thodg/libgit2/src/util/fs_path.c

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• Hash : c0b7f88e
  Author :
  Date : 2022-04-11T17:06:55
  

  fs_path: mock ownership checks Provide a mock for file ownership for testability.

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• src/util/fs_path.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 "fs_path.h"
  
  #include "git2_util.h"
  #include "futils.h"
  #include "posix.h"
  #ifdef GIT_WIN32
  #include "win32/posix.h"
  #include "win32/w32_buffer.h"
  #include "win32/w32_util.h"
  #include "win32/version.h"
  #include <aclapi.h>
  #else
  #include <dirent.h>
  #endif
  #include <stdio.h>
  #include <ctype.h>
  
  #define ensure_error_set(code) do { \
  		const git_error *e = git_error_last(); \
  		if (!e || !e->message) \
  			git_error_set(e ? e->klass : GIT_ERROR_CALLBACK, \
  				"filesystem callback returned %d", code); \
  	} while(0)
  
  static int dos_drive_prefix_length(const char *path)
  {
  	int i;
  
  	/*
  	 * Does it start with an ASCII letter (i.e. highest bit not set),
  	 * followed by a colon?
  	 */
  	if (!(0x80 & (unsigned char)*path))
  		return *path && path[1] == ':' ? 2 : 0;
  
  	/*
  	 * While drive letters must be letters of the English alphabet, it is
  	 * possible to assign virtually _any_ Unicode character via `subst` as
  	 * a drive letter to "virtual drives". Even `1`, or `ä`. Or fun stuff
  	 * like this:
  	 *
  	 *	subst ֍: %USERPROFILE%\Desktop
  	 */
  	for (i = 1; i < 4 && (0x80 & (unsigned char)path[i]); i++)
  		; /* skip first UTF-8 character */
  	return path[i] == ':' ? i + 1 : 0;
  }
  
  #ifdef GIT_WIN32
  static bool looks_like_network_computer_name(const char *path, int pos)
  {
  	if (pos < 3)
  		return false;
  
  	if (path[0] != '/' || path[1] != '/')
  		return false;
  
  	while (pos-- > 2) {
  		if (path[pos] == '/')
  			return false;
  	}
  
  	return true;
  }
  #endif
  
  /*
   * Based on the Android implementation, BSD licensed.
   * http://android.git.kernel.org/
   *
   * Copyright (C) 2008 The Android Open Source Project
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * * Redistributions of source code must retain the above copyright
   *   notice, this list of conditions and the following disclaimer.
   * * Redistributions in binary form must reproduce the above copyright
   *   notice, this list of conditions and the following disclaimer in
   *   the documentation and/or other materials provided with the
   *   distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
   * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   */
  int git_fs_path_basename_r(git_str *buffer, const char *path)
  {
  	const char *endp, *startp;
  	int len, result;
  
  	/* Empty or NULL string gets treated as "." */
  	if (path == NULL || *path == '\0') {
  		startp = ".";
  		len = 1;
  		goto Exit;
  	}
  
  	/* Strip trailing slashes */
  	endp = path + strlen(path) - 1;
  	while (endp > path && *endp == '/')
  		endp--;
  
  	/* All slashes becomes "/" */
  	if (endp == path && *endp == '/') {
  		startp = "/";
  		len = 1;
  		goto Exit;
  	}
  
  	/* Find the start of the base */
  	startp = endp;
  	while (startp > path && *(startp - 1) != '/')
  		startp--;
  
  	/* Cast is safe because max path < max int */
  	len = (int)(endp - startp + 1);
  
  Exit:
  	result = len;
  
  	if (buffer != NULL && git_str_set(buffer, startp, len) < 0)
  		return -1;
  
  	return result;
  }
  
  /*
   * Determine if the path is a Windows prefix and, if so, returns
   * its actual length. If it is not a prefix, returns -1.
   */
  static int win32_prefix_length(const char *path, int len)
  {
  #ifndef GIT_WIN32
  	GIT_UNUSED(path);
  	GIT_UNUSED(len);
  #else
  	/*
  	 * Mimic unix behavior where '/.git' returns '/': 'C:/.git'
  	 * will return 'C:/' here
  	 */
  	if (dos_drive_prefix_length(path) == len)
  		return len;
  
  	/*
  	 * Similarly checks if we're dealing with a network computer name
  	 * '//computername/.git' will return '//computername/'
  	 */
  	if (looks_like_network_computer_name(path, len))
  		return len;
  #endif
  
  	return -1;
  }
  
  /*
   * Based on the Android implementation, BSD licensed.
   * Check http://android.git.kernel.org/
   */
  int git_fs_path_dirname_r(git_str *buffer, const char *path)
  {
  	const char *endp;
  	int is_prefix = 0, len;
  
  	/* Empty or NULL string gets treated as "." */
  	if (path == NULL || *path == '\0') {
  		path = ".";
  		len = 1;
  		goto Exit;
  	}
  
  	/* Strip trailing slashes */
  	endp = path + strlen(path) - 1;
  	while (endp > path && *endp == '/')
  		endp--;
  
  	if (endp - path + 1 > INT_MAX) {
  		git_error_set(GIT_ERROR_INVALID, "path too long");
  		return -1;
  	}
  
  	if ((len = win32_prefix_length(path, (int)(endp - path + 1))) > 0) {
  		is_prefix = 1;
  		goto Exit;
  	}
  
  	/* Find the start of the dir */
  	while (endp > path && *endp != '/')
  		endp--;
  
  	/* Either the dir is "/" or there are no slashes */
  	if (endp == path) {
  		path = (*endp == '/') ? "/" : ".";
  		len = 1;
  		goto Exit;
  	}
  
  	do {
  		endp--;
  	} while (endp > path && *endp == '/');
  
  	if (endp - path + 1 > INT_MAX) {
  		git_error_set(GIT_ERROR_INVALID, "path too long");
  		return -1;
  	}
  
  	if ((len = win32_prefix_length(path, (int)(endp - path + 1))) > 0) {
  		is_prefix = 1;
  		goto Exit;
  	}
  
  	/* Cast is safe because max path < max int */
  	len = (int)(endp - path + 1);
  
  Exit:
  	if (buffer) {
  		if (git_str_set(buffer, path, len) < 0)
  			return -1;
  		if (is_prefix && git_str_putc(buffer, '/') < 0)
  			return -1;
  	}
  
  	return len;
  }
  
  
  char *git_fs_path_dirname(const char *path)
  {
  	git_str buf = GIT_STR_INIT;
  	char *dirname;
  
  	git_fs_path_dirname_r(&buf, path);
  	dirname = git_str_detach(&buf);
  	git_str_dispose(&buf); /* avoid memleak if error occurs */
  
  	return dirname;
  }
  
  char *git_fs_path_basename(const char *path)
  {
  	git_str buf = GIT_STR_INIT;
  	char *basename;
  
  	git_fs_path_basename_r(&buf, path);
  	basename = git_str_detach(&buf);
  	git_str_dispose(&buf); /* avoid memleak if error occurs */
  
  	return basename;
  }
  
  size_t git_fs_path_basename_offset(git_str *buffer)
  {
  	ssize_t slash;
  
  	if (!buffer || buffer->size <= 0)
  		return 0;
  
  	slash = git_str_rfind_next(buffer, '/');
  
  	if (slash >= 0 && buffer->ptr[slash] == '/')
  		return (size_t)(slash + 1);
  
  	return 0;
  }
  
  int git_fs_path_root(const char *path)
  {
  	int offset = 0, prefix_len;
  
  	/* Does the root of the path look like a windows drive ? */
  	if ((prefix_len = dos_drive_prefix_length(path)))
  		offset += prefix_len;
  
  #ifdef GIT_WIN32
  	/* Are we dealing with a windows network path? */
  	else if ((path[0] == '/' && path[1] == '/' && path[2] != '/') ||
  		(path[0] == '\\' && path[1] == '\\' && path[2] != '\\'))
  	{
  		offset += 2;
  
  		/* Skip the computer name segment */
  		while (path[offset] && path[offset] != '/' && path[offset] != '\\')
  			offset++;
  	}
  
  	if (path[offset] == '\\')
  		return offset;
  #endif
  
  	if (path[offset] == '/')
  		return offset;
  
  	return -1;	/* Not a real error - signals that path is not rooted */
  }
  
  static void path_trim_slashes(git_str *path)
  {
  	int ceiling = git_fs_path_root(path->ptr) + 1;
  
  	if (ceiling < 0)
  		return;
  
  	while (path->size > (size_t)ceiling) {
  		if (path->ptr[path->size-1] != '/')
  			break;
  
  		path->ptr[path->size-1] = '\0';
  		path->size--;
  	}
  }
  
  int git_fs_path_join_unrooted(
  	git_str *path_out, const char *path, const char *base, ssize_t *root_at)
  {
  	ssize_t root;
  
  	GIT_ASSERT_ARG(path_out);
  	GIT_ASSERT_ARG(path);
  
  	root = (ssize_t)git_fs_path_root(path);
  
  	if (base != NULL && root < 0) {
  		if (git_str_joinpath(path_out, base, path) < 0)
  			return -1;
  
  		root = (ssize_t)strlen(base);
  	} else {
  		if (git_str_sets(path_out, path) < 0)
  			return -1;
  
  		if (root < 0)
  			root = 0;
  		else if (base)
  			git_fs_path_equal_or_prefixed(base, path, &root);
  	}
  
  	if (root_at)
  		*root_at = root;
  
  	return 0;
  }
  
  void git_fs_path_squash_slashes(git_str *path)
  {
  	char *p, *q;
  
  	if (path->size == 0)
  		return;
  
  	for (p = path->ptr, q = path->ptr; *q; p++, q++) {
  		*p = *q;
  
  		while (*q == '/' && *(q+1) == '/') {
  			path->size--;
  			q++;
  		}
  	}
  
  	*p = '\0';
  }
  
  int git_fs_path_prettify(git_str *path_out, const char *path, const char *base)
  {
  	char buf[GIT_PATH_MAX];
  
  	GIT_ASSERT_ARG(path_out);
  	GIT_ASSERT_ARG(path);
  
  	/* construct path if needed */
  	if (base != NULL && git_fs_path_root(path) < 0) {
  		if (git_str_joinpath(path_out, base, path) < 0)
  			return -1;
  		path = path_out->ptr;
  	}
  
  	if (p_realpath(path, buf) == NULL) {
  		/* git_error_set resets the errno when dealing with a GIT_ERROR_OS kind of error */
  		int error = (errno == ENOENT || errno == ENOTDIR) ? GIT_ENOTFOUND : -1;
  		git_error_set(GIT_ERROR_OS, "failed to resolve path '%s'", path);
  
  		git_str_clear(path_out);
  
  		return error;
  	}
  
  	return git_str_sets(path_out, buf);
  }
  
  int git_fs_path_prettify_dir(git_str *path_out, const char *path, const char *base)
  {
  	int error = git_fs_path_prettify(path_out, path, base);
  	return (error < 0) ? error : git_fs_path_to_dir(path_out);
  }
  
  int git_fs_path_to_dir(git_str *path)
  {
  	if (path->asize > 0 &&
  		git_str_len(path) > 0 &&
  		path->ptr[git_str_len(path) - 1] != '/')
  		git_str_putc(path, '/');
  
  	return git_str_oom(path) ? -1 : 0;
  }
  
  void git_fs_path_string_to_dir(char *path, size_t size)
  {
  	size_t end = strlen(path);
  
  	if (end && path[end - 1] != '/' && end < size) {
  		path[end] = '/';
  		path[end + 1] = '\0';
  	}
  }
  
  int git__percent_decode(git_str *decoded_out, const char *input)
  {
  	int len, hi, lo, i;
  
  	GIT_ASSERT_ARG(decoded_out);
  	GIT_ASSERT_ARG(input);
  
  	len = (int)strlen(input);
  	git_str_clear(decoded_out);
  
  	for(i = 0; i < len; i++)
  	{
  		char c = input[i];
  
  		if (c != '%')
  			goto append;
  
  		if (i >= len - 2)
  			goto append;
  
  		hi = git__fromhex(input[i + 1]);
  		lo = git__fromhex(input[i + 2]);
  
  		if (hi < 0 || lo < 0)
  			goto append;
  
  		c = (char)(hi << 4 | lo);
  		i += 2;
  
  append:
  		if (git_str_putc(decoded_out, c) < 0)
  			return -1;
  	}
  
  	return 0;
  }
  
  static int error_invalid_local_file_uri(const char *uri)
  {
  	git_error_set(GIT_ERROR_CONFIG, "'%s' is not a valid local file URI", uri);
  	return -1;
  }
  
  static int local_file_url_prefixlen(const char *file_url)
  {
  	int len = -1;
  
  	if (git__prefixcmp(file_url, "file://") == 0) {
  		if (file_url[7] == '/')
  			len = 8;
  		else if (git__prefixcmp(file_url + 7, "localhost/") == 0)
  			len = 17;
  	}
  
  	return len;
  }
  
  bool git_fs_path_is_local_file_url(const char *file_url)
  {
  	return (local_file_url_prefixlen(file_url) > 0);
  }
  
  int git_fs_path_fromurl(git_str *local_path_out, const char *file_url)
  {
  	int offset;
  
  	GIT_ASSERT_ARG(local_path_out);
  	GIT_ASSERT_ARG(file_url);
  
  	if ((offset = local_file_url_prefixlen(file_url)) < 0 ||
  		file_url[offset] == '\0' || file_url[offset] == '/')
  		return error_invalid_local_file_uri(file_url);
  
  #ifndef GIT_WIN32
  	offset--;	/* A *nix absolute path starts with a forward slash */
  #endif
  
  	git_str_clear(local_path_out);
  	return git__percent_decode(local_path_out, file_url + offset);
  }
  
  int git_fs_path_walk_up(
  	git_str *path,
  	const char *ceiling,
  	int (*cb)(void *data, const char *),
  	void *data)
  {
  	int error = 0;
  	git_str iter;
  	ssize_t stop = 0, scan;
  	char oldc = '\0';
  
  	GIT_ASSERT_ARG(path);
  	GIT_ASSERT_ARG(cb);
  
  	if (ceiling != NULL) {
  		if (git__prefixcmp(path->ptr, ceiling) == 0)
  			stop = (ssize_t)strlen(ceiling);
  		else
  			stop = git_str_len(path);
  	}
  	scan = git_str_len(path);
  
  	/* empty path: yield only once */
  	if (!scan) {
  		error = cb(data, "");
  		if (error)
  			ensure_error_set(error);
  		return error;
  	}
  
  	iter.ptr = path->ptr;
  	iter.size = git_str_len(path);
  	iter.asize = path->asize;
  
  	while (scan >= stop) {
  		error = cb(data, iter.ptr);
  		iter.ptr[scan] = oldc;
  
  		if (error) {
  			ensure_error_set(error);
  			break;
  		}
  
  		scan = git_str_rfind_next(&iter, '/');
  		if (scan >= 0) {
  			scan++;
  			oldc = iter.ptr[scan];
  			iter.size = scan;
  			iter.ptr[scan] = '\0';
  		}
  	}
  
  	if (scan >= 0)
  		iter.ptr[scan] = oldc;
  
  	/* relative path: yield for the last component */
  	if (!error && stop == 0 && iter.ptr[0] != '/') {
  		error = cb(data, "");
  		if (error)
  			ensure_error_set(error);
  	}
  
  	return error;
  }
  
  bool git_fs_path_exists(const char *path)
  {
  	GIT_ASSERT_ARG_WITH_RETVAL(path, false);
  	return p_access(path, F_OK) == 0;
  }
  
  bool git_fs_path_isdir(const char *path)
  {
  	struct stat st;
  	if (p_stat(path, &st) < 0)
  		return false;
  
  	return S_ISDIR(st.st_mode) != 0;
  }
  
  bool git_fs_path_isfile(const char *path)
  {
  	struct stat st;
  
  	GIT_ASSERT_ARG_WITH_RETVAL(path, false);
  	if (p_stat(path, &st) < 0)
  		return false;
  
  	return S_ISREG(st.st_mode) != 0;
  }
  
  bool git_fs_path_islink(const char *path)
  {
  	struct stat st;
  
  	GIT_ASSERT_ARG_WITH_RETVAL(path, false);
  	if (p_lstat(path, &st) < 0)
  		return false;
  
  	return S_ISLNK(st.st_mode) != 0;
  }
  
  #ifdef GIT_WIN32
  
  bool git_fs_path_is_empty_dir(const char *path)
  {
  	git_win32_path filter_w;
  	bool empty = false;
  
  	if (git_win32__findfirstfile_filter(filter_w, path)) {
  		WIN32_FIND_DATAW findData;
  		HANDLE hFind = FindFirstFileW(filter_w, &findData);
  
  		/* FindFirstFile will fail if there are no children to the given
  		 * path, which can happen if the given path is a file (and obviously
  		 * has no children) or if the given path is an empty mount point.
  		 * (Most directories have at least directory entries '.' and '..',
  		 * but ridiculously another volume mounted in another drive letter's
  		 * path space do not, and thus have nothing to enumerate.)  If
  		 * FindFirstFile fails, check if this is a directory-like thing
  		 * (a mount point).
  		 */
  		if (hFind == INVALID_HANDLE_VALUE)
  			return git_fs_path_isdir(path);
  
  		/* If the find handle was created successfully, then it's a directory */
  		empty = true;
  
  		do {
  			/* Allow the enumeration to return . and .. and still be considered
  			 * empty. In the special case of drive roots (i.e. C:\) where . and
  			 * .. do not occur, we can still consider the path to be an empty
  			 * directory if there's nothing there. */
  			if (!git_fs_path_is_dot_or_dotdotW(findData.cFileName)) {
  				empty = false;
  				break;
  			}
  		} while (FindNextFileW(hFind, &findData));
  
  		FindClose(hFind);
  	}
  
  	return empty;
  }
  
  #else
  
  static int path_found_entry(void *payload, git_str *path)
  {
  	GIT_UNUSED(payload);
  	return !git_fs_path_is_dot_or_dotdot(path->ptr);
  }
  
  bool git_fs_path_is_empty_dir(const char *path)
  {
  	int error;
  	git_str dir = GIT_STR_INIT;
  
  	if (!git_fs_path_isdir(path))
  		return false;
  
  	if ((error = git_str_sets(&dir, path)) != 0)
  		git_error_clear();
  	else
  		error = git_fs_path_direach(&dir, 0, path_found_entry, NULL);
  
  	git_str_dispose(&dir);
  
  	return !error;
  }
  
  #endif
  
  int git_fs_path_set_error(int errno_value, const char *path, const char *action)
  {
  	switch (errno_value) {
  	case ENOENT:
  	case ENOTDIR:
  		git_error_set(GIT_ERROR_OS, "could not find '%s' to %s", path, action);
  		return GIT_ENOTFOUND;
  
  	case EINVAL:
  	case ENAMETOOLONG:
  		git_error_set(GIT_ERROR_OS, "invalid path for filesystem '%s'", path);
  		return GIT_EINVALIDSPEC;
  
  	case EEXIST:
  		git_error_set(GIT_ERROR_OS, "failed %s - '%s' already exists", action, path);
  		return GIT_EEXISTS;
  
  	case EACCES:
  		git_error_set(GIT_ERROR_OS, "failed %s - '%s' is locked", action, path);
  		return GIT_ELOCKED;
  
  	default:
  		git_error_set(GIT_ERROR_OS, "could not %s '%s'", action, path);
  		return -1;
  	}
  }
  
  int git_fs_path_lstat(const char *path, struct stat *st)
  {
  	if (p_lstat(path, st) == 0)
  		return 0;
  
  	return git_fs_path_set_error(errno, path, "stat");
  }
  
  static bool _check_dir_contents(
  	git_str *dir,
  	const char *sub,
  	bool (*predicate)(const char *))
  {
  	bool result;
  	size_t dir_size = git_str_len(dir);
  	size_t sub_size = strlen(sub);
  	size_t alloc_size;
  
  	/* leave base valid even if we could not make space for subdir */
  	if (GIT_ADD_SIZET_OVERFLOW(&alloc_size, dir_size, sub_size) ||
  		GIT_ADD_SIZET_OVERFLOW(&alloc_size, alloc_size, 2) ||
  		git_str_try_grow(dir, alloc_size, false) < 0)
  		return false;
  
  	/* save excursion */
  	if (git_str_joinpath(dir, dir->ptr, sub) < 0)
  		return false;
  
  	result = predicate(dir->ptr);
  
  	/* restore path */
  	git_str_truncate(dir, dir_size);
  	return result;
  }
  
  bool git_fs_path_contains(git_str *dir, const char *item)
  {
  	return _check_dir_contents(dir, item, &git_fs_path_exists);
  }
  
  bool git_fs_path_contains_dir(git_str *base, const char *subdir)
  {
  	return _check_dir_contents(base, subdir, &git_fs_path_isdir);
  }
  
  bool git_fs_path_contains_file(git_str *base, const char *file)
  {
  	return _check_dir_contents(base, file, &git_fs_path_isfile);
  }
  
  int git_fs_path_find_dir(git_str *dir)
  {
  	int error = 0;
  	char buf[GIT_PATH_MAX];
  
  	if (p_realpath(dir->ptr, buf) != NULL)
  		error = git_str_sets(dir, buf);
  
  	/* call dirname if this is not a directory */
  	if (!error) /* && git_fs_path_isdir(dir->ptr) == false) */
  		error = (git_fs_path_dirname_r(dir, dir->ptr) < 0) ? -1 : 0;
  
  	if (!error)
  		error = git_fs_path_to_dir(dir);
  
  	return error;
  }
  
  int git_fs_path_resolve_relative(git_str *path, size_t ceiling)
  {
  	char *base, *to, *from, *next;
  	size_t len;
  
  	GIT_ERROR_CHECK_ALLOC_STR(path);
  
  	if (ceiling > path->size)
  		ceiling = path->size;
  
  	/* recognize drive prefixes, etc. that should not be backed over */
  	if (ceiling == 0)
  		ceiling = git_fs_path_root(path->ptr) + 1;
  
  	/* recognize URL prefixes that should not be backed over */
  	if (ceiling == 0) {
  		for (next = path->ptr; *next && git__isalpha(*next); ++next);
  		if (next[0] == ':' && next[1] == '/' && next[2] == '/')
  			ceiling = (next + 3) - path->ptr;
  	}
  
  	base = to = from = path->ptr + ceiling;
  
  	while (*from) {
  		for (next = from; *next && *next != '/'; ++next);
  
  		len = next - from;
  
  		if (len == 1 && from[0] == '.')
  			/* do nothing with singleton dot */;
  
  		else if (len == 2 && from[0] == '.' && from[1] == '.') {
  			/* error out if trying to up one from a hard base */
  			if (to == base && ceiling != 0) {
  				git_error_set(GIT_ERROR_INVALID,
  					"cannot strip root component off url");
  				return -1;
  			}
  
  			/* no more path segments to strip,
  			 * use '../' as a new base path */
  			if (to == base) {
  				if (*next == '/')
  					len++;
  
  				if (to != from)
  					memmove(to, from, len);
  
  				to += len;
  				/* this is now the base, can't back up from a
  				 * relative prefix */
  				base = to;
  			} else {
  				/* back up a path segment */
  				while (to > base && to[-1] == '/') to--;
  				while (to > base && to[-1] != '/') to--;
  			}
  		} else {
  			if (*next == '/' && *from != '/')
  				len++;
  
  			if (to != from)
  				memmove(to, from, len);
  
  			to += len;
  		}
  
  		from += len;
  
  		while (*from == '/') from++;
  	}
  
  	*to = '\0';
  
  	path->size = to - path->ptr;
  
  	return 0;
  }
  
  int git_fs_path_apply_relative(git_str *target, const char *relpath)
  {
  	return git_str_joinpath(target, git_str_cstr(target), relpath) ||
  	    git_fs_path_resolve_relative(target, 0);
  }
  
  int git_fs_path_cmp(
  	const char *name1, size_t len1, int isdir1,
  	const char *name2, size_t len2, int isdir2,
  	int (*compare)(const char *, const char *, size_t))
  {
  	unsigned char c1, c2;
  	size_t len = len1 < len2 ? len1 : len2;
  	int cmp;
  
  	cmp = compare(name1, name2, len);
  	if (cmp)
  		return cmp;
  
  	c1 = name1[len];
  	c2 = name2[len];
  
  	if (c1 == '\0' && isdir1)
  		c1 = '/';
  
  	if (c2 == '\0' && isdir2)
  		c2 = '/';
  
  	return (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
  }
  
  size_t git_fs_path_common_dirlen(const char *one, const char *two)
  {
  	const char *p, *q, *dirsep = NULL;
  
  	for (p = one, q = two; *p && *q; p++, q++) {
  		if (*p == '/' && *q == '/')
  			dirsep = p;
  		else if (*p != *q)
  			break;
  	}
  
  	return dirsep ? (dirsep - one) + 1 : 0;
  }
  
  int git_fs_path_make_relative(git_str *path, const char *parent)
  {
  	const char *p, *q, *p_dirsep, *q_dirsep;
  	size_t plen = path->size, newlen, alloclen, depth = 1, i, offset;
  
  	for (p_dirsep = p = path->ptr, q_dirsep = q = parent; *p && *q; p++, q++) {
  		if (*p == '/' && *q == '/') {
  			p_dirsep = p;
  			q_dirsep = q;
  		}
  		else if (*p != *q)
  			break;
  	}
  
  	/* need at least 1 common path segment */
  	if ((p_dirsep == path->ptr || q_dirsep == parent) &&
  		(*p_dirsep != '/' || *q_dirsep != '/')) {
  		git_error_set(GIT_ERROR_INVALID,
  			"%s is not a parent of %s", parent, path->ptr);
  		return GIT_ENOTFOUND;
  	}
  
  	if (*p == '/' && !*q)
  		p++;
  	else if (!*p && *q == '/')
  		q++;
  	else if (!*p && !*q)
  		return git_str_clear(path), 0;
  	else {
  		p = p_dirsep + 1;
  		q = q_dirsep + 1;
  	}
  
  	plen -= (p - path->ptr);
  
  	if (!*q)
  		return git_str_set(path, p, plen);
  
  	for (; (q = strchr(q, '/')) && *(q + 1); q++)
  		depth++;
  
  	GIT_ERROR_CHECK_ALLOC_MULTIPLY(&newlen, depth, 3);
  	GIT_ERROR_CHECK_ALLOC_ADD(&newlen, newlen, plen);
  
  	GIT_ERROR_CHECK_ALLOC_ADD(&alloclen, newlen, 1);
  
  	/* save the offset as we might realllocate the pointer */
  	offset = p - path->ptr;
  	if (git_str_try_grow(path, alloclen, 1) < 0)
  		return -1;
  	p = path->ptr + offset;
  
  	memmove(path->ptr + (depth * 3), p, plen + 1);
  
  	for (i = 0; i < depth; i++)
  		memcpy(path->ptr + (i * 3), "../", 3);
  
  	path->size = newlen;
  	return 0;
  }
  
  bool git_fs_path_has_non_ascii(const char *path, size_t pathlen)
  {
  	const uint8_t *scan = (const uint8_t *)path, *end;
  
  	for (end = scan + pathlen; scan < end; ++scan)
  		if (*scan & 0x80)
  			return true;
  
  	return false;
  }
  
  #ifdef GIT_USE_ICONV
  
  int git_fs_path_iconv_init_precompose(git_fs_path_iconv_t *ic)
  {
  	git_str_init(&ic->buf, 0);
  	ic->map = iconv_open(GIT_PATH_REPO_ENCODING, GIT_PATH_NATIVE_ENCODING);
  	return 0;
  }
  
  void git_fs_path_iconv_clear(git_fs_path_iconv_t *ic)
  {
  	if (ic) {
  		if (ic->map != (iconv_t)-1)
  			iconv_close(ic->map);
  		git_str_dispose(&ic->buf);
  	}
  }
  
  int git_fs_path_iconv(git_fs_path_iconv_t *ic, const char **in, size_t *inlen)
  {
  	char *nfd = (char*)*in, *nfc;
  	size_t nfdlen = *inlen, nfclen, wantlen = nfdlen, alloclen, rv;
  	int retry = 1;
  
  	if (!ic || ic->map == (iconv_t)-1 ||
  		!git_fs_path_has_non_ascii(*in, *inlen))
  		return 0;
  
  	git_str_clear(&ic->buf);
  
  	while (1) {
  		GIT_ERROR_CHECK_ALLOC_ADD(&alloclen, wantlen, 1);
  		if (git_str_grow(&ic->buf, alloclen) < 0)
  			return -1;
  
  		nfc    = ic->buf.ptr   + ic->buf.size;
  		nfclen = ic->buf.asize - ic->buf.size;
  
  		rv = iconv(ic->map, &nfd, &nfdlen, &nfc, &nfclen);
  
  		ic->buf.size = (nfc - ic->buf.ptr);
  
  		if (rv != (size_t)-1)
  			break;
  
  		/* if we cannot convert the data (probably because iconv thinks
  		 * it is not valid UTF-8 source data), then use original data
  		 */
  		if (errno != E2BIG)
  			return 0;
  
  		/* make space for 2x the remaining data to be converted
  		 * (with per retry overhead to avoid infinite loops)
  		 */
  		wantlen = ic->buf.size + max(nfclen, nfdlen) * 2 + (size_t)(retry * 4);
  
  		if (retry++ > 4)
  			goto fail;
  	}
  
  	ic->buf.ptr[ic->buf.size] = '\0';
  
  	*in    = ic->buf.ptr;
  	*inlen = ic->buf.size;
  
  	return 0;
  
  fail:
  	git_error_set(GIT_ERROR_OS, "unable to convert unicode path data");
  	return -1;
  }
  
  static const char *nfc_file = "\xC3\x85\x73\x74\x72\xC3\xB6\x6D";
  static const char *nfd_file = "\x41\xCC\x8A\x73\x74\x72\x6F\xCC\x88\x6D";
  
  /* Check if the platform is decomposing unicode data for us.  We will
   * emulate core Git and prefer to use precomposed unicode data internally
   * on these platforms, composing the decomposed unicode on the fly.
   *
   * This mainly happens on the Mac where HDFS stores filenames as
   * decomposed unicode.  Even on VFAT and SAMBA file systems, the Mac will
   * return decomposed unicode from readdir() even when the actual
   * filesystem is storing precomposed unicode.
   */
  bool git_fs_path_does_decompose_unicode(const char *root)
  {
  	git_str nfc_path = GIT_STR_INIT;
  	git_str nfd_path = GIT_STR_INIT;
  	int fd;
  	bool found_decomposed = false;
  	size_t orig_len;
  	const char *trailer;
  
  	/* Create a file using a precomposed path and then try to find it
  	 * using the decomposed name.  If the lookup fails, then we will mark
  	 * that we should precompose unicode for this repository.
  	 */
  	if (git_str_joinpath(&nfc_path, root, nfc_file) < 0)
  		goto done;
  
  	/* record original path length before trailer */
  	orig_len = nfc_path.size;
  
  	if ((fd = git_futils_mktmp(&nfc_path, nfc_path.ptr, 0666)) < 0)
  		goto done;
  	p_close(fd);
  
  	trailer = nfc_path.ptr + orig_len;
  
  	/* try to look up as NFD path */
  	if (git_str_joinpath(&nfd_path, root, nfd_file) < 0 ||
  	    git_str_puts(&nfd_path, trailer) < 0)
  		goto done;
  
  	found_decomposed = git_fs_path_exists(nfd_path.ptr);
  
  	/* remove temporary file (using original precomposed path) */
  	(void)p_unlink(nfc_path.ptr);
  
  done:
  	git_str_dispose(&nfc_path);
  	git_str_dispose(&nfd_path);
  	return found_decomposed;
  }
  
  #else
  
  bool git_fs_path_does_decompose_unicode(const char *root)
  {
  	GIT_UNUSED(root);
  	return false;
  }
  
  #endif
  
  #if defined(__sun) || defined(__GNU__)
  typedef char path_dirent_data[sizeof(struct dirent) + FILENAME_MAX + 1];
  #else
  typedef struct dirent path_dirent_data;
  #endif
  
  int git_fs_path_direach(
  	git_str *path,
  	uint32_t flags,
  	int (*fn)(void *, git_str *),
  	void *arg)
  {
  	int error = 0;
  	ssize_t wd_len;
  	DIR *dir;
  	struct dirent *de;
  
  #ifdef GIT_USE_ICONV
  	git_fs_path_iconv_t ic = GIT_PATH_ICONV_INIT;
  #endif
  
  	GIT_UNUSED(flags);
  
  	if (git_fs_path_to_dir(path) < 0)
  		return -1;
  
  	wd_len = git_str_len(path);
  
  	if ((dir = opendir(path->ptr)) == NULL) {
  		git_error_set(GIT_ERROR_OS, "failed to open directory '%s'", path->ptr);
  		if (errno == ENOENT)
  			return GIT_ENOTFOUND;
  
  		return -1;
  	}
  
  #ifdef GIT_USE_ICONV
  	if ((flags & GIT_FS_PATH_DIR_PRECOMPOSE_UNICODE) != 0)
  		(void)git_fs_path_iconv_init_precompose(&ic);
  #endif
  
  	while ((de = readdir(dir)) != NULL) {
  		const char *de_path = de->d_name;
  		size_t de_len = strlen(de_path);
  
  		if (git_fs_path_is_dot_or_dotdot(de_path))
  			continue;
  
  #ifdef GIT_USE_ICONV
  		if ((error = git_fs_path_iconv(&ic, &de_path, &de_len)) < 0)
  			break;
  #endif
  
  		if ((error = git_str_put(path, de_path, de_len)) < 0)
  			break;
  
  		git_error_clear();
  		error = fn(arg, path);
  
  		git_str_truncate(path, wd_len); /* restore path */
  
  		/* Only set our own error if the callback did not set one already */
  		if (error != 0) {
  			if (!git_error_last())
  				ensure_error_set(error);
  
  			break;
  		}
  	}
  
  	closedir(dir);
  
  #ifdef GIT_USE_ICONV
  	git_fs_path_iconv_clear(&ic);
  #endif
  
  	return error;
  }
  
  #if defined(GIT_WIN32) && !defined(__MINGW32__)
  
  /* Using _FIND_FIRST_EX_LARGE_FETCH may increase performance in Windows 7
   * and better.
   */
  #ifndef FIND_FIRST_EX_LARGE_FETCH
  # define FIND_FIRST_EX_LARGE_FETCH 2
  #endif
  
  int git_fs_path_diriter_init(
  	git_fs_path_diriter *diriter,
  	const char *path,
  	unsigned int flags)
  {
  	git_win32_path path_filter;
  
  	static int is_win7_or_later = -1;
  	if (is_win7_or_later < 0)
  		is_win7_or_later = git_has_win32_version(6, 1, 0);
  
  	GIT_ASSERT_ARG(diriter);
  	GIT_ASSERT_ARG(path);
  
  	memset(diriter, 0, sizeof(git_fs_path_diriter));
  	diriter->handle = INVALID_HANDLE_VALUE;
  
  	if (git_str_puts(&diriter->path_utf8, path) < 0)
  		return -1;
  
  	path_trim_slashes(&diriter->path_utf8);
  
  	if (diriter->path_utf8.size == 0) {
  		git_error_set(GIT_ERROR_FILESYSTEM, "could not open directory '%s'", path);
  		return -1;
  	}
  
  	if ((diriter->parent_len = git_win32_path_from_utf8(diriter->path, diriter->path_utf8.ptr)) < 0 ||
  			!git_win32__findfirstfile_filter(path_filter, diriter->path_utf8.ptr)) {
  		git_error_set(GIT_ERROR_OS, "could not parse the directory path '%s'", path);
  		return -1;
  	}
  
  	diriter->handle = FindFirstFileExW(
  		path_filter,
  		is_win7_or_later ? FindExInfoBasic : FindExInfoStandard,
  		&diriter->current,
  		FindExSearchNameMatch,
  		NULL,
  		is_win7_or_later ? FIND_FIRST_EX_LARGE_FETCH : 0);
  
  	if (diriter->handle == INVALID_HANDLE_VALUE) {
  		git_error_set(GIT_ERROR_OS, "could not open directory '%s'", path);
  		return -1;
  	}
  
  	diriter->parent_utf8_len = diriter->path_utf8.size;
  	diriter->flags = flags;
  	return 0;
  }
  
  static int diriter_update_paths(git_fs_path_diriter *diriter)
  {
  	size_t filename_len, path_len;
  
  	filename_len = wcslen(diriter->current.cFileName);
  
  	if (GIT_ADD_SIZET_OVERFLOW(&path_len, diriter->parent_len, filename_len) ||
  		GIT_ADD_SIZET_OVERFLOW(&path_len, path_len, 2))
  		return -1;
  
  	if (path_len > GIT_WIN_PATH_UTF16) {
  		git_error_set(GIT_ERROR_FILESYSTEM,
  			"invalid path '%.*ls\\%ls' (path too long)",
  			diriter->parent_len, diriter->path, diriter->current.cFileName);
  		return -1;
  	}
  
  	diriter->path[diriter->parent_len] = L'\\';
  	memcpy(&diriter->path[diriter->parent_len+1],
  		diriter->current.cFileName, filename_len * sizeof(wchar_t));
  	diriter->path[path_len-1] = L'\0';
  
  	git_str_truncate(&diriter->path_utf8, diriter->parent_utf8_len);
  
  	if (diriter->parent_utf8_len > 0 &&
  		diriter->path_utf8.ptr[diriter->parent_utf8_len-1] != '/')
  		git_str_putc(&diriter->path_utf8, '/');
  
  	git_str_put_w(&diriter->path_utf8, diriter->current.cFileName, filename_len);
  
  	if (git_str_oom(&diriter->path_utf8))
  		return -1;
  
  	return 0;
  }
  
  int git_fs_path_diriter_next(git_fs_path_diriter *diriter)
  {
  	bool skip_dot = !(diriter->flags & GIT_FS_PATH_DIR_INCLUDE_DOT_AND_DOTDOT);
  
  	do {
  		/* Our first time through, we already have the data from
  		 * FindFirstFileW.  Use it, otherwise get the next file.
  		 */
  		if (!diriter->needs_next)
  			diriter->needs_next = 1;
  		else if (!FindNextFileW(diriter->handle, &diriter->current))
  			return GIT_ITEROVER;
  	} while (skip_dot && git_fs_path_is_dot_or_dotdotW(diriter->current.cFileName));
  
  	if (diriter_update_paths(diriter) < 0)
  		return -1;
  
  	return 0;
  }
  
  int git_fs_path_diriter_filename(
  	const char **out,
  	size_t *out_len,
  	git_fs_path_diriter *diriter)
  {
  	GIT_ASSERT_ARG(out);
  	GIT_ASSERT_ARG(out_len);
  	GIT_ASSERT_ARG(diriter);
  	GIT_ASSERT(diriter->path_utf8.size > diriter->parent_utf8_len);
  
  	*out = &diriter->path_utf8.ptr[diriter->parent_utf8_len+1];
  	*out_len = diriter->path_utf8.size - diriter->parent_utf8_len - 1;
  	return 0;
  }
  
  int git_fs_path_diriter_fullpath(
  	const char **out,
  	size_t *out_len,
  	git_fs_path_diriter *diriter)
  {
  	GIT_ASSERT_ARG(out);
  	GIT_ASSERT_ARG(out_len);
  	GIT_ASSERT_ARG(diriter);
  
  	*out = diriter->path_utf8.ptr;
  	*out_len = diriter->path_utf8.size;
  	return 0;
  }
  
  int git_fs_path_diriter_stat(struct stat *out, git_fs_path_diriter *diriter)
  {
  	GIT_ASSERT_ARG(out);
  	GIT_ASSERT_ARG(diriter);
  
  	return git_win32__file_attribute_to_stat(out,
  		(WIN32_FILE_ATTRIBUTE_DATA *)&diriter->current,
  		diriter->path);
  }
  
  void git_fs_path_diriter_free(git_fs_path_diriter *diriter)
  {
  	if (diriter == NULL)
  		return;
  
  	git_str_dispose(&diriter->path_utf8);
  
  	if (diriter->handle != INVALID_HANDLE_VALUE) {
  		FindClose(diriter->handle);
  		diriter->handle = INVALID_HANDLE_VALUE;
  	}
  }
  
  #else
  
  int git_fs_path_diriter_init(
  	git_fs_path_diriter *diriter,
  	const char *path,
  	unsigned int flags)
  {
  	GIT_ASSERT_ARG(diriter);
  	GIT_ASSERT_ARG(path);
  
  	memset(diriter, 0, sizeof(git_fs_path_diriter));
  
  	if (git_str_puts(&diriter->path, path) < 0)
  		return -1;
  
  	path_trim_slashes(&diriter->path);
  
  	if (diriter->path.size == 0) {
  		git_error_set(GIT_ERROR_FILESYSTEM, "could not open directory '%s'", path);
  		return -1;
  	}
  
  	if ((diriter->dir = opendir(diriter->path.ptr)) == NULL) {
  		git_str_dispose(&diriter->path);
  
  		git_error_set(GIT_ERROR_OS, "failed to open directory '%s'", path);
  		return -1;
  	}
  
  #ifdef GIT_USE_ICONV
  	if ((flags & GIT_FS_PATH_DIR_PRECOMPOSE_UNICODE) != 0)
  		(void)git_fs_path_iconv_init_precompose(&diriter->ic);
  #endif
  
  	diriter->parent_len = diriter->path.size;
  	diriter->flags = flags;
  
  	return 0;
  }
  
  int git_fs_path_diriter_next(git_fs_path_diriter *diriter)
  {
  	struct dirent *de;
  	const char *filename;
  	size_t filename_len;
  	bool skip_dot = !(diriter->flags & GIT_FS_PATH_DIR_INCLUDE_DOT_AND_DOTDOT);
  	int error = 0;
  
  	GIT_ASSERT_ARG(diriter);
  
  	errno = 0;
  
  	do {
  		if ((de = readdir(diriter->dir)) == NULL) {
  			if (!errno)
  				return GIT_ITEROVER;
  
  			git_error_set(GIT_ERROR_OS,
  				"could not read directory '%s'", diriter->path.ptr);
  			return -1;
  		}
  	} while (skip_dot && git_fs_path_is_dot_or_dotdot(de->d_name));
  
  	filename = de->d_name;
  	filename_len = strlen(filename);
  
  #ifdef GIT_USE_ICONV
  	if ((diriter->flags & GIT_FS_PATH_DIR_PRECOMPOSE_UNICODE) != 0 &&
  		(error = git_fs_path_iconv(&diriter->ic, &filename, &filename_len)) < 0)
  		return error;
  #endif
  
  	git_str_truncate(&diriter->path, diriter->parent_len);
  
  	if (diriter->parent_len > 0 &&
  		diriter->path.ptr[diriter->parent_len-1] != '/')
  		git_str_putc(&diriter->path, '/');
  
  	git_str_put(&diriter->path, filename, filename_len);
  
  	if (git_str_oom(&diriter->path))
  		return -1;
  
  	return error;
  }
  
  int git_fs_path_diriter_filename(
  	const char **out,
  	size_t *out_len,
  	git_fs_path_diriter *diriter)
  {
  	GIT_ASSERT_ARG(out);
  	GIT_ASSERT_ARG(out_len);
  	GIT_ASSERT_ARG(diriter);
  	GIT_ASSERT(diriter->path.size > diriter->parent_len);
  
  	*out = &diriter->path.ptr[diriter->parent_len+1];
  	*out_len = diriter->path.size - diriter->parent_len - 1;
  	return 0;
  }
  
  int git_fs_path_diriter_fullpath(
  	const char **out,
  	size_t *out_len,
  	git_fs_path_diriter *diriter)
  {
  	GIT_ASSERT_ARG(out);
  	GIT_ASSERT_ARG(out_len);
  	GIT_ASSERT_ARG(diriter);
  
  	*out = diriter->path.ptr;
  	*out_len = diriter->path.size;
  	return 0;
  }
  
  int git_fs_path_diriter_stat(struct stat *out, git_fs_path_diriter *diriter)
  {
  	GIT_ASSERT_ARG(out);
  	GIT_ASSERT_ARG(diriter);
  
  	return git_fs_path_lstat(diriter->path.ptr, out);
  }
  
  void git_fs_path_diriter_free(git_fs_path_diriter *diriter)
  {
  	if (diriter == NULL)
  		return;
  
  	if (diriter->dir) {
  		closedir(diriter->dir);
  		diriter->dir = NULL;
  	}
  
  #ifdef GIT_USE_ICONV
  	git_fs_path_iconv_clear(&diriter->ic);
  #endif
  
  	git_str_dispose(&diriter->path);
  }
  
  #endif
  
  int git_fs_path_dirload(
  	git_vector *contents,
  	const char *path,
  	size_t prefix_len,
  	uint32_t flags)
  {
  	git_fs_path_diriter iter = GIT_FS_PATH_DIRITER_INIT;
  	const char *name;
  	size_t name_len;
  	char *dup;
  	int error;
  
  	GIT_ASSERT_ARG(contents);
  	GIT_ASSERT_ARG(path);
  
  	if ((error = git_fs_path_diriter_init(&iter, path, flags)) < 0)
  		return error;
  
  	while ((error = git_fs_path_diriter_next(&iter)) == 0) {
  		if ((error = git_fs_path_diriter_fullpath(&name, &name_len, &iter)) < 0)
  			break;
  
  		GIT_ASSERT(name_len > prefix_len);
  
  		dup = git__strndup(name + prefix_len, name_len - prefix_len);
  		GIT_ERROR_CHECK_ALLOC(dup);
  
  		if ((error = git_vector_insert(contents, dup)) < 0)
  			break;
  	}
  
  	if (error == GIT_ITEROVER)
  		error = 0;
  
  	git_fs_path_diriter_free(&iter);
  	return error;
  }
  
  int git_fs_path_from_url_or_path(git_str *local_path_out, const char *url_or_path)
  {
  	if (git_fs_path_is_local_file_url(url_or_path))
  		return git_fs_path_fromurl(local_path_out, url_or_path);
  	else
  		return git_str_sets(local_path_out, url_or_path);
  }
  
  /* Reject paths like AUX or COM1, or those versions that end in a dot or
   * colon.  ("AUX." or "AUX:")
   */
  GIT_INLINE(bool) validate_dospath(
  	const char *component,
  	size_t len,
  	const char dospath[3],
  	bool trailing_num)
  {
  	size_t last = trailing_num ? 4 : 3;
  
  	if (len < last || git__strncasecmp(component, dospath, 3) != 0)
  		return true;
  
  	if (trailing_num && (component[3] < '1' || component[3] > '9'))
  		return true;
  
  	return (len > last &&
  		component[last] != '.' &&
  		component[last] != ':');
  }
  
  GIT_INLINE(bool) validate_char(unsigned char c, unsigned int flags)
  {
  	if ((flags & GIT_FS_PATH_REJECT_BACKSLASH) && c == '\\')
  		return false;
  
  	if ((flags & GIT_FS_PATH_REJECT_SLASH) && c == '/')
  		return false;
  
  	if (flags & GIT_FS_PATH_REJECT_NT_CHARS) {
  		if (c < 32)
  			return false;
  
  		switch (c) {
  		case '<':
  		case '>':
  		case ':':
  		case '"':
  		case '|':
  		case '?':
  		case '*':
  			return false;
  		}
  	}
  
  	return true;
  }
  
  /*
   * We fundamentally don't like some paths when dealing with user-inputted
   * strings (to avoid escaping a sandbox): we don't want dot or dot-dot
   * anywhere, we want to avoid writing weird paths on Windows that can't
   * be handled by tools that use the non-\\?\ APIs, we don't want slashes
   * or double slashes at the end of paths that can make them ambiguous.
   *
   * For checkout, we don't want to recurse into ".git" either.
   */
  static bool validate_component(
  	const char *component,
  	size_t len,
  	unsigned int flags)
  {
  	if (len == 0)
  		return !(flags & GIT_FS_PATH_REJECT_EMPTY_COMPONENT);
  
  	if ((flags & GIT_FS_PATH_REJECT_TRAVERSAL) &&
  	    len == 1 && component[0] == '.')
  		return false;
  
  	if ((flags & GIT_FS_PATH_REJECT_TRAVERSAL) &&
  	    len == 2 && component[0] == '.' && component[1] == '.')
  		return false;
  
  	if ((flags & GIT_FS_PATH_REJECT_TRAILING_DOT) &&
  	    component[len - 1] == '.')
  		return false;
  
  	if ((flags & GIT_FS_PATH_REJECT_TRAILING_SPACE) &&
  	    component[len - 1] == ' ')
  		return false;
  
  	if ((flags & GIT_FS_PATH_REJECT_TRAILING_COLON) &&
  	    component[len - 1] == ':')
  		return false;
  
  	if (flags & GIT_FS_PATH_REJECT_DOS_PATHS) {
  		if (!validate_dospath(component, len, "CON", false) ||
  		    !validate_dospath(component, len, "PRN", false) ||
  		    !validate_dospath(component, len, "AUX", false) ||
  		    !validate_dospath(component, len, "NUL", false) ||
  		    !validate_dospath(component, len, "COM", true)  ||
  		    !validate_dospath(component, len, "LPT", true))
  			return false;
  	}
  
  	return true;
  }
  
  #ifdef GIT_WIN32
  GIT_INLINE(bool) validate_length(
  	const char *path,
  	size_t len,
  	size_t utf8_char_len)
  {
  	GIT_UNUSED(path);
  	GIT_UNUSED(len);
  
  	return (utf8_char_len <= MAX_PATH);
  }
  #endif
  
  bool git_fs_path_str_is_valid_ext(
  	const git_str *path,
  	unsigned int flags,
  	bool (*validate_char_cb)(char ch, void *payload),
  	bool (*validate_component_cb)(const char *component, size_t len, void *payload),
  	bool (*validate_length_cb)(const char *path, size_t len, size_t utf8_char_len),
  	void *payload)
  {
  	const char *start, *c;
  	size_t len = 0;
  
  	if (!flags)
  		return true;
  
  	for (start = c = path->ptr; *c && len < path->size; c++, len++) {
  		if (!validate_char(*c, flags))
  			return false;
  
  		if (validate_char_cb && !validate_char_cb(*c, payload))
  			return false;
  
  		if (*c != '/')
  			continue;
  
  		if (!validate_component(start, (c - start), flags))
  			return false;
  
  		if (validate_component_cb &&
  		    !validate_component_cb(start, (c - start), payload))
  			return false;
  
  		start = c + 1;
  	}
  
  	/*
  	 * We want to support paths specified as either `const char *`
  	 * or `git_str *`; we pass size as `SIZE_MAX` when we use a
  	 * `const char *` to avoid a `strlen`.  Ensure that we didn't
  	 * have a NUL in the buffer if there was a non-SIZE_MAX length.
  	 */
  	if (path->size != SIZE_MAX && len != path->size)
  		return false;
  
  	if (!validate_component(start, (c - start), flags))
  		return false;
  
  	if (validate_component_cb &&
  	    !validate_component_cb(start, (c - start), payload))
  		return false;
  
  #ifdef GIT_WIN32
  	if ((flags & GIT_FS_PATH_REJECT_LONG_PATHS) != 0) {
  		size_t utf8_len = git_utf8_char_length(path->ptr, len);
  
  		if (!validate_length(path->ptr, len, utf8_len))
  			return false;
  
  		if (validate_length_cb &&
  		    !validate_length_cb(path->ptr, len, utf8_len))
  			return false;
  	}
  #else
  	GIT_UNUSED(validate_length_cb);
  #endif
  
  	return true;
  }
  
  int git_fs_path_validate_str_length_with_suffix(
  	git_str *path,
  	size_t suffix_len)
  {
  #ifdef GIT_WIN32
  	size_t utf8_len = git_utf8_char_length(path->ptr, path->size);
  	size_t total_len;
  
  	if (GIT_ADD_SIZET_OVERFLOW(&total_len, utf8_len, suffix_len) ||
  	    total_len > MAX_PATH) {
  
  		git_error_set(GIT_ERROR_FILESYSTEM, "path too long: '%.*s'",
  			(int)path->size, path->ptr);
  		return -1;
  	}
  #else
  	GIT_UNUSED(path);
  	GIT_UNUSED(suffix_len);
  #endif
  
  	return 0;
  }
  
  int git_fs_path_normalize_slashes(git_str *out, const char *path)
  {
  	int error;
  	char *p;
  
  	if ((error = git_str_puts(out, path)) < 0)
  		return error;
  
  	for (p = out->ptr; *p; p++) {
  		if (*p == '\\')
  			*p = '/';
  	}
  
  	return 0;
  }
  
  bool git_fs_path_supports_symlinks(const char *dir)
  {
  	git_str path = GIT_STR_INIT;
  	bool supported = false;
  	struct stat st;
  	int fd;
  
  	if ((fd = git_futils_mktmp(&path, dir, 0666)) < 0 ||
  	    p_close(fd) < 0 ||
  	    p_unlink(path.ptr) < 0 ||
  	    p_symlink("testing", path.ptr) < 0 ||
  	    p_lstat(path.ptr, &st) < 0)
  		goto done;
  
  	supported = (S_ISLNK(st.st_mode) != 0);
  done:
  	if (path.size)
  		(void)p_unlink(path.ptr);
  	git_str_dispose(&path);
  	return supported;
  }
  
  static git_fs_path__mock_owner_t mock_owner = GIT_FS_PATH_MOCK_OWNER_NONE;
  
  void git_fs_path__set_owner(git_fs_path__mock_owner_t owner)
  {
  	mock_owner = owner;
  }
  
  #ifdef GIT_WIN32
  static PSID *sid_dup(PSID sid)
  {
  	DWORD len;
  	PSID dup;
  
  	len = GetLengthSid(sid);
  
  	if ((dup = git__malloc(len)) == NULL)
  		return NULL;
  
  	if (!CopySid(len, dup, sid)) {
  		git_error_set(GIT_ERROR_OS, "could not duplicate sid");
  		git__free(dup);
  		return NULL;
  	}
  
  	return dup;
  }
  
  static int current_user_sid(PSID *out)
  {
  	TOKEN_USER *info = NULL;
  	HANDLE token = NULL;
  	DWORD len = 0;
  	int error = -1;
  
  	if (!OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &token)) {
  		git_error_set(GIT_ERROR_OS, "could not lookup process information");
  		goto done;
  	}
  
  	if (GetTokenInformation(token, TokenUser, NULL, 0, &len) ||
  		GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
  		git_error_set(GIT_ERROR_OS, "could not lookup token metadata");
  		goto done;
  	}
  
  	info = git__malloc(len);
  	GIT_ERROR_CHECK_ALLOC(info);
  
  	if (!GetTokenInformation(token, TokenUser, info, len, &len)) {
  		git_error_set(GIT_ERROR_OS, "could not lookup current user");
  		goto done;
  	}
  
  	if ((*out = sid_dup(info->User.Sid)))
  		error = 0;
  
  done:
  	if (token)
  		CloseHandle(token);
  
  	git__free(info);
  	return error;
  }
  
  static int file_owner_sid(PSID *out, const char *path)
  {
  	git_win32_path path_w32;
  	PSECURITY_DESCRIPTOR descriptor = NULL;
  	PSID owner_sid;
  	DWORD ret;
  	int error = -1;
  
  	if (git_win32_path_from_utf8(path_w32, path) < 0)
  		return -1;
  
  	ret = GetNamedSecurityInfoW(path_w32, SE_FILE_OBJECT,
  		OWNER_SECURITY_INFORMATION | DACL_SECURITY_INFORMATION,
  		&owner_sid, NULL, NULL, NULL, &descriptor);
  
  	if (ret == ERROR_FILE_NOT_FOUND || ret == ERROR_PATH_NOT_FOUND)
  		error = GIT_ENOTFOUND;
  	else if (ret != ERROR_SUCCESS)
  		git_error_set(GIT_ERROR_OS, "failed to get security information");
  	else if (!IsValidSid(owner_sid))
  		git_error_set(GIT_ERROR_OS, "file owner is not valid");
  	else if ((*out = sid_dup(owner_sid)))
  		error = 0;
  
  	if (descriptor)
  		LocalFree(descriptor);
  
  	return error;
  }
  
  int git_fs_path_owner_is_current_user(bool *out, const char *path)
  {
  	PSID owner_sid = NULL, user_sid = NULL;
  	int error = -1;
  
  	if (mock_owner) {
  		*out = (mock_owner == GIT_FS_PATH_MOCK_OWNER_CURRENT_USER);
  		return 0;
  	}
  
  	if ((error = file_owner_sid(&owner_sid, path)) < 0 ||
  	    (error = current_user_sid(&user_sid)) < 0)
  		goto done;
  
  	*out = EqualSid(owner_sid, user_sid);
  	error = 0;
  
  done:
  	git__free(owner_sid);
  	git__free(user_sid);
  	return error;
  }
  
  int git_fs_path_owner_is_system(bool *out, const char *path)
  {
  	PSID owner_sid;
  
  	if (mock_owner) {
  		*out = (mock_owner == GIT_FS_PATH_MOCK_OWNER_SYSTEM);
  		return 0;
  	}
  
  	if (file_owner_sid(&owner_sid, path) < 0)
  		return -1;
  
  	*out = IsWellKnownSid(owner_sid, WinBuiltinAdministratorsSid) ||
  	       IsWellKnownSid(owner_sid, WinLocalSystemSid);
  
  	git__free(owner_sid);
  	return 0;
  }
  
  int git_fs_path_owner_is_system_or_current_user(bool *out, const char *path)
  {
  	PSID owner_sid = NULL, user_sid = NULL;
  	int error = -1;
  
  	if (mock_owner) {
  		*out = (mock_owner == GIT_FS_PATH_MOCK_OWNER_SYSTEM ||
  		        mock_owner == GIT_FS_PATH_MOCK_OWNER_CURRENT_USER);
  		return 0;
  	}
  
  	if (file_owner_sid(&owner_sid, path) < 0)
  		goto done;
  
  	if (IsWellKnownSid(owner_sid, WinBuiltinAdministratorsSid) ||
  	    IsWellKnownSid(owner_sid, WinLocalSystemSid)) {
  		*out = 1;
  		error = 0;
  		goto done;
  	}
  
  	if (current_user_sid(&user_sid) < 0)
  		goto done;
  
  	*out = EqualSid(owner_sid, user_sid);
  	error = 0;
  
  done:
  	git__free(owner_sid);
  	git__free(user_sid);
  	return error;
  }
  
  #else
  
  static int fs_path_owner_is(bool *out, const char *path, uid_t *uids, size_t uids_len)
  {
  	struct stat st;
  	size_t i;
  
  	*out = false;
  
  	if (p_lstat(path, &st) != 0) {
  		if (errno == ENOENT)
  			return GIT_ENOTFOUND;
  
  		git_error_set(GIT_ERROR_OS, "could not stat '%s'", path);
  		return -1;
  	}
  
  	for (i = 0; i < uids_len; i++) {
  		if (uids[i] == st.st_uid) {
  			*out = true;
  			break;
  		}
  	}
  
  	return 0;
  }
  
  int git_fs_path_owner_is_current_user(bool *out, const char *path)
  {
  	uid_t userid = geteuid();
  
  	if (mock_owner) {
  		*out = (mock_owner == GIT_FS_PATH_MOCK_OWNER_CURRENT_USER);
  		return 0;
  	}
  
  	return fs_path_owner_is(out, path, &userid, 1);
  }
  
  int git_fs_path_owner_is_system(bool *out, const char *path)
  {
  	uid_t userid = 0;
  
  	if (mock_owner) {
  		*out = (mock_owner == GIT_FS_PATH_MOCK_OWNER_SYSTEM);
  		return 0;
  	}
  
  	return fs_path_owner_is(out, path, &userid, 1);
  }
  
  int git_fs_path_owner_is_system_or_current_user(bool *out, const char *path)
  {
  	uid_t userids[2] = { geteuid(), 0 };
  
  	if (mock_owner) {
  		*out = (mock_owner == GIT_FS_PATH_MOCK_OWNER_SYSTEM ||
  		        mock_owner == GIT_FS_PATH_MOCK_OWNER_CURRENT_USER);
  		return 0;
  	}
  
  	return fs_path_owner_is(out, path, userids, 2);
  }
  
  #endif
  
  int git_fs_path_find_executable(git_str *fullpath, const char *executable)
  {
  #ifdef GIT_WIN32
  	git_win32_path fullpath_w, executable_w;
  	int error;
  
  	if (git__utf8_to_16(executable_w, GIT_WIN_PATH_MAX, executable) < 0)
  		return -1;
  
  	error = git_win32_path_find_executable(fullpath_w, executable_w);
  
  	if (error == 0)
  		error = git_str_put_w(fullpath, fullpath_w, wcslen(fullpath_w));
  
  	return error;
  #else
  	git_str path = GIT_STR_INIT;
  	const char *current_dir, *term;
  	bool found = false;
  
  	if (git__getenv(&path, "PATH") < 0)
  		return -1;
  
  	current_dir = path.ptr;
  
  	while (*current_dir) {
  		if (! (term = strchr(current_dir, GIT_PATH_LIST_SEPARATOR)))
  			term = strchr(current_dir, '\0');
  
  		git_str_clear(fullpath);
  		if (git_str_put(fullpath, current_dir, (term - current_dir)) < 0 ||
  		    git_str_putc(fullpath, '/') < 0 ||
  		    git_str_puts(fullpath, executable) < 0)
  			return -1;
  
  		if (git_fs_path_isfile(fullpath->ptr)) {
  			found = true;
  			break;
  		}
  
  		current_dir = term;
  
  		while (*current_dir == GIT_PATH_LIST_SEPARATOR)
  			current_dir++;
  	}
  
  	git_str_dispose(&path);
  
  	if (found)
  		return 0;
  
  	git_str_clear(fullpath);
  	return GIT_ENOTFOUND;
  #endif
  }
  

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