b0b92e4ee2
This patch enables the use of the VFS from VFS plugins by passing a reference of the root directory to the constructors of file-system instances. Since it changes the signature of 'Vfs::Dir_file_system', any code that uses the VFS directly requires an adaptation. Fixes #2701
423 lines
10 KiB
C++
423 lines
10 KiB
C++
/*
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* \brief Front-end API for accessing a component-local virtual file system
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* \author Norman Feske
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* \date 2017-07-04
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*/
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/*
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* Copyright (C) 2017 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 Affero General Public License version 3.
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*/
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#ifndef _INCLUDE__GEMS__VFS_H_
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#define _INCLUDE__GEMS__VFS_H_
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/* Genode includes */
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#include <base/env.h>
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#include <base/allocator.h>
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#include <vfs/dir_file_system.h>
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#include <vfs/file_system_factory.h>
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namespace Genode {
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struct Directory;
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struct Root_directory;
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struct File;
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struct Readonly_file;
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struct File_content;
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}
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struct Genode::Directory : Noncopyable
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{
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public:
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struct Open_failed : Exception { };
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struct Read_dir_failed : Exception { };
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class Entry
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{
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private:
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Vfs::Directory_service::Dirent _dirent;
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friend class Directory;
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Entry() { }
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public:
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void print(Output &out) const
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{
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using Genode::print;
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using Vfs::Directory_service;
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print(out, _dirent.name, " (");
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switch (_dirent.type) {
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case Directory_service::DIRENT_TYPE_FILE: print(out, "file"); break;
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case Directory_service::DIRENT_TYPE_DIRECTORY: print(out, "dir"); break;
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case Directory_service::DIRENT_TYPE_SYMLINK: print(out, "symlink"); break;
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default: print(out, "other"); break;
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}
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print(out, ")");
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}
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typedef String<Vfs::Directory_service::DIRENT_MAX_NAME_LEN> Name;
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Name name() const { return Name(Cstring(_dirent.name)); }
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};
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typedef String<256> Path;
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private:
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Path const _path;
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Vfs::File_system &_fs;
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Entrypoint &_ep;
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Allocator &_alloc;
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Vfs::Vfs_handle *_handle = nullptr;
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friend class Readonly_file;
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friend class Root_directory;
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/**
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* Constructor used by 'Root_directory'
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*
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* \throw Open_failed
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*/
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Directory(Vfs::File_system &fs, Entrypoint &ep, Allocator &alloc)
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: _path(""), _fs(fs), _ep(ep), _alloc(alloc)
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{ }
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/*
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* Operations such as 'file_size' that are expected to be 'const' at
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* the API level, do internally require I/O with the outside world,
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* with involves non-const access to the VFS. This helper allows a
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* 'const' method to perform I/O at the VFS.
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*/
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Vfs::File_system &_nonconst_fs() const
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{
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return const_cast<Vfs::File_system &>(_fs);
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}
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Vfs::Directory_service::Stat _stat(Path const &rel_path) const
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{
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Vfs::Directory_service::Stat stat;
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/*
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* Ignore return value as the validity of the result is can be
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* checked by the caller via 'stat.mode != 0'.
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*/
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_nonconst_fs().stat(Path(_path, "/", rel_path).string(), stat);
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return stat;
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}
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public:
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struct Nonexistent_file : Exception { };
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struct Nonexistent_directory : Exception { };
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/**
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* Open sub directory
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*
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* \throw Nonexistent_directory
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*/
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Directory(Directory &other, Path const &rel_path)
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: _path(other._path, "/", rel_path), _fs(other._fs), _ep(other._ep),
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_alloc(other._alloc)
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{
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if (_fs.opendir(_path.string(), false, &_handle, _alloc) !=
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Vfs::Directory_service::OPENDIR_OK)
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throw Nonexistent_directory();
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}
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~Directory() { _handle->ds().close(_handle); }
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template <typename FN>
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void for_each_entry(FN const &fn)
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{
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for (unsigned i = 0;; i++) {
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Entry entry;
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_handle->seek(i * sizeof(entry._dirent));
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while (!_handle->fs().queue_read(_handle, sizeof(entry._dirent)))
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_ep.wait_and_dispatch_one_io_signal();
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Vfs::File_io_service::Read_result read_result;
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Vfs::file_size out_count = 0;
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for (;;) {
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read_result = _handle->fs().complete_read(_handle,
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(char*)&entry._dirent,
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sizeof(entry._dirent),
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out_count);
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if (read_result != Vfs::File_io_service::READ_QUEUED)
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break;
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_ep.wait_and_dispatch_one_io_signal();
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}
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if ((read_result != Vfs::File_io_service::READ_OK) ||
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(out_count < sizeof(entry._dirent))) {
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error("could not access directory '", _path, "'");
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throw Read_dir_failed();
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}
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if (entry._dirent.type == Vfs::Directory_service::DIRENT_TYPE_END)
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return;
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fn(entry);
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}
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}
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template <typename FN>
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void for_each_entry(FN const &fn) const
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{
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auto const_fn = [&] (Entry const &e) { fn(e); };
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const_cast<Directory &>(*this).for_each_entry(const_fn);
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}
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bool file_exists(Path const &rel_path) const
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{
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return _stat(rel_path).mode & Vfs::Directory_service::STAT_MODE_FILE;
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}
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bool directory_exists(Path const &rel_path) const
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{
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return _stat(rel_path).mode & Vfs::Directory_service::STAT_MODE_DIRECTORY;
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}
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/**
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* Return size of file at specified directory-relative path
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*
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* \throw Nonexistent_file file at path does not exist or
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* the access to the file is denied
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*
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*/
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Vfs::file_size file_size(Path const &rel_path) const
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{
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Vfs::Directory_service::Stat stat = _stat(rel_path);
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if (!(stat.mode & Vfs::Directory_service::STAT_MODE_FILE))
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throw Nonexistent_file();
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return stat.size;
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}
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};
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struct Genode::Root_directory : public Vfs::Io_response_handler,
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private Vfs::Global_file_system_factory,
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private Vfs::Dir_file_system,
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public Directory
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{
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void handle_io_response(Vfs::Vfs_handle::Context*) override { }
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Root_directory(Env &env, Allocator &alloc, Xml_node config)
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:
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Vfs::Global_file_system_factory(alloc),
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Vfs::Dir_file_system(env, alloc, config, *this, *this),
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Directory(*this, env.ep(), alloc)
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{ }
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void apply_config(Xml_node config) { Vfs::Dir_file_system::apply_config(config); }
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};
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struct Genode::File : Noncopyable
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{
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struct Open_failed : Exception { };
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struct Truncated_during_read : Exception { };
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typedef Directory::Path Path;
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};
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class Genode::Readonly_file : public File
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{
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private:
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Vfs::Vfs_handle *_handle = nullptr;
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Genode::Entrypoint &_ep;
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void _open(Vfs::File_system &fs, Allocator &alloc, Path const path)
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{
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Vfs::Directory_service::Open_result res =
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fs.open(path.string(), Vfs::Directory_service::OPEN_MODE_RDONLY,
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&_handle, alloc);
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if (res != Vfs::Directory_service::OPEN_OK) {
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error("failed to open file '", path, "'");
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throw Open_failed();
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}
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}
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/**
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* Strip off constness of 'Directory const &'
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*
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* Since the 'Readonly_file' API provides an abstraction over the
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* low-level VFS operations, the intuitive meaning of 'const' is
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* different between the 'Readonly_file' API and the VFS.
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*
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* At the VFS level, opening a file changes the internal state of the
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* VFS. Hence the operation is non-const. However, the user of the
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* 'Readonly_file' API expects the constness of a directory to
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* correspond to whether the directory can be modified or not. In the
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* case of instantiating a 'Readonly_file', one would expect that a
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* 'Directory const &' would suffice. The fact that - under the hood -
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* the 'Readonly_file' has to perform the nonconst 'open' operation at
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* the VFS is of not of interest.
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*/
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static Directory &_mutable(Directory const &dir)
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{
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return const_cast<Directory &>(dir);
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}
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public:
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/**
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* Constructor
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*
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* \throw File::Open_failed
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*/
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Readonly_file(Directory const &dir, Path const &rel_path)
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: _ep(_mutable(dir)._ep)
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{
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_open(_mutable(dir)._fs, _mutable(dir)._alloc,
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Path(dir._path, "/", rel_path));
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}
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~Readonly_file() { _handle->ds().close(_handle); }
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/**
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* Read number of 'bytes' from file into local memory buffer 'dst'
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*
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* \throw Truncated_during_read
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*/
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size_t read(char *dst, size_t bytes)
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{
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Vfs::file_size out_count = 0;
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while (!_handle->fs().queue_read(_handle, bytes))
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_ep.wait_and_dispatch_one_io_signal();
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Vfs::File_io_service::Read_result result;
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for (;;) {
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result = _handle->fs().complete_read(_handle, dst, bytes,
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out_count);
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if (result != Vfs::File_io_service::READ_QUEUED)
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break;
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_ep.wait_and_dispatch_one_io_signal();
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};
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/*
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* XXX handle READ_ERR_AGAIN, READ_ERR_WOULD_BLOCK, READ_QUEUED
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*/
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if (result != Vfs::File_io_service::READ_OK)
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throw Truncated_during_read();
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return out_count;
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}
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};
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class Genode::File_content
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{
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private:
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Allocator &_alloc;
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size_t const _size;
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char *_buffer = (char *)_alloc.alloc(_size);
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public:
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typedef Directory::Nonexistent_file Nonexistent_file;
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typedef File::Truncated_during_read Truncated_during_read;
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typedef Directory::Path Path;
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struct Limit { size_t value; };
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/**
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* Constructor
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*
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* \throw Nonexistent_file
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* \throw Truncated_during_read number of readable bytes differs
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* from file status information
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*/
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File_content(Allocator &alloc, Directory const &dir, Path const &rel_path,
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Limit limit)
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:
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_alloc(alloc),
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_size(min(dir.file_size(rel_path), (Vfs::file_size)limit.value))
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{
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if (Readonly_file(dir, rel_path).read(_buffer, _size) != _size)
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throw Truncated_during_read();
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}
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~File_content() { _alloc.free(_buffer, _size); }
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/**
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* Call functor 'fn' with content as 'Xml_node' argument
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*
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* If the file does not contain valid XML, 'fn' is called with an
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* '<empty/>' node as argument.
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*/
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template <typename FN>
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void xml(FN const &fn) const
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{
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try { fn(Xml_node(_buffer, _size)); }
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catch (Xml_node::Invalid_syntax) { fn(Xml_node("<empty/>")); }
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}
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/**
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* Call functor 'fn' with each line of the file as argument
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*
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* \param STRING string type used for the line
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*/
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template <typename STRING, typename FN>
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void for_each_line(FN const &fn) const
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{
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char const *src = _buffer;
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char const *curr_line = src;
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size_t curr_line_len = 0;
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for (size_t n = 0; ; n++) {
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char const c = *src++;
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bool const end_of_data = (c == 0 || n == _size);
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bool const end_of_line = (c == '\n');
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if (!end_of_data && !end_of_line) {
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curr_line_len++;
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continue;
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}
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if (!end_of_data || curr_line_len > 0)
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fn(STRING(Cstring(curr_line, curr_line_len)));
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if (end_of_data)
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break;
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curr_line = src;
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curr_line_len = 0;
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}
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}
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};
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#endif /* _INCLUDE__GEMS__VFS_H_ */
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