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Implement integer to string conversion manually

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This reduces the amount of non-standard C++ functionality pugixml may be using
by avoiding sprintf with %lld; additionally this implementation is significantly
faster (4-5x) than sprintf, mostly due to avoiding format string parsing and
stream setup that commonly happens in CRT implementations.

This comes at the expense of requiring long long division/remainder operations
if PUGIXML_USE_LONG_LONG is defined which will surely bite me one day.
This commit is contained in:
Arseny Kapoulkine 2015-09-20 00:03:02 -07:00
parent 234c2f3657
commit 131c1a159c
1 changed files with 37 additions and 15 deletions
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52
src/pugixml.cpp
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@ -4540,6 +4540,28 @@ PUGI__NS_BEGIN
} }
#endif #endif
template <typename U>
PUGI__FN char_t* integer_to_string(char_t (&buf)[64], U value, bool negative)
{
char_t* end = buf + sizeof(buf) / sizeof(buf[0]) - 1;
U rest = negative ? 0 - value : value;
*end-- = 0;
do
{
*end-- = static_cast<char_t>('0' + (rest % 10));
rest /= 10;
}
while (rest);
assert(end >= buf);
*end = '-';
return end + !negative;
}
// set value with conversion functions // set value with conversion functions
template <typename String, typename Header> template <typename String, typename Header>
PUGI__FN bool set_value_buffer(String& dest, Header& header, uintptr_t header_mask, char (&buf)[128]) PUGI__FN bool set_value_buffer(String& dest, Header& header, uintptr_t header_mask, char (&buf)[128])
@ -4557,19 +4579,19 @@ PUGI__NS_BEGIN
template <typename String, typename Header> template <typename String, typename Header>
PUGI__FN bool set_value_convert(String& dest, Header& header, uintptr_t header_mask, int value) PUGI__FN bool set_value_convert(String& dest, Header& header, uintptr_t header_mask, int value)
{ {
char buf[128]; char_t buf[64];
sprintf(buf, "%d", value); char_t* begin = integer_to_string<unsigned int>(buf, value, value < 0);
return set_value_buffer(dest, header, header_mask, buf); return strcpy_insitu(dest, header, header_mask, begin);
} }
template <typename String, typename Header> template <typename String, typename Header>
PUGI__FN bool set_value_convert(String& dest, Header& header, uintptr_t header_mask, unsigned int value) PUGI__FN bool set_value_convert(String& dest, Header& header, uintptr_t header_mask, unsigned int value)
{ {
char buf[128]; char_t buf[64];
sprintf(buf, "%u", value); char_t* begin = integer_to_string<unsigned int>(buf, value, false);
return set_value_buffer(dest, header, header_mask, buf); return strcpy_insitu(dest, header, header_mask, begin);
} }
template <typename String, typename Header> template <typename String, typename Header>
@ -4600,19 +4622,19 @@ PUGI__NS_BEGIN
template <typename String, typename Header> template <typename String, typename Header>
PUGI__FN bool set_value_convert(String& dest, Header& header, uintptr_t header_mask, long long value) PUGI__FN bool set_value_convert(String& dest, Header& header, uintptr_t header_mask, long long value)
{ {
char buf[128]; char_t buf[64];
sprintf(buf, "%lld", value); char_t* begin = integer_to_string<unsigned long long>(buf, value, value < 0);
return set_value_buffer(dest, header, header_mask, buf); return strcpy_insitu(dest, header, header_mask, begin);
} }
template <typename String, typename Header> template <typename String, typename Header>
PUGI__FN bool set_value_convert(String& dest, Header& header, uintptr_t header_mask, unsigned long long value) PUGI__FN bool set_value_convert(String& dest, Header& header, uintptr_t header_mask, unsigned long long value)
{ {
char buf[128]; char_t buf[64];
sprintf(buf, "%llu", value); char_t* begin = integer_to_string<unsigned long long>(buf, value, false);
return set_value_buffer(dest, header, header_mask, buf); return strcpy_insitu(dest, header, header_mask, begin);
} }
#endif #endif