vpVideoReader.cpp

/****************************************************************************
 *
 * This file is part of the ViSP software.
 * Copyright (C) 2005 - 2017 by Inria. All rights reserved.
 *
 * This software is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * See the file LICENSE.txt at the root directory of this source
 * distribution for additional information about the GNU GPL.
 *
 * For using ViSP with software that can not be combined with the GNU
 * GPL, please contact Inria about acquiring a ViSP Professional
 * Edition License.
 *
 * See http://visp.inria.fr for more information.
 *
 * This software was developed at:
 * Inria Rennes - Bretagne Atlantique
 * Campus Universitaire de Beaulieu
 * 35042 Rennes Cedex
 * France
 *
 * If you have questions regarding the use of this file, please contact
 * Inria at visp@inria.fr
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Description:
 * Read videos and image sequences.
 *
 * Authors:
 * Nicolas Melchior
 * Fabien Spindler
 *
 *****************************************************************************/

#include <visp3/core/vpDebug.h>
#include <visp3/core/vpIoTools.h>
#include <visp3/io/vpVideoReader.h>

#include <cctype>
#include <fstream>
#include <iostream>
#include <limits> // numeric_limits

vpVideoReader::vpVideoReader()
  : vpFrameGrabber(), imSequence(NULL),
#if VISP_HAVE_OPENCV_VERSION >= 0x020100
    capture(), frame(),
#endif
    formatType(FORMAT_UNKNOWN), initFileName(false), isOpen(false), frameCount(0), firstFrame(0), lastFrame(0),
    firstFrameIndexIsSet(false), lastFrameIndexIsSet(false), frameStep(1), frameRate(0.)
{
}

vpVideoReader::~vpVideoReader()
{
  if (imSequence != NULL) {
    delete imSequence;
  }
}

void vpVideoReader::setFileName(const char *filename)
{
  if ((!filename) || (*filename == '\0')) {
    vpERROR_TRACE("filename empty ");
    throw(vpImageException(vpImageException::noFileNameError, "filename empty "));
  }

  if (strlen(filename) >= FILENAME_MAX) {
    throw(vpException(vpException::memoryAllocationError, "Not enough memory to initialize the file name"));
  }

  strcpy(this->fileName, filename);

  formatType = getFormat(fileName);

  if (formatType == FORMAT_UNKNOWN) {
    throw(vpException(vpException::badValue, "Filename extension not supported"));
  }

  // checking image name format
  if (isImageExtensionSupported()) {
    std::string format = vpIoTools::getName(fileName);
    if (!checkImageNameFormat(format)) {
      throw(vpException(vpException::badValue, "Format of image name wasn't recognized: %s", format.c_str()));
    }
  }

  initFileName = true;
}

void vpVideoReader::setFileName(const std::string &filename) { setFileName(filename.c_str()); }

void vpVideoReader::getProperties()
{
  if (!initFileName) {
    throw(vpImageException(vpImageException::noFileNameError, "The generic filename has to be set"));
  }

  if (isImageExtensionSupported()) {
    imSequence = new vpDiskGrabber;
    imSequence->setGenericName(fileName);
    imSequence->setStep(frameStep);
    if (firstFrameIndexIsSet) {
      imSequence->setImageNumber(firstFrame);
    }
    frameRate = -1.;
  } else if (isVideoExtensionSupported()) {
#if VISP_HAVE_OPENCV_VERSION >= 0x020100
    capture.open(fileName);

    if (!capture.isOpened()) {
      throw(vpException(vpException::ioError, "Could not open the video %s with OpenCV", fileName));
    }
#if VISP_HAVE_OPENCV_VERSION >= 0x030000
    width = (unsigned int)capture.get(cv::CAP_PROP_FRAME_WIDTH);
    height = (unsigned int)capture.get(cv::CAP_PROP_FRAME_HEIGHT);
    frameRate = (double)capture.get(cv::CAP_PROP_FPS);
#else
    width = (unsigned int)capture.get(CV_CAP_PROP_FRAME_WIDTH);
    height = (unsigned int)capture.get(CV_CAP_PROP_FRAME_HEIGHT);
    frameRate = capture.get(CV_CAP_PROP_FPS);
#endif

#else
    throw(vpException(vpException::fatalError, "To read video files ViSP should be build with opencv "
                                               "3rd >= 2.1.0 party libraries."));
#endif
  } else if (formatType == FORMAT_UNKNOWN) {
    // vpERROR_TRACE("The format of the file does not correspond to a readable
    // format.");
    throw(vpException(vpException::fatalError, "The format of the file does "
                                               "not correspond to a readable "
                                               "format supported by ViSP."));
  }

  findFirstFrameIndex();
  isOpen = true;
  findLastFrameIndex();
}

void vpVideoReader::open(vpImage<vpRGBa> &I)
{
  getProperties();

  frameCount = firstFrame;
  if (!getFrame(I, firstFrame)) {
    throw(vpException(vpException::ioError, "Could not read the video first frame"));
  }

  // Rewind to the first frame since open() should not increase the frame
  // counter
  frameCount = firstFrame;

  if (isVideoExtensionSupported()) {
#if VISP_HAVE_OPENCV_VERSION >= 0x020100

#if VISP_HAVE_OPENCV_VERSION >= 0x030000
    capture.set(cv::CAP_PROP_POS_FRAMES, firstFrame - 1);
#else
    capture.set(CV_CAP_PROP_POS_FRAMES, firstFrame - 1);
#endif
    frameCount--;
#endif
  }
}

void vpVideoReader::open(vpImage<unsigned char> &I)
{
  getProperties();

  frameCount = firstFrame;
  if (!getFrame(I, firstFrame)) {
    throw(vpException(vpException::ioError, "Could not read the video first frame"));
  }

  // Rewind to the first frame since open() should not increase the frame
  // counter
  frameCount = firstFrame;

  if (isVideoExtensionSupported()) {
#if VISP_HAVE_OPENCV_VERSION >= 0x020100

#if VISP_HAVE_OPENCV_VERSION >= 0x030000
    capture.set(cv::CAP_PROP_POS_FRAMES, firstFrame - 1);
#else
    capture.set(CV_CAP_PROP_POS_FRAMES, firstFrame - 1);
#endif
    frameCount--;
#endif
  }
}

void vpVideoReader::acquire(vpImage<vpRGBa> &I)
{
  if (!isOpen) {
    open(I);
  }

  // getFrame(I,frameCount);
  if (imSequence != NULL) {
    imSequence->setStep(frameStep);
    imSequence->acquire(I);
    frameCount = imSequence->getImageNumber();
    if (frameCount + frameStep > lastFrame) {
      imSequence->setImageNumber(frameCount);
    } else if (frameCount + frameStep < firstFrame) {
      imSequence->setImageNumber(frameCount);
    }
  }
#if VISP_HAVE_OPENCV_VERSION >= 0x020100
  else {
    capture >> frame;
    if (frameStep == 1) {
      frameCount++;
    } else {
#if VISP_HAVE_OPENCV_VERSION >= 0x030000
      frameCount = (long)capture.get(cv::CAP_PROP_POS_FRAMES);
      if (frameStep > 0) {
        if (frameCount + frameStep <= lastFrame) {
          capture.set(cv::CAP_PROP_POS_FRAMES, frameCount + frameStep - 1);
        } else {
          capture.set(cv::CAP_PROP_POS_FRAMES, frameCount - 1);
        }
      } else if (frameStep < 0) {
        if (frameCount + frameStep >= firstFrame) {
          capture.set(cv::CAP_PROP_POS_FRAMES, frameCount + frameStep - 1);
        } else {
          capture.set(cv::CAP_PROP_POS_FRAMES, firstFrame - 1);
        }
      }
#else
      frameCount = (long)capture.get(CV_CAP_PROP_POS_FRAMES);
      if (frameStep > 0) {
        if (frameCount + frameStep <= lastFrame) {
          capture.set(CV_CAP_PROP_POS_FRAMES, frameCount + frameStep - 1);
        } else {
          capture.set(CV_CAP_PROP_POS_FRAMES, frameCount - 1);
        }
      } else if (frameStep < 0) {
        if (frameCount + frameStep >= firstFrame) {
          capture.set(CV_CAP_PROP_POS_FRAMES, frameCount + frameStep - 1);
        } else {
          capture.set(CV_CAP_PROP_POS_FRAMES, firstFrame - 1);
        }
      }
#endif
    }

    if (frame.empty())
      setLastFrameIndex(frameCount - frameStep);
    else
      vpImageConvert::convert(frame, I);
  }
#endif
}

void vpVideoReader::acquire(vpImage<unsigned char> &I)
{
  if (!isOpen) {
    open(I);
  }

  if (imSequence != NULL) {
    imSequence->setStep(frameStep);
    imSequence->acquire(I);
    frameCount = imSequence->getImageNumber();
    if (frameCount + frameStep > lastFrame) {
      imSequence->setImageNumber(frameCount);
    } else if (frameCount + frameStep < firstFrame) {
      imSequence->setImageNumber(frameCount);
    }
  }
#if VISP_HAVE_OPENCV_VERSION >= 0x020100
  else {
    capture >> frame;
    if (frameStep == 1) {
      frameCount++;
    } else {
#if VISP_HAVE_OPENCV_VERSION >= 0x030000
      frameCount = (long)capture.get(cv::CAP_PROP_POS_FRAMES);
      if (frameStep > 0) {
        if (frameCount + frameStep <= lastFrame) {
          capture.set(cv::CAP_PROP_POS_FRAMES, frameCount + frameStep - 1);
        } else {
          capture.set(cv::CAP_PROP_POS_FRAMES, frameCount - 1);
        }
      } else if (frameStep < 0) {
        if (frameCount + frameStep >= firstFrame) {
          capture.set(cv::CAP_PROP_POS_FRAMES, frameCount + frameStep - 1);
        } else {
          capture.set(cv::CAP_PROP_POS_FRAMES, firstFrame - 1);
        }
      }
#else
      frameCount = (long)capture.get(CV_CAP_PROP_POS_FRAMES);
      if (frameStep > 0) {
        if (frameCount + frameStep <= lastFrame) {
          capture.set(CV_CAP_PROP_POS_FRAMES, frameCount + frameStep - 1);
        } else {
          capture.set(CV_CAP_PROP_POS_FRAMES, frameCount - 1);
        }
      } else if (frameStep < 0) {
        if (frameCount + frameStep >= firstFrame) {
          capture.set(CV_CAP_PROP_POS_FRAMES, frameCount + frameStep - 1);
        } else {
          capture.set(CV_CAP_PROP_POS_FRAMES, firstFrame - 1);
        }
      }
#endif
    }

    if (frame.empty())
      setLastFrameIndex(frameCount - frameStep);
    else
      vpImageConvert::convert(frame, I);
  }
#endif
}

bool vpVideoReader::getFrame(vpImage<vpRGBa> &I, long frame_index)
{
  if (imSequence != NULL) {
    try {
      imSequence->acquire(I, frame_index);
      width = I.getWidth();
      height = I.getHeight();
      frameCount = imSequence->getImageNumber();
      imSequence->setImageNumber(frameCount); // to not increment vpDiskGrabber next image
      if (frameCount + frameStep > lastFrame) {
        imSequence->setImageNumber(frameCount);
      } else if (frameCount + frameStep < firstFrame) {
        imSequence->setImageNumber(frameCount);
      }
    } catch (...) {
      vpERROR_TRACE("Couldn't find the %u th frame", frame_index);
      return false;
    }
  } else {
#if defined(VISP_HAVE_OPENCV) && (VISP_HAVE_OPENCV_VERSION >= 0x030000)
    if (!capture.set(cv::CAP_PROP_POS_FRAMES, frame_index)) {
      vpERROR_TRACE("Couldn't find the %ld th frame", frame_index);
      return false;
    }

    capture >> frame;
    frameCount = frame_index + frameStep; // next index
    capture.set(cv::CAP_PROP_POS_FRAMES, frameCount);
    if (frame.empty()) {
      // New trial that makes things working with opencv 3.0.0
      capture >> frame;
      if (frame.empty()) {
        setLastFrameIndex(frameCount - frameStep);
        return false;
      } else {
        vpImageConvert::convert(frame, I);
      }
    } else
      vpImageConvert::convert(frame, I);
#elif defined(VISP_HAVE_OPENCV) && (VISP_HAVE_OPENCV_VERSION >= 0x020100)
    if (!capture.set(CV_CAP_PROP_POS_FRAMES, frame_index)) {
      vpERROR_TRACE("Couldn't find the %ld th frame", frame_index);
      return false;
    }

    capture >> frame;
    frameCount = frame_index + frameStep; // next index
    capture.set(CV_CAP_PROP_POS_FRAMES, frameCount);
    if (frame.empty())
      setLastFrameIndex(frameCount - frameStep);
    else
      vpImageConvert::convert(frame, I);
#endif
  }
  return true;
}

bool vpVideoReader::getFrame(vpImage<unsigned char> &I, long frame_index)
{
  if (imSequence != NULL) {
    try {
      imSequence->acquire(I, frame_index);
      width = I.getWidth();
      height = I.getHeight();
      frameCount = imSequence->getImageNumber();
      imSequence->setImageNumber(frameCount); // to not increment vpDiskGrabber next image
      if (frameCount + frameStep > lastFrame) {
        imSequence->setImageNumber(frameCount);
      } else if (frameCount + frameStep < firstFrame) {
        imSequence->setImageNumber(frameCount);
      }
    } catch (...) {
      vpERROR_TRACE("Couldn't find the %u th frame", frame_index);
      return false;
    }
  } else {
#if VISP_HAVE_OPENCV_VERSION >= 0x030000
    if (!capture.set(cv::CAP_PROP_POS_FRAMES, frame_index)) {
      vpERROR_TRACE("Couldn't find the %ld th frame", frame_index);
      return false;
    }
    capture >> frame;
    if (frame.empty()) {
      // New trial that makes things working with opencv 3.0.0
      capture >> frame;
      if (frame.empty()) {
        setLastFrameIndex(frameCount - frameStep);
        return false;
      } else {
        vpImageConvert::convert(frame, I);
      }
    } else {
      vpImageConvert::convert(frame, I);
    }
#elif VISP_HAVE_OPENCV_VERSION >= 0x020100
    if (!capture.set(CV_CAP_PROP_POS_FRAMES, frame_index)) {
      vpERROR_TRACE("Couldn't find the %ld th frame",
                    frame_index); // next index
      return false;
    }
    capture >> frame;
    frameCount = (long)capture.get(CV_CAP_PROP_POS_FRAMES);
    if (frameStep > 1) {
      frameCount += frameStep - 1; // next index
      capture.set(CV_CAP_PROP_POS_FRAMES, frameCount);
    } else if (frameStep < -1) {
      frameCount += frameStep - 1; // next index
      capture.set(CV_CAP_PROP_POS_FRAMES, frameCount);
    }
    if (frame.empty())
      setLastFrameIndex(frameCount - frameStep);
    else
      vpImageConvert::convert(frame, I);
#endif
  }
  return true;
}

vpVideoReader::vpVideoFormatType vpVideoReader::getFormat(const char *filename)
{
  std::string sfilename(filename);

  std::string ext = vpVideoReader::getExtension(sfilename);

  if (ext.compare(".PGM") == 0)
    return FORMAT_PGM;
  else if (ext.compare(".pgm") == 0)
    return FORMAT_PGM;
  else if (ext.compare(".PPM") == 0)
    return FORMAT_PPM;
  else if (ext.compare(".ppm") == 0)
    return FORMAT_PPM;
  else if (ext.compare(".JPG") == 0)
    return FORMAT_JPEG;
  else if (ext.compare(".jpg") == 0)
    return FORMAT_JPEG;
  else if (ext.compare(".JPEG") == 0)
    return FORMAT_JPEG;
  else if (ext.compare(".jpeg") == 0)
    return FORMAT_JPEG;
  else if (ext.compare(".PNG") == 0)
    return FORMAT_PNG;
  else if (ext.compare(".png") == 0)
    return FORMAT_PNG;
  else if (ext.compare(".TIFF") == 0)
    return FORMAT_TIFF;
  else if (ext.compare(".tiff") == 0)
    return FORMAT_TIFF;
  else if (ext.compare(".BMP") == 0)
    return FORMAT_BMP;
  else if (ext.compare(".bmp") == 0)
    return FORMAT_BMP;
  else if (ext.compare(".DIB") == 0)
    return FORMAT_DIB;
  else if (ext.compare(".dib") == 0)
    return FORMAT_DIB;
  else if (ext.compare(".PBM") == 0)
    return FORMAT_PBM;
  else if (ext.compare(".pbm") == 0)
    return FORMAT_PBM;
  else if (ext.compare(".SR") == 0)
    return FORMAT_PBM;
  else if (ext.compare(".sr") == 0)
    return FORMAT_PBM;
  else if (ext.compare(".RAS") == 0)
    return FORMAT_RASTER;
  else if (ext.compare(".ras") == 0)
    return FORMAT_RASTER;
  else if (ext.compare(".JP2") == 0)
    return FORMAT_JPEG2000;
  else if (ext.compare(".jp2") == 0)
    return FORMAT_JPEG2000;
  else if (ext.compare(".AVI") == 0)
    return FORMAT_AVI;
  else if (ext.compare(".avi") == 0)
    return FORMAT_AVI;
  else if (ext.compare(".MPEG") == 0)
    return FORMAT_MPEG;
  else if (ext.compare(".mpeg") == 0)
    return FORMAT_MPEG;
  else if (ext.compare(".MPG") == 0)
    return FORMAT_MPEG;
  else if (ext.compare(".mpg") == 0)
    return FORMAT_MPEG;
  else if (ext.compare(".MPEG4") == 0)
    return FORMAT_MPEG4;
  else if (ext.compare(".mpeg4") == 0)
    return FORMAT_MPEG4;
  else if (ext.compare(".MP4") == 0)
    return FORMAT_MPEG4;
  else if (ext.compare(".mp4") == 0)
    return FORMAT_MPEG4;
  else if (ext.compare(".MOV") == 0)
    return FORMAT_MOV;
  else if (ext.compare(".mov") == 0)
    return FORMAT_MOV;
  else if (ext.compare(".OGV") == 0)
    return FORMAT_OGV;
  else if (ext.compare(".ogv") == 0)
    return FORMAT_OGV;
  else if (ext.compare(".WMV") == 0)
    return FORMAT_WMV;
  else if (ext.compare(".wmv") == 0)
    return FORMAT_WMV;
  else if (ext.compare(".FLV") == 0)
    return FORMAT_FLV;
  else if (ext.compare(".flv") == 0)
    return FORMAT_FLV;
  else if (ext.compare(".MKV") == 0)
    return FORMAT_MKV;
  else if (ext.compare(".mkv") == 0)
    return FORMAT_MKV;
  else
    return FORMAT_UNKNOWN;
}

// return the extension of the file including the dot
std::string vpVideoReader::getExtension(const std::string &filename)
{
  // extract the extension
  size_t dot = filename.find_last_of(".");
  std::string ext = filename.substr(dot, filename.size() - 1);
  return ext;
}

void vpVideoReader::findLastFrameIndex()
{
  if (!isOpen) {
    vpERROR_TRACE("Use the open method before");
    throw(vpException(vpException::notInitialized, "file not yet opened"));
  }

  if (imSequence != NULL) {
    if (!lastFrameIndexIsSet) {
      std::string imageNameFormat = vpIoTools::getName(std::string(fileName));
      std::string dirName = vpIoTools::getParent(std::string(fileName));
      if (dirName == "") {
        dirName = ".";
      }
      std::vector<std::string> files = vpIoTools::getDirFiles(dirName);
      lastFrame = 0;
      for (size_t i = 0; i < files.size(); i++) {
        // Checking that file name satisfies image format,
        // specified by imageNameFormat, and extracting imageIndex
        long imageIndex = extractImageIndex(files[i], imageNameFormat);
        if ((imageIndex != -1) && (imageIndex > lastFrame)) {
          lastFrame = imageIndex;
        }
      }
    }
  }

#if VISP_HAVE_OPENCV_VERSION >= 0x030000
  else if (!lastFrameIndexIsSet) {
    lastFrame = (long)capture.get(cv::CAP_PROP_FRAME_COUNT);
    if (lastFrame <= 2) // with tutorial/matching/video-postcard.mpeg it
                        // return 2 with OpenCV 3.0.0
    {
      // std::cout << "Warning: Problem with cv::CAP_PROP_FRAME_COUNT. We set
      // video last frame to an arbitrary value (1000)." << std::endl;
      lastFrame = 100000; // Set lastFrame to an arbitrary value
    }
  }
#elif VISP_HAVE_OPENCV_VERSION >= 0x020100
  else if (!lastFrameIndexIsSet) {
    lastFrame = (long)capture.get(CV_CAP_PROP_FRAME_COUNT);
    if (lastFrame <= 2) // with tutorial/matching/video-postcard.mpeg it
                        // return 2 with OpenCV 2.4.10
    {
      // std::cout << "Warning: Problem with CV_CAP_PROP_FRAME_COUNT. We set
      // video last frame to an arbitrary value (1000)." << std::endl;
      lastFrame = 100000; // Set lastFrame to an arbitrary value
    }
  }
#endif
}

void vpVideoReader::findFirstFrameIndex()
{
  if (imSequence != NULL) {
    if (!firstFrameIndexIsSet) {
      std::string imageNameFormat = vpIoTools::getName(std::string(fileName));
      std::string dirName = vpIoTools::getParent(std::string(fileName));
      if (dirName == "") {
        dirName = ".";
      }
      std::vector<std::string> files = vpIoTools::getDirFiles(dirName);
      firstFrame = -1;
      for (size_t i = 0; i < files.size(); i++) {
        // Checking that file name satisfies image format, specified by
        // imageNameFormat, and extracting imageIndex
        long imageIndex = extractImageIndex(files[i], imageNameFormat);
        if ((imageIndex != -1) && (imageIndex < firstFrame || firstFrame == -1)) {
          firstFrame = imageIndex;
        }
      }
      imSequence->setImageNumber(firstFrame);
    }
  }
#if VISP_HAVE_OPENCV_VERSION >= 0x020100
  else if (!firstFrameIndexIsSet) {
    firstFrame = 1L;
  }
#endif
}

bool vpVideoReader::isImageExtensionSupported()
{
  return (formatType == FORMAT_PGM || formatType == FORMAT_PPM || formatType == FORMAT_JPEG ||
          formatType == FORMAT_PNG || formatType == FORMAT_TIFF || formatType == FORMAT_BMP ||
          formatType == FORMAT_DIB || formatType == FORMAT_PBM || formatType == FORMAT_RASTER ||
          formatType == FORMAT_JPEG2000);
}

bool vpVideoReader::isVideoExtensionSupported()
{
  return (formatType == FORMAT_AVI || formatType == FORMAT_MPEG || formatType == FORMAT_MPEG4 ||
          formatType == FORMAT_MOV || formatType == FORMAT_OGV || formatType == FORMAT_WMV ||
          formatType == FORMAT_FLV || formatType == FORMAT_MKV);
}

vpVideoReader &vpVideoReader::operator>>(vpImage<unsigned char> &I)
{
  this->acquire(I);
  return *this;
}

vpVideoReader &vpVideoReader::operator>>(vpImage<vpRGBa> &I)
{
  this->acquire(I);
  return *this;
}

long vpVideoReader::extractImageIndex(const std::string &imageName, const std::string &format)
{
  size_t indexBegin = format.find_last_of('%');
  size_t indexEnd = format.find_first_of('d', indexBegin);
  size_t suffixLength = format.length() - indexEnd - 1;

  // Extracting index
  if (imageName.length() <= suffixLength + indexBegin) {
    return -1;
  }
  size_t indexLength = imageName.length() - suffixLength - indexBegin;
  std::string indexSubstr = imageName.substr(indexBegin, indexLength);
  std::istringstream ss(indexSubstr);
  long index = 0;
  ss >> index;
  if (ss.fail() || index < 0 || !ss.eof()) {
    return -1;
  }

  // Checking that format with inserted index equals imageName
  char nameByFormat[FILENAME_MAX];
  sprintf(nameByFormat, format.c_str(), index);
  if (std::string(nameByFormat) != imageName) {
    return -1;
  }
  return index;
}

bool vpVideoReader::checkImageNameFormat(const std::string &format)
{
  size_t indexBegin = format.find_last_of('%');
  size_t indexEnd = format.find_first_of('d', indexBegin);
  if (indexBegin == std::string::npos || indexEnd == std::string::npos) {
    return false;
  }
  for (size_t i = indexBegin + 1; i < indexEnd; i++) {
    if (!std::isdigit(format[i])) {
      return false;
    }
  }
  return true;
}