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[base] Fixed integral to string conversion.

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This commit is contained in:
Yuri Gorshenin 2016-03-18 01:43:14 +03:00 • committed by Sergey Yershov
parent fa8aa617d1
commit 8c4df9033c
2 changed files with 21 additions and 2 deletions
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3
base/base_tests/string_utils_test.cpp
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@ -253,6 +253,9 @@ UNIT_TEST(to_string)
TEST_EQUAL(strings::to_string(123456789123456789ULL), "123456789123456789", ());
TEST_EQUAL(strings::to_string(-987654321987654321LL), "-987654321987654321", ());
uint64_t const n = numeric_limits<uint64_t>::max();
TEST_EQUAL(strings::to_string(n), "18446744073709551615", ());
}
UNIT_TEST(to_string_dac)

20
base/string_utils.hpp
View file

@ -223,6 +223,22 @@ template <typename T> string to_string(T t)
namespace impl
{
template <typename T>
int UpperBoundOnChars()
{
// It's wrong to return just numeric_limits<T>::digits10 + [is
// signed] because digits10 for a type T is computed as:
//
// floor(log10(2 ^ (CHAR_BITS * sizeof(T)))) =
// floor(CHAR_BITS * sizeof(T) * log10(2))
//
// Therefore, due to rounding, we need to compensate possible
// error.
//
// NOTE: following code works only on two-complement systems!
return numeric_limits<T>::digits10 + is_signed<T>::value + 1;
}
template <typename T> char * to_string_digits(char * buf, T i)
{
@ -238,7 +254,7 @@ template <typename T> char * to_string_digits(char * buf, T i)
template <typename T> string to_string_signed(T i)
{
bool const negative = i < 0;
int const sz = numeric_limits<T>::digits10 + 1;
int const sz = UpperBoundOnChars<T>();
char buf[sz];
char * end = buf + sz;
char * beg = to_string_digits(end, negative ? -i : i);
@ -252,7 +268,7 @@ template <typename T> string to_string_signed(T i)
template <typename T> string to_string_unsigned(T i)
{
int const sz = numeric_limits<T>::digits10;
int const sz = UpperBoundOnChars<T>();
char buf[sz];
char * end = buf + sz;
char * beg = to_string_digits(end, i);