AppleWin/source/StrFormat.cpp

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#include "StdAfx.h"
#include "StrFormat.h"
#include <cassert>
std::string StrFormat(const char* format, ...)
{
va_list va;
va_start(va, format);
std::string s = StrFormatV(format, va);
va_end(va);
return s;
}
std::string StrFormatV(const char* format, va_list va)
{
size_t const bufsz_base = 2048; // Big enough for most cases.
char buf[bufsz_base];
#if defined(_MSC_VER) && _MSC_VER < 1900
#pragma warning(push)
#pragma warning(disable: 4996) // warning _vsnprintf() is unsafe.
// VS2013 or before, _vsnprintf() cannot return required buffer size in case of overflow.
// MSVC seems fine not needing va_copy(), otherwise va_copy() may need to be called twice
// to be accurate. Not calling va_copy() here to keep things simpler.
int len = _vsnprintf(buf, sizeof(buf), format, va);
if (len >= 0 && size_t(len) <= sizeof(buf))
{
// _vsnprintf() can fill up the full buffer without nul termination.
return std::string(buf, size_t(len)); // No overflow.
}
else
{
// Overflow, need bigger buffer.
len = _vsnprintf(NULL, 0, format, va); // Get required buffer size.
std::string s(size_t(len), '\0');
len = _vsnprintf(&(*s.begin()), s.length() + 1, format, va);
assert(size_t(len) == s.length());
return s;
}
#pragma warning(pop)
#else
// Need to call va_copy() so va can be used potentially for a second time.
// glibc on Linux *certainly* needs this while MSVC is fine without it though.
va_list va_copied;
va_copy(va_copied, va);
int len = vsnprintf(buf, sizeof(buf), format, va_copied);
va_end(va_copied);
if (len < 0)
{
return std::string(); // Error.
}
else if (size_t(len) < sizeof(buf))
{
return std::string(buf, size_t(len)); // No overflow.
}
else
{
// Overflow, need bigger buffer.
std::string s(size_t(len), '\0');
len = vsnprintf(&(*s.begin()), s.length() + 1, format, va);
assert(size_t(len) == s.length());
return s;
}
#endif
}