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Handle String::toInt overflow consistently #283

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Handle String::toInt overflow consistently #283

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29 changes: 27 additions & 2 deletions api/String.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
#include "deprecated-avr-comp/avr/dtostrf.h"

#include <float.h>
#include <limits.h>

namespace arduino {

Expand Down Expand Up @@ -732,8 +733,32 @@ void String::trim(void)

long String::toInt(void) const
{
if (buffer) return atol(buffer);
return 0;
if (!buffer) return 0;

char const *p = buffer;
while (isspace(static_cast<unsigned char>(*p))) p++;

bool const negative = *p == '-';
if (negative || *p == '+') p++;

unsigned long value = 0;
unsigned long const negative_limit = static_cast<unsigned long>(-(LONG_MIN + 1L)) + 1UL;
unsigned long const limit = negative
? negative_limit
: static_cast<unsigned long>(LONG_MAX);
unsigned long const cutoff = limit / 10UL;
unsigned long const cutlim = limit % 10UL;

while (isdigit(static_cast<unsigned char>(*p))) {
unsigned long const digit = static_cast<unsigned long>(*p - '0');
if (value > cutoff || (value == cutoff && digit > cutlim)) return 0;
value = value * 10UL + digit;
p++;
}

if (!negative) return static_cast<long>(value);
if (value == negative_limit) return LONG_MIN;
return -static_cast<long>(value);
}

float String::toFloat(void) const
Expand Down
37 changes: 37 additions & 0 deletions test/src/String/test_toInt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,9 @@

#include <catch2/catch_test_macros.hpp>

#include <climits>
#include <string>

#include <api/String.h>

#include "StringPrinter.h"
Expand Down Expand Up @@ -45,3 +48,37 @@ TEST_CASE ("Testing String::toInt when string does not have a buffer", "[String-
arduino::String str(buffer);
REQUIRE(str.toInt() == 0);
}

TEST_CASE ("Testing String::toInt when string exceeds the long range", "[String-toInt-05]")
{
unsigned long const minimum_magnitude = static_cast<unsigned long>(-(LONG_MIN + 1L)) + 1UL;
std::string const one_past_maximum = std::to_string(static_cast<unsigned long>(LONG_MAX) + 1UL);
std::string const one_past_minimum = "-" + std::to_string(minimum_magnitude + 1UL);
arduino::String positive_boundary(one_past_maximum.c_str());
arduino::String negative_boundary(one_past_minimum.c_str());
arduino::String positive("999999999999999999999999999999999999");
arduino::String negative("-999999999999999999999999999999999999");

REQUIRE(positive_boundary.toInt() == 0);
REQUIRE(negative_boundary.toInt() == 0);
REQUIRE(positive.toInt() == 0);
REQUIRE(negative.toInt() == 0);
}

TEST_CASE ("Testing String::toInt at the long range limits", "[String-toInt-06]")
{
arduino::String maximum(std::to_string(LONG_MAX).c_str());
arduino::String minimum(std::to_string(LONG_MIN).c_str());

REQUIRE(maximum.toInt() == LONG_MAX);
REQUIRE(minimum.toInt() == LONG_MIN);
}

TEST_CASE ("Testing String::toInt keeps atol parsing behavior", "[String-toInt-07]")
{
arduino::String negative(" \t-123abc");
arduino::String positive("+456xyz");

REQUIRE(negative.toInt() == -123);
REQUIRE(positive.toInt() == 456);
}
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