// Windows-specific mode mapping header.mode[0] = '0'; header.mode[1] = info.isReadOnly ? '4' : '6'; strcpy(header.magic, "ustar");
Abstract The tar (tape archive) utility is a cornerstone of file archiving in Unix-like systems, but native Windows environments lack a built-in equivalent. This paper presents the design and implementation of a Windows-native tar utility that emulates POSIX behavior while adhering to Windows file system semantics, path conventions, and security models. Key contributions include handling of alternate data streams, long path names, permission mapping between POSIX and NTFS ACLs, and integration with PowerShell and CMD. Performance benchmarks and compatibility tests against GNU tar 1.34 are provided. 1. Introduction The tar format (POSIX.1-2001) remains the dominant archiving standard for software distribution, system backups, and container images (e.g., Docker). However, Windows users traditionally rely on third-party ports (e.g., GNUWin32, Cygwin) or proprietary tools (WinRAR, 7-Zip). These solutions introduce dependencies or incomplete POSIX emulation.
else if (hdr.typeflag == '2') // symlink std::wstring target = Utf8ToWide(hdr.linkname); CreateSymbolicLinkW(fullPath.c_str(), target.c_str(), IsDirectory(target) ? SYMBOLIC_LINK_FLAG_DIRECTORY : 0); tar utility for windows
bool IsSparseFile(HANDLE h) DWORD bytes; FILE_ATTRIBUTE_TAG_INFO tag = 0; DeviceIoControl(h, FSCTL_GET_NTFS_FILE_RECORD, ...); return (tag.FileAttributes & FILE_ATTRIBUTE_SPARSE_FILE) != 0;
Simplified approach: Store mode in pax extended header, apply best effort on Windows (ignore group/other bits, map owner read/write to deny/allow ACL entries). Detect sparse files on Windows via FSCTL_QUERY_ALLOCATED_RANGES : // Windows-specific mode mapping header
void TarWriter::addADS(const std::wstring& path) std::wstring streamPath = path + L":Zone.Identifier"; HANDLE h = CreateFileW(streamPath.c_str(), GENERIC_READ, ...); if (h != INVALID_HANDLE_VALUE) // Store as separate entry with name "path:Zone.Identifier" addFile(streamPath, ToUtf8(path) + ":Zone.Identifier");
// ... other types Use streaming architecture to avoid loading entire archive into memory: Introduction The tar format (POSIX
// Write file content if (!info.isDirectory) HANDLE h = CreateFileW(path.c_str(), GENERIC_READ, ...); WriteFileContent(h, info.size);