[英]Using boost iostreams filters (close and non-copyable)
After asking question about crypto++ I tried to implement it using boost iostreams. 在询问有关crypto ++的问题后,我尝试使用boost iostreams实现它。 I produced following code:
我产生了以下代码:
#include <iostream>
#include <cryptopp/sha.h>
#include <algorithm>
#include <boost/array.hpp>
#include <boost/iostreams/concepts.hpp>
#include <boost/iostreams/operations.hpp>
#include <boost/iostreams/filtering_stream.hpp>
#include <boost/iostreams/device/file.hpp>
template<typename hash>
class sha_output_filter : public boost::iostreams::output_filter
{
hash _hash;
char _digest[hash::DIGESTSIZE];
public:
typedef char char_type;
typedef boost::iostreams::output_filter_tag category;
sha_output_filter() {}
//sha_output_filter(const sha_output_filter &) = delete;
sha_output_filter &operator=(const sha_output_filter &) = delete;
template<typename Sink>
bool put (Sink &dest, int c)
{
std::cout << "put" << std::endl;
char _c = c;
_hash.Update ((const byte *)&_c, 1);
boost::iostreams::put (dest, c);
}
template<typename Source>
void close (Source &src)
{
std::cout << "close" << std::endl;
_hash.Final(_digest);
}
boost::array<char, hash::DIGESTSIZE> digest() {
boost::array<char, hash::DIGESTSIZE> tmp;
std::copy(_digest, _digest + hash::DIGESTSIZE, tmp.begin() );
return tmp;
}
};
int main()
{
sha_output_filter<CryptoPP::SHA1> outf;
boost::iostreams::filtering_ostream out;
out.set_auto_close (true);
out.push(outf);
out.push(boost::iostreams::file_sink("my_file.txt"));
std::cout << "write" << std::endl;
out.write("123\n", 4);
out.pop ();
out.pop ();
boost::iostreams::file_sink hash_out("hash.txt");
boost::array<char, CryptoPP::SHA1::DIGESTSIZE> digest = outf.digest();
hash_out.write(digest.begin (), CryptoPP::SHA1::DIGESTSIZE);
}
Problem no. 问题编号 1: It does not work if I make sha_output_filter non-copyable despite documentation stating "if T is a standard stream or stream buffer type, by using the templated overload of push taking a non-const reference."
1:尽管有文档指出“如果T是标准流或流缓冲区类型,通过使用带非常量引用的push模板重载,但我仍使sha_output_filter不可复制, 则此方法不起作用”。 but if I uncomment line:
但是如果我取消注释行:
In file included from /usr/include/boost/iostreams/traits.hpp:31:0,
from /usr/include/boost/iostreams/detail/dispatch.hpp:17,
from /usr/include/boost/iostreams/flush.hpp:17,
from /usr/include/boost/iostreams/close.hpp:18,
from /usr/include/boost/iostreams/operations.hpp:16,
from test.cpp:6:
test.cpp: In function ‘T boost::iostreams::detail::wrap(const T&, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type*) [with T = sha_output_filter<CryptoPP::SHA1>, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type = void]’:
/usr/include/boost/iostreams/stream_buffer.hpp:94:5: instantiated from ‘boost::iostreams::stream_buffer<T, Tr, Alloc, Mode>::stream_buffer(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int]’
/usr/include/boost/iostreams/chain.hpp:257:60: instantiated from ‘void boost::iostreams::detail::chain_base<Self, Ch, Tr, Alloc, Mode>::push_impl(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Self = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, Ch = char, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int]’
/usr/include/boost/iostreams/chain.hpp:216:1: instantiated from ‘void boost::iostreams::detail::chain_base<Self, Ch, Tr, Alloc, Mode>::push(const T&, std::streamsize, std::streamsize, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type*) [with T = sha_output_filter<CryptoPP::SHA1>, Self = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, Ch = char, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type = void]’
/usr/include/boost/iostreams/chain.hpp:496:7: instantiated from ‘void boost::iostreams::detail::chain_client<Chain>::push_impl(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Chain = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, std::streamsize = long int]’
/usr/include/boost/iostreams/chain.hpp:484:1: instantiated from ‘void boost::iostreams::detail::chain_client<Chain>::push(const T&, std::streamsize, std::streamsize, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type*) [with T = sha_output_filter<CryptoPP::SHA1>, Chain = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, std::streamsize = long int, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type = void]’
test.cpp:51:16: instantiated from here
test.cpp:20:3: error: deleted function ‘sha_output_filter<hash>::sha_output_filter(const sha_output_filter<hash>&) [with hash = CryptoPP::SHA1, sha_output_filter<hash> = sha_output_filter<CryptoPP::SHA1>]’
/usr/include/boost/iostreams/detail/wrap_unwrap.hpp:53:14: error: used here
In file included from /usr/include/boost/iostreams/detail/streambuf/indirect_streambuf.hpp:23:0,
from /usr/include/boost/iostreams/stream_buffer.hpp:22,
from /usr/include/boost/iostreams/chain.hpp:35,
from /usr/include/boost/iostreams/filtering_streambuf.hpp:17,
from /usr/include/boost/iostreams/filtering_stream.hpp:22,
from test.cpp:7:
test.cpp: In constructor ‘boost::iostreams::detail::concept_adapter<T>::concept_adapter(const T&) [with T = sha_output_filter<CryptoPP::SHA1>]’:
/usr/include/boost/iostreams/detail/streambuf/indirect_streambuf.hpp:187:5: instantiated from ‘void boost::iostreams::detail::indirect_streambuf<T, Tr, Alloc, Mode>::open(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int]’
/usr/include/boost/iostreams/stream_buffer.hpp:106:13: instantiated from ‘void boost::iostreams::stream_buffer<T, Tr, Alloc, Mode>::open_impl(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int]’
/usr/include/boost/iostreams/stream_buffer.hpp:94:5: instantiated from ‘boost::iostreams::stream_buffer<T, Tr, Alloc, Mode>::stream_buffer(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int]’
/usr/include/boost/iostreams/chain.hpp:257:60: instantiated from ‘void boost::iostreams::detail::chain_base<Self, Ch, Tr, Alloc, Mode>::push_impl(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Self = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, Ch = char, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int]’
/usr/include/boost/iostreams/chain.hpp:216:1: instantiated from ‘void boost::iostreams::detail::chain_base<Self, Ch, Tr, Alloc, Mode>::push(const T&, std::streamsize, std::streamsize, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type*) [with T = sha_output_filter<CryptoPP::SHA1>, Self = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, Ch = char, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type = void]’
/usr/include/boost/iostreams/chain.hpp:496:7: instantiated from ‘void boost::iostreams::detail::chain_client<Chain>::push_impl(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Chain = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, std::streamsize = long int]’
/usr/include/boost/iostreams/chain.hpp:484:1: instantiated from ‘void boost::iostreams::detail::chain_client<Chain>::push(const T&, std::streamsize, std::streamsize, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type*) [with T = sha_output_filter<CryptoPP::SHA1>, Chain = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, std::streamsize = long int, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type = void]’
test.cpp:51:16: instantiated from here
test.cpp:20:3: error: deleted function ‘sha_output_filter<hash>::sha_output_filter(const sha_output_filter<hash>&) [with hash = CryptoPP::SHA1, sha_output_filter<hash> = sha_output_filter<CryptoPP::SHA1>]’
/usr/include/boost/iostreams/detail/adapter/concept_adapter.hpp:67:48: error: used here
test.cpp: In copy constructor ‘boost::iostreams::detail::concept_adapter<sha_output_filter<CryptoPP::SHA1> >::concept_adapter(const boost::iostreams::detail::concept_adapter<sha_output_filter<CryptoPP::SHA1> >&)’:
/usr/include/boost/iostreams/detail/adapter/concept_adapter.hpp:38:23: instantiated from ‘void boost::iostreams::detail::optional<T>::reset(const T&) [with T = boost::iostreams::detail::concept_adapter<sha_output_filter<CryptoPP::SHA1> >]’
/usr/include/boost/iostreams/detail/streambuf/indirect_streambuf.hpp:187:5: instantiated from ‘void boost::iostreams::detail::indirect_streambuf<T, Tr, Alloc, Mode>::open(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int]’
/usr/include/boost/iostreams/stream_buffer.hpp:106:13: instantiated from ‘void boost::iostreams::stream_buffer<T, Tr, Alloc, Mode>::open_impl(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int]’
/usr/include/boost/iostreams/stream_buffer.hpp:94:5: instantiated from ‘boost::iostreams::stream_buffer<T, Tr, Alloc, Mode>::stream_buffer(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int]’
/usr/include/boost/iostreams/chain.hpp:257:60: instantiated from ‘void boost::iostreams::detail::chain_base<Self, Ch, Tr, Alloc, Mode>::push_impl(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Self = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, Ch = char, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int]’
/usr/include/boost/iostreams/chain.hpp:216:1: instantiated from ‘void boost::iostreams::detail::chain_base<Self, Ch, Tr, Alloc, Mode>::push(const T&, std::streamsize, std::streamsize, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type*) [with T = sha_output_filter<CryptoPP::SHA1>, Self = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, Ch = char, Tr = std::char_traits<char>, Alloc = std::allocator<char>, Mode = boost::iostreams::output, std::streamsize = long int, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type = void]’
/usr/include/boost/iostreams/chain.hpp:496:7: instantiated from ‘void boost::iostreams::detail::chain_client<Chain>::push_impl(const T&, std::streamsize, std::streamsize) [with T = sha_output_filter<CryptoPP::SHA1>, Chain = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, std::streamsize = long int]’
/usr/include/boost/iostreams/chain.hpp:484:1: instantiated from ‘void boost::iostreams::detail::chain_client<Chain>::push(const T&, std::streamsize, std::streamsize, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type*) [with T = sha_output_filter<CryptoPP::SHA1>, Chain = boost::iostreams::chain<boost::iostreams::output, char, std::char_traits<char>, std::allocator<char> >, std::streamsize = long int, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type = void]’
test.cpp:51:16: instantiated from here
test.cpp:20:3: error: deleted function ‘sha_output_filter<hash>::sha_output_filter(const sha_output_filter<hash>&) [with hash = CryptoPP::SHA1, sha_output_filter<hash> = sha_output_filter<CryptoPP::SHA1>]’
/usr/include/boost/iostreams/detail/adapter/concept_adapter.hpp:38:23: error: used here
In file included from /usr/include/boost/iostreams/detail/streambuf/direct_streambuf.hpp:26:0,
from /usr/include/boost/iostreams/stream_buffer.hpp:21,
from /usr/include/boost/iostreams/chain.hpp:35,
from /usr/include/boost/iostreams/filtering_streambuf.hpp:17,
from /usr/include/boost/iostreams/filtering_stream.hpp:22,
from test.cpp:7:
/usr/include/boost/iostreams/detail/optional.hpp: In member function ‘void boost::iostreams::detail::optional<T>::reset(const T&) [with T = boost::iostreams::detail::concept_adapter<sha_output_filter<CryptoPP::SHA1> >]’:
/usr/include/boost/iostreams/detail/optional.hpp:100:9: note: synthesized method ‘boost::iostreams::detail::concept_adapter<sha_output_filter<CryptoPP::SHA1> >::concept_adapter(const boost::iostreams::detail::concept_adapter<sha_output_filter<CryptoPP::SHA1> >&)’ first required here
The boost::ref
works however. boost::ref
起作用。
Problem no. 问题编号 2. How to close the stream?
2.如何关闭流? The debug output is:
调试输出为:
write
put
put
put
put
The first problem is that your sha_output_filter
does not meet the requirements for using the non-const overload of push
, because it is not derived from std::istream
, std::ostream
or std::streambuf
, so it is not classified as a standard stream or stream buffer type. 第一个问题是您的
sha_output_filter
不满足使用push
的非常量重载的要求,因为它不是从std::istream
, std::ostream
或std::streambuf
派生的,因此未归类为标准流或流缓冲区类型。
This can be deduced from one of the first messages from the compiler 这可以从编译器的第一条消息中推导出来
test.cpp: In function 'T boost::iostreams::detail::wrap(const T&, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type*) [with T = sha_output_filter<CryptoPP::SHA1>, typename boost::disable_if<boost::iostreams::is_std_io<T> >::type = void]':
test.cpp:在函数'T boost :: iostreams :: detail :: wrap(const T&,类型名称boost :: disable_if <boost :: iostreams :: is_std_io <T>> :: type *)[with T = sha_output_filter < CryptoPP :: SHA1>,类型名称boost :: disable_if <boost :: iostreams :: is_std_io <T>> :: type = void]':
where it indicates that it can successfully resolve the boost::disable_if<...>::type
, so it does not disable this overload. 表示可以成功解析
boost::disable_if<...>::type
,因此它不会禁用此重载。 If you look at the source code, you will probably find a enable_if
test on the non-const overload. 如果您查看源代码,则可能会发现对非const重载的
enable_if
测试。
Regarding the second problem, your filter is not marked as being closable, so the Boost library does not know it can call close
on the filter. 关于第二个问题,您的过滤器未标记为可关闭,因此Boost库不知道它可以在过滤器上调用
close
。
This can be resolved by replacing the typedef for category
with 这可以通过更换的typedef解决
category
与
struct category : boost::iostreams::output_filter_tag, boost::iostreams::closable_tag {};
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