stringprintf.h

// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2015 Google Inc. All rights reserved.
// http://ceres-solver.org/
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// Author: Sanjay Ghemawat
//
// Printf variants that place their output in a C++ string.
//
// Usage:
//      string result = StringPrintf("%d %s\n", 10, "hello");
//      SStringPrintf(&result, "%d %s\n", 10, "hello");
//      StringAppendF(&result, "%d %s\n", 20, "there");

#ifndef PALLAS_INTERNAL_STRINGPRINTF_H_
#define PALLAS_INTERNAL_STRINGPRINTF_H_

#include <cstdarg>
#include <string>

namespace pallas {
    namespace internal {

#if (defined(__GNUC__) || defined(__clang__))
// Tell the compiler to do printf format string checking if the compiler
// supports it; see the 'format' attribute in
// <http://gcc.gnu.org/onlinedocs/gcc-4.3.0/gcc/Function-Attributes.html>.
//
// N.B.: As the GCC manual states, "[s]ince non-static C++ methods
// have an implicit 'this' argument, the arguments of such methods
// should be counted from two, not one."
#define CERES_PRINTF_ATTRIBUTE(string_index, first_to_check) \
    __attribute__((__format__ (__printf__, string_index, first_to_check)))
#define CERES_SCANF_ATTRIBUTE(string_index, first_to_check) \
    __attribute__((__format__ (__scanf__, string_index, first_to_check)))
#else
#define CERES_PRINTF_ATTRIBUTE(string_index, first_to_check)
#endif

// Return a C++ string.
        extern std::string StringPrintf(const char* format, ...)
                // Tell the compiler to do printf format string checking.
                CERES_PRINTF_ATTRIBUTE(1, 2);

// Store result into a supplied string and return it.
        extern const std::string& SStringPrintf(std::string* dst, const char* format, ...)
                // Tell the compiler to do printf format string checking.
                CERES_PRINTF_ATTRIBUTE(2, 3);

// Append result to a supplied string.
        extern void StringAppendF(std::string* dst, const char* format, ...)
                // Tell the compiler to do printf format string checking.
                CERES_PRINTF_ATTRIBUTE(2, 3);

// Lower-level routine that takes a va_list and appends to a specified string.
// All other routines are just convenience wrappers around it.
        extern void StringAppendV(std::string* dst, const char* format, va_list ap);

#undef CERES_PRINTF_ATTRIBUTE

    }  // namespace internal
}  // namespace pallas

#endif  // PALLAS_INTERNAL_STRINGPRINTF_H_