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