thodg/libgit2/src/util/win32/path_w32.c

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• Hash : c3b7ace9
  Author :
  Date : 2021-11-14T16:43:53
  

  refactor: make util an object library Instead of simply including the utility files directly, make them a cmake object library for easy reusability between other projects within libgit2. Now the top-level `src` is responsible for platform selection, while the next-level `libgit2` and `util` configurations are responsible for identifying what objects they include.

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• src/util/win32/path_w32.c

• /*
   * Copyright (C) the libgit2 contributors. All rights reserved.
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  
  #include "path_w32.h"
  
  #include "fs_path.h"
  #include "utf-conv.h"
  #include "posix.h"
  #include "reparse.h"
  #include "dir.h"
  
  #define PATH__NT_NAMESPACE     L"\\\\?\\"
  #define PATH__NT_NAMESPACE_LEN 4
  
  #define PATH__ABSOLUTE_LEN     3
  
  #define path__is_nt_namespace(p) \
  	(((p)[0] == '\\' && (p)[1] == '\\' && (p)[2] == '?' && (p)[3] == '\\') || \
  	 ((p)[0] == '/' && (p)[1] == '/' && (p)[2] == '?' && (p)[3] == '/'))
  
  #define path__is_unc(p) \
  	(((p)[0] == '\\' && (p)[1] == '\\') || ((p)[0] == '/' && (p)[1] == '/'))
  
  #define path__startswith_slash(p) \
  	((p)[0] == '\\' || (p)[0] == '/')
  
  GIT_INLINE(int) path__cwd(wchar_t *path, int size)
  {
  	int len;
  
  	if ((len = GetCurrentDirectoryW(size, path)) == 0) {
  		errno = GetLastError() == ERROR_ACCESS_DENIED ? EACCES : ENOENT;
  		return -1;
  	} else if (len > size) {
  		errno = ENAMETOOLONG;
  		return -1;
  	}
  
  	/* The Win32 APIs may return "\\?\" once you've used it first.
  	 * But it may not.  What a gloriously predictable API!
  	 */
  	if (wcsncmp(path, PATH__NT_NAMESPACE, PATH__NT_NAMESPACE_LEN))
  		return len;
  
  	len -= PATH__NT_NAMESPACE_LEN;
  
  	memmove(path, path + PATH__NT_NAMESPACE_LEN, sizeof(wchar_t) * len);
  	return len;
  }
  
  static wchar_t *path__skip_server(wchar_t *path)
  {
  	wchar_t *c;
  
  	for (c = path; *c; c++) {
  		if (git_fs_path_is_dirsep(*c))
  			return c + 1;
  	}
  
  	return c;
  }
  
  static wchar_t *path__skip_prefix(wchar_t *path)
  {
  	if (path__is_nt_namespace(path)) {
  		path += PATH__NT_NAMESPACE_LEN;
  
  		if (wcsncmp(path, L"UNC\\", 4) == 0)
  			path = path__skip_server(path + 4);
  		else if (git_fs_path_is_absolute(path))
  			path += PATH__ABSOLUTE_LEN;
  	} else if (git_fs_path_is_absolute(path)) {
  		path += PATH__ABSOLUTE_LEN;
  	} else if (path__is_unc(path)) {
  		path = path__skip_server(path + 2);
  	}
  
  	return path;
  }
  
  int git_win32_path_canonicalize(git_win32_path path)
  {
  	wchar_t *base, *from, *to, *next;
  	size_t len;
  
  	base = to = path__skip_prefix(path);
  
  	/* Unposixify if the prefix */
  	for (from = path; from < to; from++) {
  		if (*from == L'/')
  			*from = L'\\';
  	}
  
  	while (*from) {
  		for (next = from; *next; ++next) {
  			if (*next == L'/') {
  				*next = L'\\';
  				break;
  			}
  
  			if (*next == L'\\')
  				break;
  		}
  
  		len = next - from;
  
  		if (len == 1 && from[0] == L'.')
  			/* do nothing with singleton dot */;
  
  		else if (len == 2 && from[0] == L'.' && from[1] == L'.') {
  			if (to == base) {
  				/* no more path segments to strip, eat the "../" */
  				if (*next == L'\\')
  					len++;
  
  				base = to;
  			} else {
  				/* back up a path segment */
  				while (to > base && to[-1] == L'\\') to--;
  				while (to > base && to[-1] != L'\\') to--;
  			}
  		} else {
  			if (*next == L'\\' && *from != L'\\')
  				len++;
  
  			if (to != from)
  				memmove(to, from, sizeof(wchar_t) * len);
  
  			to += len;
  		}
  
  		from += len;
  
  		while (*from == L'\\') from++;
  	}
  
  	/* Strip trailing backslashes */
  	while (to > base && to[-1] == L'\\') to--;
  
  	*to = L'\0';
  
  	if ((to - path) > INT_MAX) {
  		SetLastError(ERROR_FILENAME_EXCED_RANGE);
  		return -1;
  	}
  
  	return (int)(to - path);
  }
  
  static int git_win32_path_join(
  	git_win32_path dest,
  	const wchar_t *one,
  	size_t one_len,
  	const wchar_t *two,
  	size_t two_len)
  {
  	size_t backslash = 0;
  
  	if (one_len && two_len && one[one_len - 1] != L'\\')
  		backslash = 1;
  
  	if (one_len + two_len + backslash > MAX_PATH) {
  		git_error_set(GIT_ERROR_INVALID, "path too long");
  		return -1;
  	}
  
  	memmove(dest, one, one_len * sizeof(wchar_t));
  
  	if (backslash)
  		dest[one_len] = L'\\';
  
  	memcpy(dest + one_len + backslash, two, two_len * sizeof(wchar_t));
  	dest[one_len + backslash + two_len] = L'\0';
  
  	return 0;
  }
  
  struct win32_path_iter {
  	wchar_t *env;
  	const wchar_t *current_dir;
  };
  
  static int win32_path_iter_init(struct win32_path_iter *iter)
  {
  	DWORD len = GetEnvironmentVariableW(L"PATH", NULL, 0);
  
  	if (!len && GetLastError() == ERROR_ENVVAR_NOT_FOUND) {
  		iter->env = NULL;
  		iter->current_dir = NULL;
  		return 0;
  	} else if (!len) {
  		git_error_set(GIT_ERROR_OS, "could not load PATH");
  		return -1;
  	}
  
  	iter->env = git__malloc(len * sizeof(wchar_t));
  	GIT_ERROR_CHECK_ALLOC(iter->env);
  
  	len = GetEnvironmentVariableW(L"PATH", iter->env, len);
  
  	if (len == 0) {
  		git_error_set(GIT_ERROR_OS, "could not load PATH");
  		return -1;
  	}
  
  	iter->current_dir = iter->env;
  	return 0;
  }
  
  static int win32_path_iter_next(
  	const wchar_t **out,
  	size_t *out_len,
  	struct win32_path_iter *iter)
  {
  	const wchar_t *start;
  	wchar_t term;
  	size_t len = 0;
  
  	if (!iter->current_dir || !*iter->current_dir)
  		return GIT_ITEROVER;
  
  	term = (*iter->current_dir == L'"') ? *iter->current_dir++ : L';';
  	start = iter->current_dir;
  
  	while (*iter->current_dir && *iter->current_dir != term) {
  		iter->current_dir++;
  		len++;
  	}
  
  	*out = start;
  	*out_len = len;
  
  	if (term == L'"' && *iter->current_dir)
  		iter->current_dir++;
  
  	while (*iter->current_dir == L';')
  		iter->current_dir++;
  
  	return 0;
  }
  
  static void win32_path_iter_dispose(struct win32_path_iter *iter)
  {
  	if (!iter)
  		return;
  
  	git__free(iter->env);
  	iter->env = NULL;
  	iter->current_dir = NULL;
  }
  
  int git_win32_path_find_executable(git_win32_path fullpath, wchar_t *exe)
  {
  	struct win32_path_iter path_iter;
  	const wchar_t *dir;
  	size_t dir_len, exe_len = wcslen(exe);
  	bool found = false;
  
  	if (win32_path_iter_init(&path_iter) < 0)
  		return -1;
  
  	while (win32_path_iter_next(&dir, &dir_len, &path_iter) != GIT_ITEROVER) {
  		if (git_win32_path_join(fullpath, dir, dir_len, exe, exe_len) < 0)
  			continue;
  
  		if (_waccess(fullpath, 0) == 0) {
  			found = true;
  			break;
  		}
  	}
  
  	win32_path_iter_dispose(&path_iter);
  
  	if (found)
  		return 0;
  
  	fullpath[0] = L'\0';
  	return GIT_ENOTFOUND;
  }
  
  static int win32_path_cwd(wchar_t *out, size_t len)
  {
  	int cwd_len;
  
  	if (len > INT_MAX) {
  		errno = ENAMETOOLONG;
  		return -1;
  	}
  
  	if ((cwd_len = path__cwd(out, (int)len)) < 0)
  		return -1;
  
  	/* UNC paths */
  	if (wcsncmp(L"\\\\", out, 2) == 0) {
  		/* Our buffer must be at least 5 characters larger than the
  		 * current working directory:  we swallow one of the leading
  		 * '\'s, but we we add a 'UNC' specifier to the path, plus
  		 * a trailing directory separator, plus a NUL.
  		 */
  		if (cwd_len > GIT_WIN_PATH_MAX - 4) {
  			errno = ENAMETOOLONG;
  			return -1;
  		}
  
  		memmove(out+2, out, sizeof(wchar_t) * cwd_len);
  		out[0] = L'U';
  		out[1] = L'N';
  		out[2] = L'C';
  
  		cwd_len += 2;
  	}
  
  	/* Our buffer must be at least 2 characters larger than the current
  	 * working directory.  (One character for the directory separator,
  	 * one for the null.
  	 */
  	else if (cwd_len > GIT_WIN_PATH_MAX - 2) {
  		errno = ENAMETOOLONG;
  		return -1;
  	}
  
  	return cwd_len;
  }
  
  int git_win32_path_from_utf8(git_win32_path out, const char *src)
  {
  	wchar_t *dest = out;
  
  	/* All win32 paths are in NT-prefixed format, beginning with "\\?\". */
  	memcpy(dest, PATH__NT_NAMESPACE, sizeof(wchar_t) * PATH__NT_NAMESPACE_LEN);
  	dest += PATH__NT_NAMESPACE_LEN;
  
  	/* See if this is an absolute path (beginning with a drive letter) */
  	if (git_fs_path_is_absolute(src)) {
  		if (git__utf8_to_16(dest, GIT_WIN_PATH_MAX, src) < 0)
  			goto on_error;
  	}
  	/* File-prefixed NT-style paths beginning with \\?\ */
  	else if (path__is_nt_namespace(src)) {
  		/* Skip the NT prefix, the destination already contains it */
  		if (git__utf8_to_16(dest, GIT_WIN_PATH_MAX, src + PATH__NT_NAMESPACE_LEN) < 0)
  			goto on_error;
  	}
  	/* UNC paths */
  	else if (path__is_unc(src)) {
  		memcpy(dest, L"UNC\\", sizeof(wchar_t) * 4);
  		dest += 4;
  
  		/* Skip the leading "\\" */
  		if (git__utf8_to_16(dest, GIT_WIN_PATH_MAX - 2, src + 2) < 0)
  			goto on_error;
  	}
  	/* Absolute paths omitting the drive letter */
  	else if (path__startswith_slash(src)) {
  		if (path__cwd(dest, GIT_WIN_PATH_MAX) < 0)
  			goto on_error;
  
  		if (!git_fs_path_is_absolute(dest)) {
  			errno = ENOENT;
  			goto on_error;
  		}
  
  		/* Skip the drive letter specification ("C:") */
  		if (git__utf8_to_16(dest + 2, GIT_WIN_PATH_MAX - 2, src) < 0)
  			goto on_error;
  	}
  	/* Relative paths */
  	else {
  		int cwd_len;
  
  		if ((cwd_len = win32_path_cwd(dest, GIT_WIN_PATH_MAX)) < 0)
  			goto on_error;
  
  		dest[cwd_len++] = L'\\';
  
  		if (git__utf8_to_16(dest + cwd_len, GIT_WIN_PATH_MAX - cwd_len, src) < 0)
  			goto on_error;
  	}
  
  	return git_win32_path_canonicalize(out);
  
  on_error:
  	/* set windows error code so we can use its error message */
  	if (errno == ENAMETOOLONG)
  		SetLastError(ERROR_FILENAME_EXCED_RANGE);
  
  	return -1;
  }
  
  int git_win32_path_relative_from_utf8(git_win32_path out, const char *src)
  {
  	wchar_t *dest = out, *p;
  	int len;
  
  	/* Handle absolute paths */
  	if (git_fs_path_is_absolute(src) ||
  	    path__is_nt_namespace(src) ||
  	    path__is_unc(src) ||
  	    path__startswith_slash(src)) {
  		return git_win32_path_from_utf8(out, src);
  	}
  
  	if ((len = git__utf8_to_16(dest, GIT_WIN_PATH_MAX, src)) < 0)
  		return -1;
  
  	for (p = dest; p < (dest + len); p++) {
  		if (*p == L'/')
  			*p = L'\\';
  	}
  
  	return len;
  }
  
  int git_win32_path_to_utf8(git_win32_utf8_path dest, const wchar_t *src)
  {
  	char *out = dest;
  	int len;
  
  	/* Strip NT namespacing "\\?\" */
  	if (path__is_nt_namespace(src)) {
  		src += 4;
  
  		/* "\\?\UNC\server\share" -> "\\server\share" */
  		if (wcsncmp(src, L"UNC\\", 4) == 0) {
  			src += 4;
  
  			memcpy(dest, "\\\\", 2);
  			out = dest + 2;
  		}
  	}
  
  	if ((len = git__utf16_to_8(out, GIT_WIN_PATH_UTF8, src)) < 0)
  		return len;
  
  	git_fs_path_mkposix(dest);
  
  	return len;
  }
  
  char *git_win32_path_8dot3_name(const char *path)
  {
  	git_win32_path longpath, shortpath;
  	wchar_t *start;
  	char *shortname;
  	int len, namelen = 1;
  
  	if (git_win32_path_from_utf8(longpath, path) < 0)
  		return NULL;
  
  	len = GetShortPathNameW(longpath, shortpath, GIT_WIN_PATH_UTF16);
  
  	while (len && shortpath[len-1] == L'\\')
  		shortpath[--len] = L'\0';
  
  	if (len == 0 || len >= GIT_WIN_PATH_UTF16)
  		return NULL;
  
  	for (start = shortpath + (len - 1);
  		start > shortpath && *(start-1) != '/' && *(start-1) != '\\';
  		start--)
  		namelen++;
  
  	/* We may not have actually been given a short name.  But if we have,
  	 * it will be in the ASCII byte range, so we don't need to worry about
  	 * multi-byte sequences and can allocate naively.
  	 */
  	if (namelen > 12 || (shortname = git__malloc(namelen + 1)) == NULL)
  		return NULL;
  
  	if ((len = git__utf16_to_8(shortname, namelen + 1, start)) < 0)
  		return NULL;
  
  	return shortname;
  }
  
  static bool path_is_volume(wchar_t *target, size_t target_len)
  {
  	return (target_len && wcsncmp(target, L"\\??\\Volume{", 11) == 0);
  }
  
  /* On success, returns the length, in characters, of the path stored in dest.
   * On failure, returns a negative value. */
  int git_win32_path_readlink_w(git_win32_path dest, const git_win32_path path)
  {
  	BYTE buf[MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
  	GIT_REPARSE_DATA_BUFFER *reparse_buf = (GIT_REPARSE_DATA_BUFFER *)buf;
  	HANDLE handle = NULL;
  	DWORD ioctl_ret;
  	wchar_t *target;
  	size_t target_len;
  
  	int error = -1;
  
  	handle = CreateFileW(path, GENERIC_READ,
  		FILE_SHARE_READ | FILE_SHARE_DELETE, NULL, OPEN_EXISTING,
  		FILE_FLAG_OPEN_REPARSE_POINT | FILE_FLAG_BACKUP_SEMANTICS, NULL);
  
  	if (handle == INVALID_HANDLE_VALUE) {
  		errno = ENOENT;
  		return -1;
  	}
  
  	if (!DeviceIoControl(handle, FSCTL_GET_REPARSE_POINT, NULL, 0,
  		reparse_buf, sizeof(buf), &ioctl_ret, NULL)) {
  		errno = EINVAL;
  		goto on_error;
  	}
  
  	switch (reparse_buf->ReparseTag) {
  	case IO_REPARSE_TAG_SYMLINK:
  		target = reparse_buf->ReparseBuffer.SymbolicLink.PathBuffer +
  			(reparse_buf->ReparseBuffer.SymbolicLink.SubstituteNameOffset / sizeof(WCHAR));
  		target_len = reparse_buf->ReparseBuffer.SymbolicLink.SubstituteNameLength / sizeof(WCHAR);
  	break;
  	case IO_REPARSE_TAG_MOUNT_POINT:
  		target = reparse_buf->ReparseBuffer.MountPoint.PathBuffer +
  			(reparse_buf->ReparseBuffer.MountPoint.SubstituteNameOffset / sizeof(WCHAR));
  		target_len = reparse_buf->ReparseBuffer.MountPoint.SubstituteNameLength / sizeof(WCHAR);
  	break;
  	default:
  		errno = EINVAL;
  		goto on_error;
  	}
  
  	if (path_is_volume(target, target_len)) {
  		/* This path is a reparse point that represents another volume mounted
  		 * at this location, it is not a symbolic link our input was canonical.
  		 */
  		errno = EINVAL;
  		error = -1;
  	} else if (target_len) {
  		/* The path may need to have a namespace prefix removed. */
  		target_len = git_win32_path_remove_namespace(target, target_len);
  
  		/* Need one additional character in the target buffer
  		 * for the terminating NULL. */
  		if (GIT_WIN_PATH_UTF16 > target_len) {
  			wcscpy(dest, target);
  			error = (int)target_len;
  		}
  	}
  
  on_error:
  	CloseHandle(handle);
  	return error;
  }
  
  /**
   * Removes any trailing backslashes from a path, except in the case of a drive
   * letter path (C:\, D:\, etc.). This function cannot fail.
   *
   * @param path The path which should be trimmed.
   * @return The length of the modified string (<= the input length)
   */
  size_t git_win32_path_trim_end(wchar_t *str, size_t len)
  {
  	while (1) {
  		if (!len || str[len - 1] != L'\\')
  			break;
  
  		/*
  		 * Don't trim backslashes from drive letter paths, which
  		 * are 3 characters long and of the form C:\, D:\, etc.
  		 */
  		if (len == 3 && git_win32__isalpha(str[0]) && str[1] == ':')
  			break;
  
  		len--;
  	}
  
  	str[len] = L'\0';
  
  	return len;
  }
  
  /**
   * Removes any of the following namespace prefixes from a path,
   * if found: "\??\", "\\?\", "\\?\UNC\". This function cannot fail.
   *
   * @param path The path which should be converted.
   * @return The length of the modified string (<= the input length)
   */
  size_t git_win32_path_remove_namespace(wchar_t *str, size_t len)
  {
  	static const wchar_t dosdevices_namespace[] = L"\\\?\?\\";
  	static const wchar_t nt_namespace[] = L"\\\\?\\";
  	static const wchar_t unc_namespace_remainder[] = L"UNC\\";
  	static const wchar_t unc_prefix[] = L"\\\\";
  
  	const wchar_t *prefix = NULL, *remainder = NULL;
  	size_t prefix_len = 0, remainder_len = 0;
  
  	/* "\??\" -- DOS Devices prefix */
  	if (len >= CONST_STRLEN(dosdevices_namespace) &&
  		!wcsncmp(str, dosdevices_namespace, CONST_STRLEN(dosdevices_namespace))) {
  		remainder = str + CONST_STRLEN(dosdevices_namespace);
  		remainder_len = len - CONST_STRLEN(dosdevices_namespace);
  	}
  	/* "\\?\" -- NT namespace prefix */
  	else if (len >= CONST_STRLEN(nt_namespace) &&
  		!wcsncmp(str, nt_namespace, CONST_STRLEN(nt_namespace))) {
  		remainder = str + CONST_STRLEN(nt_namespace);
  		remainder_len = len - CONST_STRLEN(nt_namespace);
  	}
  
  	/* "\??\UNC\", "\\?\UNC\" -- UNC prefix */
  	if (remainder_len >= CONST_STRLEN(unc_namespace_remainder) &&
  		!wcsncmp(remainder, unc_namespace_remainder, CONST_STRLEN(unc_namespace_remainder))) {
  
  		/*
  		 * The proper Win32 path for a UNC share has "\\" at beginning of it
  		 * and looks like "\\server\share\<folderStructure>".  So remove the
  		 * UNC namespace and add a prefix of "\\" in its place.
  		 */
  		remainder += CONST_STRLEN(unc_namespace_remainder);
  		remainder_len -= CONST_STRLEN(unc_namespace_remainder);
  
  		prefix = unc_prefix;
  		prefix_len = CONST_STRLEN(unc_prefix);
  	}
  
  	/*
  	 * Sanity check that the new string isn't longer than the old one.
  	 * (This could only happen due to programmer error introducing a
  	 * prefix longer than the namespace it replaces.)
  	 */
  	if (remainder && len >= remainder_len + prefix_len) {
  		if (prefix)
  			memmove(str, prefix, prefix_len * sizeof(wchar_t));
  
  		memmove(str + prefix_len, remainder, remainder_len * sizeof(wchar_t));
  
  		len = remainder_len + prefix_len;
  		str[len] = L'\0';
  	}
  
  	return git_win32_path_trim_end(str, len);
  }
  

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