strprintf.hpp

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// SPDX-License-Identifier: AGPL-3.0-only
// Copyright (c) 2026 ForestHub. All rights reserved.
// For commercial licensing, visit https://github.com/ForestHubAI/fh-sdk
 
#ifndef FORESTHUB_UTIL_STRPRINTF_HPP
#define FORESTHUB_UTIL_STRPRINTF_HPP

 
#include <cstdarg>
#include <cstdio>
#include <string>
 
namespace foresthub {
namespace util {

#if defined(__GNUC__) || defined(__clang__)
// GCC/Clang: Enable compile-time format string checking.
// Argument indices: 1 = format string, 2 = first vararg (free function, no implicit 'this')
inline std::string StrPrintf(const char* fmt, ...) __attribute__((format(printf, 1, 2)));
#else
inline std::string StrPrintf(const char* fmt, ...);
#endif
 
inline std::string StrPrintf(const char* fmt, ...) {
    va_list args1, args2;
    va_start(args1, fmt);
    va_copy(args2, args1);
 
    int len = vsnprintf(nullptr, 0, fmt, args1);  // Pass 1: measure exact size
    va_end(args1);
 
    if (len <= 0) {
        va_end(args2);
        return "";
    }
 
    std::string result(static_cast<size_t>(len), '\0');               // ONE allocation, exact size
    vsnprintf(&result[0], static_cast<size_t>(len) + 1, fmt, args2);  // Pass 2: write
    va_end(args2);
 
    return result;  // RVO - no copy
}
 
}  // namespace util
}  // namespace foresthub
 
#endif  // FORESTHUB_UTIL_STRPRINTF_HPP