336 lines
6.7 KiB
C++
336 lines
6.7 KiB
C++
/*
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* \brief Path handling utility
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* \author Norman Feske
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* \date 2011-02-17
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*/
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/*
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* Copyright (C) 2011-2013 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__OS__PATH_H_
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#define _INCLUDE__OS__PATH_H_
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/* Genode includes */
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#include <util/string.h>
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namespace Genode {
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class Path_base;
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template <unsigned> class Path;
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}
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class Genode::Path_base
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{
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public:
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class Path_too_long { };
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protected:
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static bool is_absolute(char const *path)
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{
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return path[0] == '/';
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}
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static bool ends_with(char c, char const *path)
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{
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return path[0] && (path[strlen(path) - 1] == c);
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}
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static void remove_char(char *buf)
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{
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for (; *buf; buf++)
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buf[0] = buf[1];
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}
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static void remove_trailing(char c, char *path)
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{
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int i = 0;
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while (path[i] && path[i + 1]) i++;
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/*
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* Never touch the first character to preserve the invariant of
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* the leading slash.
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*/
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if (i > 0 && path[i] == c)
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path[i] = 0;
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}
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template <typename T>
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static T *last_element(T *path)
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{
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T *result = path;
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for (; *path; path++)
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if (path[0] == '/' && path[1] != 0)
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result = path;
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return result;
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}
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static bool is_empty(char const *path)
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{
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return strlen(path) == 0;
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}
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/**
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* Remove superfluous single dots followed by a slash from path
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*/
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static void strip_superfluous_dotslashes(char *path)
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{
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for (; *path; path++) {
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if (path[0] != '/') continue;
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/* strip superfluous dots, e.g., "/abs/./path/" -> "/abs/path" */
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while (path[1] == '.' && path[2] == '/') {
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remove_char(path);
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remove_char(path);
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}
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}
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}
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static void strip_superfluous_slashes(char *path)
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{
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for (; *path; path++) {
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if (path[0] != '/') continue;
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/* strip superfluous slashes, e.g., "//path/" -> "/path" */
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while (path[1] == '/')
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remove_char(path);
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}
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}
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/**
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* Find double-dot path element
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*
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* \return index of the first dot of the found path element, or
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* 0 if no double-dot path element could be found.
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*/
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static unsigned find_double_dot_dir(char *path)
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{
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for (unsigned i = 0; path[i]; i++)
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if (path[i] == '/' && path[i + 1] == '.' && path[i + 2] == '.'
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&& (path[i + 3] == 0 || path[i + 3] == '/'))
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return i + 1;
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return 0;
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}
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static void strip(char *dst, unsigned count)
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{
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for (char const *src = dst + count; *src; )
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*dst++ = *src++;
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*dst = 0;
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}
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static void strip_double_dot_dirs(char *path)
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{
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unsigned i;
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while ((i = find_double_dot_dir(path))) {
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/* skip slash prepending the double dot */
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unsigned cut_start = i - 1;
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unsigned cut_end = i + 2;
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/* skip previous path element */
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while (cut_start > 0 && path[cut_start - 1] != '/')
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cut_start--;
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/* skip slash in front of the pair of dots */
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if (cut_start > 0)
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cut_start--;
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strip(path + cut_start, cut_end - cut_start);
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}
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}
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private:
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Path_base(const Path_base &);
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char * const _path;
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size_t const _path_max_len;
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/**
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* Append 'path'
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*
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* \throw Path_too_long
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*/
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void _append(char const *path)
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{
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size_t const orig_len = strlen(_path);
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if (strlen(path) + orig_len + 1 >= _path_max_len)
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throw Path_too_long();
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strncpy(_path + orig_len, path, _path_max_len - orig_len);
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}
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void _append_slash_if_needed()
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{
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if (!ends_with('/', _path))
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_append("/");
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}
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void _strip_from_begin(unsigned count) { strip(_path, count); }
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/**
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* Remove superfluous artifacts from absolute path
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*/
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void _canonicalize()
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{
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strip_superfluous_slashes(_path);
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strip_superfluous_dotslashes(_path);
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strip_double_dot_dirs(_path);
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remove_trailing('.', _path);
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}
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void _import(char const *path, char const *pwd = 0)
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{
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/*
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* Validate 'pwd' argument, if not supplied, enforce invariant
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* that 'pwd' is an absolute path.
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*/
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if (!pwd || strlen(pwd) == 0)
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pwd = "/";
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/*
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* Use argument path if absolute
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*/
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if (is_absolute(path))
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strncpy(_path, path, _path_max_len);
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/*
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* Otherwise, concatenate current working directory with
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* relative path.
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*/
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else {
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const char *const relative_path = path;
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strncpy(_path, pwd, _path_max_len);
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if (!is_empty(relative_path)) {
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/* make sure to have a slash separating both portions */
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_append_slash_if_needed();
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_append(relative_path);
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}
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}
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_canonicalize();
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}
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public:
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Path_base(char *buf, size_t buf_len,
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char const *path, char const *pwd = 0)
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:
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_path(buf), _path_max_len(buf_len)
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{
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_import(path, pwd);
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}
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void import(char const *path, char const *pwd = 0) { _import(path, pwd); }
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char *base() { return _path; }
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char const *base() const { return _path; }
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size_t max_len() { return _path_max_len; }
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void remove_trailing(char c) { remove_trailing(c, _path); }
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void keep_only_last_element()
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{
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char *dst = _path;
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for (char const *src = last_element(_path) ; *src; )
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*dst++ = *src++;
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*dst = 0;
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}
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void strip_last_element()
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{
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last_element(_path)[1] = 0;
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}
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bool equals(Path_base const &ref) const { return strcmp(ref._path, _path) == 0; }
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bool equals(char const *str) const { return strcmp(str, _path) == 0; }
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bool strip_prefix(char const *prefix)
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{
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unsigned prefix_len = strlen(prefix);
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if (strcmp(prefix, _path, prefix_len) != 0)
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return false;
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if (prefix_len > 0 && ends_with('/', prefix))
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prefix_len--;
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if (prefix[prefix_len] && prefix[prefix_len] != '/')
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return false;
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if (_path[prefix_len] && _path[prefix_len] != '/')
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return false;
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_strip_from_begin(prefix_len);
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return true;
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}
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bool has_single_element() const
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{
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/* count number of non-trailing slashes */
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unsigned num_slashes = 0;
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for (char const *p = _path; *p; p++)
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num_slashes += (p[0] == '/' && p[1] != 0);
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/*
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* Check if the leading slash is the only one, also check the
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* absence of any element.
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*/
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return (num_slashes == 1) && !equals("/");
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}
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void append(char const *str) { _append(str); _canonicalize(); }
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bool operator == (char const *other) const
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{
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return strcmp(_path, other) == 0;
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}
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bool operator != (char const *other) const
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{
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return strcmp(_path, other) != 0;
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}
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};
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template <unsigned MAX_LEN>
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class Genode::Path : public Path_base {
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private:
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char _buf[MAX_LEN];
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public:
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/**
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* Default constuctor
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*
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* Initializes the path to '/'.
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*/
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Path() : Path_base(_buf, sizeof(_buf), "/") { }
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/**
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* Constructor
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*/
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Path(char const *path, char const *pwd = 0)
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: Path_base(_buf, sizeof(_buf), path, pwd) { }
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constexpr size_t capacity() { return MAX_LEN; }
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};
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#endif /* _INCLUDE__OS__PATH_H_ */
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