Added overflow handling in JsonVariant::as<T>() and JsonVariant::is<T>()

src/ArduinoJson/Numbers/parseNumber.hpp

@@ -0,0 +1,147 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2019
+// MIT License
+
+#pragma once
+
+#include "../Polyfills/assert.hpp"
+#include "../Polyfills/ctype.hpp"
+#include "../Polyfills/math.hpp"
+#include "../Polyfills/type_traits.hpp"
+#include "../Variant/VariantContent.hpp"
+#include "FloatTraits.hpp"
+#include "convertNumber.hpp"
+
+namespace ARDUINOJSON_NAMESPACE {
+
+template <typename TFloat, typename TUInt>
+struct ParsedNumber {
+  ParsedNumber() : uintValue(0), floatValue(0), _type(VALUE_IS_NULL) {}
+
+  ParsedNumber(TUInt value, bool is_negative)
+      : uintValue(value),
+        floatValue(TFloat(value)),
+        _type(uint8_t(is_negative ? VALUE_IS_NEGATIVE_INTEGER
+                                  : VALUE_IS_POSITIVE_INTEGER)) {}
+  ParsedNumber(TFloat value) : floatValue(value), _type(VALUE_IS_FLOAT) {}
+
+  template <typename T>
+  T as() const {
+    switch (_type) {
+      case VALUE_IS_NEGATIVE_INTEGER:
+        return convertNegativeInteger<T>(uintValue);
+      case VALUE_IS_POSITIVE_INTEGER:
+        return convertPositiveInteger<T>(uintValue);
+      case VALUE_IS_FLOAT:
+        return convertFloat<T>(floatValue);
+      default:
+        return 0;
+    }
+  }
+
+  uint8_t type() const {
+    return _type;
+  }
+
+  TUInt uintValue;
+  TFloat floatValue;
+  uint8_t _type;
+};
+
+template <typename A, typename B>
+struct choose_largest : conditional<(sizeof(A) > sizeof(B)), A, B> {};
+
+template <typename TFloat, typename TUInt>
+inline ParsedNumber<TFloat, TUInt> parseNumber(const char *s) {
+  typedef FloatTraits<TFloat> traits;
+  typedef typename choose_largest<typename traits::mantissa_type, TUInt>::type
+      mantissa_t;
+  typedef typename traits::exponent_type exponent_t;
+  typedef ParsedNumber<TFloat, TUInt> return_type;
+
+  ARDUINOJSON_ASSERT(s != 0);
+
+  bool is_negative = false;
+  switch (*s) {
+    case '-':
+      is_negative = true;
+      s++;
+      break;
+    case '+':
+      s++;
+      break;
+  }
+
+  if (*s == 'n' || *s == 'N') return traits::nan();
+  if (*s == 'i' || *s == 'I')
+    return is_negative ? -traits::inf() : traits::inf();
+  if (!isdigit(*s) && *s != '.') return return_type();
+
+  mantissa_t mantissa = 0;
+  exponent_t exponent_offset = 0;
+  const mantissa_t maxUint = TUInt(-1);
+
+  while (isdigit(*s)) {
+    uint8_t digit = uint8_t(*s - '0');
+    if (mantissa > maxUint / 10) break;
+    mantissa *= 10;
+    if (mantissa > maxUint - digit) break;
+    mantissa += digit;
+    s++;
+  }
+
+  if (*s == '\0') return return_type(TUInt(mantissa), is_negative);
+
+  // avoid mantissa overflow
+  while (mantissa > traits::mantissa_max) {
+    mantissa /= 10;
+    exponent_offset++;
+  }
+
+  // remaing digits can't fit in the mantissa
+  while (isdigit(*s)) {
+    exponent_offset++;
+    s++;
+  }
+
+  if (*s == '.') {
+    s++;
+    while (isdigit(*s)) {
+      if (mantissa < traits::mantissa_max / 10) {
+        mantissa = mantissa * 10 + uint8_t(*s - '0');
+        exponent_offset--;
+      }
+      s++;
+    }
+  }
+
+  int exponent = 0;
+  if (*s == 'e' || *s == 'E') {
+    s++;
+    bool negative_exponent = false;
+    if (*s == '-') {
+      negative_exponent = true;
+      s++;
+    } else if (*s == '+') {
+      s++;
+    }
+
+    while (isdigit(*s)) {
+      exponent = exponent * 10 + (*s - '0');
+      if (exponent + exponent_offset > traits::exponent_max) {
+        if (negative_exponent)
+          return is_negative ? -0.0f : 0.0f;
+        else
+          return is_negative ? -traits::inf() : traits::inf();
+      }
+      s++;
+    }
+    if (negative_exponent) exponent = -exponent;
+  }
+  exponent += exponent_offset;
+
+  TFloat result = traits::make_float(static_cast<TFloat>(mantissa), exponent);
+
+  return is_negative ? -result : result;
+}
+}  // namespace ARDUINOJSON_NAMESPACE