backuphelper.cpp

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#include "./backuphelper.h"
#include "./diagnostics.h"
#include "./mediafileinfo.h"
 
#include <c++utilities/conversion/stringbuilder.h>
#include <c++utilities/conversion/stringconversion.h>
 
#ifdef PLATFORM_WINDOWS
#include <windows.h>
#else
#include <sys/stat.h>
#endif
 
#include <cstdio>
#include <fstream>
#include <stdexcept>
#include <string>
 
using namespace std;
using namespace CppUtilities;
 
namespace TagParser {
 
namespace BackupHelper {
 
void restoreOriginalFileFromBackupFile(
    const std::string &originalPath, const std::string &backupPath, NativeFileStream &originalStream, NativeFileStream &backupStream)
{
    // ensure the original stream is closed
    if (originalStream.is_open()) {
        originalStream.close();
    }
    // check whether backup file actually exists and close the backup stream afterwards
    const auto backupPathForOpen = BasicFileInfo::pathForOpen(backupPath);
    backupStream.exceptions(ios_base::goodbit);
    backupStream.close();
    backupStream.clear();
    backupStream.open(backupPathForOpen.data(), ios_base::in | ios_base::binary);
    if (backupStream.is_open()) {
        backupStream.close();
    } else {
        throw std::ios_base::failure("Backup/temporary file has not been created.");
    }
    // remove original file and restore backup
    const auto originalPathForOpen = BasicFileInfo::pathForOpen(originalPath);
    std::remove(originalPathForOpen.data());
    if (std::rename(backupPathForOpen.data(), originalPathForOpen.data()) == 0) {
        return;
    }
    // can't rename/move the file (maybe backup dir on another partition) -> make a copy instead
    try {
        // need to open all streams again
        backupStream.exceptions(ios_base::failbit | ios_base::badbit);
        originalStream.exceptions(ios_base::failbit | ios_base::badbit);
        backupStream.open(backupPathForOpen.data(), ios_base::in | ios_base::binary);
        originalStream.open(originalPathForOpen.data(), ios_base::out | ios_base::binary);
        originalStream << backupStream.rdbuf();
        originalStream.flush();
        // TODO: callback for progress updates
    } catch (const std::ios_base::failure &failure) {
        throw std::ios_base::failure("Unable to restore original file from backup file \"" % backupPath % "\" after failure: " + failure.what());
    }
}
 
static bool isRelative(const std::string &path)
{
    return path.empty() || (path.front() != '/' && (path.size() < 2 || path[1] != ':'));
}
 
void createBackupFile(const std::string &backupDir, const std::string &originalPath, std::string &backupPath, NativeFileStream &originalStream,
    NativeFileStream &backupStream)
{
    // determine dirs
    const auto backupDirRelative(isRelative(backupDir));
    const auto originalDir(backupDirRelative ? BasicFileInfo::containingDirectory(originalPath) : string());
 
    // determine the backup path
    for (unsigned int i = 0;; ++i) {
        if (backupDir.empty()) {
            if (i) {
                backupPath = originalPath % '.' % i + ".bak";
            } else {
                backupPath = originalPath + ".bak";
            }
        } else {
            const auto fileName(BasicFileInfo::fileName(originalPath, i));
            if (i) {
                const auto ext(BasicFileInfo::extension(originalPath));
                if (backupDirRelative) {
                    backupPath = originalDir % '/' % backupDir % '/' % fileName % '.' % i + ext;
                } else {
                    backupPath = backupDir % '/' % fileName % '.' % i + ext;
                }
            } else {
                if (backupDirRelative) {
                    backupPath = originalDir % '/' % backupDir % '/' + fileName;
                } else {
                    backupPath = backupDir % '/' + fileName;
                }
            }
        }
 
        // test whether the backup path is still unused; otherwise continue loop
#ifdef PLATFORM_WINDOWS
        if (GetFileAttributes(BasicFileInfo::pathForOpen(backupPath).data()) == INVALID_FILE_ATTRIBUTES) {
#else
        struct stat backupStat;
        if (stat(BasicFileInfo::pathForOpen(backupPath).data(), &backupStat)) {
#endif
            break;
        }
    }
 
    // ensure original file is closed
    if (originalStream.is_open()) {
        originalStream.close();
    }
 
    // rename original file
    if (std::rename(BasicFileInfo::pathForOpen(originalPath).data(), BasicFileInfo::pathForOpen(backupPath).data())) {
        // can't rename/move the file (maybe backup dir on another partition) -> make a copy instead
        try {
            backupStream.exceptions(ios_base::failbit | ios_base::badbit);
            originalStream.exceptions(ios_base::failbit | ios_base::badbit);
            // ensure backupStream is opened as write-only
            if (backupStream.is_open()) {
                backupStream.close();
            }
            backupStream.open(BasicFileInfo::pathForOpen(backupPath).data(), ios_base::out | ios_base::binary);
            // ensure originalStream is opened with read permissions
            originalStream.open(BasicFileInfo::pathForOpen(originalPath).data(), ios_base::in | ios_base::binary);
            // do the actual copying
            backupStream << originalStream.rdbuf();
            backupStream.flush();
            // streams are closed in the next try-block
            // TODO: callback for progress updates
        } catch (const std::ios_base::failure &failure) {
            throw std::ios_base::failure(argsToString("Unable to rename original file before rewriting it: ", failure.what()));
        }
    }
 
    // manage streams
    try {
        // ensure there is no file associated with the originalStream object
        if (originalStream.is_open()) {
            originalStream.close();
        }
        // ensure there is no file associated with the backupStream object
        if (backupStream.is_open()) {
            backupStream.close();
        }
        // open backup stream
        backupStream.exceptions(ios_base::failbit | ios_base::badbit);
        backupStream.open(BasicFileInfo::pathForOpen(backupPath).data(), ios_base::in | ios_base::binary);
    } catch (const std::ios_base::failure &failure) {
        // can't open the new file
        // -> try to re-rename backup file in the error case to restore previous state
        if (std::rename(BasicFileInfo::pathForOpen(backupPath).data(), BasicFileInfo::pathForOpen(originalPath).data())) {
            throw std::ios_base::failure("Unable to restore original file from backup file \"" % backupPath % "\" after failure: " + failure.what());
        } else {
            throw std::ios_base::failure(argsToString("Unable to open backup file: ", failure.what()));
        }
    }
}
 
void handleFailureAfterFileModified(MediaFileInfo &fileInfo, const std::string &backupPath, NativeFileStream &outputStream,
    NativeFileStream &backupStream, Diagnostics &diag, const std::string &context)
{
    // reset the associated container in any case
    if (fileInfo.container()) {
        fileInfo.container()->reset();
    }
 
    // re-throw the current exception
    try {
        throw;
    } catch (const OperationAbortedException &) {
        if (!backupPath.empty()) {
            // a temp/backup file has been created -> restore original file
            diag.emplace_back(DiagLevel::Information, "Rewriting the file to apply changed tag information has been aborted.", context);
            try {
                restoreOriginalFileFromBackupFile(fileInfo.path(), backupPath, outputStream, backupStream);
                diag.emplace_back(DiagLevel::Warning, "The original file has been restored.", context);
            } catch (const std::ios_base::failure &failure) {
                diag.emplace_back(DiagLevel::Critical, argsToString("The original file could not be restored: ", failure.what()), context);
            }
        } else {
            diag.emplace_back(DiagLevel::Information, "Applying new tag information has been aborted.", context);
        }
        throw;
 
    } catch (const Failure &) {
        if (!backupPath.empty()) {
            // a temp/backup file has been created -> restore original file
            diag.emplace_back(DiagLevel::Critical, "Rewriting the file to apply changed tag information failed.", context);
            try {
                restoreOriginalFileFromBackupFile(fileInfo.path(), backupPath, outputStream, backupStream);
                diag.emplace_back(DiagLevel::Warning, "The original file has been restored.", context);
            } catch (const std::ios_base::failure &failure) {
                diag.emplace_back(DiagLevel::Critical, argsToString("The original file could not be restored: ", failure.what()), context);
            }
        } else {
            diag.emplace_back(DiagLevel::Critical, "Applying new tag information failed.", context);
        }
        throw;
 
    } catch (const std::ios_base::failure &) {
        if (!backupPath.empty()) {
            // a temp/backup file has been created -> restore original file
            diag.emplace_back(DiagLevel::Critical, "An IO error occurred when rewriting the file to apply changed tag information.", context);
            try {
                restoreOriginalFileFromBackupFile(fileInfo.path(), backupPath, outputStream, backupStream);
                diag.emplace_back(DiagLevel::Warning, "The original file has been restored.", context);
            } catch (const std::ios_base::failure &failure) {
                diag.emplace_back(DiagLevel::Critical, argsToString("The original file could not be restored: ", failure.what()), context);
            }
        } else {
            diag.emplace_back(DiagLevel::Critical, "An IO error occurred when applying tag information.", context);
        }
        throw;
    }
}
 
} // namespace BackupHelper
 
} // namespace TagParser