;
     const UniValue& get_array() const;

lib/univalue_get.cpp

@@ -29,37 +29,6 @@ static bool ParsePrechecks(const std::string& str)
     return true;
 }
 
-bool ParseInt32(const std::string& str, int32_t *out)
-{
-    if (!ParsePrechecks(str))
-        return false;
-    char *endp = nullptr;
-    errno = 0; // strtol will not set errno if valid
-    long int n = strtol(str.c_str(), &endp, 10);
-    if(out) *out = (int32_t)n;
-    // Note that strtol returns a *long int*, so even if strtol doesn't report an 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.
-    return endp && *endp == 0 && !errno &&
-        n >= std::numeric_limits<int32_t>::min() &&
-        n <= std::numeric_limits<int32_t>::max();
-}
-
-bool ParseInt64(const std::string& str, int64_t *out)
-{
-    if (!ParsePrechecks(str))
-        return false;
-    char *endp = nullptr;
-    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))
@@ -103,26 +72,6 @@ const std::string& UniValue::get_str() const
     return getValStr();
 }
 
-int UniValue::get_int() const
-{
-    if (typ != VNUM)
-        throw std::runtime_error("JSON value is not an integer as expected");
-    int32_t retval;
-    if (!ParseInt32(getValStr(), &retval))
-        throw std::runtime_error("JSON integer out of range");
-    return retval;
-}
-
-int64_t UniValue::get_int64() const
-{
-    if (typ != VNUM)
-        throw std::runtime_error("JSON value is not an integer as expected");
-    int64_t retval;
-    if (!ParseInt64(getValStr(), &retval))
-        throw std::runtime_error("JSON integer out of range");
-    return retval;
-}
-
 double UniValue::get_real() const
 {
     if (typ != VNUM)