421 lines
17 KiB
C++
421 lines
17 KiB
C++
/*
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Copyright (c) 2015, Arvid Norberg
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the distribution.
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* Neither the name of the author nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "libtorrent/aux_/disable_warnings_push.hpp"
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#include <boost/cstdint.hpp>
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#include <boost/system/error_code.hpp>
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#include <vector>
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#include <string>
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#include "libtorrent/aux_/disable_warnings_pop.hpp"
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#include "libtorrent/assert.hpp"
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#ifndef TORRENT_BDECODE_HPP
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#define TORRENT_BDECODE_HPP
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/*
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This is an efficient bdecoder. It decodes into a flat memory buffer of tokens.
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Each token has an offset into the bencoded buffer where the token came from
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and a next pointer, which is a relative number of tokens to skip forward to
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get to the logical next item in a container.
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strings and ints offset pointers point to the first character of the length
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prefix or the 'i' character. This is to maintain uniformity with other types
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and to allow easily calculating the span of a node by subtracting its offset
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by the offset of the next node.
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example layout:
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{
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"a": { "b": 1, "c": "abcd" },
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"d": 3
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}
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/---------------------------------------------------------------------------------------\
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| /--------------------------------------------\ |
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| | | |
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| /-----\ | /----\ /----\ /----\ /----\ | /----\ /----\ |
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| next | | | | | | | | | | | | | | | | |
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| pointers | v | | v | v | v | v v | v | v v
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+-+-----+----+--+----+--+----+--+----+--+----+--+----+--+-------+----+--+----+--+------+ X
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| dict | str | dict | str | int | str | str | end | str | int | end |
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| | | | | | | | | | | |
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| | | | | | | | | | | |
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+-+-----+-+-----+-+-----+-+-----+-+-----+-+-----+-+-----+-+-----+-+-----+-+-----+-+----+
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| offset| | | | | | | | | |
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| | | | | | | | | | |
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|/------/ | | | | | | | | |
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|| /-----------/ | | | | | | | |
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|| |/------------------/ | | | | | | |
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|| || /-----------------------/ | | | | | |
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|| || | /----------------------------/ | | | | |
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|| || | | /---------------------------------/ | | | |
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|| || | | | /-----------------------------------/ | | |
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|| || | | | |/------------------------------------------/ | |
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|| || | | | || /-----------------------------------------------/ |
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|| || | | | || | /----------------------------------------------------/
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|| || | | | || | |
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vv vv v v v vv v v
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``d1:ad1:bi1e1:c4:abcde1:di3ee``
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*/
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namespace libtorrent {
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TORRENT_EXPORT boost::system::error_category& get_bdecode_category();
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namespace bdecode_errors
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{
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// libtorrent uses boost.system's ``error_code`` class to represent
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// errors. libtorrent has its own error category get_bdecode_category()
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// with the error codes defined by error_code_enum.
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enum error_code_enum
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{
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// Not an error
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no_error = 0,
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// expected string in bencoded string
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expected_digit,
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// expected colon in bencoded string
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expected_colon,
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// unexpected end of file in bencoded string
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unexpected_eof,
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// expected value (list, dict, int or string) in bencoded string
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expected_value,
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// bencoded recursion depth limit exceeded
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depth_exceeded,
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// bencoded item count limit exceeded
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limit_exceeded,
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// integer overflow
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overflow,
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// the number of error codes
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error_code_max
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};
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// hidden
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TORRENT_EXPORT boost::system::error_code make_error_code(error_code_enum e);
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}
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} // namespace libtorrent
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namespace boost { namespace system {
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template<> struct is_error_code_enum<libtorrent::bdecode_errors::error_code_enum>
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{ static const bool value = true; };
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template<> struct is_error_condition_enum<libtorrent::bdecode_errors::error_code_enum>
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{ static const bool value = true; };
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} }
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namespace libtorrent {
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typedef boost::system::error_code error_code;
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TORRENT_EXTRA_EXPORT char const* parse_int(char const* start
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, char const* end, char delimiter, boost::int64_t& val
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, bdecode_errors::error_code_enum& ec);
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namespace detail
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{
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// internal
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struct bdecode_token
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{
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// the node with type 'end' is a logical node, pointing to the end
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// of the bencoded buffer.
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enum type_t
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{ none, dict, list, string, integer, end };
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enum limits_t
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{
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max_offset = (1 << 29) - 1,
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max_next_item = (1 << 29) - 1,
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max_header = (1 << 3) - 1
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};
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bdecode_token(boost::uint32_t off, bdecode_token::type_t t)
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: offset(off)
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, type(t)
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, next_item(0)
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, header(0)
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{
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TORRENT_ASSERT(off <= max_offset);
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TORRENT_ASSERT(t >= 0 && t <= end);
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}
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bdecode_token(boost::uint32_t off, boost::uint32_t next
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, bdecode_token::type_t t, boost::uint8_t header_size = 0)
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: offset(off)
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, type(t)
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, next_item(next)
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, header(type == string ? header_size - 2 : 0)
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{
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TORRENT_ASSERT(type != string || header_size >= 2);
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TORRENT_ASSERT(off <= max_offset);
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TORRENT_ASSERT(next <= max_next_item);
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// the string has 2 implied header bytes, to allow for longer prefixes
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TORRENT_ASSERT(header_size < 8 || (type == string && header_size < 10));
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TORRENT_ASSERT(t >= 0 && t <= end);
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}
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int start_offset() const { TORRENT_ASSERT(type == string); return header + 2; }
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// offset into the bdecoded buffer where this node is
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boost::uint32_t offset:29;
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// one of type_t enums
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boost::uint32_t type:3;
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// if this node is a member of a list, 'next_item' is the number of nodes
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// to jump forward in th node array to get to the next item in the list.
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// if it's a key in a dictionary, it's the number of step forwards to get
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// to its corresponding value. If it's a value in a dictionary, it's the
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// number of steps to the next key, or to the end node.
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// this is the _relative_ offset to the next node
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boost::uint32_t next_item:29;
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// this is the number of bytes to skip forward from the offset to get to the
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// first character of the string, if this is a string. This field is not
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// used for other types. Essentially this is the length of the length prefix
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// and the colon. Since a string always has at least one character of length
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// prefix and always a colon, those 2 characters are implied.
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boost::uint32_t header:3;
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};
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}
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// a ``bdecode_node`` is used to traverse and hold the tree structure defined
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// by bencoded data after it has been parse by bdecode().
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//
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// There are primarily two kinds of bdecode_nodes. The ones that own the tree
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// structure, and defines its lifetime, and nodes that are child nodes in the
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// tree, pointing back into the root's tree.
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//
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// The ``bdecode_node`` passed in to ``bdecode()`` becomes the one owning the
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// tree structure. Make sure not to destruct that object for as long as you
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// use any of its child nodes. Also, keep in mind that the buffer originally
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// parsed also must remain valid while using it. (see switch_underlying_buffer()).
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//
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// Copying an owning node will create a copy of the whole tree, but will still
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// point into the same parsed bencoded buffer as the first one.
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// Sometimes it's important to get a non-owning reference to the root node (
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// to be able to copy it as a reference for instance). For that, use the
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// non_owning() member function.
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//
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// There are 5 different types of nodes, see type_t.
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struct TORRENT_EXPORT bdecode_node
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{
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TORRENT_EXPORT friend int bdecode(char const* start, char const* end, bdecode_node& ret
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, error_code& ec, int* error_pos, int depth_limit
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, int token_limit);
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// creates a default constructed node, it will have the type ``none_t``.
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bdecode_node();
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// For owning nodes, the copy will create a copy of the tree, but the
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// underlying buffer remains the same.
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bdecode_node(bdecode_node const&);
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bdecode_node& operator=(bdecode_node const&);
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// the types of bdecoded nodes
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enum type_t
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{
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// uninitialized or default constructed. This is also used
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// to indicate that a node was not found in some cases.
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none_t,
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// a dictionary node. The ``dict_find_`` functions are valid.
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dict_t,
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// a list node. The ``list_`` functions are valid.
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list_t,
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// a string node, the ``string_`` functions are valid.
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string_t,
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// an integer node. The ``int_`` functions are valid.
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int_t
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};
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// the type of this node. See type_t.
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type_t type() const;
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// returns true if type() != none_t.
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operator bool() const;
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// return a non-owning reference to this node. This is useful to refer to
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// the root node without copying it in assignments.
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bdecode_node non_owning() const;
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// returns the buffer and length of the section in the original bencoded
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// buffer where this node is defined. For a dictionary for instance, this
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// starts with ``d`` and ends with ``e``, and has all the content of the
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// dictionary in between.
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std::pair<char const*, int> data_section() const;
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// functions with the ``list_`` prefix operate on lists. These functions are
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// only valid if ``type()`` == ``list_t``. ``list_at()`` returns the item
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// in the list at index ``i``. ``i`` may not be greater than or equal to the
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// size of the list. ``size()`` returns the size of the list.
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bdecode_node list_at(int i) const;
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std::string list_string_value_at(int i
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, char const* default_val = "");
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boost::int64_t list_int_value_at(int i
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, boost::int64_t default_val = 0);
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int list_size() const;
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// Functions with the ``dict_`` prefix operates on dictionaries. They are
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// only valid if ``type()`` == ``dict_t``. In case a key you're looking up
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// contains a 0 byte, you cannot use the null-terminated string overloads,
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// but have to use ``std::string`` instead. ``dict_find_list`` will return a
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// valid ``bdecode_node`` if the key is found _and_ it is a list. Otherwise
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// it will return a default-constructed bdecode_node.
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//
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// Functions with the ``_value`` suffix return the value of the node
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// directly, rather than the nodes. In case the node is not found, or it has
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// a different type, a default value is returned (which can be specified).
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bdecode_node dict_find(std::string key) const;
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bdecode_node dict_find(char const* key) const;
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std::pair<std::string, bdecode_node> dict_at(int i) const;
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bdecode_node dict_find_dict(std::string key) const;
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bdecode_node dict_find_dict(char const* key) const;
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bdecode_node dict_find_list(char const* key) const;
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bdecode_node dict_find_string(char const* key) const;
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bdecode_node dict_find_int(char const* key) const;
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std::string dict_find_string_value(char const* key
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, char const* default_value = "") const;
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boost::int64_t dict_find_int_value(char const* key
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, boost::int64_t default_val = 0) const;
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int dict_size() const;
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// this function is only valid if ``type()`` == ``int_t``. It returns the
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// value of the integer.
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boost::int64_t int_value() const;
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// these functions are only valid if ``type()`` == ``string_t``. They return
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// the string values. Note that ``string_ptr()`` is *not* null-terminated.
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// ``string_length()`` returns the number of bytes in the string.
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std::string string_value() const;
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char const* string_ptr() const;
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int string_length() const;
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// resets the ``bdecoded_node`` to a default constructed state. If this is
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// an owning node, the tree is freed and all child nodes are invalidated.
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void clear();
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// Swap contents.
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void swap(bdecode_node& n);
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// pre-allocate memory for the specified numbers of tokens. This is
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// useful if you know approximately how many tokens are in the file
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// you are about to parse. Doing so will save realloc operations
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// while parsing. You should only call this on the root node, before
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// passing it in to bdecode().
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void reserve(int tokens);
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// this buffer *MUST* be identical to the one originally parsed. This
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// operation is only defined on owning root nodes, i.e. the one passed in to
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// decode().
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void switch_underlying_buffer(char const* buf);
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private:
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bdecode_node(detail::bdecode_token const* tokens, char const* buf
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, int len, int idx);
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// if this is the root node, that owns all the tokens, they live in this
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// vector. If this is a sub-node, this field is not used, instead the
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// m_root_tokens pointer points to the root node's token.
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std::vector<detail::bdecode_token> m_tokens;
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// this points to the root nodes token vector
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// for the root node, this points to its own m_tokens member
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detail::bdecode_token const* m_root_tokens;
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// this points to the original buffer that was parsed
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char const* m_buffer;
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int m_buffer_size;
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// this is the index into m_root_tokens that this node refers to
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// for the root node, it's 0. -1 means uninitialized.
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int m_token_idx;
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// this is a cache of the last element index looked up. This only applies
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// to lists and dictionaries. If the next lookup is at m_last_index or
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// greater, we can start iterating the tokens at m_last_token.
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mutable int m_last_index;
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mutable int m_last_token;
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// the number of elements in this list or dict (computed on the first
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// call to dict_size() or list_size())
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mutable int m_size;
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};
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// print the bencoded structure in a human-readable format to a string
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// that's returned.
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TORRENT_EXPORT std::string print_entry(bdecode_node const& e
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, bool single_line = false, int indent = 0);
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// This function decodes/parses bdecoded data (for example a .torrent file).
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// The data structure is returned in the ``ret`` argument. the buffer to parse
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// is specified by the ``start`` of the buffer as well as the ``end``, i.e. one
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// byte past the end. If the buffer fails to parse, the function returns a
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// non-zero value and fills in ``ec`` with the error code. The optional
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// argument ``error_pos``, if set to non-null, will be set to the byte offset
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// into the buffer where the parse failure occurred.
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//
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// ``depth_limit`` specifies the max number of nested lists or dictionaries are
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// allowed in the data structure. (This affects the stack usage of the
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// function, be careful not to set it too high).
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//
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// ``token_limit`` is the max number of tokens allowed to be parsed from the
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// buffer. This is simply a sanity check to not have unbounded memory usage.
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//
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// The resulting ``bdecode_node`` is an *owning* node. That means it will
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// be holding the whole parsed tree. When iterating lists and dictionaries,
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// those ``bdecode_node`` objects will simply have references to the root or
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// owning ``bdecode_node``. If the root node is destructed, all other nodes
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// that refer to anything in that tree become invalid.
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//
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// However, the underlying buffer passed in to this function (``start``, ``end``)
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// must also remain valid while the bdecoded tree is used. The parsed tree
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// produced by this function does not copy any data out of the buffer, but
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// simply produces references back into it.
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TORRENT_EXPORT int bdecode(char const* start, char const* end, bdecode_node& ret
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, error_code& ec, int* error_pos = 0, int depth_limit = 100
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, int token_limit = 1000000);
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}
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#endif // TORRENT_BDECODE_HPP
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