SNFUtility/Common/FileBackup.cpp

// FileBackup.cpp
//
// Copyright (C) 2011, ARM Research Labs, LLC.
// See www.armresearch.com for the copyright terms.
//
// This file implements the common functionality for the configuration
// utilities.

#include <cerrno>
#include <cstring>
#include <cstdio>

#include <sstream>
#include <stdexcept>
#include <fstream>

#include "FileBackup.hpp"

//////////////////////////////////////////////////////////////////////////////////////////////////////////
// Configuration. ////////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////////////////////////

const std::string FileBackup::BackupSuffix(".bak");

//////////////////////////////////////////////////////////////////////////////////////////////////////////
// End of configuration. /////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////////////////////////

void
FileBackup::CopyFile(std::string From, std::string To) {

    std::ifstream Input;

    Input.open(From.c_str());
    if (!Input) {
	std::string Temp;

	Temp = "Error opening the file " + From;
	Temp += " to read from:  ";
	Temp += strerror(errno);
	throw std::runtime_error(Temp);
    }

    std::ofstream Output;

    Output.open(To.c_str(), std::ios::trunc);
    if (!Output) {
	std::string Temp;

	Temp = "Error opening the file " + To;
	Temp += " to copy to:  ";
	Temp += strerror(errno);
	throw std::runtime_error(Temp);
    }

    if (!Input.eof()) {                                                         // Copy if there are characters.
                                                                                // Copying an empty file causes
        Output << Input.rdbuf();                                                // failbit to be set.

    }

    if (Output.bad() || Output.fail()) {
	std::string Temp;

	Temp = "Error copying " + From;
	Temp += " to " + To;
	Temp += ":  ";
	Temp += strerror(errno);
	throw std::runtime_error(Temp);
    }

    Input.close();
    if (!Input) {
	std::string Temp;

	Temp = "Error closing the file " + From;
	Temp += ":  ";
	Temp += strerror(errno);
	throw std::runtime_error(Temp);
    }

    Output.close();
    if (!Output) {
	std::string Temp;

	Temp = "Error closing the file " + To;
	Temp += ":  ";
	Temp += strerror(errno);
	throw std::runtime_error(Temp);
    }

}

std::string
FileBackup::GetBackupFileName(std::string File) {

    return File + BackupSuffix;

}

bool
FileBackup::FileExists(std::string File) {

    bool Exists;
    std::ifstream Input;

    errno = 0;
    Input.open(File.c_str());

    if (ENOENT == errno) {

	Exists = false;

    } else {

	Exists = true;

    }

    Input.close();

    return Exists;

}

void
FileBackup::CreateBackupFile(std::string File) {

    bool ThisFileExists = FileExists(File);

    if (ThisFileExists) {                                                       // Back up if the file exists.

	try {

	    CopyFile(File, GetBackupFileName(File));

	} catch (std::exception &e) {
	    std::string Temp;

	    Temp = "Error making a backup of " + File;
	    Temp += ":  ";
	    Temp += e.what();
	    throw std::runtime_error(Temp);

	}

    }

    OriginalFileExists[File] = ThisFileExists;

}

void
FileBackup::RemoveAllBackupFiles() {

    bool ErrorOccurred = false;
    std::ostringstream ErrorMessage;

    for (FilenameContainer::iterator iFile = OriginalFileExists.begin();
	 iFile != OriginalFileExists.end();
	 iFile++) {
	std::string BackupFileName;

        if (iFile->second) {                                                    // Original file existed?

	    BackupFileName = GetBackupFileName(iFile->first);

            if (0 != remove(BackupFileName.c_str())) {                          // Delete the backup file.

		ErrorMessage << "Unable to remove backup file " << BackupFileName
			     << ":  " << strerror(errno) << "\n";

		ErrorOccurred = true;

	    }

	}

    }

    if (ErrorOccurred) {

	throw std::runtime_error(ErrorMessage.str());

    }

}

void
FileBackup::RestoreAllFilesFromBackup() {

    bool ErrorOccurred = false;
    std::ostringstream ErrorMessage;

    for (FilenameContainer::iterator iFile = OriginalFileExists.begin();
	 iFile != OriginalFileExists.end();
	 iFile++) {
	std::string BackupFileName;

        if (iFile->second) {                                                    // Original file existed?

            try {                                                               // Yes.

		BackupFileName = GetBackupFileName(iFile->first);

		CopyFile(BackupFileName, iFile->first);

	    } catch (std::exception &e) {

		ErrorMessage << "Error restoring " << iFile->first << " from backup "
			     << BackupFileName << ":  " << e.what() << " \n";

		ErrorOccurred = true;

	    }

        } else {                                                                // No.

	    if (FileExists(iFile->first)) {

		if (0 != remove(iFile->first.c_str())) {

		    ErrorMessage << "Unable to remove backup file " << BackupFileName
				 << ":  " << strerror(errno) << "\n";

		    ErrorOccurred = true;

		}

	    }

	}

    }

    if (ErrorOccurred) {

	throw std::runtime_error(ErrorMessage.str());

    }

}