C++ 如何使用boost::iostreams:filtering\u istream解压boost::asio::streambuf中的数据?
我正在尝试解压缩从boost asio套接字接收的zlib压缩数据。(版本1.64.0) 我使用C++ 如何使用boost::iostreams:filtering\u istream解压boost::asio::streambuf中的数据?,c++,boost,boost-asio,zlib,boost-iostreams,C++,Boost,Boost Asio,Zlib,Boost Iostreams,我正在尝试解压缩从boost asio套接字接收的zlib压缩数据。(版本1.64.0) 我使用boost::asio::streambuf作为接收缓冲区,使用boost::iostreams::filtering\u istream解压。 如果我一次发送一个压缩的数据,我的代码就会像我预期的那样工作。但是,如果我发送一个压缩数据,将其分成5字节的块,代码就不会像我预期的那样工作 compressed data: 78 9c f3 48 cd c9 c9 57 28 cf 2f ca 49 01
boost::asio::streambuf
作为接收缓冲区,使用boost::iostreams::filtering\u istream
解压。
如果我一次发送一个压缩的数据,我的代码就会像我预期的那样工作。但是,如果我发送一个压缩数据,将其分成5字节的块,代码就不会像我预期的那样工作
compressed data: 78 9c f3 48 cd c9 c9 57 28 cf 2f ca 49 01 00 18 ab 04 3d
78 9c f3 48 cd c9 c9 57 28 cf 2f ca 49 01 00 18 ab 04 3d
sbuf.size():19
<<< try decompress >>>
`is` has some data.
read_size:11
decompressed data: Hello world
<<< decompress loop out >>>
我创建一个压缩数据,如下所示:
auto str = prepare_compressed_data("Hello world");
// Prepare decompressing istream
boost::asio::streambuf sbuf;
boost::iostreams::filtering_istream is;
is.push(boost::iostreams::zlib_decompressor());
is.push(sbuf);
数据如下:
78 9c f3 48 cd c9 c9 57 28 cf 2f ca 49 01 00 18 ab 04 3d
(Length is 19)
我将过滤流设置为解压缩,如下所示:
auto str = prepare_compressed_data("Hello world");
// Prepare decompressing istream
boost::asio::streambuf sbuf;
boost::iostreams::filtering_istream is;
is.push(boost::iostreams::zlib_decompressor());
is.push(sbuf);
以下是网络发送-接收模拟代码:
// Network (asio socket send-receive) emulation
auto str_it = str.begin();
auto rest = str.size();
while (rest != 0) {
auto copy_size = std::min(rest, send_size); // send_size is 5
// Emulate receive
// In actual code, it is `socket.read_some(mbuf)`
// and its return value is `copy_size`.
auto mbuf = sbuf.prepare(copy_size);
char* p = boost::asio::buffer_cast<char*>(mbuf);
std::copy(str_it, str_it + copy_size, p);
sbuf.commit(copy_size);
hexdump(std::string(boost::asio::buffer_cast<char const*>(sbuf.data()), sbuf.size()));
std::cout << "sbuf.size():" << sbuf.size() << std::endl;
{ // decompress
std::cout << "<<< try decompress >>>" << std::endl;
while (is) {
std::cout << " `is` has some data." << std::endl;
char buf[buf_size + 1] = { '\0' };
is.read(buf, buf_size);
std::size_t read_size = is.gcount();
std::cout << " read_size:" << read_size << std::endl;
std::cout << " decompressed data: " << buf << std::endl;
// It seems that is.read() consumed 5 bytes data in underlying sbuf
// even if is.gcount() returned 0.
}
std::cout << "<<< decompress loop out >>>" << std::endl;
}
rest -= copy_size;
str_it += copy_size;
}
如果我一次复制str
,我会得到我预期的结果
compressed data: 78 9c f3 48 cd c9 c9 57 28 cf 2f ca 49 01 00 18 ab 04 3d
78 9c f3 48 cd c9 c9 57 28 cf 2f ca 49 01 00 18 ab 04 3d
sbuf.size():19
<<< try decompress >>>
`is` has some data.
read_size:11
decompressed data: Hello world
<<< decompress loop out >>>
压缩数据:78 9c f3 48 cd c9 c9 57 28 cf 2f ca 49 01 00 18 ab 04 3d
78 9c f3 48 cd c9 c9 57 28 cf 2f ca 49 01 00 18 ab 04 3d
sbuf.size():19
>
`他有一些数据。
阅读尺寸:11
解压数据:Hello world
>
当您阅读不完整的输入时,过滤流将发出EOF信号,并保持信号状态
解决此问题的最安全方法是暂时复制sbuf数据,并且在成功解压缩时仅consume()
数据:
#include <sstream>
#include <string>
#include <iostream>
#include <iomanip>
#include <algorithm>
#include <boost/iostreams/filtering_stream.hpp>
#include <boost/iostreams/filtering_streambuf.hpp>
#include <boost/iostreams/copy.hpp>
#include <boost/iostreams/filter/zlib.hpp>
#include <boost/asio.hpp>
void hexdump(std::string const& buf) {
for (std::string::const_iterator it = buf.begin(), end = buf.end();
it != end;
++it) {
std::cout
<< std::setw(2)
<< std::hex
<< std::setfill('0')
<< (static_cast<int>(*it) & 0xff)
<< ' ';
}
std::cout << std::dec << std::endl;
}
std::string prepare_compressed_data(std::string const& str) {
std::stringstream sender;
boost::iostreams::filtering_streambuf<boost::iostreams::input> out;
out.push(boost::iostreams::zlib_compressor());
out.push(sender);
sender << str << std::flush;
std::stringstream compressed;
boost::iostreams::copy(out, compressed);
return compressed.str();
}
int main() {
auto str = prepare_compressed_data("Hello world");
std::cout << "compressed data: ";
hexdump(str);
// Test settings
#if 0
// send all at conce
std::size_t const send_size = str.size();
#else
// send 5 byte chunks
std::size_t const send_size = 5;
#endif
std::size_t const buf_size = 256;
// Prepare decompressing istream
boost::asio::streambuf sbuf;
// Network (asio socket send-receive) emulation
auto str_it = str.begin();
auto rest = str.size();
while (rest != 0) {
auto copy_size = std::min(rest, send_size);
// Emulate receive
// In actual code, it is `socket.read_some(mbuf)`
// and its return value is `copy_size`.
auto mbuf = sbuf.prepare(copy_size);
char* p = boost::asio::buffer_cast<char*>(mbuf);
std::copy(str_it, str_it + copy_size, p);
sbuf.commit(copy_size);
hexdump(std::string(boost::asio::buffer_cast<char const*>(sbuf.data()), sbuf.size()));
std::cout << "sbuf.size():" << sbuf.size() << std::endl;
{ // decompress
std::cout << "<<< try decompress >>>" << std::endl;
char buf[buf_size] = {};
std::size_t read_size = 0;
boost::iostreams::filtering_istream is;
is.push(boost::iostreams::zlib_decompressor());
std::stringstream ss(std::string(boost::asio::buffer_cast<char const*>(sbuf.data()), sbuf.size()));
is.push(ss);
while (is.read(buf, buf_size) || (read_size = is.gcount())) {
std::cout << " `is` has some data." << std::endl;
std::cout << " read_size:" << read_size << std::endl;
(std::cout << " decompressed data: ").write(buf, read_size) << std::endl;
// It seems that is.read() consumed 5 bytes data in underlying sbuf
// even if is.gcount() returned 0.
}
std::cout << "<<< decompress loop out >>>" << std::endl;
}
rest -= copy_size;
str_it += copy_size;
}
}
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void hextump(std::string const&buf){
对于(std::string::const_迭代器it=buf.begin(),end=buf.end();
它!=结束;
++(it){
标准::cout
谢谢你的回答!似乎安全的方法是在收到所有压缩数据后解压?我理解正确吗?我直接编写了使用zlib的代码。我知道没有安全的方法使用boost::iostreams来执行等效的进程。对吗?