我正在尝试使用zlib_decompressor
通过istreambuf_iterator
解压缩数据。我找不到一种内置的方法来使用输入迭代器作为流的输入(如果已存在,请指出一种方式)所以我写了这个来源:
template <class cha_type, class iterator_type>
class IteratorSource {
public:
typedef cha_type char_type;
typedef boost::iostreams::source_tag category;
iterator_type& i;
iterator_type eof;
IteratorSource(iterator_type& it, iterator_type end) : i(it), eof(end) {
}
std::streamsize read(char* s, std::streamsize n) {
for(int j = 0; j < n; j++) {
if(i == eof) {
std::cout << "Reached eof after " << j << " bytes\n";
return -1;
}
char next = *i++;
std::cout << "Reading " << next << "\n";
*s++ = next;
}
return n;
}
};
并像这样使用它:
int main() {
std::vector<char> data_back = {'\x78', '\x9c', '\x73', '\x04', '\x00', '\x00', '\x42', '\x00', '\x42'};
auto start = data_back.begin();
IteratorSource<char, decltype(data_back)::iterator> data(start, data_back.end());
boost::iostreams::filtering_istreambuf def;
def.push(boost::iostreams::zlib_decompressor());
def.push(data);
boost::iostreams::copy(def, std::cout);
return 0;
}
提供此输出:
Reading x
Reading �
Reading s
Reading
Reading
Reading
Reading B
Reading
Reading B
Reached eof after 9 bytes
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::iostreams::zlib_error> >'
what(): zlib error
Aborted (core dumped)
我不确定为什么会产生错误,因为从文件加载工作正常。
答案 0 :(得分:4)
编辑为了回答澄清的问题(在下面的评论中),这是我对原始样本做的一个微不足道的改编,我的盒子上的 JustWorks™:< / p>
#include <boost/iostreams/copy.hpp>
#include <boost/iostreams/filter/zlib.hpp>
#include <boost/iostreams/filtering_streambuf.hpp>
#include <iostream>
#include <sstream>
template <class cha_type, class iterator_type>
struct my_source {
typedef cha_type char_type;
typedef boost::iostreams::source_tag category;
iterator_type& it;
iterator_type end;
my_source(iterator_type& it, iterator_type end = {}) : it(it), end(end)
{ }
std::streamsize read(char* s, std::streamsize n) {
std::streamsize result = 0;
while ((it!=end) && n--) {
++result;
*s++ = *it++;
}
return result;
}
};
int main() {
std::string const rawdata {'x', '\234', '\313', 'H', '\315', '\311', '\311', 'W', '(', '\317', '/', '\312', 'I', '\341', '\002', '\0', '\036', 'r', '\004', 'g' };
std::istringstream iss(rawdata, std::ios::binary);
auto start = std::istreambuf_iterator<char>(iss);
my_source<char, decltype(start)> data(start);
boost::iostreams::filtering_istreambuf def;
def.push(boost::iostreams::zlib_decompressor());
def.push(data);
boost::iostreams::copy(def, std::cout);
}
我认为你可以使用任何流,比如stringstream:
std::istringstream iss("hello world\n");
filtering_streambuf<input> def;
def.push(zlib_compressor());
def.push(iss);
boost::iostreams::copy(def, std::cout);
或解压缩:
std::string const rawdata {'x', '\234', '\313', 'H', '\315', '\311', '\311', 'W', '(', '\317', '/', '\312', 'I', '\341', '\002', '\0', '\036', 'r', '\004', 'g' };
std::istringstream iss(rawdata, std::ios::binary);
filtering_streambuf<input> def;
def.push(zlib_decompressor());
def.push(iss);
boost::iostreams::copy(def, std::cout);
这就像一个魅力。 (抱歉八角逃脱:这就是bash给我的东西
printf "%q\n" "$(echo hello world | zlib-flate -compress)"
而且我很懒,保持这种方式。)
查看完整示例 Live on Coliru
或者 Boost Iostreams接受一个streambuffer,所以你可以等效地
def.push(*iss.rdbuf());