internal/ceres/stringprintf.cc

// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2015 Google Inc. All rights reserved.
// http://ceres-solver.org/
//
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// modification, are permitted provided that the following conditions are met:
//
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//   this list of conditions and the following disclaimer.
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//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution.
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//   used to endorse or promote products derived from this software without
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// Author: Sanjay Ghemawat

#include "ceres/stringprintf.h"

#include <cerrno>
#include <cstdarg>  // For va_list and related operations
#include <cstdio>   // MSVC requires this for _vsnprintf
#include <string>
#include <vector>

#include "ceres/internal/export.h"

namespace ceres::internal {

using std::string;

void StringAppendV(string* dst, const char* format, va_list ap) {
  // First try with a small fixed size buffer
  char space[1024];

  // It's possible for methods that use a va_list to invalidate
  // the data in it upon use.  The fix is to make a copy
  // of the structure before using it and use that copy instead.
  va_list backup_ap;
  va_copy(backup_ap, ap);
  int result = vsnprintf(space, sizeof(space), format, backup_ap);
  va_end(backup_ap);

  if (result < sizeof(space)) {
    if (result >= 0) {
      // Normal case -- everything fit.
      dst->append(space, result);
      return;
    }

#if defined(_MSC_VER)
    // Error or MSVC running out of space.  MSVC 8.0 and higher
    // can be asked about space needed with the special idiom below:
    va_copy(backup_ap, ap);
    result = vsnprintf(nullptr, 0, format, backup_ap);
    va_end(backup_ap);
#endif

    if (result < 0) {
      // Just an error.
      return;
    }
  }

  // Increase the buffer size to the size requested by vsnprintf,
  // plus one for the closing \0.
  int length = result + 1;
  char* buf = new char[length];

  // Restore the va_list before we use it again
  va_copy(backup_ap, ap);
  result = vsnprintf(buf, length, format, backup_ap);
  va_end(backup_ap);

  if (result >= 0 && result < length) {
    // It fit
    dst->append(buf, result);
  }
  delete[] buf;
}

string StringPrintf(const char* format, ...) {
  va_list ap;
  va_start(ap, format);
  string result;
  StringAppendV(&result, format, ap);
  va_end(ap);
  return result;
}

const string& SStringPrintf(string* dst, const char* format, ...) {
  va_list ap;
  va_start(ap, format);
  dst->clear();
  StringAppendV(dst, format, ap);
  va_end(ap);
  return *dst;
}

void StringAppendF(string* dst, const char* format, ...) {
  va_list ap;
  va_start(ap, format);
  StringAppendV(dst, format, ap);
  va_end(ap);
}

}  // namespace ceres::internal